Vegetation structure and the interception of acidic deposition by ombrotrophic mires

📝 Description

<div>Ombrotrophic mires are usually dominated by Sphagnum species which form an almost continuous carpet largely intercepting the atmospheric supply of elements in wet and dry deposition. In unpolluted conditions, some essential elements, e.g., nitrogen, are immobilized by these bryophytes and do not reach the roots of higher plants in appreciable quantities. Under these conditions, Sphagnum species can be shown to be closely coupled to the atmospheric nitrogen supply, inducing nitrate reductase activity in response co nitrate ions in each wet deposition event. In conditions of high acidic deposition this coupling breaks down, and nitrate supply is in excess of nitrate utilization, leading to nitrate appearing in Sphagnum throughfall and entering the rooting zones of the higher plants. The importance of Sphagnum species as interceptors of wet, dry and occult deposition is examined, and the ecological importance of a breakdown in the vegetation structure of mires as the result of acidic deposition</div><div>is discussed.</div>