Departamento de Sistemas y Recursos Naturales, Universidad Politécnica de Madrid, Ciudad Universitaria, s/n, 28040 Madrid, Spain.
Departamento de Sistemas y Recursos Naturales, Universidad Politécnica de Madrid, Ciudad Universitaria, s/n, 28040 Madrid, Spain; Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA 94305, USA.
J Environ Manage. 2018 Jan 15;206:642-649. doi: 10.1016/j.jenvman.2017.11.007. Epub 2017 Nov 10.
Wild ungulate populations have increased and expanded considerably in many regions, including austral woodlands and forests where deer (Cervus elaphus) have been introduced as an alternative management to traditional cattle grazing. In this study, we compared traditional cattle with introduced deer management at increasing deer densities in the "Chaco Serrano" woodlands of Argentina to assess their ecological sustainability. We used three ecological indicators (abundance of tree regeneration, woody plant diversity and browsing damage) as proxies for environmental sustainability in woody systems. Our results indicate that traditional cattle management, at stocking rates of ∼10 ind km, was the most ecologically sustainable management since it allowed greater tree regeneration abundance, higher richness of woody species and lower browsing damage. Importantly, cattle management and deer management at low densities (10 ind km) showed no significant differences in species richness and abundance of seedlings, although deer caused greater browsing damage on saplings and juveniles. However, management regimes involving high deer densities (∼35 deer km) was highly unsustainable in comparison to low (∼10 deer km) and medium (∼20 deer km) densities, with 40% probability of unsustainable browsing as opposed to less than 5% probability at low and medium densities. In addition, high deer densities caused a strong reduction in tree regeneration, with a 19-30% reduction in the abundance of seedlings and young trees when compared to low deer densities. These results showed that the effect of increasing deer densities on woody plant conservation was not linear, with high deer densities causing a disproportional deleterious effect on tree regeneration and sustainable browsing. Our results suggest that traditional management at low densities or the use of introduced ungulates (deer breeding areas) at low-medium densities (<20 deer km) are compatible with woody vegetation conservation. However, further research is needed on plant palatability, animal habitat use (spatial heterogeneity) and species turnover and extinction (comparison to areas of low-null historical browsing) to better estimate environmental sustainability of Neotropical ungulate-dominated woodlands.
野生动物种群在许多地区（包括澳大利亚的林地和森林）大量增加和扩张，在这些地区，鹿（Cervus elaphus）被引入作为传统牛放牧的替代管理方式。在这项研究中，我们比较了在阿根廷“查科塞拉诺”林地中增加鹿密度时传统的牛管理和引入的鹿管理，以评估它们的生态可持续性。我们使用了三个生态指标（树木再生的丰度、木本植物多样性和啃食损害）作为木本系统环境可持续性的替代指标。我们的结果表明，在 10 头/km 的放牧率下，传统的牛管理是最具生态可持续性的管理方式，因为它允许更多的树木再生丰度、更高的木本物种丰富度和更低的啃食损害。重要的是，在低密度（10 头/km）时，牛管理和鹿管理在物种丰富度和幼苗丰度上没有显著差异，尽管鹿对幼树和幼树造成了更大的啃食损害。然而，与低密度（约 10 头/km）和中密度（约 20 头/km）相比，涉及高密度（约 35 头/km）鹿的管理模式极不可持续，40%的可能性是不可持续的啃食，而在低密度和中密度下，可能性小于 5%。此外，高密度的鹿导致树木再生的强烈减少，与低密度的鹿相比，幼苗和小树的数量减少了 19-30%。这些结果表明，增加鹿密度对木本植物保护的影响不是线性的，高密度的鹿对树木再生和可持续啃食造成了不成比例的有害影响。我们的结果表明，在低密度下进行传统管理，或在低密度至中密度（<20 头/km）下使用引入的有蹄类动物（鹿繁殖区），与木本植被保护是兼容的。然而，需要进一步研究植物适口性、动物栖息地利用（空间异质性）和物种更替和灭绝（与历史低-零啃食地区相比），以更好地估计新热带有蹄类动物占主导地位的林地的环境可持续性。
