常绿阔叶林恢复过程植物物种多样性的变化

Evergreen broad-leaved forest is one of the most important vegetation types in China. Because of the human activities, evergreen broad-leaved forest has been destroyed extensively, leading to degraded ecosystem. It is urgent to conserve and restore these natural forests in China.tn this paper, the tendency and rate of species diversity restoration of the evergreen broad-lea ved forest in Darning Mountain has been studied. The main results are as follows:(a) in subtropical mid-mountain area, species diversity in degraded evergreen broad-leaved forest can be restored. Through analyzing b diversity index of communities in different time and space, it was found that the species composition of communities tend to be the same as that in the zonal evergreen broad-leaved forest. (b) The restoration rate of evergreen broad-leaved forest was very fast. Planting Chinese fir after clear-cutting and controlled burning of the forest 178 species appeared in a 60Om^2, sample area after 20 years““ natural recovering. Among these species, 58 were tree layer and the height of community reached 18m, The survey suggested that it would take only 20 years for the degraded forest to develop into community composed of light demanding broad-leaved pioneer trees and rain-tolerance broad-leaved trees, and it need another 40-80 years to reach the stage consisting of min-tulerance evergreen broad-leaved trees, (c) Species number increased quickly at the early stage (2-20 years) during vegetation recovering process toward the climax, and decreased at the min-stage (50-60 years ), then maintained a relatively stable level at the late-stage (over 150 years).     

国内外城市生态空间土壤种子库研究 进展

城市生态空间是城市空间的重要组成部分,能为城 市提供生态服务。在当前生态文明和绿色发展理念下,城市 生态修复相关研究逐渐增多,其中能为城市生态空间植被恢 复提供潜在种子来源,且低成本、可持续、生态效益高的土 壤种子库技术也日益受到关注。以城市绿地、城市湿地、城 市废弃地等主要城市生态空间为对象,论述了城市生态空间 土壤种子库研究进展,重点综述了城市生态空间土壤种子库 特征、影响因素和实践探索,梳理了城市生态空间土壤种子 库技术体系,包括修复模式、技术路线及评价体系。在此基 础上,提出了今后利用土壤种子库技术进行城市生态空间植 被恢复应加强基础科学研究、合适的工艺与方法开发、生态 修复和景观化融合等方面,以期为城市生态空间土壤种子库 研究与应用提供参考与借鉴。     

Land use intensification potential in slash-and-burn farming through improvements in technical efficiency

Much attention is being paid to find alternative land use options in slash-and-burn (SaB) farming (or forest–fallow-based shifting cultivation) systems. The conservation objective is often twofold; that is, to discourage farmers from expanding into the forest frontier and to reduce the ecological damage from burning plots. Options include the total abandonment of forest plots, the adoption of productivity increasing green revolution-type technologies, and the application of modern ‘evergreen’ agroforestry knowledge. This paper evaluates another alternative: the intensification of land use by improving technical efficiency in farming. This involves the reduction of land clearing while at the same time maintaining crop output levels and the local (and traditional) low-input technology. The potential for such land use intensification is empirically assessed with ecological and socioeconomic household data from Yucatan (Mexico). The methodology is based on both parametric and nonparametric output and input distance functions. In addition, the sources of inefficiency are addressed. The results of the analysis suggest that on-and off-farm labour diversification can play a key role to help shifting cultivating households to improve their technical efficiency in farming and thus to help to intensify land use. Furthermore, while the empirical results point towards the positive effect of soil fertility, mainly determined by the length of forest fallows, on crop output levels, farmers appear to overcome the ecological constraint of farming in less fertile soils by being more technically efficient.     

基于土壤重金属生态修复的社区花园 植物景观设计

生活环境需求的提高要求景观绿地不仅要加强观 赏性和体验性,同时要满足生态可持续的目标。城市更新下 社区花园呈现迅速发展趋势,然而其景观设计与生态修复的 研究缺乏理论基础。基于此,以土壤重金属污染为切入点, 结合社区花园的景观特点和功能需求进行植物生态景观营造 研究,提炼出基于土壤重金属生态修复的社区花园植物景观 营造目标与原则。从社区花园的空间分区设计、植物群落层 次、植物组团配置及重金属污染分级修复进行植物景观设计 的探索,提出基于土壤重金属修复下的植物生态景观设计策 略。以期为社区花园的长远发展和土壤重金属污染修复的景 观营造提供借鉴。     

云南生态环境评价

在西部大开发中，云南省已全面启动生态环境建设工程，对云南生态环境现状作出科学评价尤显急迫而重要。我们以1999年为基期，县级行政区划为评价单元，按主导因子，区域差异，统筹兼顾和可操作性为指标选择原则，以云南生态环境面临的主要问题、自然生态环境的主导体和技术上的可行性为指标选择依据，选择森林覆盖率、土均水资源量、坡旱地比重、未利用地的比重、土壤侵蚀率、人口密度6个指标，用模糊数学的方法对云南生态环境现状进行评价，得出124个县的评价等级。其中生态环境质量优的26个县，良的35个县，中的34个县，差的23个县，劣的6个县。     

