Aims Our objectives were to reveal changes in plant functional groups and species diversity under three grassland using modes in typical steppe of Inner Mongolia, China.
Methods Three plots in similar habitats were selected from the Hulunbeier steppe area of the Hui River National Nature Reserve: an meadow plot (controlled utilization), pasture plot (moderate utilization) and public pasture plot (severe utilization). Plots were 250 m × 250 m and consisted of three sample belts separated by 20 m. Each sample belt had eight 1 m × 1 m sample plots.
Important findings There were differences in species composition and community characteristics of the functional groups. Shrubs and sub-shrubs combined were significantly different (p< 0.05) among the plots, with the highest value in meadow. Perennial grasses were significantly different (p< 0.05). Annual and biennial herbs combined had significant differences (p < 0.05), with the highest value in the public pasture. The public pasture also had the highest percentage of the xerophyte functional group (50%) and the lowest mesoxerophyte and mesophyte (19%), and differences were significant ( p< 0.05) among the plots. The biomass of shrubs and sub-shrubs were lower in all plots. The combined biomass of perennial grasses and forbs decreased with the increase in grassland use intensity among meadow, pasture and public pasture, while the combined biomass of annual and biennial herbs increased. With the increase in use intensity, the community structure and composition tended to become simplified and susceptible to change. Richness and diversity were lowest in the pasture and highest in meadow. Differences in evenness were not significant. The use of meadow contributed to improving the health of the grassland, but pasture and public pasture exhibited over-grazing phenomena. The public pasture had degraded significantly because of the uncertainty about property responsibility and ineffective management.

Aims River floodplain meadow is biologically highly productive, but excessive grazing has degraded most of it. Our objective was to analyze changes of vegetation in a Xilin River Basin (Inner Mongolia) wetland meadow to provide information for the restoration and management of degraded wetland.
Methods We compared fenced (non-grazed) and grazed sites within the wetland for vegetation and soil characteristics: plant community composition, aboveground biomass, plant height, internode length, leaf length and width of major species, plant community root biomass and distribution, soil moisture, soil bulk density, soil microbial biomass and soil carbon and nitrogen content.
Important findings Grazing affects plant dominant species, gradually replacing original wetland plants with more drought-resistant ones. It also significantly reduces the aboveground and belowground biomass. Plants in degraded wetland meadow are smaller, thus resulting in the decline in community productivity; Grazing also causes a decrease in soil moisture. In the low flood plain, soil moisture and root biomass both increase with increasing soil depth; however, in the high flood plain, soil moisture does not change with soil depth and is similar to that of the typical steppe. Soil bulk density increases as soil is compacted by animal grazing and trampling. In high and low floodplain wetlands, the changes of soil microbial biomass carbon and nitrogen between ungrazed and grazed sites are varied. In low floodplain wetlands, grazed areas have increased microbial biomass, while in high floodplain wetlands, grazed areas have significant less microbial biomass, carbon and nitrogen.

Aims Xylem embolism is a physiological response of plant species to adverse environmental factors, such as water deficit. Desert riparian forest plays an important role in the inland river basin of China. Our objectives were to clarify how xylem embolism of desert plants responds to different drought stress and to understand their acclimation mechanism to drought environment.
Methods Desert species, Populus euphratica, Tamarixspp.,Alhagi sparsifolia andKarelinia caspia were chosen to study the response of xylem hydraulic conductivity and embolism of the root and shoot to different drought stress in two riparian areas: Tikanlik, which is located in the lower reaches of the Tarim River, and Ulan Tug, which is located in the lower reaches of the Heihe River. We used a xylem embolism meter. We also examined the effects of soil moisture, groundwater depth and climatic factors in the two areas on the root and shoot xylem hydraulic conductivity and embolism of the desert plants at the same time.
Important findings Xylem hydraulic conductivities of the desert plants in Ulan Tug were significantly higher than those in Tikanlik. For example, the initial specific conductivity (K_s0) values in the root xylem of Tamarixspp.,P. euphratica, A. sparsifolia andK. caspiaincreased 11.97, 6.74, 7.10 and 3.73 times, respectively, and the shoot xylem K_s0 values increased 9.48, 3.65, 2.07 and 1.88 times, respectively. The fundamental reason for the different xylem hydraulic conductivities of the plants was the difference in drought stress produced by different groundwater depths in the two regions. The drought resistance of Tamarixspp.was the strongest, meaning the genus could exist in a broad soil moisture environment, but A. sparsifolia andK. caspia only exist in a narrow soil moisture environment because of their weak drought resistance, which might be related to root distribution. The major resistance to water transportation of desert plants was shoot xylem when it encountered moderate drought stress, but it was root xylem when the plant encountered severe drought stress. Desert plants adapt to moderate drought stress through limiting shoot xylem hydraulic conductivity to coordinate the plant growth, but it adapted to severe drought stress through sacrificing inferior shoots and enhancing xylem hydraulic conductivity of the other shoots.

