A 10,000 year record of dune activity；dust storms；and severe drought in the central Great Plains

IEECAS SKLLQG

Validating MODIS-derived land surface evapotranspiration with in situ measurements at two AmeriFlux sites in a semiarid region

Reducing uncertainties in the estimation of land surface evapotranspiration (ET) from remote-sensing data is essential to better understand earth-atmosphere interactions. This paper demonstrates the applicability of temperature-vegetation index triangle (T-s-VI) method in estimating regional ET and evaporative fraction (EF, defined as the ratio of latent heat flux to surface available energy) from MODIS/Terra and MODIS/Aqua products in a semiarid region. We have compared the satellite-based estimates of ET and EF with eddy covariance measurements made over 4 years at two semiarid grassland sites: Audubon Ranch (AR) and Kendall Grassland (KG). The lack of closure in the eddy covariance measured surface energy components is shown to be more serious at MODIS/Aqua overpass time than that at MODIS/Terra overpass time for both AR and KG sites. The T-s-VI-derived EF could reproduce in situ EF reasonably well with BIAS and root-mean-square difference (RMSD) of less than 0.07 and 0.13, respectively. Surface net radiation has been shown to be systematically overestimated by as large as about 60 W/m(2). Satisfactory validation results of the T-s-VI-derived sensible and latent heat fluxes have been obtained with RMSD within 54 W/m(2). The simplicity and yet easy use of the T-s-VI triangle method show a great potential in estimating regional ET with highly acceptable accuracy that is of critical significance in better understanding water and energy budgets on the Earth. Nevertheless, more validation work should be carried out over various climatic regions and under other different land use/land cover conditions in the future.

Study on spatial pattern of land-use change in China during 1995-2000

It is more and more acknowledged that land-use/cover dynamic change has become a key subject urgently to be dealt with in the study of global environmental change. Supported by the Landsat TM digital images, spatial patterns and temporal variation of land-use change during 1995 -2000 are studied in the paper. According to the land-use dynamic degree model, supported by the 1km GRID data of land-use change and the comprehensive characters of physical, economic and social features, a dynamic regionalization of land-use change is designed to disclose the spatial pattern of land-use change processes. Generally speaking, in the traditional agricultural zones, e.g., Huang-Huai-Hai Plains, Yangtze River Delta and Sichuan Basin, the built-up and residential areas occupy a great proportion of arable land, and in the interlock area of farming and pasturing of northern China and the oases agricultural zones, the reclamation I of arable land is conspicuously driven by changes of production conditions, economic benefits and climatic conditions. The implementation of "returning arable land into woodland or grassland" policies has won initial success in some areas, but it is too early to say that the trend of deforestation has been effectively reversed across China. In this paper, the division of dynamic regionalization of land-use change is designed, for the sake of revealing the temporal and spatial features of land-use change and laying the foundation for the study of regional scale land-use changes. Moreover, an integrated study, including studies of spatial pattern and temporal process of land-use change, is carried out in this paper, which is an interesting try on the comparative studies of spatial pattern on change process and the change process of spatial pattern of land-use change.

Reproductive biology of great cormorant (Phalacrocorax carbo sinensis) in the qinghai-tibet plateau

There have been no detailed studies on reproductive biology of the Great Cormorant (Phalacrocorax carbo sinensis) in Qinghai-Tibet Plateau. We conducted such investigations during the breeding seasons of 1999 and 2000 in Qinghai-Lake Bird Isle, China. Great Cormorants began to migrate to Qinghai-Lake for reproduction from the middle of March and left from early October at the end of reproduction. Nesting periods were from early April to mid June and took 50 days. Egg-laying occurred during the three weeks from the end of April to 20 May. Females typically laid an egg every 1-2 days until clutch completion. Mean clutch size in the study area over two years was 3.3 (SE +/- 0.13, N = 68, range 1-5) and most (66.18%) fell within the range 3-4 eggs. Length of eggs averaged 61.01 mm and breadth averaged 34.13 mm. Fresh egg weight averaged 57.34 g (SE +/- 0.36, range 46.0-73.7 g, N = 179). Hatching success was 48.7% and fledging success was 64.9% over two years. Decline of available fish resources in Qinghai-Lake might be one of main causes of lower reproductive success. The causes of chick loss were possibly high altitude, high winds and prolonged rain.