Aims The biomass of tropical forests plays an important role in the global carbon cycle; however, the distribution of tropical forest biomass based on vegetation index is seldom explored. Our objectives were to evaluate relationships between biomass and vegetation indices and to determine the spatial distribution of the aboveground biomass of tropical forest in Bawangling, Hainan Island, South China.
Methods Using measurements of forest biomass from 135 sample plots distributed over the study area, we correlated four vegetation indices (normalized difference vegetation index (NDVI), moisture vegetation index using Landsat’s 5 (MVI5), moisture vegetation index using Landsat’s band 7 (MVI7) and ratio vegetation index (RVI)) with aboveground biomass (total biomass, climax species biomass and pioneer species biomass) using the Pearson correlation method. We also developed models describing the relationships between forest aboveground biomass and vegetation indices using stepwise linear regression analysis. Three maps of biomass components were produced using the developed models, and residual maps were used to test the validity of the models.
Important findings MVI7and MVI5 are most effective for total biomass and climax species biomass, whereas NDVI and RVI seem to be good indices of pioneer species biomass. The strongly predictive percent areas for total species, climax species and pioneer species biomass models were 69.24, 73.98 and 88.08, respectively. Simulated biomasses of total species and climax species were distributed in the center, north and southwest parts of the study area; however, simulated biomass of pioneer species was scattered.

Aims Co-inertia analysis is infrequently used when there are few environmental variables or little collinearity among them. Ecologists usually prefer the widely used canonical correspondence analysis. Our objective was to compare the results of co-inertia analysis and canonical correspondence analysis in the ordination of a plant community in a habitat represented by few environmental variables.
Methods We compared the results of PCA-CA co-inertia analysis (PCA-CA COIA) and canonical correspondence analysis (CCA) ordination of a Phellodendron amurense community in Xiaolongmen woodland, Beijing, China. The correlation of corresponding ordination axes of two methods was measured by Spearman’s rho correlation.
Important findings PCA-CA COIA and CCA produced mostly consistent results. Both first axes were correlated with elevation, whereas the second axis of PCA-CA COIA corresponded to the third axis of CCA and the third axis of CCA corresponded to the second axis of PCA-CA COIA. The first three axes of both methods were significantly correlated with elevation, slope position, soil thickness and litter layer thickness. The eigenvalues of the ordination axes and the cumulative percentage variance of species-environment relation in PCA-CA COIA were higher than that in CCA.

Aims Lianas (woody vines) are important floristic and ecological elements in forests throughout the world, especially in tropical and subtropical areas. However, ecological studies on lianas are relatively scarce because field research is difficult. Our objectives were to develop liana biomass regression models, examine liana biomass composition and distribution in a natural moist evergreen broad-leaved forest, and assess the effects of anthropogenic disturbances on the biomass of lianas.
Methods We compared power functional models for biomass of canopy lianas (length ≥5.0 m) and understory lianas (length ＜5.0 m) based on 48 samples of lianas, using variables of basal diameter, length, and squared basal diameter × length. In the Ailao Mountains of southwestern China, we established three 20 × 20 m sample plots in each of a natural undisturbed moist evergreen broad-leaved primary forest and four secondary forests: old (100 a) and younger (50 a) secondary Lithocarpus forests, a Populus bonatii secondary forest and an Alnus nepalensis secondary forest. In each plot, we enumerated all liana stems ≥0.5 m in length (from the roots) and measured their basal diameters (30 cm along the stem from roots).
Important findings The regression model developed by liana basal diameters had the highest correlation coefficients and is preferred for practical use because measurement of liana basal diameter is easy and accurate. The total aboveground biomass of lianas in the natural moist evergreen broad-leaved forest was 9.82×10³ kg·hm^-2, 99.70% of which was canopy lianas. Anthropogenic disturbances result in the decrease of liana biomass. The biomass of understory lianas was relatively greater in younger secondary forests, but the biomass of lianas (especially large canopy lianas) was significantly lower. The aboveground biomass of lianas in the old secondary Lithocarpus forest was 91.03% of that of the natural moist evergreen broad-leaved forest, after about 100 years of restoration succession.