Aims The Species Area Relationship (SAR) is a fundamental pattern in ecology. Recent analyses have often demonstrated substantial uncertainty in selecting the best SAR model for a data set. Our objective was to understand the effects of sample design on species-area relations, in order to suggest a more appropriate SAR model for the given plot data.
Methods A long-term 42 hm²forest plot was established in conifer and board-leaved mixed forest in Jiaohe, China. All trees with diameter at breast height (DBH) > 1 cm were tagged and their height, DBH and crown diameter recorded. We propose three SARs models (logarithmic function, power function and logistic function) to compare SARs constructed from nested design and random design. We use Akaike Information Criterion (AIC) to compare the quality fit of each SAR model given the data.
Important findings The way of constructing SARs influences the outcome. The random design showed significantly better goodness of fit of SARs model than the nested design. Among the three SAR models, Logistic function model from the random design was the best, suggesting it provided a reasonable description of the species-area relationship in the plot. This study demonstrates the significance of scale variance in species-area relationships; the effects of area on species richness are variable and can be scale dependent. However, because the species distribution patterns and spatial scale vary greatly, further work is needed to consider environmental effects and the community succession on different spatial scales.

Aims The study of reproductive allocation is important to understand the environmental factors that contribute to population differences and species evolution. Our objective is to examine variation in reproductive allocation among 30 populations representing three Saussurea species across an elevation gradient on China’s Qinghai- Tibetan Plateau.
Methods We used population means to evaluate sources of variation in reproductive allocation within species. In addition, we used the sample investigation method and dry weight to evaluate biomass.
Important findings Reproductive allocation is negatively correlated with mean plant size; however, this relationship is not statistically significant when the effect of elevation is controlled statistically. Among populations within species, reproductive allocation increases with elevation, and this relationship persists even when the effect of mean plant size is controlled statistically. Altitude is a main influence on reproductive allocation.

Aims Our objective is to provide a scientific basis for optimization of tobacco planting.
Methods First, we analyzed the ecological factors that impact tobacco’s cultivation and quality. Second, we applied ARCGIS spatial analysis to obtain elevation and slope factors. Third, we obtained the vegetation index, surface temperature, soil moisture and solar radiation factor based on conventional remote sensing models. Fourth, we used Kriging interpolation to encrypt the geochemical data. Then we applied AHP analysis to establish a comprehensive evaluation system for tobacco cultivation.
Important findings Several environmental factors have a major impact on tobacco distribution, growth and quality. These include light, temperature, soil type, rainfall, soil moisture, altitude, slope and heavy metal pollution. These factors are also essential for optimizing allocation of tobacco cultivation. The spatial distribution of tobacco cultivation in the experimental area needs to be optimized.

Aims With the development of quantitative remote sensing technology, multiple bi-directional reflectance distribution function (BRDF) models have been developed to describe reflectance of forest canopies. Our objective is to compare the DART, 4SCALE and MGEOSAIL models for greater understanding their proper use.
Methods We used the BRDF models to simulate reflectance of the scene with different canopy densities at various observation angles in red and near-infrared bands and compared the results to analyze model applicability and limitations.
Important findings The MGEOSAIL model is suitable to simulate the scene reflectance with low canopy density and large trees, and the hotspot is obvious. The DART and 4SCALE models are accurate and suitable to simulate the scene reflectance with various kinds of canopy density. Also, the scene reflectance simulated by 4SCALE is higher than DART’s simulated first-order scattering value, but lower than DART’s fifth-order scattering value. All three models show the “bowl” shape in the near-infrared band.

Aims Andromonoecy, the presence of both staminate and hermaphrodite flowers on the same individual, was observed in Soranthus meyeri, a common early spring ephemeral perennial in the Guerbantonggut Desert of Northwest China. The relationships between sex ratio (number of hermaphrodite flowers/total number of flowers) and plant size and the flowering pattern of both staminate and hermaphroditic flowers of this species were studied to determine size-dependent sex allocation and flowering pattern.
Methods The study was conducted from May to June in 2006-2008. Morphology, number and dry mass of both staminate and hermaphroditic flowers were determined. Position of the two types of flowers and their flowering pattern at the level of the flower, umbel and individual were recorded. Individual biomass was determined, and the relationship between number of staminate and of hermaphroditic flowers and plant size was analyzed.
Important findings The sex ratio within a population of S. meyeri was 0.69 ± 0.03, 0.62 ± 0.03 and 0.69 ± 0.02 in 2006, 2007 and 2008, respectively, and there were no significant differences among the years. This indicates that the sex ratio of this species is stable and possibly controlled by genetics. Staminate flowers produced less pollen, and their biomass was smaller than that of hermaphrodite flowers, suggesting that staminate flowers were less expensive to produce. Primary umbels produced more hermaphrodite flowers than secondary umbels, indicating that the primary umbels are capable of obtaining more resources from the mother plant and increase female fitness. Resources saved by not producing hermaphroditic flowers in secondary umbels could be reallocated to produce more staminate flowers, thus increasing floral display to attract more pollinators as well as enhancing pollen export and overall fitness. The sex ratio per plant was significantly, positively correlated with aboveground vegetative organ biomass, and large plants allocated more to the female function than small plants. Thus, female reproductive success is limited by availability of resources. Flowers in the primary umbel bloom first, followed by those in the secondary umbel five days later. All umbels of the same order flower simultaneously, and all flowers within an umbel open centripetally. Separation of male and female phases through protandry is complete both within hermaphrodite flowers and within umbels, thus avoiding interference between the male and female function and promoting xenogamy. However, there is an overlap of about one day between umbels of consecutive orders, which can provide conditions for geitonogamy.

