三峡库区柏木林降雨的再分配及养分循环研究

REDISTRIBUTION OF RAINFALL AND NUTRIENT CYCLING IN CUPRESSUS FUNEBRIS FOREST IN THE THREE-GORGE REGION

以三峡库区柏木林为对象，定量研究了雨季（７月）林分中降雨的再分配及Ｎ、Ｐ两种养分元素的循环过程。研究结果表明：１）穿透雨量占总降雨量的７９．７０％，树干茎流占总降雨量的１．１７％，树冠截留量占总降雨量的１９．１３％，地表径流系数平均为１９８％；２）由于淋溶作用，实际进入林地的穿透雨和树干茎流中总Ｎ和总Ｐ的含量均升高了较大的幅度。降雨时总Ｎ和总Ｐ含量的相对平衡值分别为０４６１ ｍｇ／Ｌ和０．０７５ ｍｇ／Ｌ，淋溶系数为１．８６和２．９４，迁移系数为０．５７和０．２９；３）柏木林生态系统中，Ｎ的总贮量为３６． ００ ｘ１０３ｋｇ／ｈｍ２，Ｐ的总贮量为２．５１２ Ｘ １０３ｋｇ／ｈｍ２，其绝大部分（Ｎ为 ９９． ５％， Ｐ为 ９８． ８％）贮藏在土壤库中； ４）在有燃料输出的情况下，系统中的 Ｎ和 Ｐ循环效率分别为０．４３和０．４１。燃料的输出导致系统Ｎ和Ｐ循环效率降低，土壤中养分减少，从而导致系统养分的缺乏，生产力下降。

Based on the artificial Cupressus funebris forest in the Three-gorge region, a quantitative study on the redistribution of rainfall and nutrient cycling in rain season (July) were conducted. The through fall, the stemflow and the canopy interception accounted for 79. 70%, 1. 17 %, and 19. 13 % in the total precipitation, respectively. The average coefficient of the surface run - off was 1. 98 %. Because of the eluviation, the actual contents of total N and total P carried into the forestland by the throughfall and the stemflow had a great increase. In the rain process, the relative equilibrium levels of total N and total P were 0. 461 mg/L and 0. 075 mg/L, respectively, with leaching coefficients being at 1. 86 and 2. 94, respectively, and migration coefficients 0. 57 and 0. 29, respectively. In the Cupressus funebris forest ecosystem, the storage of N was 36. 00 X 103 kg/hm2 and P 2. 512 x 103 kg/hm2, with most of them stored in the soil. Under the condition of fuel output from the ecosystem, the cycling rate of N was 0. 43 and P 0. 41. The cycling rates of N and P decreased and the nutrient in the soil reduced as a result of fuel output. Consequently, the lackage of nutrients in the ecosystem was resulted and the lower productivity was therefore expected.