Impact of Land Management on Available Water Capacity and Water Storage of Peat

Abstract

<p>In Germany, more than 95% of peatlands have been drained for agriculture and forestry leading to water as well as carbon storage loss, soil degradation, and water eutrophication. Soil available water capacity (AWC) is one of the most important soil properties regulating the water balance and plays a pivotal role in plant growth. Compared with that of mineral substrates, our understanding of the impact of land management on water storage and the AWC of peat is limited. In this study, we aimed to deduce possible alterations of the AWC and water storage of peat following land drainage and rewetting. We analyzed a comprehensive database (674 measurements from boreal and temperate peatlands) to seek relations between bulk density (BD), field capacity, wilting point, and AWC. Bulk density was used as a proxy for soil degradation. The AWC increases with BD up to a value of 0.2 g cm<sup>−3</sup>; a further increase in BD leads to a considerable decrease in AWC. The derived function between BD and AWC enables us to upscale the AWC to a regional scale. The average AWC of agricultural peatlands in Germany is estimated to be 37 ± 11 vol% (mean ± standard deviation). Currently, the water storage of agricultural peatlands in Germany is approximately 1.0 m<sup>3</sup> per m<sup>2</sup>. We estimated that water storage in the natural peatlands in Germany was 33.8 km<sup>3</sup> prior to drainage. Converting natural peatlands into agricultural land resulted in a water storage loss of approximately 18.6 km<sup>3</sup>. Several decades of peatland rewetting have a limited effect on water storage recovery due to a substantial loss of peat thickness because of former drainage and a low porosity of degraded peat.</p>