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首页> 外文期刊>Biogeosciences >Edaphic, structural and physiological contrasts across Amazon Basin forest-savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function
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Edaphic, structural and physiological contrasts across Amazon Basin forest-savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function

机译：亚马逊河流域森林-热带稀树草原过渡带之间的粗化，结构和生理对比表明钾是热带木本植被结构和功能的关键调节剂

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Sampling along a precipitation gradient in tropical South America extending from ca. 0.8 to 2.0 m a(-1), savanna soils had consistently lower exchangeable cation concentrations and higher C/N ratios than nearby forest plots. These soil differences were also reflected in canopy averaged leaf traits with savanna trees typically having higher leaf mass per unit area but lower mass-based nitrogen (N-m) and potassium (K-m). Both N-m and K-m also increased with declining mean annual precipitation (P-A), but most area-based leaf traits such as leaf photosynthetic capacity showed no systematic variation with P-A or vegetation type. Despite this invariance, when taken in conjunction with other measures such as mean canopy height, area-based soil exchangeable potassium content, [K](sa), proved to be an excellent predictor of several photosynthetic properties (including C-13 isotope discrimination). Moreover, when considered in a multivariate context with P-A and soil plant available water storage capacity (theta(P)) as covariates, [K](sa) also proved to be an excellent predictor of stand-level canopy area, providing drastically improved fits as compared to models considering just P-A and/or theta(P). Neither calcium, nor magnesium, nor soil pH could substitute for potassium when tested as alternative model predictors (Delta AIC > 10). Nor for any model could simple soil texture metrics such as sand or clay content substitute for either [K](sa) or theta(P). Taken in conjunction with recent work in Africa and the forests of the Amazon Basin, this suggests in combination with some newly conceptualised interacting effects of P-A and theta(P) also presented here - a critical role for potassium as a modulator of tropical vegetation structure and function.
机译：从南美洲热带沿南美洲降水沿降水梯度采样。 0.8到2.0 m a（-1）的稀树草原土壤的可交换阳离子浓度和C / N比值始终比附近的林地低。这些土壤差异也反映在冠层平均叶片性状上，热带稀树草原的单位面积叶片质量通常较高，而氮素（N-m）和钾素（K-m）较低。 N-m和K-m均随着年均降水量（P-A）的减少而增加，但是大多数基于区域的叶片性状（如叶片的光合能力）均未显示P-A或植被类型的系统性变化。尽管存在这种不变性，但与其他措施（例如平均冠层高度，基于区域的土壤中可交换钾含量[K]（sa））一起使用时，被证明是几种光合特性（包括C-13同位素歧视）的出色预测指标。此外，在以PA和土壤植物可用储水量（theta（P））作为协变量的多变量环境中考虑时，[K]（sa）也被证明是站立水平冠层面积的极佳预测指标，可显着改善拟合度与仅考虑PA和/或theta（P）的模型相比。作为替代模型预测指标进行测试时，钙，镁，土壤pH都不能替代钾（Delta AIC> 10）。对于任何模型，简单的土壤质地指标（例如沙子或粘土含量）都无法替代[K]（sa）或theta（P）。结合近期在非洲和亚马逊河流域森林中的工作，这表明结合了PA和theta（P）的一些新概念化的相互作用，在这里也提出了钾的作用-钾作为热带植被结构调节剂的关键作用。功能。

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