Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment
Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment
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DOI：
10.1038/nature05900
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发表时间：
2007-06-21
期刊：
影响因子：
64.8
通讯作者：
Martinelli, Luiz A.
中科院分区：
文献类型：
--
作者：
Davidson, Eric A.;de Carvalho, Claudio J. Reis;Martinelli, Luiz A.
磷（P）通常被认为是生长在高度风化土壤上的成熟热带低地森林生产力的最常见限制性营养素（1-5）。人们通常认为，磷限制也适用于年轻的热带森林，但氮（N）的损失在土地利用变化可能会改变化学计量平衡的养分循环过程。在亚马逊河流域，约16%的原始森林面积已被砍伐（6），据估计，约30 - 50%的被砍伐土地在农业废弃后已处于次生林演替的某个阶段（7）。在这里，我们使用森林年龄时序表明，年轻的演替森林农业废弃后，高度风化的低地热带土壤表现出保守的N-循环特性很像那些在温带地区的年轻土壤上的N-有限的森林。随着次生演替的进展，N循环特性恢复，成熟低地热带森林典型的保守P循环的优势再次出现。这些连续的变化，在N：P循环比与林龄提供了一个机械的解释，最初较低，然后逐渐增加土壤排放的温室气体一氧化二氮（N2 O）。在次生林演替过程中的N和P循环的模式，在这里展示了十年的时间尺度，是类似的N-和P-循环模式在初级演替的土壤年龄超过数千万年，从而揭示了陆地生态系统中的N的可用性是短暂的，可以被破坏的自然或人为干扰在几个时间尺度。
Phosphorus ( P) is generally considered the most common limiting nutrient for productivity of mature tropical lowland forests growing on highly weathered soils(1-5). It is often assumed that P limitation also applies to young tropical forests, but nitrogen (N) losses during land-use change may alter the stoichiometric balance of nutrient cycling processes. In the Amazon basin, about 16% of the original forest area has been cleared(6), and about 30 - 50% of cleared land is estimated now to be in some stage of secondary forest succession following agricultural abandonment(7). Here we use forest age chronosequences to demonstrate that young successional forests growing after agricultural abandonment on highly weathered lowland tropical soils exhibit conservative N-cycling properties much like those of N-limited forests on younger soils in temperate latitudes. As secondary succession progresses, N-cycling properties recover and the dominance of a conservative P cycle typical of mature lowland tropical forests re-emerges. These successional shifts in N: P cycling ratios with forest age provide a mechanistic explanation for initially lower and then gradually increasing soil emissions of the greenhouse gas nitrous oxide (N2O). The patterns of N and P cycling during secondary forest succession, demonstrated here over decadal timescales, are similar to N- and P-cycling patterns during primary succession as soils age over thousands and millions of years, thus revealing that N availability in terrestrial ecosystems is ephemeral and can be disrupted by either natural or anthropogenic disturbances at several timescales.