Establishment of apparent quantum yield and maximum ecosystem assimilation on Tibetan Plateau alpine meadow ecosystem

The alpine meadow is widely distributed on the Tibetan Plateau with an area of about 1.2×106kn2. Damxung County, located in the hinterland of the Tibetan Plateau, is the place covered with this typical vegetation. An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux of alpine meadow from July to October,2003. The continuous carbon flux data were used to analyze the relationship between net ecosystem carbon dioxide exchange (NEE) and photosynthetically active radiation (PAR), as well as the seasonal patterns of apparent quantum yield (α) and maximum ecosystem assimilation (Pmax).Results showed that the daytime NEE fitted fairly well with the PAR in a rectangular hyperbola function, with α declining in the order of peak growth period (0.0244 μmolCO2 · μmol-1pAR) ＞early growth period ＞ seed maturing period ＞ withering period (0.0098 μmolCO2 · μmol-1pAR).The Pmax did not change greatly during the first three periods, with an average of 0.433mgCO2· m-2· s-1, i.e. 9.829 μmolCO2· m-2· s-1. However, during the withering period, Pmax was only 0.35 mgCO2 · m-2 · s-1, i.e. 7.945 μmolCO2 · m-2 · s-1. Compared with other grassland ecosystems, the α of the Tibetan Plateau alpine meadow ecosystem was much lower.     

岩石变形破坏的熵突变过程与破坏判据

在岩石的变形破坏过程中,当进入不稳定的破裂发展阶段之后,系统不断调整结构抵抗外力的扰动,裂纹向局域集中的有序方向发展,应变能不断耗散,并以应变能的耗散为媒介,使系统与外扰动所追加的负熵流产生能量流通,也使系统熵值和系统的维数逐次降低,这一阶段岩石系统远离平衡态,岩石的破坏是系统熵的突变过程。基于这一认识,并在验证应变能分布与结构块度分布模式的一致性的基础上,推导出包含了结构因素和能量分布的熵表达式;对熵表达式进行平衡分析获得局部突变的分岔集,得到了岩石局部破坏的熵折迭突变破坏准则;同时,探讨了熵表达式所表征的结构有序度的尖点突变性,解出岩石系统的分岔集,这个分岔集就是岩石系统熵突变的整体破坏准则。     

Turbidity and suspended sediment dynamics in small catchments in the Nepal Middle Hills

The Himalayan environment has, until recently, been perceived to be in a critical state of environmental decline, resulting from rapid population growth and associated land‐use change. Recent research, however, has emphasized the difficulty of developing an objective appraisal of the state of the environment in a region where empirical data are scarce and unstructured and where an understanding of the spatial and temporal dynamics of natural environmental processes remains highly uncertain. This paper presents results from an intensive three‐year project designed to help address the regional empirical deficit, establish detailed baseline environmental data and to gain an insight into storm period and seasonal suspended sediment dynamics. The instrumentation, calibration and analysis of high‐frequency infrared turbidimetric records from a number of small subcatchments in the Nepal Middle Hills are reported. Storm period and seasonal variation in turbidity and suspended sediment are examined and hysteresis patterns explored and explained. A variety of methods to estimate seasonal suspended sediment yield in a mixed land‐use catchment are examined, and found to vary by up to a factor of five. Despite the inherent uncertainty, all estimates of catchment sediment yield are found to be high with respect to erosion plot studies from the local area, and this suggests the importance of riparian and channel erosion as major sediment sources, a finding consistent with other regional studies. Copyright © 2000 John Wiley & Sons, Ltd.     

Predicting agricultural drought in eastern Rajasthan of India using NDVI and standardized precipitation index

In the present study, prediction of agricultural drought has been addressed through prediction of agricultural yield using a model based on NDVI-SPI. It has been observed that the meteorological drought index SPI with different timescale is correlated with NDVI at different lag. Also NDVI of current fortnight is correlated with NDVI of previous lags. Based on the correlation coefficients, the Multiple Regression Model was developed to predict NDVI. The NDVI of current fortnight was found highly correlated with SPI of previous fortnight in semi-arid and transitional zones. The correlation between NDVI and crop yield was observed highest in first fortnight of August. The RMSE of predicted yield in drought year was found to be about 17.07 kg/ha which was about 6.02 per cent of average yield. In normal year, it was 24 kg/Ha denoting about 2.1 per cent of average yield.     