顶坛花椒产业的生态经济模式分析

顶坛花椒是具有地域特色的优良花椒品种,适生于喀斯特干热河谷,具有喜钙、耐旱、周年萌梢、有效成分含量高等特点,是北盘江狭谷典型石漠化山地进行生态治理的主要经济树种。通过营建以花椒为主的经济林,使当地的土壤侵蚀模数减少47%～54%,森林覆盖率提高4%～7%,林地贮水量比农地增加3.19%～7.36%,水土流失防治率达94%,土地石漠化治理率达92%,生态环境得到持续改善。这种选择原生植物资源进行开发利用,并发展成优势产业以治理生态的生态经济模式值得借鉴和推广。     

北京园林绿地6种树木的叶片和一年生枝中5种重金属含量比较

为了解不同园林树木对重金属的吸收情况,以北京市陶然亭公园、紫竹院公园、中科院植物园、马甸公园、皇城根遗址公园和营城建都滨水绿道不同环境绿地为样地,选择样地间共有的园林树木,采用ICP光谱仪测定了6种树木叶片和一年生枝条中重金属锌(Zn)、铬(Cr)、镍(Ni)、砷(As)和汞(Hg)的含量,以此为基础,采用隶属函数法将6种树木单位重量对5种重金属的综合富集能力进行排序,并对同树种叶片与当年生枝、5种重金属吸收量分别进行相关分析。结果表明：1)不同树种叶片和一年生生枝条单位重量中重金属含量有显著差异,且因重金属种类而异。Zn、As含量最高的为金银木,Cr、Ni、Hg含量最高的依次为圆柏、侧柏、丁香;丁香富集Zn、Cr、As的能力最低,白皮松富集Ni能力最低,侧柏富集Hg能力最低。2)树木叶片和当年生枝单位重量对5种重金属综合富集能力排序为：金银木＞侧柏＞圆柏＞油松＞丁香＞白皮松。其中,针叶树种中圆柏、侧柏、油松富集5种重金属的综合能力显著高于白皮松(P＜0.01),阔叶树种中金银木吸收重金属的能力显著高于丁香(P＜0.01)。3)树木不同器官中重金属含量也不同,不同树种间叶片与枝条中仅Cr含量具有显著相关性,相关系数为0.461(P＜0.01),其他4种元素均未达到显著水平。4)同树种叶片和当年生枝Cr和Ni吸收呈极显著相关性(P＜0.01),其他元素吸收之间未呈现相关性。本研究结果对北     

覆土厚度对城市园林植物生长的影响 分析

城市绿地地下空间开发对解决城市建设与绿化用地之 间的矛盾至关重要,覆土厚度作为其重要参数指标,对园林植物 生长和工程建设成本具有重要的影响。通过不同覆土厚度(0.5、 1.0、1.5m)处理与地面对照下北京城市5种常见园林植物地上部 及其根系生长的多年监测与分析发现以下几方面。1)与地面对照 相比,0.5m覆土处理与1.0m覆土处理明显限制了速生树种洋白 蜡的地上部生长;但各覆土处理未明显限制生长速率较慢的油松 和紫薇的生长;而0.5m覆土处理明显限制了灌木类(大叶黄杨与 金银木)的地上部生长。2)植物生长5年后,所有覆土处理中的植 物根系均已到达种植池底部,且0.5m覆土处理的粗根分布密度 明显高过其他处理,表现出一定程度的根系相互压迫与横向生长 现象。乔木根系生长随着覆土年限的推移将会受到不利影响。     

山西生态经济问题初探：森林与人口,土地

山西省由于森林覆盖率极小，各种自然灾害频繁发生，致使耕地减少，质量下降，农业生产力降低；人口的激增，致使人均耕地面积大幅度减小，粮食紧缺，形成：人口增加－粮食不足－土地拓垦－森林消失－水土流失－经济贫困的恶性循环，从而进一步制约了社会经济的发展。为改变这一状况，笔者提出了若干对策指施。     

Policies for the management of weeds in natural ecosystems: the case of scotch broom (Cytisus scoparius,L.) in an Australian national park

Environmental weeds are plants that invade natural ecosystems and present a serious threat to conservation of nature. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis in weed control in Australian national parks has been placed on chemicals, manual pulling of small plants, excluding tourists and feral animal control measures. Recently, biological control has been introduced to control weed infestations. These methods typically have been applied as funds have become available, with little opportunity to consider their long-term effectiveness. As the threat from environmental weeds is becoming more fully recognised, an integrated, strategic, ecological and economic approach to weed management is needed. A deterministic dynamic programming model is developed for this purpose in this paper. A case study for scotch broom is presented, to assess the ways in which this approach can address the policy issues that face the community in the management of an environmental weed in a national park. The model takes account of the weed population dynamics, the effectiveness and cost of control measures, and the value of the park outputs (biodiversity, recreation and grazing). The dynamic programming model includes weed density and seed bank as state variables and a budget constraint for the control variables. The model is used to derive optimal control rules for any given state of the weed population. An optimal decision rule provides a package of control measures that can be used to attack the problem each year, depending on the current weed density and seed bank. Optimal trajectories are developed for a planning horizon of 45 years, and the effect of the budget constraint is analysed. The marginal value of an extra dollar for weed control, in terms of discounted future benefits, is estimated. It is shown that a combination of controls that targets both weed density and the seed bank is important. It is also shown (given the assumed parameters) that biological control is worth undertaking, as it appears as part of most of the optimal strategies identified. The paper concludes with policy recommendations for managing weeds in natural ecosystems.