稻田水质模型研究和应用进展

水稻生产环境特殊、生产过程中病虫草害严重,导致农药使用品种多、频次高.部分农药会淋失到周围水体中,对水体的潜在污染风险较高.随着农药监测和田间试验成本的不断提高,数学模型已成为农药登记过程中不可或缺的一部分.稻田水质模型(RICEWQ模型)作为欧洲稻田农药暴露评估最可靠和应用最广泛的模型,主要用于预测淹水稻田土壤和积水中的农药浓度,在我国也得到了初步应用.本文简要介绍了RICEWQ模型的系统结构、农药归趋的主要过程、模型的输入输出,综述了国内外相关的研究进展,以期推进RICEWQ模型在我国的应用,并为相关研究提供参考.     

Ecological distribution and phenology of an invasive species, Cardamine hirsuta L., and its native counterpart, Cardamine flexuosa With., in central Japan

Cardamine hirsuta is a European species that was recently introduced into Japan and its wide distribution has been confirmed in the Kanto district. To understand mechanisms of the recent spread of C. hirsuta in Japan, a comparative study of the alien species and its native congeneric species, C. flexuosa, was conducted. Habitat preferences, phenology and seed germination were examined. Cardamine hirsuta and C. flexuosa showed distinctive habitat-preferences; the former was most common in open habitats created by recent man-made constructions, and the latter was common in rice paddy fields and surrounding areas. The results indicate that C. flexuosa is a year-long annual, with a mixed phenology of summer and winter germination and growth. Seed dormancy during summer was relatively weak for C. flexuosa, and some plants that germinated early in summer reproduced during the same summer–autumn period. Plants that germinated in late summer and autumn behaved as winter annuals. In rice paddy fields, C. flexuosa is a winter annual because germination is prevented by submergence during summer. Plants flower during the following spring and complete their life cycle before the fields are flooded for rice cultivation. Cardamine hirsuta showed strong seed dormancy during summer and behaved as a typical winter annual. Seeds of C. hirsuta were intolerant to submergence in water, a condition that breaks seed dormancy of C. flexuosa. The results explain the absence of C. hirsuta from rice paddy fields. It was concluded that the spread of C. hirsuta is attributable to the recent expansion of urban habitats created by human activity and has occurred without direct competition with C. flexuosa. Considering recent urbanization in many areas, it is suggested that C. hirsuta has been spreading rapidly in Japan.     

Multi-tracer identification of nutrient origin in the Hii River watershed,Japan

This study aimed to evaluate the loading of nutrients of agricultural origin. We investigated monthly nutrient concentrations at 11 stations located in the Hii River, Japan. The nitrogen and oxygen stable isotope ratios in nitrate were applied to distinguish the origin of nitrogen, i.e., from fertilizers applied to paddy fields or from sewage. Although total nitrogen (TN), presumably from transboundary air pollution, was mainly loaded during the cooler season, nitrate originating from fertilizers applied to paddy fields became the main source of nitrogen in the river water during the warmer season. Phosphorus was mainly added in particulate form, and showed increased loading at the upstream stations in the warmer season, but not in the cooler season. Potassium and magnesium—components of fertilizers—showed an increasing trend in the downstream section of the paddy fields. Our results suggest that controlled application of fertilizers is necessary to decrease the nitrogen loads originating from farmlands, particularly from paddy fields. Since the nitrogen isotope of TN in fertilizer showed significantly lower values (mean value ?4.6 ‰) than that in river water (mean value 1.8 ‰) or treated water (mean value 21.9 ‰), we could use these values to determine the contribution of TN from fertilizers to river water quality, and can use them to monitor fertilization levels in watersheds.     

