“非正常”凋落物对冰雪灾后南岭森林土壤有机碳的影响

Effects of abnormal litter input on forest soil organic carbon after ice-storm:A case of Nanling

2008年初,一场百年罕见的冰雪灾害袭击了我国南方地区,对南方19个省(区)的林区,相当中国森林面积的13%(1.86×107hm2)的森林植被遭受整体性、毁灭性破坏,导致的大量"非正常"凋落物必将对森林土壤碳循环产生深远影响。本研究以广东乐昌杨东山十二度水省级自然保护区不同海拔梯度上受灾的常绿阔叶混交林3种森林群落为研究对象,采用去除冰雪灾害导致的"非正常"凋落物与受损林地进行对照试验,对冰雪灾害所导致"非正常"凋落物对土壤碳的影响进行了研究。研究结果表明:灾后3种森林群落中不同深度土壤的有机碳质量分数和储量持续增加,同一深度土壤有机碳质量分数和碳储量在不同年份之间差异显著。直至2011年"非正常"凋落物分解完毕时,10～50 cm的土壤有机碳质量分数与上一年相比有减少趋势;0～10 cm的土壤有机碳质量分数稍比2010年高,但变化差异不显著(p=0.36),说明在"非正常"凋落物分解结束后土壤有机碳质量分数有减小的趋势,致使土壤碳储量下降。去除"非正常"凋落物样地与对照样地相比,各土壤深度的土壤有机碳质量分数明显下降,年平均下降百分比例变化范围为12.14%～55.34%,0～10 cm和10～30 cm土壤的有机碳质量分数下降变化波动幅度要比30～50 cm大;不同深度土壤有机碳质量分数与凋落物有机碳失质量间具有显著的线性相关性。可见,冰雪灾害导致的"非正常"凋落物对土壤有机碳质量分数和储量都有十分显著的影响,"非正常"凋落物的分解输入能显著提高土壤有机碳质量分数和储量。

A greatest extreme ice-snow disaster swept across the most areas of southern China in early 2008. The snow, ice and sleet caused severe forest losses and destroyed 1.86×107 hm2 of forests, or nearly 13%of the China＇s forests, in 19 provinces of China. The damaged area was scattered by broken branches, tree trunks and leaves. The abnormal litter was equivalent to the sum of several years normal litter sum. And it wills strong and generally short-term changes in turnover of SOC and soil carbon stock induced by organic substrates added to the soil. Abnormal litter exclusion experiment has been established in an evergreen and deciduous broadleaved mixed forest with three forest community types selected along different elevation, in Yangdongshan Shierdushui Natural Reserve, Guangdong province. The concentration of soil organic carbon and carbon stock were measured every quarter, Several key results were given as follows： The different depths of soil organic carbon concentration and soil carbon stock were continued to increase in destroyed forest communities until abnormal litter completive decomposition in 2011, the soil depth 10-50 cm of soil organic carbon concentration has decline trend. The soil depth 0~10cm of soil organic carbon concentration is higher in 2011 than 2010, but no significant difference （p=0.36）. This indicates that soil organic carbon concentration and soil carbon stock would decline after abnormal litter completely decomposed. Compared with the control plots,soil organic carbon content decreased significantly in abnormal litter exclusion plot, decline ranged from 12.14%to 55.34%. And the soil organic carbon concentration in depth 0~30 cm declined changed more than the depth 30-50 cm. Soil organic carbon concentration has a significant linear correlation with litter carbon mass loss. Obviously, the forest soil organic carbon concentration and soil carbon stock were significantly impacted by abnormal litter which destroyed by ice storm. And the abnormal litter can increase the soil organic carbon concentration and soil carbon stock during decomposition and input.