【作者】 张小燕；

【导师】 杨改河；

【作者基本信息】 西北农林科技大学 ， 作物栽培学与耕作学， 2003， 博士

【摘要】 通过查阅大量的环境、植被、生态、人文等方面资料文献，经过仔细研究、深入分析、严密思考、科学论证，对西北地区植被背景值及演替规律进行了较为全面系统地研究。 1．与植被有关的环境的研究 对与植被有关的西北地区的环境背景、地质背景及主要大地构造、地貌特征及主要地貌单元、气候特征、水文特征、土壤类型进行了论述。 把影响植被变化的因素归纳为地理位置、气候条件、地形地貌、土壤条件和人类活动五类。其中把人类活动对植被的影响概括成人类的农业活动、人类的开垦活动、人类的开采活动、人类的工业活动和人类的生活五个方面。指出人类的农业活动主要在水热土条件较为优越的地方，环境的自我收复功能较强；人类的开垦活动在或者是水热条件差、或者地形不平或陡峭、或者土壤难以耕作的地方，环境的收复能力差，人类的活动对自然生态系统影响深远；人类的开采活动则是在人类为了获取能源、矿产、药材、燃料等物质的任何含有所开采物的地方；人类的工业活动是在从事工业生产的所有场地；人类的生活对植被的影响主要表现在人类与植被在生存空间上对生活要素的争夺，特别是在干旱的荒漠区，对水资源的争夺尤为明显。 2．对西北地区植被类型及地理分布的研究。 通过对西北地区现有植被类型进行统计分析和归类研究，按照我国现在普遍采用的植被分类的单位，从高级类型到低级类型，把西北地区现有的自然植被分成了9个植被型组，20个植被型，37个植被亚型，86个群系组。并且以直观明了的表格形式把西北地区植被的各级类型及主要分布区域表示出来，便于查阅、比较及分析。 把西北地区的农业植被分成了3个类型，6个型，13个组合型。 3．关于西北地区自然植被与农业植被对环境的作用研究。 从覆盖面积、土壤固结作用和对环境中生活要素的损耗三方面就西北地区自然植被与农业植被对环境的作用进行了分析论述。尽管不同区域、不同植被类型地表覆盖度有很大差别，若把自然植被的覆盖度看作1，指出在同样区域内，农业植被的覆盖度在西北地区从0.20到1。不同的种植方式其作物覆盖率分别为：以春麦类为主的一熟四年轮休二年为0.22；以春麦类为主的一熟三年轮休二年为0.20；以春麦类(豌豆)为主的一熟三年轮休一年为0.25。以春麦类(马铃薯)为主的一年一熟为0.33；以春麦类(豌豆)与胡麻、燕麦秋作为主的一年一熟为0.375；以春麦类(豌豆)与荞麦为主的一年一熟为0.361；以水稻连作为主的一年一熟为0.5。以春麦类(豌豆)与荞麦为主的一年一熟为0.361；以冬麦、春玉米与谷、糜类为主的一年一熟为0.56。以冬小麦、夏杂粮为主的一年二熟为1.00；以春麦、夏杂粮为主的一年二熟为0.583。 农业植被对土壤的固结作用远远小于自然植被；农业植被对环境中生活要素的损耗大大超过自然植被，在西北地区的荒漠区域、草原区域影响更为严重。 4.对西北地区植被的区划。 在掌握西北地区现有植被类型的基础上，以植被类型组合、植物区系特征、人类栽培植被特点等为依据，把西北地区作为一个独立的单元，按照植被分区的原则、指标和单位，从高级单位到低级单位，把西北地区的自然植被分成了5个植被区域(包括n个亚区域)，13个植被地带，25个植被区，58个小区。 5.对西北地区植被背景的研究。 以植被区为单元，在了解各区地理位置、气候特征、植物区系特征的基础上，对西北地区25个植被区的58个小区的植被分布规律、植被类型结构进行了系统地较为详细地论述。 6.对西北地区植被演替的研究。 按照地质发展的纵向顺序，从古生代中的二叠纪开始，经过二叠纪期、侏罗纪时期、白至纪时期，到新生代的古新世、始新世未期到渐新世晚期，再到中新世时期、上新世至更新世时期、更新世和全新世，最后到历史时期，较为系统地整理了全国地形、气候以及植物的变迁。指出西北地区在未来十年干早的局面不可能改变。 植物的变迁有相对种类丰富、生长繁茂期，也有种类单调、生长缓慢时期。总的规律是随着大地构造的基本稳定，变幅越来越小。自人类出现以后，植被的变迁除了受地质环境变化影响外，也参杂了人类活动的影响，并且人类活动的影响一直在逐渐加大:在距今3000年以前，植被变化几乎完全受气候冷暖干湿变化的控制;进入到近2000年来的人类历史时期，人类对植被的影响作用逐渐加大，但植被的波动主要还是受千年和百年尺度的气候影响;到了19世纪下半叶的现代时期，植被覆盖既受数十年或数年尺度的气候干湿波动作用，也受人类不合理经济活动的影响，尤其是在20世纪50年代以来，在半湿润森林草原区、半干早典型草原区、干早荒漠草原区、黄土高原水土流失区等，人类经济活动影响的成份更多。 7.影响植被的人为因素变迁 把影响植被的人为因素变迁，归纳为人口数量的变迁、人口空间分布的变迁、人类所掌握的科技文明的变迁和人类需求的变迁四类。人口数量的增加，活动范围的加大，人类改造环境手段的进步和能力的加强，使得原来的自然植被，变迁成农业植被，再变迁成稀少植被更多还原

