Belowground Biomass Response to Nutrient Enrichment Depends on Light Limitation Across Globally Distributed Grasslands
Belowground Biomass Response to Nutrient Enrichment Depends on Light Limitation Across Globally Distributed Grasslands
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DOI：
10.1007/s10021-019-00350-4
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发表时间：
2019-11-01
期刊：
影响因子：
3.7
通讯作者：
Seabloom, Eric W.
中科院分区：
文献类型：
--
作者：
Cleland, Elsa E.;Lind, Eric M.;Seabloom, Eric W.
人为活动正在增加对全世界生态系统的养分投入，对全球碳和养分循环产生影响。最近的荟萃分析表明，地上初级生产往往是共同限制多种养分，但是，很少有人知道根生产如何响应养分供应的变化。在四大洲的29个草地站点，我们量化了浅根生物量对氮（N）、磷（P）和钾加微量营养素富集的响应，并比较了地下和地上的响应。我们假设，最优分配理论将预测背景依赖根生物量响应养分富集，在限制植物生长的资源（特别是光与养分）的网站之间的变化。与最优分配理论的预测相一致，地下总生物量的比例下降与N或P添加，由于地上生物量增加（N和P）和地下生物量减少（N，特别是在低冠层透光率的网站）。绝对根生物量增加，N除了在土壤表面的光是丰富的，但下降的网站，草地冠层截获了很大比例的入射光。这些结果表明，地下资源供应的变化的反应可以从地上的反应，这可能会显着修改未来的养分循环和固碳率的预测有很大的不同。我们的研究结果还强调了如何为个别植物开发的最优分配理论可能有助于预测地下生物量在生态系统尺度上对养分富集的反应，跨越广泛的气候和环境梯度。
Anthropogenic activities are increasing nutrient inputs to ecosystems worldwide, with consequences for global carbon and nutrient cycles. Recent meta-analyses show that aboveground primary production is often co-limited by multiple nutrients; however, little is known about how root production responds to changes in nutrient availability. At twenty-nine grassland sites on four continents, we quantified shallow root biomass responses to nitrogen (N), phosphorus (P) and potassium plus micronutrient enrichment and compared below- and aboveground responses. We hypothesized that optimal allocation theory would predict context dependence in root biomass responses to nutrient enrichment, given variation among sites in the resources limiting to plant growth (specifically light versus nutrients). Consistent with the predictions of optimal allocation theory, the proportion of total biomass belowground declined with N or P addition, due to increased biomass aboveground (for N and P) and decreased biomass belowground (N, particularly in sites with low canopy light penetration). Absolute root biomass increased with N addition where light was abundant at the soil surface, but declined in sites where the grassland canopy intercepted a large proportion of incoming light. These results demonstrate that belowground responses to changes in resource supply can differ strongly from aboveground responses, which could significantly modify predictions of future rates of nutrient cycling and carbon sequestration. Our results also highlight how optimal allocation theory developed for individual plants may help predict belowground biomass responses to nutrient enrichment at the ecosystem scale across wide climatic and environmental gradients.