Temporal and spatial change characteristics of growing season evapotranspiration and its cause analysis in Liaohe River delta wetland, China

2020 ◽  
Vol 40 (2) ◽  
Author(s):  
刘曼晴 LIU Manqing ◽  
胡德勇 HU Deyong ◽  
于琛 YU Chen ◽  
王莎莎 WANG Shasha
Keyword(s):  
Growing Season ◽  
River Delta ◽  
Spatial Change ◽  
Cause Analysis ◽  
Liaohe River ◽  
Change Characteristics ◽  
Temporal And Spatial

CHANGES IN THE HYDROTHERMAL COEFFICIENT AND IN THE FREQUENCY OF EXTREME HUMIDIFICATION CONDITIONS ON THE TERRITORY OF BELARUS DURING CLIMATE WARMING

2020 ◽  
pp. 5-18
Author(s):  
Yuliya A. Brovka ◽  
Ivan V. Buyakov
Keyword(s):  
Climate Warming ◽  
Growing Season ◽  
Northern Region ◽  
Meteorological Station ◽  
Spatial Change ◽  
Hydrothermal Coefficient ◽  
Arid Conditions ◽  
Moisture Supply ◽  
Moisture Conditions ◽  
Heat And Moisture

It is important to study the heat and moisture supply of the territory under climate warming conditions in Belarus since 1989, as well as changes in the occurrence frequency of extreme moisture conditions. The features of the spatial change in the averaged hydrothermal coefficient (HTC) for the period of climate warming (1989–2019) and the colder period preceding it (1960–1988) in the months of the growing season were revealed based on the maps constructed by interpolation. A decrease in the aridity of conditions in May and September in the southeast and east of the country, an increase in aridity in June and August (especially in the southern regions), an increase in the area with excessive moisture in July and its decrease in September were defined. The article shows the features of changes in the frequency of droughts (HTC ≤ 0,7), less arid conditions (HTC = 0,71–1,0) and excessive moisture (HTC > 1,6) from May to September in 1989–2019, according to compared with the period 1960–1988. It was found that during the period of climate warming from May to September, there is a significant increase in the droughts frequency at meteorological stations in various regions of Belarus. A decrease in the number of years with drought in May and June is observed at several eastern and southern meteorological stations, in August – at the Zhitkovichi meteorological station, in September – at the Kostyukovichi meteorological station. The frequency of arid conditions in May, July and September decreases at many meteorological stations, and its changes are characterized by territorial heterogeneity. An increase in the number of years with less arid conditions is observed in most of Belarus in June and August. A significant increase in the frequency of excessive moisture was noted in July in most of the territory of Belarus, in May – in some regions. A decrease in the frequency of excessive moisture is observed at many meteorological stations in June and August; the number of years with excessive moisture increases only in the northern region. Spatial heterogeneity and less pronounced changes in the frequency of excessive moisture are noted in September.

scholarly journals Partitioning CO<sub>2</sub> net ecosystem exchange fluxes on the microsite scale in the Lena River Delta, Siberia

