Aims Litterfall plays an important role in linking aboveground and belowground processes in forest ecosystems. Nutrients absorbed by plants can be released to the soil and re-utilized by plants via litter decomposition. Although litterfall composition and dynamics have been widely studied in the past two decades, the relationship among litterfall, nutrient cycling and vegetation types is poorly understood. Therefore, we studied litterfall in evergreen broad-leaved forests (EBLF) to enrich our knowledge of the relationship.
Methods The research was conducted in Tiantong National Forest Park (29°52'N, 121°39'E, 200 m a.s.l), Zhejiang, East China. We chose secondary and young EBLF (Schima superba community), coniferous and evergreen broad-leaved mixed forest (Pinus massoniana+Schima superba community), coniferous forest (Pinus massoniana community) and shrubland (Lithocarpus glaber + Loropetalum chinense community) to represent forests at different degradation stages and mature EBLF (Castanopsis fargesii community) to represent reference climax forest. Productivity, composition, nutrient concentration and total nutrient amount of the litterfall were measured each month from November 2003 to October 2004. Litterfall traits were correlated with soil total N, total P, total inorganic N, N mineralization and nitrification rates.
Important findings Degradation of EBLF significantly reduced litterfall productivity from 13.03 Mg·hm^-2 in mature EBLF to 6.38 Mg·hm^-2 in shrubland, and significantly reduced N concentration in litterfall. In contrast, P concentration showed no consistent pattern. Total N and total P amounts returned via litterfall decreased significantly with degradation. Soil total N was positively correlated with annual litterfall productivity but not litter N concentration. Soil total P was positively correlated with both annual litterfall productivity and litter P concentration. Soil inorganic N was not correlated with either productivity or litter nutrient concentration. Soil N nitrification rate was positively correlated with annual litterfall productivity and total amounts of nutrients returned, but was not correlated with litter N concentration. Soil N was not correlated with any litterfall traits. These results suggested that, during degradation of EBLF, shifting of plant functional types and simplifying of community structure reduced the quality and quantity of litterfall to a low level and consequently reduced soil nutrient pools.

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 Forest is an important pool of carbon in terrestrial ecosystems. Woody tissues contribute much biomass, and their respirations influence carbon fixation. Stem respiration is an important component of the carbon budget of forest stands. Stem respiration has been studied in temperate and boreal zones, but seldom has been reported for tropical rain forests. Our objective was to investigate the characteristics of stem respiration and the response of stem respiration to temperature in 11 common trees in Xishuangbanna tropical seasonal rain forest.
Methods We made in situ chamber measurements of stem respiration using an Li-820 infra-red CO₂ gas analyzer (IRGA) from March 2005 to February 2006. Our custom-built polyvinyl chloride (PVC) chamber sealed to the stem by thin neoprene gaskets. Stem respiration rates were measured on south and north sections at 1.3 m height, and stem temperatures were recorded at 1 cm depth.
Important findings Stem respiration rates of all species had similar seasonal patterns and were higher in the wet season and lower in the dry season. There were significant differences in stem respiration rates among species, ranging from 0.823 to 2.727 μmol·m^-2·s^-1. Stem respiration rates on the south and north sections were similar for the same species. Significant exponential correlations were observed between stem respiration rates and stem temperatures (0.55<R²<0.92). Q₁₀ values for stem respiration among species ranged from 1.90 to 3.03, somewhat higher than the range (1.6-2.38) reported in previous studies.

Aims Soil respiration may have distinct dynamic patterns at different temporal scales since it is affected by diverse abiotic and biotic factors. Seasonal variation in soil respiration is largely controlled by abiotic factors such as temperature and soil moisture, whereas the regulation of diurnal variation is likely physiological rhythms of plants. Our objectives were to compare seasonal and diurnal patterns of soil respiration and to evaluate relationships between soil respiration and temperature at annual and diurnal scales.
Methods We examined seasonal variations of soil respiration using infrared gas analyzers at monthly or bimonthly intervals from April 2004 to March 2005, and diurnal variations in July, September and November 2004 as well as in January, March and May 2005 in a montane evergreen broad-leaved forest in Ailao Mountains, China. Soil temperature, air temperature, soil water content and air humidity were measured at the same time. We evaluated Q₁₀ values of soil respiration and correlations between soil respiration and soil temperature.
Important findings Soil respiration fluctuated with distinct seasonal and diurnal patterns. Soil respiration was higher in the wet season (May through October) than in the dry season (November through April). Diurnal patterns of soil respiration varied among seasons. The mean rate of soil respiration was higher in nighttime than in daytime in July, September, January and March, but lower in November and May. On the whole-year basis, soil respiration correlated strongly with soil temperature and soil water content. However, on a diurnal scale, these regressions were not significant. Q₁₀ values were 4.48, 7.17 and 2.34 for the whole year, dry season and wet season, and their corresponding soil temperature ranges were 5.9-16.6, 5.9-11.0 and 10.3-16.6 ℃, respectively. Our results demonstrate that biotic and abiotic factors have distinct impacts on soil respiration at different temporal scales in the forest. Estimation on daily and annual carbon fluxes based on instantaneous measurements of soil respiration, rather than 24-hour measurements, may cause severe deviation from actual values because of the lack of diurnal correlation between soil respiration and temperature.

