Our objective was to explore changes in soil respiration of three temperate forests in Mt. Dongling, Beijing over the last 20 years from the year of 1994-1995 to 2012-2015.

We re-investigated the permanent plots of three temperate forests (Betula platyphylla forest, Quercus wutaishanica forest and Pinus tabuliformis forest) which were established in 1992. We measured soil respiration for 3 years (2012-2015) using a LI-8100 Soil Respiration System. Continuous soil temperatures at 5 cm depth were measured at the same time. Annual soil respiration was accumulated using a relationship between soil respiration and soil temperature .

We found that soil respiration rates were significantly correlated with soil temperature at 5 cm depth and that these correlations differed remarkably among the three forests. Annual soil respiration in B. platyphylla forest was highest, with a 3-year average of (574 ± 21) g C·m^-2, followed by Q. wutaishanica forest ((455 ± 31) g C·m^-2) and P. tabuliformis forest ((414 ± 35) g C·m^-2). In the past 20 years, annual soil respiration in all these forests increased significantly: compared to 1994-1995, the average in 2012-2015 increased by 85%, 17% and 73% for B. platyphylla, Q. wutaishanica, and P. tabuliformis forests, respectively.

Study on the relationships between plant functional traits and soil water content is important for revealing potential impact of vegetation dynamics on soil water dynamics. The objective of this study was to understand the change of soil water content (W_s) through forest succession.

The study sites are located in Tiantong, Nanshan and Shuangfeng Mountains in eastern Zhejiang Province. We measured 10 functional traits for common plant species and W_s in forest plots representative of three successional stages of evergreen broadleaved forests. The Pearson correlation and the stepwise regression were conducted to determine the quantitative relationships between plant functional traits and W_s.

Tree height (H), crown area (CA) and leaf dry matter content (LDMC) were significantly higher for species at intermediate-and late-successional stages than for species at early-successional stage. In contrast, max net photosynthetic rate (P_max) and transpiration rate (T_r) of dominant species declined with forest succession. The W_s in the surface soil layer (0-20 cm) increased significantly, whereas W_s in the subsurface soil layer (20-40 cm) did not significantly change through forest succession. With respect to the surface soil layer, W_s was positively correlated with each of H, CA and LDMC, but negatively correlated with each of P_max and T_r. With respect to the subsurface soil layer, W_s positively correlated with CA only, and negatively correlated with each of P_max, stomatal conductance (Cond) and T_r. Variation in soil water content with forest succession could be explained mostly by H, CA, LDMC, P_max, Cond and T_r, and the ratio of crown depth to tree height (CD/TH) was mostly sensitive to the change of soil water content during forest succession.

Much attention has been paid for the relationship between species diversity (SD) and aboveground net primary productivity (ANPP). However, the effect of functional diversity (FD) on ANPP was more straightforward. Most researchers considered SD or FD as an independent variable to study the relationship between biodiversity and ANPP. In fact, the relationship may be affected by abiotic factors. Our objective was to study how different disturbance factors affect the relationship of FD-ANPP.

The experiment was conducted in the alpine Kobresia humilis meadow at Haibei Research Station of the Chinese Academy of Sciences with clipping (unclipping, stubbled 3 cm and 1 cm) and fertilizing (12.75 g·m^-2·a^-1 urea + 3.06 g·m^-2·a^-1 (NH₄)₂HPO₄) treatments from 2007 to 2013. General linear model univariate ANOVA, regression analysis and ANCOVA were used for studying the effects of clipping, fertilizing, year and their interaction on ANPP and FD and the change of relationship of FD-ANPP.

ANPP was enhanced by increasing clipping intensity and soil nutrient extremely significantly (p < 0.01). However, the effect extent was different in each year. ANPP presented a fluctuant downward trend year-to-year while FD increased along time. FD was increased by fertilizing significantly (p < 0.05), while the effect of clipping on FD was not significant (p > 0.05). Under the six kinds of treatment combinations of clipping and fertilizing, the relationship of FD-ANPP presented two patterns including linear positive correlation and no correlation mainly depending on clipping. No matter the community was fertilized or not, in the unclipped community, FD showed no correlation with ANPP (n = 90, p > 0.05). However, in the clipped community, clipping increased FD and ANPP in the same time, which facilitated them showing linear positive correlation. Fertilizing cannot affect the pattern of relationship of FD-ANPP, but the slope and intercept of equations of relationship were influenced by fertilizing and clipping. The results suggested that the relationship of FD-ANPP was influenced by clipping and fertilizing jointly, while clipping plays a leading role in changing their relationship patterns.

Dark septate endophytes (DSE) are commonly detected in plant roots in different ecosystems. However, so far our knowledge about the ecological significance of DSE in semiarid and arid lands is limited. The main objective of this study was to compare the colonization status and ecological distribution of DSE in Ammopiptanthus mongolicus and its associated plants in desert habitats.

In July 2013, soil and root samples of A. mongolicus and its associated plants were collected from three sites, including Yinchuan, Shapotou and Minqin located in northwest China. At each sampling site, samples were collected at five depth intervals, 0-10, 10-20, 20-30, 30-40 and 40-50 cm, respectively.

