Natural regeneration of trees may provide a cost-effective way to restore degraded tropical dry forests, but the factors predominantly affecting natural regeneration success are poorly understood. We performed a multifactor analysis of natural regeneration in an Afromontane forest in Northern Ethiopia. Inventory plots of 400 m², each with a nested 9 m² subplot, were systematically established. All trees larger than 5 cm DBH and natural regeneration were identified and recorded in the plots and subplots, respectively. Variables describing climate, topography, soil, vegetation, and indications of local human degradation were collected. Determinants of regeneration presence and abundance were analyzed using Hurdle negative binomial regressions. Sixty-nine woody species were represented in the regeneration, with an average regeneration density (SE) of 14,700 (51) ha⁻¹. The presence of regeneration was positively associated with canopy cover (p < 0.001), distance to the road network (p = 0.04), precipitation (p = 0.003) and tree species diversity (p = 0.03), and negatively with Northing (p = 0.003). The regeneration abundance was positively associated with soil quality (p = 0.001), canopy cover (p = 0.04), and precipitation (p = 0.01). Including the abundance of dominant species in the tree canopy and regeneration layers in the regression model did not affect the presence of natural regeneration, but it clearly affected regeneration abundance. In such a model, the regeneration abundance was positively associated with Euclea racemosa seedlings abundance and negatively associated with the basal area of Dodonaea angustifolia (p = 0.02) and Rhus natalensis (p = 0.04). In this model, forest degradation (p = 0.01) negatively affected the late-successional species regeneration but not the regeneration of the drought-resistant light-demanding species. The low representation of late-successional trees species in the natural regeneration calls for active restoration intervention.

中文翻译：

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影响退化的干燥非洲山地森林自然更新的环境和人为因素

树木的自然更新可以提供一种具有成本效益的方法来恢复退化的热带干旱森林，但主要影响自然更新成功的因素知之甚少。我们对埃塞俄比亚北部的非洲山地森林的自然更新进行了多因素分析。400 m ^{2 的}库存图，每个都有一个嵌套的 9 m ²子情节，被系统地建立。所有大于 5 cm DBH 和自然更新的树木都分别被识别和记录在样地和子样地中。收集了描述气候、地形、土壤、植被和当地人类退化迹象的变量。使用障碍负二项式回归分析再生存在和丰度的决定因素。69 种木本树种在再生中代表，平均再生密度 (SE) 为 14,700 (51) ha ^-1。再生的存在与冠层覆盖 ( p  < 0.001)、到道路网络的距离 ( p  = 0.04)、降水 ( p  = 0.003) 和树种多样性 ( p) 呈正相关 = 0.03)，而北距则为负 ( p  = 0.003)。再生丰度与土壤质量 ( p  = 0.001)、冠层盖度 ( p  = 0.04) 和降水量 ( p  = 0.01)呈正相关。在回归模型中包括树冠和再生层中优势种的丰度并不影响自然再生的存在，但它明显影响了再生丰度。在这样的模型中，再生丰度与总状桉幼苗丰度呈正相关，与狭叶杜鹃( p  = 0.02) 和漆树( p = 0.04）。在该模型中，森林退化 ( p  = 0.01) 对晚继物种更新产生负面影响，但对抗旱、需光物种的更新没有负面影响。自然更新中晚继树种的代表性较低，需要积极的恢复干预。