Wang Zongming

Comparison of different methods for corn LAI estimation over northeastern China

Leaf area index (LAI) is a crucial variable in all kinds of ecosystem, climate and crop yield models, describing the fluxes of energy, mass and momentum between the surface and the planetary boundary layer. To accurately determine the corn LAI, several methods of LAI estimation have been evaluated in this investigation, including vegetation indices, principal component analysis (PCA), the neural network method (NN), the look-up table (LUT) inversion from PROSAIL model and the Hybrid model. Comparisons were conducted based on field-measured corn canopy hyperspectral reflectance and LAI data over northeastern China. In order to fairly compare the LAI estimation performance of different methods, the groundmeasured data were separated into two sets (modeling data and validation data), except the LUT and hybrid methods of PROSAIL-based. The results indicated that the PCA method delivered the best performance for corn LAI estimation (with maximum R2 = 0.814 and minimum RMSE = 0.501) in this study. The hybrid model and EVI provided moderate results. Comparatively, the LUT and NN methods were less successful and NDVI provided the worst corn LAI estimation performance in this study. The PCA method shows great potential for performing well on corn LAI estimation from hyperspectral information. PCA can avoid the reflectance saturation defect of dense canopy in a certain extent, can utilize hyperspectral reflectance data much more effectively than other methods, and is not limited by the band numbers, it can also reduce noise and provide an great correlation with LAI from the hyperbands or the multibands reflectance.

Detecting modes of cyanobacteria bloom using MODIS data in Lake Taihu

Detection of cyanbacteria blooms in Taihu using vegetation index data from MODIS was carried out since cyanbacteria blooms broke out in May 2007.The results showed that MODIS was able to detect cyanobacteria bloom effectively.Algorithm of band ratio between infrared and red band and values of NDVI or EVI can be used to analyze the distribution of algae.However,the former two were difficult to distinguish high-turbid water from algae or identify areas with low density of cyanbacteria,which resulted in the magnified or reduced areas of algae,while the latter one could constrain background noise properly mainly from water and suspended matter.Therefore,based on the digital number values(DNs)of EVI band,an approximately actual distribution of algae was induced.The study showed that satellite observations could be effectively applied to cyanobacteria bloom real-time monitoring system for Lake Taihu.

Estimates of loss in ecosystem service values of Songnen plain from 1980 to 2000

Ecosystem services are premises for human beings to exist and develop in the world, and it is of importance to study effects of land use change on ecosystem functions. Songnen plain, located in Northeast China, is one of the national key bases for agricultural production. Because there were remarkable variations in land use in recent years, it can supply specific foundation for protection and restoration of regional eco-environment to explore changes in its values of ecosystem services. This study aims to qualify long-term changes in land use of Songnen plain from 1980 to 2000, and to explore the impact of land use change on ecosystem services. With 2-period land use data using RS and GIS, this paper analyzed changes in land use and in ecosystem service values using the ecosystem service value coefficients (VC) put forward by Costanzaet al. Results showed that from 1980 to 2000, area of rangeland, water area and wetlands and area of cropland decreased, but urban area and unused land increased. Due to cropland’s comparatively low VC and comparatively high VC of wetlands and water area, increment in cultivated land could not offset the total decrement in regional ecosystem service values because of the decrease in area of wetlands and water area. Meanwhile, city sprawl has also led to loss of ecological values. Total ecosystem service values of the study area reduced dramatically, from 34,926.10 × 106

A GIS-based Tupu analysis of dynamics of saline-alkali land in western Jilin Province

to 31,744.54 × 106

Dynamics and driving force of lake changes in northeast China during 2000-2010

in the period 1980-2000. This represents a 9.11% net decline in annual value of ecosystem services in the study area.

