scholarly journals Environmental Controls on Multi-Scale Dynamics of Net Carbon Dioxide Exchange From an Alpine Peatland on the Eastern Qinghai-Tibet Plateau

2022 ◽  
Vol 12 ◽  
Author(s):  
Hu Yao ◽  
Haijun Peng ◽  
Bing Hong ◽  
Qian Guo ◽  
Hanwei Ding ◽  
...  
Keyword(s):  
Eddy Covariance ◽  
Growing Season ◽  
Temporal Variations ◽  
Tibet Plateau ◽  
Precipitation Event ◽  
Carbon Dioxide Exchange ◽  
Multi Scale ◽  
Environmental Controls ◽  
Qinghai Tibet Plateau ◽  
Alpine Peatland

Peatlands are characterized by their large carbon storage capacity and play an essential role in the global carbon cycle. However, the future of the carbon stored in peatland ecosystems under a changing climate remains unclear. In this study, based on the eddy covariance technique, we investigated the net ecosystem CO2 exchange (NEE) and its controlling factors of the Hongyuan peatland, which is a part of the Ruoergai peatland on the eastern Qinghai-Tibet Plateau (QTP). Our results show that the Hongyuan alpine peatland was a CO2 sink with an annual NEE of −226.61 and −185.35 g C m–2 in 2014 and 2015, respectively. While, the non-growing season NEE was 53.35 and 75.08 g C m–2 in 2014 and 2015, suggesting that non-growing seasons carbon emissions should not be neglected. Clear diurnal variation in NEE was observed during the observation period, with the maximum CO2 uptake appearing at 12:30 (Beijing time, UTC+8). The Q10 value of the non-growing season in 2014 and 2015 was significantly higher than that in the growing season, which suggested that the CO2 flux in the non-growing season was more sensitive to warming than that in the growing season. We investigated the multi-scale temporal variations in NEE during the growing season using wavelet analysis. On daily timescales, photosynthetically active radiation was the primary driver of NEE. Seasonal variation in NEE was mainly driven by soil temperature. The amount of precipitation was more responsible for annual variation of NEE. The increasing number of precipitation event was associated with increasing annual carbon uptake. This study highlights the need for continuous eddy covariance measurements and time series analysis approaches to deepen our understanding of the temporal variability in NEE and multi-scale correlation between NEE and environmental factors.

scholarly journals Spatial and Temporal Differences in Alpine Meadow, Alpine Steppe and All Vegetation of the Qinghai-Tibetan Plateau and Their Responses to Climate Change

2021 ◽  
Vol 13 (4) ◽  
pp. 669
Author(s):  
Hanchen Duan ◽  
Xian Xue ◽  
Tao Wang ◽  
Wenping Kang ◽  
Jie Liao ◽  
...  
Keyword(s):  
Climate Change ◽  
Alpine Meadow ◽  
Global Climate ◽  
Growing Season ◽  
Tibet Plateau ◽  
Vegetation Types ◽  
Analysis Method ◽  
Alpine Steppe ◽  
Qinghai Tibet Plateau ◽  
Variation Trends

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.

scholarly journals Effects of Air Temperature and Precipitation on Soil Moisture on the Qinghai-Tibet Plateau during the 2015 Growing Season

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Qingyan Xie ◽  
Jianping Li ◽  
Yufei Zhao
Keyword(s):  
Soil Moisture ◽  
Air Temperature ◽  
Hydrological Cycle ◽  
Critical Role ◽  
Growing Season ◽  
Tibet Plateau ◽  
Ecosystem Stability ◽  
Near Surface ◽  
Temperature And Precipitation ◽  
Qinghai Tibet Plateau

The Qinghai-Tibet Plateau (QTP) holds massive freshwater resources and is one of the most active regions in the world with respect to the hydrological cycle. Soil moisture (SM) plays a critical role in hydrological processes and is important for plant growth and ecosystem stability. To investigate the relationship between climatic factors (air temperature and precipitation) and SM during the growing season in various climate zones on the QTP, data from three observational stations were analyzed. The results showed that the daily average (Tave) and minimum air temperatures (Tmin) significantly influenced SM levels at all depths analyzed (i.e., 10, 20, 30, 40, and 50 cm deep) at the three stations, and Tmin had a stronger effect on SM than did Tave. However, the daily maximum air temperature (Tmax) generally had little effect on SM, although it had showed some effects on SM in the middle and deeper layers at the Jiali station. Precipitation was an important factor that significantly influenced the SM at all depths at the three stations, but the influence on SM in the middle and deep layers lagged the direct effect on near-surface SM by 5–7 days. These results suggest that environment characterized by lower temperatures and higher precipitation may promote SM conservation during the growing season and in turn support ecosystem stability on the QTP.

