Department of Agronomy, Hetao College, Bayannur, Inner Mongolia, China.
Department of Agronomy, Horticulture and Plant Sciences, South Dakota State University, Brookings, South Dakota, United States of America.
PLoS One. 2020 Aug 7;15(8):e0236638. doi: 10.1371/journal.pone.0236638. eCollection 2020.
Grazing effects on soil properties under different soil and environmental conditions across the globe are often controversial. Therefore, it is essential to evaluate the overall magnitude and direction of the grazing effects on soils. This global meta-analysis was conducted using the mixed model method to address the overall effects of grazing intensities (heavy, moderate, and light) on 15 soil properties based on 287 papers published globally from 2007 to 2019. Our findings showed that heavy grazing significantly increased the soil BD (11.3% relative un-grazing) and PR (52.5%) and reduced SOC (-10.8%), WC (-10.8%), NO3- (-23.5%), and MBC (-27.9%) at 0-10 cm depth, and reduced SOC (-22.5%) and TN (-19.9%) at 10-30 cm depth. Moderate grazing significantly increased the BD (7.5%), PR (46.0%), and P (18.9%) (0-10 cm), and increased pH (4.1%) and decreased SOC (-16.4%), TN (-10.6%), and P (-23.9%) (10-30 cm). Light grazing significantly increased the SOC (10.8%) and NH4+ (28.7%) (0-10 cm). Heavy grazing showed much higher mean probability (0.70) leading to overgrazing than the moderate (0.14) and light (0.10) grazing. These findings indicate that, globally, compared to un-grazing, heavy grazing significantly increased soil compaction and reduced SOC, NO3-, and soil moisture. Moderate grazing significantly increased soil compaction and alkalinity and reduced SOC and TN. Light grazing significantly increased SOC and NH4+. Cattle grazing impacts on soil compaction, SOC, TN, and available K were higher than sheep grazing, but lower for PR. Climate significantly impacted grazing effects on SOM, TN, available P, NH4+, EC, CEC, and PR. Heavy grazing can be more detrimental to soil quality based on BD, SOC, TN, C: N, WC, and K than moderate and light grazing. However, global grazing intensities did not significantly impact most of the 15 soil properties, and the grazing effects on them had insignificant changes over the years.
放牧对全球不同土壤和环境条件下土壤性质的影响往往存在争议。因此，评估放牧对土壤的综合影响幅度和方向至关重要。本全球荟萃分析采用混合模型方法，基于 2007 年至 2019 年全球发表的 287 篇论文，评估了放牧强度（重度、中度和轻度）对 15 种土壤性质的综合影响。我们的研究结果表明，重度放牧显著增加了土壤容重（相对未放牧增加 11.3%）和团聚体稳定性（增加 52.5%），并降低了土壤有机碳（SOC）（减少 10.8%）、含水量（WC）（减少 10.8%）、硝态氮（NO3-）（减少 23.5%）和微生物生物量碳（MBC）（减少 27.9%），在 0-10 厘米深度，SOC（减少 22.5%）和总氮（TN）（减少 19.9%）在 10-30 厘米深度。中度放牧显著增加了土壤容重（增加 7.5%）、团聚体稳定性（增加 46.0%）和磷（增加 18.9%）（0-10 厘米），并增加了 pH 值（增加 4.1%）和降低了 SOC（减少 16.4%）、TN（减少 10.6%）和磷（减少 23.9%）（10-30 厘米）。轻度放牧显著增加了 SOC（增加 10.8%）和铵态氮（NH4+）（增加 28.7%）（0-10 厘米）。重度放牧的平均概率（0.70）明显高于中度（0.14）和轻度（0.10）放牧，导致过度放牧的可能性更高。这些发现表明，与未放牧相比，全球范围内，重度放牧显著增加了土壤紧实度，降低了 SOC、NO3-和土壤水分。中度放牧显著增加了土壤紧实度和碱性，降低了 SOC 和 TN。轻度放牧显著增加了 SOC 和 NH4+。牛放牧对土壤紧实度、SOC、TN 和有效钾的影响大于绵羊放牧，但对 PR 的影响较小。气候显著影响放牧对 SOM、TN、有效磷、NH4+、EC、CEC 和 PR 的影响。基于 BD、SOC、TN、C:N、WC 和 K，重度放牧对土壤质量的不利影响大于中度和轻度放牧。然而，全球放牧强度并没有显著影响 15 种土壤性质中的大多数，而且这些性质的放牧影响在这些年内没有显著变化。
