Department of Ecology, University of Szeged, Közép fasor 52, Szeged 6726, Hungary; MTA-SZTE Lendület Applied Ecology Research Group, Közép fasor 52, Szeged 6726, Hungary.
Department of Ecology, University of Szeged, Közép fasor 52, Szeged 6726, Hungary.
Sci Total Environ. 2023 Jan 15;856(Pt 1):158960. doi: 10.1016/j.scitotenv.2022.158960. Epub 2022 Sep 24.
The most widespread nature-based solution for mitigating climate change is tree planting. When realized as forest restoration in historically forested biomes, it can efficiently contribute to the sequestration of atmospheric carbon and can also entail significant biodiversity and ecosystem service benefits. Conversely, tree planting in naturally open biomes can have adverse effects, of which water shortage due to increased evapotranspiration is among the most alarming ones. Here we assessed how soil texture affects the strength of the trade-off between tree cover and water balance in the forest-steppe biome, where the global pressure for afforestation is threatening with increasing tree cover above historical levels. Here we monitored vertical soil moisture dynamics in four stands in each of the most common forest types of lowland Hungary on well-drained, sandy (natural poplar groves, and Robinia and pine plantations) and on poorly drained, silty-clayey soils (natural oak stands and Robinia plantations), and neighboring grasslands. We found that forests on sand retain moisture in the topsoil (approx. 20 cm) throughout the year, but a thick dry layer develops below that during the vegetation period, significantly impeding groundwater recharge. Neighboring sandy grasslands showed an opposite pattern, with often dry topsoil but intact moisture reserves below, allowing deep percolation. In contrast, forests on silty-clayey soils did not desiccate lower soil layers compared neighboring grasslands, which in turn showed moisture patterns similar to sandy grasslands. We conclude that, in water-limited temperate biomes where landscape-wide water regime depends on deep percolation, soil texture should drive the spatial allocation of tree-based climate mitigation efforts. On sand, the establishment of new forests should be kept to a minimum and grassland restoration should be preferred. The trade-off between water and carbon is less pronounced on silty-clayey soils, making forest patches and wooded rangelands viable targets for both climate mitigation and ecosystem restoration.
缓解气候变化最广泛的基于自然的解决方案是植树造林。当它在历史上有森林的生物群落中实现为森林恢复时，它可以有效地促进大气碳的固存，并且还可以带来显著的生物多样性和生态系统服务效益。相反，在自然开阔的生物群落中植树造林可能会产生不利影响，其中由于蒸散增加而导致的水资源短缺是最令人担忧的影响之一。在这里，我们评估了土壤质地如何影响森林-草原生物群落中树木覆盖与水分平衡之间权衡的强度，在该生物群落中，全球造林压力正在威胁着超过历史水平的树木覆盖。在这里，我们监测了匈牙利低地最常见的森林类型中的四个林分中的垂直土壤水分动态，这些林分分别位于排水良好的沙质土壤上（天然白杨林、刺槐和松林）和排水不良的粉砂-粘土地上（天然橡树林和刺槐林），以及相邻的草原上。我们发现，沙地上的森林在整个生长季节都能保持表土（约 20 厘米）中的水分，但在植被生长期间，下面会形成一层厚厚的干燥层，严重阻碍地下水补给。相邻的沙质草原则表现出相反的模式，表土通常干燥，但下面仍有完整的水分储备，允许深层渗透。相比之下，在粉砂-粘土地上的森林与相邻的草原相比，不会使下层土壤变干，而相邻的草原则表现出与沙质草原相似的水分模式。我们得出结论，在水资源有限的温带生物群落中，景观范围的水分状况取决于深层渗透，土壤质地应该驱动基于树木的气候缓解努力的空间分配。在沙地上，应尽量减少新森林的建立，并优先进行草原恢复。在粉砂-粘土地上，水和碳之间的权衡关系不太明显，这使得森林斑块和树木繁茂的牧场成为气候缓解和生态系统恢复的可行目标。