湖北省县域粮食单产影响因素的空间异质性研究

在城镇化进程快速推进耕地保护形势严峻的背景下,粮食单产的区域差异研究对地区粮食安全具有重要意义。本文以湖北省粮食单产数据为基础,采用探索性数据分析方法和地理加权回归模型揭示省内县域粮食单产的空间关系和影响因素的空间异质性。结果表明:湖北省县域粮食单产具有显著的空间自相关特征,整体水平稳中有增。农村劳动力、化肥施用量、农村机械总动力和有效灌溉面积比对粮食单产具有正向促进作用和一定的空间分异规律,对农村用电量呈现出先正后负的影响,各因素的空间异质性显著。结合县域现状和因素的区域特质采取对应的有效措施应对粮食安全问题具有深远的现实意义。     

Regional yield estimation for winter wheat with MODIS-NDVI data in Shandong, China

The significance of crop yield estimation is well known in agricultural management and policy development at regional and national levels. The primary objective of this study was to test the suitability of the method, depending on predicted crop production, to estimate crop yield with a MODIS-NDVI-based model on a regional scale. In this paper, MODIS-NDVI data, with a 250 m resolution, was used to estimate the winter wheat (Triticum aestivum L.) yield in one of the main winter-wheat-growing regions. Our study region is located in Jining, Shandong Province. In order to improve the quality of remote sensing data and the accuracy of yield prediction, especially to eliminate the cloud-contaminated data and abnormal data in the MODIS-NDVI series, the Savitzky–Golay filter was applied to smooth the 10-day NDVI data. The spatial accumulation of NDVI at the county level was used to test its relationship with winter wheat production in the study area. A linear regressive relationship between the spatial accumulation of NDVI and the production of winter wheat was established using a stepwise regression method. The average yield was derived from predicted production divided by the growing acreage of winter wheat on a county level. Finally, the results were validated by the ground survey data, and the errors were compared with the errors of agro-climate models. The results showed that the relative errors of the predicted yield using MODIS-NDVI are between −4.62% and 5.40% and that whole RMSE was 214.16 kg ha⁻¹ lower than the RMSE (233.35 kg ha⁻¹) of agro-climate models in this study region. A good predicted yield data of winter wheat could be got about 40 days ahead of harvest time, i.e. at the booting-heading stage of winter wheat. The method suggested in this paper was good for predicting regional winter wheat production and yield estimation.     

Sediment transfer in an extremely low-gradient,low-relief and highly buffered system: Darwin Harbour catchment,northern Australia

Abstract

Sediment yields from and sediment transfer within catchments of very low relief and gradient, which make up about 50% of Earth’s surface, are poorly documented and their internal sediment dynamics are poorly known. Sediment sources, their proportionate contributions to valley floors and sediment yield, and storage are estimated using fallout radionuclides ²¹⁰Pb_(ex) and ¹³⁷Cs in the catchments that drain into Darwin Harbour, northern Australia, an example of this understudied catchment type that appears to be globally at the extreme end of this category of catchments. Unchannelled grassy valley floors (dambos, or seasonal wetlands) trap ～90% of the sediment delivered from hillslopes by sheet and rill erosion. Further down valley, small channels transport ～10% of the sediment that escapes from the dambos, and the remaining sediment comes from erosion of the channels. In this case, the fractional sediment storage is very high as a result of the existence of dambos, a landform that depends for its existence on low gradients.     

无公害刺参稳产健康养殖新技术

本文针对目前刺参养殖中存在的问题,简单明了叙述刺参无公害健康养殖一系列新技术和新方法,对推动海参养殖业持续、稳定、健康发展,起到积极作用和效果。     

厦门海域渔业资源评估

以初级生产力和渔业统计资料为材 ,分别应用Tait沿岸海域生态系能流分析法、营养动态法和Cushing等 3种模式 ,估算厦门沿岸海域的渔业资源自然生产量。同时 ,分别应用Schaefer和Fox两种剩余产量模式估算最大持续产量和最大持续捕捞力量。前 3种模式估算该海域的资源生产量分别为 2 0 1 0 5t,1 8463t和 1 7489t,平均 1 8686t。后两种模式估算最大持续产量平均值分别为 9639t和 91 0 4t。估算的最大持续捕捞力量 :5种作业综合总功率为 1 5976kW ;以厦门机定置渔船单位功率渔捞效率为标准估算的总功率为 2 7351kW ;以厦门机刺网渔船单位功率渔捞效率为标准估算的总功率为 432 1 3kW。 1 997年实际渔获量和捕捞力量均超过了估算的最大持续产量和最大持续捕捞力量。文中还讨论了捕捞力量的调整问题。     

Introducing a transferable fishing day management regime for Pacific Island countries

On 1 December 2007, eight ‘Small Island Developing States’ in the Western and Central Pacific Ocean implemented a management regime restricting the total number of days fished by tuna purse seine vessels within their waters, commonly referred to as the Vessel Day Scheme (VDS). The VDS is seen as one component of management arrangements to reduce fishing mortality on bigeye and yellowfin tuna, constrain fishing effort, and increase the rate of return from access fees by Distant Water Fishing Nations.