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首页> 外文学位 >Ecosystem responses to warming-induced plant species loss and increased nitrogen availability in a Rocky Mountain subalpine meadow.
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Ecosystem responses to warming-induced plant species loss and increased nitrogen availability in a Rocky Mountain subalpine meadow.

机译：生态系统对落基山亚高山草甸变暖引起的植物物种丧失和氮素利用增加的响应。

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Climate change is predicted to be an important driver of future biodiversity changes, especially in mountainous environments. Climate warming-induced plant species loss is likely to be non-random and based on species-specific susceptibility to rising temperatures. Experimental warming results from a subalpine meadow in Colorado suggest that warming adversely affects shallow-rooted forb species in this ecosystem. To examine the ecological consequences of losing this warming-sensitive species group, I experimentally removed all shallow-rooted forb species from otherwise intact subalpine meadow plots. Since experimental warming also resulted in increased soil nitrogen availability, I crossed the removal treatment with a nitrogen addition treatment to determine whether the loss of shallow-rooted forbs altered the community's response to a perturbation in nitrogen availability.; After three years of experimental species removal, tap-rooted forbs and grasses were able to fully compensate for the loss of shallow-rooted forbs with increased biomass production. Moreover, the remaining plant community yielded a larger biomass response to nitrogen addition when shallow-rooted forbs were removed, possibly because removal led to increased soil moisture. The loss of shallow-rooted forbs and addition of nitrogen did not have strong effects on nitrogen cycling beyond increases in the amount of nitrate moving down through the soil profile. Uptake of nitrogen into plant tissue was also not affected by either the shallow-rooted forb removal or nitrogen addition treatments, suggesting that nitrogen may not have been the most limiting resource during the experiment. I found that spatial heterogeneity generally had a greater influence on soil microbial community composition than any of the experimental treatments.; I conclude that the warming-induced loss of shallow-rooted forbs did not affect biomass production, nitrogen cycling, or soil microbial community composition, but did increase the ecosystem's sensitivity to a perturbation in nitrogen availability. My results demonstrate that non-random scenarios of species loss do not necessarily follow the pattern of decreased productivity, decreased nitrogen uptake, increased nitrogen losses, and dampened response to nitrogen addition with species loss that is predicted by theory and experimental results from randomly-assembled plant communities. Therefore, caution should be used in applying results from randomly-assembled communities to natural communities undergoing non-random species loss.
机译：预计气候变化将是未来生物多样性变化的重要推动力，尤其是在山区环境中。气候变暖导致的植物物种流失很可能是非随机的，并且基于物种对温度升高的敏感性。来自科罗拉多州一个高山草甸的实验性变暖结果表明，变暖对这个生态系统中的浅根Forb物种产生了不利影响。为了研究失去这种对温度敏感的物种的生态后果，我实验性地从原本完整的亚高山草甸地块中去除了所有浅根的福布斯物种。由于实验性升温也导致土壤氮素利用率的增加，我将去除处理与氮素添加处理相结合，以确定浅根前缘草的损失是否改变了社区对氮素利用率扰动的响应。经过三年的实验物种清除，自生根的前缘草和草能够完全补偿生物量增加而产生的浅根前缘草的损失。此外，当去除浅根的前穗时，其余植物群落对氮的添加产生更大的生物量响应，这可能是因为去除导致土壤水分增加。浅根前叉的丧失和氮的添加对氮循环的影响不大，而在土壤剖面中向下移动的硝酸盐的数量却增加了。浅根前叉去除或氮添加处理也未影响氮向植物组织的吸收，这表明氮可能不是实验期间的最大限制资源。我发现，空间异质性通常比任何实验处理对土壤微生物群落组成的影响更大。我得出的结论是，由变暖引起的浅根前叉的损失不会影响生物量的产生，氮的循环或土壤微生物群落的组成，但会增加生态系统对氮素供应扰动的敏感性。我的结果表明，物种流失的非随机场景并不一定遵循生产率和氮吸收减少，氮流失增加以及对氮添加的响应减弱以及物种流失的模式，这是由随机组装的理论和实验结果预测的植物群落。因此，在将随机组装的社区的结果应用于遭受非随机物种损失的自然社区时，应谨慎行事。

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