Aims Net primary productivity (NPP) is a key component of the terrestrial carbon cycle. Model simulation is commonly used to estimate regional and global NPP given difficulties to directly measure NPP at such spatial scales. A number of NPP models have been developed in recent years as research issues related to food security and biotic response to climatic warming have become more compelling. However, large uncertainties still exist because of the complexity of ecosystems and difficulties in determining some key model parameters.
Methods We developed an estimation model of NPP based on geographic information system (GIS) and remote sensing (RS) technology. The vegetation types and their classification accuracy are simultaneously introduced to the computation of some key vegetation parameters, such as the maximum value of normalized difference vegetation index (NDVI) for different vegetation types. This can remove some noise from the remote sensing data and the statistical errors of vegetation classification. It also provides a basis for the sensitivity analysis of NPP on the classification accuracy. The maximum light use efficiency (LUE) for some typical vegetation types in China is simulated using a modified least squares function based on NOAA/AVHRR remote sensing data and field-observed NPP data. The simulated values of LUE are greater than the value used in the CASA model and less than the values simulated with the BIOME-BGC model. The computation of the water restriction factor is driven with ground meteorological data and remote sensing data, and complex soil parameters are avoided. Results are compared with other studies and models.
Important findings The simulated mean NPP in Chinese terrestrial vegetation from 1989-1993 is 3.12 Pg C (1 Pg=10¹⁵ g). The simulated NPP is close to the observed NPP, and the total mean relative error is 4.5% for 690 NPP observation stations distributed in the whole country. This illustrates the utility of the model for the estimation of terrestrial primary production over regional scales.

The biological sciences developed very fast during the 20th century and have become increasingly sophisticated and predictive. Along with this trend, areas of research also have become increasingly specialized and fragmented. However, this fragmentation and specialization risks overlooking the most inherent biological characteristics of living organisms. One can ask if the living organisms on the earth have unified and essential characteristics that can connect the disparate disciplines and levels of biological study from molecular structure of genes to ecosystem dynamics. By exploring this question, a new science, ecological stoichiometry, has been developed over the past two decades. Ecological stoichiometry is a study of the mass balance of multiple chemical elements in living systems; it analyzes the constraints and consequences of these mass balances during ecological interactions. All biological entities on the earth have a specific elemental composition and specific elemental requirements, which influence their interactions with other organisms and their abiotic environment in predictable ways. Ecological stoichiometry has been incorporated successfully into many levels of biology from molecular, cellular, organismal and population to ecosystem and globe. At present, the principles of ecological stoichiometry have been broadly applied to research on population dynamics, trophic dynamics, microbial nutrition, host-pathogen interactions, symbiosis, comparative ecosystem analysis, and consumer-driven nutrient cycling. This paper reviews the concepts, research history, principles, and applications of ecological stoichiometry and points out future research hotspots in this dynamic field of study with an aim to promote this discipline of research in China.

Plant traits link environmental factors, individuals and ecosystem structure and functions as plants respond and adapt to the environment. This review introduces worldwide classification schemes of plant functional traits and summarizes research on the relationships between plant functional traits and environmental factors such as climate (e.g., temperature, precipitation and light), geographical variation (e.g., topography, ecological gradients and altitude), nutrients and disturbance (including fire, grazing, invasion and land use), as well as between plant functional traits and ecosystem functions. We synthesize impacts of global change (e.g., climate change) on plant functional traits of individuals and plant communities. Research on plant functional traits is very fruitful, being applicable to research on global change, paleovegetation and paleoclimate reconstruction, environmental monitoring and assessment and vegetation conservation and restoration. However, further studies at large scale and including multi-environmental factors are needed and methods of measuring traits need to be improved. In the future, study of plant functional traits in China should be accelerated in a clear and systematic way.

Estimating carbon storage in terrestrial ecosystems has been a central focus of research over the past two decades because of its importance to terrestrial carbon cycles and ecosystem processes. As one of the most widespread ecosystem types, China’s grasslands play an important role in global change research. The grasslands in China, which are distributed primarily throughout the temperate regions and on the Tibetan Plateau, were classified into 17 community types. In the present study, a statistical model was established to estimate grassland biomass and its geographical distribution in China based on a grassland inventory data set and remote sensing data (Normalized Difference Vegetation Index) using GIS and RS techniques. We found that there was a significant correlation between aboveground biomass density and the maximum annual NDVI when expressed as a power function (R2=0.71, p<0.001). The aboveground biomass was estimated to be 146.16 TgC (1Tg=1012 g) and belowground biomass was estimated as 898.60 TgC (6.15 times of the above biomass) for a total biomass of 1 044.76 TgC. This value accounts for about 2.1%-3.7% of the world’s grassland biomass. The grassland biomass is distributed primarily in the arid and semiarid regions of Northern China and the Qinghai-Xizang Plateau. The average biomass density of China’s grasslands was 315.24 gC·m-2, smaller than the world average. The aboveground biomass density decreases from southeastern China toward the northwest corresponding with changes in precipitation and temperature. Furthermore, aboveground biomass density reached the lowest levels at 1 350 m elevation and peak levels at 3 750 m above sea level which most likely is related to China’s three-step topographical background. The ratio of total biomass of grassland to forest biomass in China is 1/4, much higher than that of the world, suggesting a greater contribution of grasslands to China’s carbon pool.

Root exudates have specialized roles in nutrient cycling and signal transduction between a root system and soil, as well as in plant response to environmental stresses. They are the key regulators in rhizosphere communication, and can modify the biological and physical interactions between roots and soil organisms. Root exudates play important roles in biogeochemical cycle, regulation of rhizospheric ecological processes, and plant growth and development, and so on. Root exudates also serve roles in the plant-plant, plant-microbe, and microbe-microbe interactions. Plant allelopathy, intercropping system, bioremediation, and biological invasion are all the focal subjects in the field of contemporary agricultural ecology. They all involve the complex biological processes in rhizosphere. There are increasing evidences that various positive and negative plant-plant interactions within or among plant populations, such as allelopathy, consecutive monoculture problem, and interspecific facilitation in intercropping system, are all the results of the integrative effect of plant-microbe interactions mediated by root exudates. Recently, with the development of biotechnology, the methods and technologies relating to soil ecological research have achieved a remarkable progress. In particular, the breakthroughs of meta-omics technologies, including environmental metagenomics, metatranscriptomics, metaproteomics, and metabonomics, have largely enriched our knowledge of the soil biological world and the biodiversity and function diversity belowground. Research on plant-soil-microbe interactions mediated by root exudates has important implications for elucidating the functions of rhizosphere microecology and for providing practical guidelines. The concept and components of root exudates as well as the functions are reviewed in this paper. An overview on the root-bacteria, root-fungi, and root-fauna interactions is presented in detail. Methods to study root exudates and microbial communities are reviewed and the aspects needed to be further studied are also suggested.

