Nitrogen deposition reduces methane uptake in both the growing and non-growing season in an alpine meadow

Alpine meadow and alpine steppe are the two most widely distributed nonzonal vegetation types in the Qinghai-Tibet Plateau. In the context of global climate change, the differences in spatial-temporal variation trends and their responses to climate change are discussed. It is of great significance to reveal the response of the Qinghai-Tibet Plateau to global climate change and the construction of ecological security barriers. This study takes alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau as the research objects. The normalized difference vegetation index (NDVI) data and meteorological data were used as the data sources between 2000 and 2018. By using the mean value method, threshold method, trend analysis method and correlation analysis method, the spatial and temporal variation trends in the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau were compared and analyzed, and their differences in the responses to climate change were discussed. The results showed the following: (1) The growing season length of alpine meadow was 145~289 d, while that of alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau was 161~273 d, and their growing season lengths were significantly shorter than that of alpine meadow. (2) The annual variation trends of the growing season NDVI for the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau increased obviously, but their fluctuation range and change rate were significantly different. (3) The overall vegetation improvement in the Qinghai-Tibet Plateau was primarily dominated by alpine steppe and alpine meadow, while the degradation was primarily dominated by alpine meadow. (4) The responses between the growing season NDVI and climatic factors in the alpine meadow, alpine steppe and the overall vegetation of the Qinghai-Tibet Plateau had great spatial heterogeneity in the Qinghai-Tibet Plateau. These findings provide evidence towards understanding the characteristics of the different vegetation types in the Qinghai-Tibet Plateau and their spatial differences in response to climate change.

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Environmental influences on carbon dioxide fluxes over three grassland ecosystems in China

Biogeosciences ◽

10.5194/bg-6-2879-2009 ◽

2009 ◽

Vol 6 (12) ◽

pp. 2879-2893 ◽

Cited By ~ 86

Author(s):

Y. Fu ◽

Z. Zheng ◽

G. Yu ◽

Z. Hu ◽

X. Sun ◽

...

Keyword(s):

Carbon Dioxide ◽

Soil Moisture ◽

Alpine Meadow ◽

Growing Season ◽

Co2 Fluxes ◽

Meadow Steppe ◽

Temperate Steppe ◽

Area Index ◽

Grassland Ecosystems ◽

Alpine Shrub

Abstract. This study compared carbon dioxide (CO2) fluxes over three grassland ecosystems in China, including a temperate semiarid steppe in Inner Mongolia (NMG), an alpine shrub-meadow in Qinghai (HB), and an alpine meadow-steppe in Tibet (DX). Measurements were made in 2004 and 2005 using the eddy covariance technique. Objectives were to document the seasonality of the net ecosystem exchange of CO2 (NEE) and its components, gross ecosystem photosynthesis (GEP), and ecosystem respiration (Reco), and to examine how environmental factors affect the CO2 exchange in these grassland ecosystems. The 2005 growing season (from May to September) was warmer than that of 2004 across the three sites, and precipitation in 2005 was less than that in 2004 at NMG and DX. The magnitude of CO2 fluxes (daily and annual sums) was largest at HB, which also showed the highest temperature sensitivity of Reco among the three sites. A stepwise multiple regression analysis showed that the seasonal variation of GEP, Reco, and NEE of the alpine shrub-meadow was mainly controlled by air temperature, whereas leaf area index can likely explain the seasonal variation in GEP, Reco, and NEE of the temperate steppe. The CO2 fluxes of the alpine meadow-steppe were jointly affected by soil moisture and air temperature. The alpine shrub-meadow acted as a net carbon sink over the two study years, whereas the temperate steppe and alpine meadow-steppe acted as net carbon sources. Both GEP and Reco were reduced by the summer and spring drought in 2005 at NMG and DX, respectively. The accumulated leaf area index during the growing season (LAIsum) played a key role in the interannual and intersite variation of annual GEP and Reco across the study sites and years, whereas soil moisture contributed most significantly to the variation in annual NEE. Because LAIsum was significantly correlated with soil moisture at a depth of 20 cm, we concluded that the available soil moisture other than annual precipitation was the most important factor controlling the variation in the CO2 budgets of different grassland ecosystems in China.

