Data from: Land-use history alters contemporary insect herbivore community composition and decouples plant-herbivore relationships

1. Past land use can create altered soil conditions and plant communities that persist for decades, although the effects of these altered conditions on consumers are rarely investigated. 2. Using a large-scale field study at 36 sites in longleaf pine (Pinus palustris) woodlands, we examined whether historic agricultural land use leads to differences in the abundance and community composition of insect herbivores (grasshoppers, families Acrididae and Tettigoniidae). 3. We measured the cover of six plant functional groups and several environmental variables to determine whether historic agricultural land use affects the relationships between plant cover or environmental conditions and grasshopper assemblages. 4. Land-use history had taxa-specific effects and interacted with herbaceous plant cover to alter grasshopper abundances, leading to significant changes in community composition. Abundance of most grasshopper taxa increased with herbaceous cover in woodlands with no history of agriculture, but there was no relationship in post-agricultural woodlands. We also found that grasshopper abundance was negatively correlated with leaf litter cover. Soil hardness was greater in post-agricultural sites (i.e. more compacted) and was associated with grasshopper community composition. Both herbaceous cover and leaf litter cover are influenced by fire frequency, suggesting a potential indirect role of fire on grasshopper assemblages. 5. Our results demonstrate that historic land use may create persistent differences in the composition of grasshopper assemblages, while contemporary disturbances (e.g. prescribed fire) may be important for determining the abundance of grasshoppers, largely through the effect of fire on plants and leaf litter. Therefore, our results suggest that changes in the contemporary management regimes (e.g. increasing prescribed fire) may not be sufficient to shift the structure of grasshopper communities in post-agricultural sites towards communities in non-agricultural habitats. Rather, repairing degraded soil conditions and restoring plant communities are likely necessary for restoring grasshopper assemblages in post-agricultural woodlands.1. 既往土地利用活动可改变土壤状况与植物群落结构，且此类改变效应可延续数十年之久；然而，这类改变对消费者类群的影响却鲜有研究。2. 本研究针对长叶松（Pinus palustris）林的36个样地开展大规模野外调查，旨在探究历史农业土地利用是否会导致植食性昆虫（蝗虫，涵盖蝗科Acrididae与螽斯科Tettigoniidae）的种群丰度与群落组成出现差异。3. 本研究测定了6种植物功能群的盖度及多项环境变量，以明确历史农业土地利用是否会调控草本盖度、环境状况与蝗虫群落之间的关联模式。4. 土地利用历史对蝗虫类群具有类群特异性效应，且会与草本植物盖度产生交互作用，进而改变蝗虫种群丰度，最终导致群落组成发生显著变化。在无农业利用历史的林地中，多数蝗虫类群的丰度随草本盖度升高而增加，但在经农业开垦后的林地中，二者并无显著关联。本研究还发现，蝗虫丰度与枯落物盖度呈负相关关系。农业后样地的土壤硬度更高（即土壤更紧实），且该特征与蝗虫群落组成存在关联。草本盖度与枯落物盖度均受火烧频率影响，这表明火烧可能通过间接途径对蝗虫群落发挥作用。5. 本研究结果证实，历史土地利用可对蝗虫群落组成造成持久改变；而当代干扰（如计划火烧）则可能主要通过影响植物与枯落物覆盖度，进而调控蝗虫的种群丰度。因此，仅通过调整当代管理措施（如增加计划火烧频次），或不足以将农业后样地的蝗虫群落结构恢复至非农业生境中的状态。相较而言，修复退化的土壤条件与重建植物群落，或是恢复农业后林地蝗虫群落的必要手段。