Aims Nitrogen (N) and phosphorus (P) are two key elements of life and are major limiting nutrients in many ecosystems across the world. The balance of N and P has become the focal point of global change ecology and biogeochemistry, especially as aggravated by atmospheric nitrogen deposition. Although N:P stoichiometry has proved useful in studies of nutrient limitation, biogeochemical cycles, forest succession and degraded land, little is known about it in lower subtropical forest succession. Therefore, our objective is to better understand nutrient controlling factors of plant-soil interaction and reveal interactions of N and P to provide insight and theoretical fundamentals for forest management.

Methods We measured total N and P of organs of dominant species and different soil layers in three forests in Dinghushan Biosphere Reserve, Southern China: pine forest (PF, early successional stage), pine and broad-leaved mixed forest (MF, middle stage) and monsoon evergreen broad-leaved forest (MEBF, advanced stage).

Important findings Soil N content in the 0-10 cm soil layer increased with succession; values in PF, MF and MEBF were 0.440, 0.843 and 1.023 g·kg^-1, respectively. The largest value of P content in the same layer was in MF (0.337 g·kg^-1); the values in PF and MEBF were 0.190 and 0.283 g·kg^-1, respectively. Plant foliage N and P content decreased with succession; the largest values for roots were in MF, and the values in PF equaled those in MEBF. Soil N:P ratio in the 0-10 cm layer significantly increased with succession; 2.3, 2.5 and 3.6, respectively. The N:P ratio of various plant organs also increased with succession, and the value in foliage was close to that in roots; the foliage N:P ratios were 22.7, 25.3 and 29.6, respectively. We discussed the characteristics of N:P ratios in soil and plants of the lower subtropical forest ecosystem, the law of N:P ratios in soil and plants in successional series, and the limiting effect of P on the lower subtropical forest ecosystem.

Over the past two decades, society has become increasingly aware of problems of forest degradation. The effects of forest degradation transcend individual countries and now impact global processes. Research on the restoration of degraded forests has become a key issue in global ecology. Of particular concern are the effects of human activities on forest productivity and site fertility, especially as the demands for fuel and timber from tropical forests increase. Removal and burning of biomass causes nutrient losses and changes to the soil’s physical and chemical characteristics. The amount of nutrient loss depends on the intensity of the activities, local environmental factors, and the type and successional state of the forest. If nutrient losses cannot be recovered during regrowth, forests often become degraded through time. Thus, it is important that the nutrient dynamics of human-impacted forests are well understood in order to develop plans for restoration of degraded forests and for sustainable forest management. Most of the primary tropical forests in southern China have been degraded by human activities during the past several hundred years. Factors leading to their degradation include: timber harvesting, unsustainable agriculture, overgrazing by domestic animals, and intensive harvesting for fuel. In extreme cases, the land has become completely denuded. Attempts to reverse this process of land degradation have been initiated in this region of southern China. Over the last few decades, large areas have been reforested with a native pine species, Pinus massoniana, to prevent further degradation to the landscape. Cutting of trees is now prohibited, but harvesting of the understory and collection of litter is still allowed to satisfy local fuel needs. Compared with whole-tree harvests, this practice removes less biomass from the forests; however, as the understory and litter are relatively nutrient-rich, this practice may slow or prevent the recovery of soil fertility and productivity of these forest ecosystems. The objective of this study was to determine the effects of harvesting understory plant species and litter on nutrient accumulation dynamics in a Pinus massoniana forest of subtropical China. The results are used to address the following questions: 1) How are nutrients distributed in plants of this pine forest; 2) What quantity of nutrients are removed annually from the ecosystem by the practice; 3) Is this harvesting practice sustainable or not; 4) What alternative management options are available for continued use to meet fuel needs while at the same time improving site fertility, productivity and regeneration processes; and, 5) How do stressed ecosystems respond when the stressors are removed, that is, how would the forest respond if the harvesting practice was stopped. In order to achieve the objectives above, an experiment was established in a MAB reserve of subtropical China in May 1990. The experiment was a paired-plot design with 20 replicates. Each pair consisted of a treatment (continued harvest) and control (no harvest) plot, 10 m×10 m in size and surrounded by a 10 m wide buffer strip. In the treatment plots, local people continued to harvest litter and understory plants according to local practice (about 2－3 times a year) from the beginning of the experiment in May 1990. The harvesting according to local practice occurred during the period of 1990 to 1995 and was stopped after this time. Control plots were protected from any harvesting. Each set of paired plots was similar in soil, slope, aspect, and elevation. In this paper we report only the results of nutrient dynamics and its responses to human impacts over a ten-year period from 1990 to 2000.

Droughts are the world’s costliest natural disasters, causing an estimated $6-$8 billion in global damages annually and affecting more people than any other form of natural disaster. Given the consequences and pervasiveness of droughts, it is important to assess the specialized indices that are used to assess drought severity. The standardized precipitation index (SPI) has several characteristics that are an improvement over previous indices, including its simplicity and temporal flexibility that allow it to examine both short term and long term drought conditions. Computation of the SPI involves fitting a gamma probability density function to a given time series of monthly precipitation totals for a weather station. The resulting parameters are then used to find the probability of a particular precipitation event over a given time scale. This probability is then converted to the standard normal random variable SPI index value. In this article, 1-month SPI are calculated and compared with the Z-index, the most widely used index in China. The results demonstrated that 1-month SPI calculated for 7 observational stations are greatly consistent with Zindex, but that the SPI rarely relates to distributing on precipitation, avoiding some of the irregularities associated with the Z-index. Thus, the SPI is superior to the Z-index in its application. We also investigated drought and flood events from 1951-1995 for Beijing in greater detail. By using the 24-month SPI (SPI24), three well-defined drought and flood events were identified from the data series. In general, the same drought and flood events were observed using the 12-month SPI (SPI12) as the SPI24, although there were some interruptions where the SPI12 values approached zero or became negative for short periods. For 3-month periods (SPI3), the SPI values frequently fell above and below zero. These results highlight the SPI characteristics at different time scales. As the time scale increases from 1 to 24 months, the SPI responds more slowly to short-term precipitation variation, and the cycles of positive (wet conditions) and negative (drought) SPI values become more visible. The possibility of calculating the SPI for different time scales enhances its analysis capacity, since it allows the estimation of different antecedent conditions in the soils. Whereas the shortest scales (1 to 3 months) quantifies superficial soil water, which bears a direct significance for agriculture, the longest accumulation scales (12 to 24 months) indicate the state of subsoil moisture as well as other surface and subsurface water resources. The joint consideration of different SPI scales in the analysis contributed to a satisfactory explanation of risk conditions before each flood event reported. These results indicate that the SPI is an effective index for assessing drought conditions at different time scales and should be adopted for use in China.

Aims The nitrogen and phosphorus characteristics of plants represent plant features and responses to environmental factors. Our objectives are to distinguish leaf and litter C : N : P stoichiometric characteristics, nitrogen and phosphorus resorption of trees, and the relationship between stoichiometric ratio and temperature and precipitation for four typical regions in China.

Methods We studied temperate coniferous, subtropical evergreen broad-leaved, tropical monsoon and tropical plantation forest in the Changbaishan, Dinghushan, Xishuangbanna and Qianyanzhou Ecological Stations, respectively. We analyzed leaf and litter C : N : P, N, P and the relation of N, P nutrition limitation at each station.