【Abstract】 widely Referring to information about environment, vegetation, ecology , human activity and so on, the vegetation backgrounds and vegetation succession in Northwest China were studied by delving, deeply analyzing, consideration and scientific reasoning.1 .Study on environment related to vegetationThe paper discussed factors which is closely related to vegetation, such ad environment backgrounds, geology backgrounds and earth tectonic, physiognomy traits and its unit, climate, hydrogeology, agrotype and so on.Factors affecting vegetation were induced to geographic position, climate, terrain and physiognomy, soil and human activities. Influences of human activities on vegetation were generalized five parts, i.e. farming, reclamation, exploitation, manufacture, and human livings. The arid also points out that human farming actions is in places of better water, quantity of heat and soil conditions, where environment rehabilitation ability is better; reclamation action is in places of bad conditions of water and quantity of heat, or rough or steep terrain, or soil difficult to cultivation, where environment rehabilitation ability is bad and humane actions have deep influences on mature ecosystem; mining action is in any places of valuable resources of energy, minerals, medicinal materials and fuel etc., which can be demanded and be acquired by people; manufacturing actions is in all places of industrial production; influences of human livings on vegetation represents contest for living essentials in living space, especially obvious in the region of arid hungriness for water resources.Vicissitude of human factors affecting vegetation concludes flux of population quantity, population distribution in space, science and technology mastered by people and human demands. Flux of population quantity includes population increase as improving of medical treatment and living conditions, and population reduction as battle and murrain. Flux of population distribution in space includes migration from backland to border land, from border land to backland, from South to North and from North to South for some reasons. Flux of science and technology mastered by people represents people wisdom development in the process of continually science exploring and technology innovating, which are applied to every walk of life, such as agriculture, industry and mining etc. Flux of human demands refers to increasingly people demands including in continually city what scale enlargement, improvement of habitation conditions and additional facilities increase, all of which makes natural vegetation previous change to agriculture vegetation, further, to sparse vegetation or to concrete construction without vegetation.2. Study on vegetation type in Northwest China.The vegetation was classified into nine vegetation-type groups, 20 vegetation-types, 37 vegetation subtypes and 86 formation groups in Northwest China, through statistic, analyse and classification for vegetation in Northwest China according to principles of vegetation classification generally adopted by botanist. All of the vegetation and their distribution were showed with tabulation, which are visual, legible and convenient.3. Study on effect of natural vegetatin and agriculture vegetation to environment in Northwest China.The article analyzes effect of natural vegetation and agriculture vegetation to environment in Northwest China from three aspects, viz cover area, soil prehension and consumption for living essentials in space . Assuming cover rate of natural vegetation is regard as 1, the study shows that cover rate of agriculture vegetation is from 0.22 to 1 in the same places according to planting modes in Northwest China. Effect of agriculture vegetation on soil prehension are distinctly less than those of natural vegetation. Consumption of living essentials of agriculture vegetation exceeds that of natural vegetation, especially more badly in hungriness and campo areas in Northwest China.Agriculture vegetation is divided 3 groups, 6 types, 13 combinati更多还原