Extensive livestock grazing is a global human activity. In the Iberian Peninsula, extensive grazing and seminatural grasslands and open woodlands such as dehesas have co-evolved with human use for millennia. However, social, demographic, and economic factors are now pushing this traditional activity towards both conventional intensification and land abandonment, with consequences for the biodiversity and functioning of these seminatural ecosystems. Soils can be particularly affected by grazing abandonment due to the cessation of inputs of pre-processed organic matter (dungs and urine) and of trampling, with still poorly understood consequences for the composition, network configuration, and activity of soil microbial communities and the capacity of soils to store C. In this work, we used 20 pairs of adjacent plots (40 plots in total) located in seminatural grasslands from central Spain. For each pair, one plot was extensively grazed by livestock and the other one was abandoned. We evaluated the effects of extensive grazing abandonment on soil fertility (C and N contents, and P and K bioavailability), forage quality (fibre and protein content), and soil microbial community composition (amplicon sequencing of 16 S [bacteria] and ITS [fungi]), network coupling, and activity (extracellular hydrolytic enzymes linked to the biogeochemical cycling of C, N, P, and S). Grazing resulted in higher soil fertility in terms of C, N, and P, and grassland forage quality (lower fibre). Grazing also affected soil microbial community composition, but not richness or diversity. These effects occurred primarily through changes in nutrients and soil water availability. Actinobacteria significantly increased in abandoned plots, while Acidobacteria, Verrucomicrobia, and Planctomycetes decreased. Bacterial and, particularly, fungal networks were generally less coupled in abandoned plots. Furthermore, grazing resulted in greater soil enzyme activity via direct effects. These results support the notion that extensive grazing with intermediate stocking rates provides a positive effect on grass quality, soil fertility, nutrient cycling, and microbial network configuration, and thus warn about the potential negative effects of land abandonment.

中文翻译：

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放弃传统的牲畜放牧会降低土壤肥力和酶活性，改变土壤微生物群落，并使微生物网络脱钩，从而影响地中海草原的饲料质量

广泛的牲畜放牧是一项全球性的人类活动。在伊比利亚半岛，大面积的放牧和半自然草原以及德赫萨斯等开阔林地与人类的利用共同进化了数千年。然而，社会、人口和经济因素现在正在推动这种传统活动走向传统集约化和土地废弃，从而对这些半自然生态系统的生物多样性和功能产生影响。由于停止输入预处理的有机物（粪便和尿液）和践踏，土壤尤其容易受到放牧的影响，而对土壤微生物群落的组成、网络结构和活动以及能力的影响仍然知之甚少。在这项工作中，我们使用了位于西班牙中部半自然草原的 20 对相邻地块（总共 40 块地块）。对于每一对来说，一块地被牲畜广泛放牧，另一块则被遗弃。我们评估了大面积放牧对土壤肥力（碳和氮含量、磷和钾生物利用率）、饲料质量（纤维和蛋白质含量）和土壤微生物群落组成（16 S [细菌]和 ITS 的扩增子测序）的影响。真菌]）、网络耦合和活性（与 C、N、P 和 S 生物地球化学循环相关的细胞外水解酶）。放牧提高了土壤的碳、氮和磷肥力，以及草地饲料质量（较低的纤维）。放牧还影响土壤微生物群落的组成，但不影响丰富度或多样性。这些影响主要是通过养分和土壤水分可用性的变化而发生的。废弃地块中放线菌显着增加，而酸杆菌、疣微菌和浮霉菌则减少。在废弃的地块中，细菌网络，尤其是真菌网络的耦合度通常较低。此外，放牧通过直接影响导致土壤酶活性增强。这些结果支持这样的观点，即中等载畜率的广泛放牧对草质、土壤肥力、养分循环和微生物网络配置产生积极影响，从而对土地撂荒的潜在负面影响提出警告。