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Impacts of precipitation, warming and nitrogen deposition on methane uptake in a temperate desert

Biogeochemistry ◽

10.1007/s10533-019-00606-0 ◽

2019 ◽

Vol 146 (1) ◽

pp. 17-29 ◽

Cited By ~ 1

Author(s):

Ping Yue ◽

Xiaoqing Cui ◽

Wenchao Wu ◽

Yanming Gong ◽

Kaihui Li ◽

...

Keyword(s):

Nitrogen Deposition ◽

Methane Uptake ◽

Temperate Desert

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Hydro-meteorological influences on the growing season CO2 exchange of an alpine meadow in the northeastern Tibetan Plateau permafrost region: observations using eddy covariance method

Theoretical and Applied Climatology ◽

10.1007/s00704-019-02861-5 ◽

2019 ◽

Vol 138 (1-2) ◽

pp. 1063-1073

Author(s):

Qingfeng Wang ◽

Huijun Jin ◽

Jun Wen ◽

Ziqiang Yuan ◽

Xiaoying Jin ◽

...

Keyword(s):

Tibetan Plateau ◽

Eddy Covariance ◽

Alpine Meadow ◽

Growing Season ◽

Co2 Exchange ◽

Permafrost Region ◽

Eddy Covariance Method ◽

Northeastern Tibetan Plateau ◽

Meteorological Influences

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Nitrogen fertilizer regulates soil respiration by altering the organic carbon storage in root and topsoil in alpine meadow of the north-eastern Qinghai-Tibet Plateau

Scientific Reports ◽

10.1038/s41598-019-50142-y ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Wen Li ◽

Jinlan Wang ◽

Xiaolong Li ◽

Shilin Wang ◽

Wenhui Liu ◽

...

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Soil Respiration ◽

Alpine Meadow ◽

Growing Season ◽

N Storage ◽

The North ◽

C Storage ◽

North Eastern ◽

C And N

Abstract Soil respiration (Rs) plays a critical role in the global carbon (C) balance, especially in the context of globally increasing nitrogen (N) deposition. However, how N-addition influences C cycle remains unclear. Here, we applied seven levels of N application (0 (N0), 54 (N1), 90 (N2), 126 (N3), 144 (N4), 180 (N5) and 216 kg N ha−1 yr−1 (N6)) to quantify their impacts on Rs and its components (autotrophic respiration (Ra) and heterotrophic respiration (Rh)) and C and N storage in vegetation and soil in alpine meadow on the northeast margin of the Qinghai-Tibetan Plateau. We used a structural equation model (SEM) to explore the relative contributions of C and N storage, soil temperature and soil moisture and their direct and indirect pathways in regulating soil respiration. Our results revealed that the Rs, Ra and Rh, C and N storage in plant, root and soil (0–10 cm and 10–20 cm) all showed initial increases and then tended to decrease at the threshold level of 180 kg N ha−1 yr−1. The SEM results indicated that soil temperature had a greater impact on Rs than did volumetric soil moisture. Moreover, SEM also showed that C storage (in root, 0–10 and 10–20 cm soil layers) was the most important factor driving Rs. Furthermore, multiple linear regression model showed that the combined root C storage, 0–10 cm and 10–20 cm soil layer C storage explained 97.4–97.6% variations in Rs; explained 94.5–96% variations in Ra; and explained 96.3–98.1% in Rh. Therefore, the growing season soil respiration and its components can be well predicted by the organic C storage in root and topsoil in alpine meadow of the north-eastern Qinghai-Tibetan Plateau. Our study reveals the importance of topsoil and root C storage in driving growing season Rs in alpine meadow on the northeast margin of Qinghai-Tibetan Plateau.

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