Niche and fitness concepts are applied in this study of the dynamics of water availability and growth characteristics under five separate restoration planting regimes on stable sand dunes in the Shapotou area. Field soil water data was used to parameterize a mathematical model that calculates the relative water fitness of two species—Artemisia ordosica Krasch. and Caragana korshinskii Kom—along a gradient of water availability. This model indicates that A. ordosica had the lowest water deficit in July and that its water fitness was higher in mono-species plantings than in mixture. The water fitness of C. korshinskii was lower in mono-specific stands than when mixed. These trends occurred despite two-fold variation in growth season precipitation. Of three single-species planting patterns the 2 × 2 gave the best results in terms of plant growth. Of the two mixed planting patterns, 2 lines of A. ordosica × 2 lines of C. korshinskii with one line blank after every four lines was best.

The potential effects of future rainfall change on hydraulic and growth characteristics of seedlings of Sabina vulgaris, a dominant evergreen shrub of the semi-arid Mu Us sandy desert were examined in a controlled experiment simulating rainfall change conducted at the Ordos Grassland Ecological Station. Water saturated deficit (WSD) and tissue density (TD) decreased with increasing of soil water significantly, while the water loss coefficient (k) increased. This indicates that drought-resistance and water-holding ability of seedlings decreases with increasing simulated rainfall. The simulated water gradient had no significant effects on the ratio of branch to stem area, while a significant influence on the ratios of leaf mass to stem area and leaf mass to branch area was found, suggesting that the potential effects of water supply on seedlings decreases with increasing water availability. Biomass allocation was also significantly influenced by the water gradient; In contrast both morphology and the canopy productivity index showed no significant response to the water gradient. Changes in biomass increment, plant height, and basal diameter with water gradient reflected the slow-growing attributes of the seedlings. The sensitivity of roots to water change was higher than that of leaves and stems. The below-ground biomass allocation increased with increasing of water availability, implying that the seedlings may adapt to water stress through more economical use of water resource in natural habitats.

The soil water regime in Populus euphratica forest was studied in the alluvial plain of Tarim River, Yingbaza section. Patterns varied according to the age of the forest stand: in young forest zones groundwater was 1-2 m deep and lightly salt (1-3 g·L-1). The zone is often flooded during typical high water stages and has a high content of soil water, it is suitable for the growth of Popular euphratica seedlings. In the mature forest zone, groundwater is 2.5-4 m deep but still slightly salt (1-3 g·L-1). As the zone is flooded only in especially wet years and the soil water content in the surface layer is low, the water condition significantly limits the growth of Populus euphratica seedlings. The depth of groundwater observed in these forests is in the reach of the roots of mature trees and the conditions are suitable for mature forest growth. In the degraded forest zone, groundwater depth was 5-10 m, exceeding the critical depth for typical growth of Populus euphratica and soil moisture supply is in seriously deficit, causing Populus euphratica stands to degrade and wither.

We recorded climatic factors and physical and chemical characteristics of vegetation in 5 experimental shelter-belt forest plantations in Dongdai, Jiangsu province. The variables recorded were: solar radiation, ground temperature, ground relative humidity and daily variation in these across different growing seasons, and transpiration, nutrient value and biomass of herbage. The effects of forest canopy closure on solar radiation can be divided into 3 stages: under both high and low canopy closure variation in closure has little effect on variation in radiation while under medium canopy closure variation in closure has a large effect. At the peak of the growing season temperature in the experimental plots had a mean value of 23.1±5.9˚ which is 24.3% and 62.4% higher, respectively, than the beginning and end of growing season. Relative humidity also peaks, at 91.6% ± 1.6%, 24.4% and 32.9% higher than the beginning and the end of growing season, respectively. Transpiration of Sorghum sudanense at the climax of growing season was 3660±489 g·dm-2·h-1, just 1.7% higher than at the end of growing season. The metabolic energy and fodder unit of Arthraxon pricnodes per unit area reached a peak of 4.88×103 kJ·m-2 and 3891 FU ·hm-2, 77.5% and 80.8% higher than the lowest value. The effect of temperature on dry biomass of Setaria faberii and S. sudanense in each growing season was not significant, nor was relative humidity. On the other hand, the effect of solar radiation on the biomass of S. faberii was significant (Y= –724.19+0.063L) at the beginning of growing season, and on that of S. sudanense in the end of growing season (Y= –1093.30+0.11 L). For the native grass S. faberii all 3 enviromental factors had a significant impact on biomass at the beginning of growing season: Y= –3859.39+25.35T+23.03RH+0.11L; but only relative humidity and solar radiation had a significant effect on biomass at the climax of the growing season: Y=1205.16+0.05L–14.84RH; there were no significant factors at the end of growing season. For the introduced grass S. sudanense, temperature and relative humidity had a significant effect on biomass at the beginning of growing season: Y=6186.48–69.38T–62.64RH; all 3 factors had a significant effect on the biomass at the climax of growing season: Y= –3777.95+11.61 T+16.36RH+0.15L; and solar radiation and relative humidity have a significant impact at the end of growing season: Y= –779.92+0.116L–5.59RH.