Aims Parashorea chinensis, an endangered plant listed as the first class protected in China, now survives in local fragmented forests in Mengla, Hekou in Yunnan and Bama, Tianyang, Longzhou, Napo in Guangxi. We developed regression models for individual growth, age structure and biomass and analyzed population density, age structure, biomass dynamics and survivorship curves for local populations and the entire population in Mengla, Xishuangbanna, Yunnan Province, SW China. Our objective was to understand the population dynamics to aid protection of this endangered plant.
Methods We established different numbers and sizes of plots (50 m × 20 m or 100 m × 20 m ) in five local patches according to patch size, and each plot was divided into 10 m × 10 m subplots to measure the height, diameter at breast height (DBH) or basal diameter and crown of each individual >0.5 m height. We also measured height, basal diameter and crown of each individual <0.5 m height in 2 m × 2 m quadrats in each subplot.
Important findings There were large differences in population density and age structure as well as mortality rate for different age stages of local populations in different patches. The local population density of the patch in which some trees were cut was 3-4 times as much as the patch which was protected and 16 -18 times as much as the patch which was planted with Amomum villosum. Moreover, the local population of the smallest patch had no mature individuals and lacked individuals in some age stages. Although the biomass of local populations showed logistic increase with stand age, maximum biomass and biomass dynamics with time were different for local populations. The survivorship curve of the entire population was approximately a straight line, indicating that the age structure of entire population was stable and increasing. The mortality of 1-60 year-old individuals declined, mortality of 60-150 year-old individuals increased with age, and peak mortality occurred after 180 years. The biomass of the entire population was consistent with logistic growth before 180 years and was at a maximum at about 180 years. However, some patches had been so badly disturbed that the local populations were on the edge of extinction. Effective steps must be taken to protect this endangered plant population.

Aims Shorea wantianshuea is an endangered tree species of Dipterocarpaceae in Xishuangbanna seasonal rain forest, and is listed in the Plant Red Book under Grade Ⅰ in China. This species regenerates exclusively from seeds. Our objective was to determine the fate of seedlings (including their growth and survival) following a mast fruiting event. Results will be useful in restoring this species and degraded natural forests dominated by it.
Methods In early December 2004, after mast fruiting of S. wantianshuea, we established three parallel 20 m×100 m transects spaced 50 m apart within an area of 100 m×200 m spanning from valley bottom to ridge top. Each transect was stratified into five contiguous plots of 20 m and near the center of each plot two 3 m×3 m quadrats were established. We labeled all newly established S. wantianshuea seedlings in each quadrat, recorded seedling height, basal stem diameter and number of leaves every 2-3 months over a 10-month period and calculated death rate, herbivory rate and survival rate of the seedlings. At the end of the survey, we destructively sampled seedlings and determined leaf areas, total dry weight, root-shoot ratio and specific leaf area.
Important findings Many S. wantianshuea seedlings established after the mast-fruiting event did not recruit into its natural population because of high mortality rate and herbivory rate caused by seasonal drought stress, small mammals and other predators. The density of seedlings was as high as 2.76 plants·m^-2 in December 2004 (first census), but was less than 0.26 plants·m^-2 in September 2005 when the study ended. Seedling mortality rate was high during the dry season, particularly after the first two months. The final seedling mortality rate on ridge-top and lower-ridge sites, 55% and 54%, respectively, were higher than those on other sites, with a gradually increase from valley bottom to ridge top. Herbivory rate in the first census was low and in 8 of 15 sites no seedlings were gnawed or pulled. At the end of the study, mean seedling height was 17.9, 19.7, 18.4, 13.0 and 12.1 cm in valley-bottom, lower-slope, medium-slope, lower-ridge and ridge-top sites, respectively; however, no significant differences were observed in seedling height and other growth parameters.

Aims Rapidly growing population and environmental issues have been key problems for the living and sustainable development of humans. In order to provide policy-makers with a theoretical reference, it is urgent to know how terrestrial ecosystem productivity and its carrying capacity in Northeast China will respond to future climatic change. My objective was to simulate net primary productivity (NPP) of terrestrial ecosystems in Northeast China and their carrying capacities, as well as their responses to climatic change.
Methods Values of NPP of the different terrestrial ecosystems were simulated by a natural vegetation NPP model (Zhou & Zhang, 1995) and an agricultural NPP model (Zheng et al., 1997), in terms of land use (forest, agriculture, grassland and wetland) data with a spatial resolution of 10 km×10 km and daily meteorological data from 1980 to 2002 as well as the projected climatic scenarios for 2020, 2050, 2070 and 2100. Ecosystem carrying capacities were given by the carrying capacity model (Cao, 1993) and NPP of agricultural, grassland and wetland ecosystems.
Important findings Mean annual temperature increased, and annual precipitation decreased in Northeast China from 1980 to 2002. Total mean annual terrestrial ecosystem productivity during these 23 years was 3.52×10 ¹¹ kg DM·a^-1. Total mean annual terrestrial ecosystem productivities for forest, agriculture, grassland and wetland ecosystems were 1.53×10¹¹, 4.55×10¹⁰, 1.07×10¹¹ and 4.63×10¹⁰ kg DM·a^-1, respectively. Mean annual terrestrial ecosystem productivities for forest, agriculture, grassland and wetland ecosystems were 5.73×10³, 1.84×10³, 5.64×10³ and 5.55×10³ kg DM·hm^-2·a^-1. Total mean annual carrying capacities from 1980 to 2002 were 2.61×10⁸, 2.15×10⁸ and 1.77×10⁸ for well-off, comparatively well-off and surplus consumption levels, respectively. When 350×10⁸ kg commercial grain export from Northeast China was considered, total mean annual carrying capacities from 1980 to 2002 were 1.70×10⁸, 1.40×10⁸ and 1.15×10⁸ for the above three consumption levels, respectively. The population of Northeast China is about 1.07×10⁸ at present. It implied that the population in Northeast China should be controlled in the future, in order to ensure the surplus consumption level and 350×10⁸ kg commercial grain export. Simulated total mean annual carrying capacities of Northeast China in 2020, 2050, 2070 and 2100 were 2.73×10⁸, 2.25×10⁸ and 1.85×10⁸;2.88×10⁸, 2.38×10⁸ and 1.95×10⁸; 3.03×10⁸, 2.49×10⁸ and 2.05×10⁸; and 3.09×10⁸, 2.55×10⁸ and 2.09×10⁸ for the three consumption levels, respectively, in terms of the climatic scenarios for the future. This study provides fundamental information for land resources and social sustainable development.

