An Indicator System for Assessing Soil Erosion in the Loess Plateau Gully Regions:A Case Study in the Wangdonggou Watershed,China

The Wangdonggou Watershed on the Loess Plateau in China was selected as the study area to develop a model for soil erosion assessments. Using the data collected at 20 sampling sites all tentatively selected indicators were assessed against their corresponding erosion intensity through a correlation analysis. Eight highly correlated indicators were then chosen for the soil erosion assessment. In addition, threshold limits to delineate the class size for these indicators and weights to rank them were determined. Next, a grading model incorporating the selected indicators class rating and their associated weights was developed and verified by an on site evaluation of the soil erosion intensity in the study area. Results of the verification showed that the overall accuracy of the indicator system for assessing soil erosion in the Loess Plateau gully regions could reach 85%.

Leaf area index retrieval based on canopy reflectance and vegetation index in eastern China

The aim of this paper is to investigate the feasibility of using Landsat TM data to retrieve leaf area index (LAI). To get a LAI retrieval model based ground reflectance and vegetation index, detailed field data were collected in the study area of eastern China, dominated by bamboo, tea plant and greengage. Plant canopy reflectance of Landsat TM wavelength bands has been inversed using software of 6S. LAI is an important ecological parameter. In this paper, atmospheric corrected Landsat TM imagery was utilized to calculate different vegetation indices (VI), such as simple ratio vegetation index (SR), shortwave infrared modified simple ratio (MSR), and normalized difference vegetation index (NDVI). Data of 53 samples of LAI were measured by LAI-2000 (LI-COR) in the study area. LAI was modeled based on different reflectances of bands and different vegetation indices from Landsat TM and LAI samples data. There are certainly correlations between LAI and the reflectance of TM3, TM4, TM5 and TM7. The best model through analyzing the results is LAI = 1.2097*MSR + 0.4741 using the method of regression analysis. The result shows that the correlation coefficient R2 is 0.5157, and average accuracy is 85.75%. However, whether the model of this paper is suitable for application in subtropics needs to be verified in the future.

The natural basis of the formation of the dual-nuclei structural model

The dual-nuclei spatial structure is composed of a regional central city, a port city and their spat ial relations in certain regions. In general, this spatial structure c ould be found in most of the coastal regions or regions along big rivers. In terms of the mechanism, the dual-nuclei structure is the result of the s patial interaction and the complementary characteristics of the center city and the port city. The 'marginal function' of the port city and its relationship with the central city has long been discussed in th e literature. On the one hand, drainage area is the main natural geo graphical background of the formation of the dual-nuclei spatial structure; the refore, we can build a theoretical geographic structure that is based on the drainage area. On the other hand, vicissitude of the coastline al so has important influence on the formation of the dual-nuclei spatial structure. It is especially meaningful if we can notice this when w e examine deeply the research on the spatial structure of delta.

New discovery of submerged forest remains in Shenhu bay, Fujian Province, and its environmental significance

The authors have made a further investigation on the tidal-zone paleoforest remains found in the Shenhu bay, Fujian Province. By surveying (scale of 1︰500) andnumbering of the remains, 65 tree trunks were found. They are relatively concentrated in three different regions fromsouth to north. Their growing ages ranged from 45 a to 100 a. 22 ancient trunks?sections with low degree of carbonizationshow that the paleoforest was composed of Keteleeria Carr., Morus L. and Gleditsia L. 14C dating shows that thepaleoforest was living in 9 420—6760 aBP. Later it stoppeddeveloping and was buried by the alluvial aggradation caused by the sea level rise.