Hydric, root and soil cohesions and cohesion from biomass, water and soil loading under various land uses in Laos, Costa Rica and France hillslopes between 2012 and 2015

Although vegetation is increasingly used to mitigate landslide risks, how vegetation affects the temporal variability of slope stability is poorly understood, especially in earthquake-prone regions. We combined 3-year long soil moisture monitoring, measurements of soil physical properties and plant functional traits, and numerical modeling to compare slope stability under paired land uses with and without trees in tropical, sub-tropical, and temperate landslide- and earthquake-prone regions. Trees improved stability for 5-12 months per year from drawdown of soil moisture and resulted in less interannual variability in the duration of high-stability periods compared to slopes without trees. Our meta-analysis of published data also showed that slopes with woody vegetation were more stable and less sensitive to climate and soil factors than slopes with herbaceous vegetation. However, estimates of earthquake magnitude necessary to destabilize slopes at our sites suggest that large additional stabilization from trees is necessary for meaningful protection against external triggers.

尽管植被在滑坡风险防控中的应用日益广泛，但学界对植被如何影响边坡稳定性的时间变异性仍知之甚少，在地震多发区域这一问题尤为突出。本研究结合为期3年的土壤湿度监测、土壤物理性质与植物功能性状测量，以及数值模拟手段，在热带、亚热带及温带滑坡与地震多发区域，针对有无树木覆盖的配对土地利用场景下的边坡稳定性展开对比分析。结果显示，相较于无树边坡，树木可通过降低土壤含水率使边坡稳定性每年提升5至12个月，并降低了高稳定期时长的年际变异性。本研究对公开数据开展的荟萃分析同样表明，相较于草本植被覆盖的边坡，木本植被覆盖的边坡稳定性更强，且对气候与土壤因子的敏感性更低。不过，针对本研究站点边坡失稳所需地震震级的估算结果显示，若要通过植被实现对外部触发因素的有效防护，仍需树木额外提供大幅的边坡稳定性提升。