Seedling light limitation does not increase across a natural productivity gradient
Seedling light limitation does not increase across a natural productivity gradient
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幼苗光照限制不会随着自然生产力梯度的增加而增加
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发表时间：
2013
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通讯作者：
Emily Grman
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作者：
Emily Grman
目标植物群落生态学的一个关键思想是，限制资源的身份从低生产力地点的土壤养分转移到高生产力地点的光。这个想法及其对植物群落结构的影响已经在人工生产力梯度（施肥研究）中进行了多次测试，但它是否适用于自然生产力梯度尚不清楚。方法为了测试幼苗光照限制是否会在自然生产力梯度上增加，我在美国密歇根州西南部进行了一项跨地点田间实验。在六个生产力自然不同的老田中，我将移植的大须芒草（Andropogon gerardii）幼苗暴露于光添加（回接）处理中，以增加光的可用性，并在一个和两个生长季节后测量它们的生物量。重要发现 幼苗对回接处理有积极反应，但积极反应并没有在自然生产力梯度上增加。这些结果表明，尽管光确实限制了幼苗的建立，但光限制的强度并不取决于自然系统生产力的变化。相反，光照限制与各种位点差异相互作用来确定建立。尽管光限制随生产力增加而增加的一般原则已得到充分确立，但这些结果表明它可能并不总是发生在自然系统中。
Aims A key idea in plant community ecology is that the identity of the limiting resource shifts from soil nutrients in low productivity sites to light in high productivity sites. This idea, and its implications for plant community structure, has been tested many times in artificial productivity gradients (fertilization studies), but whether it applies to natural productivity gradients is unclear. Methods To test whether seedling light limitation would increase across a natural productivity gradient, I conducted a cross-site field experiment in southwest Michigan, USA. At each of six old fields naturally varying in productivity, I exposed transplanted seedlings of big bluestem (Andropogon gerardii) to a light addition (tie-back) treatment that increased light availability and measured their biomass after one and two growing seasons. Important Findings Seedlings responded positively to the tie-back treatment, but positive responses did not increase across the natural productivity gradient. These results suggest that although light does limit seedling establishment, the strength of light limitation does not depend on variation in productivity in natural systems. Instead, light limitation interacted with a variety of site differences to determine establishment. Although the general principle that light limitation increases with productivity is well established, these results indicate that it may not always occur in natural systems.