Analyzing the spatiotemporal evolution and driving forces of gross ecosystem product in the upper reaches of the Chaobai River Basin

The Chaobai River Basin,which is a crucial ecological barrier and primary water source area within the Beijing-Tianjin-Hebei region,possesses substantial ecological significance.The gross ecosystem product(GEP)in the Chaobai River Basin is a reflection of ecosystem conditions and quantifies nature’s contributions to humanity,which provides a basis for basin ecosystem service management and decision-making.This study investigated the spatiotemporal evolution of GEP in the upper Chaobai River Basin and explored the driving factors influencing GEP spatial differentiation.Ecosystem patterns from 2005 to 2020 were analyzed,and GEP was calculated for 2005,2010,2015,and 2020.The driving factors influencing GEP spatial differentiation were identified using the optimal parameter-based geographical detector(OPGD)model.The key findings are as follows:(1)From 2005 to 2020,the main ecosystem types were forest,grassland,and agriculture.Urban areas experienced significant changes,and conversions mainly occurred among urban,water,grassland and agricultural ecosystems.(2)Temporally,the GEP in the basin increased from 2005 to 2020,with regulation services dominating.At the county(district)scale,GEP exhibited a north-west-high and south-east-low pattern,showing spatial differences between per-unit-area GEP and county(district)GEP,while the spatial variations in per capita GEP and county(district)GEP were similar.(3)Differences in the spatial distribution of GEP were influenced by regional natural geographical and socioeconomic factors.Among these factors,gross domestic product,population density,and land-use degree density contributed significantly.Interactions among different driving forces noticeably impacted GEP spatial differentiation.These findings underscore the necessity of incorporating factors such as population density and the intensity of land-use development into ecosystem management decision-making processes in the upper reaches of the Chaobai River Basin.Future policies should be devised to regulate human activities,thereby ensuring the stability and enhancement of GEP.

Comparing the seasonal variation of parameter estimation of ecosystem carbon exchange between alpine meadow and cropland in Heihe River Basin,northwestern China

Grasslands and agro-ecosystems occupy one-third of the global terrestrial area. However, great uncertainty still exists about their contributions to the global carbon cycle. This study used various combinations of a simple ecosystem respiration model and a photosynthesis model to simulate the influence of different climate factors, specifically radiation, temperature, and moisture, on the ecosystem carbon exchange at two dissimilar study sites. Using a typical alpine meadow site in a cold region and a typical cropland site in an arid region as cases, we investigated the response char- acteristics of productivity of grasslands and croplands to different environmental factors, and analyzed the seasonal change patterns of different model parameters. Parameter estimations and uncertainty analyses were performed based on a Bayesian approach. Our results indicated that： （1） the net ecosystem exchange （NEE） of alpine meadow and seeded maize during the growing season presented obvious diurnal and seasonal variation patterns. On the whole, the alpine meadow and seeded maize ecosystems were both apparent sinks for atmospheric CO2; （2） in the daytime, the mean NEE of the two ecosystems had the largest values in July and the lowest values in October. However, overall carbon uptake in the cropland was greater than in the alpine meadow from June to September; （3） at the alpine meadow site, temperature was the main limiting factor influencing the ecosystem carbon exchange variations during the growing season, while the sensitivity to water limitation was relatively small since there is abundant of rainfall in this region; （4） at the cropland site, both temperature and moisture were the most important limiting factors for the variations of ecosystem carbon exchanges during the growing season; and （5） some parameters had an obvious characteristic of seasonal patterns, while others had only small seasonal variations.

Carbon dioxide fluxes of tundra vegetation communities on an esker top in the low-Arctic

Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic tundra future carbon budgets.

Basic Principles of Gross Ecosystem Product(GEP)Accounting

Gross ecosystem product(GEP) is the gross value of all ecosystem products and services provided by ecosystems for human society. In practice, GEP measures the ecosystems’ contributions to human well-being and constitutes one of the core issues in the construction of ecological civilization systems. Currently, GEP accounting faces a series of problems, such as the inconsistency of accounting subjects and a lack of accounting standards,the result of which is the non-reproducibility and weak applicability of accounting results. In this paper, mainstream models for ecosystem service valuation are summarized in a systematic manner. On this basis, eight basic principles are established for screening accounting indicators: biological productivity, human benefits, production territoriality, current increment, actual effectiveness, physical metrizability, data availability, and harmlessness. Next, a series of ecosystem service subjects are identified that need to be excluded from accounting, and the detailed reasons for their exclusion are presented. Finally, three ideas for improving GEP accounting are offered from the perspectives of the relationship between biological production and human production, the circulation-transport relationship and spatial differences, and harms to the ecosystem carrying capacity. The purpose is to provide positive considerations aimed at promoting the socio-economic applications of accounting and to contribute to the scientific quantification of the values of ecological products.