Aims There is increasing need for regional estimates of leaf area index (LAI) because it is an essential input for many eco-hydrological processes models; however, there has been a lack of effective methods for its estimation. Picea crassifolia is the dominant species in the forest ecosystem of Qi- lian Mountains and is critical to the eco-hydrological processes of the ecosystem. Our objective is to compare methods for determining canopy LAI of this P. crassifolia forest.
Methods We investigated canopy LAI with an LAI-2000 canopy analyzer, hemispherical photography and allometric regression on tree height and diameter at breast height (DBH). The value was underestimated by the two instruments because of clumping in the conifer forest. In order to adjust the LAI measured and obtain the spatial distribution of LAI, we first measured the clumping index by Tracing Radiation and Architecture of Canopies (TRAC). Then we calculated the adjusting coefficient by the clumping index, which was used to adjust the LAI value measured by hemispherical photography. Then, we determined the relationship between adjusted LAI and vegetation indexes retrieved by high resolution remote sensing data (QuickBird) and estimated the spatial distribution of canopy LAI.
Important findings The values of canopy LAI were 1.03-3.70 by LAI-2000 canopy analyzer, 0.48-2.26 by hemispherical photography, and 2.27-8.20 by allometric regression. LAI value by allometric regression on tree height and DBH was used for assessing the measurement accuracy by the other two indirect measurement techniques. We found the two instruments (LAI-2000 canopy analyzer and hemispherical photography) under estimated the canopy LAI of the forest by about 3.14-3.86 times. We built statistical models between adjusted LAI and vegetation indexes and selected the optimal model, i.e., correlation between normalized difference vegetation index and LAI, through validating.

Aims Our objective was to evaluate the performance of BIOCLIM in predicting geographical distributions of tree species in China and to determine the impacts of sample size and species traits on predictive accuracy.
Methods BIOCLIM model was used to predict the geographical distribution of 12 deciduous Quercus species differing in ecological traits and sample sizes. We used data from museum or herbarium collections and 18 layers of grid-data of meteorological variables at 6′×6′ resolution to run the model. We evaluated the quality of model predictions with area under the receiver operating characteristic curve (AUC) and Kappa statistic.
Important findings Model performance was improved and the variability in predictive accuracy was reduced with increasing sample size. Reasonable predictions to county-level resolution can be achieved with a sample size of 25 data points. On average, 75-100 observations were found to be sufficient to obtain maximal accuracy. Furthermore, we found that accuracy of BIOCLIM was greater for species with narrower geographical range and limited environmental tolerance than those with broader range and greater tolerance.

Aims Litter reduces surface runoff directly by an interception effect and indirectly by a barrier effect. Our objective is to study the effects of litter in Pinus caribaea stands on runoff and nitrogen and phosphorus losses by analyzing their runoff.
Methods We collected runoff from a P. caribaea stand with litter and a P. caribaea stand without litter in Foshan, Guandong Province and analyzed concentrations of nitrogen and phosphorus in the runoff in the lab.
Important findings Annual runoff amounts of the stands with and without litter were 12.6 and 51.8 mm, respectively, with >90% of annual runoff in summer. The relationships between rainfall and runoff in both stands were linear. Except for July 2007 and February 2008, monthly N concentration of the stand with litter was greater than the stand without litter, which was mainly caused by the difference in runoff amount between the two stands. Generally, monthly P concentration in the stand with litter was greater than that in the stand without litter. A negative exponent relationship existed between runoff and N concentration. Annual N losses of the stands with and without litter were 341 and 983 g·hm^-2, respectively, accounting for 73% and 64% of their annual N losses, respectively. Annual P losses of the stands with and without litter were 6.5 and 21.5 g·hm^-2, respectively. The greatest monthly P losses of the stands with litter and without litter occurred in June 2008, accounting 46% and 60% of their annual P losses, respectively. Therefore, N and P exports from P. caribaea stands could be significantly reduced by keeping litter in place.