Spectral absorption properties of particulate matters in the Shitoukoumen Reservoir of Changchun City

Based on Tupu theory, this paper studied the dynamic changes, conversion modes, expansion intensity and landscape attributes of the saline-alkali lands in Changling County, Zhenlai County and Da’an City of the western Jilin Province in 1980–2000 with the help of GIS. The results show that the saline-alkali land rather sharply increased in Da’an during 1995–2000; the main conversion processes in the three counties were from grassland to saline-alkali land and from saline-alkali land to grassland; and the typical shapes, spatial expansion speed and mode, and landscape attributes of the saline-alkali land were different in the three counties, which were closely related to local topography, predominant wind orientation, water resources distribution, etc. The corresponding spatial expansion mode was marginality in Changling, random in Zhenlai and more kernels in Da’an, respectively. Landscape attributes also responded to the spatial-temporal dynamic changes of the saline-alkali land and the landscape indices of Da’an fluctuated greatly. The frame of this research may provide fundamental reference for landscape analysis and give some suggestions for regional sustainable development.

Spatial Distribution Characteristics of Non-Point Source Pollution of Xingkai Lake Irrigation District Based on L-THIA Model

Based on Landsat TM and ETM remote sensing images in 2000,2005 and 2010 and an object-oriented classification method,this paper extracted information on the temporal and spatial change characteristics and the driving forces for lake areas in northeast China during the past 10 years( 2000-2010). The results showed that during the past 10 years,the area of those lakes has reduced from 12234.02 km2to 11307. 58 km2,with a greater shrinking rate in the later five years( 2005-2010). Meanwhile,natural lake area has significantly reduced while artificial lake area slightly increased during the past 10 years. In the study area,lake shrinkage in the northwest is less than that in the southeast,resulted in the centroid moving to the northwest. Those changes resulted from both natural factors and human activities,and the coupled effects greatly accelerated local environment changes.

Climate Change Character in the Special Sand Area of the Areas Encircling Beijing: A Case Study on the Counties of Zhangbei,Huailai and Fengning

The Shitoukoumen Reservoir, an urban water resource of Changchun City, was chose as a represent case of waters in Northeast of China, and then its spectral absorption properties of particulates were analyzed using the field data on June 13th and September 23rd 2008, respectively. Results showed that the content of total suspended matters (TSM) was higher but content of chlorophyll-a (Chl.a) was lower in June than that in September. The spectral curves of TSM were similar to that of tripton. Tripton contributed much more than phytoplankton in the absorption by TSM. In September, the contribution coming from phytoplankton slightly increased, which resulted in an obvious absorption peak around 440nm in the spectral absorption curves of TSM. Absorption by tripton at 440nm had a good relationship with TSM but not with Chl.a. The absorption of phytoplankton in Shitoukoumen Reservoir was generally low. Chl.a held the majority of the pigment composition and had good exponential relationships with its absorption at 440nm and 675nm, respectively. The average values of phytoplankton specific absorption coefficient at 440nm and 675nm in June were 0.0483m2/mg and 0.0263m2/mg respectively, while the data in September were 0.0337m2/mg and 0.0187m2/mg respectively.

ANN-BP model for Chl-a concentration estimation with in-situ collected hyperspectral refelctance in Lake Chagan, Jilin Province

Agriculture has been identified as the largest contributor of non-point source (NPS) pollution of surface and ground water systems globally. Estimation of non-point source pollution under different land uses is an important task in non-point pollution control in China. Taking Mishan city in Xingkai lake irrigation district as the study area, with the help of GIS and RS technology, the long-term average pollution loads in Mishan city were estimated using the Long-Term Hydrologic Impact Assessment (L-THIA) model. The spatial distribution characteristics of the pollutants were analyzed, including total nitrogen, nitrate nitrogen, total phosphorus and suspended solids. Results indicated that the spatial distribution of the four non-point pollutants is quite identical. The total loads of four pollutants were different under different land use types, and the agricultural land had the most important impact on non-point pollution in the study area. Forests and grassland contributed more to the retention of the pollutants in this area. The result of this research showed that L-THIA model is available for the spatial distribution of non-point pollution and it can provide the service for planning and management of the watershed.

An algorithm on extraction of saline-alkalized land by image segmentation based on ETM + Image

采用张北、丰宁、怀来建站以来气象资料 (气温、地表温度、降水、风速 ) ,分析了研究区 40余年的气候变化特征。结果表明 :2 0世纪 70年代以来研究区温度上升的速度持续增加 ;其中 1 985年是研究区气候变化的一个转折点 ,1 985年以前气候变化幅度较大 ,1 985年以后变化趋于稳定。冬季气候特征变化较其它各季节显著 ,年均风速与年均温度呈负相关关系