2018 ◽  
Author(s):  
Tim Eckhardt ◽  
Christian Knoblauch ◽  
Lars Kutzbach ◽  
Gillian Simpson ◽  
Evgeny Abakumov ◽  
...  
Keyword(s):  
Water Table ◽  
Net Ecosystem Exchange ◽  
Growing Season ◽  
Arctic Tundra ◽  
High Water ◽  
Water Levels ◽  
River Delta ◽  
Lena River ◽  
Hydrological Conditions ◽  
Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing rates of amplified climate change. This is critical as these ecosystems store significant amounts of carbon in their soils, which can be mineralized to CO2 and CH4 and released to the atmosphere. To understand how the CO2 net ecosystem exchange (NEE) fluxes will react to changing climatic conditions, it is necessary to understand the individual responses of the physiological processes contributing to CO2 NEE. Therefore, this study aimed: (i) to partition NEE fluxes at the soil-plant-atmosphere interface in an arctic tundra ecosystem; and (ii) to identify the main environmental drivers of these fluxes. Hereby, the NEE fluxes were partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined flux data collected during the growing season in 2015 using closed chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. The measured fluxes on the microscale (1 m–10 m) were used to model the NEE, GPP, Reco, RH, RA and net ecosystem production (NPP) over the growing season. Here, for the first time, the differing response of in situ measured RA and RH fluxes from permafrost-affected soils to hydrological conditions have been examined. It was shown that low RA fluxes are associated to a high water table, most likely due to the submersion of mosses, while an effect of water table fluctuations on RH fluxes was not observed. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a sink for atmospheric CO2 during the growing season. Spatial heterogeneity was apparent with the net CO2 uptake at a wet, depressed polygon center being more than twice as high as that measured at a drier polygon rim. In addition to higher GPP fluxes, the differences in NEE between the two microsites were caused by lower Reco fluxes at the center compared to the rim. Here, the contrasting hydrological conditions caused the CO2 flux differences between the microsites, where high water levels lad to lower decomposition rates due to anoxic conditions.

scholarly journals Partitioning net ecosystem exchange of CO<sub>2</sub> on the pedon scale in the Lena River Delta, Siberia

2019 ◽  
Vol 16 (7) ◽  
pp. 1543-1562 ◽  
Author(s):  
Tim Eckhardt ◽  
Christian Knoblauch ◽  
Lars Kutzbach ◽  
David Holl ◽  
Gillian Simpson ◽  
...  
Keyword(s):  
Growing Season ◽  
Arctic Tundra ◽  
River Delta ◽  
Environmental Drivers ◽  
Co2 Fluxes ◽  
Lena River ◽  
Hydrological Conditions ◽  
Tundra Ecosystem ◽  
Water Saturated ◽  
Lena River Delta

Abstract. Arctic tundra ecosystems are currently facing amplified rates of climate warming. Since these ecosystems store significant amounts of soil organic carbon, which can be mineralized to carbon dioxide (CO2) and methane (CH4), rising temperatures may cause increasing greenhouse gas fluxes to the atmosphere. To understand how net the ecosystem exchange (NEE) of CO2 will respond to changing climatic and environmental conditions, it is necessary to understand the individual responses of the processes contributing to NEE. Therefore, this study aimed to partition NEE at the soil–plant–atmosphere interface in an arctic tundra ecosystem and to identify the main environmental drivers of these fluxes. NEE was partitioned into gross primary productivity (GPP) and ecosystem respiration (Reco) and further into autotrophic (RA) and heterotrophic respiration (RH). The study examined CO2 flux data collected during the growing season in 2015 using closed-chamber measurements in a polygonal tundra landscape in the Lena River Delta, northeastern Siberia. To capture the influence of soil hydrology on CO2 fluxes, measurements were conducted at a water-saturated polygon center and a well-drained polygon rim. These chamber-measured fluxes were used to model NEE, GPP, Reco, RH, RA, and net primary production (NPP) at the pedon scale (1–10 m) and to determine cumulative growing season fluxes. Here, the response of in situ measured RA and RH fluxes from permafrost-affected soils of the polygonal tundra to hydrological conditions have been examined. Although changes in the water table depth at the polygon center sites did not affect CO2 fluxes from RH, rising water tables were linked to reduced CO2 fluxes from RA. Furthermore, this work found the polygonal tundra in the Lena River Delta to be a net sink for atmospheric CO2 during the growing season. The NEE at the wet, depressed polygon center was more than twice that at the drier polygon rim. These differences between the two sites were caused by higher GPP fluxes due to a higher vascular plant density and lower Reco fluxes due to oxygen limitation under water-saturated conditions at the polygon center in comparison to the rim. Hence, soil hydrological conditions were one of the key drivers for the different CO2 fluxes across this highly heterogeneous tundra landscape.

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