The effect of broadleaved woodland on Chalk groundwater resources

The impact of broadleaved woodland on chalk groundwater resources, in Hampshire, UK, was assessed with a comparative study
of beech woodland at Black Wood near Micheldever and grass at Bridgets Farm near Winchester. At both sites, parallel estimates
of evaporation and detailed studies of the changes in soil water content and the direction of water movement were made.
Beneath both sites, a reduction in soil water content was observed during the summer to a depth of 6 m. However, total water
potential measurements showed that upward movement of water was only occurring in the upper 2 m of the profile, whilst drainage
was occurring below this point. Drainage continued even when soil moisture deficits existed in the upper part of the profile.
Seasonal differences between woodland and grass do exist, however annual differences in evaporation and drainage are insignificant.
The similarity of evaporation from and drainage below the broadleaved woodland and grass sites contrasts markedly with several
other studies that show greater drying below woodland. Unlike other comparisons, this study was made within a large block
of woodland and both sites were on chalk. The relevance of woodland size and chalk substrate are discussed.

本研究旨在评估英国汉普郡地区阔叶林对石灰岩地下水资源的 影响。通过对比分析米切德弗附近的布莱克伍德林和温切斯特附近的布里奇特农场草地，对两地的蒸发量和土壤水分含量变化及其水分流动方向进行了并行估算和深入研究。在夏季，两个研究地点的土壤水分含量均降至6米深度以下。然而，总水势测量结果显示，水分的上升运动仅发生在剖面上层2米处，而排水现象则发生在该点以下。即使在剖面上层存在土壤水分亏缺的情况下，排水现象仍持续进行。阔叶林与草地之间的季节性差异确实存在，但蒸发量和排水的年度差异则不显著。与显示林地下方干燥程度更高的其他研究相比，本研究在大型林地块内进行，且两个研究地点均位于石灰岩地区。本文讨论了林地规模和石灰岩基质的关联性。