Rapid population growth and economic development in the Asia-Pacific Region has resulted in serious local, national and regional environmental problems such as floods, droughts, forest fires, dust storms, air, water and soil pollution, desertification, salinization, water resource depletion, and soil erosion. Such problems are a serious constraint to sustainable development in the region. The Integrated Environmental Monitoring (IEM), a sub-project of Asia-Pacific Environmental Innovation Strategy (APEIS) project, aims to develop an integrated environmental monitoring system that can be used to detect, monitor and assess environmental disasters, degradation and their impacts in the Asia-Pacific Region. The system employs data primarily from the MODIS (Moderate Resolution Imaging Spectrometer) sensor on the Earth Observation System (EOS)-Terra/Aqua satellite, as well as those from ground observations. The IEM achievements in the last two years can be concluded as follows: (1) IEM established an integrated monitoring network system under the auspices of the National Institute for Environmental Studies (NIES) in Japan and the Institute of Geographic Sciences and Natural Resources Research (IGSNRR) of the Chinese Academy of Sciences in China, and expanded it with additional participation by the National University of Singapore and the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia. The network has already covered most of the Asia-Pacific Region. (2) IEM also established two data-analyzing centers at NIES in Japan and IGSNRR in China. These centers store a wide variety of satellite data produced not only by different sensors, but also by various ground-based measurements. A data-processing system for deriving the higher order environmental indices from MODIS data was also completed. The products can be used to detect and monitor environmental disasters/degradations and indices for vulnerabilities. They can also be used as inputs to a range of models for assessing climate change, ecological conditions and agricultural production. (3) Although numerous satellite-derived indices in the Asia-Pacific Region have already been produced by other projects/organizations, most have yet to be calibrated or validated by ground-truth data so that they might contain significant uncertainties. Thus, IEM established five validation sites in a variety of ecosystems in China, as follows: grassland, dry field, paddy field, forest, and semi-arid area. The data gathered at these sites include information related to radiation, meteorology, and soil and vegetation. The data can be remotely downloaded through a satellite network. Using these consistent and quality assured datasets, IEM can produce accurate and reliable information specific to the region. (4) A MODIS data based integrated watershed management model is developed to assess conditions and changes in ecological goods and services such as fresh water resources and food production. With this model and the above information, strategic policy options for sustainable watershed management will be explored.
Water vapor, heat and CO2 fluxes as well as ecosystem characteristics have been measured at 5 sites in different ecological systems at Haibei (grassland), Yucheng (dryland), Taoyuan (paddy field), Qianyanzhou (forest land) and Fukang (saline desert) in China since the spring of 2002. These sites were set up initially for the validation of satellite data obtained from MODIS station established for the project "Asia-Pacific Environmental Innovation Strategy (APEIS)", which was launched in 2001 by the Ministry of the Environment of Japan, so we called them APEIS-FLUX system. The main objective of this study was to validate estimates of surface temperature, evaporation, soil moisture, as well as leaf area index and net primary productivity (NPP) generated by MODIS satellite data, and to understand the mechanisms controlling the exchanges of energy, water vapor and CO2 across a spectrum of time and space scales. The results show that both latent flux and CO2 flux are much higher in the crop field than those in the grassland and the saline desert, but the sensible heat flux is in the opposite way. Using the observed data to validate the MODIS data products, we found that different products have very different correspondence, which suggests that the algorithm to be used to process MODIS products needs to be revised by using the local dataset. We used the APEIS-FLUX data as the inputs and parameters of Biome-BGC model, and found that the revised model can simulate wheat growing process, heat and carbon fluxes over it well.
