Historical Use Data

Some traditional practices such as grazing have been crucial for promoting ecosystem diversity, resilience, and heterogeneity. However, the effects of ungulates on ecosystem services vary widely and depend on the context. One of the most influential factors determining these effects is their population density, including both wild and domestic ungulates. Currently, in Doñana National Park, domestic and wild ungulates coexist, reaching high densities in some estates. In many areas of the park, Mediterranean forest regeneration is limited due to declining water tables, pest and pathogen impacts, and the effects of large ungulates. The poor regeneration of these forests poses a threat to the biodiversity they support and the ecosystem services they provide. In this study, we make use of a set of exclosures constructed 15 years ago - that gradually became more permeable to the ungulates they were designed to exclude- to study the short- and long-term impact of ungulates on Mediterranean woodland vegetation in Doñana National Park. Specifically, it examines three key aspects: (1) plant damage and consumption, (2) sapling density (i.e., recruitment) and (2) plant size (i.e., establishment and growth). We observed significant levels of damage and browsing on branches when domestic herbivores were present in moderate or high relative abundances, showing a linear effect. In contrast, the impact of wild herbivores increased with their abundance but tended to saturate at higher densities and, in some cases, even decreased. We did not observe clear or consistent effects of herbivores on the saplings density of various species, likely due to the low number of saplings found (n = 62), which may suggest very low recruitment of the species studied within the enclosures. Regarding the establishment and growth of juvenile plants, both the average height and canopy size, as well as their variation, were generally lower in areas with a historically higher presence of herbivores. With climate change, the adverse effects of herbivory on Mediterranean forest ecosystems, as observed in this study, could become more severe. It is essential to continue researching the ecological interactions between herbivores and the park's ecosystems. This knowledge can be applied to the development of management strategies to balance livestock production, wildlife conservation, and the resilience of Mediterranean ecosystems to climate change.

诸如放牧在内的诸多传统实践，对促进生态系统多样性、韧性（resilience）与异质性（heterogeneity）至关重要。然而，有蹄类动物（ungulates）对生态系统服务的影响差异显著，且效应依情境而异。决定此类效应的最关键因素之一，便是其种群密度，涵盖野生与家养有蹄类动物。目前，在多尼亚纳国家公园（Doñana National Park）内，家养与野生有蹄类动物共存，部分区域内其种群密度已达较高水平。该公园的诸多区域内，地中海森林（Mediterranean forest）的更新进程受限，其成因包括地下水位下降、病虫害影响以及大型有蹄类动物的作用。此类森林更新不良，对其维系的生物多样性及其提供的生态系统服务构成威胁。本研究借助15年前布设的一系列围栏样地（exclosures）——这些围栏对原本设计排除的有蹄类动物而言，其通透性逐渐提升——探究有蹄类动物对多尼亚纳国家公园内地中海林地植被的短期与长期影响。具体而言，本研究聚焦三大核心维度：(1) 植物受损与取食状况；(2) 幼树密度（即更新状况）；以及(2) 植株体型（即定植与生长情况）。我们观察到，当家养草食动物（herbivores）的相对丰度处于中等或较高水平时，植株枝条会出现显著的受损与啃食现象，且该效应呈线性变化趋势。与之形成对比的是，野生草食动物的影响随其丰度上升而增强，但在较高密度下往往趋于饱和，部分情境下甚至会出现效应下降的情况。我们未观察到草食动物对各类物种幼树密度产生明确且一致的影响，这大概率源于调查发现的幼树样本量极低（n=62），或可表明围栏样地内所研究物种的更新率极低。关于幼龄植株的定植与生长状况，在草食动物历史出现频率较高的区域，植株平均高度与冠幅（canopy size）及其变异程度普遍更低。随着气候变化（climate change），本研究观测到的草食作用（herbivory）对地中海森林生态系统的负面影响或会进一步加剧。持续探究草食动物与该公园生态系统间的生态相互作用，实属必要之举。此类研究成果可用于制定管理策略，以平衡畜牧生产、野生动物保护以及地中海生态系统应对气候变化的韧性。