Precipitation and seasonality affect grazing impacts on herbage nutritive values in alpine meadows on the Qinghai-Tibet Plateau

2019 ◽  
Vol 12 (6) ◽  
pp. 993-1008 ◽  
Author(s):  
Xixi Yao ◽  
Jianping Wu ◽  
Xuyin Gong
Keyword(s):  
Nutritional Value ◽  
Dominant Species ◽  
Nutritive Value ◽  
Growing Season ◽  
Tibet Plateau ◽  
Nutritional Values ◽  
Potentilla Fruticosa ◽  
Nutritive Values ◽  
Qinghai Tibet Plateau

AbstractAimsGrasslands used for animal husbandry are chosen depending on the nutritive values of dominant herbage species. However, the influence of grazing in combination with precipitation and growing season on the nutritive values of dominant species has not been explicated.MethodsTo unveil the influence of the different grazing intensities on the nutritional values, an ecological study was formulated, namely fencing (G0), light grazing (G1), moderate grazing (G2) and high grazing (G3). This ambitious study was undertaken on the nutritive values of the four dominant species of herbage in an alpine meadow on the Qinghai-Tibet Plateau (QTP) during growing season (June–September) for two successive years, namely 2015 (rainy year) and 2016 (droughty year).Important FindingsWe found that (i) the nutritive value of Kobresia capillifolia, Polygonum viviparum and Caragana sinica was noticeably increased by grazing, but negligible effect on Potentilla fruticosa nutritive value was recorded. (ii) During the rainy year (2015), compared with G0, Polygonum viviparum and Potentilla fruticosa displayed 5.4 and 1.5% increases in the crude protein (CP) content and 8.5 and 2.4% increases in vitro true digestibility (IVTD), respectively, while the neutral detergent fibre (NDF) decreased by 13.5 and 0.9%, respectively. During the droughty year (2016), compared with G0, C. sinica and Potentilla fruticosa showed increases in the CP content by 4.3 and 1.3% and increases in the IVTD by 10.7 and 0.4%, respectively, during G3, while the NDF decreased by 6.0 and 1.0%, respectively. (iii) The nutritive values of all species were higher in the years when the rains were good. However, the nutritive values suffered heavily during drought conditions. Besides, the highest and lowest values of nutrition were detected in June and in September, respectively. The inter-seasonal and the inter-annual changes in the nutritional values of species were higher for K. capillifolia and Polygonum viviparum than for Potentilla fruticosa and C. sinica, suggesting that Potentilla fruticosa and C. sinica had higher water-use efficiency. (iv) Grazing clearly reduced the drought tolerance of three species and showed no effects on Potentilla fruticosa. (v) Grazing clearly increased the inter-month variation in the nutritional value of K. capillifolia and Polygonum viviparum but showed no effects on Potentilla fruticosa or C. sinica. Evidently, the grazing effects impacting the nutritional value of the dominant species of herbage exhibited conspicuous inter-annual and seasonal variations with species-specific influences and responses. Our findings are expected to have far-reaching implications enabling the authorities to arrive at strategic decisions and designing of relevant policies for the efficient management of the ecosystems ensuring the speed restoration of the QTP under severe grazing and extreme climatic circumstances.

scholarly journals Impacts of climate and reclamation on temporal variations in CH<sub>4</sub> emissions from different wetlands in China: from 1950 to 2010

2015 ◽  
Vol 12 (23) ◽  
pp. 6853-6868 ◽  
Author(s):  
T. Li ◽  
W. Zhang ◽  
Q. Zhang ◽  
Y. Lu ◽  
G. Wang ◽  
...  
Keyword(s):  
Climate Warming ◽  
Coastal Wetlands ◽  
Temporal Variations ◽  
Tibet Plateau ◽  
Atmospheric Methane ◽  
Temporal And Spatial Variations ◽  
Ch4 Emissions ◽  
Natural Wetlands ◽  
Temporal And Spatial ◽  
Qinghai Tibet Plateau

