黄土区果园和刺槐林生态系统土壤有机碳变化及影响因素

果园和刺槐是黄土区小流域综合治理中两种典型土地利用方式,对比分析二者土壤固碳功能变化有助于深入了解小流域综合治理条件下陆地生态系统土壤碳循环过程及其影响因素.在中国科学院长武黄土高原农业生态试验站,针对20世纪80年代以来综合治理的王东沟小流域,选取坡地上不同生长年限苹果园和刺槐林群落,测定表层(0~20 cm)土壤有机碳(SOC)、全氮(TN)以及根系生物量和地表凋落物含量,研究不同治理措施下SOC的变化特征及其影响因素.结果表明:1随生长年限的增加,苹果园中SOC、TN含量呈降低趋势,而刺槐林中呈增加趋势.与农地(对照)相比,3年、8年、12年、18年苹果园SOC、TN含量分别降低了3.26%、10.54%、18.08%、22.55%和-8.08%、-0.48%、4.97%、16.91%,12年、18年、25年刺槐林SOC、TN含量分别增加了5.31%、32.36%、44.13%和2.49%、15.75%、24.22%;23年、8年、12年、18年苹果园细根生物量,分别为农地(对照)的25.97%、66.23%、85.71%和96.10%,凋落物量均为0 g·m-2,而12年、18年、25年刺槐林细根生物量相较农地(对照),分别增加了23.53%、79.41%、157.35%,凋落物输入量分别为194、298、433g·(m2·a)-1;3有机物输入差异是导致果园和刺槐生态系统土壤固碳功能差异化的重要原因.

Changes of Soil Organic Carbon and Its Influencing Factors of Apple Orchards and Black Locusts in the Small Watershed of Loess Plateau, China

Orchard and black locust are two typical plants for comprehensive control in the small watershed of land uses in Loess area. The analysis of soil carbon sequestration function changes of growing two plants is important to gain a deep understanding of soil carbon cycle process and its influencing factors of terrestrial ecosystems under the condition of small watershed comprehensive control. The experiment was conducted in the Changwu State Key Agro-Ecological Station,Shanxi,China. SOC,TN,fine root biomass and litter amount were determined at different age apple orchards and black locusts on the slope land of Wangdonggou watershed to study the variation characteristics of soil organic carbon and its influencing factors under two measurements. The results showed that:1 SOC and TN contents in apple orchards significantly decreased with the increased age,whereas those in black locust showed an increased tendency with the age increased. Compared with the adjacent cropland,the SOC and TN contents in year 3, year 8, year 12 and year 18 apple orchards were decreased 3.26%,10.54%,18.08%,22.55% and -8.08%,-0.48%,4.97%,16.91%,respectively. However,SOC and TN contents increased 5.31%,32.36%,44.13% and 2.49%,15.75%,24.22%,in year 12, year 18 and year 25 black locusts,respectively. 2 The fine root biomass in year 3,year 8,year 12,and year 18 apple orchards were about 25.97%,66.23%,85.71% and 96.10% of the adjacent cropland,respectively; and the litter amounts were all 0 g ·m^-2. However,compared with adjacent cropland,The fine root biomass in year 12, year 18 and year 25 black locusts were increased 23.53%,79.41%,157.35%,respectively; and the litter input rates were 194, 298, 433 g ·(m² ·a)^-1,respectively. 3 The difference of organic matter input was the major factor which drove the variability of soil carbon sequestration function of apple orchard and black locust ecosystems.