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1.
In this study, trophic state indicators, total phosphate, algal chlorophyll and Secchi disk transparency and zooplankton community of Lake Choghakhor was studied monthly between May 2003 and April 2004. This lake is a shallow ecologically and economically important water body in eastern part of Iran. Crop farming and recreational activities are examples of the human impact around and within the lake, leading to a loading of DIN (Dissolved Inorganic Nitrogen) and TP (Total Phosphate) into the lake. Now submerged plants especially Myriophyllum spicatum has covered almost the entire lake and dense macrophyte beds (Polygonom amphibium), located on the East Southern end of the lake appear to act as a sink for these nutrients. Lake Choghakhor appeared to be in a macrophyte dominated clear water state with low TP (annual mean: 24 +/- 15 microg L(-1)) and chlorophyll a (annual mean: 3 +/- 1.28 microg L(-1)) concentrations and very high Secchi depth. The grazing pressure of dominant pelagic filtering zooplankton Daphnia longespina did not seem to be significant in determining the low phytoplankton crop expressed as chlorophyll a. We expect that sequestering of nutrients by submerged plants and associated epiphytes are the dominant stabilizing mechanisms suppressing the phytoplankton crop of Lake Choghakhor. 相似文献
2.
播期是影响小麦产量与品质的一个重要因素,冬小麦生产管理对播期的及时和准确监测有强烈需求。遥感数据源的日趋丰富及遥感定量化水平的日益提高,为大面积、低成本监测小麦播期提供了可能。本文对冬小麦播期遥感监测的研究进展进行了回顾,系统归纳了当前国内外播期遥感监测方法,分析了目前冬小麦播期遥感监测中存在的问题。推进高时空分辨率遥感数据的使用、强化多尺度传感器遥感数据融合算法的应用、开展冬小麦生长前期不同播期光谱数据的挖掘、探索冬小麦生长前期光谱与上茬作物时序遥感数据的综合及尝试遥感数据与作物模型同化方法的借鉴是冬小麦播期遥感监测的未来发展方向。 相似文献
3.
Evaluation of MODIS NDVI and LST for indicating soil moisture of forest areas based on SWAT modeling
Park Jong-Yoon Ahn So-Ra Hwang Soon-Jin Jang Cheol-Hee Park Geun-Ae Kim Seong-Joon 《Paddy and Water Environment》2014,12(1):77-88
This study examined the capability of remotely sensed information gained using the terra moderate resolution imaging spectroradiometer (MODIS) normalized difference vegetation index (NDVI) and land surface temperature (LST) to explain forest soil moisture. The soil and water assessment tool (SWAT) was used for the analysis. Nine years (2000–2008) of monthly MODIS NDVI and LST data from a 2,694.4 km2 watershed consisting of forest-dominant areas in South Korea were compared with SWAT simulated soil moisture. Before the analysis, the SWAT model was calibrated and verified using 9 years of daily streamflow at three gauging stations and 6 years (2003–2008) of daily measured soil moisture at three locations within the watershed. The average Nash–Sutcliffe model efficiency during the streamflow calibration and validation was 0.72 and 0.70, respectively. The SWAT soil moisture showed a higher correlation with MODIS LST during the forest leaf growing period (March–June) and with MODIS NDVI during the leaf falling period (September–December). Low correlation was observed in the year of frequent rains, regardless of the leaf periods. 相似文献
4.
