Shrub and tree planting plays an important role in combating desertification in China′s Mu Us Sandland, an ecotone sensitive to both the environmental fluctuations and anthropogenic disturbances. Recent years has witnessed the success of establishing Pinus tabulaeformis tree-belt in purpose of wind-breaking and sand-fixing in this area. However, the growth of the Pinus trees is prevailingly constrained by shortage of water. This restriction can be furthered by the persistence of varied substrate conditions that lead to the differences in water availability to plant. As a result, it’s urgently needed to analyze the physiological performance of this plant growing at the specific soil substrates in this area. This paper studied the water relations ,including transpiration, leaf water potential and drought resistance ,of the Pinus trees growing at both the typical dune and hard ridge (Cretaceous and Jurassic rocks)substrates. The main results obtained are in the following. (1)In Spring time, the Pinus trees growing at the hard ridge experienced more serious drought than their dune counterparts. This implies that much care is needed for the hard ridge grown rtees in Spring time; (2)The density of the Pinus tree-belt at the dune site should be paid special attention to because soil water holding capacity was poorer at this substrate; (3)Osmotic potential at initial plasmolysis obtained from the Pressure-Volume curves can be regarded as the threshold points at which leaf tissue begin to be injured by drought stress, and hence can be an indicator for requirement of watering.

The diurnal courses of the net photosynthesis(Pn)of the main tree species in the evergreen broad-leaved forest dominated by Quercus glauca under clear day in spring and summer showed significant midday decrease. The net photosynthesis of the evergreen species was the highest in autumn and the lowest when the plants were in the period of concentrate change of leaves. They still had Pn in winter. The photosynthetic rate of summer-green species was the highest in autumn too, but it began to defoliation in the end of October, when the environment was still suitable for photosynthesis. That caused the summed lower Pn in the year of summer-green species compared with the evergreen species, and their status would decrease in the development of the community. Between the two evergreen species, Quercus glauca can use the weaker light, that would ensure the dense crown having a higher Pn and keeping its dominated status in the community. Lithocarpus glaber Preferred to use stronger light. Their fewer leaves and the relative sparse crown could meet the require for light so as to get high photosynthesis and keeping its status of subdominant species. The diurnal course of Pn of the shrub and herb species in the community were the single peak type. Two shrub species, Loropethalum chinense and Lindera aggregata required relatively high light. The pteridophyta Woodwaria japonica had stronger shade tolerance and higher Pn, so it would become the stable accompany species in the community.

The diurnal course of transpiration rate generally showed a pattern of single peak and had a close relationship with Li (light intensity) in the species: P, hopeiensis, P. simonii,P, beijingensis and C. korshinskii. The four sorts of optimal models of transpiration rate consisted of the independent variable of Li; the independant variables of Li and T(temperature),the independent variables of Li and RH(relative humidity),and the independant variables of Li, T and RH, respectively. These four species had the transpiration rates (g·g-1LD·h-1) in the following order: C. korshinskii ( 0.9269 ± 0.2089 ) (mean ± 1 SD ) > P. simonii ( 0.7177 ± 0.2410 ) > P. hopeiensis (0.6256 ± 0.1609) >P. beijingensis (0.6007 ±0.2749); the net photosynthesis rate (mgCO2 ·g-1LD·h-1) was C. korshinskii(14.5949±4.6627)>P.simonii(13.4055±2.9994)>P. hopeiensis (13.2569 ±4.3531) > P. beijingensis (11.6989 ± 2.5884); and the transpiration efficiency (gDM·g-1H2O) was P. beijingensis (1.41% ± 0.42%)>P. hopeiensis(1.35%±0.36%)>P.simonii (1.26%±0.23%)>C. korshinskii (1.00%±0.27%).

To supply scientific and quantitative index to forest ecosystem management, the values of ecosystem services of major forests in China were evaluated and analyzed in this paper according to the forest inventory data from the third national investigation of forest resources(1984～1988) and the global average values of forest ecosystem services given by Costanza et al. (1997). The result indicates that the value of forest ecosystem services in China costs at least about $117.401 ×109 considering 14 types of ecosystem services annually. Among 14 types of ecosystem services, forests’ nutrient cycling which accounts for 40 per cent of the total value contributed the greatest, while their raw materials, including lumber, fuel and fodder, accounted only for 15 percent of the total value. It indicates that the ecological effect of forests was much more obvious.The total value of each forest ecosystem services had close relation with its net primary production (NPP):Ln(Va)= 108.21 (Tp)0.93 (R2= 0. 844). It may be helpful to simplify the procedure of estimating the value of ecosystem services, and provide a scientific and quantitative basis for rational protection and sustainable utilization of forest resources.

An experiment was carried out in the open-top chambers for elucidating the effect of CO2 enrichment on CH4emission from rice. Significant stimulation of CO2 enrichment on CH4 emission was found in the tillering, panicle initiation, booting, grain filling and maturity stages with the CH4 emission increments of 253%, 288%, 273% and 157% ,respectively. The highest flux, 1.91mgCH4·d-1·p-1,occurred in 106 days after transplanting. We propose that the increase in rice root biomass and root exudate might be the major reason for the stimulation of CH4 emission.

The paper deals with the influence of salinity on the changes in caloric values and ash contents of different parts of Kandelia candel seedlings cultivated for 170 days. The results indicate that the medium salinity had little influence on the caloric values and ash contents of hypocotyls other than those of root, stem and leaf. The caloric values of root, stem, and leaf increased with the salt stress at low salinity, and decreased with the salt stress at high salinity. The caloric values of root, stem and leaf reached the peak under the medium salinity of 15‰,20‰ and 25‰ ,respectively. The medium salinity of 15‰ was the upper limit for the normal living of K. candel The caloric value was a good physiological index for determining salt-resistance of species.