Habitat attributes similarities reduce impacts of land-use conversion on seed removal

Changes in land use strongly influence habitat attributes (e.g., herbaceous ground cover and tree richness) and can consequently affect ecological functions. Most studies have focused on the response of these ecological functions to land-use changes within only a single vegetation type. These studies have often focused solely on agricultural conversion of forests, making it nearly impossible to draw general conclusions across other vegetation types or with other land use changes (e.g., afforestation). We examined the consequences of agricultural conversion for seed removal by ants in native grassland, savanna, and savanna-forest habitats that had been converted to planted pastures (Brachiaria decumbens) and tree plantations (Eucalyptus spp.) and explored if changes in seed removal were correlated with differences in habitat attributes between habitat types. We found that land-use changes affected seed removal across the tree cover gradient and that the magnitude of impact was influenced by similarity in habitat attributes between native and converted habitats, being greater where there was afforestation (Eucalyptus spp in grassland and savanna). Herbaceous ground cover, soil hardness, and tree richness were the most important habitat attributes that correlated with differences in seed removal. Our results reveal that the magnitude of impact of land-use changes on seed removal varies depending on native vegetation type and is associated with the type of habitat attribute change. Our findings have implications for biodiversity in tropical grassy systems: afforestation can have a greater detrimental impact on ecological function than tree loss.

土地利用变化可显著改变栖息地属性（如草本地表覆盖度、树木物种丰富度），进而对生态功能产生影响。现有多数研究仅聚焦于单一植被类型内生态功能对土地利用变化的响应。这类研究往往仅聚焦于森林向农业用地的转化，导致几乎无法在其他植被类型或其他土地利用变化（如造林）情境下得出普适性结论。本研究针对原生草原、稀树草原及稀树草原林三种原生栖息地，探究其被转化为臂形草（*Brachiaria decumbens*）人工牧场与桉属（*Eucalyptus* spp.）人工林后，蚂蚁介导的种子移除过程所受的影响；同时探讨种子移除的变化是否与不同栖息地类型间的栖息地属性差异存在关联。研究结果显示，土地利用变化对沿树木覆盖梯度的各类生境的种子移除均产生影响，且影响程度受原生栖息地与转化后栖息地的属性相似度调控：在造林场景（草原与稀树草原转为桉属人工林）中，影响更为显著。草本地表覆盖度、土壤硬度与树木物种丰富度是与种子移除差异关联最为紧密的关键栖息地属性。本研究结果表明，土地利用变化对种子移除的影响程度因原生植被类型而异，且与栖息地属性的变化类型密切相关。本研究结果对热带草本生态系统的生物多样性保护具有启示意义：相较于林木丧失，造林活动对生态功能的负面影响可能更为强烈。