期刊
WATER AIR AND SOIL POLLUTION
卷 152, 期 1-4, 页码 233-255出版社
SPRINGER INTERNATIONAL PUBLISHING AG
DOI: 10.1023/B:WATE.0000015363.83436.a5
关键词
ammonia air concentrations; C/N ratio; forest edges; nitrogen deposition; nitrate leaching; soil solution; spruce forests
The atmospheric deposition of air pollutants was studied by means of monitoring canopy throughfall at six forest stands. The investigation was carried out in Norway spruce (Picea abies L. Karst.) forests in Southern Bavaria with high ambient ammonia concentrations due to either adjacent intensive agriculture or poultry housing. Five monitoring plots transected the forest edges and forest interior from the edge, at 50, 150, about 400 m and about 800 m to the interior. Additionally, nutrient concentration in soil solution was sampled with suction cups at each plot, and C/N ratio of the humus layer was also determined. The variation of ambient ammonia concentration between three of the six investigated sites was estimated using diffusive samplers. In order to compare the effects of atmospheric deposition on European beech (Fagus sylvatica L.) and Norway spruce additional monitoring plots were installed under each of these species in a mixed beech and spruce stand. Bulk deposition and soil water samples were analysed for major ions (NO3-, NH4+, SO42-, Cl-, Na+, K+, Mg2+, Ca2+). The results show a substantial increase of deposition towards the forest edges for all ions. This so called 'edge effect' continued in most cases until a distance from 50 to 150 m from edge. For both ambient ammonia concentrations and nitrogen deposition, it can be concluded that increased dry deposition is the main reason for the edge effect. Over 76% of the nitrogen ratios in throughfall deposition between the edge and 50 m distance into the spruce forest exceed 1.0. Except for potassium, beech generally showed lower ratios than spruce. Due to high nitrogen deposition the forest floor, C/N ratios were lower at stand edges when compared to their interior. In contrast to the increase of nitrogen deposition at the edge, nitrate export below the main rooting zone was lower at the edge. Nitrate export was generally lower under beech than spruce. Nitrogen budgets of some plots were negative, indicating a reduction of total ecosystem nitrogen stock. The results show that forest edges, especially in areas with high air pollution, receive much more atmospheric deposition than the interior parts of closed forest stands. As many deposition studies in forests were conducted at field stations in the central parts of forests the estimated deposition for the whole forest may be underestimated. This may be important to consider in geo-statistical studies and models aiming to estimate spatial critical deposition values, especially with an increasing fragmentation of the forest cover.
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