Data from: An insect ecosystem engineer alleviates drought stress in plants without increasing plant susceptibility to an above-ground herbivore

Climate change models predict more extreme rainfall patterns, ranging from droughts to deluges, which will inevitably affect primary productivity in many terrestrial ecosystems. Insects within the ecosystem, living above- and below-ground, may modify plant responses to water stress. For example, some functional groups improve soil conditions via resource provision, potentially alleviating water stress. Enhanced resource provision may, however, render plants more susceptible to herbivores and negate beneficial effects. Using a model system, we tested how plants (Brassica oleracea) responded to drought, ambient and increased precipitation scenarios when interacting with both a soil conditioning ecosystem engineer (dung beetles; Bubas bison) and an above-ground herbivore, the major crop pest diamondback moth (Plutella xylostella). Dung beetles enhanced soil water retention by 10% and promoted growth in plants subjected to drought by 280%, relieving the impacts of water stress on plants. Under drought conditions, plants grown with dung beetles had c. 30% more leaves and were over twice as tall as those without dung beetles. Dung beetles produced a 2·7-fold increase in nitrogen content and more than a threefold increase in carbon content of the shoots, though shoot concentrations of nitrogen and carbon were unchanged. Carbon concentrations in roots, however, were increased by dung beetles under both ambient and increased precipitation regimes. Increased precipitation reduced root and shoot nitrogen concentrations by 16% and 30%, relative to plants under ambient regimes, respectively, most likely due to dilution effects of increased plant growth under increased precipitation. Soil carbon and nitrogen concentrations were largely unaffected. While dung beetles enhanced plant growth and nitrogen content in plants experiencing drought, the anticipated increase in plant suitability to herbivores did not arise, possibly because shoot nitrogen concentrations and C:N ratio were unaffected. To our knowledge, this is the first report of an insect ecosystem engineer alleviating the effects of predicted drought events on plants via physical manipulation of the soil matrix. Moreover, their effects did not change plant suitability to an above-ground herbivore, pointing to potential beneficial role for insect ecosystem engineers in climate change adaptation and crop protection.

气候变化模型预测，极端降雨格局将愈发频发，范围涵盖干旱与洪涝，这势必会对众多陆地生态系统的初级生产力造成影响。栖息于陆地生态系统地上与地下的昆虫，或可改变植物对水分胁迫的响应。例如，部分功能群可通过资源供给改善土壤条件，潜在缓解水分胁迫；然而，强化的资源供给或使植物更易遭受植食者侵害，进而抵消其有益效应。
本研究依托模式实验系统，测试了甘蓝（Brassica oleracea）在干旱、自然对照及增水三种降水情景下，与土壤调控型生态系统工程师蜣螂（dung beetles, Bubas bison）以及地上植食者、主要作物害虫小菜蛾（Plutella xylostella）共同互作时的响应情况。结果显示，蜣螂可将土壤持水性提升10%，并使经受干旱胁迫的植物生物量增长280%，缓解了水分胁迫对植物的负面影响。在干旱条件下，与蜣螂共培养的植物叶片数较无蜣螂组多约30%，株高更是达到后者的两倍以上。蜣螂使植物地上部分的氮含量提升至原来的2.7倍，碳含量提升至三倍以上，但地上部分的氮、碳浓度并未发生改变。而在自然对照与增水两种降水情景下，蜣螂均使根系碳浓度有所提升。
相较于自然降水处理组，增水处理分别使植物根系与地上部分的氮浓度降低16%与30%，这大概率是增水下植物生长加速导致的稀释效应所致。土壤碳、氮浓度则基本未受影响。
尽管蜣螂可提升干旱胁迫下植物的生长速率与氮含量，但其预期的植物对植食者适宜性提升并未出现，这可能是因为地上部分的氮浓度与碳氮比并未发生改变。据我们所知，本研究首次报道了昆虫生态系统工程师通过物理改造土壤基质，缓解了预测中的干旱事件对植物造成的影响。此外，蜣螂的作用并未改变植物对地上植食者的适宜性，这表明昆虫生态系统工程师在气候变化适应与作物保护领域或具备潜在的有益作用。