Jinling Zhao Chao Xu Linsheng Huang Dongyan Zhang Dong Liang 《Paddy and Water Environment》2016,14(4):439-449
Remote sensing has facilitated the identification of acreage and spatial distribution of field crops with obvious seasonal dynamics. The primary objective of this study is to identify the spatial patterns of double-season early rice, single-season middle rice and double-season late rice of Hunan Province and Yuanjiang City, China, in 2010, using two kinds of time series remotely sensed imagery: 8-day composite MODIS surface reflectance product data (MOD09A1) and HJ-1A/B satellite images with a 4-day revisit period. The available MODIS and HJ-1 CCD images of transplanting and heading stages were first assured in accordance with the schedules of local traditional paddy fields tillage. Based on the MOD09A1 data product, time series normalised difference vegetation index (NDVI) images were calculated and smoothed to remove the noise and the atmospheric effects. Second, the spatial distribution and planting acreage of three types of rice of Hunan Province were derived from combining the enhanced vegetation index and land surface water index according to the water background and variation characteristics of NDVI values at transplanting and heading stages. Conversely, a two-test procedure was used to finish the identification of paddy rice in Yuanjiang City using time series HJ-CCD imagery. The first test was to derive the potential rice pixels using the NDVI image (?NDVI) between heading and transplanting stages, and the second test was to remove the non-rice pixels using maximum likelihood supervised classification. The experimental results showed that three types of rice were mainly distributed along the Dongting Lake Basin in Hunan Province and the relative errors were ?10.99, 1.46 and ?5.87 %, respectively, while they were primarily planted in the northern plains of Dongting Lake in Yuanjiang City, where the relative errors were 12.1, 16.7 and 0.8 %, respectively. We conclude that transplanting and heading stages are the best phenological combinations for identifying paddy rice through remote sensing time series analysis, and this study can provide a basis for evaluating paddy rice yield on a large scale . 相似文献
5.
Background
South America is one of the most species diverse continents in the world. Within South America diversity is not distributed evenly at both local and continental scales and this has led to the recognition of various areas with unique species assemblages. Several schemes currently exist which divide the continental-level diversity into large species assemblages referred to as biomes. Here we review five currently available biome maps for South America, including the WWF Ecoregions, the Americas basemap, the Land Cover Map of South America, Morrone's Biogeographic regions of Latin America, and the Ecological Systems Map. The comparison is performed through a case study on the Seasonally Dry Tropical Forest (SDTF) biome using herbarium data of habitat specialist species.Results
Current biome maps of South America perform poorly in depicting SDTF distribution. The poor performance of the maps can be attributed to two main factors: (1) poor spatial resolution, and (2) poor biome delimitation. Poor spatial resolution strongly limits the use of some of the maps in GIS applications, especially for areas with heterogeneous landscape such as the Andes. Whilst the Land Cover Map did not suffer from poor spatial resolution, it showed poor delimitation of biomes. The results highlight that delimiting structurally heterogeneous vegetation is difficult based on remote sensed data alone. A new refined working map of South American SDTF biome is proposed, derived using the Biome Distribution Modelling (BDM) approach where georeferenced herbarium data is used in conjunction with bioclimatic data.Conclusions
Georeferenced specimen data play potentially an important role in biome mapping. Our study shows that herbarium data could be used as a way of ground-truthing biome maps in silico. The results also illustrate that herbarium data can be used to model vegetation maps through predictive modelling. The BDM approach is a promising new method in biome mapping, and could be particularly useful for mapping poorly known, fragmented, or degraded vegetation. We wish to highlight that biome delimitation is not an exact science, and that transparency is needed on how biomes are used as study units in macroevolutionary and ecological research. 相似文献6.
Ji-Hong Jeon Chun G. Yoon Jong-Hwa Ham Kwang-Wook Jung 《Paddy and Water Environment》2005,3(2):93-101
A field experiment was performed at two Korean research sites to evaluate water and nutrient behavior in paddy rice culture
operations for 2 years. One site was irrigated with groundwater, whereas the other site was irrigated with surface water.
Both sites received average annual rainfall of about 1,300 mm, and about 70–80% of it was concentrated during July–September
coinciding with rice growing season. Although most of the nutrient outflow was attributed to plant uptake, nutrient loss by
surface drainage was substantial. The simplified computer model, PADDIMOD, was developed to simulate water and nutrient behaviors
in the paddy rice field. The model predicts daily ponded water depth, surface drainage, and nutrient concentrations. It was
formulated with a few equations and simplified assumptions, but its application and a model fitness test indicated that the
simulation results reasonably matched the observed data. It is a simple and practical planning model that could be used to
evaluate nutrient loading from paddy rice fields alone or in combination with other complex watershed models. Further validation
might be required for general application of the PADDIMOD to the simulation of paddy rice fields with various agricultural
environments. 相似文献
7.
