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作 者 ：秦树高,吴斌,张宇清*

期 刊 ：生态学报 2010年 30卷 13期 页码：3616~3627

关键词：复合农林系统；林草复合系统；种间互作关系；竞争；共栖；小气候效应；生理生态反应；

Keywords:agroforestry system, silvopasture system, interspecific interaction, competition, commensalism, microclimate effect, eco-physiological response,

摘 要 ：林草复合系统因其具有产品多样性、生产高效性、环境友好性等特点，在世界范围内得到普遍应用，同时也是我国西部地区生态环境建设中的重要类型之一。在林草复合系统中，种间互作关系能够直接影响到系统经营的成功与否，因此一直以来都是本领域研究的热点内容。地上部分种间互作关系指发生或表现在地表以上的物种之间直接或间接的相互作用关系，在林草复合系统中主要表现为：系统对林地小气候的影响，林木与牧草在生长和生产过程中的相互作用，系统对生物多样性的影响以及林木的存在和生长与放牧活动之间的相互作用。在林草复合系统中，林分通过对诸多气象要素的调节，为牧草和牲畜的生长发育提供了良好的气象条件；同时牧草通过增加空气湿度、减小土壤和空气温度的变化幅度，可对林木（特别是幼树）起到一定保护作用。牧草能够发生一系列生理生态反应（增加叶面积指数和叶绿素含量、提高光利用效率等），以适应林分对小气候的改变，而其产量和质量会受到系统物种组成、配置模式和林木遮荫的共同影响。林木遮荫通常会降低牧草产量，但会使牧草品质得到一定改善。而热带稀疏草原上孤立树的遮荫和草牧场防护林的庇护，均可有效提高和改善牧草的产量和品质。将低竞争性的牧草（尤其是豆科牧草）引入森林或果园之中，林产品的产量和品质、林木生长特性能够得到相应的提高和改善；但在困难立地条件下进行这样的尝试，由于林草之间存在着激烈的竞争，往往会产生相反的结果。林草复合系统具有多样的物种组成和复杂的系统结构，可为害虫天敌提供丰富的食物和良好生境，有助于实现森林和果园的生态化经营。在有牲畜参与的林草复合系统中，尽管牲畜对林下植被的采食，可增加林木对土壤资源的占有率，而林分对小气候的改善，可有效改善牲畜生产特性和福利状况，但牲畜活动也会对林木造成一些机械伤害，因此有必要对林木进行一定的保护。通过对上述研究的分析总结，可为林草复合系统的设计、建设和经营管理提供一定的经验借鉴，以优化系统结构和资源利用格局，减小物种之间的负面影响，最终实现系统综合收益最大化。未来应加强生理学在林草复合系统种间互作研究中的应用，揭示种间互作结果的生理学原因；构建和完善林草对太阳辐射利用关系的长期动态模型；探索系统增加生物多样性的机理；研究牲畜造成的机械损伤对林木生长的影响及相应防护技术，以及开展林草复合系统地上部分种间互作关系对全球气候变化响应的研究等。

Abstract:As a major category of agroforestry, silvopasture systems, because of its diversity of products, great efficiency and environmental improvement, has been one of the most important practice for ecosystem rehabilitation in northwestern China. Because the outputs of the systems are affected immensely by designed components, interspecific interactions have been the focus of research in silvopasture systems. Above-ground interactions mean direct or indirect non-underground interactions between different species in a community, including microclimatic modification and biodiversity increase, effects among plant species, relationship between woody plants and livestock, etc. This review summarises current knowledge on above-ground interactions in silvopasture systems, discussing cases from research reports and drawing on experiences from practices in the world. In silvopasture systems, by decreasing solar radiation and heat dissipation, reducing evapotranspiration and air flow, and raising air humidity and snow cover, trees provide favorable microclimatic conditions for herbage and livestock; And in turn, herbage provide protection to trees, especially to seedlings, by increasing air humidity, reducing air and soil temperature variation. Herbage make some eco-physiological responses to the presence of trees, e.g. enhancing leaf area index and chlorophyll content, improving light use efficiency, reducing tillering and tillers′ relative growth, and delaying maturity. The yield and quality of forage depend on many factors, such as species, space arrangement and shade. Generally, solar radiation interception of woody plants may decrease forage yield, but improve quality of forage simultaneously. Both yield and quality of grass can be enhanced under the canopies of isolated trees in tropical savanna and near windbreaks on rangelands, because of favorable microclimate, and availability of soil water and nutrient. The yield and quality of forest products, and growth performance of trees are improved, by introducing lower competition forage, especially legume, into forests and orchards; However, due to severely competition for soil resource between woody plants and grass, opposite consequence usually occur in silvopasture systems on infertile sites. Silvopasture systems, with more species and components, provide abundant food, favorable habitat for predators, improving biodiversity and stability of silvopasture systems, that may contribute to eco-environmentally-friendly management of forests and orchards. In silvopasture systems involving livestock, while grazing of livestock can reduce competition from grass, animals′ gnawing and trampling also hurt the trees combined. Consequently, it is necessary that some equipments for trees defensing the mechanical damage of livestock, such as tree shelters and electric fences. The performance and welfare of livestock may be enhanced because of favorable conditions provided by trees. The knowledge aforementioned can provide some suggestions for component design, system optimizing, sustainable land use, alleviation of adverse interations and maximal outputs of silvopasture systems in China. The paper also suggests that more researches should be carried out further in physiological mechanisms of interspecific interactions, long-term and dynamic models of light utility between woody plants and herbage, biodiversity protection mechanism, some protective approaches for mechanical damage of animals, and the system responses to global climate change.

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