Important findings Leaf C : N : P in temperate needle and broad-leaved mixed, subtropical evergreen broad-leaved, tropical rain and subtropical plantation forests were 321 : 13 : 1, 561 : 22 : 1, 442 : 19 : 1 and 728 : 18 : 1, respectively. Litter C : N : P of the four forest types were 552 : 14 : 1, 1 305 : 35 : 1, 723 : 24 : 1, 1 950 : 27 : 1, respectively. The C : N of evergreen coniferous forest is higher than in evergreen broad-leaved and deciduous broad-leaved forests, but C : P has no relationship with forest type. Leaf N : P was highest in evergreen broad-leaved forest and lowest in deciduous broad-leaved forest. Plant N : P has a linear relation with latitude and mean monthly temperature, but neither N or P concentration has such a relationship. Plant at high latitude are easily limited by N, those in low latitude are easily limited by P, but results show that plants limited by N or P don’t have higher N or P resorption. Stoichiometric ratios of leaf and litter are consistent, but environmental factors have different effects on different kinds of plant.

To advance our understanding of the effects of climate change on grassland ecosystems, we used a time series (1982-1999) data set of the Normalized Difference Vegetation Index (NDVI) together with historical climate data to analyze interannual variations in grassland vegetation cover and explore the relationships between NDVI and climatic factors on the grasslands of the Tibetan Plateau. The NDVI increased significantly by a ratio of 0.41% a^-1 and a magnitude of 0.001 0 a^-1 during the growing season (p=0.015). An increase in NDVI during the growing season resulted from both the advanced growing season and accelerated vegetation activity. The largest NDVI increase was in the spring with a ratio of 0.92% a^-1 and a magnitude of 0.001 4 a^-1. The NDVI increase in the summer was a secondary contributor to the NDVI increase during the growing season with a ratio of 0.37% a^-1 and a magnitude of 0.001 0 a^-1. In the spring, the NDVI increased significantly in the alpine grasslands (alpine meadow and alpine steppe) and temperate steppe (p<0.01;p=0.001; p=0.002). During the summer, a significant NDVI increase was found in alpine meadows (p=0.027). However, the NDVI increase in alpine and temperate steppe was not significant (p=0.106; p=0.087). In the autumn, no significant increase was found in the three grasslands (p=0.585; p=0.461; p=0.143). In the spring, the NDVI increase in three grasslands was corresponded to an increase in temperature. In the summer, the NDVI was related to temperature and sensitive to precipitation in the spring in the alpine grasslands (alpine meadow and alpine steppe). However, no significant statistical relationship was found between NDVI and climatic factors in temperate steppe. Significant lagged correlations between precipitation and NDVI were found for alpine grasslands (alpine meadow, alpine steppe).

Aims Our objective is to compare a new photosynthetic light-response model with the non-rectangular hyperbola, rectangular hyperbola, and Prado-Moraes model in fitting data and obtaining the maximum net photosynthetic rate and the light saturation point.

Methods We measured the light-response of photosynthetic rate of winter wheat (Triticum aestivum) under the same chamber CO₂ concentration and different air temperatures in North China Plain using a gas analyzer Li-6400. The measured data were simulated by the new photosynthetic light-response model and the non-rectangular hyperbola, rectangular hyperbola and Prado-Moraes models, respectively.

Important findings The new photosynthetic light-response model shows advantage over the non-rectangular hyperbola, rectangular hyperbola, and Prado-Moraes models in fitting data on the maximum net photosynthetic rate and the light saturation point. The main photosynthetic parameters calculated by the new one were very close to the measured data (R²=0.999 4 and R²=0.998 7). Results showed that the apparent quantum was not an ideal indicator to assess the light use efficiency of plants. We suggest the apparent quantum yield be replaced by the quantum yield at the light compensation point due to the unity of the quantum yield for any C₃plantspecies under certain environmental conditions.

Science magazine has published a paper by Fang et al. (2001, 291: 2320-2322) which, based on the variable BEF (Biomass Expansion Factor) method, discusses forest biomass carbon and its changes in China in the past 50 years, by using direct field measureme

The aridity Index (AI, here defined as the climatic aridity) is an index that describes the dry and wet conditions of a site. Historically, the AI has been often used in long-term studies of geography and ecology. Recently it has became one of the most frequently used climatic factors in studies of global change, especially in studies of climate change, ariditification and desertification. A total of 22 AIs used worldwide were briefly introduced in this paper, and of these eight of the more commonly used AIs were evaluated. We discussed their principles, calculation methods, their applications in ecological and geographical studies, and the advantages and shortcomings of each indice were analyzed based on their applications and practice in China. Our analyses indicated that three AIs, the modified Selianinov AI, the de Martonne AI and the Holdridge potential evapotranspiration ratio (another AI to some extent) have clear applicability and significance for physics and ecology. These AIs are suitable for characterizing the physical environment of China and can be used in future studies of climate change, aridification and desertification in China.

Multi-temporal NOAA/AVHRR NDVI digital images and monthly temperature and precipitation data were obtained for 160 standard observatories across China covering the period 1983 to 1992. The relationships among these were analyzed for trends in temporal and geographic variation with the results that: correlation coefficients declined in a north to south direction across the data and increased from the southeast to the northwest of China. The NDVI changes of the temperate desert, steppe and meadow vegetation regions were strongly influenced by the changes of temperature and precipitation, but the influence of climate was relatively small for some agriculture and forest vegetation types in the southeast of China.

Aims Cropping practices and fertilizer/organic matter application affects the soil microbial growth and activity. In china, only few studies have been conducted on the influence of long-term fertilizer and organic matter with fertilizer application on the soil biological properties. Our objective was to study the changes in soil biological and biochemical characteristics under a long-term (15 years) field experiment involving fertility treatments (inorganic fertilizers and organic matter with fertilizers) and two crop rotation systems.
Methods In 1990, thirteen different treatments were established in the Drab Fluvo-aquic soil in Beijing for the long-term experiment. Six treatments were chosen in this study. Four were in a wheat-maize rotation receiving no fertilizer (CK), mineral fertilizers (NPK), mineral fertilizers plus farmyard manure (NPKM) and mineral fertilizers with maize straw incorporated (NPKS). One was in a wheat-maize/wheat-soybean rotation receiving NPK (NPKF). The other was abandoned arable land (CK0) growing weeds. The amount of chemical fertilizer per year was N 150 kg·hm^-2, P₂O₅ 75 kg·hm^-2, K₂O 45 kg·hm^-2, manure 22.5 Mg·hm^-2 and maize straw 2.25 Mg·hm^-2. Established methods were used to analyze soil enzymes and soil physical and chemical characteristics. Analysis was done using an integrative method combining correlation and component analyses in SPSS.
Important findings The soil organic C (SOC) and total N (STN) content, microbial biomass C (SMB-C) & N (SMB-N), activities of soil invertase, phosphatase and urease, and the ratio of SMB-C/SOC and SMB-N/STN were found higher in long-term (15 years) abandoned arable land than those in cultivated arable land soils. However, the soil metabolic quotient, pH value and bulk density of fallow soil were lower than those in cultivated arable land soils. The soil nutrient concentration, microbial biomass C & N, activities of soil invertase, phosphatase and urease, were higher in treatments with fertilizer application (NPK, NPKM, NPKS and NPKF) compared to no fertilizer application treatment (CK). The above soil parameters were also found higher in wheat-maize/wheat-soybean rotation cropping system compared to continuous wheat-maize cropping system. Among the fertilizer application treatments (NPK, NPKM, NPKS and NPKF), NPKM had relative higher soil nutrient concentration, microbial biomass C & N, and enzyme activities compared to other fertilizer application treatments. However, the soil metabolic quotient, pH value and bulk density of NPKM were lower than them.

