结合植被指数与作物高度反演冬小麦叶面积指数

[目的]叶面积指数LAI(Leaf Area Index)是反映作物长势的关键参数之一。目前,基于无人机影像进行LAI反演多注重影像光谱信息的应用,但是由于高分影像存在强烈的光谱异质性以及无法区分高密闭度植被垂直方向枝叶的光谱特征等不足,在反演作物LAI时,需要探讨作物高度等结构参数对LAI反演的影响。[方法]文章以冬小麦为例,将无人机影像的光谱信息与点云数据相结合,共同构建LAI反演模型,并与单利用光谱信息的一元线性LAI回归模型进行对比,探讨作物高度信息对LAI反演精度的影响。[结果](1)无人机影像获取的点云数据能有效反演作物高度,其决定系数R~2=0.61,均方根误差RMSE=0.02;(2)基于作物高度和植被指数Ⅵ(Vegetation Index)反演LAI的二元模型(Adjust R~2=0.38,Adjust RMSE=0.55)优于单用植被指数反演LAI的一元模型(Adjust R~2=0.29,Adjust RMSE=0.59),[结论]研究表明作物高度和光谱信息结合的反演模型能够提高作物LAI的反演精度,同时表明作物高度因子在LAI反演中具有重要的应用价值。     

Complements, Substitutes, Budget Constraints and Valuation

This study employs a multi-program contingent valuation (CVM) design tosimultaneously assess the value of three ecosystem conservation programsin Alberta, Canada. The design is different from most other CVM designsand has several different features including the natural incorporation ofdirect reminders of substitute/complementary programs and budgetconstraints. In contrast to the findings of other studies, two of the environmentalprograms appear to be complements and other combinations of the programssuggest an absence of substitution effects. The multi-program model ismore informative and robust in terms of theoretical validity and expectedrelationships with demographic and recreational characteristics of therespondents.     

关于珍贵乡土用材树种资源培育的思考——以本溪市为例

文章探讨了开展珍贵乡土用材树种培育的战略意义,分析了人们对乡土珍贵用材树种的漠视和培育方面存在的问题,以及辽宁省本溪开展乡土珍贵用材树种资源培育具备的优势条件,提出了定向改培和新造林的技术思路及其方法措施。     

浅谈树种选择如何做到适地适树

本文介绍了适地适树的标准和含义,阐明了园林树木种植设计的科学性,分析了"适地适树"三条途径,强调了"适地适树"考虑因素。     

Wildlife Damage and Agriculture: A Dynamic Analysis of Compensation Schemes

We study the environmental and economic consequences of introducing a program to compensate peasants for damages caused by wildlife. We show that the widely held belief that compensation induces wildlife conservation may be erroneous. In a partially open economy, compensation can lower the wildlife stock and result in a net welfare loss for local people. In an open economy, compensation can trigger wildlife extinction and also reduce welfare. We identify the conditions leading to a reduction of the wildlife stock and discuss the implications for current and planned compensation programs in Africa and Asia.     

The Correspondence Principle: A Superfluous Tool of Economic Analysis

I analyze the evolution of trout recreational fisheries with the objective of identifying possible factors that might be driving current controversies in biodiversity policy reforms on the governance of alien and invasive species. Findings suggest that trout species have attained a cultural status, which makes it difficult to have them eradicated without facing stiff resistance from the trout-dependent sector. Results suggested that a process of leisure augmentation through environmental greed underpinned the introduction and continuance of spreading trout. With this process came also the development of a complex set of institutions that protected trout since they served an honorific role. My findings also suggest that the Ayresian thesis that all ceremonial systems are past-binding could be relaxed because ceremonial interests also envision alternative futures that can entrench and further protect ceremonial systems. To that end, these ceremonial interests facilitate path-breaking, but harmful institutional change. I extend Paul Dale Bush's concept of institutional spaces by assigning faces to the concept, resulting in expansion of possible institutional adjustment configurations. I find that this reorganization of Bush's concept tells the historical evolution of institutions of the leisure class in South Africa in a more dynamic way.     

Can People Value Protection against Invasive Marine Species? Evidence from a Joint TC–CV Survey in the Netherlands

Harmful algal-bloom species (HABs) are invasiveexotic species that are primarily introduced inNorth European waters through ballast water ofships. Some produce important damages to themarine ecosystem such as the red tides thatcause a massive destruction of marine livingresources, including fish and bottom-livinganimals. Others are responsible for theproduction of thick foams with repellent odorsand the coloration of the beach water, causingimportant damages on beach recreation. Thisarticle reports a monetary valuation study of amarine protection program. This program focuseson the prevention of HABS along the coastlineof the Netherlands. It entails the constructionof a ballast water disposal treatment in theRotterdam harbor and the implementationof a monitoring program of the water quality inthe open sea along the North-Holland beaches.The valuation study is based on a questionnaireundertaken at Zandvoort, a famous Dutchbeach resort. The economic value of the marineprotection program includes non-market benefitsassociated with beach recreation, human healthand marine ecosystem impacts. Both contingent-valuation and travel-cost methods are used.These valuation techniques have not yet beenapplied to value HABs damages. The valuationresults indicate that the protection programmakes sense from an economic perspective aslong as its cost is, in any case, less than 225 millioneuro, and possibly less than 326 million euro, depending on how survey refusals are dealt with.     

恢复水生植被对城市湖泊污染净化效能的影响

在城市湖泊中利用水生植被，可逐步恢复城市湿地生态功能。本文对比了植被恢复前后湖泊的净化效率，结果显示：水生植被恢复前后水体对CODCr的净化效果差异不明显，对营养盐的净化效果差异显著，TN的去除率提高30．8％，净去除浓度1．44mg／L，是植被恢复前的4倍；对TP的去除率提高36．8％，水体Ohl—a浓度整体逐步降低，至15μg／L左右，与植被恢复前同期相比降低6．5倍；浮游植物种群密度下降，蓝藻细胞密度下降一个数量级。可见，随着植被的恢复，水体净化效率逐步提高。鉴于建造人工湿地比利用现有水体改造湿地的费用和环境效果均大得多的现实，本文提出：恢复城市湖泊的水生植被是治理城市非点源污染的经济有效的途径。     

Economic modeling approaches for wildlife and species conservation

This paper presents modeling approaches for wildlife and species conservation with a special emphasis on large mammals in a developing country setting. In such countries there are frequently conflicts over land use and species conservation, and institutions for managing conflicts are often weak or even lacking. In addition, most of the world species and biodiversity are found in developing countries. Two main issues are discussed. First, we study a situation where the wildlife is valuable, but is considered a pest by the local people living close to the wildlife. Second, we consider models with a discrepancy between management geography and biological geography, and where the species flows between a conservation area with no harvesting and a neighboring area with harvesting and possible habitat degradation.