Effect of paralleled grazing and mowing on stoichiometric linkages and insect community composition in semi-arid grassland

As the two major management practices for grasslands, livestock grazing and mowing greatly influence the soil-plant-insect cascading effects, which can be reflected by their associations in stoichiometry. While previous studies have investigated the effect of grazing or moving on plants, soils and insects in grasslands, few have purposely made a sound comparison between the effects of paralleled grazing and mowing on soil-plant-insect stoichiometric linkages and insect community composition in a semi-arid grassland. In a four year field manipulative experiment, we investigated how paralleled grazing and mowing affect C:N:P stoichiometric linkages among soil, dominant plant (Leymus chinensis) and dominant insect herbivore (Euchorthippus grasshopper), as well as insect community composition in a semi-arid grassland in northeastern China. We noted that grazing significantly increased soil and plant total N concentration but decreased their C:N, whereas both grazing and mowing failed to affect C:N:P stoichiometry of grasshoppers. Our results uphold the concept that organisms at higher trophic levels exhibit higher elemental homeostasis against disturbances. The total abundance and species evenness of insects were not affected, whereas grazing significantly increased insect species richness by 17 % compared to mowing. Mowing reduced predator insect abundance by 27 %, whereas grazing increased detritivore insect abundance by 18 %. Our study suggests that cattle grazing is better than mowing in terms of improving soil and plant nutrient and diversifying insects (beneficial in most cases), but longer-term investigations are needed to study the effects of paralleled grazing and mowing on stoichiometric linkages and insect community composition in grasslands.