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This study is a global meta-analysis of the effects of grassland plant species richness on aboveground and belowground carbon and nitrogen dynamics. Observations from 73 studies in grasslands totaling 1385 paired observations of plant mixtures and monocultures were compiled. Response variables included nine carbon and six nitrogen processes to plant diversity, examined the effects of experimental types and age on the responses, and predicted the carbon and nitrogen balance following different biodiversity loss scenario in grasslands. We found that carbon and nitrogen functions significantly enhanced in plant mixtures, but varied with experimental types. Most of the attributes was significantly correlated with species richness and experimental age, the relationship between species richness and carbon and nitrogen processes was interacted with experimental duration in the field experiments, except for soil respiration, fungal biomass, and soil nitrate nitrogen. Importantly, our results showed that the declines in soil carbon and nitrogen pool accelerated following plant diversity loss. Our meta-analysis revealed that the plant diversity has ubiquitous impacts on carbon and nitrogen cycles in grasslands, likely driven by complementarity effects of plant diversity on plant productivity and biomass, underlined interactive effects of plant diversity, experimental types and age, and climate on carbon and nitrogen processes, and suggested that the reduction in carbon and nitrogen stocks in grasslands will be larger following biodiversity loss in the future.

Integrated vegetation management programs have successfully reduced the frequency and intensity of power line right-of-way management by promoting low-growing plant communities resistant to tree invasion. To examine whether these principles are transferable to northern ecosystems, researchers tested eight treatments at four sites in Yukon, Canada. Two herbicides, imazapyr and triclopyr, were applied by three methods, as well as a native grass seeding treatment and a mowing control. Vegetation cover was recorded prior to treatment and after one year along with herbicide damage assessments. Overall, treatments caused significant changes to vascular plant communities after one year. Short-term control of woody target species was greater in chemically-treated plots (66%–94%) than with mechanical methods (<55%). All treatments caused a minor reduction in non-target vegetation cover. In seeded plots, seedlings emerged but total non-target species cover was reduced by seedbed preparation. Triclopyr broadcast spray reduced non-target vegetation cover by <10%, but the common shrub, kinnickinnick (Arctostaphylos uva-ursi), was highly impacted. Selective application of triclopyr effectively controlled targets with minimal effects on non-target species. Imazapyr consistently caused more impacts to non-target plants than triclopyr. Both selective and non-selective imazapyr applications resulted in chlorosis, stunting, and deformity of shrubs and forbs one year after treatment. This suggests imazapyr can remain active in northern soils for at least 365 days as well as transfer to untreated plants. The range of sensitivities of boreal plant species to imazapyr and triclopyr and potential persistence in northern soils highlights the need for focused toxicity research in the North.