The located experiment was conducted in Taoyuan Experimental Station of Agroecosystem Research of the Chinese Academy of Sciences. The result indicated both fertilization systems and water management pattern significantly affected the transformation processes and production efficiency of the nutrient and water. The production efficiency was 4.5 kg/kg for N fertilizer application only, but 8.8 kg/kg and 8.0 kg/kg for NP and NPK fertilizer combined, respectively. The yield-increase rate was 56.8% in the organic residue recycle case, however it could be up to 80.1% based on organic residue combined application with NPK fertilizer. The yield-increase rate was 62.8% with fertilizer application development and 80.1% with inorganic-organic fertilizer combined. In other words, in the case of optimum fertilization system, the largest contribution portion of inorganic fertilizer applied was 38.4% while that of inorganic-organic fertilizer combined was 44.4%. There were obvious differences in water transformation in paddy fields with different irrigation patterns. Water distribution in the paddy field with control irrigation (CI) showed that transpiration and evaporation accounted for 1/2, plowing and preparing land for 1/6, plant constitution for 1/21, field leakage for 1/14, and other environment consumption (maintenance) for 1/5. Whereas, the proportion of plowing and preparing land and field leakage was too large under rain-fed (RF) conditions. Water needed for irrigation was about 5838 m3/hm2 and the annual variation efficiency of irrigation water required was 8.3%, of which 71% for growing late rice. Irrigation between July and September consumed 68% of the total water required. Irrigation production rate was 3.67 kg/m3 in rice biomass and 1.48 kg/m3 in grain output. It was concluded that for growing double harvest rice in the Yangtze Valley, the thinner water layer must be kept in early rice and the periodical ration irrigation was very important for late rice.
An eddy-covariance system and a micrometeorological station were installed at south periphery of Gurbantonggut Desert in April of 2002. Evaluation of the data showed that the measurements of sensible heat (H), latent heat (LE) and CO2 fluxes were reliable. However, a special phenomenon was revealed from detailed analysis on the diurnal and seasonal changes of the fluxes: when LE fluxes signified a strong water shortage and hence severe water stress should have been applied on the plants, CO2 fluxes indicated that the photosynthesis of the plant community was not affected. This was obviously against generally-accepted theory on plant-water relations. No concrete evidence available so far can explain this phenomenon, but we may speculate that local shrub plant might not benefit from the rainfall. Being a salinized desert, its upper soil layer contains high salt content. Thus shrub roots could not develop and survive at upper layer of the soil. On the contrary, roots might develop mainly at deep soil layers near the groundwater table. Therefore, whether rainfall wetted the upper soil layer or not, plant water condition was not affected, but the evapotranspiration (LE) was. The measured change of LE fluxes mainly came from evaporation of soil surface and CO2 fluxes were mainly determined by plant photosynthesis. Since the former is mainly influenced by soil water condition near soil surface and the latter determined by soil water condition near the groundwater table, it is just reasonable that the two aspects are not correlated. Thus, the phenomena reported here occurred under the combined local climatic, botanical and soil conditions and it is not really against the principle of plant-water relations in general.
In this paper, species composition, biomass change pattern and differences of 2 types of alpine vegetations in the northeastern part of Qinghai were analyzed. Monitoring results showed that there were significant differences in soil humidity moisture and evaporation between Kobresia humilis meadow and Potentilla fruticosa shrub which grew in the same regions with similar altitudes and precipitation but different topography. The species constitute 2 types of alpine vegetations which are different due to limitations of environmental factors, especially soil temperature and moisture. With respect to the general biogeography of the region, the Potentilla fruticosa shrubs, dominated by Potentilla fruticosa and accompanied with Kobresia capillifolia, Kobresia pygmaes, Festuca ovina and some forbs, are found on the northern slopes. The Kobresia humilis meadows, typical alpine meadow dominated by Kobresia humilis and accompanied with Elymus mutans, are widely distributed along the valley floor. The above-ground biomass of Kobresia humilis meadow is greater than that of Potentilla fruticosa shrub. As for underground biomass (0-40 cm), both types of vegetations maintained relatively great values during the period from May to September, but the occurrence time of its peak value and the lowest value differs from each other for the 2 types of vegetations. The annual net underground production of Potentilla fruticosa shrub is greater than that of Kobresia humilis meadow, whereas, the turnover value of underground production of Kobresia humilis meadow is greater than that of Potentilla fruticosa shrub.
