Aims We studied the relationships between functional traits of Quercus species and their responses to meteorological factors in the temperate zone of the North-South Transect of Eastern China (NSTEC), with the objective of finding the dynamics of the relationship between plants and environment.

Methods We measured functional traits of Quercus dominant trees in their eleven core habitats in the temperate zone of NSTEC and analyzed relationships among the traits and their responses to meteorological factors.

Important findings Although leaf mass per area (LMA) and leaf dry matters content (LDMC) could indicate life strategy of the Quercus trees, the implications of LMA was more obvious. The relationships among leaf nutrients based on area were more significant than those based on weight, and the relationships between leaf nitrogen and phosphorus contents were more significant than their relationships to potassium content except for the relationship between phosphorus content per leaf area (P_area) and potassium content per leaf area (K_area). This could be interpreted that potassium does not take part in synthesizing stable structural materials directly in plants. Mean annual temperature (MAT) and mean annual sunlight (MASL) were the main meteorological factors that affected the relationships among functional traits. Compared to leaf nutrients based on weight, those based on area were affected more by MAT and MASL. Mean annual rainfall (MAR) had an effect only on the relationships between P_area and other traits.

Aims Improved understanding of tree growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. Coniferous forests in Wolong National Natural Reserve occupy broad elevational ranges with varied geology and topography and thus have great potential for dendroclimatological studies. However, little is known about the growth-climate relationships in this region compared with the nearby Tibetan Plateau. Our objective was to determine the main climate responses in diameter growth and examine the regional climate variability within this ecological complex area.

Methods We used standardized dendroecological methods to study the effects of climatic variability on radial growth of a subalpine conifer, Abies faxoniana, which is the dominant and economically most important tree species in this region. We sampled 58 stands of A. faxoniana in a treeline site (3 450 m) and extracted increment cores for radial growth analyses. Several statistics were used to identify common patterns of interannual growth variability, and correlation and regression analyses were used to identify climatic factors associated with that variability.

Important findings The main limiting factor for tree growth was temperature in summer (June to August), followed by temperature in early spring (March), relative humidity from June to September of the current year and precipitation in October of the prior year. The summer (June to August) temperature reconstruction, spanning A.D. 1850-2008, was verified with independent data and accounted for 28.8% of the actual temperature variance during the period in common period (1955-2008). The most obvious characteristic of the reconstructed temperature was a significant warming trend after the 1940s. Before the 1940s, the climate of this region was consistent cold, with cold intervals in the 1850s-1870s and the 1890s-1930s. Because the low-frequency variation of the reconstruction agreed with previously published tree-ring proxies (ice cores of nearby glaciers), it appears that our reconstructed series was reliable and could aid in the evaluation of regional climate signal. Wavelet spectral analysis indicated the existence of some decadal (10-16 years) and interannual (2-8 years) cycles, which probably are ascribed to solar variability and El Niño-Southern Oscillation (ENSO), respectively.

Aims Soil enzymes often play an important role in maintaining soil fertility and the biogeochemical cycle in soil ecosystems. Many soil enzyme studies have examined decomposition of leaf litter, but few have addressed decomposition of fine roots. Our objectives were to determine soil enzyme dynamics during fine root (including grass root) decomposition and whether variation of soil enzymes is linked to chemical composition of fine roots.

Methods We placed 560 intact soil cores in nylon bags with 0.25 mm mesh in Betula luminifera-Hemarthria compressa (HN), Betula luminifera plantation (H), Hemarthria compressa grassland (NC) and Cryptomeria fortunei plantation (LS) for 1 year. Intact soil cores were sampled at 30, 90, 180, 270 and 365 d from the starting date. On each sampling date, we collected fine root (including grass root) and soils from each soil core and measured decomposition rates, chemical composition of fine root (including grass root), soil enzymes and soil microbes.