Aims Lower subtropical evergreen broadleaved forest in Dinghushan is one of typical vegetations in Southern China. Its vegetation is protected very well. Because of its geographical location, the composition of its flora is transitional between the subtropical and tropical. A 20 hm² permanent plot of 400 m × 500 m was established in 2005 for long-term monitoring of the biodiversity in the forest.
Methods The plot was established following the field protocol of the 50 hm² plot in Barro Colorado Island (BCI) in Panama. All free-standing trees with diameter at breast height (DBH) at least one centimeter were mapped and identified to species.
Important findings There are 71 617 individuals, belonging to 210 species, 119 genera and 56 families. Its floristic composition is transitional between the subtropical and tropical. The vertical structure of the forest is clear. There are five layers from the top of the canopy to the ground floor, three tree layers (upper, middle and low), one shrub layer and one herb layer, respectively. Based on important value, Castanopsis chinensis, Schima superba and Engelhardtia roxburghiana are the three most dominant species in the upper layer. There are many shade-tolerant and intermediate light-demanding species, such as Cryptocarya chinensis, Xanthophyllum hainanense, Machilus chinensis in mid-layer. Species in low layer are rich and complex, which composition varies a lot. The species-area curve indicates that there is high diversity in the forest and the number of species is close to BCI. There is high proportion of rare species represented by <20 individuals which account for 52.38% of the total number of species. Among these rare species 45% of them lead to be rare by species characteristics, 20% by the floristic transitional nature of the plot, while the rest by disturbances.Size distribution of all individuals shows an invert J-shape, which indicates that the community is in a stable and normal growth status. Size distributions of the dominant species are classified into four types based on their size-class frequencies, unimodal in the top layer, inverse J-shape in middle layer, close to inverse J-shape in middle and low layer, and L-shape in low and shrub layer. Dominant species in different layers are aggregated by the spatial pattern analysis and the spatial patterns of these species in different layers vary with size-classes. However, spatial patterns of them also show complementary within the same size classes, especially in 10-40 cm DBH. The individuals with DBH>40 cm are randomly distributed.

The concept of ecosystem services was first used in 1960s in abroad and the terminology of “ecosystem services” appeared in 1981. Three classifications of ecosystem services included function classification, structure classification and description classification, in which function classification has been used widely. The relationship between ecosystem services and biodiversity was examined to understand the mechanism of formation and variation in ecosystem services. At present, many case studies have been conducted to obtain the economic values of ecosystem services at local, river basin, regional and national levels with three kinds of methods: economic method, emergy method and benefit transfer. In China, the concept of ecosystem services was introduced in 1990s and, since then, there have been many studies about ecosystem services which involves the introduction of abroad studies, forming and accumulating process of ecosystem services and case studies.

Because of limitations on the studies of ecosystem services, including the reliability of the evaluation results, confusion of ecological capital and ecosystem services, uncertainty of the quantity of ecosystem services, uncertainty of the monetary values of ecosystem services, and complexity of ecosystem functions and services. A new paradigm of ecosystem services should be set to strictly distinguish the ecosystem services from ecological capital, to evaluate the ecosystem services on the basis of ecological monitoring and ecological models, and to divide the region into different units in evaluation of regional ecosystem services. The researches on ecosystem services should pay more attention in the complex relationships between ecosystem services, structure and processes, the response and feedback of ecosystem services to human activities, the impacts of changes in ecosystem services on human well_being, the impacts of policies and institutions on ecosystem services, and the monetary values of ecosystem services from different kinds of ecosystems.

Background and Aims Artemisia ordosica is an important sand fixation plant in north China, whereas few studies were conducted on its population patterns. Population patterns of this species are therefore studied, and the aims are mainly: 1) how spatial scales are related to population patterns, 2) whether plant sizes effect population patterns, and 3) what roles environments play in the process of pattern formation?
Methods Two plots in the size of 50 m×50 m were established in the Mu Us sandy land, and all the A. ordosica plants were recorded and mapped. After that, the data were analyzed with the method of point pattern analysis.
Key results On the scales less than certain critical points, the population is usually characterized by non-random distribution (being clumped or regular), and their spatial association is considerably strong, but may be positive or negative. By contrast, if the scales enlarge beyond these points, the plants will disperse randomly, and their spatial association will loosen greatly. Small individuals are more likely to follow clumped distribution than those big ones. The spatial association between plants will turn from positive to negative if their size differences are enlarged increasingly. Unlike the A. ordosica plants growing in fixed sandy land, those plants in semi-fixed sandy land are easier to follow clumped distribution and associate with each other positively.
Conclusions Population patterns and spatial association of A. ordosica depend on spatial scales, individual sizes and environments, and so do their intra-specific relationships. If A. ordosica plants are transplanted into shifting sandy land for sand control and vegetation restoration, they ought to be arranged in the form of clumped distribution rather than regular distribution.

Aims Mainly distributed in China, subtropical evergreen broad-leaved forest is one of important vegetation types in the world. Here we report preliminary results of floristic characteristics, community composition, vertical structure, size class structure, and spatial structure of Gutianshan(GTS) forest plot.
Methods We established a 24-hm² (600 m×400 m) forest permanent plot from November, 2004 to September, 2005 in mid-subtropical evergreen broad-leaved forest of Gutianshan Nature Reserve, China. Following the standard census procedure of the Centre for Tropical Forest Science (CTFS), all free-standing trees ≥1 cm in diameter at breast height (DBH) in the forest were mapped, tagged and identified to species. We employed software R 2.6.0 to analyze our data.
Important findings The results of floristic characteristics indicates that the tropical elements are more than temperate elements. At family level, the proportion of the pantropic type is the greatest (28.6%), the number of the tropic elements are more than temperate ones (24/13). At genus level,there are 53 tropic genera and 44 temperate ones. As for community composition, there are 159 species, 103 genera and 49 families, 140 700 individuals in total. The evergreen tree species in community are dominant (i.e. 91 species, total relative dominance is 90.6%, importance value is 85.6%, accounts for 85.9% of the total abundance). GTS forest plot is typical mid-subtropical evergreen broad-leaved forest, which displays characteristics of both temperate deciduous broad-leaved forest and tropical rain forest. On the one hand, community composition has obvious dominant species, which is similar to temperate deciduous broad-leaved forest. There are 3 mostly dominant species, Castanopsis eyrei, Schima superba and Pinus massoniana. Large numbers of rare species (59 rare species, equal to or less than one tree per hm²) in the community account for 37.1% species richness, which is similar to tropical rain forest. Vertical structure is composed of canopy layer (63 species), sub-tree layer (70 species), shrub layer (26 species).The structure of DBH size class of all species in the plot generally appears reverse 'J' shape, which indicates successful community regeneration. Spatial distribution of several dominant species, from small to adult tree or old tree, shifts from closer aggregation to looser aggregation, and shows different habitat preference. Finally, we compare the large plot approach with conventional sampling method.