Aims Our objectives are to explore the effect of nitrogen availability in soil on the accumulation of the secondary metabolites of plants growing in different areas, to test the C/N hypothesis, and to address reasons for the variability of content of active constituents in medicinal herbs growing in different areas.
Methods We surveyed plants and soils in 44 populations of a medicinal plant, Erigeron breviscapus. We analyzed total and active nitrogen of soil samples and total flavonoids, scutellarin, caffeates and nitrogen in plant samples. Linear regression analysis was used to study relationships between soil nitrogen availability and active constituents of plants.
Important findings The contents of flavonoids and caffeates in plants were negatively correlated with soil nitrogen availability and plant nitrogen content, as predicted by the carbon/nutrient balance hypothesis. Variation in available soil nitrogen accounted for 17%-30% of the variation in the content of secondary metabolites of plants. In contrast, variation in available nitrogen accounted for about 80% of the variation in content of total flavonoids in the rendizina and about 60% of content of scutellarin and caffeates in the non-rendizina. It appeared that effects of nitrogen availability on the accumulation of secondary metabolites in the plant were affected by other factors, such as genetic and environmental variation. The content of flavonoids and caffeates in plants growing in different areas varied with differences in nitrogen availability, ecological factors and genotypes.

Aims Our objective was to analyze population quantitative dynamics of the rhizomatous woody clonal plant Eremosparton songoricum, a rare dwarf shrub of mobile or semi-fixed sand dunes of central Asian desert.
Methods We investigated rhizome structure along three transects at the edge of two dune populations of E. songoricum (riverside population A at 46°31.09′ N, 88°33.06′ E; hinterland population B at 46°28.07′ N, 88°33.07′ E) in Gurbantuggut Desert in Xinjiang, China. We used rhizome length as the unit of the populations instead of ramets. Based on rhizome structure, we constructed static life tables, survival curves, fecundity schedules and Leslie matrix modes for the two populations and predicted their dynamics in the next 15 years.
Important findings The survival curves of the two E. songoricum populations were the Deevey Type I and mortality rates were low at the early stage. For population A, the net reproductive rate (R₀), the intrinsic rate (r_m) and the finite rate (λ) were low, indicating that the size of population A would decline; this agreed with the prediction of the Leslie matrix model. For population B, R₀, r_m, andλwere moderate, indicating that the size of population B would slowly increase in the future. This result was generally consistent with the prediction of the Leslie matrix model, which showed that population B would first decrease and then increase in the next 15 years.

Aims Heteracia szovitsii is a common ephemeral Asteraceae species that germinates in early spring in the Junggar Desert of China and produces three types of achenes with different morphologies in one infructescence. To better understand how this species is adapted to its desert habitat, we studied 1) the morphological, structural and dispersal characteristics of the three types of achenes and 2) according to the bet-hedging strategy, how heterocarpy spreads the risk of survival in the desert environment.
Methods For the three types of achenes, we recorded number, mass, morphology, surface ornamentation (via scanning electron micrographs), pericarp structure, dispersal distance and landing time in the laboratory and mode of dispersal and its duration in the field.
Important findings Compared with central achenes, the pericarps of peripheral and intermediate achenes were thicker, darker in color, and contained a higher amount of phenolic compounds and more sclerenchyma, which could protect the embryo better and cause the seeds to be more dormant. Embryo mass of peripheral and intermediate achenes was greater than that of central achenes, and thus could produce larger and more competitive seedlings. After maturation, central achenes with pappus dispersed over a wide range, while peripheral and intermediate achenes with no pappus usually dispersed near the mother plant. The different number of heteromorphic achenes could spread the risk of dispersal and settlement for this species. The larger number of central achenes increases chance for their random dispersal, and this is favorable for exploiting a larger geographical range for the population. The lower number of peripheral and intermediate achenes could decrease sibling competition due to dispersal near the mother plant. Formation of heteromorphic achenes is a form of bet hedging that could spread the risk of mortality in the extreme environment of the Junggar Desert. The peripheral and intermediate achenes presumably represent a “low-risk” strategy and the central achenes a “high-risk” strategy in one capitulum. Based on these strategies, H. szovitsii can spread the risk of survival and ensure its reproductive success.

