Yongping Wei

Double counting in ecosystem services valuation: causes and countermeasures

Many studies have been conducted on ecosystem services and double counting is a frequent problem that causes uncertainty and poor reliability of estimating the value of ecosystem services. By referring to previous studies of ecosystem service valuation, our research has identified the basic causes of double counting. These include ambiguous definitions and inconsistent classifications of ecosystem services, poor understanding of ecosystem complexity, inadequate recognition of exclusiveness and complementarities of individual ecosystem services, spatio-temporal scale dependence of ecosystem services, and overlap and lack of cross-referencing between ecosystem service valuation methods. Measures for reducing double counting in ecosystem service valuation are proposed as follow: (1) identifying the spatio-temporal scales of ecosystem services; (2) valuing the final benefits obtained from ecosystem services; (3) establishing consistent classification systems for ecosystem services; and (4) selecting valuation methods appropriate for the study context.

Ecosystem management based on ecosystem services and human activities: a case study in the Yanhe watershed

With activities that alter the structure and function of the habitat, humans have a direct impact on ecosystems and ecosystem services, i.e., the conditions and processes that sustain human life. In this study, 35 townships in the Yanhe watershed in the Loess Plateau of China were selected. The net primary production (NPP), carbon sequestration and oxygen production (CSOP), water conservation, and soil conservation were the ecosystem services selected and valuated. Human activity was quantified by an integrated human activity index (HAI) based on population density, farmland ratio, and the influence of road networks and residential areas. The NPP, CSOP, and water conservation showed a conspicuous spatial pattern fanning outward from the southwest, while the soil conservation showed an obscure spatial pattern distinguished primarily by the peripheral area surrounding the urbanized areas. Total ecosystem services in the Yanhe watershed demonstrated a decreasing pattern from south to north, and the HAI was in proportion to administrative and economic development. Based on the selected ecosystem services and HAI, we mapped the townships of the Yanhe watershed by cluster analysis, and provided sustainable ecosystem management suggestions, tailored to the social-ecological map.

Ecosystem services in changing land use

PurposeOngoing population growth and economic development place increasing demands on the supply of services produced in and by ecosystems. The resulting degradation compromises their ability to continue supporting the provision of these services. As ecosystem services (ESs) are closely related to land use changes, studies linking these topics are critical in the context of better land use planning and to ensure the sustainable provision of ESs.ResultsThe impacts of various land uses on ESs occur in three ways: (1) Major ESs are generated under different land use practices, (2) land use patterns have a significant impact on ESs, and (3) differing intensities of land use may have different impacts on the generation of ESs. As human needs for different ESs vary and are not always consistent, maximizing the use of one ES can lead to a sharp decline in other ESs that may exceed a threshold inducing irreversible change. Therefore, trade-offs between ESs have become challenges that the ecosystem planning and management community must address. Furthermore, other problems (such as a lack of reliable data, inconsistent evaluation methods, and a lack of validated results used in assessments of ESs) compound the difficulty of this challenge. The development of comprehensive assessment models that result from an integrated assessment and scenario analysis of ESs under different land uses can inform ecosystem management options.Future perspectives and conclusionsStudies of ESs under different types of land use change must enhance understanding of topics that link ecosystem processes with ESs. Recommended research includes enhancement of the management practices of soil and land, modeling and mapping the spatial flow of ESs, analyzing trade-offs and synergies between multiple ESs, and integrating and optimizing analyses of ESs. By understanding the ecological processes that drive ESs and how these are affected by land use change, we can establish a sustainable balance between multiple uses of different ESs.

Modeling Nitrate Leaching and Optimizing Water and Nitrogen Management under Irrigated Maize in Desert Oases in Northwestern China

Understanding water and N transport through the soil profile is important for efficient irrigation and nutrient management to minimize nitrate leaching to the groundwater, and to promote agricultural sustainable development in desert oases. In this study, a process-based water and nitrogen management model (WNMM) was used to simulate soil water movement, nitrate transport, and crop growth (maize [Zea mays L.]) under desert oasis conditions in northwestern China. The model was calibrated and validated with a field experiment. The model simulation results showed that about 35% of total water input and 58% of the total N input were leached to <1.8 m depth under traditional management practice. Excessive irrigation and N fertilizer application, high nitrate concentration in the irrigation water, together with the sandy soil texture, resulted in large nitrate leaching. Nitrate leaching was significantly reduced under the improved management practice suggested by farm extension personnel; however, the water and nitrate inputs still far exceeded the crop requirements. More than 1700 scenarios combining various types of irrigation and fertilizer practices were simulated. Quantitative analysis was conducted to obtain the best management practices (BMPs) with simultaneous consideration of crop yield, water use efficiency, fertilizer N use efficiency, and nitrate leaching. The results indicated that the BMPs under the specific desert oasis conditions are to irrigate the maize with 600 mm of water in eight times with a single fertilizer application at a rate of 75 kg N ha(-1).

