Species Richness of Experimental Productivity Gradients: How Important is Colonization Limitation?
Species Richness of Experimental Productivity Gradients: How Important is Colonization Limitation?
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DOI：
10.2307/1939572
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发表时间：
1993-12
期刊：
影响因子：
4.8
通讯作者：
D. Tilman
中科院分区：
文献类型：
--
作者：
D. Tilman
一个网站的生物多样性应取决于当地殖民（增益）和灭绝（损失）率的相互作用，但很少有理论解释的多样性模式的生产力梯度包括殖民生产力的影响。在一项为期1年的研究中，通过氮添加增加生产力的实验通常会导致四个草地领域的物种丰富度下降。生产地块的多样性下降是由于物种获得率较低，现有物种的损失率较高。一年生禾本科和杂类草有很高的收益率和损失率，但这些都是独立的生产力。与此相反，多年生禾草和杂类草的增益率随着生产力的下降而下降，它们的损失率增加。物种丰富度取决于凋落物质量和光穿透，但不是地上活植物质量，这表明多样性的生产力没有直接的影响。多样性定期烧毁草原，其中有低凋落物质量，是独立的生产力的第10和第11年的研究。结果表明，多样性较低的生产性草地，因为积累的凋落物，并可能降低光的渗透，抑制发芽和/或幼苗的存活，从而降低新物种的建立率。更高的生产力也导致更高的损失率，可能是通过竞争取代现有物种。研究结果不支持土壤氮异质性在时间和空间尺度上控制多样性的假设。
The biodiversity of a site should depend on the interplay of local colonization (gain) and extinction (loss) rates, but few theoretical explanations of diversity patterns on productivity gradients have included effects of productivity on colonization. In an 1 -yr study, experimental increases in productivity via nitrogen addition generally led to de- creased species richness in four grassland fields. Decreased diversity in productive plots was caused as much by lower rates of species gain as by greater rates of loss of existing species. Annual grasses and forbs had high gain and loss rates, but these were independent of productivity. In contrast, the rates of gain of perennial grass and forb species declined with productivity, and their rates of loss increased. Species richness was dependent on litter mass and on light penetration, but not on aboveground living plant mass, suggesting that there was no direct effect of productivity on diversity. Diversity in periodically burned prairie, which had low litter mass, was independent of productivity by the 10th and 11th yr of the study. Results suggest that diversity is lower in productive grasslands because accumulated litter, and possibly lower light penetration, inhibit germination and/or survival of seedlings, and thus decrease rates of establishment by new species. Higher productivity also leads to higher rates of loss, presumably via competitive displacement, of existing species. Results do not support the hypothesis that soil N heterogeneity controls diversity on the temporal and spatial scales of this study.