Chlorophylls function in harvesting light energy, funneling the excitation to reaction center and converting sunlight into chemical energy, and carotenoids are responsible for light harvesting and photoprotection. Both are vital for photosynthesis. We summarized the distribution and function of the main photosynthetic pigments and variation of pigment composition and content in sun and shade plants. Sun plants possess larger xanthophyll cycle pool size (violaxanthin + antheraxanthin + zeaxanthin), but de-epoxidation level is lower than that of shade plants. The ratio of lutein to xanthophyll cycle pool size is positively correlated to plant shade tolerance. Light intensity and spectral quality vary between different shade sources. Generally for plant growth, building shade is better than vegetation shade, and deciduous shade exceeds coniferous shade. Variation in light intensity may activate two cycles in plants, xanthophyll cycle and lutein epoxide cycle, for light harvesting or energy dissipation. Some species may alter chlorophyll content and Chl a/b ratio to acclimate to different light intensity, but this character is not related to their shade tolerance. Temporary shade is not necessarily detrimental. Xanthophyll cycle pool size is not only determined by daily photon receipt, but also by the way photon flux is distributed over the daylight hours, because light and temperature are both essential for optimal photosynthetic metabolism. The best photosynthetic performances of plants were obtained with the reinforcement of blue, red and far red wavelengths and with a red: far red ratio closer to that observed in nature. We reviewed internal and external factors affecting photosynthetic pigment content and composition, and determined that during the acclimation to different light environments, plants altered pigment composition and content mainly through adjusting the ratio of reaction center to light harvesting complex and PSI/PSII. We also discussed current research problems and provided insight into future relevant research.

Aims Little is known about constrained ratios of carbon, nitrogen, and phosphorus (C:N:P) in terrestrial ecosystems. Our objective was to examine the C:N:P stoichiometry and its relationship with N and P resorption in evergreen broad-leaved forests (EBLF), evergreen coniferous forests (CF) and deciduous broad-leaved forests (DF) at the regional scale.

Methods The study was conducted in Tiantong National Forest Park (29°52′ N, 121°39′ E), Zhejiang Province, eastern China. To estimate foliar and litter C:N:P ratios and N and P resorption efficiencies, we quantified the C, N and P concentrations in leaf and litterfall in EBLF, CF and DF. We used type II regression slopes (reduced major axis, RMA) to determine whether C:N:P stoichiometry varied across gradients of forest production and nutrients.

Important findings The C:N:P ratios in EBLF, CF and DF were 758:18:1, 678:14:1 and 338:11:1 in fresh leaves and 777:13:1, 691:14:1 and 567:14:1 in litterfall, respectively. The foliar C:N ratio was highest in CF, intermediate in EBLF and lowest in DF, while the foliar C:P and N:P ratios were highest in EBLF, intermediate in CF and lowest in DF. In contrast, the litterfall C:N and C:P ratios were higher in EBLF than in CF and DF, and there were no significant differences of N:P ratio among forests. The type II regression slope for N vs. P in leaves of overall plants was statistically >1, suggesting an increasing investment of N with increasing of P in fresh leaves. In contrast, the slope for N vs. P in litterfall approximated 1. N resorption in EBLF was significantly higher than in CF and in DF, but the highest P resorption was observed in DF. Although foliar N:P ratios indicated that EBLF was P limited, DF was N limited and CF was both N and P limited, the nutrient resorption efficiency did not respond with relatively high N resorption in EBLF and high P resorption in DF. We concluded that the relative higher resorption of N and P before leaf abscission could be an inherent property of plants, but was not a mechanism thought to have evolved to conserve nutrients in environments with limited N or P supply.

The objectives of this study were to characterize the C:N:P stoichiometry of the “plant-litter-soil” continuum and to better understand nutrient cycling and stability mechanisms in karst forest ecosystems in Southwest China. Three representative forest sites were selected for each of the primary and secondary communities (28 years of natural restoration) in Northwest Guangxi, and measurements were made on carbon (C), nitrogen (N), and phosphorus (P) contents in plants, litter and soils. Compared with other regions, the plants in karst forest ecosystems had relatively lower C content and higher N content, with a lower C:N ratio in consistency with the characteristics of plants. After 28 years of natural recovery, N and P absorption in secondary forests were at a relatively stable state compared with the primary forest communities. The values of N:P ratio varied from a range of 16-19 in the primary forest communities to 17-19 in the secondary forest communities, without apparent difference in the mean vale between the two contrasting community types. Soil organic C, N and P in karst forests occurred primarily in the top 0-10 cm soil layer, at 92.0 mg·g^-1 C, 6.35 mg·g^-1 N, and 1.5 mg·g^-1 P, respectively. In contrast, the nutrient utilization efficiency and nutrient resorption rate were lower in karst forest plants than in other plant types, with karst forest plants exhibiting a relatively rapid nutrient turnover rate. The N resorption rate was lower, and the P resorption higher, in the primary forest communities than in the secondary forest communities, indicating that the higher N deficiency and lower P deficiency of the primary forest communities compared with the secondary forest communities. Determination of the C:N:P stoichiometric characteristics in the plant-litter-soil continuum in this study provides a scientific guidance for restoration of the vulnerable karst ecosystem in Southwest China.

Aims Homeostasis constrains the elemental composition of individual species within narrow bounds no matter the chemical composition of the environment or the resource base. Our objective was to determine the dynamics of leaf stoichiometry during the growth period of plants and the optimum time for stoichiometry study.

Methods We monitored leaf N, P stoichiometry of Scirpus mariqueter, Carex scabrifolia and Phragmites australis, the dominant species in Hangzhou Bay coastal wetlands, at different growth stages from May to October 2007.

Important findings Leaf N, P stoichiometry of the Scirpus, Carex and Phragmites species showed differences: 7.41-17.12, 7.47-13.15 and 6.03-18.09 mg·g^-1 for N, 0.34-2.60, 0.41-1.10 and 0.35-2.04 mg·g^-1 for P, and 7.19-30.63, 11.58-16.81 and 8.62-21.86 for N:P ratios, respectively. The arithmetic means for the three species were (11.69 ± 2.66), (10.17 ± 1.53) and (11.56 ± 3.19) mg·g^-1 for N, (0.93 ± 0.62), (0.74 ± 0.23) and (0.82 ± 0.53) mg·g^-1 for P, and 16.83 ± 8.31, 14.53 ± 3.91 and 16.49 ± 5.51 for N:P, respectively, but there was no significant difference of N, P stoichiometry (p > 0.05). It showed high N, P concentrations at the early stage of growth because of small biomass and then decreased greatly with leaf expansion during the fast growth period, increased as leaf growth became stable and decreased again with leaf senescence. Leaf N:P was low at the early stage of growth and then increased, decreased strongly at the fast growth period, and became stable after leaf maturation.

