Experimental warming increases ecosystem respiration by increasing above-ground respiration in alpine meadows of Western Himalaya

Pankaj Tiwari,Gopal Singh Rawat,Ishwari Datt Rai,Gautam Talukdar,Pamela Bhattacharya

doi:10.1038/s41598-021-82065-y

Pankaj Tiwari, Gopal Singh Rawat + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-82065-y

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Abstract

Alpine ecosystems in the Himalaya, despite low primary productivity, store considerable amount of organic carbon. However, these ecosystems are highly vulnerable to climate warming which may stimulate ecosystem carbon efflux leading to carbon-loss and positive feedback. We used open-top chambers to understand warming responses of ecosystem respiration (ER) and soil respiration (SR) in two types of alpine meadows viz., herbaceous meadow (HM) and sedge meadow (SM), in the Western Himalaya. Experimental warming increased ER by 33% and 28% at HM and SM, respectively. No significant effect on SR was observed under warming, suggesting that the increase in ER was primarily due to an increase in above-ground respiration. This was supported by the warming-induced increase in above-ground biomass and decrease in SR/ER ratio. Soil temperature was the dominant controlling factor of respiration rates and temperature sensitivity of both ER and SR increased under warming, indicating an increase in contribution from plant respiration. The findings of the study suggest that climate warming by 1.5–2 °C would promote ER via increase in above-ground respiration during the growing season. Moreover, net C uptake in the alpine meadows may increase due to enhanced plant growth and relatively resistant SR under warming.

Highlights

Alpine ecosystems in the Himalaya, despite low primary productivity, store considerable amount of organic carbon
herbaceous meadow (HM) being densely vegetated, as compared to sedge meadow (SM), allowed lower solar radiations reaching ground inside open-top chamber (OTC) and showed low and inconsistent soil warming across growing season, significant (p < 0.001) only during May, June and October with a mean increase of 1.0 ± 0.36 °C (p = 0.03)
S1 and S2 online) probably due to decreased solar radiations reaching ground with increased plant growth. This effect was more profound at HM, having dense vegetation, leading to a significant decrease in soil temperature (ST) (1.10 ± 0.39 °C, p = 0.006) under OTCs during August

Summary

Introduction

Alpine ecosystems in the Himalaya, despite low primary productivity, store considerable amount of organic carbon. Studies on impacts of warming on ER and SR have come up with contrasting results showing positive25,26, negative[27,28] and even neutral responses[12] These variations have originated mainly due to inherent differences in ecosystem properties and heterogeneity in soil b iota[29,30,31]. A large proportion of the alpine region in Himalaya are covered by meadows that are broadly classified as alpine moist herbaceous meadows, and alpine dry meadows dominated by graminoids i.e., grasses and sedges[36,37] These habitats are of much ecological interest owing to predominance of specialized plantforms adapted under harsh climatic conditions, their ability to translocate much of the synthesized carbon to Scientific Reports | (2021) 11:2640. We hypothesized that (1) warming would stimulate both ER and SR, (2) warming-induced decrease in soil moisture would limit increase in ER and SR, and (3) temperature sensitivity of both ER and SR would decrease under warming in both types of alpine meadows

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