Aims Figs and fig wasps are classical materials for research on plant-animal coevolution. There are both monoecious and dioecious figs. The evolutionary mechanism of Ficus has attracted many biologists. Most recently,Chen (2005) deduced that Ficus evolved from monoecious to dioecious, based on comparison of style distribution, pollinators’ ovipositor length, and reproduction success in monoecious and dioecious figs. Our objective was to test the duduction and further study Ficus evolution.
Methods We collected figs in the female floral phase and measured the length of styles and pollinators’ ovipositors in both monoecious figs and dioecious figs using dissecting microscopy. Figs in the male florets phase were also collected. We counted (i) seeds, galls, bladders, and unparasitized ovaries for monoecious figs, (ii) galls, bladders, and unparasitized ovaries for dioecious male figs, and (iii) seeds and unparasitized ovaries for female figs.
Important findings Ovipositor length was significantly longer, and the coefficient of variation (CV) of style length was higher in the two monoecious figs than in dioecious figs. Style length had unimodal distributions in the two monoecious figs, and their CVs were higher than pollinators’ ovipositor length CVs. The style length had biomodal distributions in the two dioecious fig species, and the CVs of style length were also higher than those of the ovipositor length. Monoecious figs were more effective in producing galls, based on the proportions of ovaries that pollinators’ ovipositors could reach, but dioecious figs were more effective in producing seeds. Therefore, the deduction ofChen (2005) is not completely correct, and additional research is needed to resolve the Ficus evolution question.

Aims The majority of damage by herbivores occurs during the leaf expansion period, yet the pattern of leaf damage and its influence are poorly known. Our objective is to measure damage throughout leaf expansion to understand the herbivory pattern and the defense strategy for young leaves of Castanopsis fargesii.
Methods We examined variation of leaf area and specific leaf weight (SLW) and measured herbivory frequency and herbivory rate dynamics twice a day during leaf expansion of 35 seedlings of C. fargesii in Tiantong National Forestry Park, eastern China.
Important findings Leaf herbivory frequency and herbivory rate on young leaves in the unfolded stage were significantly higher than in the folded stage (F_{1, 32}=8.97, p=0.005 4; F_{1, 32}=12.38, p=0.001 4). Herbivory in the folded stage consisted of a large amount of low proportion herbivory, while leaves in the folded stage mainly had high proportion herbivory. Leaves were intensively grazed at night (t=2.51, p=0.017), which accounted for about 85% of the total leaf herbivory. Young leaves of C. fargesii might follow different strategies in the two expansion stages.

Aims High soil calcium is an important factor influencing physiological characteristics of plants in karst areas. It causes harmful effects on plants by inhibition of photosynthesis, growth and phosphorus metabolism, thus limiting the number of species inhabiting karst areas. Our objective is to analyze plant calcium contents and different adaptation mechanisms to high calcium environment in karst areas to provide basic information on selection of plants useful for ecological restoration in karst areas.
Methods We collected a total of 45 dominant or common plant species and corresponding soil samples in four karst areas (Puding, Huajiang, Libo and Luodian) in Guizhou Province and measured total calcium contents in aboveground and underground plant parts along with the exchangeable calcium contents in soils. We analyzed the relationship between plant calcium and soil exchangeable calcium for 14 of the dominant shrubs and grasses by Pearson’s correlation and the calcium content difference by ANOVA.
Important findings Average calcium content of vegetation was very high. The exchangeable calcium content in soil was significantly related to calcium content of plant underground parts but not aboveground parts. There were significant differences among plant groups. Average calcium contents in aboveground parts of ferns were much lower than that of angiosperms. Calcium contents in aboveground parts were similar to that in underground parts in ferns and monocotyledons, but were much higher than that in underground parts in dicotyledons. In addition, we classified three categories of plant adaptation to high calcium environment in karst areas: calcium-indifferent, high-calcium and low-calcium. For calcium-indifferent species, the exchangeable calcium content in soil was the key factor influencing the calcium contents, and the calcium content in plant aboveground and underground parts had a significant positive correlation with exchangeable calcium content in soil. For high-calcium species, the calcium contents in aboveground parts were always high, even in soil with low exchangeable calcium content. In contrast, the calcium contents in aboveground parts of low-calcium species was always low, even in soil with high exchangeable calcium content.