The plant breeding system has become the most active and promising area among the recent evolutionary studies. In its definition, the plant breeding system represents the sum of all sexual characteristics that could possibly in fluence the genetic c

All viable seeds present on or in the soil or associated litter constitute the soil seed bank. Seed bank input is determined by the seed rain. Seed rain comes from seed dispersion from mother plants and also from secondary dispersion. Seed losses result from germination, animal predation, deep burial, redispersal, natural senescence and death caused by pathogens and some animals. Seeds in the soil display horizontal and vertical dispersion, reflecting initial dispersal onto the soil and subsequent movement. Investigation of the seed and spore bank has become a recognized and indispensable part of plant ecology now and has been an active research area. The soil seed bank is one of the life history stages of plant populations, which is called subpopulation stage. Some soil seed bank classification methods had been provided by scientists, but simply the soil seed bank can be classified into the transient soil seed bank, with seeds that germinate within a year of initial dispersal, and the permanent soil seed bank, with seeds that remain in the soil more than one year. Even given ideal germination conditions such as season, temperature and moisture, some seeds in the soil still remain dormant; these comprise the persistent soil seed bank. Temporal and spatial heterogeneity is the basic characteristic of the soil seed bank. Not only are the floristic composition, size and diversity of the soil seed bank different in different plant communities, but microsites or microhabitats greatly affect the distribution patterns of the soil seed bank. The number of reproductive individuals existing in a dormant state is significantly greater than that of aboveground individuals in most habitats dominated by higher plants. Because of reasons such as germination, predation and decay, soil seed banks have seasonal dynamics. The soil seed bank, seedling bank and adult vegetation can interconnect and interact with each other. The relationship between soil seed banks and their aboveground vegetation is similar or dissimilar because of different plant community types, different succession stages and different sampling time. Germination in the greenhouse and physical separation methods were used to research the soil seed bank. The soil seed bank can partly reflect the history of communities, and plays an important role in the restoration of degraded ecosystems.The main hot topics about soil seed bank research are summed up as following: 1) the research methods about soil seed banks; 2) the classification of soil seed banks; 3) the temporal and spatial distribution patterns of soil seed banks; 4) the relationships between aboveground vegetation and soil seed bank; 5) the dynamics of soil seed banks.

Above- and below-ground are important components of terrestrial ecosystems. Plants and microorganisms are dependent on each other, and they are important in the linkage between above- and below-ground processes. The relationship between plants and soil microorganisms and the fundamental role played by above- and below-ground feedbacks are important in controlling ecosystem processes and properties. Plant species play a fundamental role in nutrient absorption, nutrient accumulation, nutrient distribution and nutrient return. Soil microorganisms are important in controlling plant nutrient availability and soil quality. Our main objective is to summarize the relationships between plants and microbes, such as facilitation and competition. Plants, as producers, provide nutrients for soil microorganisms via leaf litter and root exudation. Soil microorganisms, as decomposers, break down organic matter and provide nutrients to plants. A wide range of soil microbes form intimate symbiotic associations with plants, and this can stimulate plant productivity by delivering limited nutrients to their host plants. However, both plants and microbes compete for nutrients because plant nutrient uptake and microbial immobilization occur simultaneously. We provide an integrated analysis of effects of plant diversity on soil microbial diversity, as well as direct and indirect effects of soil microbes on plant diversity and productivity. Previously, the mechanisms of plants and microorganisms in regulating ecosystem nutrient cycling have been controversial. Litter chemical composition and diversity should be considered important functional traits that explain the mechanisms. It is clear that interactions between plants and microbes play a fundamental role in maintaining the stability of natural ecosystems. This review elucidates the linkage between aboveground and belowground processes, which have been treated separately in the past.

Karst region of Southwest China is ecologically very fragile. It has been suffering from severe rock-desertification and its vegetation has been damaging heavily. The restoration or reconstruction of the vegetation is extremely difficult. In recent years, a lot of pure and application-oriented basic researches have been performed in order to scientifically and technologically support the management of the rock-desertification. In this paper, we summarize habitat characteristics of the karst region and review the progress in ecological researches on plant adaptation, plant population, plant community and ecosystem in the region. In addition, as for current situation in management of the rock-desertification, we propose, particularly from angle of plant ecology, expectations for further researches in the region.

Aims Many mechanisms of forest patterns have been examined in tropical rain forest; however, there are only a handful of similar studies on subtropical broad-leaved evergreen forest. Our objective is to analyze the main mechanisms of distribution pattern of Castanopsis eyrei and Schima superba in GTS (Gutianshan) forest plot.

Methods Based on a stem map of a 24 hm² permanent plot in the middle subtropical broad-leaved evergreen forest at Gutianshan National Reserve, we analyzed the distribution pattern of the dominant species C. eyrei and S. superba in saplings, juvenile trees, adult trees, large trees and old trees using spatial point pattern analysis. We also examined spatial associations among different growth stages.

Important findings Castanopsis eyrei and S. superba had a clustered distribution across a range of scales (0-100 m). Saplings, juvenile trees and adult trees tended to be more clumped than big trees. Old trees tended to be somewhat more clumped than big trees. Our results suggested that the two species have obvious habitat preferences at larger scales. For C. eyrei, saplings were significantly positively associated with juvenile trees at scales ≤ 100 m, as were saplings and adult trees, juvenile trees and adult trees, adult trees and big trees. Generally there was no correlation between big trees and old trees at scales ≤ 10 m, whereas their association tended to be positive at larger scales (10-100 m). Generally there were negative or no correlations between other size classes. For S. superba, the saplings were significantly positively associated with juvenile trees at scales ≤ 100 m, as were saplings and adult trees, juvenile trees and adult trees. Generally there were negative or no correlations between juvenile trees and old trees, adult trees and old trees, big trees and old trees, saplings and big trees, juvenile trees and big trees, adult trees and big trees. Generally there was negative correlation between saplings and old trees at scales ≤ 20 m, whereas their association tended to be positively at larger scales (25-100 m). These results suggested that dominant species facilitated coexistence of other species through emptying space for colonization of other species, which is probably attributed to density dependence or the Janzen-Connell effect. Both processes depended on species in intensity and acting time.

Grazing disturbance is one of nain factors affecting change in plant diversity of grassland communities.The results of this study of nine major grassland communities along the grazing disturbance gradient in the Northeast China Transect showed that the Shannon index was the highest in moderate grazing or heavy grazing stages, changing as follows: Moderate grazing-Heavy grazing > Heavy grazing-Moderate grazing > Light grazing > Over grazing. While species richness had a higher contribution to species diversity, compared with evenness, changes in evenness contributed most towards the rate of change in diversity than did changes in species richness. Life form diversity also manifested some obvious changes along the grazing disturbance gradient. The pattern of plant diversity of the steppe region in the Northeast China Transect was Meadow steppe > Typical steppe > Desert steppe > Alkaline meadow.

