官司河流域防护林景观结构及生态功能研究

利用2005年度的IKONOS4卫片解译数据和2007年度小班调查资料,结合样地调查资料以及四川省林业科学研究院森林生态效益定位站（四川绵阳新桥）径流场的有关数据,对绵阳官司河流域的防护林体系景观结构及生态功能进行了分析。结果表明：该区域防护林景观中,以松柏混交林（Mixed Alnus—Cupressus forest）面积最大,占27．37％,其次是马尾松纯林（Pinus massoniana forest）,占25．41％。栎柏混交林（Mixed Quercus-Cupressus forest）最少,只占0．96％。纯林面积明显大于混交林,前者比后者大45．31％。栎柏混交林、松柏栎混交林（Mixed Pinus-Cupressus—Quercus forest）最大斑块指数（LPI）、边缘密度（ED）和斑块密度（PD）较小,分布较为破碎。而马尾松纯林、松柏混交林和柏木纯林（Cupressus forest）分布较为集中。桤柏混交林（Mixed Alnus—Cupressus forest）和松柏混交林的散布与并列指数（IJI）较大,其空间关系较为复杂。栎柏混交林、柏木纯林的聚集度（A1）较小,斑块分散度大,连接睦较差;而桤柏混交林、松柏混交林的分散度较大,连接性较好。桤柏混交林、松柏混交林的形状指数（LSI）较小,形状分布较规则,而马尾松纯林、柏木纯林的形状指数较大,形状较复杂。从不同景观类型林下灌草层的生物多样性指数可知,松柏混交林、栎柏混交林的灌草多样性指数均较大,而马尾松纯林、柏木纯林则较小。从保持水土功能来看：桤柏混交林、松柏混交林的水土保持效果优于柏木纯林、马尾松纯林,桤柏混交林的水土保持效果优于松柏混交林。因此,对长江防护林进行空间结构调整,应多采用混交林模式,针阔混交林代替针针混交,乔灌草结合,调整合理的密度,使防护林景观的生态功能更好地发挥。     

长三角地区典型稻作农业小流域氮素平衡及其污染潜势

江苏省句容市陈武镇水库流域是以稻作为主的农业小流域,在长三角地区颇具典型性。于2007年5月至2008年4月在该流域进行定位观测与现场调查,通过估算氮素平衡来分析预测流域农田氮污染潜势。结果表明,研究时段内流域氮素输入量为1 589.1 t,输出量为1 168.4 t。化肥氮输入是农田氮素的最主要来源,占氮输入总量的67.2%;而作物收获是农田氮输出的主要方式,占氮输出总量的46.7%。水田和旱地氮平衡均处于盈余状态,盈亏率分别为20.5%和52.4%,氮素利用率分别为33.6%和34.9%,利用率较低。水田47.8%的氮素以气态形式损失,气态氮和储存在土壤中的氮素极易导致大气和水体污染。     

乌梁素海流域种 养系统氮素收支及其对当地环境的影响

以内蒙古乌梁素海流域为研究区,建立区域氮素流动模型,研究了2006年种-养系统中氮素的收支状况及其对区域环境的影响。研究结果表明,乌梁素海流域氮素投入主要来源于耕地系统,草地系统的投入量很少。耕地系统氮投入量大于支出量,氮素盈余4.03×104t,平均盈余85.0 kg.hm-2。草地系统氮投入量小于支出量,导致草地系统氮收支亏损,亏损额为593 t,平均亏损0.99 kg.hm-2。大量氮亏损是引起当地草场退化的主要原因。此外,该流域每年随地表径流进入地表水的氮总量达9.25×103t,给当地水环境带来了巨大压力。肥料施用是地表水最主要的氮素来源,因此,控制农业面源污染应是当地水环境控制和管理的重点。     

丘陵地区流域土地利用对氮素径流输出的影响

氮素是地表水体富营养化的一个限制因子,土地利用对农业非点源污染的氮素输出具有重要的影响.以位于亚热带低山丘陵地区的安徽省南部宣城市梅村流域为实例,通过航空遥感图像解译、GIS分析和实地定位动态监测方法,研究了具有不同土地利用结构的农-林生态系统地表径流水的氮素含量和输出通量及其与土地利用的定量关系.结果表明:氮素的输出以NO₃^--N的输出为主,土地利用类型或土地利用格局对径流水中氮素的含量和输出具有非常显著的影响.在同一种土地利用结构系统下,NO₃^--N与T-N的含量间具有极显著的正线性关系;而只有林地-水塘系统下,NH₄⁺-N与T-N的含量间有极显著线性关系.而各类氮素的输出量间都具有极显著正的线性相关关系.各类氮素的输出量都与土地利用类型具有指数相关性,林地、水塘对氮素输出具有负效应,而水田和村庄则具有正效应.同时,土地利用类型对径流中氮素的含量也有影响.     

