干湿交替对科尔沁沙地人工林叶凋落物分解和养分释放的影响

在干旱/半干旱地区,土壤干湿交替现象非常明显.在全球气候变化背景下,预测未来科尔沁沙地的土壤干湿交替变化强度将进一步加剧.本研究采用室内原位土柱培养方法,模拟干湿交替对科尔沁沙地小叶杨和樟子松叶凋落物分解速率及养分释放的影响.试验设置3个处理:恒湿处理(CM)、轻度干湿交替处理(DW₁,10 d干燥+20 d湿润)和重度干湿交替处理(DW₂,20 d干燥+10 d湿润).整个培养试验共处理180 d,其中进行4次干湿交替循环处理,并在干湿交替处理结束后,将各处理置于相同土壤水分条件(60%田间持水量)延时培养60 d.结果表明: 小叶杨和樟子松叶凋落物分解及养分释放对干湿交替的响应一致.在干湿交替期间,DW₂处理显著抑制叶凋落物分解及叶凋落物C、木质素和总酚释放;与CM相比,DW₂处理叶凋落物质量、C、木质素和总酚残留率分别增加17.4%、23.8%、35.2%和32.7%,而干湿交替对叶凋落物N和P养分释放无显著影响.干湿交替处理结束和延时培养结束时,不同干湿处理叶凋落物分解及养分残留率的变化具有一致性.而延时培养期间DW₂处理凋落物分解速率、叶凋落物C和木质素释放加快,表明干湿交替对叶凋落物分解及养分释放具有短期延时效应.

Effects of drying-rewetting on leaf litter decomposition and nutrient releases in forest plantations in Horqin Sandy Land,China

Soil drying-rewetting is a common phenomenon in arid and semi-arid regions. Under the background of global climate change, it is predicted that the intensity of soil drying-rewetting cycle in Horqin Sandy Land will be further strengthened in the future. In this study, we conducted an in-situ soil column incubation experiment for 180 days to investigate the effects of soil drying-rewetting on leaf litter decomposition and nutrient releases of Populus simonii and Pinus sylvestris var. mongo-lica in Horqin Sandy Land. There were three treatments: Constantly moist treatment (CM, 60% water holding capacity during whole incubation period), mild drying-rewetting treatment (DW₁, gra-dual drought for 10 days plus 60% WHC for 20 days) and heavy drying-rewetting treatment (DW₂, gradual drought for 20 days plus 60% WHC for 10 days). To evaluate their delayed effects, leaf litter in all three treatments were incubated for 60 days under same and constant humid condition (60% WHC) after four cycles of soil drying-rewetting. The responses of litter decomposition to soil drying-rewetting cycles and nutrient releases of P. simonii and P. sylvestris var. mongolica were similar during the drying and rewetting period. Litter mass loss and the release of C, lignin and total phenol were decreased by 17.4%, 23.8%, 35.2% and 32.7% in DW₂ treatment compared with CM treatment. There was no significant difference in release of leaf litter N or P among the drying-rewetting treatments. There were consistent changes of litter mass loss and nutrient releases among the treatments at the end of drying-rewetting and delayed incubation period. However, litter decomposition rate and litter C and lignin release rates were increased in DW₂ treatment compared with CM treatment during the delayed incubation period, indicating a short-term delayed effect.