The MODIS product of the land surface vapor flux (MOD16) is not yet released by NASA because some parameters in the algorithm are very unstable in the time and space scales, which are difficult to be or cannot be derived from the remote sensing data. In this study, we validated the original algorithm of MOD16 with the ground measured data from April to May in 2002 (Yucheng Ecological Experimental Station in Shandong, CAS). The result showed that the estimated vapor flux was about 20% more than the observed values. We revised the original model by adjusting the crop physiological temperature parameters and coefficients for calculating the aerodynamic resistance, and the fractional vegetation cover according to the characteristics of winter wheat in Yucheng Station. The slope of the regression line plotted with the result simulated by the revised algorithm and the field measured data was 0.9706, and the correlation coefficient (R2
By transplanting original plants/soil system into lysimeters and treating those lysimeters with five precipitation treatments: 80%, 90%, 100%, 110% and 120% of the average annual precipitation, plant productivity and soil moisture were observed. Field experiment in Yuansi county, Hebei, showed that precipitation change was a very sensitive factor influencing both the productivity and soil moisture. Precipitation increase resulted in the increase of productivity. When precipitation increased by 10%, productivity increased by about 15%. The experiment also showed that higher precipitation generally resulted in higher soil moisture, which should be the reason for productivity increase in high precipitation treatments, though good plant growth, in some treatments, might also feed back on the soil moisture change. In order to see the possible effect of both temperature and precipitation changes on soil moisture, without changing plant growth pattern, WAVES model is calibrated, validated and used for the simulation of response of soil moisture to climatic change. The simulation shows that temperature associated with precipitation decrease or no precipitation change will definitely result in the decrease of soil moisture, indicating a great possibility of plant productivity decrease. Though precipitation increase would benefit the soil moisture, however, it is showed that 10% precipitation increase will not bring any benefit to soil moisture if temperature rises by 4 oC. Precipitation rise by 10% will possibly create only a slightly favorable soil moisture condition if temperature rises by 2 oC. It is thus suggested that the positive effect of 10% precipitation increase on soil moisture will possibly be offset by roughly a temperature rise of 3 oC . As soil moisture is the key factor influencing plant productivity, plant productivity will possibly follow the same trend. However, since the effect of CO2 concentration rise on plant transpiration and plant growth is not considered in the model simulation, there are still quite a lot of uncertainties remaining. The results need to be testified by future studies.
Photosynthetically active radiation (PAR) is a key variable required by almost all terrestrial ecosystem models. Unfortunately, the current incident PAR products estimated from remotely sensed data at spatial and temporal resolutions are not sufficient for carbon cycle modeling. In this paper, a method was proposed to retrieve land surface PAR from MODIS data in non-cloudy sky. Firstly, the maximum PAR in top of atmosphere was calculated in any place and at any time. Then the atmospheric parameters, vapor and aerosol, were estimated from MODIS data. Finally, the land surface PAR was computed by radiative transfer model using atmospheric parameters and sun geometrical information. The method was used to retrieve PAR in Shandong and the result was tested by the ground data in Yuncheng station of CERN with the error less than 10%.
The Tibetan Plateau is the least human-disturbed region in the world. Its outstanding topographic features and ecological characteristics give it a fame of "Natural Lab" for global change research. An improved TEM model based on MODIS satellite data and field observations data during 2000-2002 were used to estimate annual net primary productivity (NPP) in the Tibetan Plateau. A validation by using the observed NPP at different sites shows that the estimated NPP is well agreed with the measured NPP. The simulated results show that the estimated annual primary productivity of the entire Tibetan Plateau is 302.44×1012 gC yr-1, among which forest NPP takes up 39.7% of the total, though forests comprise only 9.74% of the Tibetan Plateau region; NPP accumulation for summer is 246.7×1012 gC yr-1, which is 80% of the year total.
This paper describes a method for the estimation of the net primary productivity (NPP) by integrating remotely sensed and GIS data with a process-based ecosystem model. Hokkaido Island of Japan was selected as a case to validate our method. In order to improve the estimation accuracy, we improved the BEPS model (Boreal Ecosystem Productivity Simulator) for NPP estimation by incorporating new land cover classification logic, a robust Normalized Difference Vegetation Index-Leaf Area Index (NDVI-LAI) algorithm and employing GIS data with high quality as the input of the model. As the results of the model calculation, the mean and total NPP for the study area in 1998 was 644 g C/m2/yr and 0.078 Gt C/yr, respectively. In addition, the effect of the quality of the model input requirements on accurate NPP estimation using a process-based model was also assessed. The results show that the higher quality input data obtained from GIS datasets for a process-based model improved the NPP estimation accuracy for Hokkaido Island by about 16.6%-39.7%.
