三工河流域琵琶柴群落凋落物对土壤有机碳固定的影响

土壤有机碳是土壤碳库的重要组成部分,对生态系统生产力和全球碳循环有着重要作用。采用凋落物收集器和DIRT法(添加和去除凋落物法)研究三工河流域两处不同琵琶柴群落凋落物的产量、现存量、凋落物处理对土壤有机碳的影响。结果表明:群落1和群落2的凋落物产量季节变化趋势相同,均呈"N"型变化,在10月份达到最大值,7月或8月份达到次大值。凋落物现存量随季节均呈现"W"型变化,在10月份达到最大值,最大值分别为30.65 g/m~2和57.87 g/m~2。土壤有机碳随土壤深度的增加均逐渐降低,群落1和群落2分别下降了61.73%—62.39%和18.24%—25.84%。与对照处理相比,去除凋落物处理(NL)的群落1和群落2土壤有机碳分别降低了6.97%和18.38%;添加凋落物处理(DL)的土壤有机碳分别增加了19.64%和13.66%;去除凋落物处理(NL)的群落1和群落2土壤有机碳储量分别为1007.36 kg/hm~2和709.30 kg/hm~2,添加凋落物处理(DL)的土壤有机碳储量分别为1197.88 kg/hm~2和1010.78 kg/hm~2。双因素方差分析表明群落1的土层深度和三种处理对土壤有机碳的交互作用不显著,群落2的交互作用显著。回归分析显示:土壤水分、电导率、pH、容重和温度是导致两琵琶柴群落土壤有机碳不同的主要生态因子。相对较高的土壤pH和盐分含量抑制了凋落物的分解,导致凋落物现存量较高、土壤有机碳含量低;相对较高的土壤含水量和较小的容重,有利于土壤生物的活性和土壤有机碳的矿化,导致土壤有机碳含量降低。

Effects of litter on soil organic carbon fixation in Reaumuria soongorica communities in the Sangong River basin

Soil organic carbon is an important component of the soil carbon pool,and plays a key role in ecosystem productivity and the global carbon cycle. In this research,litter removal and detritus input treatment (DIRT) methods were used to study the litter productivity,litter amount,and effects of different litter treatments on the soil organic carbon in two Reaumuria soongarica communities in the Sangong River Basin. The results showed that the litter productivities of two communities had almost identical seasonal changes;they reached their second-maximum and maximum values in July (August) and October,and both showed "N" distributions. The litter amount also presented similar seasonal change trends;both showed "W" distributions,and reached their maximum values of 30.65 g/m² and 57.87 g/m² in October,respectively. The soil organic carbon content gradually reduced with soil depth;Community 1 and Community 2 decreased by 61.73%-62.39% and 18.24%-25.84%,respectively. The average soil organic carbon content of Community 1 and Community 2 was reduced by 6.97% and 18.38% by the litter removal treatment (no litter,NL),and increased by 19.64% and 13.66% by the litter treatment (double litter,DL),respectively. The soil organic carbon storage values of Community 1 and Community 2 were 1007.36 kg/hm² and 709.30 kg/hm² after NL treatment,and 1197.88 kg/hm² and 1010.78 kg/hm² after DL treatment,respectively. Two-way analysis of variance showed that the interaction of soil organic carbon between the soil depths and three litter treatments was significant in Community 2,but not Community 1. Regression analysis showed that soil properties were determinants of the differences in soil organic carbon between the two communities. The relatively high litter amount and low soil organic carbon content were attributed to the high soil pH and salt content, which inhibited litter decomposition. Otherwise,the relatively high soil water content and low soil bulk density promoted both soil organism activity and soil organic carbon mineralization,which led to the decrease in soil organic carbon content.