Aims Our study was conducted in the Nokrek Biosphere Reserve (NBR) in the Garo hills districts of Meghalaya, Northeast India. Our aim was to assess the effects of human activities on plant diversity, population structure and regeneration.
Methods We selected a representative 1.2 hm² stand in both the core and buffer zones of NBR. Structure and composition were determined by randomly sampling square quadrats, population structure was assessed by determining age structure, and regeneration was assessed by measuring densities of seedling, sapling and adult trees.
Important findings More woody species were recorded from the core zone than the buffer zone (87 vs. 81 species), and there were a large number of tropical, temperate, and Sino-Himalayan, Burma-Malaysian and Malayan elements, primitive families and primitive genera. The trees were distributed in three distinct strata, canopy, subcanopy and sapling. Subcanopy and sapling layers had the highest species richness (81%-88%). Lauraceae and Euphorbiaceae were the dominant families in terms of the number of species, and a large number of families were represented by single species. Most woody species (57%-79%) were contagiously distributed and had low frequency (<20%). Although stand density was high in the buffer zone, its basal area was low compared to the stand in the core zone. Low similarity and high β-diversity indicate marked differences in species composition of the stands. Shannon diversity index was high in both the stands, while Simpson dominance index was low. The diameter-class distribution for dominant species revealed that the most had a large number of young individuals in their populations. Preponderance of tree seedlings, followed by a steep decline in population density of saplings and adult trees, indicated that the seedling to sapling stage was the most critical in the life cycle of the tree populations. Most species (42%-48%) had no regeneration, 25%-35% had good/fair regeneration, and the rest had poor regeneration or reoccurred as immigrants.

Aims Our objective is to predict the distribution of coniferous species and determine species' sensitivity to environmental factors in the Small Xing'an Mountains, China. This information is important for forest regeneration and biodiversity conservation and is useful to policy makers for forest management at different scales.
Methods Slope, aspect, compound topographic index, elevation, topographic position index and average annual temperature and precipitation were selected for use in Logistic regression to predict the occurrence of Korean pine (Pinus koraiensis), larch (Larix gmelinii), fir (Abies nephrolepis), spruces (Picea koraiensis and P. jezoensis) and Mongol scotch pine's (Pinus sylvestris var. mongolica). Relative operating characteristic (ROC) was used to evaluate the Logistic models. Because Logistic regression is difficult to explain, we used the correlation coefficient between species distribution and environmental factors to explore the sensitivity of species to environmental factors.
Important findings The fir model had best fitness (ROC >80%), and Korean pine, spruces and larch had good fitness (ROC = 60%-80%). The predictions of Mongol scotch pine, a rare species, had low accuracy. At the regional scale, Korean pine, fir, spruces and Mongol scotch pine were the most sensitive to average annual precipitation, and larch was the most sensitive to slope. At local scale, Korean pine was the most sensitive to slope, fir and spruces to elevation and larch to slope position. In addition, this shift of the most important factor in species occurrence at different scale was accompanied by a change of distribution type. Korean pine was more clustered at regional scale (ROC=78.6%) than at local scale (74.4%), and its proportion increased in Fenglin Natural Reserve. Fir and spruces clustered at regional scale, but approached random distribution at local scale (ROC<60%), i.e., they occurred everywhere. Larch, the dominant species in the north, became more clustered at local scale (ROC increased from 71.7 to 82.0%) and was restricted to sites such as valleys. Scaling down from regional to local scale resulted in the changes of the most important factors affecting species distribution. Most species were sensitive to climatic factors at regional scale and geographic factors at local scale; however, larch was always the most sensitive to geographic factors due to the temperature inversion in the region.

Aims The purpose of the study was to determine the biomass (including fine roots), NPP, specific leaf area (SLA), leaf area index (LAI), and soil nutrients of Woodwardia japonica community under artificial coniferous forest in Jiangxi Province in subtropical China.
Methods Plants in quadrats were harvested and dry weight was measured. Leaf area was measured by scanning, and SLA was represented by the ratio of dry matter to leaf area. LAI of the population was estimated by SLA and leaf biomass.
Important findings The relationships between aboveground biomass (W1) and geometric parameters of W. japonica were established (W1=0.021H ^1.545(R²=0.790) and W1=2.518(D ²H)^0.616(R²=0.894), H: height; D: diameter). The biomass of herbage and shrub under coniferous plantation was 367.8 g·m^-2(52-932 g·m^-2), 4.7% of canopy layer. The accumulated litter under forest was 1 631 g·m^-2(672-2 763 g·m^-2). The above- and under-ground biomass of W. japonica community were 266.6 g·m^-2 and 212.6 g·m^-2, respectively. In total, the biomass of W. japonica population approximately accounted for 73.7% of the whole herbaceous layer. There was a significant negative-correlation between SLA and leaves dry matter content (LDMC). A leaf area (S) model was established in the form of S=21.922 6-0.152L ²+0.000 9L³(9.0≤L: max length of leaf ≤23.5;1.4 ≤ W: max width of leaf ≤5.9).LAI of W. japonica population was estimated as 1.8 m²·m^-2. Soil water content affected biomass of the community. A positive correlation between biomass and soil nitrogen concentration or soil organic matter (SOC) was identified.