Aims Our objective was to determine the impact of temperature and soil water content on soil respiration in Haloxylon ammodendron, Anabasis aphylla and Halostachys caspica desert communities.
Methods We measured soil respiration in the 2005 and 2006 growing seasons using an automated CO₂ efflux system (Li-Cor 8100). Air temperature (at 50 cm in height) and soil temperature (every 5 cm from 0 to 50 cm depth) were monitored at three points adjacent to the chamber using a digital thermometer at each site. Gravimetric soil moisture at 0-5, 5-15, 15-30, and 30-50 cm depths at three points was measured using the oven-drying method at 105 °C for 48 h. Water was added for artificial precipitation using plastic watering cans.
Important findings Soil respiration showed an asymmetric daytime pattern, with the minimum at 8:00 and the maximum at 12:00-14:00. The seasonal variation of soil respiration was characterized by a minimum in October and a maximum in June or July, which generally followed that of air temperature. The mean soil respiration rate in the growing season was 0.76, 0.52 and 0.46 μmol CO₂·m^-2·s^-1 in Haloxylon ammodendron, Anabasis aphylla and Halostachys caspica communities, respectively. Air temperature explained >35%, 51% and 65% of seasonal variations of soil respiration in Haloxylon ammodendron, Anabasis aphylla and Halostachys caspica communities, respectively. Q₁₀ values increased in Haloxylon ammodendron (1.35), Anabasis aphylla (1.41) and Halostachys caspica (1.52) communities, and R₁₀ decreased 0.45, 0.30 and 0.22 μmol CO₂·m^-2·s^-1 in each site, respectively. Significant power and quadratic relationships existed between normalized soil respiration and soil water content in the Haloxylon ammodendron and Anabasis aphylla communities, but not in the Halostachys caspica community. Two-dimensional equations based on temperature and soil water content explained most of temporal variations of soil respiration: 71%-93% in Haloxylon ammodendron, 79%-82% in Anabasis aphylla and 70%-80% in Halostachys caspica. Following artificial precipitation, the rate of soil respiration decreased, increased and then quickly decreased again, a pattern consistent with changes in soil temperature.

Aims Functional-structural plant modeling is concerned with the integration of architecture and resource allocation as aspects of plant function. It can depict the three-dimensional presentation of plants for use in analyzing individual tree growth and interactions between structural architecture and resource allocation in environments. Our objective was to parameterize and validate the functional-structural model GreenLab for young Pinus tabulaeformis to simulate its growth. Few studies have applied the GreenLab model to trees.
Methods Destructive sampling was done to collect detailed data including structure and biomass measurements from 9 young P. tabulaeformis trees. We used the functional-structural GreenLab model that has been successfully calibrated for several crops. To extend its application in tree growth analysis, we validated the basic hypotheses of the model such as constant allometry rules and source-sink relationships. Direct parameters were attained from the measurement data and hidden parameters of the model were calibrated using the generalized least squares method.
Important findings Simulations of P. tabulaeformis growth based on the fitted parameters were reasonably accurate. The coefficients of determination of linear regression equations between observations and predictions ranged from 0.78 to 0.91. The topological code system was set up to analyze tree topological structure for simulation. The calibrated parameters can be used to simulate and visualize 3D representation of pine trees. The methods for measuring tree topology and biomass and coding system can serve as a reference for the development of functional-structural models of coniferous trees.