Aims Alfalfa (Medicago sativa) is the most extensive perennial leguminous forage. In the semi-arid region, water is the most important limiting factor for alfalfa growth. Our objective was to study the effect of soil water content on physiological properties of alfalfa.
Methods Our field experiment consisted of four treatments: non-irrigation (W₀) and irrigated (75 mm each) once (W₁), twice (W₂) and three times (W₃) for each crop. We evaluated soil moisture, leaf chlorophyll fluorescence parameters, stomatal conductance (G_s), transpiration rate (T_r), and net photosynthetic rate (P_n).
Important findings The original light conversion efficiency (F_v/F_m), G_s, T_r, and P_n of alfalfa were significantly improved by increasing irrigation. Moreover, correlation analysis showed that the mean value of the day of F_v/F_m, G_s, T_r, and P_n had significantly positive relationships with the average soil water content of 0-280 cm depth. P_n had a significantly positive relationship with F_v/F_m × PAR (photosynthetically active radiation). Additional irrigation also changed the diurnal courses of leaf P_n. Photosynthesis of alfalfa under W₂ and W₃ treatments did not present the “midday depression”, and the diurnal courses were unimodal. Nevertheless, treatments W ₁ and W₀ exhibited an apparent “midday depression” phenomenon, and the diurnal variation was bimodal. There were different physiologically activities at different growth stages of alfalfa. P_n of alfalfa in the early flowering stage was obviously higher than in the regeneration stage, in contrast T_r was lower at the early flowering stage.

Aims Although the influences of waterlogging disturbance on the physiology and growth characteristics of plants have been reported for many angiosperms, few studies were carried out in dioecious plants. Our objective was to explore the differences between the sexes of a dioecious species,Populus cathayana, in sex-related growth and physiological responses to waterlogging.
Methods One-year-old male and female P. cathayana seedlings were grown in plastic pots in Nanchong, Sichuan Province, China and were subjected to two water regimes: control (common soil water content) and waterlogging (water level 4 cm above soil surface) for 40 days of growth. We investigated sexual differences in malondialdehyde (MDA) content, photosynthetic pigments, gas exchange characteristics, antioxidant enzyme and morphological indices at the end of the experiment.
Important findings The waterlogging treatment significantly increased MDA content and number of stems with adventitious roots under water, as well as decreased net photosynthetic rate (P_n), chlorophyll content, super-oxide dismutase (SOD) activity, plant height, basal diameter, total leaf area, specific leaf area (SLA), root biomass, leaf biomass, stem biomass, total biomass and root/shoot ratio (R/S). Moreover, the waterlogging treatment significantly increased MDA content but decreased SOD activity, P_n, carotenoids (Caro) content, chlorophyll a/b ratio, SLA, root biomass and R/S in female plants, and males had higher stomatal conductance (G_s), intercellular CO₂concentration (C_i), transpiration rate (T_r), more adventitious roots and greater plant height than females. The results indicated that morphological growth and physiological progress of the P. cathayanaseedlings were seriously inhibited by the waterlogging treatment. Males may possess greater waterlogging resistance than females with higher photosynthetic capacity and number of adventitious roots maintaining plant growth under waterlogging stress.

Leaf morphology is closely related to the specific environment and provides the most useful characteristics to understand plant response and adaptation strategy to environmental change. Leaf morphology plasticity is obviously related to the temporal and spatial variation of environmental variables, which are useful to plants to enhance their ability to survive. Consequently, for many years, studies on plant physiology, plant ecology and physiological ecology focused on leaf morphology. We establish a simple category of leaf morphology classification. Simultaneously, based on the principle of material and energy balances, we systematically review the relationships among environment, leaf morphology and energy balances (or material changes), and emphasize that leaf morphology responded or adapted to lower water availability and higher radiation (or temperature) in arid ecosystems. In conclusion, we submit and discuss existing problems in leaf morphology based on the weaknesses of previous studies.