By using Terra/MODIS satellite data in 2002, the dynamic variation of surface water area and water storage in Dongting Lake was studied. We, at first, divided the whole Dongting Lake into three parts (WDL: West Dongting Lake, SDL: South Dongting Lake, EDL: East Dongting Lake from west side) according to geographical characteristics. Secondly, surface water area was detected based on the spectral deference between water and terrestrial area using satellite (Terra/MODIS) NDVI (Normalized Difference Vegetation Index) data. Thirdly, the surface water area was overlaid on the lake bottom DEM with a grid size of 50 m by 50 m, and the water level could be calculated. Finally, the water storage was obtained by times water depth (difference between water surface elevation and lake-bottom elevation.) with the grid area. The total water storage at Dongting Lake was calculated by accumulating all water column values in the whole lake. By comparing the estimated water level and storage with the measurements in the three parts of the Dongting Lake, we found that there are high correspondences between the two, which implies that our method is an effective approach to estimate water level and water storage of a large lake.
The original purpose of the TOPEX/ Poseidon was to measure sea surface height. Making use of the concept, "assuming datum plane", TOPEX/Poseidon derived water level changes data were converted to water level data. Furthermore, the rating curve between satellite-derived "water level" and in situ river discharge was established. Using this approach, the actual river discharge can be determined from TOPEX/Poseidon data without the need of the actual water level. Based on the two years (1998, 1999) TOPEX/Poseidon data and ground observed river discharge data around Datong station which is located in the lower reaches of the Yangtze River, the approach was validated. The results show that TOPEX/Poseidon data can be used to determine river discharge in the lower reaches of the Yangtze River.
In order to acquire high resolution, data fusion technique can be used to combine multiple data from different sensors. This study practices two methods of data fusion: IHS transformation method and wavelet-based method. The result showed that IHS transformation method was a relatively simple one to be used, but it can not remain all information except for three bands of RGB. However, the wavelet-based method is relatively complicated and it can get high resolution images in all bands. As an approach to scale down the resolution of images, a so-called pixel level data scaring model was used in this study. Comparisons were made from data acquired by four multi-spectral sensors (Landsat/ETM+, Terra/ASTER, Terra/MODIS, and NOAA/AVHRR) over Kushiro Marsh in Hokkaido, Japan, on September 26, 2001. To reveal the effect of the sensors' spatial resolution, simulated data are generated from the higher spatial resolution (small size pixel) data to match the lower spatial resolution (larger size pixel) data. The result shows that the Terra/ASTER images can be effectively down-scaled to the resolution of Landsat/ETM+. However, it is rarely effective to scale down both Landsat/ETM+ and Terra/ASTER images to the resolution of MODIS and AVHRR.
Aiming at water resource crisis of the Yellow River, this paper discusses the connotation of water exchange time, analyzes the change characteristics of water exchange time based on reservoir action, and then establishes numerical models of the water resident time in the mainstream of the Yellow River. The following conclusions are drawn: (1) The result indicates that the amount of renewable water per month can meet the demand of all kinds of water utilizations and Lijin profile flows naturally when the original amount of water storage in the Longyangxia reservoir is 9.343 billion m3 and water exchange time is 1.46d0; when the original amount of water storage in the Longyang Gorge Reservoir is 5.343 billion m3 and water exchange time is 1.77d0, no-flow will appear in April and May. (2) Water supply and demand are disproportional in time and space. By dispatching reservoir, the water exchange time of the Yellow River at month scale will be lengthened or shortened, which corresponds the disproportion in time and space of water supply and demand, the amount of runoff in no-flood period with reservoirs action is more 8.3 billion m3 than that without reservoirs action, which promotes the efficiency of reasonable utilization of water resources. (3) When the stage of original storage of the Longyangxia increases from 5.343 billion m3 to 18.043 billion m3, the multi-year scale water exchange time in the Yellow River is close to d0. So, reservoir action has no effect on multi-year scale water exchange time. (4) Water exchange time depends on hydrologic cycle and water balance, which controls the renewable capacity of water resources in various time scales, and determines the total amount of regional water resources accurately. All these offer scientific basis for establishing water supply system for sustainable utilization of water resources.
