Extrapolation and Uncertainty Evaluation of Carbon Dioxide and Methane Emissions in the Qinghai-Tibetan Plateau Wetlands Since the 1960s

Abstract

Wetlands are important modulators of atmospheric greenhouse gas (GHGs) concentrations. However, little is known about the magnitudes and spatiotemporal patterns of GHGs fluxes in wetlands on the Qinghai-Tibetan Plateau (QTP), the world's largest and highest plateau. In this study, we measured soil temperature and the fluxes of carbon dioxide (CO 2) and methane (CH 4) in an alpine wetland on the QTP from April 2017 to April 2019 by the static chamber method, and from January 2017 to December 2017 by the eddy covariance (EC) method. The CO 2 and CH 4 emission measurements from both methods showed different relationships to soil temperature at different timescales (annual and seasonal). Based on such relationship patterns and soil temperature data (1960-2017), we extrapolated the CO 2 and CH 4 emissions of study site for the past 57 years: the mean CO 2 emission rate was 1096.59 mg C m −2 h −1 on different measurement methods and timescales, with the range of the mean emission rate from 421.17 to 1754.99 mg C m −2 h −1 , while the mean CH 4 emission rate was 32.99 mg C m −2 h −1 , with the ranges of the mean emission rate from 16.95 to 46.25 mg C m −2 h −1. The estimated regional CO 2 and CH 4 emissions from permanent wetlands on the QTP were 94.29 and 2.37 Tg C year −1 , respectively. These results indicate that uncertainties caused by measuring method and timescale should be fully considered when extrapolating wetland GHGs fluxes from local sites to the regional level. Moreover, the results of global warming potential showed that CO 2 dominates the GHG balance of wetlands on the QTP.

Methane Emissions From the Qinghai‐Tibet Plateau Ponds and Lakes: Roles of Ice Thaw and Vegetation Zone

“…Compared to CH 4 emissions and average fluxes from rivers (0.37–1.23 Tg CH 4 yr −1 , 18.08 mmol m −2 d −1 ) and wetlands (0.96–3.16 Tg CH 4 yr −1 , 5.49 mmol m −2 d −1 ) on the QTP (Chen et al., 2022; Zhang et al., 2020b, 2020c), the total emissions and average flux from ponds and lakes are smaller (Figure 8a). This is because wetlands and rivers are mainly distributed in the eastern QTP with high temperatures and soil organic carbon density, thereby exhibiting high CH 4 production rates (Zhang et al., 2020b, 2020c). However, most of the ponds and lakes are distributed in the western and middle parts of the QTP, with elevations above 4,000 m, and are characterized by large, saline, and oligotrophic conditions (Liu et al., 2021; Zhang, Yao, et al., 2020).…”

“…The CH 4 emissions offset approximately 7% of CH 4 uptake by non‐wetland alpine grassland ecosystems (Wei & Wang, 2017) or about 3% of net ecosystem exchange of alpine grasslands on the QTP regarding CO 2 ‐equivalent global warming potential over 100 years (Wang, Xiao, et al., 2023). Compared to CH 4 emissions and average fluxes from rivers (0.37–1.23 Tg CH 4 yr −1 , 18.08 mmol m −2 d −1 ) and wetlands (0.96–3.16 Tg CH 4 yr −1 , 5.49 mmol m −2 d −1 ) on the QTP (Chen et al., 2022; Zhang et al., 2020b, 2020c), the total emissions and average flux from ponds and lakes are smaller (Figure 8a). This is because wetlands and rivers are mainly distributed in the eastern QTP with high temperatures and soil organic carbon density, thereby exhibiting high CH 4 production rates (Zhang et al., 2020b, 2020c).…”

“… Comparing CH 4 fluxes from waterbodies in the Qinghai‐Tibet Plateau (QTP) permafrost region with fluxes from wetlands and rivers on the QTP, and lakes in other regions of China (a), as well as high‐latitude (north of ∼50°N) waterbodies during ice‐free (b) and ice thaw (c). (a) Value is regional mean flux; the ranges represent different statistical methods for rivers or wetlands (Zhang et al., 2020b, 2020c), and 5th to 95th for CH 4 fluxes from ponds and lakes across different vegetation zones in the QTP permafrost region and lakes in other regions of China; “Average” represents areal average CH 4 flux from ponds and lakes in the QTP permafrost region; EPL represents East Plain lakes zone, IMXL represents Inner Mongolia‐Xinjiang lakes zone, NPML represents Northeast Plain and Mountain lakes zone, and YGL represents Yunnan‐Guizhou Plateau lakes zone (Li et al., 2018). (b) Value is the median CH 4 flux during ice‐free, and the range is first quartile to third quartile; CH 4 fluxes from high‐latitude waterbodies during ice‐free season collected from Kuhn et al.…”

An optimized water table depth detected for mitigating global warming potential of greenhouse gas emissions in wetland of Qinghai-Tibetan Plateau

“…The dominant plants at the site are Carex muliensis, Scirpus triqueter, Carex meyeriana, Trollius farreri, Gentiana leucomelaena, and Caltha palustris , with no moss species being present. 10 , 66 , 67 , 68 …”

“…where F is gas flux; H, the chamber height (cm) above the soil surface; M, the molar mass of the gas; P, atmospheric pressure at the sampling site; V 0 , P 0 and T 0 , molar volume (22.4 L mol −1 ), atmospheric pressure (101.325 kPa) and absolute temperature (273.15 K) under standard conditions; T, absolute temperature at the time of sampling; and dc/dt, the rate of change in the gas concentration. 22 , 68 For each chamber measurement, gas sample concentrations were plotted as a function of sampling time. Linear regressions were performed on each flux rate to verify its linearity.…”