A water quality analysis system to evaluate the impact of agricultural activities on N outflow in river basins in Japan

We have developed a personal-computer-based water quality analysis system for river basins. The system estimates potential N outflow by model and calculates actual N outflow from monitoring data. For the former it uses the potential load factor method to estimate annual nitrogen load from various sources and runoff potential from each area of land in a basin. For the latter it analyzes water quality monitoring data in relation to meteorological data. We used the system to analyze N outflow in basins around Lake Kasumigaura and the Yahagi River in central Honshu, Japan. The land around Lake Kasumigaura is rather flat, and about 25% is periodically flooded for rice and lotus cultivation. The land around the Yahagi River is mountainous, and much less land is flooded. In the Yahagi River basin the actual N outflow agreed closely with the potential. However, the actual N outflow in the basin around Lake Kasumigaura was much less than the potential, suggesting that a large part of the N load is denitrified in flooded soils. This further indicates that a sequence of different land uses including flooded rice fields is an important factor determining N outflow in basins in Japan. On the basis of the above analyses, we incorporated a denitrification model into the system that enables us to estimate N balance in a designated basin;this system may be helpful in the formulation of scenarios of land use andsoil management for improving water quality.     

A water quality analysis system to evaluate the impact of agricultural activities on N outflow in river basins in Japan

We have developed a personal-computer-based water quality analysis system for river basins. The system estimates potential N outflow by model and calculates actual N outflow from monitoring data. For the former it uses the potential load factor method to estimate annual nitrogen load from various sources and runoff potential from each area of land in a basin. For the latter it analyzes water quality monitoring data in relation to meteorological data. We used the system to analyze N outflow in basins around Lake Kasumigaura and the Yahagi River in central Honshu, Japan. The land around Lake Kasumigaura is rather flat, and about 25% is periodically flooded for rice and lotus cultivation. The land around the Yahagi River is mountainous, and much less land is flooded. In the Yahagi River basin the actual N outflow agreed closely with the potential. However, the actual N outflow in the basin around Lake Kasumigaura was much less than the potential, suggesting that a large part of the N load is denitrified in flooded soils. This further indicates that a sequence of different land uses including flooded rice fields is an important factor determining N outflow in basins in Japan. On the basis of the above analyses, we incorporated a denitrification model into the system that enables us to estimate N balance in a designated basin; this system may be helpful in the formulation of scenarios of land use and soil management for improving water quality.     

湘北丘陵林-稻系统镉的迁移

为了研究中南丘陵区林-稻系统镉的迁移规律,2012年5月下旬至9月上旬(中稻稻季)在湘北汩罗市桃林林场选择两种类型的林-稻复合生态系统针对降水、地表径流、山塘水、稻田水及其中镉含量用收支平衡法进行了原位动态研究。结果表明,(1)以降水形式从区域外输入的镉是湘北地域地表系统主要的外来镉源,镉的输入主要集中在稻季的早期;(2)镉以雨水形式输入丘陵林-稻系统后,53%被林地截留,7.5%累积于山塘,11.6%存留于稻田,其余28.9%以稻田水和稻草、谷粒的形式输出林-稻系统;(3)不同林-稻系统比较,混-稻系统对外源镉的固持功能最强,松-稻系统其次,对照系统最弱,其原因在于各系统间岗地森林郁闭度存在差异,郁闭度大能增强岗地对镉的固持能力;(4)在岗地截留镉能力较弱的情况下,山塘能够减缓系统镉的迁移强度;(5)岗地输入山塘水中的大分子有机物能加强镉在稻田中累积。综上所述,林-稻系统镉的累积与雨水常年输入镉有关,系统内岗地森林郁闭度、与有机物输出相关的森林类型影响镉在系统中的迁移和分配。     

A preliminary investigation into the use of the invasive golden apple snail,Pomacea canaliculata (Lamarck, 1822), as a water purifier and food source in the breeding ponds of the oriental weatherloach Misgurnus anguillicaudatus (Cantor, 1842)

This study investigated the feasibility of using an invasive snail, Pomacea canaliculata, as a food source and water purifier for the commercial breeding of the loach Misgurnus anguillicaudatus. The predatory potential of M. anguillicaudatus (3.5–5.5?g) against hatchling snails was evaluated in aquaria and simulated paddy fields. Some hatchling snails left the water to avoid being preyed upon by the loaches, and approximately 10 hatchlings died per day in the presence of five loaches in aquaria, whereas a weaker snail control effect was observed in the simulated paddy fields. The growth of rice seedlings (Oryza sativa) was not reduced by the presence of hatchling snails alone, but the shoot biomass of seedlings coexisting with snails was promoted after introducing the loaches. Additionally, the presence of P. canaliculata adults improved the aquatic environment in the short term for loach breeding by decreasing the turbidity of the water. Importantly, M. anguillicaudatus (12–18?g) mortality decreased and its weight increased in the presence of adult snails.     

