Gordonia acumenata is one of the species dominating the subtropical evergreen broad-leaved forests in the southwest China. It is a pioneer climax species that has light-demanding adults and shade-tolerant seedlings.Its curves of diurnal variation of Pn in the sunny days of spring, summer and autumn have two peaks, one in the morning and the other in the afternoon, while in the winter, only one peak occurs at about 14:00 o’clock, Beijing time.Gordonia acumenata is characterized by high saturated net photosynthetic rate and low dark respiration, therefore, its adults are light-demanding, while its seedlings are shade-tolerant. The transpiration rates of its seedlings are greatly influenced by air temperature, leaf temperature, light intensity, relative humidity and leaf water content. Its photosynthetic rate can be significantly decreased by drought-stress, accompanied with this is an increased root/shoot ratio of the seedlings. This might be a strategy for Gordonia acumenata to be adapted to drought-stress.The nutrient content in different organs of Gordonia acumenata varies with season.

The salty meadow community of Hutubi, Xinjiang was analyzed by DCA, CCA and DCCA. The environment factors include level of underground water, depth of the clay layer, thickness of clay layer, pH value of underground water and mineral contents of underground water. The spatial coordinate matrix was established in order to partition out the effect of the spatial pattern to vegetation variation. The results show that the level of underground water and the pH value of the underground water are two main factors affecting the vegetation variation; the effect of spatial pattern to vegetation variation is larger than that of environmental factors to it.

Ordination is one of the most popular multivariate analysis methods used in vegetation research. However, most of the commonly used techniques involved in this aspect are concerned with linear data set that is difficult to find in the ecological world. In this paper, non-metric multidimensional scaling,a non-linear ordination technique put forward in Shepard and Kruskal, is introduced and its algorithm is programmed in the C++ computer language as program NMMDS, and it is included in the computer software Gingko V1.O used for structural analysis of vegetation. An example with the classification of tropical montane forest in Bawangling Nature Reserve, Hainan island, is presented. Also other multivariate analysis methods, such as principal components analysis, cluster analysis, are also used for comparison, The result shows that non-metric multidimensional scaling is suitable for higher species richness community classification, and much better than principal components analysis. With this, two sub-vegetation types in Bawangling montane forest have been classified. The tropical montane rain forest is represented by Dacrydium pierrei +Syzygium araiocladum community, while the tropical montane evergreen forest is represented by Sycopsis tutcheri +Syzygium araiocladum community. Also five associations among them are recognized.

The effects of the main climatical factors, including light, air temperature and relative humidity, on the photosynthesis of corn (Zea mays) in a shelterbelt network ecofield in the Song-Nen Plain, Northeast China were studied. The results showed that, during the entire season, the photosynthetic rate of corn was positively correlated with air temperature and light intensity and that the diurnal photosynthetic yield was positively correlated with air temperature and relative humidity. There existed an obvious midday depression as reflected in the diurnal curves of the photosynthetic rate of the corn in the west and east sides near the tree belts in the shelterbelt network. This phenomenon was hardly detectable in the corn growing in the center of the tree belt. Correspondingly, the corn plants growing in the central position showed higher photosynthetic yield than those growing in both sides. Through a synthetic analysis, we found that low air humidity was the primary factor causing the midday depression of photosynthesis of the corn plants in our study site, and air temperature and humidity were the main climatic factors limiting the photosynthesis of corn in the Song-Nen Plain, with air temperature being the most critical one. The shelterbelt network could increase the air temperature and humidity in the belt, thus increasing the photosynthetic yield of corn.

The storage of viable seeds and the species diversity in the soil of six salinealkali communities dominated by one species in the alkalized meadow in the Song-Nen Plain of China are comparatively analyzed in this paper. The common feature of the three communities dominated by Chloris virgata, Sueda corniculata, and S. heterotera was that they had large seed banks, of which the majority was composed of the dominant species, and had lower species diversity index. The transitional communities dominated by Puccinellia tenuiflora and Aeluropus littoralis var. sinensis, respectively, showed medium seed bank and species diversity. The dominant species in the seed banks were the same as the aboveground dominant species in these two communities. The Aneurolepidium chinense community differed from other communities of differentiating successional stages, in that it had the smallest seed bank, and highest species diversity.

A series of techniques including the analysis of variance, X2-test, Ochiai, Dice and Jaccard indices were used based upon a 2×2 contingency table to determine the interspecific association of the 13 dominant species in a subtropical Castanopsis fargesii forest in the Jinyun Mountain of China. We expressed the results in the forms of semi-matrix, complete-matrix and constellation figures. Our results indicate that the interspecific association of the dominant species in the subtropical Castanopsis fargesii can be adequately interpreted by using the techniques mentioned above. To be specific, the analysis of variance can be used to explain the overall association of all species; the X2-test can be used to describe the statistical significance and the property of the interspecific association; and the Ochiai, Dice and Jaccard indices can be employed to show to what degree a pair of species is associated. The result shows that the interspecific association is very complicated. The relationship between Castanopsis fargesii and Elaeocarpus decipiens is significantly positive. Castanopsis fargesii is significantly negatively related with Gordonia acuminata or Castanopsis carlesii var. spinulosa. The probability of the presence of a specific accompanying species will be high if all the constituent species in a community are closely evolutionarily related, have similar environmental requirements, and respond to the environmental factors with a similar manner. However, the species association properties can not be determined based on the above analysis.

