Alpine grassland degradation intensifies the burrowing behavior of small mammals:evidence for a negative feedback loop

Globally,grassland degradation is an acute ecological problem.In alpine grassland on the Tibetan Plateau,increased densities of various small mammals in degraded grassland are assumed to intensify the degradation process and these mammals are subject to lethal control.However,whether the negative impact of small mammals is solely a result of population size or also a result of activity and behavior has not been tested.In this study,we use plateau pika as a model to compare population size,core area of colony,and the number of burrow entrances and latrines between lightly and severely degraded grassland.We test whether the alleged contribution of pika to grassland degradation is a result of increased population size or increased burrowing activities of individuals in response to lower food abundance.We found that grassland degradation resulted in lower plant species richness,plant height,and biomass.Furthermore,the overall population size of pika was not significantly affected by location in lightly and severely degraded grassland.However,pika core areas in severely grassland degradation were significantly larger and had significantly higher densities of burrows and latrines.Our study provides convincing evidence that habitat-induced changes in the behavior of small,burrowing mammals,such as pika,can exacerbate grassland degradation.This finding has significant implications for managing small mammals and restoring degraded grassland ecosystems.

Bioaccumulation and effects of sediment-associated gold-and graphene oxide nanoparticles on Tubifex tubifex

With the development of nanotechnology,gold（Au） and graphene oxide（GO） nanoparticles have been widely used in various fields,resulting in an increased release of these particles into the environment.The released nanoparticles may eventually accumulate in sediment,causing possible ecotoxicological effects to benthic invertebrates.However,the impact of Au-NPs and GO-NPs on the cosmopolitan oligochaete,Tubifex tubifex,in sediment exposure is not known.Mortality,behavioral impact（GO-NP and Au-NP） and uptake（only Au-NP） of sediment-associated Au-NPs（4.9±0.14 nm） and GO-NPs（116±0.05 nm） to T.tubifex were assessed in a number of 5-day exposure experiments.The results showed that the applied Au-NP concentrations（10 and 60 μg Au/g dry weight sediment） had no adverse effect on T.tubifex survival,while Au bioaccumulation increased with exposure concentration.In the case of GO-NPs,no mortality of T.tubifex was observed at a concentration range of 20 and180 μg GO/g dry weight sediment,whereas burrowing activity was significantly reduced at 20 and 180 μg GO/g dry weight sediment.Our results suggest that Au-NPs at 60 μg Au/g or GO-NPs at 20 and 180 μg GO/g were detected by T.tubifex as toxicants during short-term exposures.