Aims It is well documented that nitrogen (N) and phosphorus (P) are the two main growth-limiting nutrients for plants in many natural environments. Plant N:P ratio has proved useful as an indicator of shifts from N (P) to P (N) limitation because it is easily determined and compared. However, little is known about the plant N:P ratio in evergreen broad-leaved forests (EBLF), particularly the pattern along secondary succession. Therefore, our goal was to examine the relationship between the form of nutrient limitation and secondary successional stage by using the N:P ratio of plant leaves (ratio of N to P concentration) as an indicator.
Methods The research was completed in Tiantong National Forest Park (29°52' N, 121°39' E, 200 m elevation), Zhejiang Province, East China. Leaf N and P concentrations of dominant tree species along a secondary succession gradient of EBLF were quantified to provide canopy N:P ratios for different communities. Leaf N and P concentrations of common plant species in a given community were then determined to emphasize the relationships between differences in the N:P ratios among species at each successional stage.
Important finding Shifts in the N:P ratios of species were consistent along the successional series, although the N:P ratios of different species in a given community varied considerably. At the community level, the lowest N:P ratio (7.38) was found in grassland, which was usually considered a primary stage of EBLF succession. Thereafter, the N:P ratio increased to 19.96 in the shrub stage, declined to an average of 14-16 in the mid-stages of succession, including coniferous forest and coniferous-broadleaved mixed forest, and increased at the end stages of succession (e.g. 18.77 in the Schima superba community and 20.13 in the Castanopsis fargesii community). These results suggest that the productivity of vegetation in the Tiantong region is N-limited in the primary stages of succession, N- and P-limited in the mid-succession stages and probably P-limited in the shrub and mature EBLF stages.

Aims Rising soil temperature under the warming process stimulates microbial activity in soils on the Qinghai- Xizang Plateau. Moreover, the eastern edge of Qinghai-Xizang Plateau has been experiencing distinct atmospheric nitrogen deposition with an increasing trend. All of these have led to an increase in the available nutrients in soils. This study was aimed to determine the responses of carbon fixation in the alpine meadow to nitrogen and phosphorus additions on the Qinghai-Xizang Plateau.
Methods The study was conducted in an alpine meadow ecosystem at the Haibei National Field Research Station of Alpine Grassland Ecosystem, Northwest Institute of Plateau Biology, Chinese Academy of Sciences. Four treatments were set up in 2009, including control, nitrogen addition only (N), phosphorus addition only (P), and combined nitrogen and phosphorus additions (NP). Nutrients were added in June or July each year. The aboveground biomass of functional groups and the above- and belowground biomass of plant communities were measured by harvesting in 2012.
Important findings (1) N and P additions increased the aboveground biomass of grass, and the proportion of grass biomass in the community, but decreased the proportion of forb biomass in the community. Only P addition decreased the aboveground biomass of sedge, and the proportion of sedge biomass in the community. (2) N and P additions increased the aboveground biomass by 24% and 52%, respectively, compared with the control. (3) N addition had no effect on the belowground biomass, whereas P addition slightly increased the belowground biomass. (4) N addition had no effect on the total biomass, whereas P addition significantly increased the total biomass. Therefore, N and P additions could relieve the nutrient limitation and stimulate plant growth. Furthermore, the results suggest that the Qinghai-Xizang Plateau could be more limited by P than N on plant growth.

Aims Plant or biomass stoichiometry can be used to distinguish biological entities (genes, cells, organisms, etc.) based on element composition. Our objective was to determine the stoichiometry characteristics and examine nutrient limitation in evergreen broad-leaved forest, coniferous and broad-leaved mixed forest and coniferous forest.

Methods We determined C, N, P stoichiometry of leaves of 19 dominant trees of 16 taxa in three forest types at the Pearl River Delta Forest Ecosystem Research Station, Guangdong Province, South China.

Important findings Leaf stoichiometry showed large variations: C ranged from 434 to 537 mg·g^-1, N from 6.8 to 23.0 mg·g^-1, P from 0.56 to 2.10 mg·g^-1, C:N from 21.22 to 70.74, C:P from 227.14 to 844.64 and N:P from 5.26 to 20.91. Leaf N, P, C:N and C:P were linearly correlated (p < 0.01). Leaf C, C:P and N:P (weighted average ± standard deviation: (517.85 ± 35.96), (727.47 ± 231.52) and (15.71 ± 3.76) mg·g^-1, respectively) were the highest in coniferous forest, followed by mixed forest (509.47 ± 19.38, 553.01 ± 152.32 and 10.93 ± 1.89, respectively) and evergreen broad-leaved forest (481.59 ± 18.35, 412.19 ± 200.91 and 9.46 ± 4.28, respectively), and a reverse sequence was detected for leaf P content. The sequence for N content was coniferous forest ((12.20 ± 5.65) mg·g^-1) > evergreen broad-leaved forest ((11.50 ± 4.24) mg·g^-1) > mixed forest ((10.51 ± 5.22) mg·g^-1) and for C:N was mixed forest (51.35 ± 13.65) > coniferous forest (47.40 ± 15.85) > evergreen broad-leaved forest (45.59 ± 14.70), and higher nutrient use efficiency was discovered in three forest types. Several evergreen broad-leaved trees and evergreen broad-leaved forest had shortages of N.

Aims Much research is being done on plant nutrients and stoichiometry. Our purpose was to reveal the effects of grazing on plant nutrients and stoichiometry in a typical steppe of Inner Mongolia of China.

Methods We studied nutrient content of C, N and P and their ratio in soil and leaves of dominant plants in three adjacent sites: fenced since 1983 and 1996 and unfenced. We employed the stoichiometric approach and assessed the effects of grazing on spatio-temporal patterns of nutrient cycling between plants and soil in restoration succession of degenerate steppes.

Important findings Both total soil nutrient content and the ratio of the soil total nitrogen and soil total phosphorus (STN:STP) were lower in overgrazed plant communities compared to fenced plant communities at different levels of restoration. Conversely, the ratio of soil organic carbon and STN (SOC:STN) was higher in overgrazed plant communities. The total organic carbon content (TOC) of most plants was higher in fenced communities and lower in grazed communities and was positively correlated with time since community restoration began. However, the content of total nitrogen (TN) and total phosphorus (TP) in plants was higher in fenced communities than that in grazed communities. Both TN and TP correlated negatively with time since restoration began and positively with the degree of degradation due to overgrazing. TP had a larger range in values compared to TN. The stoichiometry ratios of nitrogen and phosphorus (N:P) and carbon and nitrogen (C:N) in leaves were the lowest in grazed communities and correlated negatively with the degree of degradation. These communities had less total N than total P; however, this pattern was reversed in fenced communities, where sometimes both N and P were limiting. We propose that stoichiometry ratios in dominant plant species can serve as indicators of direction of plant succession in this typical steppe.

