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To conserve ecosystem and its services is a frontier and hot topic in the researches of conservation ecology. This paper reviewed the newest concepts and methods in the assessment of ecosystem and its services conservation, with the focus on the indicators and criteria for assessing the conservation status and the endangerment level of ecosystem as well as the main methods of ecosystem services assessment and conservation (including benefit transfer, systematic modeling, and quantitative indicator-based estimation). With the consideration of the research progress and the demands of ecological conservation in China, some issues to be urgently solved were put forward: 1) formulating the indicators, criteria, and methods suitable for the assessment of ecosystem conservation in China, 2) developing the methodologies for the quantitative assessment of ecosystem services, 3) determining the demands and optimal spatial arrangement of ecosystem and its services conservation in China, and 4) establishing the policies and incentive mechanisms for ecosystem and its services conservation. The resolution of these issues would supply important guarantee to the development of ecological civilization in China.

Based on the 2000-2008 MODIS-NDVI images and using dimidiate pixel model, a dynamic evaluation was made on the vegetation coverage in northern Shaanxi Province, one of the ecologically fragile area in China, under the backgrounds of returning farmland to forestland and grassland and of the integrated management of soil and water loss. In 2000-2008, the vegetation coverage in the study area fluctuated within a year, being the highest in August and the lowest in March, and showed an increasing trend from the northwest to the southeast. The annual maximum vegetation coverage had a pronounced increase, but the area of medium and high coverage increased while that of low coverage decreased. The increased area of vegetation coverage occupied more than half of the study area, especially in the northeast. Climate features and human activities were the main causes inducing the pronounced increase of vegetation coverage, reflecting to a certain extent the effectiveness of ecological restoration efforts. The dimidiate pixel model based on the MODIS-NDVI images could well and truly simulate the spatiotemporal variation trend of the vegetation cover in northern Shaanxi, and be applicable to quantitatively estimate and evaluate the effectiveness of vegetation restoration at regional scale.

Based on the 10-day SPOT VEGETATION NDVI data and the daily meteorological data from 1998 to 2007 in Yan' an City, the main meteorological variables affecting the annual and interannual variations of NDVI were determined by using regression tree. It was found that the effects of test meteorological variables on the variability of NDVI differed with seasons and time lags. Temperature and precipitation were the most important meteorological variables affecting the annual variation of NDVI, and the average highest temperature was the most important meteorological variable affecting the inter-annual variation of NDVI. Regression tree was very powerful in determining the key meteorological variables affecting NDVI variation, but could not build quantitative relations between NDVI and meteorological variables, which limited its further and wider application.

Sediment gyration sampling was conducted in June 2006 to analyze the profile distribution of sediment particle sizes at a check-dam built in 1954 in a typical small watershed of hilly and gully Loess plateau. There were at least 28 layers of sediment gyration at the check-dam, with the layer depth varied from 2 cm to 60 cm. In the sediment profile, silt (0.05-0.002 mm) occupied60%, its particle size being mainly within the range of 0.01-0.05 mm, while coarse sand (0.05 mm) accounted for 23.09%. The variation degree of sediment particle sizes increased with increasing depth, and an abrupt change was observed at the depth 2 m. Both longitudinal gradient and hydrodynamic condition caused the variation of sediment particle sizes. There was an accumulated plough layer of 72 cm thickness in the profile, which had indicative role for the sediment erosion environment of check dam.

Based on the land use change data and by using 137Cs tracer technique, this paper studied the change process of soil erosion intensity in Yangjuangou watershed in Loess Hilly Region. Since the 1980's, the land use intensity in the watershed decreased gradually. In 1980-2006, the slope arable land decreased from 94.9 hm2 to 0.2 hmb2, while the forest land, shrub land, orchard land, and grassland increased from 0 to 51.1 hm2, from 0 to 19.2 hm2, from 0 to 18.0 hm2, and from 76.9 hm2 to 80.1 hmb2, respectively. The soil erosion intensity was in the order of slope arable landshrub landorchard landgrass landforest land. In 1980, 1984, 1996, and 2006, the soil erosion intensity was 6408.9, 5362.4, 4903.9, and 3641.4 t x km(-2) x a(-1), respectively, being changed from intense to moderate. Soil and water conservation and vegetation restoration were the main causes of the decrease of soil erosion intensity in the study area.