莫莫格湿地干-湿界面优势植物种群动态分析

莫莫格湿地从高河漫滩底端到顶端选取有代表性的植物群落片断作为固定观测样带,并设置6个观测样方,生长季5月、7月、9月3次观测结果表明,小叶章优势种群5月份密度最高达1154-1594株/平方米,7月种群数量下降,9月有所升高;踏头苔草优势种群5-7月份密度在3 414-7 193株/平方米,9月份种群数量大幅度下降;土壤相对含水量低地段小叶章种群相对优势度大,土壤相对含水量高地段踏头苔草种群相对优势度大,局部地段生长季内有相对优势度相互替代过程,莫莫格湿地干-湿界面上小叶章和踏头苔草两个种群可以共存。     

Modelling land cover transitions: A solution to the problem of spatial dependence in data

Raster-based spatial land cover transition models (LCTMs) are widely used in landscape ecology. However, many LCTMs do not account for spatial dependence of the input data, which may artificially fragment the output spatial configuration. We demonstrate the consequences of ignoring spatial dependence, thus assigning probabilities randomly in space, using a simple LCTM. We ran the model from four different initial conditions with distinct spatial configurations and results indicated that, after 20 simulation steps, all of them converged towards the spatial configuration of the random data set. From an ecological perspective this is a serious problem because ecological data often exhibit distinct spatial configuration related to ecological processes. As a solution, we propose an approach (region approach) that accounts for spatial dependence of LCTM input data. Underlying spatial dependence was used to apply spatial bias to probability assignment within the model. As a case study we applied a region approach to a Vegetation Transition Model (VTM); a semi-Markovian model that simulates forest succession. The VTM was applied to approximately 500,000 ha of boreal forest in Ontario, at 1 ha pixel resolution. When the stochastic transition algorithms were applied without accounting for spatial dependence, spatial configuration of the output data became progressively more fragmented. When the VTM was applied using the region approach to account for spatial dependence output fragmentation was reduced. Accounting for spatial dependence in transition models will create more reliable output for analyzing spatial patterns and relating those patterns to ecological processes.This revised version was published online in May 2005 with corrections to the Cover Date.     

Economics of foliar fungicides for hard red winter wheat in the USA southern Great Plains

Grain yields of winter wheat (Triticum aestivum L.) in the southern Great Plains are often reduced by the presence of foliar diseases. This study was conducted to determine whether the application of foliar fungicides is an economically optimal management strategy. The effects of fungicide treatment on commercially available hard red winter wheat varieties with differing levels of genetic resistance (i.e., resistant, intermediate, and susceptible) to foliar diseases were investigated at two locations, Apache and Lahoma, OK, USA, for the harvest years 2005–2012. Two fungicides were rotated between the two locations and applied at approximately Feekes growth stage 9–10.5. When averaged across years, plots to which fungicide was applied generated greater average net returns than plots that did not receive fungicide for susceptible varieties at Apache, and for resistant, intermediate, and susceptible varieties at Lahoma. However, foliar fungicide application was not economical in every year at either location suggesting fungicide use should be reassessed each year given that profitability depends on year specific yield potential, prices, and foliar disease conditions. At both locations high disease incidence occurred in all but one site-year when the average March through May relative humidity exceeded 65%. Additional research would be required to determine the relationship between weather, including relative humidity, and disease incidence, and to develop an economic threshold for treatment decision aid.     

Economic performance and comparative riskiness of different management practices for control of botrytis fruit rot in florida strawberry

Florida strawberry farmers usually rely on weekly calendar fungicide applications to prevent yield loss from Botrytis fruit rot (BFR). The Strawberry Advisory System (SAS), which helps optimize the timing of fungicide applications, is an additional tool in the farmers' arsenal of disease control options. This study uses data from two-year production trials in Florida combined with historical strawberry prices to measure the economic performance of the Calendar and SAS-based BFR management practices under output price risk and producers' risk preferences. We use Monte Carlo simulation to model the effect of the variability in weekly output prices on farm returns. Results reveal that the traditional calendar-based system is not the least risky BFR management option as growers expected to be. SAS-based options such as SAS-Switch and SAS-Luna would be preferred by both risk-neutral and risk-averse producers and are recommended under high disease pressure conditions.     

