Wildlife Ecology & Health group (WE&H), Servei d'Ecopatologia de Fauna Salvatge (SEFaS), Departament de Medicina i Cirurgia Animals, Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain.
Departamento de Biología (Botánica), Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Universidad Autónoma de Madrid, Spain; CREAF, Cerdanyola del Vallès, Spain.
Sci Total Environ. 2022 Apr 20;818:151771. doi: 10.1016/j.scitotenv.2021.151771. Epub 2021 Nov 20.
Alpine grasslands are essential for carbon sequestration and food supply for domestic and wild herbivores inhabiting mountainous areas worldwide. These biomes, however, are alternatively threatened by the abandonment of agricultural and livestock practices leading to a fast-growing shrubification process while other mountain grasslands are suffering from the impacts of overgrazing. The functioning of alpine meadow ecosystems is primarily driven by climatic conditions, land-use legacies and grazing. However, although it is critically important, the role of large herbivores on the aboveground biomass and protein content of palatable plants is poorly understood for most alpine meadows. In this work, we explore the effects of grazing on grassland vegetation at two different spatial and temporal scales in the Eastern Pyrenees, Spain. Remote sensing was used to assess the effect of high and moderate grazing (HG and MG respectively) on grass biomass using the leaf area index (LAI) at the meso-scale (patches between 2.3 and 38.7 ha). We also explored the impact of null (NG), overgrazing (MO, mimicked overgrazing) and high (HG) grazing intensities at local scale setting eighteen 1 m exclusion boxes in six meadows (three boxes each) commonly used by domestic and wild ungulates. Historical satellite data showed that LAI values are greater in high than in low grazed areas (HG, mean = 0.66, LG, mean = 0.55). Along the same lines, high and moderate grazing pressures improved biomass production at the local-scale (HG, mean = 590.3 g/m, MO, mean = 389.3 g/m and NG, mean = 110.8 g/m). Crude protein content reached higher values under MO pressure than under HG pressure. Our results confirm that grazing intensity exerts significant changes on the above-ground biomass production and the protein content of plants consumed by domestic (cattle and horses) and wild ungulates (Southern Chamois, Rupicapra pyrenaica). We can conclude that ungulates sustain biomass and nutritive values of grass exerting a negligible effect on biomass and protein content of woody vegetation. Our results will inform management guidelines to support profitable grazing activities and promote conservation of the open landscapes in the alpine ecosystems under the current global change scenario.
高山草原对于全球山区的碳固存和家养及野生草食动物的食物供应至关重要。然而，这些生物群落也受到农业和畜牧业废弃的交替威胁，导致快速的灌木化过程，而其他山地草原则受到过度放牧的影响。高山草甸生态系统的功能主要受气候条件、土地利用遗留问题和放牧的驱动。然而，尽管这一点至关重要，但大型食草动物对高山草甸中可食用植物地上生物量和蛋白质含量的影响在大多数情况下仍知之甚少。在这项工作中，我们在西班牙比利牛斯山脉的两个不同的时空尺度上探索了放牧对草原植被的影响。利用中尺度（斑块面积在 2.3 到 38.7 公顷之间）的叶面积指数（LAI），遥感用于评估高（HG）和中度（MG）放牧对草本生物量的影响。我们还在小尺度上（设置了 18 个 1 米的排除框，放置在六个常见的家养和野生有蹄类动物使用的草地上，每个草地 3 个）探索了零（NG）、过度放牧（MO，模拟过度放牧）和高（HG）放牧强度对草地植被的影响。历史卫星数据表明，高放牧区的 LAI 值大于低放牧区（HG，均值=0.66，LG，均值=0.55）。同样，高和中度放牧压力提高了小尺度上的生物量生产（HG，均值=590.3 g/m，MO，均值=389.3 g/m 和 NG，均值=110.8 g/m）。在 MO 压力下，粗蛋白含量达到较高水平。我们的研究结果证实，放牧强度对植物地上生物量和家养（牛和马）和野生有蹄类动物（南方盘羊，Rupicapra pyrenaica）食用植物的蛋白质含量产生显著影响。我们可以得出结论，有蹄类动物维持着生物量和营养价值的草，对木本植被的生物量和蛋白质含量几乎没有影响。我们的研究结果将为管理指南提供信息，以支持有利可图的放牧活动，并在当前的全球变化情景下促进高山生态系统开阔景观的保护。