《Plant Production Science》2013,16(4):352-364
AbstractIn this study, a deterministic algorithm named Ensemble Square Root Filter (EnSRF), an algorithm significantly improved from the Ensemble Kalman Filter (EnKF), was used to integrate remotely sensed information (ASD spectral data, HJ-1 A/B CCD and Landsat-5 TM data) with a wheat (Triticum aestivum L.) growth model (WheatGrow). The analyzed values of model variables, leaf area index (LAI) and leaf nitrogen accumulation (LNA), were calculated based on EnSRF without perturbed measurements. Independent datasets were used to test EnSRF and the root mean square error (RMSE) values were 0.81 and 0.82 g m-2, with relative error (RE) values of 0.15 and 0.13, for LAI and LNA, respectively. RMSE values for LAI and LNA were 1.39 and 1.70 g m-2, respectively (RE, 0.28 and 0.34) based on EnKF, 1.17 and 1.80 g m-2 (RE, 0.24 and 0.35), respectively, based on the WheatGrow model alone, and 0.97 and 1.25 g m-2 (RE, 0.21 and 0.24), respectively, based on the remote sensing models. These results indicated that the LAI and LNA values based on EnSRF matched the measured values well compared with the EnKF, WheatGrow and remote sensing models. In addition, the predicted results are consistent with the temporal and spatial distribution of winter wheat growth status and grain yields in the study area, with RE values of less than 0.2 and 0.1 for LAI and LNA, respectively. These results provide an important approach for simulating winter wheat growth status based on combining remote sensing and crop growth models. 相似文献
8.
The existing irrigation schedule of most rice-growing areas in Jilin Province is not in full compliance with the Water Requirements Law of the rice; these discrepancies affect the yield of rice to some extent. Thus, research on rice water regulations and selection of an appropriate water production function model (WPFM) is very important. In this study, according to the water demand characteristics of rice, we used drought treatments separately during the tillering, jointing booting, flowering, and milky stages. Evapotranspiration and yield data were obtained using a test pit experiment and production measurements in 2011 and 2012, respectively. Five commonly used WPFMs (the Jensen, Blank, Minhas, Stewart, and Singh model) were selected for this study, and the water sensitivity index of each model was calculated based on the evapotranspiration, yield, and the model equations. The Jensen model was found to be the most suitable WPFM for this region; furthermore, a mathematical relationship between the water sensitivity index and days after rice planting was established. These results have important theoretical and practical implications for guidelines regarding rice irrigation in Jilin Province. 相似文献
9.
10.
稻田高产节水灌溉方式的研究 总被引：11，自引：0，他引：11
1984～1988年在中国水稻研究所实验场排水与其它农业措施相结合，采用节水灌溉措施和高产灌溉制度，综合考虑对田面水、土壤水、地下水和雨水的统一管理利用和合理调节控制，通过大田、小区、测坑试验和生产实践，提出了适合当地条件的节水高产灌排方式、地下水埋深度和排水量。这种水综合运用，既可节约灌溉用水量，减少灌水次数，还可降低排涝水量，减轻排涝能耗费用。 相似文献
11.
Guénaëlle Corre-Hellou Nadine Brisson Marie Launay Joëlle Fustec Yves Crozat 《Field Crops Research》2007
Competition for soil resources plays a key role in the outcome of intercropping systems. In cereal–legume intercrops, competition for soil nitrogen during the vegetative phase greatly influences the final performance of the intercropped species. However, there is a lack of knowledge on the main factors involved in interspecific soil N competitive interactions between species. The dominance of cereals over legumes is often attributed to their faster growing rooting system. Nevertheless, using only field experimental approaches makes it difficult to isolate the effect of one factor because of the strong interactions between processes and the environment. Given the complexity of intercropping systems, dynamic simulation models can be especially helpful for testing hypotheses about the key factors driving competition between species. The present work was designed to investigate, under non-limiting water conditions, through an experimental and modelling approach, whether differences in root depth penetration among pea and barley grown together determined competition for soil N and dry matter accumulation (DM) by each species during the vegetative phase. This hypothesis was tested through several simulated scenarios generated using the STICS crop model. The model was first used to compare competition for soil N according to differences in root depth penetration rates between species. This rooting depth penetration effect was then studied at three levels of soil N supply leading to different degrees of N demand and N stress. A field experiment carried out in 2003 including pea–barley intercrops grown either with 130 kg N ha−1 or without any fertilizer was used to test the model. Experimental results of aboveground biomass, nitrogen accumulation, N2 fixation and rooting depth monitored regularly during the crop cycle were compared to simulated results. The simulated responses of the intercrops were in agreement with the observations from the experimental dataset. Using the model, it is clear that faster root growth in barley gives it access to more soil nitrogen than pea during the vegetative phase. However, this advantage, which is limited to the vegetative phase, only affects the outcome of the intercrop when soil N supply is low. With higher soil N supplies, soil N sharing is not affected by the differences in rooting depth penetration between species. It appears that with higher N supplies, the differences in N demand between species have more influence on species dominance than differences in rooting depth. 相似文献
12.