Human activities have greatly changed the pathway and rate of nitrogen transferred from atmosphere to terrestrial ecosystems worldwide. Anthropogenic nitrogen enrichment, as a result of chronic nitrogen deposition, has caused a wide range of impacts on ecosystem structures and functions. In this paper, we summarize the main effects of anthropogenic nitrogen addition on terrestrial ecosystems as follows:

1) Increased nitrogen input may have influences on plant production and ecosystem carbon storage, and the direction and magnitude of responses are determined by initial nitrogen status of ecosystems (N-limited or N-saturated) and local properties of vegetation and soil;

2) Chronic nitrogen addition can also alter soil nitrogen cycling, decrease the capability of soil to retain N, even lead to soil acidification, depletion of base cation, and affect decomposition of SOC;

3) Both high rate of nitrogen deposition and chronic low nitrogen addition may accelerate losses of N-contained gas, but the magnitude of influences depends on initial status of ecosystem (N-limited or P-limited);

4) N enrichment will affect species richness in terrestrial ecosystems, plant communities' structures and dynamics. It may also contribute to forest expansion into grasslands, alter species composition and diversity of mycorrhizal fungi;

5) Continuous N input and the resulting changes in plant composition and physiological feature may have effects on consumption rate and population dynamics of herbivorous insects, and eventually change ecosystem trophic structure through food chain;

6) Since the influences of N addition, increased concentration of CO₂ and O₃ on ecosystem properties and processes are interdependent, it is difficult to distinguish each effect.

We also summarized the current status of researches on N deposition in China, and proposed the potential research activities and recommendations.

Land use/cover change (LUCC) is one of the most concerned environmental problems by scientists, land managers and policy makers. LUCC can affect energy flow, biogeochemical and hydrological cycling in terrestrial ecosystems through altering land surface and species composition. Ecosystem carbon cycling responds differently to various LUCC types, showing a pattern of CO₂ release into the atmosphere when LUCC from a high-biomass forest to low-biomass grassland, cropland or urban area. Previous reports indicated that global terrestrial ecosystem released 2.21 Pg C (1 Pg C=10¹⁵ g C) per year induced by LUCC during the 1990s, which explains about 25% of the global C emission per year in the same period; and in the last two centuries, the released C from LUCC accounts for 50% of the C emission from fossil fuel combustion. The LUCC patterns are totally diversified for regions around the world, which cause obviously different C fluxes among them. The reports showed that LUCC in the tropics is a C source, while it is a C sink in the middle and high latitude regions in the northern hemisphere, which possibly explain a large part of the “missing carbon sink" in the terrestrial ecosystems. Currently, modeling is the most popular way to simulate LUCC-induced changes in ecosystem C cycling. The quantitative relationship between LUCC patterns and their related processes and ecosystem carbon cycling remains uncertain. This uncertainty causes great discrepancies in the estimation of terrestrial ecosystem CO₂ fluxes from land use/cover changes. In the near future, except for carrying on long-term experiments to determine these quantitative relationships, model development by integrating LUCC with vegetation dynamic model and ecosystem process model will be essential for making an accurate estimation of C fluxes induced by LUCC. Sound land management can greatly increase C storage in the terrestrial ecosystems during LUCC processes. However, the quantification of land management effects is not well-established yet and land management is thus not included in most simulation models of LUCC impacts, which needs more researches in the future.

The concept of leaf economics spectrum (LES) has attracted much attention and debate since its emergence. It for the first time provides quantitative analysis of plant functional traits and their relationships on the global scale, hence quantifying and generalizing the context and variations of the trade-off strategies. This is of great theoretical value, and provides a useful research method and scientific ideas for subsequent study on plant traits and their functions. In this paper, we try to comprehensively review the meaning, contents, relevant verifications and objections about LES, and to explore its underlying mechanisms. In addition, we emphasize the multi-scale and multidimensional extensions, integration and potential applications of LES. Currently there are still several shortcomings about LES research in China, and we outlook the development of LES theory domestically and abroad. It may be of significance for ecological researchers to establish and exploit jointly a global database on plant traits.

Aims Our objective was to explore seasonal variations of leaf C:N:P stoichiometry in plants with the same growth form.
Methods We chose six shrubs in the desert of the Alxa Plateau in north-central China (Zygophyllum xanthoxylum, Nitraria tangutorum, Reaumuria soongorica, Ceratoides lateens, Oxytropis aciphylla and Ammopiptanthus mongolicus) and observed their phenological stages from May to October 2010. Leaf samples were collected during this period, and leaf C, N and P contents and C:N:P stoichiometry were monitored.
Important findings Seasonal dynamics of leaf C, N and P contents and C:N, C:P and N:P mass ratio in the six shrubs were species-specifics, and the variation of leaf C, N and P and C:N, C:P and N:P mass ratios in different species were also dramatically different. Based on variation analysis among different seasons within species, there were less seasonal dynamics in C and N contents and C:N mass ratio than the other three parameters including P contents and C:P and N:P mass ratios. The range of values of coefficient of variation (CV) for C and N contents and N:P mass ratio was 0.60%-10.20%, 6.09%-20.50% and 5.87%-18.78%, respectively. For the other three parameters, the range of CV values for P content was 16.43%-43.43%, and C:P and N:P mass ratios were 8.48%-31.95% and 11.86%-40.73%, respectively. With the comprehensive analysis based on the total variation (resulting from two factors: season and species) for each parameter in these six shrubs, the rank of CV for each parameter was P (28.85%) > C:P (25.02%) > N:P (22.18%) > N (14.22%) > C:N (12.48%) > C (4.62%). Factorial analysis of variation for each parameter, with sampling date (season) and species as independent variables, showed that leaf C and N contents and leaf C:N, C:P and N:P mass ratios were mainly determined by plant species. For leaf P contents, it was the sampling date (season).

Aims The Yangtze River Estuary (YRE) faces eutrophication caused by discharge of industrial and agricultural sewage. This leads to frequent harmful algae blooms involving the rapid proliferation of specific toxic species. The aims of our study are to: 1) apply scientific methods and field experiments to clarify the distributional relationship between phytoplankton species and the environment, and 2) provide data on species and environment informative for further research on estuary ecosystem protection.
Methods An interdisciplinary survey of hydrological, chemical and biological resources was conducted in the YRE on August 28 - September 6, 2004. Phytoplankton cell counts and species identification were performed with an inverted microscope at ×100-×400 magnification after sedimentation for 24 h in 25 ml Utermøhl chambers. Temperature, salinity, pH and dissolved oxygen were measured by a pre-calibrated YSI 6000. Other abiotic environmental data were obtained based on protocols of marine investigations. Canonical correspondence analysis (CCA) was applied to explore the relationship between phytoplankton species and environmental parameters using CANOCO4.0.
Important findings Turbidity and nutrient gradient along the Yangtze River runoff were the most important factors influencing the distribution of phytoplankton species. Transparency, nitrate and silicate were major factors affecting the phytoplankton community structure. The dominant phytoplankton species Proboscia alata f. gracillima preferred low nitrate concentration and clear offshore areas, while Skeletonema costatum preferred high nitrate and more turbid waters. CCA can be a useful tool to understand the spatial distribution of phytoplankton species in marine ecosystems.