基于Markov随机场的猪肉糜微结构图像模拟

利用Markov随机场和Gibbs分布理论，建立了猪肉糜微结构图像的随机场模型，然后通过迭代方法，对不同微结构的猪肉糜图像进行了随机模拟，同时对随机模拟图像和原始图像作了对比分析。糜状食品物料微观结构图像的分析和模拟是定研究其微结构模式形态对流变特性影响的关键问题。通过从已知流变特性反演糜状食品物料微结构的几何形态，可以更深入地探讨、研究微结构形成的动力学机制和过程，进而沟通流变特性和微结构形态之间的联系，从而为定量描述糜状食品物料的流变特性提供了条件。     

Simulation of soil types in Teramo province (Central Italy) with terrain parameters and remote sensing data

Soil surveys are an essential source of information for land management although a limited budget often reduces the amount of data available. Even if the dataset is limited, geostatistics can provide a valid estimation tool through a weighted moving average interpolation (kriging). Often, however, the spatial variability of soil properties appears smoothed and short range variability is underestimated by this kind of interpolation technique. A more realistic distribution of a given variable on the territory can be obtained through models based on stochastic simulation.     

FSWM: A hybrid fuzzy-stochastic water-management model for agricultural sustainability under uncertainty

A hybrid fuzzy-stochastic water-management (FSWM) model is developed for agricultural sustainability under uncertainty, based on advancement of a multistage fuzzy-stochastic quadratic programming (MFSQP) approach. In MFSQP, uncertainties presented in terms of fuzziness and randomness can be incorporated within a multilayer scenario tree, such that revised decisions are permitted in each time period based on the realized values of the uncertain events. Moreover, fuzzy quadratic terms are used in the objective function to minimize the variation of satisfaction degrees among the constraints; it allows an increased flexibility in controlling the system risk in the optimization process. Results of the case study indicate that useful solutions for the planning of agricultural water management have been obtained. In the FSWM model, a number of policies for agricultural water supply are conducted. The results obtained can help decision makers to identify desired water-allocation schemes for agricultural sustainability under uncertainty, particularly when limited water resources are available for multiple competing users.     

Responses of subshrub sagebrush rangeland in North-Western China to changes in livestock numbers and rainfall over 10 years (2004–2013)

Seriphidium transiliense, or subshrub sagebrush, is one of the most important forage resources for livestock in many arid lands, but such resources have been threatened by overgrazing for a long time. A 2013 vegetation survey of an original sagebrush rangeland (2400?ha) in the Tianshan Mountains revealed that nearly half of the area once under sagebrush has been replaced by annual species. This is due to the continual and rapid increase in livestock numbers over the past 30?years. Three smaller sites with different grazing scenarios: no grazing (Site N), a decline (Site 1), and an increase (Site 2) in livestock numbers, were selected to monitor recent changes (from 2004 to 2013) in vegetation biomass and the degree of dominance by sagebrush. Supplanting happened at Site 2 but little occurred at Site 1. There were significant differences between Site 2 and Site 1 in standing biomass in Spring and Summer, but no significant differences in Summer between Site 1 and Site N. The supplanting of sagebrush marks the completion of a dynamic process – in which rainfall plays a crucial role – of damage to sagebrush from heavy grazing in drought years and its rehabilitation by light grazing in some good years. Plant biomass loss was greatest when the land was first subjected to heavy grazing. Sagebrush tends to exist as a sole-dominant species rather than a companion species in sagebrush communities. This suggests that sagebrush continued to survive in pockets where grazing pressure had declined.     

耕地细碎化、耕地质量认知与化肥施用效率 ——基于湖北省水稻种植户的调查数据

在中国倡导农业农村绿色发展的大背景下,化肥投入的政策导向逐渐由增量增产转变为减量增效,如何提高化肥施用效率成为当前重点关注的问题。本文依据湖北省水稻种植户微观调查数据,运用随机前沿法测算水稻种植户化肥施用效率,并在此基础上运用CLAD模型进一步分析耕地细碎化程度与耕地质量认知对化肥施用效率的影响。结果表明:当前水稻种植户化肥施用效率仅为63.85%,若完全消除效率损失,化肥施用效率仍有36.15%的提升空间;耕地细碎化程度显著降低了化肥施用效率,可能与农户的避险行为有关;耕地质量认知显著促进了化肥施用效率提升,说明农户对耕地质量的科学认识能够改善化肥施用效率。因此,提出加快耕地整合与耕地连片经营法律法规建设,加速耕地细碎化治理经验与创新结合,加强引导农户对化肥施用的正确认知,推行科学种植生产模式以提升化肥施用效率的政策建议。     

早显性水稻三系不育系乐3A的选育

乐3A是用IR超级稻与金23B杂交F3代的优良单株与矮败型不育系协青早A测交,并经多代回交转育而成的籼稻三系不育系.该不育系配合力强,异交习性好,且具有早熟不完全显性的特点.配制的杂交组合优质,早熟,抗倒性强.2012年8月,该不育系通过了四川省农作物品种审定委员会技术鉴定,所配组合乐3优727、乐3优2275于201...