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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Nonlinear responses to nitrogen and strong interactions with nitrogen and phosphorus additions drastically alter the structure and function of a high arctic ecosystem
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Nonlinear responses to nitrogen and strong interactions with nitrogen and phosphorus additions drastically alter the structure and function of a high arctic ecosystem

机译：对氮的非线性响应以及与氮和磷的添加之间的强烈相互作用极大地改变了北极高生态系统的结构和功能

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摘要

Significant changes in ecosystem CO2 exchange and vegetation characteristics were observed following multiple additions of nitrogen (N) and factorial additions of N and phosphorus (P) to prostrate dwarf-shrub, herb tundra in Northwest Greenland. Ecosystem CO2 exchange and vegetation cover and composition were very sensitive to low rates of N inputs (0.5 g m?2 y?1), indicating that even low rates of atmospheric N deposition may alter high arctic ecosystem structure and function. Increasing N addition from 1 to 5 g N m?2 y?1 did not alter CO2 exchange or vegetation characteristics, suggesting the ecosystem had become N saturated. Factorial additions of both N and P released the ecosystem from N saturation and dramatically increased gross ecosystem photosynthesis (+500%) and ecosystem respiration (+250%), such that the ecosystem switched from a small source of CO2 to a small sink for CO2 at midday during the 2005 growing season. Changes in the component fluxes of CO2 exchange were largely explained by a doubling of the normalized difference vegetation index, a 100% increase in vascular plant cover and dramatic increases in the abundance of several previously rare grass species. Our results clearly demonstrate that high arctic prostrate dwarf-shrub, herb tundra is highly sensitive to low levels of N addition and that future increases in N deposition or N mineralization will likely lead to change in carbon cycling and vegetation characteristics, but the magnitude of the response will be constrained by P availability.
机译：在西北格陵兰西南部矮化灌木，苔原苔下，多次添加氮（N）和析因添加氮和磷（P）后，观察到生态系统CO2交换和植被特征发生了显着变化。生态系统的CO2交换，植被覆盖和组成对低氮输入量（0.5 g m？2 y？1）非常敏感，这表明即使低速的大气氮沉积也可能会改变北极高生态系统的结构和功能。将氮的添加量从1 g N m？2 y？1增加到5 g不会改变CO2交换或植被特征，这表明生态系统已变得N饱和。氮和磷的因子添加使生态系统从氮饱和状态释放出来，并显着增加了生态系统的总光合作用（+ 500％）和生态系统呼吸作用（+ 250％），从而使生态系统从少量的CO2转换为较小的CO2汇。在2005年生长季节的中午。归一化差异植被指数加倍，维管束植物覆盖率增加100％和几种以前稀有草种的丰度显着增加，很大程度上解释了CO2交换组分通量的变化。我们的结果清楚地表明，高寒北极矮化灌木，草本苔原对低水平的氮添加高度敏感，未来氮沉降或氮矿化的增加可能会导致碳循环和植被特征的变化，但是响应将受到P可用性的限制。

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