北京市白河和潮河流域生态健康评价

选取北京市重要的饮用水源密云水库上游白河和潮河流域,结合北京山区流域生态现状,构建了涵盖水域生境结构、水生生物、生态压力和陆域生态格局与功能、生态压力5大类13项指标的评价指标体系,开展了流域生态健康评价。结果表明白河和潮河流域的健康状态整体处于良好等级,但水生生物和陆域生态格局状况相对较差。14个子流域的健康状况差异并不显著,琉璃河、白河下段、汤河上游的健康状况相对较好,潮河中下段和小汤河的健康状况相对较差。流域内不合理的畜禽养殖、岸边带种植及民俗旅游是导致流域生态健康退化的主要原因,建议加强污染负荷排放的控制和监管涉水活动对水生生境的干扰以改善流域健康状况,并重点关注可指示水生态系统早期退化的生物指数,以实现可持续性和适应性的流域管理,保障密云水库的水生态安全。     

Estimation of sensible heat,water vapor,and CO<Subscript>2</Subscript> fluxes using the flux-variance method

This study investigated the flux-variance relationships of temperature, humidity, and CO(2), and examined the performance of using this method for predicting sensible heat (H), water vapor (LE), and CO(2) fluxes (F(CO2)) with eddy-covariance measured flux data at three different ecosystems: grassland, paddy rice field, and forest. The H and LE estimations were found to be in good agreement with the measurements over the three fields. The prediction accuracy of LE could be improved by around 15% if the predictions were obtained by the flux-variance method in conjunction with measured sensible heat fluxes. Moreover, the paddy rice field was found to be a special case where water vapor follows flux-variance relation better than heat does. However, the CO(2) flux predictions were found to vary from poor to fair among the three sites. This is attributed to the complicated CO(2) sources and sinks distribution. Our results also showed that heat and water vapor were transported with the same efficiency above the grassland and rice paddy. For the forest, heat was transported 20% more efficiently than evapotranspiration.     

广西岩溶区稻田土壤优先路径的空间分布

田间土壤优先路径空间分布影响优先流的发生和运动。通过野外土壤染色示踪试验,利用形态学图像解析技术,并结合群落生态学分析方法,对广西岩溶区秸秆覆盖(CM)和非覆盖(CK)下的水稻田进行土壤优先路径空间分布研究。结果表明: 在相同的外部供水状况下,随土壤深度的增加,秸秆覆盖水稻田的土壤水平染色由整体分布向团块状聚集分布转变;非秸秆覆盖水稻田以枝状染色为主,其平均染色斑块形状系数为21.69,染色形态规则,是秸秆覆盖水稻田的1.04倍。秸秆覆盖与非覆盖水稻田的土壤优先路径均呈聚集分布,秸秆覆盖水稻田内优先路径的Morisita指数为1.28,且田间优先路径以影响半径＜1.0 mm为主(重要值0.31),非秸秆覆盖水稻田内影响半径＜1.0 mm的优先路径重要值为0.28。秸秆覆盖影响稻田土壤优先路径,有助于改善田间作物的水肥利用状况。     

Pattern of immigration of the sorghum plant bug Stenotus rubrovittatus (Hemiptera: Miridae) into paddy fields from a large source habitat

