冬小麦生境中土壤养分对凋落物碳氮释放的影响

Nutrient availability in habitats affects carbon and nitrogen releases of litter in winter wheat

土壤养分影响植物生长,进而影响凋落物质量和产量;凋落物质量和产量影响凋落物分解过程。基于一个生长实验和一个相同环境分解实验,研究了冬小麦(Triticum aestivum)生境中养分可利用性对凋落物碳(C)和氮(N)释放的影响。结果显示:(1)冬小麦凋落物产量、叶/根C:N比、C释放量和N释放量随土壤养分梯度呈单调变化;(2)土壤养分影响叶凋落物丢失率而不影响根凋落物丢失率;(3)初始叶/根C:N比与其C、N释放量之间存在负相关关系;(4)分解过程降低叶C:N比和根C:N比。结果表明:生境中土壤养分的提高可加速凋落物C、N归还,这反过来可能促进冬小麦生长,因此这种效应是正反馈;初始C:N比可预测凋落物C、N释放量。

Aims Our objective is to test whether C and N releases in winter wheat （Triticum aestivum） litter change monotonically or unimodally with soil nutrients in its habitats. Methods We conducted a growth experiment where winter wheat was subjected to 6-level nutrient regimes and a common garden decomposition experiment. We determined initial C：N ratios of live tissues, biomass loss of litters, C：N ratios of remaining litter, and the amounts of C and N releases. We analyzed correlations between initial C：N ratios and C/N release or between C：N ratios. All data were analyzed with SPSS 13.0 and R 2.9.1. Important findings Litterfall, initial leaf/root C：N ratios, C：N ratios of remaining litter, and C and N releases changed monotonically along a soil nutrient gradient. Soil nutrients had significant effects on biomass loss of leaves, but not of roots. There were negative correlations between initial leaf/root C：N ratios and C and N releases. Initial leaf/root C：N ratios were strongly and positively correlated with C：N ratios of remaining litter. These findings suggest that （1） increased soil nutrients surrounding winter wheat plants enhance C and N return in litter, thereby being beneficial to its growth, （2） C：N ratios indicate the potential amounts of C and N releases, and （3） decomposition processes decrease C：N ratios in remaining litter.