Effects of Environmental Conditions and Aboveground Biomass on CO2 Budget in Phragmites australis Wetland of Jiaozhou Bay,China

Estuarial saline wetlands have been recognized as a vital role in CO_2 cycling.However,insufficient attention has been paid to estimating CO_2 fluxes from estuarial saline wetlands.In this study,the static chamber-gas chromatography(GC) method was used to quantify CO_2 budget of an estuarial saline reed(Phragmites australis) wetland in Jiaozhou Bay in Qingdao City of Shandong Province,China during the reed growing season(May to October) in 2014.The CO_2 budget study involved net ecosystem CO_2 exchange(NEE),ecosystem respiration(Reco) and gross primary production(GPP).Temporal variation in CO_2 budget and the impact of air/soil temperature,illumination intensity and aboveground biomass exerted on CO_2 budget were analyzed.Results indicated that the wetland was acting as a net sink of 1129.16 g/m^2 during the entire growing season.Moreover,the values of Reco and GPP were 1744.89 g/m^2 and 2874.05 g/m^2,respectively;the ratio of Reco and GPP was 0.61.Diurnal and monthly patterns of CO_2 budget varied significantly during the study period.Reco showed exponential relationships with air temperature and soil temperature at 5 cm,10 cm,20 cm depths,and soil temperature at 5 cm depth was the most crucial influence factor among them.Meanwhile,temperature sensitivity(Q10) of Reco was negatively correlated with soil temperature.Light and temperature exerted strong controls over NEE and GPP.Aboveground biomass over the whole growing season showed non-linear relationships with CO_2 budget,while those during the early and peak growing season showed significant linear relationships with CO_2 budget.This research provides valuable reference for CO_2 exchange in estuarial saline wetland ecosystem.

Effect of water stress on ecosystem photosynthesis and respiration of a Leymus chinensis steppe in Inner Mongolia

Many studies on global climate have forecast major changes in the amounts and spatial patterns of precipitation that may significantly affect temperate grasslands in arid and semi-arid regions. As a part of ChinaFLUX, eddy covariance flux measurements were made at a semi-arid Leymus chinensis steppe in Inner Mongolia, China during 2003-2004 to quantify the response of carbon exchange to environmental changes. Results showed that gross ecosystem production (FGEP) and ecosystem respiration (Reco) of the steppe were significantly depressed by water stress due to lack of precipitation during the growing season. Temperature was the dominant factor affecting FGEP and Reco in 2003, whereas soil moisture imposed a significant influence on both Reco and FGEP in 2004. Under wet conditions, Reco showed an exponentially increasing trend with temperature (Q10 = 2.0), but an apparent reduction in the value of Reco and its temperature sensitivity were observed during the periods of water stress (Q10=1.6). Both heat and water stress can cause decrease in FGEP. The sea-sonality of ecosystem carbon exchange was strongly correlated with the variation of precipitation. With less precipitation in 2003, the steppe sequestrated carbon in June and July, and went into a senescence in early August due to water stress. As compared to 2003, the severe drought during the spring of 2004 delayed the growth of the steppe until late June, and the steppe became a CO2 sink from early July until mid-September, with ample precipitation in August. The semi-arid steppe released a total of 9.7 g C·m-2 from May 16 to the end of September 2003, whereas the net carbon budget during the same period in 2004 was close to zero. Long-term measurements over various grasslands are needed to quantify carbon balance in temperate grasslands.

Seasonal drought effects on carbon sequestration of a mid-subtropical planted forest of southeastern China

Continuous measurement of carbon dioxide exchange using the eddy covariance (EC) technique is made at the Qianyanzhou mid-subtropical planted forest as part of the ChinaFLUX network. Qianyanzhou planted forest is affected by typical subtropical continental monsoon climate. It has plentiful water and heat resource but is in inconsistency of its seasonal distribution in the mid-subtropical region, thus seasonal drought frequently occurs in this planted forest. In this study, seasonal drought effect on ecosystem carbon sequestration was analyzed based on net ecosystem productivity (NEP), ecosystem respiration (RE) and gross ecosystem productivity (GEP) at the month scale in 2003 and 2004. In this drought-stressed planted forest, ecosystem carbon sequestration showed a clear seasonality, with low rates during seasonal drought and in winter. The declining degree of ecosystem carbon sequestration under the seasonal drought condition was determined by the accumulation of soil moisture deficits and a co-occurrence of high temperatures. Different drought effects are expected for RE and GEP. The net effect of ecosystem carbon balance depends on how these two quantities are affected relatively to each other. Summer drought and heat wave are two aspects of weather that likely play an important part in the annual NEP of forest in this region.