Important findings Soil urease, sucrase and acid phosphatase activities were highest in HN. Soil urease and acid phosphatase activities were lowest in LS (p < 0.05). Soil urease activity in HN, NC and LS was positively correlated to root decomposition rates. Sucrase activity in HN, soil acid phosphatase activity in NC and soil polyphenoloxidase in LS were positively correlated to root decomposition rates (p < 0.05). Soil urease activity was negatively correlated to C/N and absolute content of cellulose in decomposing roots, except for H (p < 0.05). Soil polyphenoloxidase activities in HN, H and LS were negatively correlated with absolute content of cellulose in decomposing roots. The correlation between soil urease activity and the number of aerobic azotobacter and soil fungi was significant. Moreover, soil surcease activity was significant positively correlated with cellulolytic bacteria numbers in HN. Soil acid phosphatase activity in H and NC was significant positively correlated with bacteria and cellulolytic bacteria numbers (p < 0.05). We concluded that it is beneficial to improve soil enzymes activities in HN, which is formed by two different plant life forms, soil urease activity provided information on the fine root (including grass root) decomposition rate, C/N in fine root (including grass root) was one of the important factors influencing soil urease activity in these plantations, and soil enzyme activity was associated with the number of soil fungi, soil aerobic azotobacter, soil cellulolytic bacteria and soil bacteria.

Aims Urban land use has dramatically changed ecosystem functions especially carbon sequestration and storage in the built-up area. Our objective was to assess carbon sequestration and storage by estimating the biomass and net primary productivity (NPP) of urban vegetation including trees, shrubs and lawns with consideration of the effects of garden management (pruning and mowing).

Methods Biomass and NPP from all trees, shrubs and lawns were estimated from 346 random quadrats. Allometric equations were used to calculate tree biomass from diameter at breast height and total height. An increment borer was used to measure trunk increment. Biomass and NPP from shrubs and lawns were estimated by destructive sampling. Management activities were recorded through actual measurements and the records of gardeners.

Important findings Trunk growth rate of individual urban trees is two times that in native forest. Pruning accounts for 30% of tree NPP. Carbon sequestration per unit of Taizhou built-up area is estimated to be 2.1 × 10³ kg C·hm^-2·a^-1(with trees, shrubs and lawns contributing 64%, 9% and 27%, respectively), which is lower than native forest. We infer that the carbon sequestration ability of Taizhou built-up area could meet the level of native evergreen broad-leaved forest if vegetation coverage is increased from 23% to 46%.

Aims Quercus acutissima is widely distributed in China. Because of high resistance to drought and the adaptation to poor soil condition, it is commonly planted in mountainous and hilly areas for soil and water conservation and wood production. Our objective is to study its growth and nutrient use strategy for the purpose of better plantation management.

Methods We analyzed biomass, nutrient contents and nutrient distributions of 12-year-old Q. acutissima stands at two different sites at Hongyashan Forest Farm, Chuzhou, Anhui, China: a poor site with high gravel content and low soil nutrient concentration and a rich site with low gravel content and high soil nutrient concentration.

Important findings In the poor site, the aboveground biomass of Q. acutissima was 49 180.2 kg·hm^-2, total nutrient accumulation in the aboveground biomass was 633.9 kg·hm^-2 and the storage of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) was 119.9, 18.7, 88.5, 368.6 and 38.2 kg·hm^-2, respectively. In the rich site, the aboveground biomass was 90 774.8 kg·hm^-2, total nutrient accumulation was 993.6 kg·hm^-2 and the storage of N, P, K, Ca and Mg was 203.5, 23.0, 146.9, 553.6 and 66.6 kg·hm^-2, respectively. Results indicated obvious effects of site conditions on biomass productivity and nutrient accumulation of Q. acutissima plantations. Moreover, the nutrient accumulation coefficient of Q. acutissima was higher, while the nutrient concentration of litterfall was lower in the poor site than in the rich site. Therefore, adaptation of Q. acutissima to poor soil conditions involved increased nutrient uptake, increased internal nutrient cycling and reduced nutrient loss through litterfall.

Aims Suaeda salsa can grow in the intertidal zone or on saline inland soil. The intertidal population is mainly affected by high salt concentration, hypoxia and low temperature, while the inland population is mainly affected by salt and drought. We hypothesized that S. salsa from the intertidal zone would have a greater ability to regulate salt accumulation or translocation compared with S. salsa in saline inland habitats. Therefore, our objective was to investigate the effects of salinity on growth, photosynthetic oxygen evolution and ion accumulation of two populations of S. salsa, i.e., to determine how two populations of S. salsa adapt to their different habitats.

