黄土丘陵区柠条林地养分状况及其循环规律

黄土丘陵区柠条林地养分状况及其循环规律刘增文李雅素（西北林学院，陕西省杨陵７１２１００）ＦｅｒｔｉｌｉｔｙａｎｄＥｌｅｍｅｎｔｓＢｉｏ－ＣｙｃｌｉｎｇｓｏｆｔｈｅＣａｒａｇａｎａＭｉｃｒｏｐｈｙｌａＬ．ＦｏｒｅｓｔｌａｎｄｉｎｔｈｅＲｏｌｉｎｇＬｏｅ...

Fertility and Elements Bio-Cyclings of the Caragana Microphylla L. Forestland in the Rolling Loess Region.

The results of the present study showed that Caragana microphylla L. could improve the soil fertility. The element contents of N,P,K in C.microphylla forestland were 50.47%,83.48% and 103.88% respectively, which were more than those of the bare slopeland. There was no obvious difference of fertility among the forestlands with different planting time ,but with increasing of the forest age after cutting, fertility of the forestland was improved slightly. In the plant of C.microphylla , Contents of the fertility elements in living leaves were higher than in roots and branches,trunks. The dead leaves had lower content of the fertility elements than the living leaves. The growth of C.microphylla needs more N than K and than P. It needs about 18.69kg N,1.59 kg P and 6.25kg K to produce 1000 kg dry material. Absorption ratio of elements by C.microphylla from the forestland were N(0.4240%) higher than P(0.0123%) and than K(0.0065%).However, the return ratio through bio-cycling were N(0.30) lawer than P(0.39) and than K(0.48).The results indicated that the N 2-fixation of nodule was the main cause that kept the forestland without shortage of N content under great growth absorption.