Litter decomposition and nutrient release as affected by soil nitrogen availability and litter quality in a semiarid grassland ecosystem
Litter decomposition and nutrient release as affected by soil nitrogen availability and litter quality in a semiarid grassland ecosystem
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DOI：
10.1007/s00442-009-1506-7
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发表时间：
2010-03-01
期刊：
影响因子：
2.7
通讯作者：
Han, Xingguo
中科院分区：
文献类型：
--
作者：
Liu, Ping;Huang, Jianhui;Han, Xingguo
氮的有效性是至关重要的凋落物分解，特别是在干旱和半干旱地区，氮是有限的。以克氏针茅（Stipa krylovii）和冷蒿（Artemisia frigida）为草地优势种，研究了内蒙古典型半干旱草原生态系统凋落物质量和土壤氮对凋落物分解的相对贡献。研究有四个不同的氮添加率（0，8，32，和64克N m（-2）年（-1）），凋落物样品分解在不同的立地条件下，凋落物类型。还研究了两个物种的凋落物混合效应。我们发现，N添加增加凋落物N浓度，从而提高凋落物分解，通过改善基质质量。然而，这种增加，被抵消的负面影响，增加土壤氮，从而减少影响增加土壤氮的有效性在原位凋落物分解。提高凋落物质量的正效应略大于增加土壤氮的负效应。我们进一步的分析表明，增加土壤氮对凋落物分解的负面影响可以部分解释为减少土壤微生物生物量和活性。分解是显着更快的凋落物的两个物种的混合物比凋落物的单一物种，但凋落物的分解率没有太大的差异，这两个物种之间，组成平衡，而不是针茅和蒿属之间的优势变化，是更关键的凋落物分解，因此在这个生态系统中的养分循环。随着土壤氮素含量的增加，针茅对土壤养分的吸收和利用逐渐由蒿向针茅转化，针茅的分解速率比蒿慢，养分留存率比蒿高，这可能使半干旱草原生态系统的养分利用趋于保守。
Nitrogen availability is critically important to litter decomposition, especially in arid and semiarid areas where N is limiting. We studied the relative contributions of litter quality and soil N to litter decomposition of two dominant grassland species, Stipa krylovii and Artemisia frigida, in a semiarid typical steppe ecosystem in Inner Mongolia, China. The study had four different rates of N addition (0, 8, 32, and 64 g N m(-2) year(-1)), and litter samples were decomposed under varying site conditions and by litter types. Litter-mixing effects of the two species were also examined. We found that N addition increased litter N concentration and thus enhanced litter decomposition by improving substrate quality. This increase, however, was offset by the negative effect of increased soil N, resulting in a diminished effect of increased soil N availability on in situ litter decomposition. The positive effects of improved litter quality slightly out-performed the negative effects of increased soil N. Our further analysis revealed that the negative effect of increasing soil N on litter decomposition could be partially explained by reduced soil microbial biomass and activity. Decomposition was significantly faster for litters of a two-species mixture than litters of the single species, but the rate of litter decomposition did not differ much between the two species, suggesting that compositional balance, rather than changes in the dominance between Stipa and Artemisia, is more critical for litter decomposition, hence nutrient cycling in this ecosystem. This semiarid steppe ecosystem may become more conservative in nutrient use with switching of dominance from Artemisia to Stipa with increasing soil N, because Stipa has a slower decomposition rate and a higher nutrient retention rate than Artemisia.