Methods After pre-culture for 40 days, seedlings of both populations were treated with 1, 200 and 600 mmol·L^-1 NaCl. The experiment was terminated 20 days after final NaCl concentrations were reached. Then we determined the organic dry weight of shoots and roots, content of chlorophyll and the rate of photosynthetic oxygen evolution in leaves and contents of Na⁺ and Cl^- in leaves and roots of seedlings of the two S. salsa populations.

Important findings The organic dry weight of shoots and roots of both populations was not affected by 200 mmol·L^-1 NaCl, indicating that both populations had high salt resistance. Under all treatments, the rate of photosynthetic oxygen evolution was higher in leaves of S. salsa from saline inland than that in the intertidal population, while the opposite trend was true in the chlorophyll a/b ratio. The Cl^-content in leaves of S. salsa from the intertidal zone was lower than that in the saline inland habitats, while the opposite trend was true in the Cl^- content in roots, which suggests that S. salsa from the intertidal zone may employ superior control of ion accumulation (especially for Cl^-) in roots or ion translocation from roots to shoots compared with S. salsa from saline inland. These traits may affect the distribution of S. salsa in natural saline environments.

Aim Arbuscular mycorrhizal (AM) fungi were inoculated into the seedlings of Elaeagnus mollis, an endangered plant in China. Our objectives were to study the impact of AM fungi inoculation on the soil micro-area in the rhizosphere of E. mollis seedlings using a greenhouse pot experiment.

Methods The experimental design included separate inoculation (Glomus mosseae = GM or Acaulospora delicata = AD) and mixed inoculation (GM + AD); control groups were not inoculated. We determined the infection rate of AM fungi, biomass, infection rate of mycorrhizae, number of microorganisms in the rhizosphere, soil pH, soil enzyme activity, N and P nutrients in the rhizosphere, etc.

Important findings AM fungi infected the three inoculated groups, among which the infection rate of GM + AD was the greatest, up to 90.5%. Compared with the control group, the biomass of inoculated groups improved markedly (p < 0.05) and the biomass of the GM + AD group was 2.2 times that of the CK group. AM mycorrhizae impacted microbial populations on the roots; the number of bacteria, actinomycetes and nitrogen-fixing bacteria on the root surface increased significantly (p < 0.05). The AM mycorrhizae made the pH in the rhizosphere decrease, and this was significantly negatively correlated with the infection rate (p < 0.05). The activity of soil phosphatase, urease and protease in the rhizosphere of inoculated groups increased. Moreover, the increase of their activity was significantly correlated with mycorrhizal infection rate (p < 0.01). The phenomenon that the N and P elements directly absorbed by plants enriched the rhizosphere soil of inoculated groups was significantly correlated with the mycorrhizal infection rate (p < 0.05). AM formation improved the micro-ecological environment of E. mollis seedlings and increased soil fertility in the rhizosphere.

Aims Arbuscular mycorrhizal fungi can directly or indirectly affect plant secondary metabolic processes. Camptothecin, a secondary metabolite in a special Chinese tree Camptotheca acuminata, has gained great attention for its remarkable inhibitory activity against tumor cells. The effect of two arbuscular mycorrhizal fungi belonging to two genera on the accumulation of camptothecin at different growth times of C. acuminata seedling was carried out in the present study.

Methods The selected sterile seeds of C. acuminata were sown in sterilized matrix (a mixture of soil and sand) in the greenhouse. Seedlings with similar height and crown were selected and divided into three groups (30 pots per group). Each group of C. acuminata seedlings was inoculated with a species of arbuscular mycorrhizal fungi Acaulospora mellea or Glomus intraradices, or non-mycorrhizal inoculation when seedlings unearthed 20 days, 40 days and 60 days, respectively. After 30 days of treatment, camptothecin contents and yields in the seedlings of C. acuminata were determined.