Evaluation of the landscape-level movement of Stenotus rubrovittatus (Matsumura), a major rice pest in Japan, is essential for establishing management strategies. We assessed the immigration timing and the average dispersal distance from a bank slope covered with Italian ryegrass Lolium multiflorum Lam. to paddy fields by periodic sampling in two regions in Chiba Prefecture. The immigrant densities in paddy fields increased exponentially as they approached the bank slope as a large-scale habitat of the insect. The relationship between immigrant density and distance from the source habitat fit an empirical model and theoretical model well. The theoretical model estimated the average dispersal distance during immigration: that of females was 72.0 and 92.1 m and that of males was 122.0 and 112.9 m in the respective regions. In addition, the average dispersal distance of males increased 7 days or later after the rice heading date despite the steady dispersal distance of females.     

Effects of Variations in Cadmium and Lead Levels in River Sediments on Local Foods and Body Burden of Local Residents in Non-Polluted Areas in Japan

This study was initiated to examine if variations in the concentrations of cadmium (Cd) and lead (Pb) in water environment may affect metal levels in local foods and body burden of local residents in non-polluted areas in Japan. Two nationwide databases have been made available on concentrations of Cd in locally harvested brown rice and of Cd and Pb in sediments in local river beds. These data were combined with published data on metal concentrations in polished rice, food duplicates, and blood and urine from the residents. Cd in river sediments correlated significantly with those in brown rice, food duplicates, blood, and urine. Cd in food duplicates correlated with Cd in rice. In contrast, Pb concentrations in the river sediments either did not correlate or correlated only weakly with Pb in biological materials or food duplicates. Possible implication of the different behavior between Cd and Pb regarding the intensity of correlation was discussed with reference to the different routes of exposure to the elements. In conclusions, the Cd body burden on local residents in Japan is significantly influenced by Cd levels in water in the general environment, whereas water-borne Pb did not show clear correlation with the Pb body burden.     

Development of region-specific emission factors and estimation of methane emission from rice fields in the East, Southeast and South Asian countries

Rice cultivation areas in East, Southeast and South Asia account for 89% of the world total, and field measurements of methane (CH₄) emission from rice cultivation have been widely performed in this area. In this paper, we assembled most of the measurements and developed region‐specific CH₄ emission factors. Efforts were made in order to regionalize rice fields by climate and soil properties, and to incorporate the effect of organic input and water regime on emission. Data on rice cultivation areas of 1995 were collected at subdivision level (province, state, prefecture, etc.). Total emission from these areas was estimated at 25.1 Tg CH₄ year ^{? 1}, of which 7.67 Tg was emitted from China and 5.88 Tg from India. Irrigated and rainfed rice fields contributed 70.4 and 27.5% to the total emission, respectively. Deepwater rice fields had a very small share. A high‐resolution and quality emission distribution map was constructed as the emission was directly estimated at province level and below that, a 30‐second land‐use dataset was used in order to translate the emission to grid format. As the rice cultivation area in the study region accounts for 89% of the world total, extrapolating the estimate to the global scale indicates a global emission of 28.2 Tg CH₄ year ^{? 1}. The estimate was compared with country reports made by local scientists. For some countries – such as Indonesia, Myanmar, Thailand, Vietnam, Japan, South Korea, Pakistan and the Philippines – the results of this estimate agree reasonably well with their country reports (CV < 15%). For some other countries – such as China, India and Bangladesh – there is relatively large disagreement between our estimate and their country reports. The reasons for the discrepancies were discussed.     

BasinBox: A Generic Multimedia Fate Model for Predicting the Fate of Chemicals in River Catchments

Multimedia fate models have proven to be very useful tools in chemical risk assessment and management. This paper presents BasinBox, a newly developed steady-state generic multimedia fate model for evaluating risks of new and existing chemicals in river basins. The model concepts, as well as the intermedia processes quantified in the model, are outlined, and an overview of the required input parameters is given. To test the BasinBox model, calculations were carried out for predicting the fate of chemicals in the river Rhine basin. This was done for a set of 3175 hypothetical chemicals and three emission scenarios to air, river water and cropland soils. For each of these hypothetical chemicals and emission scenarios the concentration ratio between the downstream area and the upstream area was calculated for all compartments. From these calculations it appeared that BasinBox predicts significant concentration differences between upstream and downstream areas of the Rhine river basin for certain types of chemicals and emission scenarios. There is a clear trend of increasing chemical concentrations in downstream direction of the river basin. The calculations show that taking into account spatial variability between upstream, midstream and downstream areas of large river basins can be useful in the predictions of environmental concentrations by multimedia fate models.     

