Herbivory and misidentification of target habitat constrain region-wide restoration success of spekboom ( Portulacaria afra ) in South African subtropical succulent thicket

作者：Marius L. van der Vyver, Anthony Mills, Mark Difford, Richard M. Cowling · 发表于：PeerJ · 年份：2021 · DOI：10.7717/peerj.11944 · 被引用次数：19 · 研究领域：Ecology and Vegetation Dynamics Studies、Land Use and Ecosystem Services、Soil erosion and sediment transport

Restoration of degraded subtropical succulent thicket, via the planting of Portulacaria afra (spekboom) truncheons, is the focus of a public works programme funded by the South African government. The goals of the programme, which started in 2004, are to create jobs, sequester carbon, restore biodiversity, reduce erosion, improve soil water holding capacity and catalyse private sector investment for upscaling of restoration. Here we report on a region-wide experiment to identify factors that can improve project success. Measures of success were survivorship and annual aboveground biomass carbon sequestration (ABCsr) of spekboom truncheons some 33–57 months after planting—starting in March 2008—into 173 fenced plots (0.25 ha) located throughout the global extent of spekboom thicket vegetation. We also collected data for 18 explanatory variables under the control of managers, and an additional 39 variables reflecting soil physical and chemical characteristics and rainfall patterns post restoration, all beyond the influence of managers. Since the latter covariates were available for only 83 plots, we analysed the two data sets separately. We used a prediction rule ensemble to determine the most important predictors of restoration success. There was great variation in percentage survivorship (median = 24, range = 0–100%) and ABCsr (median = 0.009, range = 0–0.38 t C ha −1 yr −1 ). The model using management variables explained less variance (53%) in survivorship than the model in...