Gaodi Xie

The economic benefits of rainwater-runoff reduction by urban green spaces: a case study in Beijing, China.

Urbanization involves the replacement of vegetated surfaces with impervious built surfaces, and it often results in an increase in the rate and volume of rainwater surface runoff. Urban green spaces play a positive role in rainwater-runoff reduction. However, few studies have explored the benefits of rainwater-runoff reduction by urban green spaces. Based on inventory data of urban green spaces in Beijing, the paper evaluated the economic benefits of rainwater-runoff reduction by urban green spaces, using the rainwater-runoff-coefficient method as well as the economic valuation methods. The results showed that, 2494 cubic meters of potential runoff was reduced per hectare of green area and a total volume of 154 million cubic meters rainwater was stored in these urban green spaces, which almost corresponds to the annual water needs of the urban ecological landscape in Beijing. The total economic benefit was 1.34 billion RMB in 2009 (RMB: Chinese currency, US

Forest ecosystem services and their values in Beijing

1=RMB6.83), which is equivalent to three-quarters of the maintenance cost of Beijings green spaces; the value of rainwater-runoff reduction was 21.77 thousand RMB per hectare. In addition, the benefits in different districts and counties were ranked in the same order as urban green areas, and the average benefits per hectare of green space showed different trends, which may be related to the impervious surface index in different regions. This research will contribute to an understanding of the role that Beijings green spaces play in rainwater regulation and in the creation and scientific management of urban green spaces.

The Relation between Gamma-Ray and Near-Infrared Radiation in Gamma-Ray-loud Blazars

As the most important ecosystem in Beijing, the forest supports a lot of ecosystem services to local and around communities, which plays a key role in the maintenance of urban ecological security. However, the valuation on the forest ecosystem services based on regional scale could not provide precise and reasonable values for forestry sector management. In this study, we estimated the magnitudes and economic values of the forest ecosystem services in Beijing at sublot level. The economic value of forest ecosystem services in Beijing was estimated to be 19 339.71×106 yuan (RMB) in 2004. Among all the ecosystem services indicators we estimated in this study, only fruit, timber and part of the recreation (which only include the tourism income from the forest parks and scenic areas, but not include that from other forest types) were measured in the social economic system. As estimated in this study, more than 82.19% of the economic value of forest ecosystem services could not be measured in the socio-economic statistical system. The importance of forest ecosystem services in Beijing to human welfare was underestimated by the socio-economic system. Therefore, the policies about the eco-compensation of forest ecosystem services should be established to maintain the sustainable supply of the forest ecosystem services in Beijing.

Radio-selected BL Lacertae objects and some correlations

We collect 16 gamma-ray-loud blazars (seven BL Lac objects and nine flat-spectrum radio quasars) with both observed near-infrared and gamma-ray flux densities and find that the near-IR luminosity correlates better with gamma-ray luminosity than with X-ray. Possible constraints on the gamma-ray emission mechanism are discussed. We suggest that the gamma-ray radiation is probably created by inverse Compton scattering of the radiation from hot circumnuclear dust by beamed, ultrarelativistic electrons.

Land Use Dynamics, Farmers' Preferences and Policy Implications in the Jinghe Watershed of Remote North-Western China

Based on the orientation of relativistic jets of BL Lac objects, the observed data must be corrected for the Doppler effect. For 21 radio-selected BL Lac objects whose optical Doppler factors have been obtained (Xie et al 1991a, b, 1992), their corrected data based on our assumption of Doppler factor show good relations, which means synchrotron emission is their main emission mechanism, and our assumption of Doppler factor is reasonable.

Regional differences of water conservation in Beijing’s forest ecosystem

This paper investigates the dynamics of land use patterns, contributory issues, farmers preferences and policy implications in the Jinghe watershed of remote north-western China. Landsat™ data (using GIS) and primary data from participatory rural appraisal – a method rarely applied in China – and household surveys using weighted indices were analysed. Proportions of land use and landscape indices were applied to analyse changes in land use patterns. It was found that land use patterns remain relatively stable in the watershed region where arable land and grassland predominate, a situation that has not changed structurally for 10–20 years. In villages, however, structural changes in landscape patterns occurred with transitions from predominantly arable land to forest and grass. High values for dominance and contagion indices were found in counties with relatively simple land use patterns or agricultural land use, while low values for dominance and contagion indices were associated with diversified land use involving agriculture, forest and grassland. Government intervention, market demand, personal considerations and growing environmental concerns are perceived by farmers as major factors leading to land use change. The local people prefer to grow food crops to ensure food security rather than to manage forest and grassland. This calls for a comprehensive natural resource conservation strategy, which should be based on building resource conservation into policy making; institutional reform with local participation; promotion of indigenous technology for resource conservation and management; and population control.