Aims Comparison of populations of different plant species can reveal the formation mechanism and the influencing factors of the populations. We compared quantitative features of populations of Pinus tabulaeformis and P. armandii, which are the dominants in naturally regenerating communities, following water damage 17 years ago in part of the Fanjiazhuang section of the Caiyuhe Watershed of Qinling Mountain. We asked whether biological features of P. tabulaeformis and P. armandii influence the population size, age structure and population survival dynamics.
Methods We measured the height, basal diameter and age (number of whorled branches) of two individuals in a total plot area of 11 900 m² in 2005.
Important findings As a result of faster height and lateral growth, P. tabulaeformis had greater mean height and basal diameter than P. armandii, and individuals occupied larger vertical and horizontal space. The two populations had different height, diameter and age structures, and no consistenay, which indicated that size structure did not always reflect the age structure. The populations had different age structures, with that of P. tabulaeformis skewed to older trees and that of P. armandii in a near normal distribution. The age structure of P. armandii population was influenced by slope aspect, but that of P. tabulaeformis population was not. Both survivorship curves were the type Ⅱ, which indicated that both populations had similar survival dynamics. Therefore, the different biological characteristics of P. tabulaeformis and P. armandii led to different population size and age structure features, but not survival processes. This implied that environmental factors were the main determinants of population survival dynamics.

Aims Vallisneria species are very common and important in shallow lakes of the middle-lower reaches of the Yangtze River of China. Our objectives were to: 1) examine whether these co-existing Vallisneria species differ in sexual and clonal life-history traits, and 2) determine whether life-history traits explain the interspecific distribution pattern of these species.
Methods Field investigations were carried out to determine the distribution and coexistence pattern of the three Vallisneria species (V. spinulosa, V. natans and V. denseserrulata) in lakes of the middle-lower reaches of the Yangtze River. Life-history traits of sexual reproduction and clonal propagation of V. spinulosa and V. natans were determined and compared under field condition and uniform glasshouse environment.
Important finding V. spinulosa was the dominant species in these lakes, V. natans was very common and V. denseserrulata was rare in this region. V. spinulosa and V. natans widely coexisted in these lakes; they frequently displayed a clear interspecific zonation pattern, or V. natans individuals scarcely occurred in V. spinulosa communities. Field investigations and glasshouse experiments suggested great differences of sexual and clonal life-history traits between V. spinulosa and V. natans. V. spinulosa is perennial, and capable of extensive clonal propagation, while V. natans is annual and reproduces mainly by sexual seedling as well as limited clonal growth. Differences of resource-acquisition and competitive abilities, caused by trade-offs of resource allocation between sexual reproduction and clonal propagation, might determine the pattern of competitive coexistence of V. spinulosa and V. natans.

Aims Xixi wetland is located at the outskirt of Hangzhou, eastern China. Under the influences of human residents, farming and fishing activities for more than one thousand years, Xixi has changed to secondary farming wetland with 70% of the area covered by open water interfaced by narrow dikes and large islets. Urbanization and industrialization during the last 20 years has rapidly shrunken Xixi. We investigated species composition of vascular plants in Xixi to explore: 1) relationships between species composition and habitats, 2) species which should be protected in the restoration of Xixi and methods for their protection, 3) favorable habitats for native and wetland species, and 4) occurrence and effects of invasive exotic species in different habitats and methods for their control.
Methods The herbaceous habitats of Xixi were classified into five types based on plant composition, water level, and solar radiation: blazing high dike (BHD), shading high dike (SHD), blazing low dike (BLD), blazing high islet (BHI), and blazing low islet (BLI). Community composition of the five habitats was studied by quadrat sampling method. Important values (IV) were used to calculate diversity indices and DCA ordination. A total of 26 sites with 234 m² quadrats were sampled in this study.
Important findings There were 119 vascular species belonging to 103 genera and 44 families. Among them, 108 species were native, 11 were invasive exotic; 50 were wetland plants; 6 were legumes, and 35 were grasses or grasses relatives. Results showed that BHD, SHD, BLD, BHI had greater plant species richness than BLI, and BHD had the greatest native species and woody species richness. Invasive exotic species and wetland plant species were prevalent in BLI, and common in BHD, SHD, BLD and BHI. BHD may be in favor of the protection of native species, and may be good for resisting the invasion of exotic species, but may be an unfavorable habitat for wetland plants, BLI was reversed. BLD could maintain moderately native plant species richness and had higher proportions of herbs and wetland plant species. Therefore, well-managed BLD should be emphasized in Xixi for protection and enhancement of native vegetation diversity and wetland plant species richness. The invasive exotic species, such as Alternanthera philoxeroides, which were harmful to the landscape or harmful to maintain native species diversity, must be removed periodically.

Aims Annual or long-term actual evaporation and its response to precipitation pattern are poorly known. Our aims are to estimate average annual surface evaporation of bare sand dunes and explore the relationship between precipitation pattern and annual evaporation variance.
Methods Based on a meta-analysis of previous experiments, we used a process-based model to calculate the evaporation (EV) of bare sand dunes in Maowusu from day to multiyear scales. We also developed a simple Rainfall-EV model driven by amount and frequency of rainfalls, by which we explored the relationship between intensify of rainfall events and variance of annual evaporation.
Important findings The process-based model yielded reasonable short-term evaporation pattern after rainfalls and accumulative evaporation. The long-term average of evaporation from 1959 to 1992 is 166 mm, accounting for 56% of annual precipitation. Although there is no significant change of annual precipitation, the actual evaporation increased significantly with a tendency of 1.30 mm·a^-1. We suggested the significant increase (0.69 mm·a^-1) of small rainfall events (<5 mm) was the dominant reason of the increase of annual actual evaporation. The frequencies and amounts of strong rainfall contributed more to annual precipitation than annual evaporation, while weak rainfall events (<12 mm) kept relatively constant among years, providing about 100 mm evaporation. These resulted in less variance of annual evaporation than precipitation. Since the precipitation pattern among years apparently will influence annual evaporation, the simple Rainfall-EV model is able to predict annual evaporation effectively.

