北京大学刘鸿雁组研究了大规模造林是否会导致中国旱地出现水土短缺危机。2024年3月4日，国际知名学术期刊《科学通报》发表了这一成果。

研究人员收集了来自中国北方98个样地的1226个观测数据，以评估造林后土壤含水量（SWC）随林龄的变化规律，揭示了树种、降水和土地利用类型转换对土壤含水量的影响。研究发现，自1978年以来，针叶林和阔叶林的SWC分别以每十年0.6毫米和每十年3.2毫米的速率递减。随着人工林林龄的增加，森林SWC有明显的下降趋势，北方地区人工林的最佳生长期为0-20 a。

然而，研究发现，草地向森林转化和低降水量地区的SWC增加与针叶林的SWC增加相对应。结果表明，在区域尺度上，造林可能导致中国北方土壤水分亏缺危机，但这取决于先前的土地利用类型、树木类群和年平均降水情况，这为制定旱地生态恢复政策和水资源管理的决策提供了启示。

据悉，用水换碳已经对全球旱地的大规模造林提出了警告。然而，模型模拟表明，由于植被的反馈，土壤水分的消耗可以通过增加降雨量来部分抵消。迫切需要对长期和大规模的野外观测进行系统的meta分析，以解决上述局限性，自1978年以来，中国北方实施的大规模造林为解决上述问题提供了一个理想的例子。

附：原文原文

Title: Will large–scale forestation lead to a soil water deficit crisis in China's drylands

Author: Qiuming Wang, Hongyan Liu, Boyi Liang, Liang Shi, Lu Wu, Jing Cao

Issue&Volume: 2024/03/04

Abstract: Trading water for carbon has cautioned large-scale afforestation in global drylands. However, model simulations suggested that the consumption of soil water could be partially offset by increasing precipitation due to vegetation feedback. A systematic meta–analysis of long–term and large–scale field observations is urgently required to address the abovementioned limitations, and the implementation of large–scale afforestation since 1978 in northern China, provides an ideal example. This study collected data comprising 1226 observations from 98 sites in northern China to assess the variation in soil water content (SWC) with stand age after afforestation and discuss the effects of tree species, precipitation and conversions of land use types on SWC. We found that the SWC has been decreased by coniferous forest and broadleaf forest at rates of 0.6 mm decade^–1 and 3.2 mm decade^–1, respectively, since 1978. There is a significant declining trend of SWC with the stand age of plantations, and the optimum growth stage for artificial forests is 0–20 a in northern China. However, we found increases in SWC for the conversion from grassland to forest and in the low–precipitation region, both are corresponding to the increased SWC in coniferous forest. Our study implies that afforestation might lead to a soil water deficit crisis in northern China in the long term at the regional scale but depends on prior land use types, tree taxa and the mean annual precipitation regime, which sheds light on decision–making regarding ecological restoration policies and water resource management in drylands.

DOI: 10.1016/j.scib.2024.03.005

Source: https://www.sciencedirect.com/science/article/abs/pii/S209592732400149X