Early Spring Snowmelt and Summer Droughts Strongly Impair the Resilience of Key Microbial Communities in Subalpine Grassland Ecosystems

Abstract

Subalpine grassland ecosystems are important from biodiversity, agriculture, and touristic perspectives but their resilience to seasonally occurring climatic extremes is increasingly challenged with climate change, accelerating their vulnerability to tipping points. Microbial communities, which are central in ecosystem functioning, are usually considered as more resistant and highly resilient to such extreme events due to their functional redundancy and strong selection in residing habitats. To investigate this, we explored the soil microbial responses upon recurrent summer droughts associated with early snowmelt in grasslands mesocosms set-up at the Lautaret Pass (French Alps). Potential respiration, nitrification and denitrification were monitored over a period of two growing seasons along with quantification of community gene abundances of total bacteria as well as (de)nitrifiers. Results revealed that droughts had a low and short-term impact on bacterial total respiration supporting their hypothesized high resistance and ability to recover. Nitrification and abundances of the corresponding functional guilds showed relatively strong resistance to summer droughts but declined in response to early snowmelt. This triggered a cascading effect on denitrification but also on the abundances of denitrifying communities which could recover from all climatic extremes except from the summer droughts where nitrifiers were collapsed. Denitrification and the respective functional groups faced high impact of applied stresses with strong reduction in the abundance and activity of this specialized community. Although, the consequently lower microbial competition for nitrate may be positive for plant biomass production, warnings exist when considering the potential nitrogen leaching from these ecosystems as well as risks of greenhouses gases emission such as N2O

Invasive Weeds Dynamics, Plant-Microbes Interactions, and Carbon-Nitrogen Cycles in Sino-Pakistan’s Grasslands Perspectives

“…This might be attributed to addition and/or decay of OM in the soil. The concentration of ammonia and nitrate forms of N was also associated with soil pH as acid soils having pH less than 6 recorded higher concentration of ammonia, whereas less acidic soils chiefly produced nitrate [14,[75][76][77][78].…”

“…The final products due to incomplete denitrification are N2 and N 2 O, which impart pronounced repercussions on the gaseous chemistry of atmosphere as 16% higher N 2 O concentrations have been deposited in the atmosphere compared to pre-industrial era. Overall, both of these processes contribute over 70% of the total N 2 O emissions from terrestrial ecosystems [14,72,[79][80][81]. At local and global levels, mountainous GL serve as a strategic terrestrial ecosystem by providing diverse ecosystem services.…”

“…Fundamentally, the concept of GL conservation entails such practices that are adopted for the protection and sustainable management of GL ecosystems in order to maintain biodiversity and ecological integrity for persistent provision of ecosystem services. In the modern era, GL conservation has become associated with the monitoring of anthropogenic interferences and grass-microbe interactions along with carbon and nitrogen (N) cycles [12][13][14][15][16]. The study of these interactions and nutrient cycles might unveil feasible solution for imparting sustainability to traditional and modern ecosystem services offered by GL.…”

Early spring snowmelt and summer droughts strongly impair the resilience of bacterial community and N cycling functions in a subalpine grassland ecosystem

“…Data are available from the Zenodo Digital Repository: http:// doi.org/10.5281/zenodo.5648316 (Hafeez et al 2023).…”

Bacterial denitrification drives elevated N 2 O emissions in arid southern California drylands

“…In drylands, where infrequent rainfall may rarely develop the anoxic soil environments required for denitrification, biogeochemical theory would predict that oxygen reduction by nitrifiers is thermodynamically favored over NO 3 − reduction by denitrifiers (4)(5)(6). However, in deserts, extreme heat and aridity may limit the survival and activity of microorganisms (10)(11)(12)(13)(14), suggesting that the rapid N 2 O emission pulses detected within minutes of wetting soils may not be exclusively biological. N 2 O can be produced via chemodenitrification, an abiotic process coupling the reaction of metals with nitrite (NO 2…”