Aims Seed dispersal and seed predation are important on mechanisms of forest maintenance and degeneration. Understanding them can enable effective conservation measures, especially in Xishuangbanna tropical rainforest in China which is suffering severe pressures.
Methods Musa acuminata is a large herbaceous plant in Xishuangbanna, Yunnan Province. We investigated seed dispersal and spatial-temporal variation of seed predation in three habitats (wild banana communities, virgin rainforest and open habitat) in three different sites of Xishuangbanna (XTBG, Xinshan and Bubeng). We used two treatments excluding ants and rodents and surveyed community structure of ants and rodents to explore the relationship between abundance of predators and intensity of seed predation.
Important findings Bats were the most important, effective seed disperser, and birds also played an important role in seed dispersal, with approximately 75% of the mature fruits of M. acuminata dispersed at night and about 25% during daytime. After primary dispersal, seeds of M. acuminata were mainly removed by small rodents and ants. This seed predation was significantly influenced by season, site and habitat. Seed predation was significantly stronger in rainy than dry seasons (p<0.001). Seed predation in M. acuminata communities was the highest among the three habitats (p<0.001), and seed predation in Bubeng Nature Reserve, which had the least disturbance, was significantly lower than the other two sites (which were not significantly different at p>0.05). Seed removal was generally consistent with the abundance of rodents and ants in different seasons, habitats and sites. The interaction between sites and habitats and the interaction among seasons, sites and habitats had significant effects on seed predation. Compared to nearby forest and open habitats, Musa communities had the most abundant rodents and the highest seed predation and the lowest proportion of secondary seed dispersal by ants. In contrast, seed predation by rodents in forest and open habitat was relatively weak and a large proportion of post dispersal seed was removed by ants. Therefore, primary seed dispersal mostly by bats and birds is essential for M. acuminata seeds to escape seed predation.

Aims Isoetes sinensis (Isoeteaceae) is a critically endangered aquatic fern ally in China. Understanding the genetic differentiation of quantitative traits and local adaptation of the remnant populations should provide insight into the adaptation of different populations to their local environment and useful information for formulating appropriate conservation strategy.
Methods The quantitative traits of nine isozyme multilocus genotypes from three remnant populations of I. sinensis were investigated using nested analysis based on random block design in common-garden experiments. Population differentiation of allozyme (F_ST) and quantitative traits (Q_ST) were estimated using the Bayesian approach.
Important findings Of 14 quantitative traits examined, ten were found to be significantly different among populations and three were significantly different within populations. Multiple comparison by Turkey tests indicated that the mean values of five traits were the highest for the Songyang population and lowest for the Xiuning population, whereas the mean values of the macrosporangium characteristics and plant height were highest for the Jiande population and lowest for the Xiuning population. This result probably reflected different scenarios of founder effect, habitat competition ability and trade-off between vegetative and reproductive growth. Local adaptation was evaluated as a difference of Q_ST vs. F_ST value, and eight important reproductive fitness traits were found to be significant (Q_ST>F_ST, p≤0.05 ) under the selfing assumption, suggesting local adaptability in the remnant populations. It is more likely that there is a potential risk of outbreeding depression if genetic enhancement is implemented by translocation of individuals from different populations. Therefore, translocation among these remnant populations is not recommended. Instead, we recommend increasing gene flow within each population and improving habitat management by reducing competition with companion species in in situ conservation for Xiuning and Songyang populations. In the case of Jiande population, minimizing human disturbance should be considered as a top priority and an in situ conservation plot should be designated for the population.

Aims A growing number of studies have focused on evaluating spectral indices in terms of their sensitivity to vegetation biophysical parameters. We use a regression model, based on wavelet-transformed reflectance, and vegetation indices (VI) to estimate a wide range of soybean (Glycine max) canopy reflectances to study the sensitivity of wavelet-transformed reflectance and vegetation indices to soybean chlorophyll a concentration. We modify some VI to enhance their sensitivity to variations in chlorophyll a concentration.
Methods We collected soybean canopy hyperspectral reflectance and chlorophyll a concentration data in 2003 and 2004 at two sites in the black soil belt of China. We correlated reflectance, derivative reflectance and soybean chlorophyll a concentration and regressed vegetation indices (NDVI, SAVI, RDVI and MSRI) and soybean chlorophyll a concentration. We transformed soybean canopy reflectance with wavelet analysis and applied extracted wavelet energy coefficient in a regression model for estimation of chlorophyll a concentration.
Important findings Soybean canopy reflectance shows a negative correlation with chlorophyll a concentration in the visible spectral region, while it shows a positive correlation with soybean chlorophyll a concentration in the near-infrared region. Reflectance derivative has a strong relationship with soybean chlorophyll a concentration in the blue, green and red edge spectral region, with maximum correlation coefficient in the red-edge region. Four vegetation indices have strong correlations with soybean chlorophyll a concentration, with R² >0.75. The single variable regression model based upon wavelet-extracted reflectance energy can accurately estimate soybean chlorophyll a concentration, with R ² about 0.75, while R ² was 0.85 with the multivariate regression model. Our study indicated that wavelet analysis can be applied to in-situ collected hyperspectral data for soybean chlorophyll a concentration estimation with accurate prediction and in the future wavelet analysis methods should be applied to hyperspectral data for estimation of other vegetation biophysical and biochemical parameters.