Vegetation of the Oryza rufipogon Reserve, in Chaling, Hunan Province was surveyed with 2 m ~ 2 m quadrats and a community horizontal structure map drawn. In total, ninety random sampling quadrats in nine plots under different ecological conditions were surveyed. Several basic descriptive statistical indices were chosen to characterize patch size and spatial distributions. The niche breadth and niche overlap of the ten dominant species were measured on indirect habitat gradients and niche ordination was calculated from the overlap matrix. The results showed that the species distribution was heterogeneous and that niche separation was found among the ten species. The ecological distributions of these species were determined by heterogeneous environmental factors, especially hydrological factors. Ten species occupied a continuum along a water availability gradient, which was divided into 3 groups based on niche ordination: Brasenia schreberi, Murdannia triquetra, Nelumbo nucifera, Eleocharis acutangula, Scirpus triangulatus, and Sagittaria trifolia were found in water deeper than 20 cm. O. rufipogon and Leersia hexandra occurred at a depth of 10 cm to 20 cm. Isachne globosa was found at a depth of less than 10 cm. The maintenance of the suitable habitat, especially the suitable water level, is essential for the conservation of O. rufipogon.

Reinforcement by tree roots is the most effective mechanical process effecting soil stability and slope protection in shelter-forests. In mountainous areas particularly, traction of lateral roots plays an important role in this regard. The importance of this effect rises positively with the roots’tensile strength. This study developed a mechanical model of the relationship between the tensile strength and the traction effect of roots. The model was tested in a Pinus-Cyclobalanopsis forest. The results show that the tensile strength of the Pinus and Cyclobalanopsis roots were 30-5 MPa and 40-10 MPa respectively, and increased negatively with root diameter. In the 0-60 cm layer, the density of lateral roots of the two tree species was relatively high and the roots are able to increase the tensile strength of the rooted soil by 6.85-12.41 kPa, through their traction effect. Though the strength of the pine’s roots and its role in increasing strength of the rooted soil are significant, the root strength of the Pinus is lower than that of Cyclobalanopsis and other broad leaved trees.

Grazing disturbance is one of nain factors affecting change in plant diversity of grassland communities.The results of this study of nine major grassland communities along the grazing disturbance gradient in the Northeast China Transect showed that the Shannon index was the highest in moderate grazing or heavy grazing stages, changing as follows: Moderate grazing-Heavy grazing > Heavy grazing-Moderate grazing > Light grazing > Over grazing. While species richness had a higher contribution to species diversity, compared with evenness, changes in evenness contributed most towards the rate of change in diversity than did changes in species richness. Life form diversity also manifested some obvious changes along the grazing disturbance gradient. The pattern of plant diversity of the steppe region in the Northeast China Transect was Meadow steppe > Typical steppe > Desert steppe > Alkaline meadow.

Changes in fatty acid composition of roots of Elymus nutans, Poa sphyondylodes, and Bromus sinensis growing in alpine area were investigated over late fall and early winter. The results indicated that there were marked changes in the fatty acid composition in this period. The content of saturated palmitic acid (16:0) decreased by 40% while the content of unsaturated linolenic acid (18:3) increased by 112%, resulting in an increase in IUFA (index of unsaturated fatty acid) melting level. Membrane fluidities were low at the freezing-melting stage, but higher in the freezing stage. Ca2+, Mn2+ ATPase activities of plasma membranes increased, but Mg2+ ATPase activities decreased. The results suggested that increase in unsaturated fatty acid content of roots may be a very important physiological response to cold acclimation, which is directly associated with changes in the properties of plasma membranes, in maintaining membrane fluidity and controlling the activities of membrane integrated enzymes.