In Mediterranean mountain socio-ecosystems, both grazing by livestock and the dry season may influence tree regeneration. However, the relative contributions of these drivers are poorly known, even though present and future canopy composition might result from past and present variations in climate and herbivore density. This study aims to test how semi-feral cattle presence and season affect tree regeneration. The study was conducted using permanent plots inside and outside a cattle exclosure in an old-growth Mediterranean forest. Saplings and seedlings were counted five times per year (winter, early spring, middle spring, summer, fall) and monitored over 7 yrs. Semi-feral cattle exclusion increased Acer, Fagus, Ilex, Pinus, Prunus and Quercus sapling densities and increased Acer, Fraxinus, Ilex, Quercus and Sorbus seedling densities. Interestingly, the dry season did not exert any noticeable effects on the sapling or seedling densities of any of the studied taxa. Semi-feral cattle presence may limit tree regeneration through taxon-dependent effects, which suggests that the current decrease in grazing livestock across the Mediterranean basin will modify recruitment processes and, likely, future forest composition. Semi-feral cattle presence acts as a selective driver of tree community composition.

中文翻译：

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半野生牛放牧对地中海老龄山区森林树木更新的选择性和分类依赖性

在地中海山区的社会生态系统中，牲畜放牧和干旱季节都可能影响树木的再生。然而，尽管当前和未来的冠层组成可能是由于过去和现在的气候和草食动物密度的变化所致，但这些驱动因素的相对贡献却鲜为人知。这项研究旨在测试半野生牛的存在和季节如何影响树木的再生。这项研究是在地中海古老的森林中使用牛棚内外的永久性地块进行的。每年对树苗和幼苗进行五次计数（冬季，早春，中春，夏季，秋季），并在7年内进行监测。半野生牛排斥增加了Acer，Fagus，Ilex，Pinus，Prunus和Quercus树苗的密度，并增加了Acer，Fraxinus，Ilex，Quercus和Sorbus幼苗的密度。有趣的是，旱季对任何所研究的类群的树苗或幼苗密度均未产生任何明显的影响。半野生牛的存在可能通过依赖分类群的作用限制树木的再生，这表明整个地中海盆地目前放牧牲畜的减少将改变征募过程，并可能改变未来的森林组成。半野生牛的存在是树木群落组成的选择性驱动因素。