Aims Our objective was to explore the effects of saline-alkali stress on photosynthetic apparatus of Helianthus tuberosus seedlings.
Methods H. tuberosus seedlings were treated with NaCl (50, 100, 150, 200, 250 mmol·L^-1) and Na₂CO₃ (25, 50, 75, 100, 125 mmol·L^-1) in plastic pots with sand. Others were cultured in modulated half-strength Hoagland solution as a control. We studied the effects of NaCl and Na₂CO₃ on net photosynthetic rate (P_n) and parameters of chlorophyll fluorescence by measuring chlorophyll content, P_n, stomatal conductivity (G_s) and fluorescence parameters after 7 days.
Important findings Significant increases of chlorophyll content, P_n and G_s compared with the control were observed under the 150 mmol·L^-1 NaCl treatment, whereas there were no effects on fluorescence parameters, F_v/F_m (maximal photochemical efficiency of photosystem Ⅱ (PSⅡ) while all PSⅡ reaction centers are open), F_m/F_o (another expression for the maximal photochemical efficiency of PSⅡ), Φ_PSⅡ (actual quantum yield of PSⅡ under actinic irradiation), q_P (photochemical quenching coefficient), and NPQ (non-photochemical quenching coefficient). But with greater NaCl concentration, the chlorophyll content, P_n, G_s and fluorescence parameters significantly decreased except for an increase of NPQ compared with the control. When H. tuberosus seedlings were treated with Na₂CO₃, chlorophyll content, P_n, G_s, F_v/F_m, F_m/F_o, Φ_PSⅡ and q_P significantly decreased and NPQ increased compared with the control. At the same concentration of Na ⁺, the decrease of chlorophyll content, P_n, G_s, F_v/F_m, F_m/F_o, Φ_PSⅡ, q_P and the increase of NPQ were higher in Na₂CO₃ stress than in NaCl stress. All results suggested that the tolerance of H. tuberosus seedlings to saline stress was higher than to alkaline stress.

Aims Our objective was to compare growth responses to soil Cd, as well as Cd uptake and accumulation in two ecotypes of Sedum alfredii.
Methods In a pot experiment, we planted one mining ecotype of S. alfredii and one non-mining ecotype in eight soils with different Cd levels (control, 12.5, 25, 50, 100, 200, 300, 400 mg·kg^-1) for two successive croppings.
Important findings The mining ecotype of S. alfredii grew healthy at all Cd supply levels. Its Cd concentrations in shoots and roots linearly increased with increasing soil Cd levels and reached a maximum of approximately 2 900 mg·kg^-1 (DW) and 500 mg·kg^-1 at 400 mg·kg^-1 treatment, respectively. Its Cd concentration in shoots were far higher than roots. In contrast, the growth of the non-mining ecotype was severely inhibited by soil Cd supply, as its shoot and root biomass significantly decreased compared with the control treatment. Cd concentrations in shoots and roots of the non-mining ecotype also increased with increasing soil Cd levels, but its Cd concentration in roots was higher than in shoots. At low soil Cd levels (≤50 mg·kg^-1), Cd concentration in roots of the mining ecotype was higher than the non-mining ecotype, while there were no significant differences between the two ecotypes at high Cd levels (100 and 200 mg·kg^-1). Increasing soil Cd levels from 0 to 400 mg·kg^-1 enhanced Cd concentration in shoots of the two ecotypes, and Cd concentration in shoots of the mining ecotype was always far higher than the non-mining ecotype at all Cd supply levels. These results indicate that the mining ecotype of S. alfredii has an extraordinary ability to tolerate and uptake Cd from soil and is proved to be a Cd hyper-accumulator.

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 Xylem embolism is a physiological response of tree species to adverse environmental factors, such as water deficit. However there is little research on relationships between phosphorus and xylem embolism. Our objectives were to 1) explore whether phosphorus could increase xylem embolism occurrence and 2) test the hypothesis of “drought tolerance by restricting sap flow in xylem".
Methods The tree species Acer truncatum and Ligustrum lucidum were chosen to study the response of xylem embolism (measured as percentage loss of hydraulic conductivity, PLC) to phosphorus addition under drought-stressed and well-watered treatments (soil water content of about 30%-40% and 70%-80% of field moisture capacity, respectively).
Important findings Daily PLC ranged from 60.7% to 70.7% in A. truncatum and 43.9%-72.3% in L. lucidum, indicating that occurrence and refilling of xylem embolism was a usual event in these woody plants. Phosphorus addition raised PLC significantly for A. truncatum at each water status and L. lucidum was subjected to drought. A. truncatum had more xylem embolism occurrence with drought than when well-watered, but there was no significant difference within two water status in L. lucidum. Drought could increase the embolism vulnerability of A. truncatum, causing higher percentage loss of hydraulic conductivity than in L. lucidum under the same water stress. Consequently, drought-resistant trees are not always invulnerable to water deficit. This might be a strategy for a water-limited environment. This study suggests that xylem embolism might be a “hydraulic signal" in plants. Once a plant is under water stress, its xylem conduits become cavited or embolized, resulting in decreased hydraulic conductivity and closure of stomata to maintain water balance by reducing water transportation and consumption. This study supports the hypothesis of “drought tolerance by restricting sap flow in xylem".