Important findings All inoculated seedlings were infected by arbuscular mycorrhizal fungi and formed arbuscular mycorrhiza after 30 days of co-cultivation. The results showed that camptothecin yields (camptothecin contents multiplied by biomass) in mycorrhizal seedlings were significantly higher than non-mycorrhizal seedlings. Furthermore, the increase of camptothecin yields in mycorrhizal seedlings was mainly credited to the increase of camptothecin contents in seedlings (especially in leaves) inoculated at early stage (20 days of seedlings emergence) or to the increase of plant biomass in seedlings inoculated at late stage (60 days of seedlings emergence).

Aims The major objective was to explore the difference in the systematic induced effects of mechanical wounding on Bt corn and conventional corn after the first leaf of corn seedlings was mechanically wounded.

Methods Two Bt corns, ‘5422Bt1’ (Bt11) and ‘5422CBCL’ (Mon810), as well as their conventional corn ‘5422’ were used to detect changes in the content of direct defense chemical DIMBOA and expression of its genes (Bx1, Bx6 and Bx9), content of direct defense chemical total phenol and expression of its gene (PAL), direct defense protein genes (MPI and PR-2a), and the indirect defense chemical volatile genes (FPS and TPS) in the non-wounded parts (second leaf and roots) by employing chemical analysis and gene expression analysis methods after the first leaf of corn seedlings was mechanically wounded for 6 h.

Important findings Mechanical wounding systematically induced the expression of PAL and TPS in the second leaf and PAL and FPS in the roots of conventional corn ‘5422’ as compared with the healthy plants, which significantly increased the DIMBOA content in the second leaf but reduced the DIMBOA content and its gene expression of Bx6 and Bx9 in the roots. In addition, mechanical wounding systematically induced the gene expression of Bx6, PAL, PR-2a and TPS in the second leaf and Bx6, Bx9, PAL, MPI, PR-2a and TPS in the roots of Bt corn ‘5422Bt1’, resulting in increased DIMBOA content of the second leaf. In terms of ‘5422CBCL’, mechanical wounding systematically induced the gene expression of Bx9, PAL, PR-2a and TPS in the second leaf and the gene expression of Bx6, PAL, MPI and TPS in the roots, which remarkably increased the total phenol content in the roots. The systematic induced effect of mechanical wounding on the chemical defense response is more obvious in the two Bt corns as compared with the conventional corn ‘5422’, suggesting that there is a synergistic relationship between the Bt gene introduction and chemical defense response during the systematic induced defense processes inflicted by mechanical wounding.

Aim Our primary objective was to establish an effective method of near infrared reflectance spectroscopy (NIRS) for estimating leaf nitrogen content in rice, which would help with nitrogen diagnosis and dressing fertilization in rice production.

Methods Using the techniques of partial least square (PLS), principal component regression (PCR) and stepwise multiple linear regression (SMLR), we established four NIRS-based models for estimating nitrogen content (NC) in fresh leaf and leaf powder of rice cultivars under varied nitrogen application rates.

Important findings The coefficient of determination (R_C²) and root mean square error for calibration (RMSEC) of NC models with fresh leaf were 0.940 and 0.226, respectively, whereas the R_C² and RMSEC of NC models with leaf powder were 0.977 and 0.136, respectively. We tested the accuracy of models with independent experiment datasets by the determination coefficient (R_CV²) and root mean square error of cross-validation (RMSECV), and the determination coefficient (R_V²) and root mean square error of external validation (RMSEP). With fresh leaf, the R_CV² and RMSECV of NC models were 0.866 and 0.243, respectively, while the R_V² was >0.800 and RMSEP was <0.500. With leaf powder, the R_CV² and RMSECV of NC models were 0.900 and 0.202, respectively, whereas the R_V² and RMSEP were 0.944 and 0.142, respectively. Overall, the performance of the models with leaf powder is better than that with fresh leaf in rice.