苏、浙、皖、闽、湘、鄂、赣7省酸沉降农业危害——农业损失估算

为估算苏、浙、皖、闽、湘、鄂、赣7省由酸沉降造成的农业经济损失,利用野外开顶式熏气装置对水稻、小麦、大麦、棉花、大豆、油菜、番茄、胡萝卜和菜豆9种作物进行模拟酸雨与SO₂的单独处理和复合处理。建立酸雨pH值和SO₂浓度对农作物产量的单一影响模型和复合影响模型,从而推算出自然条件下7省农作物受酸沉降危害的减产量,利用市场价格法估算并分析酸沉降造成的７省农业经济损失。分析表明,酸沉降已对7省的农业生产造成了一定程度的危害,7省主要农作物受酸沉降影响播种面积达991.83万hm²,减产562.41万t,经济损失约合36.99亿元。     

上海浦东新区农业发展环境规划研究

基于在发展农业的同时有效地控制农业环境污染的目的,综合环境、经济和社会等方面的因素,建立了浦东新区农业结构优化调整的灰色线性规划模型。该模型将农业结构调整与经济预测、化肥与农药的流失控制以及畜禽粪便污染联系起来,动态地分析规划年份的浦东新区农业生产结构,确定了农业内部结构调整的方针。     

农业可持续发展状态评价指标(体系)框架及其分析

通过对农业活动、农业政策与农业环境变化关系的研究,提出了反映农业可持续发展状态的指标结构以及面向农业决策的状态指标分析框架,建议采用“离差法”来评价农业系统的可持续发展状态,其评价结果可以用来判断和制定正确的农业政策;同时还论述了状态评价的具体方法、步骤及评价标准     

THE WESTERN WATER COMMISSION: WATERSHED MANAGEMENT RECEIVES THE AVI'ENTION OF A NEW GENERATION1

ABSTRACT: Our nation periodically reviews national water policy and considers its directions for the future. The most recent examination was directed at the western United States and the role of the federal agencies in meeting its needs. The West is no longer the frontier, but rather contains vibrant cities and booming centers of international trade, as well as tourism, mineral, and oil and gas development, agricultural, and other development. In this changing environment, federal water policies need to consider the long term sustainability of the West, provide justice to Indian tribes, protect the rivers and ecosystems on which natural systems depend, balance the needs of newcomers with those of agricultural users and communities, and meet a myriad of other demands. The Western Water Policy Review Advisory Commission has just concluded its review of these issues and issued its report. Key among the recommendations is the need to coordinate federal agencies at the basin and watershed level and make government more responsive to local needs, but within a framework that includes national mandates. The Commission's recommendations are presented here, along with some of the issues that surrounded the operations of the Commission.     

LANDCARE AND COMMUNITY-LED WATERSHED MANAGEMENT IN VICTORIA,AUSTRALIA1

ABSTRACT: Australia's ‘Landcare’ program is a community-based participatory program established by government to tackle the problem of land degradation. Landcare involves thousands of Australians working together in locally based groups, tackling problems of common concern. Government and community are now looking to ‘scale up’ the Landcare idea to a regional level. State and territory governments have moved to create regional (often watershed-based) frameworks for land management planning and resource conservation, in accordance with the concept of integrated watershed management. Growing out of the success of community involvement in Landcare, many of these approaches involve the community. However scaling up of the Landcare idea introduces problems of both time and space. There have been a number of problems experienced in the implementation of Landcare and integrated watershed management. These problems include the equitable delineation of membership on decision-making bodies; the raising of sufficient funds for program implementation; and the coordination of a diversity of governmental layers, planning processes and management programs. This paper reviews how the State of Victoria has responded to these challenges and suggests what challenges remain.     

WATERSHED AND LAKE WATER QUALITY ASSESSMENT: AN INTEGRATED MODELING APPROACH1

Watershed planning groups and action agencies seek to understand how lake water quality responds to changes in watershed management. This study developed and demonstrated the applicability of an integrated modeling approach for providing this information. An integrated model linking watershed conditions to water-quality of the receiving lake incorporated the following components: (1) an event-based AGNPS model to estimate watershed pollutant losses; (2) annualization of AGNPS results to produce annual lake pollutant loadings; (3) a base flow separation package, SAM, to estimate base flow; (4) estimates of nutrients in base flow and point sources; and (5) linkage of watershed loadings directly to EUTROMOD lake water quality algorithms. Results are presented for Melvern Lake, a 28-km² multipurpose reservoir with a 900-km² agricultural watershed in east central Kansas. Reasonable estimates of current lake quality were attained using an average phosphorus availability factor of 31 percent to calibrate model results to measured in-lake phosphorus. Comparison of a range of possible scenarios, including all cropland changed to no-till (best case) and all CRP and good-condition grasslands changed to cropland (worst case), indicated only a (4 percent change for in-lake phosphorus and a (2 percent change for chlorophyll a. These results indicated that this watershed is not sensitive to projected changes in land use and management.