Department of Ecology, Swedish University of Agricultural Sciences, 75007, Uppsala, Sweden.
Sci Rep. 2020 Jul 29;10(1):12752. doi: 10.1038/s41598-020-69696-3.
Herbivorous insects can influence grassland ecosystem functions in several ways, notably by altering primary production and nutrient turnover. Interactions between above- and belowground herbivory could affect these functions; an effect that might be modified by nitrogen (N) addition, an important global change driver. To explore this, we added above- (grasshoppers) and belowground (wireworms) insect herbivores and N into enclosed, equally composed, grassland plant communities in a fully factorial field experiment. N addition substantially altered the impact of above- and belowground herbivory on ecosystem functioning. Herbivory and N interacted such that biomass was reduced under above ground herbivory and high N input, while plant biomass remained stable under simultaneous above- and belowground herbivory. Aboveground herbivory lowered nutrient turnover rate in the soil, while belowground herbivory mitigated the effect of aboveground herbivory. Soil decomposition potential and N mineralization rate were faster under belowground herbivory at ambient N, but at elevated N this effect was only observed when aboveground herbivores were also present. We found that N addition does not only influence productivity directly (repeatedly shown by others), but also appears to influence productivity by herbivory mediated effects on nutrient dynamics, which highlights the importance of a better understanding of complex biotic interactions.
食草昆虫可以通过多种方式影响草原生态系统功能，特别是通过改变初级生产力和养分周转率。地上和地下食草动物之间的相互作用可能会影响这些功能；这种影响可能会被氮（N）添加所改变，氮添加是一种重要的全球变化驱动因素。为了探索这一点，我们在一个完全因子野外实验中，将食草昆虫（蚱蜢）和地下食草动物（地老虎）以及 N 添加到封闭的、成分相同的草原植物群落中。N 添加大大改变了地上和地下食草动物对生态系统功能的影响。食草动物和 N 之间存在相互作用，以至于在地上食草动物和高 N 输入下，生物量减少，而在同时存在地上和地下食草动物的情况下，植物生物量保持稳定。地上食草动物降低了土壤中的养分周转率，而地下食草动物减轻了地上食草动物的影响。在大气氮下，地下食草动物会加快土壤分解潜力和氮矿化率，但在高氮下，只有当地上食草动物也存在时，才会观察到这种效果。我们发现，N 添加不仅直接影响生产力（这一点已被其他人多次证明），而且似乎还通过食草动物对养分动态的介导作用来影响生产力，这凸显了更好地理解复杂生物相互作用的重要性。
