【作者】 王晗生；

【导师】 贾志宽； 黄占斌；

【作者基本信息】 西北农林科技大学 ， 作物栽培学与耕作学， 2002， 博士

【摘要】 生态环境建设是实现社会和经济可持续发展的重大问题。黄土高原以严重的水土流失闻名于世，水土保持工作长期以来受到人们的高度关注，然而，迄今，从整体上说，黄土高原生态环境建设并未达到预期的效果，其中防蚀植被作为重要建设内容，依然是最为薄弱的环节。在我国实施西部大开发战略的新的历史时期，为取得植被建设实质性的成效，不能不使人们对黄土高原长期造林种草的实践进行反思和总结。 本文从广义植被(包括农作物)的角度出发，通过广泛搜集资料以及野外考察，采取分析与综合、归纳与演绎相结合的方法，对该地区植被建造中存在的根本性关键问题，如植被建造依据及技术与模式、植被作用下的土壤干化、景观生态建设等进行了探讨。 首先，讨论了植被结构与其防止土壤侵蚀作用的关系，结果表明，植被盖度或郁闭度的大小并不一定就是防蚀有效植被的充分条件，植被保持水土功能还与覆盖层的高度密切相关，覆盖层高度大并不有利于植被保持水土。贴地面覆盖层的发育程度(盖度或厚度)是防蚀有效植被的充分必要条件，贴地面覆盖因而也是其更为一般的基本本质特征。植被保持水土重要的是应具有贴地面的覆盖层，促进贴地面覆盖层的发育或关注贴地面覆盖层的变化是植被保持水土的关键。 在上述结论的基础上，本文通过指出现有防蚀植被定义的缺陷，论述了其涵义，认为防蚀植被应当是在侵蚀地区，以防止土壤侵蚀或以固沙为目的，植物充分占据地面空间，一般具紧密结构，或者显著具有有机体(枯落物以及生物量)贴地面覆盖特征的植被。进一步的分析表明防蚀植被就是发育良好的自然植被或者接近自然的人工植被，与纯粹追求经济目标的人工植被相比，不仅在结构上，而且在演替、经营等方面是不同的。据此，通过对荒坡问题的讨论，认为应当将灌苹坡，尤其草坡与真正的荒坡区别开来而对待。 为因地制宜地建造植被，本文还分析了黄土高原植被屈性的有关观点，以及生物气候条件在不同地域之间的分异性和植被地带性特征，说明黄土高原可表征为森林、草原等地带，不能认为黄土高原不具有森林发育的地带性环境。相对于森林地带北界森林线，森林草原地带北界应为树木线。植被建造不应局限于一种土地利用模式，如朱显谟“28字方略”，不能无视疏林及稀疏灌丛在森林草原地带的客观存在。 在阐述植被建造依据之后，本文讨论了植被建造的技术与模式，表明典型水土保持植物是建造水土保持植被的首选植物。在分析人工林经营存在问题的基础上，将水土保持林划分为公益性和公益及商品兼顾林两类，并论述了其成林过程、途径等方面的性质，表明人工水土保持林接近自然的属性是保证其质量的重要特征；使得林木在一个世代内保持其稳定性而不早衰，或者演替为地带性顶极植被而产生的稳定性，则奠定了其功能持续的基础：较短时期内形成良好的贴地面覆盖是其快速有效性的前提。鉴于造林的一般立地特征，黄十高原除建造森林植被外，更应高度重视草灌的水土保持作用。在一定情况下，可不必全面造林种草，如植被带状种植形式，可以较少的占地面积，就能达到良好的水工保持目的。植被带状种植在逐步退耕还林还草中也有着特殊的意义。一般地，水土保持林内可以间种牧草．但粮、药、菜等间作形式欠妥。商品林虽然通常也被称其为“林”，但它绝非一般意义上的森林，可以说，两品林属于作物栽培范畴也有一定的根据。“杂草”概念及其控制具有相对性。 本文接着又讨论了植被土壤水分状况及其与经营的关系，表明在气候干旱少雨，蒸发又强烈的条件下，黄土高原由于地下水埋藏深，土壤于化是植被作用下易于发生的现象，是人为营造大片耗水性强的植被类型，高密度以及追求高生本量的必然结果。这种植物生长用水与环境供水之间的矛盾表现，对人工林草植被的稳定性构成亚重威胁，并对植被衰败后的深根性植物的生长发育起到显著的抑制作用。显然，植被作用下的土壤干化，对追求经济目标来说是不利的，但对于防止土壤侵蚀并不一定就产生负面影响。植被作用下土壤干化的显现，表明森林涵养水源的功能址以实现，水源涵养林是水土保持林，但水土呆待林不一定就是水源涵养林。人为可以将植被作用下的上壤干化现象加以调节和控制，如局部带状或团块状种植、疏伐、轮作、休闲等。何况，土壤干化并不是黄土高原植被建造的必然结果。因此，不能以此为由或者根据植被减少流域年总径流量的结果，怀疑甚至否定黄土高原林草植波的建造。植被作用下的土壤干化现象说明，在贯彻适地适种原则的基础上，还需选择耗水量少的抗旱节水植物和可维持土壤水库水平的密度或盖度，这是保证植被稳定持久值得重视的又一重翌方面。从有利于流域水资源状况的改善，在满足水土保持目标的前提下，人工林草植被的发展也应该适度规模。公益性植被建造不能根据作物栽培的水分利用原则，极尽将降雨转化为生物产量。 最后，本文由景观生态学的观点理解生态环境建设，分析了“山川秀美”的涵义，讨论了黄士高原生态环境建设的目标、重点、原则、途径等。基本农田建设在一定程度上关系到生态环境更多还原

