积雪变化对中国森林凋落物分解影响研究进展

Research progress in the effects of snow cover change on forest litter decomposition in China

森林凋落物的分解对于维持生态系统物质循环和养分平衡具有重要意义,并受到不同积雪厚度下冻融格局的影响。冻融期(包括冻结过程期、完全冻结期、融化过程期)是冻土区凋落物分解的重要时期,该时期分解的凋落物量约占全年分解总量的一半。积雪减少通常会导致土壤温度降低、冻融循环次数增加,进而影响凋落物分解。通过综述近10年来积雪变化对我国森林凋落物分解影响的研究成果发现,积雪厚度减少在冻融期通常会抑制凋落物质量损失、碳元素释放和纤维素降解,生长季则起到促进作用,从全年来看多数表现为抑制作用。因此,冻融作用造成凋落物的物理破坏,对其分解的促进作用主要发生在后续生长季。积雪厚度减少在冻融期通常抑制氮元素释放,生长季和全年则无明显规律;磷元素和木质素目前研究还存在很大差异。最后,进一步阐述了积雪变化对凋落物分解影响研究存在的问题及未来研究发展方向。

Forest litter decomposition plays an important role in maintaining the element cycle and nutrient balance of the ecosystem,which is affected by the freeze-thaw patterns under different levels of snow thickness.Freeze-thaw stage(i.e.freezing onset,deep freezing and thawing stage)is an important period of litter decomposition in permafrost zone,accounting for about a half of mass loss in the whole year.Reduced snow cover would decrease soil temperature and increase freeze-thaw cycles,which would influence litter decomposition.The paper reviewed the effects of snow cover on forest litter decomposition in the recent 10 years.Reduced snow cover would decrease litter mass loss,carbon element release and cellulose degradation during the freezethaw period and in the whole year,but increase during the growing season.Freeze-thaw action would result in litter physical fragmentation,and then accelerate litter decomposition in the following growing season.Reduced snow cover usually decreased nitrogen element release,but no clear trends were found in the growing season and whole year.There were some large differences in the results of phosphorus and lignin.Finally,the problems of snow cover effects on forest litter decomposition were discussed and the future research directions were prospected.