海岸带林草复合系统环境及其效应研究

在江苏东台海岸带防护林内设置5个林分密度小区，记录各小区不同生长季节的光照、地面温度和地面相对湿度及其日变化，测定牧草的蒸腾作用、营养价值及其生物量的变化，分析林草复合系统的环境特征及其生态效应，结果表明：林分郁闭度对光照强度变化的影响可分为3个阶段，低郁闭度时，郁闭度的变化对光照影响较小，中等郁闭度时影响最大，高郁闭度时影响又会减弱。生长季盛期，试区平均温度最高，为23.09±5.93℃，分别比初期和末期高24.3％和62.4％；此时平均相对湿度为91.61％±1.57％，分别高于初期24.4％和末期32.9％。生长季盛期苏丹草(Sorghum sudonense)的平均蒸腾强度为3659.82％±489.44g·dm-2·h-1，比末期高1.72％。在IV区茅叶荩草(Arthraxon pricnodes)单位面积的代谢能、饲料单位最高，分别为4.877×103kJ·m-2和3890.64FU·hm-2，比最低的Ⅰ区高77.54％和80.87％。不论是单个生长季的温度，还是几个生长季温度的组合，对于狗尾草(Setaria faberii)和苏丹草干重的影响都是不显著的，相对湿度也是如此。生长季初期的光照(L)对狗尾草生物量(Y)回归是显著的：Y= –724.19+0.063L；生长季末期的光照对苏丹草的生物量是显著的：Y= –1093.30+0.11 L。对于狗尾草，在生长季初期，试区内温度(T)、相对湿度(RH)和光照对其生物量的影响都是极显著的，其关系为：Y＝–3859.39+25.35T+23.03RH+0.11L；盛期时，只有相对湿度和光照的作用显著，关系为：Y＝1205.16+0.05L–14.84RH末期时，三因子中没有一个因子或因子的组合有显著作用。对于苏丹草，在生长季初期，温度和相对湿度的作用明显，其回归方程为：Y＝6186.48–69.38T–62.64RH；盛期时，温度、相对湿度和光照的作用都是显著的，其关系是：Y＝–3777.95+11.61 T+16.36RH+0.15L；而在末期，光照和相对湿度与苏丹草干重呈显著回归：Y＝–779.92+0.116L–5.59RH。

THE ENVIRONMENT AND IMPACTS OF A COMPOUND SILVO- PASTORAL SYSTEM IN A COASTAL REGION

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=－724.2 + 0.063L) at the beginning of growing season, and on that of S. sudanense in the end of growing season (Y=－1093 + 0.11L). For the native grass S. faberii, all 3 environmental factors had a significant impact on biomass at the beginning of growing season: Y=－3859 + 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= 6186－69.38T－62.64RH; all 3 factors had a significant effect on the biomass at the climax of growing season: Y=－3777.95+11.61T+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.