模拟雪被变化对水曲柳和兴安落叶松凋落叶分解的影响

气候变化引起的雪被变化会深刻地影响森林凋落物的分解过程.本研究采用人工控雪处理(对照、增雪、除雪)模拟研究雪被变化对两种温带树种——水曲柳和兴安落叶松凋落叶分解动态的影响. 为期一年的分解试验表明: 不同控雪处理下水曲柳和落叶松的凋落叶年分解率的变化范围分别为51.3%～57.4%和21.7%～31.4%;两者的分解系数(k)变化范围分别为0.048～0.057和0.022～0.030,其中增雪处理的k值最大、除雪处理的k值最小.与对照相比,增雪处理下水曲柳凋落叶50%和95%分解的时间分别缩短了1.1月和4.2月,落叶松则分别缩短了3.7月和15.5月;相反,除雪处理下相应的分解时间分别延长了1.8月和6.4月(水曲柳)及5.0月和21.1月(落叶松).此外,凋落叶分解率与树种、雪深、分解时间、土壤温度等密切相关,但其主要影响因子随分解阶段而异,表现为雪被期主要受土壤温度影响,而随后的无雪期主要受凋落叶初始质量的影响.本研究突显了雪被变化对凋落叶分解有显著的瞬时效应和延迟效应.

Influence of snow depth changes on leaf litter decomposition of Fraxinus mandshurica and Larix gmelinii

Changes in snowpack induced by climate change can profoundly affect forest litter decomposition. A snow depth manipulation experiment with three treatments (i.e.,control,snow addition, and snow removal) was conducted to assess the effects of snow depth changes on leaf litter decomposition of two temperate tree species [Manchurian ash (Fraxinus mandshurica) and Dahurian larch (Larix gmelinii)]. The annual loss of the litter mass after one year decomposition varied between 51.3% and 57.4% for the ash and between 21.7% and 31.4% for the larch. The decomposition constants (k) ranged from 0.048 to 0.057 and from 0.022 to 0.030 for these two species respectively.The greatest k value occurred under the snow addition treatment, while the least occurred under the snow removal treatment.Snow addition treatment shortened the 50% and 95% decomposition time by 1.1 months and 4.2 months for the ash, respectively, and by 3.7 months and 15.5 months for the larch, respectively. The snow removal treatment lengthened those decomposition time by 1.8 months and 6.4 months for the ash,and by 5.0 months and 21.1 months for the larch, respectively. Litter decomposition rate was significantly correlated with tree species, snow depth, decomposition time, and soil temperature, but its major influencing factors varied with decomposition stage. Soil temperature and the initial litter quality were the major factors affecting decomposition rates during the snow covered and following snow free periods, respectively. Our findings highlight that changes in snow depth exert significantly instantaneous and prolonged effects on forest litter decomposition.