A. Bhadra A. Bandyopadhyay R. Singh N. S. Raghuwanshi 《Paddy and Water Environment》2013,11(1-4):331-341
A water balance model for paddy is developed primarily based on the principle of conservation of mass of soil–water within the root zone. The water balance for paddy is different from that of field crops because paddy requires standing water in the field during most of its growth period. This model requires soil, crop and meteorological data as inputs. This user friendly model was developed using computer programmes C and Visual Basic (VB) 6.0. It simulates various water balance components such as evapotranspiration, deep percolation, surface runoff and depth of irrigation water and ponding depth in the field on a daily basis. For estimation of deep percolation loss, physically based saturated and unsaturated flow processes are incorporated into the model to consider ponding (if there is standing water in the field), saturation (if moisture content of soil is in between field capacity and saturation) and depletion (if moisture content of soil is below field capacity) phases of paddy field. This article presents development of a user friendly water balance model for paddy and also its validation using published data. 相似文献
13.
In closed water bodies, such as reservoirs and lakes, where the exchange with external waters is usually small, the wind-induced
flow significantly affects their water quality by mixing the surface waters and transfering heat down through the water column.
However, the circulation caused by wind acting on the water surface can be influenced by the excessive growth of aquatic plants
in summer, which may make their water quality to become worse. Therefore, understanding the response of the closed water bodies
to winds acting on the water surface is of great significance in examining and maintaining their water quality in good condition.
With that significance, this research has been done to build a two-dimensional, unsteady, laterally averaged model for simulating
the circulation and water quality in closed water bodies. To verify the model, the Tabiishidani reservoir located in Sasaguri
town, Fukuoka prefecture, Japan, was chosen as a case study. To illustrate the methodology of the research, water temperature
of the reservoir was chosen to calibrate the model. After calibration, the model was applied to simulate water temperature
in the Tabiishidani reservoir under different patterns of meteorology. The results of simulation clarified the change in water
temperature distribution along the depth of the reservoir under the different patterns of meteorology. This research shows
that the model can be a suitable tool for simulating the circulation and water temperature in closed water bodies. Moreover,
the model can be extended to simulate the circulation and any variable of water quality in closed water bodies with the coverage
of aquatic plants on the water surface. 相似文献
14.
Changing climate has increasingly exacerbated droughts and floods in Taiwan; therefore, it is important to understand the
actual demand of transferring Taiwan’s agricultural water. This estimation model could help the water resource agencies to
develop appropriate mechanisms for transferring agricultural water, as well as bargaining tools for water-related negotiations.
In this study, an inverse demand function estimation model for transferring agricultural water was established, and the water
usage statistics derived from the water charge agreements, covering the period from January 1989 to December 2006 and including
drought and non-drought periods, regarding the charging of water management fees and water usage fees, was applied to the
estimation model in our empirical research. The agreements were made between irrigation associations and water companies,
industrial water users, and science and industrial parks, for the purposes of strengthening irrigation management, building
usage, and disposal of remaining water. The empirical research was conducted to estimate the demand for transferring agricultural
water using double-log regression model for panel data, and analyzed with random effects models for regular conditions and
drought periods. The results showed that the inverse demand function developed in this study was able to pass Largrange multiplier
test, and adjusted R
2 for the regression were high, fitting the random effects model showing good compatibility with the sample selection. From
the results, we can verify the estimation models to forecasting models. The significant results not only prove that the model
could provide important market information for the commercialization of water resources, but water resource agencies could
also make use of this important information to develop suitable mechanisms for transferring agricultural water, as well as
bargaining tools for negotiation of water transactions. 相似文献
15.