In order to better understand the biogeochemical process of the Changjiang (Yangtze) River and pollutant load flowed into the East China Sea from the river and provide scientific basis for eco-environmental and water resources protection, field surveys along the Changjiang River from Chongqing to Shanghai (about 2300 km long) were carried out in autumns of 1998 and 1999 through the international cooperative study between the National Institute for Environmental Studies (NIES), Japan and the Changjiang Water Resources Commission, China. In this paper, the preliminary results of water quality conducted in the joint survey were presented. From the concentration variations of SS, DOC, T-P, NH4-N, NO3-N and DT-N along the main course of the Changjiang River during both surveys of 1998 and 1999, it is evident that the concentrations of SS and nutrients in the autumn of 1999 were higher than that in the summer of 1998, because the influence of non-point pollutant source and the discharge and water level during the survey period in 1999 was much higher than that in 1998. On the other hand, the general tendency of the nutrient distribution increased from upstream to downstream along the main course of the Changjiang; the concentrations of nutrients were evidently higher in the downstream of big cities than that in the upstream of these big cities. Water quality was improved after passing through the Gezhouba Dam. It was also found that the BOD and NH4-N concentrations increased sharply after passing Dongting and Poyang lakes.
To evaluate the performance of a computer model simulating runoff in the upper reaches of the Changjiang (Yangtze) River Basin over a relatively short time interval, including examining the applicability of the input precipitation data generated from global circulation models and satellite data, we used a spatially distributed model, HSPF with the ISLSCP precipitation data for 1987 and 1988 as input data. The Nash-Sutcliffe coefficient (R2) for 5-day average stream flow was 0.94 in the calibration period and 0.95 in the verification period for the whole upper region. Moreover, the model simulated the 5-day average stream flow well in each main tributary, as shown by R2 values of 0.46 to 0.96, except that it underestimated the peak flow rates during the flood season over two years by up to 71% in the Tuojiang River and 61% in the Jialingjiang River. The ISLSCP precipitation tended to be more frequent and less intense than the measured precipitation. This was probably the main reason why the HSPF did not perform well in all regions at all times.
Though the annual total sediment load at Yichang hydro-station increased from the 1950s to the 1980s, it tended to decrease gradually in the 1990s. The reason of increase is due to violent deforestation and rapid landuse change, while that of decrease may be due to countermeasures taken to control sediment yields and lots of dams built on the upstream basins. The Jialingjiang River watershed is one of the main sources of sediments in the Changjiang river watershed, and the annual total load in the 1990s from the Jialingjiang River basin discharged into the Changjiang River reduced to about 36% of that before 1988. To clarify the reason of decrease of annual sediment-inflow rate in this basin is of great significance to sediment control related forest planning, reservoir sedimentation prevention at the Three Gorges Dam and habitat and ecosystems preservation in the Changjiang River, etc. In this study we developed a surface erosion type of sediment yield model for watershed slope, applied it to Jialingjiang River watershed in 1987, and investigated its applicability.
For implementing water resources management in the Yellow River Basin, water resources assessment is very necessary and important. The accuracy of water resources assessment relies on predictability of the hydrological cycle. Different land uses, topographical features, geological and soil conditions, and artificial water uses (mainly agricultural irrigation) determine the complexity of hydrological characteristics in this basin. With the limited observation of the river discharge, it is difficult to develop a lumped model for simulating hydrology in different sub-basins based on parameter calibration. The physically-based hydrological model can be helpful in this case. The present research attempts to incorporate all available spatial information into the hydrological modeling by a distributed approach. A physical model is developed using the physical governing equations for description of the hydrological processes. It carries out a 10-year (1980-1989) simulation of the natural hydrological cycle. Based on the hydrological simulation, the paper discusses the spatial-temporal hydrological characteristics and the status of water resources in the Yellow River Basin.