Abstract. Natural wetlands are among the most important sources of atmospheric methane and thus important for better understanding the long-term temporal variations in the atmospheric methane concentration. During the last 60 years, wetlands have experienced extensive conversion and impacts from climate warming which might result in complicated temporal and spatial variations in the changes of the wetland methane emissions. In this paper, we present a modeling framework, integrating CH4MODwetland, TOPMODEL, and TEM models, to analyze the temporal and spatial variations in CH4 emissions from natural wetlands (including inland marshes/swamps, coastal wetlands, lakes, and rivers) in China. Our analysis revealed a total increase of 25.5 %, averaging 0.52 g m−2 per decade, in the national CH4 fluxes from 1950 to 2010, which was mainly induced by climate warming. Larger CH4 flux increases occurred in northeastern, northern, and northwestern China, where there have been higher temperature rises. However, decreases in precipitation due to climate warming offset the increment of CH4 fluxes in these regions. The CH4 fluxes from the wetland on the Qinghai–Tibet Plateau exhibited the lowest CH4 increase (0.17 g m−2 per decade). Although climate warming has accelerated CH4 fluxes, the total amount of national CH4 emissions decreased by approximately 2.35 Tg (1.91–2.81 Tg), i.e., from 4.50 Tg in the early 1950s to 2.15 Tg in the late 2000s, due to the wetland loss totalling 17.0 million ha. Of this reduction, 0.26 Tg (0.24–0.28 Tg) was derived from lakes and rivers, 0.16 Tg (0.13–0.20 Tg) from coastal wetlands, and 1.92 Tg (1.54–2.33 Tg) from inland wetlands. Spatially, northeastern China contributed the most to the total reduction, with a loss of 1.68 Tg. The wetland CH4 emissions reduced by more than half in most regions in China except for the Qinghai–Tibet Plateau, where the CH4 decrease was only 23.3 %.

scholarly journals Vegetation influence and environmental controls on greenhouse gas fluxes from a drained thermokarst lake in the western Canadian Arctic

2020 ◽  
Vol 17 (17) ◽  
pp. 4421-4441
Author(s):  
June Skeeter ◽  
Andreas Christen ◽  
Andrée-Anne Laforce ◽  
Elyn Humphreys ◽  
Greg Henry
Keyword(s):  
Water Content ◽  
Eddy Covariance ◽  
Vapour Pressure Deficit ◽  
Growing Season ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Lake Basin ◽  
Thermokarst Lake ◽  
Environmental Controls ◽  
Lake Formation

Abstract. Thermokarst features are widespread in ice-rich regions of the circumpolar Arctic. The rate of thermokarst lake formation and drainage is anticipated to accelerate as the climate warms. However, it is uncertain how these dynamic features impact the terrestrial Arctic carbon cycle. Methane (CH4) and carbon dioxide (CO2) fluxes were measured during peak growing season using eddy covariance and chambers at Illisarvik, a 0.16 km2 thermokarst lake basin that was experimentally drained in 1978 on Richards Island, Northwest Territories, Canada. Vegetation in the basin differs markedly from the surrounding dwarf-shrub tundra and included patches of tall shrubs, grasses, and sedges with some bare ground and a small pond in the centre. During the peak growing season, temperature and wind conditions were highly variable, and soil water content decreased steadily. Basin-scaled net ecosystem CO2 exchange (NEE) measured by eddy covariance was −1.5 [CI95 %±0.2] g C−CO2 m-2d-1; NEE followed a marked diurnal pattern with no day-to-day trend during the study period. Variations in half-hourly NEE were primarily controlled by photosynthetic photon flux density and influenced by vapour pressure deficit, volumetric water content, and the presence of shrubs within the flux tower footprint, which varied with wind direction. Net methane exchange (NME) was low (8.7 [CI95 %±0.4] mgCH4m-2d-1) and had little impact on the growing season carbon balance of the basin. NME displayed high spatial variability, and sedge areas in the basin were the strongest source of CH4 while upland areas outside the basin were a net sink. Soil moisture and temperature were the main environmental factors influencing NME. Presently, Illisarvik is a carbon sink during the peak growing season. However, these results suggest that rates of growing season CO2 and CH4 exchange rates may change as the basin's vegetation community continues to evolve.

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