高寒杂草类草甸牧压梯度下植被碳密度季节动态及分配特征

摘要

比较分析了祁连山北坡高寒杂草类草甸夏季牧场牧压梯度下植被生物量季节动态及净初级生产碳量、现存碳量和地上地下碳量的分配关系.结果表明,牧压梯度下:1.地上生物量有一定的季节变化,但随放牧强度的增加季节变化幅度降低；枯落物量从生长期开始逐渐下降,生长末期有所增加,其中重牧和中牧条件下随时间进程比轻牧和封育措施下的减少量明显；地下生物量有不甚明显的季节变化；半腐殖质层生物量从生长季初期到放牧中期变化平稳,7月下旬开始有所下降,说明良好的水热条件影响下半腐殖质层生物量归还土壤碳的能力增大.2.净初级生产碳量大小依次是轻牧、中牧、重牧和封育,表明适当放牧对植被净初级生产碳量的提高有利,从其地下分配来看,封育所占比例小于80％,轻牧、重牧、中牧在80％以上.9月底测定结果表明,植被现存总碳量随放牧强度的降低而增大,轻牧和封育条件下植被的储碳能力强,利于土壤固碳能力的提高.%Seasonal dynamics of vegetation biomass,net primary carbon production,current carbon content,and the ratio of above and below ground carbon content of the summer alpine weeds meadow pasture lying in the north slope of Qilian Mountain under different grazing intensity were analyzed.The results showed that:(1) there was an obvious seasonal variation of the aboveground biomass,but the amplitude of variation was lower with the increase of grazing intensity ; litter began to decline from the beginning of the growing season and rise a little in the late growing season,in which the decline in the heavy grazing(HG) and moderate grazing(MG) was more evident than in the light grazing(LG) and no grazing(NG) ; the seasonal variation of below-ground biomass was not obvious; biomass in the humus layer varied smoothly from the beginning of the growing season to middle stage and begin to decline in late July indicating that the biomass in the humus layer returned to the soil well in the favorable water and heat conditions.(2) net primary carbon production had the order of LG ＞ MG ＞ HG ＞ NG,showing that appropriate grazing was beneficial to improve the net primary carbon production; its distribution in the below ground was less than 80 ％ in NG,while it was more than 80％ in LG,HG and MG.The investigation in the late September showed that the current total carbon content in vegetation increased with the decrease of the grazing intensity.The capacity of vegetation carbon storage under LG and NG was large and it was conducive to improve the carbon sequestration in soil.