Data from: Do grazing intensity and herbivore type affect soil health? Insights from a semi-arid productivity gradient

Grazing is one of the most widespread forms of intensive management on Earth and is linked to reductions in soil health. However, little is known about the relative influence of herbivore type, herbivore intensity and site productivity on soil health. This lack of knowledge reduces our capacity to manage landscapes where grazing is a major land use.
We used structural equation modelling to assess the effects of recent (cattle, sheep, goats, kangaroos and rabbit dung) and historic (cattle, sheep/goat livestock tracks) herbivore activity on soil health at 451 sites across 0·5 M km2 of eastern Australia. We assessed the direct and indirect effects of increasing herbivore intensity, using dung and livestock tracks, on 15 morphological, physical and chemical attributes that are indicative of soil health, and we used these attributes to derive three indices representing the capacity of the soil to maintain its structural integrity (stability), cycle nutrients (nutrients) and maintain water flow (infiltration).
Grazing had negative effects on the three soil health indices, but these effects varied with productivity. Grazing intensity was associated with strong reductions in the stability and nutrient indices under low productivity, but these effects diminished with increasing productivity. Herbivore effects on individual attributes varied in relation to productivity level and were strongly herbivore specific, with most due to cattle grazing, and to a lesser extent, sheep, goats and rabbits. Few effects due to kangaroos or historic grazing by livestock were observed.
Synthesis and applications. Our study shows that livestock and rabbits degrade soil health through grazing, and its effects are strongest under low or moderate productivity; however, kangaroo effects are benign. Our findings support calls for resource management agencies to consider site productivity, as well as herbivore type and intensity, when developing strategies to manage grazing by livestock, and feral and native herbivores.

放牧是全球分布最广的集约化土地管理模式之一，且与土壤健康退化密切相关。然而，目前学界对草食动物类型、放牧强度以及生境生产力对土壤健康的相对影响仍缺乏系统认知。这一认知缺口制约了我们对以放牧为核心土地利用方式的景观开展有效管理的能力。

本研究针对澳大利亚东部0.5百万平方公里范围内的451个采样位点，采用结构方程模型（structural equation modelling），评估了近期（牛、羊、山羊、袋鼠及兔类粪便）与历史（牛、羊/山羊牲畜足迹）草食动物活动对土壤健康的影响。研究以粪便与牲畜足迹表征放牧强度，分析了放牧强度提升对15项可指示土壤健康状况的形态、物理及化学属性的直接与间接效应；并基于这些属性构建了三项土壤健康指数，分别反映土壤维持结构完整性（稳定性）、循环养分（养分循环）以及保障水分运移（入渗能力）的功能。

放牧对三项土壤健康指数均产生负面影响，但该效应随生境生产力水平呈现显著差异。在低生产力生境中，放牧强度提升与土壤稳定性及养分循环指数的显著下降密切相关，但该效应随生产力提升逐渐减弱。草食动物对单项土壤属性的影响既与生境生产力水平相关，也具有极强的物种特异性：多数影响源自牛的放牧活动，其次为羊、山羊与兔类；袋鼠以及历史牲畜放牧活动产生的土壤健康影响则相对微弱。

研究总结与应用启示。本研究表明，家畜与兔类通过放牧活动损害土壤健康，且该损害在低或中等生产力生境中最为显著；而袋鼠的放牧活动对土壤健康无明显负面影响。本研究结果支持资源管理机构在制定家畜、野生化与本土草食动物的放牧管理策略时，需同时考量生境生产力、草食动物类型与放牧强度的呼吁。