Substrate age and tree islands influence carbon and nitrogen dynamics across a retrogressive semiarid chronosequence
Substrate age and tree islands influence carbon and nitrogen dynamics across a retrogressive semiarid chronosequence
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DOI：
10.1029/2007gb003062
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发表时间：
2008-03
影响因子：
5.2
通讯作者：
P. Selmants;S. Hart
中科院分区：
文献类型：
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作者：
P. Selmants;S. Hart
半干旱生态系统中碳（C）和氮（N）的长期动态仍然知之甚少。我们测量池和表层土壤C和N的通量，以及其他土壤性质，树冠下，并在树冠间的空间在四个网站，形成一个火山基质年龄梯度在半干旱的皮农-杜松林地的北方亚利桑那州，美国。粘粒含量和土壤持水能力随着基质年龄的增加而增加，但土壤有机碳和氮仅在75万年前增加，然后在最古老的（300万年）地点下降。土壤C和N通量的措施表现出类似的模式，总C和N库。随着基质年龄达到75万年，三种冠层类型之间的C和N库和通量变得更加均匀，但在最古老的地点，树木和冠层间微型地点之间的差异再次扩大。树叶和表层土壤的δ 15 N在基质年龄梯度上逐渐富集，与同位素分馏损失越来越占主导地位的N循环一致。我们的研究结果表明，半干旱和更潮湿的生态系统之间的生态系统发展的模式，并建议，土壤发育可能是一个重要的因素控制在半干旱生态系统的土壤资源的空间分布。这些数据应有助于统一和扩大目前的陆地生态系统发展理论。
The long‐term dynamics of carbon (C) and nitrogen (N) in semiarid ecosystems remain poorly understood. We measured pools and fluxes of surface soil C and N, as well as other soil properties, under tree canopies and in intercanopy spaces at four sites that form a volcanic substrate age gradient in semiarid piñon‐juniper woodlands of northern Arizona, United States. Clay content and soil water‐holding capacity increased consistently with substrate age, but both soil organic C and N increased only up to the 750,000 year site and then declined at the oldest (3,000,000 year) site. Measures of soil C and N flux displayed a similar pattern to total C and N pools. Pools and fluxes of C and N among the three canopy types became more homogeneous with substrate age up to the 750,000 year site, but disparity between tree and intercanopy microsites widened again at the oldest site. The δ15N of both tree leaves and surface soils became progressively more enriched across the substrate age gradient, consistent with a N cycle increasingly dominated by isotope fractionating losses. Our results point to consistencies in patterns of ecosystem development between semiarid and more humid ecosystems and suggest that pedogenic development may be an important factor controlling the spatial distribution of soil resources in semiarid ecosystems. These data should help both unify and broaden current theory of terrestrial ecosystem development.