Aims Harmful algal blooms caused by multiple toxic or harmful algal species have globally expanded and threaten marine sustainability, and interaction among bloom species is thought to play an important role in bloom development and elimination. Our objective is to study the interactions of two causative bloom-forming species of coastal China, Heterosigma akashiwo and Karenia mikimotoi, under controlled laboratory conditions.
Methods The experiments were carried out in mono- and co-culture. Results were analyzed with the software package Sigmaplot 8.0 and SPSS 13.0, and ANOVA and Duncan’s multiple range tests were used for data analysis.
Important findings Growth of both species at different initial cell densities in mono-culture was well predicted by a logistic model. Their environmental capacity (K) decreased steadily while the intrinsic rate of increase (r) increased with the initial cell density increment, and the time for entering exponential and stationary growth phases shortened simultaneously. Both K values of the microalgae in co-culture were inhibited as compared to mono-culture (p＜0.05), and their competition changed simultaneously with the ratio of their initial biomass. Under co-culture, K. mikimotoi became dominant when the initial biomass ratio of H. akashiwo (H): K. mikimotoi (K) was set at 1:4 and 1:16; however, H. akashiwo overcame K. mikimotoi when the ratio turned to H:K = 1:1. Therefore, initial biomass played an important role in microalgal inter-specific competition in co-culture. Allelopathy is a possible reason for the observed results.

Aims Our objective was to explore differences in genetic diversity of Kobresia pygmaea populations related to grazing intensity to help prevent grassland degradation and contribute to ecology, genetics and evolutionary ecology.
Methods We randomly selected tender leaves from 25 K. pygmaea individuals from four populations along a gradient of grazing intensity, used SRAP (Sequence-related amplified polymorphism) molecular markers, and examined the genetic diversity of the populations to determine the effect of grazing disturbance.
Important findings We used 20 primers and produced 448 clear bands, 376 (83.93%) of which were polymorphic. With increased grazing intensity, the percentage of polymorphic loci, Nei’s genetic diversity index and Shannon information index of the K. pygmaea populations decreased. Total genetic diversity (H_t) of the four populations under different grazing intensities was 0.276 6, genetic diversity within the four populations (H_s) was 0.243 6, genetic differentiation coefficient among populations (G_st) was 0.119 4 and gene flow (N_m^*) was 1.843 4. With increased grazing intensity, G_st increased and gene flow decreased. Therefore, grazing increased genetic the differentiation coefficient among populations, restrained gene transfer among populations and promoted population gene differentiation. The genetic distance of the four populations with different grazing intensities was small; however, with increased grazing intensity, genetic distance slowly increased and genetic consistency among populations decreased. The UPGMA dendrogram constructed by genetic distance arrayed the four populations in order of increasing grazing pressure.

Aims Our objective was to better understand physiological acclimation to varying light and soil water conditions by established seedlings of Mikania micrantha and Chromolaena odoratum to provide insight into the control of these invasive species.
Methods Seedlings were grown under optimum light and water conditions for plant stability and then treated by three light (full, medium and low irradiance) and three soil water (full, medium and low water content) conditions in field glasshouses. We measured superoxide dismutase (SOD) and catalase (CAT) activities and proline (Pro), glutathione (GSH) and malondialdehyde (MDA) contents in leaves and compared the two species.
Important findings Under full irradiance, the MDA content of both species in the low soil water treatment was always significantly higher than in the full soil water treatment (p＜0.01), indicating that drought stressed both species under high light. Both species developed mechanisms to scavenge the active oxygen. M. micrantha improved the SOD, CAT activities and the Pro and GSH contents, though the antioxidants could not sustain for a long time; C. odoratum showed similar trends in the measured antioxidants, except CAT was less responsive and Pro and GSH played important roles in acclimation to high light and drought. Relative to other irradiances, low light significantly reduced SOD and CAT activities and MDA contents in M. micrantha, but had less effect on those variables in C. odoratum, implying that low light reduced the antioxidants metabolism of both species, especially M. micrantha.