Aims Chinese fir (Cunninghamia lanceolata), an important tree of timber plantations in South China, is a fast-growing coniferous species with high yield and quality of wood. Since the forest soil in South China is highly heterogeneous in nutrients, our objective is to study responses of Chinese fir to soil heterogeneity.
Methods We used pot experiments under heterogeous and homogeneous environments to study tree growth, dry matter accumulation and allocation, root morphology and nutrient absorption efficency of three open-pollinated varieties of C. lanceolata ('Long 15', 'Jinping 45' and 'Jing 398') to detect the differences in their adaptability to the heterogenous nutrient environment.
Important findings The three varieties were significantly different in their adaptability to the heterogenous nutrient environment and in their response to soil patches. 'Jinpin 45' exhibited higher plant height, higher biomass accumulation and more developed roots in the heterogeneous environment than homogeneous environment, but 'Long 15' and 'Jing 398' grew better in the homogeneous environment. Although the responses of the three varieties were different, roots proliferated mainly in poor patches. 'Jinping 45' showed high root physiological plasticity in the heterogeneous environment, but 'Long 15' and 'Jing 398' were low and average, respectively, in the hererogeous environment. The root concentration of N, P and K in the heterogeous environment (poor-patch) was lower than in the homogeneous environment (rich-patch); this is different from Pinus massoniana, which had high nutrient absorption. However, concentration of nutrients was not lower in rich-patch than poor-patch. Further more, it can be inferred that 'Jinping 45' grew better in the heterogeneous environment than the homogeneous environment not only because of physiological plasticity but also because of a larger portion of biomass and nutrients distributed to leaves.

Aims Ecological risk assessments have paid increasing attention to the field release of transgenic Bt crops. Some studies have reported that Bt protein could enter the soil ecosystem through root exudates, crop residues, crop decomposition and pollen. Protein from transgenic Bt crops is a potential hazard for soil non-target organisms and biodiversity, and this may affect soil ecological function and soil nutrients. This study aims to evaluate the soil ecological risk of transgenic Bt cotton.
Methods A pot experiment with two types of transgenic Bt cotton, ‘BtXincai1’ and ‘BtJi668’, was conducted to study the effects of transgenic Bt cotton planting on rhizosphere soil microorganisms. The plant was carefully removed from the pot at seedling, budding, flowering, bolling and boll-opening stages. Rhizosphere soil approximately 0-5 mm in diameter was separated from bulk soil by gently shaking the root system. Samples were frozen at -20 ℃ after sieving for subsequent Bt protein analyses, or stored at 4 ℃ for microorganism analyses, which were begun within a day of sampling. Bt protein was analyzed by ELISA BOX. The populations of three main microorganism groups and some functional groups were measured by cultivation.
Important findings The content of Bt protein exuded by different transgenic Bt cottons and the degradation rate of Bt protein in different rhizosphere soils were different. Compared with the controls, transgenic Bt cottons seemed to stimulate the reproduction of rhizosphere soil bacteria and fungi. However, no significant effects on the populations of actinomycete, aerobic nitrogen fixing bacteria and kalium-solubilizing bacteria were observed. Transgenic Bt cottons increased the population of ammonifying bacteria and decreased that of inorganic phosphorus-solubilizing bacteria significantly at seedling and flowering stages, whereas they increased the population of aerobic cellulose-decomposing bacteria and decreased that of organic phosphorus-solubilizing bacteria significantly only at the flowering stage. ‘BtJi668’ also enhanced the population of aerobic cellulose-decomposing bacteria significantly at the seedling stage. The abundance of aerobic cellulose-decomposing bacteria and organic and inorganic phosphorus-solubilizing bacteria in transgenic Bt cottons rhizosphere soils changed. Although the total population of functional groups in transgenic Bt cottons rhizosphere soils was higher than in control cultivars, community diversity (H) and evenness (J) decreased and dominance concentration (C) increased. The change range of diversity indexes and population of functional groups in transgenic Bt cottons rhizosphere soils at the flowering stage was higher than at the seedling stage.

Aims The main aim of this study was to investigate the response of various physiology indexes, e.g., chlorophyll index value (stand for the relative content of chlorophyll, SPAD value), net photosynthetic rate (P_n), stomatal conductance (G_s), and root shoot ratio (R/S) in two genetypes of maize (Zea mays) to NH₃ concentration enrichment.
Methods We grew maize on Hoagland solution in PVC pots in open top chambers (OTCs). The experiment was a split-split plot design, which main treatments were two NH₃ concentrations (10 and 1 000 nl·L^-1). The sub-plot treatments of the experiment were two levels of nitrogen (high and low), and sub-sub-plot treatments were two N efficiency genotypes (high N efficiency, ‘NE5’, and low N efficiency, ‘SD19’). Air flow in OTCs was controlled by small fans and atmospheric NH₃ concentration was measured accurately by two methods (NH₃ determination tubes and GTL-C atmosphere detecting apparatus).
Important findings Under elevated atmospheric NH₃, there were significant differences (p<0. 05) for physiology indexes between the two varieties, ‘NE5’ and ‘SD19’. Under high N medium, compared with 10 nl·L^-1 atmospheric NH₃ concentration, the SPAD value, P_n and G_s of ‘NE5’ treated with 1 000 nl·L^-1 decreased 7.0%, 14.0% and 6.5%, respectively, and the corresponding targets of ‘SD19’ decreased 9.0%, 11.0% and 6.9%, respectively. Under low N medium, various physiology indexes of the two varieties significantly increased, i.e., the SPAD value, P_n and G_s of ‘NE5’ increased 5.7%, 7.1% and 17%, respectively, and the relative value of ‘SD19’ increased 7.0%, 11.0% and 22.0%, respectively. The results also demonstrated that under high N medium, the inhibition effect of increased atmospheric NH₃ on ‘SD19’ shoot biomass was obviously lower than that of ‘NE5’, while under low N medium, NH₃ concentration enrichment had more positive influence on ‘NE5’ (p<0. 05) than ‘SD19’. Moreover, the ratio of roots to shoots of ‘NE5’ and ‘SD19’ in the two atmospheric NH₃ concentrations was related to maize growth periods, i.e., there were different changes for their root and shoot biomass in three sampling time, but still obeying certain laws. All these results indicated that the absorbed atmospheric NH₃ by plants can improve crop nitrogen nutrition growing in low N medium, and there may be more significantly positive effect on low nitrogen efficiency genotypes.