Responses of photosynthetic properties and chloroplast ultrastructure of Bryum argenteum from a desert biological soil crust to elevated ultraviolet-B radiation.

Our understanding of plant responses to enhanced ultraviolet-B (UV-B) radiation has improved over recent decades. However, research on cryptogams is scarce and it remains controversial whether UV-B radiation causes changes in physiology related to photosynthesis. To investigate the effects of supplementary UV-B radiation on photosynthesis and chloroplast ultrastructure in Bryum argenteum Hedw., specimens were cultured for 10 days under four UV-B treatments (2.75, 3.08, 3.25 and 3.41 W m(-2) ), simulating depletion of 0% (control), 6%, 9% and 12% of stratospheric ozone at the latitude of Shapotou, a temperate desert area of northwest China. Analyses showed malondialdehyde content significantly increased, whereas chlorophyll (Chl) fluorescence parameters and Chl contents decreased with increased UV-B intensity. These results corresponded with changes in thylakoid protein complexes and chloroplast ultrastructure. Overall, enhanced UV-B radiation leads to significant decreases in photosynthetic function and serious destruction of the chloroplast ultrastructure of B. argenteum. The degree of negative influences increased with the intensity of UV-B radiation. These results may not only provide a potential mechanism for supplemental UV-B effects on photosynthesis of moss crust, but also establish a theoretical basis for further studies of adaptation and response mechanisms of desert ecosystems under future ozone depletion.

An overview of precipitation isotopes over the Extensive Hexi Region in NW China

Until now, most studies of the isotopic composition of precipitation in the Extensive Hexi Region have described individual sites. A systematic study considering the regional atmospheric circulation, the complex topography, and the re-evaporation process is lacking. This paper compares and summarizes previous studies in the Extensive Hexi Region, to provide a regional picture of the characteristics of isotopic composition of precipitation and moisture sources. δ18O and δD values exhibit significant seasonal variability, with higher values in summer and lower values in winter due to the seasonality of temperature and moisture sources. The temperature effect is more pronounced in the Extensive Hexi Region than in northwest China. The altitude effects are also evident with a gradient of −0.23 ‰/100 m for δ18O and −1.67 ‰/100 m for δD. But, the d-excess increases gradually with altitude, and the higher d-excess values occur at mountain sampling sites which are attributed to the difference of the secondary evaporation between mountains and plain. Finally, the moisture source in the study area was investigated, and the results show relatively complex patterns: the westerly and polar air masses dominate in winter; however, there are inconsistent results in summer. Whether or not the westerly air mass is the dominant supply of moisture in summer is yet to be determined. Additionally, in the course of reviewing and integrating, some new research questions are identified for future work.

Lake water volume calculation with time series remote-sensing images

The volume of water in lakes is commonly estimated by combining data of water level variations with accurate bathymetry and shore topographic maps. However, bathymetry and shore topography data are often difficult to acquire, due to high costs for labour and equipment. This article presents an innovative method for calculating lake water volumes by using long-term time series remote-sensing data. Multi-spectral satellite remote-sensing images were used to map a lake’s water surface area. The lake water surface boundaries for each year were combined with field-observed water levels to generate a description of the underwater terrain. The lake water volume was then calculated from the water surface area and the underwater terrain data using a constructed TIN (triangulated irregular network) volume model. Lake Baiyangdian, the largest shallow freshwater lake in the North China Plain, was chosen as the case study area. For the last 40 years the water levels of Lake Baiyangdian have reflected multiple dry and wet periods, which provide a good data series for the study of the proposed method. Archived Landsat MSS/TM/ETM+ and HJ-1A/B images from 1973 to 2011 were used as the basic data. The NDWI (normalized difference water index) and MNDWI (modified NDWI) were used to map the water surface of the lake, and the lake water volumes were calculated with the 3D Analyst tool of ArcMap 9.3. The results show that the estimated water volumes from remote-sensing images were very consistent with the volumes derived from the fitted equation of the lake storage capacity curve based on observed data.