《Plant Production Science》2013,16(4):269-279
AbstractSpectral reflectance of differentially-managed rice canopies was measured over an entire growing season and analyzed with special attention to linking remotely sensed information with a simple growth model. The fraction of absorbed photosynthetically active radiation (fAPAR), which is often used as a key variable in simple process models, was well correlated writh spectral vegetation indices (VI). VIs, such as NDVI and SAVI, were derived from the ratio of reflectance at two wavelengths (R660 nm and R830 nm) and a new VI, termed the normalized difference ND [R1100 nm, R660 nm], was derived from the difference of Rl 100 nm and R660 nm divided by their sum. These close relations between fAPAR and Vis were expressed by exponential formulae with different parameters for the periods before and after heading. These indices became less sensitive to fAPAR when fAPAR was larger than 0.4. The use of R1100 nm and R1650 nm with R660 nm and R830 nm in multiple regression significantly improved the prediction accuracy of fAPAR. A close linear relation was found between a spectral ratio R830 nm/R550 nm and leaf nitrogen content during the ripening period although it was not the case before heading. Results suggested that R830 nm/R550 nm was effective for estimation of leaf nitrogen content when the paddy field was regarded as a big leaf. The total amount of leaf nitrogen was well correlated with ND [R1100 nm, R660 nm] ; nevertheless, the sensitivity was lost when the total amount of leaf nitrogen was greater than 3 g m?2. Multiple regression analysis showed that a combination of four spectral bands R550 nm, R830 nm, R1650 nm and R2200 nm was useful for estimation of the total amount of leaf nitrogen. Remotely-sensed nitrogen variables would be a potential model parameters in a simple model. A real-time recalibration module based on a simplex algorithm was developed and proved effective in linking the remotely-sensed fAPAR with a simple model. This approach was also useful for inferring the physiological parameters such as radiation use efficiency for each rice canopy without destructive sampling. The re-parameterization and/or re-initialization with remotely-sensed information was demonstrated to be a practical and effective approach, especially for operational purposes. 相似文献
16.
While studying water quality in the Tatara river, we realized that the river has various hydraulic and topographic characteristics
when flowing through different regions. Because of these specific characteristics, the application of the existing models
for simulation of its water quality may not be appropriate due to limitations in the models themselves. Therefore, we developed
a mathematical model that is suitable for short-term simulations of water quality in rivers with characteristics similar to
the Tatara river. The main foundation of the model is the one-dimensional transport equation established on the basis of the
mass conservation law. To solve this equation numerically, it was discretized by the method of finite-difference approximations,
and an algorithm has been programmed in Fortran 90. To verify the model, the Tatara river was chosen as a case study. Water
temperature, dissolved oxygen, hydraulic parameters in four typical blocks of the river, and meteorological data of the study
area, have been observed and used to test the model. By calibrating the model with different series of data collected from
the designated blocks, all results have shown a good fit between simulated data and the observed one. Therefore, the model
could be a reliable tool for simulating water quality in medium- and small-sized rivers over a short-term period. This research
has also indicated the changing tendencies of water temperature and dissolved oxygen in Tatara river in response to different
meteorological patterns over a daily 24-h period. Besides, the model could be improved to simulate other water quality variables,
which would be studied further. 相似文献
17.
《水稻科学》2017,(6)
Genotyping by sequencing(GBS) is the recent approach of next-generation sequencing technique for discovering and genotyping single nucleotide polymorphisms(SNPs) in crop species. Genotypic variation studies(SNPs and insertion-deletions/In Dels) were performed using four rice lines based on GBS data by aligning to the reference genome Nipponbare. Local aromatic rice landrace Tulaipanji was crossed with Ranjit, and two distinct lines were identified from the progenies: one line with awns and aroma traits and the other without awns and aroma. Total number of SNPs and In Dels identified were 52 810 and 4 327 at read depth 10, respectively. Out of the total polymorphic SNPs/In Dels, 16 490 were intergeneric, 7 812 were inside gene, and 4 435 were intronic. Phylogenetically, Tulaipanji was closer to the reference genome nipponbare. Based on recurrent parent genome analysis, out of 10 013 alleles, 92.52% was introgressed into progeny-awn from Tulaipanji and 7.48% from Ranjit, whereas progeny-awnless carried 89.19% alleles from Ranjit and only 10.81% alleles from Tulaipanji. In addition, progeny-awn was the highest heterozygous(83.88%) and progeny-awnless was the least(2.24%) at this fifth generation of recombinant inbred lines. These SNP variations may be linked to the phenotypic traits and can be utilized in crop improvement through linkage mapping. These results suggest that adding a high density of SNP markers to a mapping or breeding population through GBS has a great value for numerous applications in rice breeding and genetics research. 相似文献
18.
