Greenhouse Gas Emissions from the Tibetan Alpine Grassland: Effects of Nitrogen and Phosphorus Addition

Abstract

The cycle of key nutrient elements nitrogen (N) and phosphorus (P) has been massively altered by anthropogenic activities. Little is known about the impacts on greenhouse gas (GHG) emission of the large nutrient additions occurring in the alpine grasslands of the Tibetan Plateau. We investigated soil surface emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) under control, N, P and combined nitrogen and phosphorus (NP) additions from July 2011 to September 2012. Compared to the control, CO2 flux significantly increased by 14.6% and 27.4% following P and NP addition, respectively. The interaction of NP addition had a significant influence on CO2 flux during the non-growing season and the spring thaw period. Compared to the control, CH4 flux decreased by 9.9%, 23.2% and 26.7% following N, P and NP additions, respectively, and no interactive effect of NP addition was found in any period. Soil N2O flux was significantly increased 2.6 fold and 3.3 fold, following N and NP addition treatments, respectively, and there was no interaction effect of NP addition together. The contribution of cumulative CO2 emission during the non-growing season was less than 20% of the annual budget, but cumulative CH4 and N2O emissions during the same period can account for 37.3–48.9% and 44.7–59.5% of the annual budget, respectively. Methane and N2O emissions did not increase greatly during the spring thawing period, with contributions of only 0.4–3.6% and 10.3–12.3% of the annual budget, respectively. Our results suggest that N and P addition could increase CO2 and N2O emissions and reduce CH4 emission. Furthermore, although the non-growing season is very cold and long, cumulative CH4 and N2O emissions are considerable during this period and cannot be neglected by future studies evaluating the greenhouse gas emission budget in the Tibetan plateau.

Asymmetric response of aboveground and belowground temporal stability to nitrogen and phosphorus addition in a Tibetan alpine grassland

“…The data that support the findings of this study are openly available in Dryad Digital Repository (Wang et al, 2023) at https://doi.org/10.5061/dryad.d2547d87j.…”

“…Effects were considered statistically significant if p < .05 and marginally significant if .05 ≤ p < .10. Data used in the current study are deposited in the Dryad Digital Repository (Wang et al, 2023).…”

CO2, CH4 and N2O fluxes in an alpine meadow on the Tibetan Plateau as affected by N-addition and grazing exclusion

“…Our results imply that N 2 O emission would increase if N addition increases with warming under future climate change. Moreover, we found that N addition significantly increased N 2 O emission under grazing and exclosure conditions during the experiment period (Tables 1, 2), a similar result to that of Wang et al (2018) in the region (Wang et al 2018). Some studies have reported that N fertilizer application can lead to substantial N 2 O emission through nitrification-denitrification processes (Loecke and Robertson 2009).…”

Warming Amplified the Effect of Phosphorus addition on N₂O Emissions in a Peatland

“…However, the continuous intensification of human activities and the availability of P increase have resulted in P no longer being the limiting factor for ecological processes in peatlands [14][15][16][17]. Increased P input will stimulate the activity of nitrifying and denitrifying bacteria, accelerate N turnover in soil, and promote 2 of 12 soil N mineralization, which may produce more N 2 O [3,[18][19][20][21]]. Mori's meta-analysis found that the addition of P to a P limited ecosystem will meet the microbial demand for P, leading to a boom of microorganisms [22].…”

“…Currently, we still know rather little about how N 2 O emissions respond to joint environmental changes, P addition and warming, in wetlands, especially peatland ecosystems [18,21,35]. To address this, we conducted a field monitoring experiment in Hani peatland that was combined with laboratory experiments to investigate the effect of P addition, as well as its interaction with warming on peatland net N 2 O fluxes and the response of N 2 O fluxes to changes in biological and abiotic factors.…”