The global exposure of forests to air pollutants
The global exposure of forests to air pollutants
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DOI：
10.1023/a:1005249231882
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发表时间：
1999-11-01
影响因子：
2.9
通讯作者：
Stevenson, D
中科院分区：
文献类型：
--
作者：
Fowler, D;Cape, JN;Stevenson, D
高大的、空气动力学粗糙的森林表面为陆地表面和大气之间的热量和动量的有效交换提供了条件。森林的同样特性也为污染物气体、气溶胶和云滴提供了很大的潜在沉积率。对于一些活性污染物气体，包括SO2、HNO3和NH3，沉积速率可能很大，而且比在较短的植被上的沉积速率大得多，这是所谓的森林树冠“过滤效应”的原因。通过测量苏格兰南部一个未受污染的地点和德国东南部一个污染较重的地点的环境浓度，对输入到沼地和森林的污染物进行了比较。S和N对苏格兰森林的投入分别比高地高出16%和31%，分别为7.3 kg S ha(-1)y和10.6 kg N ha(-1)y(-1)。在大陆地区，S的森林输入和氮沉降分别比高地高出43%和48%，总计分别为53.6 kg S公顷(-1)y(-1)和69.5 kg N ha(-1)y(-1)。对全球森林的酸度输入表明，1985年S获得1 kg H+ha(-1)y(-1)的大部分地区处于温带纬度，全球森林总量的8%超过了这一门槛。到2050年，全球17%的森林将像S那样受到1千克H-1公顷(-1)的影响，其中大部分增加在热带和亚热带国家。世界各地的森林也将暴露在臭氧浓度升高的环境中。以60 ppb O-3作为可能对敏感森林物种产生植物毒性的浓度，用全球模式模拟了1860、1950、1970、1990和2100年全球森林暴露在潜在植物毒性O-3浓度下的情况。该模型显示，1860年没有暴露在超过60 ppb的浓度下，1950年全球6%的森林暴露在60 ppb的浓度下，75%在温带，25%在热带。到1990年，24%的全球森林暴露在60 ppb的O-3浓缩物中，到2100年，这个数字增加到全球森林的近50%。虽然全球森林未来污染气候的不确定性很大，但由于这些污染物之间的相互作用以及同期环境二氧化碳浓度、N沉降和气候的重大变化，O-3和酸沉降的可能影响更难评估，但这些影响不太可能总体上是有益的。
The tall, aerodynamically rough surfaces of forests provide for the efficient exchange of heat and momentum between terrestrial surfaces and the atmosphere. The same properties of forests also provide for large potential rates of deposition of pollutant gases, aerosols and cloud droplets. For some reactive pollutant gases, including SO2, HNO3 and NH3, rates of deposition may be large and substantially larger than onto shorter vegetation and is the cause of the so called "filtering effect" of forest canopies. Pollutant inputs to moorland and forest have been compared using measured ambient concentrations from an unpolluted site in southern Scotland and a more polluted site in south eastern Germany. The inputs of S and N to forest at the Scottish site exceed moorland by 16% and 31% respectively with inputs of 7.3 kg S ha(-1) y and 10.6 kg N ha(-1) y(-1). At the continental site inputs to the forest were 43% and 48% larger than over moorland for S and N deposition with totals of 53.6 kg S ha(-1) y(-1) and 69.5 kg N ha(-)1 y(-)1 respectively.The inputs of acidity to global forests show that in 1985 most of the areas receiving > 1 kg H+ ha(-1) y(-1) as S are in the temperate latitudes, with 8% of total global forest exceeding this threshold. By 2050, 17% of global forest will be receiving > 1 kg H-1 ha(-1) as S and most of the increase is in tropical and sub-tropical countries.Forests throughout the world are also exposed to elevated concentrations of ozone. Taking 60 ppb O-3 as a concentration likely to be phytotoxic to sensitive forest species, a global model has been used to simulate the global exposure of forests to potentially phytotoxic O-3 concentrations for the years 1860, 1950, 1970, 1990 and 2100. The model shows no exposure to concentrations in excess of 60 ppb in 1860, and of the 6% of global forest exposed to concentrations > 60 ppb in 1950, 75% were in temperate latitudes and 25% in the tropics. By 1990 24% of global forest is exposed to O-3 concentrates > 60 ppb, and this increases to almost 50% of global forest by 2100. While the uncertainty in the future pollution climate of global forest is considerable, the likely impact of O-3 and acid deposition is even more difficult to assess because of interactions between these pollutants and substantial changes in ambient CO2 concentration, N deposition and climate over the same period, but the effects are unlikely to be beneficial overall.