Seasonal dynamics of gas regulation service in forest ecosystem

The water conservation capacities of main forests in Beijing, China were estimated through the quantitative analysis. Various methods developed in published papers on forest hydrology were employed. The forests in Huairou, Yanqing, Miyun, Mentougou and Fangshan districts are the main contributors to water conservation (the cumulative ratio reaches 65%), and the forests in Tongzhou, Chaoyang, Shunyi and Daxing districts have the highest water conservation capacity (3000 m3/ha). Altitude and slope are the key factors to affect the water conservation capacity. The forests located in Plain Area, Hilly Area, Low Mountain, and Middle Mountain contributes 27%, 28%, 24% and 21% of the conserved water, respectively. The water conservation capacity of forests in Plain Area (2 948 m3/ha), is superior to the forests in other regions. And the forests situated on Flat Slope, Moderate Slope and Gentle Slope constitute the largest proportion (nearly 93%) of water conservation, while the forests on Flat Slope has the highest water conservation capacity (2 797 m3/ha), and the forest on Steep slope has the lowest water conservation capacity (948 m3/ha).

Decijansky Radio Flux BL Lacertae Objects

Using the 3-year observational data from ChinaFlux (Chinese Terrestrial Ecosystem Flux Research Network), we studied the gas regulation flux dynamics and cumulative process of gas regulation value in Qianyanzhou middle subtropical plantation (QYF) and Changbai Mountain temperate mixed forest (CBF). The gas regulation service was differentiated into vegetation gas regulation service and net ecosystem gas regulation service. Carbon tax approach, reforestation cost approach and industrial oxygen approach were employed to calculate gas regulation value. Results show that there was significant seasonal variation in vegetation gas regulation flux. Daily CO2 uptake fluxes averaged 82.00 kg·ha−1·d−1 and 59.37 kg·ha−1·d−1 and the corresponding O2 emission fluxes were 59.65 kg·ha−1·d−1 and 43.19 kg·ha−1·d−1 for QYF and CBF, respectively. The cumulative curves of vegetation gas regulation value always followed a sigmoid shape, and the annual gas regulation value produced by vegetation was RMB 14 342.69 yuan·ha−1 and RMB 10 384.18 yuan·ha−1 for both QYF and CBF, respectively. In terms of monthly net ecosystem gas regulation service, QYF appeared as a CO2 sink and O2 source for the whole year, while CBF appeared to be a CO2 sink and O2 source mainly in the period between May and September. The cumulative curves of net ecosystem gas regulation value presented a sigmoid (“S”) shape for QYF, while a unimodal type curve for CBF. The annual net ecosystem gas regulation value was 8470.52 yuan·ha−1 and 5091.98 yuan·ha−1 for QYF and CBF, respectively. The economic value of both the vegetation gas regulation service and net ecosystem gas regulation service were mainly produced between May and October.

Forest soil conservation based on eco-service provision unit method and its value in Anji County, Huzhou, Zhejiang, China

BL Lac objects with radio flux in the range of [1, 10) decijanskys (dJy) are defined as observational class dJy. Because the radio fluxes of most radio-selected BL Lac objects (RBLs) are bigger than 1 Jy while the radio fluxes of most X-ray-selected BL Lac objects (XBLs) are less than 1 dJy, we investigate whether the dJy class forms a bridge connecting RBLs and XBLs on the αro-αox color-color diagram. We compose a dJy sample by collecting dJy class sources from radio and X-ray surveys as well as other means of observation. Our study shows that the dJy sample so collected does not form a bridge connecting RBLs and XBLs. Instead, the sources of the sample are mainly distributed in the main domains of RBLs and XBLs. We find no evidence of the existence of any specific observational class in the medium of the two classes. This suggests that RBLs and XBLs may not be unified merely through observational orientation, because such a unified scheme expects some observational class to form the bridge. In order to have a more reliable study, it is proposed that 1 dJy radio surveys that include some previously missed BL Lac objects should be made.

The exact solution of Einstein's disc

We propose an eco-service provision unit method for estimating the benefit and spatial differences of forests in controlling soil erosion. A total of 197 eco-service provision units were grouped on 1424.43xa0km2 of forest according to differences in vegetation, slope, soil, and rainfall. The amount of soil conservation and its economic value were estimated. The forests in Anji County prevent 4.08xa0×xa0105 tons of soil from eroding annually, thereby avoiding 1.36xa0×xa0104 tons of nutrient loss (on-site cost) and preventing 149 tons of nutritive elements from entering water systems (off-site cost). From an economic perspective, the soil nutrient conservation in the forests of Anji County generated an annual benefit of 43.37 million RMB (Chinese Currency, 6.20 RMBxa0=xa0US