【作者】 杨柳；

【导师】 阎建忠；

【作者基本信息】 西南大学 ， 土地资源管理， 2019， 硕士

【摘要】 青藏高原被誉为地球“第三极”、亚洲水塔,是受气候变化最严重的地区之一,特殊的地理位置及地形特征使其成为全球气候变化研究的热点区域。自1980年代后期以来,青藏高原持续变暖趋势明显,且增温幅度高于我国其他地区,气候条件由暖干型向暖湿型突变,极端高温事件增加,极端低温事件降低。以变暖为主的气候变化使当地热量资源得以改善,从而使青藏高原适宜耕种的土地面积增加。基于遥感数据和种植适宜性模型的一些研究表明,该地区足够的农业热量资源增加了适宜耕种土地的面积,为农牧民的开垦行为创造了有利的条件。同时,在日益增长的人口压力影响下,青藏高原农牧交错区的农牧民不得不开垦以满足对饲草的需求。气候变暖导致灌木丛入侵高山草甸,影响了牧草的生长。且在放牧规模不断扩大、国家禁牧、休牧、轮牧政策的影响下,致使牧草供给十分短缺。进而导致农牧民所承受的人口压力不断加大。而人口压力也一直被认为是农地开垦的原因之一。然而,农牧民也有极大的可能性不选择开垦,主要的原因在于:第一,我国是气候变化受益国之一(主要表现在适宜耕种面积的增加),其他受益国家的农牧民更多地采取耕地集约化策略,增加对农业的长期投入;第二,随着城市化进程的加快,青藏高原同时面临劳动力析出和劳动力价格的上涨,农牧民作为一个理性的经济人,追求利益最大化,他们会更愿意追求生计多样化以获得更高的收入,从而导致耕地撂荒现象明显;第三,青藏高原的耕地大多处于饱和状态,无地可垦;第四,开垦耕地需要较高的费用(如追加灌溉、平整土地等投资),农牧民的行为是风险规避型,为降低风险,他们往往选择集约化利用耕地,而不是开垦。在气候背景下,虽然从理论和遥感解译的角度来看,青藏高原耕地利用方式呈扩大化趋势,农户可能采取策略是耕地扩大化,但仍有采取集约化策略的可能。加之,城镇化进程的加快,青藏高原农牧民越来越接受非农工作。那么,农牧民又是如何平衡气候变化带来的开垦机遇、风险,劳动力析出以及人口压力的,仍然缺少认识。因此,有必要在气候变化和劳动力析出背景下研究农牧民的耕地利用决策,并分析影响农牧民耕地利用决策的因素,为增强该地区农户抵御气候变化带来的风险以及制定气候变化下耕地利用的有效适应策略和农牧业发展计划提供理论基础。青藏高原是生态脆弱区,是我国重要的生态安全屏障、战略资源储备基地,是中华民族特色文化的重要保护地。该地区农牧民所采取的耕地利用方式不容忽视,如农牧交错带草地的垦殖也会导致草地退化和沙漠化,并且不可逆转。鉴于此,本文以青藏高原的“一江两河”地区、朋曲河流域、河湟谷地以及川西地区的壤塘县为研究区,利用四个区域947份农牧民家庭调查问卷,通过统计分析了气候变化和劳动力析出背景下农牧民的耕地利用决策,并定量研究农牧民耕地利用决策的影响因素。研究结果表明,气候变化和劳动力析出背景下,农牧民多采取耕地集约化策略,且以长期投资为主,较少的农牧会采取开垦策略。最后,根据研究结果,提出相关政策建议。具体地,研究结果如下:(1)除了降水情况的感知,研究区样本农牧民感知情况与气象站数据基本相符。绝大多数农牧民感知气候条件仍是“暖干型”气候,且感知暴风雪减少、干旱增多。此外,大部分的农牧民认为气候变化并没有对农业产生巨大的影响。(2)在气候变化背景下,随着城镇化不断地加快,农牧民对非农工作的认可度越来越高,加之政府的管制,使得开垦现象并不普遍。仅有18.16%的农牧民有开垦行为,且开垦耕地面积大多在0.02—0.20 hm~2之间。通过对调查数据的分析,证实了农牧民开垦是气候变化和人口压力共同作用的结果。计量结果还表明,农牧民开垦决策与人均打工年收入呈显著负相关关系。(3)研究区机械化水平相对较高,高达70%以上。农牧民主要购置农用拖拉机和机械用犁这两类设备,而对微耕机和水泵的投入较少,且农牧民大多在2000年以后购置农用设备。同时,农牧民的非农活动收入促进了当地的耕地机械化。此外,计量结果还表明,农牧民机械化投资与农牧民感知春季霜冻的整体变化趋势和牲畜数量呈显著正相关关系。(4)研究区耕地灌溉水平相对较高,且以沟灌为主。灌溉地块面积较小,在0.02—0.30hm~2之间。大部分灌溉设施是由政府出资修建,而农牧民自主灌溉投资相对较低。促进农牧民自主灌溉投资的因素是农牧民感知春季霜冻的整体变化趋势和耕作地块平均面积,而人均打工月收入高则抑制了农牧民灌溉投资。(5)大多数农牧民的自主化肥投入基本上没有发生变化,仅有28.83%的农牧民化肥投入有所增加。计量结果表明,农牧民的增加化肥投入决策与农牧民感知冬季持续时间的整体变化趋势、感知降水的整体变化趋势、抚养比呈显著负相关关系;与农牧民感知春季霜冻的整体变化趋势、牲畜数量、居住地距集镇距离、耕作地块平均面积呈显著正相关关系。更多还原