我国稻田氮磷流失现状及影响因素研究进展

水稻是我国主要的粮食作物,分析现阶段我国稻田氮磷流失现状及影响因素,对明确不同区域水稻化肥减施潜力具有重要意义.本研究对我国主要稻区地表径流氮磷流失现状特征和降雨、种植模式、栽培技术、施肥管理、水分管理方式及其他影响因素进行了总结.六大稻区全氮(TN)、全磷(TP)径流损失量范围分别在5.09～21.32和0.70～3.22 kg·hm^-2,均以华南双季稻区最高,TN径流损失量以华北单季稻区最低,TP径流损失量以西南高原单双季稻区最低.各稻区农户习惯施肥的水稻田田面水TN、TP峰值普遍高于径流水.水稻施肥后一周内为氮磷流失高峰期.与优化施肥相比,农户习惯施肥仍具有20%左右的氮磷减施潜力.各因素中,降雨和施肥管理是影响稻田径流氮磷流失的主要因素,而施肥管理和水分管理则最具可控性,具体调控措施包括化肥减量、施用新型肥料、有机肥代替化肥和节水灌溉等.整体上我国稻田氮磷流失风险在南方更突出.应以资源高效利用模式进行水稻种植以降低养分流失风险.未来研究应侧重稻田面源污染监测、氮磷流失风险评估、氮磷流失特征和机理、化肥减施增效新技术等方向.     

Using Landsat images to map habitat availability for waterbirds in rice fields

Rice fields are an important habitat for waterbirds. Knowledge of the availability of this habitat is important since the reduction in the area of natural wetlands has converted rice fields into vital refuges. This paper presents a method for mapping habitat availability in rice fields according to different waterbirds’ habitat preferences and examining its phenology during the crop cycle. Data from bird censuses carried out in the Doñana rice fields were analysed to determine the habitat preferences of 22 species of waterbird at different stages in the rice production cycle. Discriminant function analysis of seven Landsat images was used to classify paddy field stages. The phenology of habitat availability in rice fields during autumn and winter was examined. Waterfowl and waders preferentially used the ‘flooded’ and ‘mudflats with water’ paddy field stages, respectively, and the ‘rice growing’ and ‘dry’ stages were rejected by waterbirds. The area of preferred habitats within rice fields increased during autumn; subsequently, the area of the ‘flooded’ paddy fields decreased in January, whereas that of ‘mudflats with water’ remained available until March. The automatic classification of paddy field stages with Landsat images allowed habitat availability for different species of waterbirds to be monitored and provides relevant information for understanding behavioural and population responses in waterbirds that use rice fields. After examining the phenology of the availability of habitat and comparing it with dates of arrival and departure of migrant waterbirds, best crop practices could be defined to favour waterbirds (i.e. adjusting harvest, ploughing and flooding dates). Taking into account climatic change and loss of wetlands this method could help in the integration of agriculture and conservation, in particular in areas where there is no remaining natural wetland habitat.     