This paper concerns the analyses of niche breadths of and overlaps between several plant species in 3 Kobresia communities in the Haibei Research Station using the formula described by Levins and Pianka. Our results show that the dominant species in the three Kobresia communities have greater niche breaths than their companion species. Kobresia pygmaea have niche breadths of 0.918, 0.896 and 0.910 on the gradients of soil water potential, incident light intensity and slope aspect, respectively. K. humilis and K. tibetica have niche breadths of 0.875 and 0.866, respectively, on the soil water potential gradient. The niche Overlaps are higher between the species that have greater niche breadths than between those that have relatively narrower niche breadths. The niche overlaps show a decreasing trend among congeneric species that have similar biological and ecological characteristics. The niche overlaps between K pygmaea and K. humilis are 0.671, 0.719 and 0.686 on the gradients of soil water potential, incident light intensity and slope aspect, respectively. Our results also show that the niche overlaps between some weeds and high-quality grasses are rather high. This might have been attributable to the suppression of high-quality grasses due to long-term overgrazing and habitat degradation.

Grasslands dominated by Leymus chinensis in the west part of the northeast China and the eastern Inner Mongolia are the main natural pasture for grazing and hay production, and, therefore they are highly economically valuable. However, the degradation of these grassland ecosystem are very severe, mainly due to overgrazing.In this paper, we will use mathematical’models to show the change of the relative dominance of plant populations in the retrogressive succession series. In lightly and moderately grazed grasslands, Leymus chinensis is the dominance. Its relative dominance changes with increasing grazing intensity, and this change can be described by an equation, D=124.2e-0.35T2. In the entire succession series, the changes of the relative dominance of Carex duricscula and Cleistogenes squarrosa can be explained using models of D=2.13T3.3 e-0.15T2 (for C. duricscula) and D=1.77T3.7e-0.29T2 (for C. squarrosa). The relative dominance of Suaeda corniculata and Chloris virgata increases as the grassland degrades. Their relative dominance changes can be elucidated by the following models, D =0.11e1.3T (for S. corniculata) and D=0.38e10.94T (for C. virgata), respectively. Our results indicate that the shift of dominant species is very conspicuous during the retrogressive succession of grassland communities.

Hutubi Cow Breeding Farm is localed in the border of the alluvial fan and the paleo-alluvial plain of the northern slope of Tianshan Mountain. The zonal grassland type in this region is desert and the interzonal grassland type is low land meadow. The formation and distribution of grassland types are mainly controlled by topography, ground water and soil salinity.Using methods of TWINSPAN and polythetic hierarchical agglomerative classification, the grassland types are divided into 16 types and their hierarchical classification system is formed. The ecological gradient in this region can be given by DCA ordination and the interpretation of its quantitative environment can aslo be given after multivariate regression analysis. The result shows that the grassland types and their distribution are strongly correlated with soil moisture, soil salinity and soil texture.

Cunninghamia lanceolata trees were mixed with Schima wallichii, Schima superba and Michelia macclurei, respectively, to examine the effect of mixing type (tree species composition) and mixing mode (species ratio) on soil fertility in the Yunyong Forest Station of Gaoming County, Guangdong Province. These forests were investigated for 6 consecutive years after planting. The results showed that interspecific competition started to appear after the trees were planted for three years. Twig-trimming, top-pruning, and selective lopping, at least once or twice before the trees were 6 years old, were required to regulate the interspecific relationship, hence weakening the competition between species. In comparison with the pure forest stands, the mixed forests removed more nutrients from the soil, as indicated by a decline in the concentrations of major nutrient elements (N, P, K) in the top 30 cm soil, and had higher biomass and productivity. After 6 years, the litterfall and nutrients in the litter began to increase. Moreover, the mixed forests had higher soil moisture content, and higher total and available N, P, K concentrations in the top soil (0--10cm) than the pure stands. We recommend that the mixing ratio between Cunninghamia lanceolata and broad-leaved tree species be increased from 3:1 to 4:1 or 5:1.

Exposed to high concentrations of Na2SO4(1% and 2%),the permeability of plasma membrane and membrane-lipid peoxidation of Seriphidium schrenkianum, Artemisia ratifolia, Festuca arundinacea and Dactylis glomerata were increased. But the increases in the permeability of plasma membrane and the membrane-lipid peroxidation were more prominent in salt-resistant species, Seriphidium schrenkianum and Festuca arundinacea, than the salt-sensitive species, Artemisia ratifolia and Dactylis glomerata. The activities of the superoxide dismutase (SOD) and catalase (CAT) in the graminaceous family (F. arundinacea and D. glomerata) increased with increasing concentration of Na2SO4, while those in the composite family (S. schrenkianum and A. ratifolia) decreased. In the graminaceous family, the rate of increase of SOD and CAT activities in the salt-resistant grass (F. arundinacea)was higher than that in the salt-sensitive grass (D. glomerata),while in the composite family, the rate of decrease of SOD and CAT activities was lower in the salt-resistant grass (S. schrenkianum) than that in the salt-sensitive species (A. ratifolia). Within the same family, the relative contents of carotene in the salt-resistant grasses were higher than those in the salt-sensitive grasses.