@article {124441, title = {Nitrogen addition and warming modulate the pathogen impact on plant biomass by shifting intraspecific functional traits and reducing species richness}, journal = {JOURNAL OF ECOLOGY }, volume = {111}, year = {2023}, month = {11/2022}, pages = {509-524}, abstract = {

Foliar fungal pathogens can substantially reduce plant biomass. This effect can be modulated by environment conditions, such as soil nitrogen availability and air temperature. The ongoing global changes are altering these variables and thus interact with pathogens to influence plant biomass, but experimental test of their interactions is scarce. We conducted a 4-year field experiment in a Tibetan alpine meadow to examine the interactive effects of nitrogen addition, warming and foliar pathogens (via fungicide application) on plant biomass. We also measured plant functional traits, species richness and abundance to test the possible mechanisms underlying these interactions. Our results showed that foliar fungal pathogens reduced plant community biomass under nitrogen addition, which in turn weakened the positive nitrogen effect on community biomass. Mechanistically, nitrogen addition shifted the plant communities towards fast-growing traits; this happened predominantly because of changes in within-species trait values, including an increase in specific leaf area and height. These trait changes resulted in greater suppression of plant biomass by pathogens, likely because of the trade-offs associated with the allocation of resources to plant growth and defense. Moreover, the reduction in species richness amplified the pathogen effect under nitrogen addition due to the increased density and susceptibility of the most dominant species (i.e. Kobresia capillifolia). Furthermore, warming did not interact with pathogens and nitrogen addition to influence plant community biomass, but their three-way interaction modified the biomass of K. capillifolia. Specifically, warming enhanced the positive effect of nitrogen addition on the biomass of K. capillifolia in the fungicide, low infection plots, while it weakened the nitrogen effect in the no fungicide, high infection plots. Synthesis. Our results demonstrate how pathogens interact with nitrogen addition and warming to influence the biomass of dominant species and the whole plant community. Our study highlights the importance of considering foliar fungal pathogens when assessing ecosystem responses to multiple global change factors.

}, doi = {10.1111/1365-2745.14043}, author = {Yan, Xuebin and Kohli, Mayank and Wen, Yue and Wang, Xiaoyi} } @article {85847, title = {Grazing and climate change have site-dependent interactive effects on vegetation in Asian montane rangelands}, journal = {JOURNAL OF APPLIED ECOLOGY}, year = {2020}, month = {11/2020}, abstract = {

Climate over Asian montane rangelands is changing faster than the global average, posing serious threats to the future of the region{\textquoteright}s livestock-based economies and cultures. Effects of climate change on rangeland vegetation likely depend on grazing by herbivores but the potential responses of vegetation to such changes in climate and grazing regimes remain unclear.

We examined vegetation responses to experimentally simulated climate change (warming, drought and increased rainfall) and grazing (clipping vegetation) between 2015 and 2018 at two mountain rangeland sites: Spiti valley, in the Indian Trans-Himalaya and Tost, in the Gobi-Altai Mountains in Mongolia.

Clipping and climate change manipulations interactively reduced vegetation cover and biomass but did not affect species richness. Treatment effects and their interactions varied between sites. In ungrazed plots, vegetation cover and biomass declined sharply in response to warming (18\%-35\%) and drought (20\%-50\%) at the two sites, and, surprisingly also declined slightly in response to increased rainfall (20\%) at Tost. While the effects of climate treatments were largely similar in the grazed and ungrazed plots in Tost, they were larger in the ungrazed plots in Spiti. The decline in vegetation cover was driven by a decline in the cover of both forbs and grasses.

In combination, grazing and warming (Tost) or drought (Spiti) had sub-additive effects, that is, the decrease in vegetation cover in response to grazing and warming/drought was less than the sum of their independent effects but greater than the effect of either manipulation alone. Of the two, warming had a greater effect than drought at the more arid site (Tost), whereas drought had a larger effect at the more mesic site (Spiti).

Synthesis and applications. Our findings show that future changes in climate, including just over 1 degrees C of warming, could undermine the sustainability of pastoral economies and the persistence of wildlife across Asian montane rangelands. Furthermore, grazing by herbivores will play an important role in mediating rangeland responses to climate change; thus, pasture management in concert with local pastoralists will be crucial in mitigating the adverse effects of climate change on rangelands, pastoral livelihoods and wildlife populations.

}, doi = {10.1111/1365-2664.13781}, author = {Kohli, Mayank and Mijiddorj, Tserennadmid Nadia and Suryawanshi, Kulbhushansingh Ramesh and Mishra, Charudutt and Boldgiv, Bazartseren and Sankaran, Mahesh} }