Redistribution of carbon and nitrogen through irrigation in intensively cultivated tropical mountainous watersheds

This study aimed at tracing and quantifying organic carbon and total nitrogen fluxes related to suspended material in irrigation water in the uplands of northwest Vietnam. In the study area, a reservoir acts as a sink for sediments from the surrounding mountains, feeding irrigation channels to irrigate lowland paddy systems. A flow separation identified the flow components of overland flow, water release from the reservoir to the irrigation channel, direct precipitation into the channel, irrigation discharge to paddy fields and discharge leaving the sub-watershed. A mixed effects model was used to assess the C and N loads of each flow component. Irrigation water had an average baseline concentration of 29?±?4.4?mg?l^?1 inorganic C, 4.7?±?1.2?mg?l^?1 organic C and 3.9?±?1.6?mg?l^?1 total N. Once soils were rewetted and overland flow was induced, organic C and total N concentrations changed rapidly due to increasing sediment loads in the irrigation water. Summarizing all monitored events, overland flow was estimated to convey about 63?kg organic C ha^?1 and 8.5?kg?N?ha^?1 from surrounding upland fields to the irrigation channel. The drainage of various non-point sources towards the irrigation channel was supported by the variation of the estimated organic C/total N ratios of the overland flow which fluctuated between 2 and 7. Nevertheless, the majority of the nutrient loads (up to 93–99%) were derived from the reservoir, which served as a sediment-buffer trap. Due to the overall high nutrient and sediment content of the reservoir water used for irrigation, a significant proportion of nutrients was continuously reallocated to the paddy fields in the lowland throughout the rice cropping season. The cumulative amount of organic C and total N load entering paddies with the irrigation water between May and September was estimated at 0.8 and 0.7?Mg?ha^?1, respectively. Therefore deposition of C and N through irrigation is an important contributor in maintaining soil fertility, and a process to be taken into account in the soil fertility management in these paddy rice systems.     

Effects of free-air CO2 enrichment (FACE) on CH4 emission from a rice paddy field

Methane (CH₄) is a particularly potent greenhouse gas with a radiative forcing 23 times that of CO₂ on a per mass basis. Flooded rice paddies are a major source of CH₄ emissions to the Earth's atmosphere. A free‐air CO₂ enrichment (FACE) experiment was conducted to evaluate changes in crop productivity and the crop ecosystem under enriched CO₂ conditions during three rice growth seasons from 1998 to 2000 in a rice paddy at Shizukuishi, Iwate, Japan. To understand the influence of elevated atmospheric CO₂ concentrations on CH₄ emission, we measured methane flux from FACE rice fields and rice fields with ambient levels of CO₂ during the 1999 and 2000 growing seasons. Methane production and oxidation potentials of soil samples collected when the rice was at the tillering and flowering stages in 2000 were measured in the laboratory by the anaerobic incubation and alternative propylene substrates methods, respectively. The average tiller number and root dry biomass were clearly larger in the plots with elevated CO₂ during all rice growth stages. No difference in methane oxidation potential between FACE and ambient treatments was found, but the methane production potential of soils during the flowering stage was significantly greater under FACE than under ambient conditions. When free‐air CO₂ was enriched to 550 ppmv, the CH₄ emissions from the rice paddy field increased significantly, by 38% in 1999 and 51% in 2000. The increased CH₄ emissions were attributed to accelerated CH₄ production potential as a result of more root exudates and root autolysis products and to increased plant‐mediated CH₄ emissions because of the larger rice tiller numbers under FACE conditions.     

稻鸭共作对稻田营养生态及稻米品质的影响

通过稻、鸭之间的共生互作,共生期不施用任何农药和化肥,进行优质无公害水稻生产。结果表明,稻鸭共作的除草效果达到99．4％以上,病虫害基数明显降低;水体营养物质和溶解氧增大;土壤速效养分有一定提高,但成熟后土壤速效P、速效K较基础肥力有一定降低;植株N、P、K吸收量增加;产量明显提高,构成因素中成穗率、实粒数和结实率增加;稻米的加工品质、外观品质、营养品质及蒸煮品质得到改善,尤以降低垩白率效果最为明显;稻田生态系统综合效益明显提高。     

中国稻田蜘蛛群落结构研究初报

通过近３０ａ的调查研究，中国稻田蜘蛛群落的物种组成，经不断分类鉴定，有２２科、１０８属、３７５种，其中已定出种名的有３３７种，未定种名的３８种。２２科中有优势科８个，优势属１３个，及１７个优势种，但优势科中不一定都含有优势属或优势种。