Agustin Pimstein Arnon KarnieliSurinder K. Bansal David J. Bonfil 《Field Crops Research》2011,121(1):125-135
Given the importance of potassium (K) and phosphorus (P) contents to wheat yield and grain quality, and the very little experience that has been gained on nutritional monitoring of other than nitrogen using remotely sensed technologies, a study was undertaken to explore the possibility of identifying these mineral stresses using spectral data. Canopy spectra and biophysical data were collected from commercial and experimental fields in India and Israel. Traditional and newly developed vegetation indices, together with Partial Least Squares (PLS) regression models, were calculated in order to predict potassium and phosphorus contents from the wheat canopy spectral data. Results show that the application of PLS and specific narrow bands vegetation indices reached significant levels of accuracy in the retrieval of K and P levels, in comparison to traditional broad band indices. Additionally, it was observed that a significant improvement is obtained when the mineral total content is considered instead of the relative content. Therefore it was suggested that the biomass should also be retrieved from the spectral data. Finally, as very different crop conditions were included in this study, it was possible to confirm that the level of accuracy in the retrieval of K and P levels is related to the quality and variability of the data used for calibrating the models. 相似文献
19.
The subject of this study is water management in low-lying paddy fields. The objective of this study is to quantify the water requirement, and estimate an appropriate volume and facilitate management of irrigation water in areas where it is difficult to estimate the flow rate continuously. A field observation was conducted at a 14-ha study site located in the Kuwabara area, Fukuoka City, southwest of Japan, to evaluate water management conditions in the command area of the reservoir. This site near the reservoir was selected, because it was impossible to understand the water supply situation in the entire command area. The farmers in this region have been unable to retain sufficient irrigation water. The observation results indicate that the water depth fluctuates widely in every irrigation canal. The canals are frequently empty because rotational irrigation is conducted by water managers; this makes quantifying the flow rate in the irrigation canal very difficult. To quantify the water requirement, an improved tank model was introduced. The accuracy of the model was examined by comparing the observed and calculated ponding depths at a paddy field. The simulation results agreed with the observed data. Using this model, water management for the reduction of water managers’ labor was simulated. Simulation results indicated that rotational irrigation effectively reduces labor and saves irrigation water. 相似文献
20.
Simulation of the influence of poor soil drainage on grass-based dairy production systems in Ireland
A dairy cow system simulator, Dairy_sim , designed for assessing the interaction of climate and management on dairy cow production, based on rotational grass grazing, was further developed by integrating a soil water model. The soil water model was based on the concept of soil water deficits, and influenced the growth of grass herbage in the simulator when there was an excess of water over field capacity and when water content in the soil was approaching wilting point. The soil water model was tested using baseline meteorological data (1961–1990) and then the system simulation was parameterized and tested for poorly drained soils using data from a research farm in the west of Ireland. After testing, the effects of regional differences in climate on system management on well- and poorly drained soils were compared. Down-scaled Global Climate Model (GCM) data for the baseline years (1961–1990) were used for this purpose. These data resulted in slightly more favourable weather than that recorded. It was found that the simulator was capable of generating results in good agreement with published data for dairy production on poorly drained soils. The regional analysis showed dairy farms on well-drained soils out-performed their equivalents on poorly drained soils and, in general, were able to sustain higher stocking rates by 0·6–0·9 cows ha−1 . Dry matter production was around 1·5–3 t ha−1 greater per annum on well-drained soils compared to poorly drained soils. The simulator, Dairy_sim , also captured a large difference in the requirement for housing and forage between the well and poorly drained soils. The simulation model can now be used to evaluate interactions between soils, systems and weather, and is thus a more useful tool for developing practical advice and for evaluating the impacts of possible climate change. 相似文献