【Abstract】 Eco-environmental construction is a major problem concerning realizing sustainable development of society and economy. Because the Loess Plateau is well-known for serious soil erosion, soil and water conservation has been valued highly for a long time, but so far its eco-environmental construction don’t achieve the desired results as a whole, in which anti-erosive vegetation regarded as great substance is still the weakest link. In the new historical stage when the strategy for developing west China is being implemented, in order to get material results in vegetation construction, long-term pratices of construction of forest and grass vegetation in the Loess Plateau have to be examined.From the point of view of generalized vegetation including crops, through widely collecting data and field investigations the paper takes combination of analysis with synthesis or induction with deduction to deal with basic key problems existing in vegetation construction in this region, such as bases, techniques and patterns of vegetation construction, soil desiccation by vegetation, landscape ecological construction.At first, the relations between vegetation structures and their controlling soil erosion are discussed. The results show that magnitude of plant community coverage or canopy closure isn’t certainly the adequate condition of an anti-erosive effective community because the community function of soil and water conservation is related to height of coverage layer as well as community coverage or canopy closure. High coverage layer is unfavorable to soil and water conservation by vegetation. Developing degree (coverage or thickness) of coverage layer close to ground is the adequate and necessary condition of anti-erosive effective communities, so coverage close to ground is also the ultimate essential characteristic more common for them. It is important to form coverage close to ground for soil and water conservation by vegetation, and it is a key to soil and water conservation by vegetation to promote development of coverage layer close to ground or pay close attention to changes of it.Based on the above conclusions about anti-erosive vegetation structure, the paper expounds the implication of anti-erosive vegetation by pointing out the fault of its current definitions, and it is considered that anti-erosive vegetation should aim at protecting soil from erosion and fixing active sands in the eroded areas, ground space fully occupied by plants, in general with close structure, especially with outstanding coverage close to ground by organic matter (litter and/or biomass). The further analyses indicate that anti-erosive vegetation should be natural well developed or near natural, and it would be different not only in structure, but also in succession, management, etc., from artificialvegetation taking economical value as only a target. According to this, through discussing the problem about waste slopes it is thought that shrub and/or grass slopes should be distinguished from real waste slopes.In order to construct vegetation in line with local conditions, in addition the paper analyzes the viewpoints relevant to vegetation properties of the Loess Plateau along with regional differentiation of bio-climatic conditions and vegetation zonality. It is shown that the Loess Plateau might be regionalized into different vegetation zones of forest and steppe. It couldn’t be believed that zonal environment don’t be possessed in the Loess Plateau. So far as the north demarcation line of the forest zone is called the forest line, the north demarcation line of the forest-steppe zone should be called the tree line. Vegetation construction shouldn’t be confined to such a land use pattern as "the 28-word general plan" put forward by Zhu Xianmo. The objective reality of thin woods and sparse shrubberies in the forest-steppe zone cannot be ignored.After expounding the bases of vegetation construction, the paper discusses the techniques and patterns of vegetation construction. It is shown that typical plants for soil and wate更多还原