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首页> 外文期刊>Biogeochemistry >Atmospheric deposition and watershed nitrogen export along an elevational gradient in the Catskill Mountains, New York.
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Atmospheric deposition and watershed nitrogen export along an elevational gradient in the Catskill Mountains, New York.

机译：纽约州卡茨基尔山脉的大气沉积和流域氮沿高度梯度出口。

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Cumulative effects of atmospheric N deposition may increase N export from watersheds and contribute to the acidification of surface waters, but natural factors (such as forest productivity and soil drainage) that affect forest N cycling can also control watershed N export. To identify factors that are related to stream-water export of N, elevational gradients in atmospheric deposition and natural processes were evaluated in a steep, first-order watershed in the title area of the USA from 1991 to 1994. Atmospheric deposition of SO42-, and probably N, increased with increasing elevation within this watershed. Stream-water concentrations of SO42- increased with increasing elevation throughout the year, whereas stream-water concentrations of NO3- decreased with increasing elevation during the winter and spring snowmelt period, and showed no relation with elevation during the growing season or the autumn. Annual export of N in stream water for the overall watershed equalled 12% to 17% of the total atmospheric input on the basis of two methods of estimation. This percentage decreased with increasing elevation, from～25% in the lowest subwatershed to 7% in the highest subwatershed; a probable result of an upslope increase in the thickness of the surface organic horizon, attributable to an elevational gradient in temperature that slows decomposition rates at upper elevations. Balsam fir (Abies balsamea) stands, more prevalent at upper elevations than lower elevations, may also affect the gradient of subwatershed N export by altering nitrification rates in the soil. Variations in climate and vegetation must be considered to determine how future trends in atmospheric deposition will effect watershed export of nitrogen.
机译：大气氮沉降的累积效应可能会增加流域的氮出口并促进地表水的酸化，但是影响森林氮循环的自然因素（例如森林生产力和土壤排水）也可以控制流域氮的出口。为了确定与N的河水输出有关的因素，在1991年至1994年美国标题地区的一个陡峭的一级流域中，评估了大气沉积和自然过程中的海拔梯度。SO42-，随着流域内海拔的升高，N可能会增加。在冬季和春季融雪期间，SO42-的河水浓度随海拔的升高而增加，而NO3-的河水浓度在冬季和春季融雪期间随海拔的升高而降低，并且与生长季节或秋季的海拔无关。根据两种估算方法，整个流域的溪流水中氮的年出口量相当于大气总输入量的12％至17％。该百分比随着海拔的升高而降低，从最低子流域的〜25％到最高子流域的7％;温度升高的梯度可能会降低表面有机层厚度的上升，这可能是由于降低了较高海拔处的分解速率所致。苦瓜（Abies balsamea）林分，高海拔地区比低海拔地区更普遍，它也可能通过改变土壤中的硝化率而影响分水岭下N出口的梯度。必须考虑气候和植被的变化，以确定未来大气沉积趋势将如何影响流域的氮出口。

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