Effects of enhanced nitrogen deposition and phosphorus limitation on nitrogen budgets of semi‐natural grasslands
Effects of enhanced nitrogen deposition and phosphorus limitation on nitrogen budgets of semi‐natural grasslands
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DOI：
10.1046/j.1365-2486.2003.00660.x
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发表时间：
2003-09
影响因子：
11.6
通讯作者：
G. Phoenix;R. Booth;J. Leake;D. Read;J. P. Grime;John A. Lee
中科院分区：
文献类型：
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作者：
G. Phoenix;R. Booth;J. Leake;D. Read;J. P. Grime;John A. Lee
物种丰富的酸性和石灰性草原的植物区系变化与大气反应性氮沉积的增加有关，但这种污染物氮在这些生态系统中的去向尚不清楚。本文首次对英国氮污染最严重的德比郡白峰区两个草地的氮素收支和氮素通量进行了分析。对未改良的酸性和石灰性草地的蒸渗仪岩心(保留原始草皮)的N通量进行了监测，这些草地在接受了3.5g和14g N m−2 a r−1的模拟强化N沉积处理后(除环境N沉降外)连续6年。通过P的因子添加来评估减少磷限制的影响，详细监测了硝酸盐、氨和有机氮的季节性淋失，以及通过模拟放牧去除N和通过反硝化和挥发去除气体的估计。这些路径的N通量速率被用来创建草原的N预算。这两个草地都积累了大量模拟的额外氮沉积：高达89%的氮积累在石灰性草原，高达38%的氮积累在酸性草原。这些草地氮素流失的主要通量是通过模拟放牧和淋溶的方式(在环境条件下占淋溶氮素的90%)。淋溶无机氮(主要是硝态氮)仅在最高氮处理下对氮素输出通量有显著贡献。氨挥发造成的氮素损失不到模拟沉降量的6%，而反硝化作用仅在冬季对酸性草地的氮素输出有显著贡献。讨论了结果对生态系统N平衡的影响，以及N在这些草原上积累的可能后果。
Increased reactive atmospheric N deposition has been implicated in floristic changes in species‐rich acidic and calcareous grasslands, but the fate of this pollutant N in these ecosystems is unknown. This paper reports the first analysis of N budgets and N fluxes for two grasslands in the White Peak area of Derbyshire, one of the most heavily N‐polluted locations in the UK. N fluxes were monitored in lysimeter cores (retaining the original turfs) taken from field plots of unimproved acidic and calcareous grasslands that had received (in addition to ambient N deposition) simulated enhanced N deposition treatments of 3.5 and 14 g N m−2 yr−1 for 6 years. The influence of reducing phosphorus limitation was assessed by factorial additions of P. Seasonal leached losses of nitrate, ammonia and organic N were monitored in detail along with estimates of N removal through simulated grazing and gaseous losses through denitrification and volatilization. The rates of N fluxes by these pathways were used to create N budgets for the grasslands. Both grasslands were found to be accumulating much of the simulated additional N deposition: up to 89% accumulated in the calcareous grassland and up to 38% accumulated in the acidic grassland. The major fluxes of N loss from these grasslands were by simulated grazing and leaching of soluble organic N (constituting 90% of leached N under ambient conditions). Leached inorganic N (mainly nitrate) contributed significantly to the output flux of N under the highest N treatment only. Loss of N through ammonia volatilization accounted for less than 6% of the N added as simulated deposition, while denitrification contributed significantly to output fluxes only in the acidic grassland during winter. The implications of the results for ecosystem N balances and the likely consequences of N accumulation on these grasslands are discussed.