The regional characteristics of carbon storage and carbon dioxide fluxes of major Chinese forest ecosystems were studied from the points of internal biological cycle, based on published data regarding forest biomass, productivity, the organic carbon content of soil profile, stand and annual weight of the litter, soil respiration etc. The results are as follows: the average carbon density of Chinese forest ecosystem is 258.83 t·hm^-2, showing a generally increasing trend with increasing latitude; carbon density of the vegetation, soil and litter is 57.07 t·hm^-2,193.55 t·hm^-2, and 8.21 t·hm^-2, respectively; the characteristics of the carbon density of these three fractions (vegetation, soil, litter) were also analyzed; from the recent areal data provided by the Ministry of Forestry of China in 1989-1993 the total carbon storage of Chinese forests was estimated to be 281.16 ×10⁸ t, in which the vegetation, soil and litter were 62.00×10⁸ t, 210.23×10⁸ t,8.92×10⁸ t, making up 22.2% ,74.6%, 3.2%, respectively of the total, the carbon storage of deciduous broad-leaved forests, warmer temperate coniferous forests, evergreen/evergreen-deciduous broad-leaved forests, Picea-Abies forests, and Larix forests were the major carbon pool of the forest, making up 87% of the total; in China the net flux between the forest ecosystem and the atmosphere is 4.80×10⁸ t·a^-1 , and the forest ecosystem acts as a carbon sink when exchanged with the atmosphere, absorbing 48.7% of the carbon dioxide from burning of biomass, fossil fuel and human respiration (9.87×10⁸ t·a^-1). Generally, the carbon dioxide fixing capacity of the deciduous forest is higher than the coniferous forests, decreasing with increasing latitude.

Effective temperature, measured by the sugar-inversion method at 113 measurement points from June to September, 1993, was studied in relation to the indication value of plant communities to habitat temperature in the hilly landscape of the Kraichgau area in Germany. The results show : 1) the average indication value of the plant community to temperature is positively correlated with temperature as measured by the sugar-inversion method; 2) the average indication value of plant community is able to distinguish temperature differences between habitats on northern and southern exposure slopes, but its sharpness varies among three different methods of calculation; further comparison among these three methods reveals that the average indication value calculated in light of the quadrat data from each community is most effective for indicating the temperature difference between different exposures; 3) the average indication value calculated in light of the transect survey is not effective enough to indicate the temperature differences both between different exposures and among different slope positions. The reason for this ineffectiveness is probably either the narrowness of the transect or the heavy human impact on the vegetation along this transect.

The response of net photosynthetic rate (Pn) in new growth shoots of 18-year-old China fir (Cunninghamia lanceolata (Lamb.)Hook. ) to sudden exposure to high-light and lightflecks was measured and is discussed in this paper. Pn showed a S-shape response to sudden exposure following a period of low-light or darkness adaptation, and 10-15 minutes of photo induction was required for Pn to attain its maximum level. With increasing intensity of the high-light exposure a longer induction period was required. Longer exposure and/or lower levels of low-light also increased the induction period. Following the passage of the initial light fleck shoots showed a hysteretic response by maintaining an induction state during non-consecutive light-flecks unless lightflecks were separated by a long period of low light. The response of Pn to instantaneous light-flecks depended on induction status and light-fleck duration; fully inducted shoots could respond, more rapidly than low or non-inducted shoots; the raised photo induction associated with light-flecks of longer length could thus contribute to increased Ph. The slow decrease of Pn after light-flecks suggested that there existed postillumination CO2 fixation, and that in canopies with frequent instantaneous light-flecks, a great proportion of assimilation might be the result of postillumination CO2 fixation.

Abstract  Using rainfall erosion data from a woodland and a grassland runoff plot in Suide, Yanan and Ansai on the loess plateau, the effective cover rate of woodland and grassland for soil and water conservation in different rainfall and slope conditions was analyzed. The relationship between the critical effective cover rate (v) and a rainfall index (product of total rainfall amount and maximum 30 rain rainfall intensity represented by (Pi₃₀)) and slope steepness (s) is:

            woodland: v = -103.29 + 33.81log (Pi₃₀) + 75.38log(s)

            grassland: v = -103.20 + 34.62log(Pi₃₀) + 78.97log(s)

The results indicate that the effective cover rate of woodland and grassland increases with increasing rainfall and slope when soil and vegetation are relatively in the same condition, the conditional effect of rainfall and slope on effective cover rate weaken when the critical effective cover rate reaches a certain level. When other conditions remain equal, the suggested effective cover rate of grassland is higher than that of woodland in the same soil and water conservation effectiveness. Finally, through a rainfall frequency analysis, a critical effective cover rate of wood and grass land to fight different rainstorm is obtained.

Systematic analysis of the relation between wheat residual decomposition and soil biochemistry factors in the heavy frigid region of North East China found the following: changes through time in the rate of wheat residual decomposition showed a distinct seasonal trend with a single peak, in July (12.14×10-3g·g-1·d-1). 14 soil biochemistry factors were observed and these also changed in a distinct seasonal pattern. A step effect was an obvious feature of the residual decomposition and soil organic matter synthesis. The grey correlative effects of the 14 soil biology chemistry factors on the wheat residual decomposition were arranged as follows: x1(0.914)>x4(0.880)>x3(0.855)>x12(0.852)>x14(0.802)>x2(0.799)=x11(0.799)>x8(0.788)>x10(0.775)>x9(0.760)>x13(0.709)>x5(0.700)>x7(0.694)>x6(0.657) This allowed the delimitation of the GM(0,6) predictive model: y(k)＝13.5x1(k)+23.75x4(k)-15.0x3(k)-16.5x12(k)-0.5x14(k)+5.0x2(k)-1.6