Aims High temperature is one of the major abiotic factors that limit plant growth and development in many regions of the world. Although plant thermo-tolerance has been extensively investigated, little attention has been paid to the effects of root temperature on thermo-stability of the photosynthetic apparatus. Our objective was to investigate the effects of variation in root temperature on photosynthetic apparatus and explore potential mechanisms.
Methods Under high air temperature (37 and 40 ℃), root temperatures of Prunus mira seedlings were increased gradually (variable root temperature) or kept at (25±2) ℃ (appropriate root temperature) throughout the treatment. We examined relative water content, H₂O₂ concentration, malondialdehyde (MDA) concentration, activity of antioxidant enzymes, cholorophyll a fluorescence and ABA content in leaves. The experimental design was completely randomized, and each treatment was replicated at least three times.
Important findings The combination of high air temperature and appropriate root temperature induced a decrease in activities of antioxidant enzymes and maximum quantum yield of PSII (F_v/F_m) with relatively high leaf relative water content (RWC). Hydrogen peroxide (H₂O₂) and MDA increased, indicating the photosynthetic apparatus was damaged by high temperature. The combination of high air temperature and gradually increasing root temperature reduced damage to the photosynthetic apparatus with significant improvement in antioxidant enzymes activities and leaf ABA content. Therefore, root temperature plays an important role in enhancing the thermo-stability of the photosynthetic apparatus. First, roots at appropriate temperature maintain high relative water content of leaves, but have damaged photosynthetic apparatus. Second, roots sensed the temperature stimulus and increased the leaf ABA accumulation when root temperature increased gradually, and high leaf ABA level prevented damage to the photosynthetic apparatus and enhanced heat-resistance.

Leaves of vascular plants in tropical and subtropical rain forests are frequently colonized by epiphylls. Most epiphylls are lichens and liverworts, but a few algae, cyan-bacteria and minute invertebrate animals also can occur. The composition of epiphyll communities is a sensitive indicator of seasonal changes of forest environments and microenvironment heterogeneity, and it can directly reflect habitat factors including moisture, temperature and illumination. Furthermore, epiphylls play significant roles in the formation and maintenance of biodiversity, as well as in the circulation of nutrients and water in ecosystems. In addition, they are indicators of forest responses to global changes. Epiphylls obtain nutrients independently. However, some experiments have provided evidence that substances can be exchanged between epiphylls and their host plants. Although epiphylls cover host leaf surface, whether the shading affects photosynthesis of the host plant is controversial. It has been hypothesized recently that leaves can photo-acclimate to the cover of the epiphyll community and photosynthesis of covered leaf areas can be compensated fully. The functions of epiphylls in nutrient and water circulation of forest ecosystems have attracted more attention in recent years. Nitrogen fixed by the epiphyll community provides 10%-25% of the nitrogen for the understory of tropical forest ecosystems. Epiphylls can also retain atmospheric moisture to alleviate drought in the dry season. There may be evolutionary balances between epiphyllous organisms and their host plants, and the relationships are likely influenced by multiple, poorly understood factors. More research is needed on relationships between epiphylls and their hosts.

Aims Although Phellodendron amurense is generally recognized as a shade-intolerant tree species, it has been reported to have some shade tolerance and be able to regenerate in both full sunshine and shade in New York, USA, where it is invasive. Our objective was to investigate shade tolerance of P. amurense.
Methods We planted 2-year-old P. amurense seedlings in two plantation plots, one with full natural light and the other with 15% of full natural light. After one year we observed the parameters of gas exchang, including maximum net photosynthetic rate (P_max), apparent quantum yield (AQY), dark respiration rate (R_d), light compensation point (LCP) and light use efficiency (LUE), using a Li-6400 (Li-Cor, USA). We also determined chlorophyll (Chl) contents per unit leaf area and per unit mass and specific leaf weight (SLW).
Important findings There were no significant differences (p>0.05) between sun and shade treatments for P_max, AQY and R_d. However, plants in the shade treatment had significantly lower LCP and SLW, but higher Chl content per unit mass and leaf area. These results indicated that P. amurense seedlings effectively used weak light by decreasing LCP and R_d, and enhanced the ability of capturing light by decreasing SLW and increasing leaf area and relative content of chlorophyll b, which made LUE increase in weak light condition. Therefore, P. amurense seedlings are shade tolerant.