Aims Ozone is a prominent gas pollutant that adversely affects vegetation, including visible leaf injury, growth and yield reduction. Our objective was to assess photosynthesis, growth and yield responses of field-grown wheat to increased ozone.
Methods We planted winter wheat (Triticum aestivum cv. Jia 403) in 12 plots of 2 m×2 m on 7 November 2005. After the wheat greened, we established 12 open-top octagonal (2.2 m high, 2 m diameter) chambers on 1 March 2006. Except rainy days, wheat was exposed to charcoal-filtered air, unfiltered air, and two treatments with ozone addition (DO100, DO150) from 13 March to 28 April 2006, for 8 h per day, for a total of 30 days. We measured diurnal gas exchange and P_n-PAR response curves of flag leaves at the early grain filling stage (after 25 days exposure to ozone) and components of yield at harvest.
Important findings High concentration of ozone altered gas exchange parameters, including stomatal conductance (G_s), leaf photosynthetic rate (P_n), transpiration rate (T_r) and intercellular CO₂ concentration (C_i). Apparent quantum yield (AQY), light saturation point (LSP) and light compensation point (LCP) were significantly decreased, suggesting photosynthetic capacity could also be changed, characterized as reduced photon-saturated photosynthetic rate (P_max). The decrease of photosynthetic activity was probably dominated by non-stomatal factors in combination with stomatal closure. In addition, ozone exposure caused leaf aging and decreases in plant height, ear length and number of grains per ear. Although similar responses were observed in plants exposed to ambient ozone concentration, we found no statistically significant differences at current concentration. We concluded that dynamic ozone exposure detrimentally affects photosynthesis, growth and yield of winter wheat.

Aims Plants have evolved self-defense mechanisms against insects and can produce insecticidal protein and other compounds. The development of proteomics has enabled study of the molecular mechanism of this defense. Oilseed rape (Brassica napus cv. Westar) is an important oil crop in China and suffers from damage caused by insect pests and disturbances such as hail. Our objective is to investigate changes of total soluble protein and induced individual protein in B. napus using mechanical damage to mimic insect feeding.
Methods We took two leaf samples from the same leaf of each plant 4 h apart and treated the first sample as mechanical damage. Total soluble protein (TP) of samples was measured by Bio-rad Protein Assay and separated by two-dimensional (2-D) polyacrylamide gel electrophoresis. Up-regulated proteins and new proteins were discriminated on the gel after staining. Two of eight different protein spots were analyzed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry and identified by Mascot in database of Matrix Science.
Important findings TP concentration in leaves increased when measured after wounding. The two proteins discriminated on the 2-D gel were the small subunit (SSU) precursor of ribulose-1,5-bisphosphate carboxylase (rubisco) and a mixture containing fructose-bisphosphate aldolase and coproporphyrinogen Ⅲ oxidase (COP). The sequence of rubisco SSU was first reported in B. napus, and the other two enzymes were reported in Arabidopsis thaliana, a relative of B. napus. All of these proteins have been shown to be involved in plant responses to stress. Thus we assume that these three proteins are important in maintaining plant physiological functions during wound-response in leaves of B. napus. This finding could be useful in understanding the relationship between plants and phytophagous insects at the proteomic level.

Aims Southern Hunan is the largest flue-cured tobacco-growing area in Hunan, China, aided by climate and soil conducive to the growth and development of tobacco. Our objectives were to evaluate climate feasibility, soil fertility and tobacco quality, and provide a scientific basis for classifying southern Hunan tobacco-growing areas.
Methods We obtained climate data for 30 years, including different growth and development periods and total sunlight hours during the field period, for the counties of Xintian, Yongxing, Jianghua, Jiangyong, Daoxian, Ningyuan, Guiyang, Jiahe, Hengnan and Lanshan from the Hunan Meteorology Bureau. We collected 1 225 soil samples from 2002 to 2003 and determined soil parameters, including pH, organic matter, nutrient elements and cation exchange capacity (CEC). We selected three or four flue-cured tobacco varieties from southern Hunan in 2004 and determined six appearance quality indexes and nine sensory quality indexes of 15 tobacco samples of C3F grades. We estimated climate feasibility index (CFI), soil feasibility index (SFI), appearance quality index (AQI) and sensory quality index (SQI) for tobacco by applying membership function and estimating weight values for each index by using principal components analysis.
Important findings The CFI was (79.59%±3.96%) and ranged from 74.71% to 83.98%. The areas had feasible temperature, a long period with average daily temperature ≥20 ℃, high accumulated temperature of ≥10 ℃, small day-and-night temperature differences, abundant precipitation, high humidity, and low sunlight percentage during field periods. The SFI was (43.92%±15.49%) and ranged from 13.32% to 82.82%. The soil had high nutrient storage capability and was rich in organic matter, total N, hydrolytic N, available P and most micro elements; however, pH was neutral to slightly alkaline and total P, total K and available K were insufficient for tobacco. Furthermore, the ratio of exchangeable Ca to Mg was unbalanced, available S was high and available B was lacking. The AQI and SQI were (86.65%±3.29%) and (63.08%±0.74%), respectively. Tobacco leaves had good maturity, open configuration and high quality of aroma; undesirable taste and biting taste were small.