嘉陵江上游低山暴雨区3种不同植被类型氮循环研究

本文通过对嘉陵江上游低山暴雨区不同植被类型的初步研究。不同植被类型的氮库总储量分别为：6 787.27 kg.hm-2、7 115.39 kg.hm-2、6 951.06 kg.hm-2。其中不同植被类型中活体生物量分别为：136.43 kg.hm-2、210.40 kg.hm-2、169.66 kg.hm-2,凋落物层分别为：31.06 kg.hm-2、38.96 kg.hm-2、40.05 kg.hm-2,土壤（0-40cm）中分别为：6 619.73 kg.hm-2、6 866.03 kg.hm-2、6 741.35 kg.hm-2。不同植被类型土壤中的氮分别占总储量的97.53%、96.50%、96.98%,活体生物量分别占2.01%、2.96%、2.44%,而凋落物层分别仅占0.46%、0.55%、0.58%。结果表明,低山暴雨区3种不同植被类型的N主要分布在土壤中,而在活体生物量和凋落物层中只占很少的一部分。3种不同植被类型树干径流的氮含量分别为：0.44 kg.hm-2、0.553 kg.hm-2、0.851kg.hm-2,林分穿透雨氮含量分别为：12.649 kg.hm-2、12.551 kg.hm-2、13.291 kg.hm-2,地表径流氮的输出量分别为：0.55 kg.hm-2、0.55 kg.hm-2、1.27 kg.hm-2。不同植被类型氮的生物循环：湿地松林吸收量、存留量、归还量、循环系数分别为：37.561 kg.hm-2.a-1、6.497 kg.hm-2.a-1、31.064 kg.hm-2.a-1、82.703%,刺槐林吸收量、存留量、归还量、循环系数分别为：48.976 kg.hm-2.a-1、10.019 kg.hm-2.a-1、38.957 kg.hm-2.a-1、79.543%,混交林吸收量、存留量、归还量、循环系数分别为48.127 kg.hm-2.a-1、8.079 kg.hm-2.a-1、40.048kg.hm-2.a-1、83.213%。吸收量、存留量均是刺槐林〉混交林〉湿地松林,归还量是混交林〉刺槐林〉湿地松林。结果表明,3种植被类型处于良好的养分积累状态,有利于系统的稳定持续发展。

A Study of Nitrogen Cycle of Different Vegetation Types in Low-mountain and Rainstorm Sections in the Upper Reaches of the Jialing River

Studies were made of nitrogen cycle of different vegetation types in low-mountain and rainstorm sections in the upper reaches of the Jialing River.The nitrogen stocks in the three vegetation types were 6 787.27 kg·hm-2,7 115.39 kg·hm-2 and 6 951.06 kg·hm-2.Among them,the distribution of nitrogen stocks of the living biomass of the three vegetations was as follows：136.43 kg·hm-2,210.40 kg·hm-2,169.66 kg·hm-2;the distribution of nitrogen stock in the litter was as follows：31.06 kg·hm-2,38.96 kg·hm-2 and 40.05 kg·hm-2;the distribution of nitrogen stock in the soil as was follows：6 619.73 kg·hm-2,6 866.03 kg·hm-2 and 6 741.35 kg·hm-2.It was found that most of the nitrogen in the three vegetations was stored in the soil,but not in the living biomass.The nitrogen contents in stemflow in the three vegetations were 0.44 kg·hm-2,0.553 kg·hm-2 and 0.851 kg·hm-2.The nitrogen contents in throughfall were 12.649 kg·hm-2、12.551 kg·hm-2 and 13.291 kg·hm-2.The nitrogen input in stream flow was 0.55 kg·hm-2,0.55 kg·hm-2 and 1.27 kg·hm-2.The nitrogen biologic cycling of the three vegetations was：37.561 kg·hm-2·a-1 taken up by plants,6.497 kg·hm-2·a-1stored in living biomass,and 31.064 kg·hm-2·a-1 returned to soil in Pinus elliottill.48.976 kg·hm-2·a-1 were taken up by plants、10.019 kg·hm-2·a-1 were stored in living biomass,38.957 kg·hm-2·a-1 were retuned to soil in Robinia pseudoacacia.48.127 kg·hm-2·a-1 were taken up by plants,8.079 kg·hm-2·a-1 were stored in living biomass,40.048 kg·hm-2·a-1 were retuned to soil in mixed forest.Nitrogen absorption amount and stored amount were Robinia pseudoacacia forestmixed forestPinus elliottill forest.And the nitrogen return amount was mixed forestRobinia pseudoacacia forestPinus elliottill forest.Studies showed that the three vegetation types had the nitrogen conservation mechanism and remained in the nitrogen accumulation state.