The roots of A. mongolicus and its associated plants were infected by DSE which could be characterized by typical septate hyphae and microsclerotia. Microsclerotia of A. mongolicus were compact lumps, while the associated plants had scattered microsclerotia. In the same site, microsclerotia colonization in A. mongolicus and its associated plants showed no significant difference, but hyphal colonization, colonization intensity and total colonization of A. mongolicus were much higher than that of its associated plants. In different sites, the colonization intensity and total colonization of DSE in A. mongolicus exhibited a pattern as Shapotou > Yinchuan > Minqin, and these indexes in associated plants were Yinchuan > Minqin > Shapotou. Plant species and soil layer had significant effects on the colonization and distribution of DSE as well as soil properties. The path coefficient and principal component analysis indicated that soil organic matter, total extractable glomalin, phosphatase and available K are the main influencing factors, which directly affected the colonization of DSE in desert environment, Northwest China.

Transpiration is one of important physiological activities for plants, which is regulated by many environmental variables. Our objectives were to understand the responses of sap flow density of Haloxylon ammodendron to environmental variables and simulate its diurnal change under different micrometeorological conditions.

Sap flow in stems of H. ammodendron was measured with stem heat balance method using commercial sap-flow gauges from May to October, 2014, in the oasis-desert ecotone, located in the middle range of Hexi Corridor, Northwestern China.

Sap flow velocity of H. ammodendron exhibited a positive relationship with stem diameter, but sap flow density (J_s) decreased with stem diameter. The first three axes of principal component analysis (PCA) explained 49%, 15%, 12% of variances in the environmental datasets, respectively, and vapour pressure deficit (VPD), photosynthetically active radiation (PAR), temperature in the first axes indicated the atmospheric evaporative demand. A sigmoid function could explain 86% of the variation in J_s in typical sunny days, while only 65% on rainy days. It was worth noting the simulated J_s using the established sigmoid function agreed well with the measurements (R² = 0.90) if the time lags of J_s to principle environmental variables were taken into consideration. Plots of 30-min J_s against PAR, VPD, and evaporative demand index (EDI) revealed a counter-clockwise hysteresis for PAR, but a clockwise hysteresis for VPD and EDI, it was possibly affected by water stress and time lags of sap flow density to principle environmental variables.

Our objective is to study the effect of elevation on the reproductive allocation and sexual allocation of Saussurea dzeurensis during the flowering season.

We used the field investigation method and dry mass method to evaluate morphological characteristics of S. dzeurensis at different elevations.

Elevation had a significant impact on the biomass and resource allocation of S. dzeurensis; reproductive allocation and male allocation were positively correlated with elevation, but vegetative allocation and female allocation were negatively correlated with elevation; there was a trade-off of resource allocation between capitulum number and mass, between reproductive allocation and vegetative allocation, and between male allocation and female allocation; When resources were limiting, the resource input of every structure of S. dzeurensis was balanced by increasing reproductive allocation and sexual allocation so that the plant can adapt to the stressful environment and have high rate of reproductive success.

In order to determine the adaptability of legumes as the interplanting crops in fruit yards, field and pot experimental treatments with full natural light and weak light (48% of full natural light) regimes were conducted in 2014 to test the shade tolerance and physiological mechanisms of four legume species.

The leaf photosynthetic characteristic parameters, photosynthetic pigments contents and the activities of ribulose-1,5-bisphosphate carboxylase (RuBPCase) were measured during the first bloom stage. The responses of growth to weak light were likewise studied.

The results showed that the maximum net photosynthetic rate, light saturation point, light compensation point, apparent quantum yield and dark respiration rate of the four legume species changed into those of shade-tolerant plants under the weak light stress. The weak light reduced the net photosynthetic rate, stomatal conductance, transpiration rate, water use efficiency and RuBPCase activity of the legumes. In contrast, the weak light increased intercellular CO₂ concentration significantly. Contents of chlorophyll (Chl) a and Chl b in leaves of Vigna cylindrica (VCS) and Vigna radiata (VR) increased significantly, while Chl a/b in the leaves decreased dramatically after shading. Other two species changed photosynthetic pigments contents after shading. The weak light changed the growth of the four legume species, such as reducing stem diameter and branching quantity, reducing root nodule and root-shoot ratio, decreasing dry matter yield and dry matter accumulation efficiency, debasing leaf area and leaf thickness, reducing leaf quantity and leaf area index. Crotalaria assamica (CA) can not bloom under the weak light stress. Flowers were not strong enough to seed for Senna occidentalis (SO) under the weak light. The weak light also changed reproductive growth of VCS and VR significantly, such as debasing flowers quantity and flowering time, as well as decreasing seed yield. In conclusion, according to the responses of photosynthesis and growth to weak light regime in the legumes, we concluded that the shade tolerance ranking of four legume species from high to low is as follows: VCS, VR, SO and CA. VCS and VR are suitable for orchard interplanting. However, SO and CA are not suitable for orchard interplanting.