Photosynthesis of two moss crusts from the Tengger Desert with contrasting sensitivity to supplementary UV-B radiation

Predicting the effects of increased ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion on temperate desert ecosystems requires better knowledge of the ecophysiological response of common moss species. The aim of the current work was to determine whether elevated UV-B radiation affected photosynthetic performance and chloroplast ultrastructure of two moss crusts and whether response differences were observed between the crusts. In laboratory experiments, Bryum argenteum and Didymodon vinealis, which show microdistributions and are dominant in soil crusts at the Tengger Desert, Northern China, were subjected to four levels of UV-B radiation of 2.75 (control), 3.08, 3.25, and 3.41 W m−2 for 10 days, simulating 0, 6, 9, and 12% of stratospheric ozone at the latitude of Shapotou, respectively. The results showed that chlorophyll a fluorescence parameters (i.e., the maximal quantum yield of PSII photochemistry, the effective quantum yield of PSII photochemistry, and photochemical quenching coefficient), pigment contents, soluble protein contents, and the ultrastructure were negatively influenced by elevated UV-B radiation and the degree of detrimental effects significantly increased with the intensity of UV-B radiation. Moreover, results indicated that B. argenteum was probably more sensitive to supplementary UV-B radiation than D. vinealis. Therefore, we propose the use of B. argenteum crusts as a bioindicator of responses to elevated UV-B radiation.

Evolution of China’s water issues as framed in Chinese mainstream newspaper

There is an urgent need globally to trigger fundamental societal changes in water management away from existing unsustainable paradigms. This paper attempts to understand the evolution of newspaper coverage of water issues in China by analyzing water-related articles in a major national newspaper, the People’s Daily, over the period 1946–2012 using a content analysis approach. The major findings include the following: (1) water issues were in relatively prominent positions in the newspaper; (2) the reporting of water issues in China experienced three stages: 1946 to the middle of 1980s—flood and drought control and water for food production, the middle of 1980s to 1997—water for economic development, and 1998 to the present—water for the environmental sustainability and economic development; (3) the reporting of water issues in the People’s Daily clearly reflected China’s top-down water resources management system, and no “real” public opinions on water were reported during the study period; and (4) the People’s Daily is just a wind vane of Chinese mainstream values and policies on water. The findings supported the realist assumption that the societal value changes on water issues in China were triggered by a range of factors including biophysical pressure (floods and droughts), political campaign (the Cultural Revolution), macro-economic reform (Reform and Opening-up), water institutional arrangement (the Water Law), and water management reform (the No. 1 Central Document on water reform). While there are similarities and differences between this study and other studies, important implications for more sustainable water management are a need to strengthen academic specialists’ and NGO’s voices in the newspaper to create a better informed public, and to stimulate practices toward sustainable water use.

Carbon sequestration capacity of shifting sand dune after establishing new vegetation in the Tengger Desert, northern China.

Reconstructing vegetation in arid and semiarid areas has become an increasingly important management strategy to realize habitat recovery, mitigate desertification and global climate change. To assess the carbon sequestration potential in areas where sand-binding vegetation has been established on shifting sand dunes by planting xeric shrubs located near the southeastern edge of the Tengger Desert in northern China, we conducted a field investigation of restored dune regions that were established at different times (20, 30, 47, and 55 years ago) in the same area. We quantified the total organic carbon (TOC) in each ecosystem by summing the individual carbon contributions from the soil (soil organic carbon; SOC), shrubs, and grasses in each system. We found that the TOC, as well as the amount of organic carbon in the soil, shrubs, and grasses, significantly increased over time in the restored areas. The average annual rate of carbon sequestration was highest in the first 20 years after restoration (3.26 × 10(-2)kg·m(-2) ·year(-1)), and reached a stable rate (2.14 × 10(-2) kg·m(-2) ·year(-1)) after 47 years. Organic carbon storage in soil represented the largest carbon pool for both restored systems and a system containing native vegetation, accounting for 67.6%-85.0% of the TOC. Carbon in grass root biomass, aboveground grass biomass, litter, aboveground shrub biomass, and shrub root biomass account for 10.0%-21.0%, 0.2%-0.6%, 0.1%-0.2%, 1.7%-12.1% and 0.9%-6.2% of the TOC, respectively. Furthermore, we found that the 55-year-old restored system has the capacity to accumulate more TOC (1.02 kg·m(-2) more) to reach the TOC level found in the natural vegetation system. These results suggest that restoring desert ecosystems may be a cost-effective and environmentally friendly way to sequester CO2 from the atmosphere and mitigate the effects of global climate change.