Grasslands in China cover vast, continuous areas and account for about 40% of Chinese land area. Most are located in the eco-geographical fragile region, are sensitive to climate change, and play important roles in regulating the carbon dioxide concentration in the atmosphere. Our objective was to review recent studies on soil respiration of grassland in China. Most studies were conducted in Northeast Plain, Inner Mongolia and Tibetan Plateau. Diurnal dynamics of soil respiration are controlled by temperature, seasonal patterns are controlled by temperature and/or water depending on the limiting environmental factors, and inter-annual variability is mainly determined by water. In addition, there is great spatial heterogeneity driven by mean annual precipitation and soil total nitrogen content. Responses of soil respiration to global changes were complicated and depended on the interaction of each factor. Most recent soil respiration models failed to incorporate the modulation of soil and biotic factors and their interaction. Key issues and suggested future research topics are 1) soil respiration in temperate desert grassland, 2) soil respiration during non-growing season, 3) comparison study of grassland soil respiration on different spatial and temporal scales, 4) simulation study of grassland soil respiration and 5) remote sensing of grassland soil respiration.

The light and CO₂ response curve of photosynthesis is an important tool to study plant physiology and plant ecology that can provide a scientific basis for the response of plant photosynthetic properties to environmental factors. This review considered the progress and potential weaknesses of light and CO₂ response models of photosynthesis and discussed research trends. Photosynthesis, which involves energy of light, absorption, energy conversion, electron transfer, ATP synthesis, CO₂ fixation etc., is a complex physical and chemical reaction process. It includes three basic steps: the primary reaction, the assimilatory power forms and the carbon assimilation, and each link may directly influence other processes. Classical models on photosynthetic light response only involve with light energy absorption, and biochemistry models do with the assimilatory power to form as well as carbon assimilation. A future direction of research of the mechanistic model of photosynthetic light response is the primary reaction of photosynthesis, namely participation the energy of light absorption, the transmission and the transformation of the harvesting light pigment member the physical parameter (e.g., the light-harvesting pigment molecules, light energy absorption cross-section of the harvesting pigment, the mean lifetime of the harvesting light pigment) unify in the biochemistry model.

Fuel is the basic component of forest ecosystems. It is one of the most important factors that influence forest fire ignition and fire severity. Hence, it has drawn much attention from researchers worldwide. We reviewed the current status of forest fuel studies from four aspects: 1) forest fuel properties, including physical and chemical properties, and flammability of forest fuels, 2) fuel models and fire behaviors, 3) methodologies for inventory and mapping of fuel types and fuel loads, and 4) forest fuel management. We also discuss the future direction in forest fuel studies, including 1) forest fuel studies at site, regional, and country-wide scales, 2) fuel models and fire behaviors, 3) combining observational and experimental studies with computer simulation and spatial analysis technologies for long-term predictions of fuel treatment effects over large landscapes, and 4) fuel treatment and carbon budget under global climate change. There are significant implications for forest fire management and forest fuel research in China.

Aims The bamboo Fargesia denudata is one of the Giant Panda’s main food sources and also affects the structure and dynamics of Giant panda habitat in the subalpine coniferous forests of southwestern China. Bamboos are thought to influence forest regeneration by suppressing tree recruitment. Our objectives were to examine the clonal plastic response of F. denudata by studying (1) biomass allocation and clonal morphological plasticity under different canopy conditions and (2) environmental conditions most conducive for growth and survival.

Methods In September 2007 and July-August 2008, we measured population density, biomass of ramets and modules, and clonal morphological features of F. denudata in four canopy conditions, i.e., forest understory (Fu), small gap (Sg), middle gap (Mg), and large gap (Lg), in an Abies faxoniana forest in Wanglang National Nature Reserve in northwestern Sichuan, China. The data were analyzed statistically by One-Way ANOVA using SPSS13.0.

Important findings The biomass, height, and basal diameter of ramets and biomass of modules were highest in the Sg canopy condition. With the increase of canopy cover, there were increases in biomass allocation to leaves, specific leaf area and percentage of branching and decreases in biomass allocation to roots and number of roots. Specific stem length and specific rhizome length were significantly lowest in the Sg canopy condition. Branching intensity of rhizomes was significantly higher in Sg and Mg. These results indicated that biomass allocation and morphological features of F. denudata are significantly different under different canopy conditions, for efficient utilization of light. Sg is the most suitable canopy condition for growth of F. denudata.