Aims

One of the most important questions of our time is how ecosystems will be transformed by climate change. Here, we used a five-year field experiment to investigate the effects of climate warming on the cover and function of a sub-Arctic alpine ecosystem in the highlands of Iceland dominated by biocrust, mosses and vascular plants.

Methods

We used Open Top Chambers (OTCs) to simulate warming; standard surface and Normalised Difference Vegetation Index (NDVI) analyses to measure plant cover and function; gas analyzers to monitor biocrust respiration; and the Tea Bag Index approach to estimate mass loss, decomposition and soil carbon stabilization rates.

Results

Contrary to our initial hypothesis of warming accelerating an ecological succession of plants growing on biocrust, we observed a warming-induced decreased abundance of vascular plants and mosses —possibly caused by high temperature summer peaks that resemble heat waves— and an increase in the cover of biocrust. The functional responses of biocrust to warming, including increased litter mass loss and respiration rates and a lower soil carbon stabilization rates, may suggest climate-driven depletion of soil nutrients in the future.

Conclusion

It remains to be studied how the effects of warming on biocrusts from high northern regions could interact with other drivers of ecosystem change, such as grazing; and if in the long-term global change could favor the growth of vascular plants on biocrust in the highlands of Iceland and similar ecosystems. For the moment, our experiment points to a warming-induced increase in the cover and activity of biocrust.

中文翻译：

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经过五个生长季的实验性变暖后，冰岛高地的生物结皮覆盖和活动增加

 目标

我们这个时代最重要的问题之一是气候变化将如何改变生态系统。在这里，我们利用为期五年的实地实验来研究气候变暖对冰岛高地以生物结皮、苔藓和维管植物为主的亚北极高山生态系统的覆盖和功能的影响。

 方法

我们使用开顶室 (OTC) 来模拟变暖；标准表面和归一化植被指数 (NDVI) 分析以测量植物覆盖和功能；用于监测生物结皮呼吸的气体分析仪；以及茶袋指数方法来估计质量损失、分解和土壤碳稳定率。

 结果

与我们最初的假设相反，即变暖加速了生物结皮上生长的植物的生态演替，我们观察到变暖引起的维管束植物和苔藓的丰度减少（可能是由类似于热浪的夏季高温高峰引起的）以及植物覆盖度的增加。生物结壳。生物结皮对变暖的功能反应，包括凋落物质量损失和呼吸速率的增加以及土壤碳稳定率的降低，可能表明未来气候驱动的土壤养分消耗。

 结论

变暖对北部高地生物结皮的影响如何与生态系统变化的其他驱动因素（例如放牧）相互作用，仍有待研究。从长远来看，全球变化是否有利于冰岛高地和类似生态系统生物结皮上维管束植物的生长。目前，我们的实验表明变暖导致生物结皮的覆盖和活动增加。