【Abstract】 The Tibetan Plateau,known as the "third pole" of the earth and the water tower of Asia,is one of the areas most affected by climate change.Its special geographical location and topographic characteristics make it a hot spot in the study of global climate change.Since the late 1980 s,the warming trend of the Tibetan Plateau has been obvious,and the range of warming is higher than that of other regions in China.Climate conditions change from warm-dry to warm-wet,extreme high temperature events increase and extreme low temperature events decrease.Climate change,mainly warming,has improved local heat resources,thus increasing the area of land suitable for cultivation on the Tibetan Plateau.Some studies based on remote sensing data and planting suitability models have shown that sufficient agricultural heat resources in this area increase the area of suitable cultivated land and create favorable conditions for farmers and herdsmen to reclaim.At the same time,under the influence of increasing population pressure,farmers and herdsmen in the agro-pastoral ecotone of the Tibetan Plateau have to reclaim to meet the demand for forage.Climate warming causes shrubs to invade alpine meadows,affecting the growth of pasture.Besides,under the influence of the continuous expansion of grazing scale,the state’s policy of forbidding grazing,resting grazing and rotating grazing,the supply of pasture is very short.This leads to the increasing population pressure on farmers and herdsmen.Population pressure has also been considered as one of the reasons for farmland reclamation.However,farmers and herdsmen also have great possibilities not to choose reclamation.The main reasons are as follows: first,China is one of the beneficiaries of climate change(mainly reflected in the increase of suitable cultivation area).Farmers and herdsmen in other beneficiary countries are more likely to adopt intensive cultivated land strategies to increase long-term investment in agriculture;second,with the acceleration of urbanization,the Tibetan Plateau is confronted with both labor migration and rising labor price.As a rational economic man,farmers and herdsmen are more willing to pursue diversification of livelihoods in order to obtain higher income,resulting in the phenomenon of land abandonment obvious;third,most of the arable land in the Tibetan Plateau is saturated and no more land can be reclaimed;fourth,land reclamation requires higher costs(such as additional irrigation).In order to reduce the risk,farmers and herdsmen often choose intensive use of cultivated land instead of reclamation.Under the climate background,the use of cultivated land in the Tibetan Plateau is expanding from the perspective of theory and remote sensing interpretation.Farmers may adopt the strategy of expanding cultivated land,but there is still the possibility of adopting intensive strategy.In addition,with the acceleration of urbanization,farmers and herdsmen in the Tibetan Plateau are increasingly accepting non-agricultural work.So,it is still lack of understanding how farmers and herdsmen balance reclamation opportunities,risks,labor force migration and population pressure brought by climate change.Therefore,it is necessary to study the farmland use decision-making of farmers and herdsmen under the background of climate change and labor force migration,and to analyze the factors affecting farmland use decision-making,so as to provide theoretical basis for enhancing farmers’ resistance to the risks brought by climate change and formulating effective adaptation strategies for farmland use under climate change and agricultural development plans.The Tibetan Plateau,is a typical ecologically fragile area,an important ecological security barrier and strategic resource reserve base in China.The way of farmland utilization should not be neglected.For example,the reclamation of grassland in the agro-pastoral ecotone will also lead to grassland degradation and desertification,which is irreversible.In view of this,this paper takes the the Yarlung Zangbo River,Nyangqu River,and Lhasa River regions,the Pum Qu River Basin,the Yellow River-Huangshui River Valley and Zamtang county as the research areas,and uses 947 household questionnaires in four regions to analyze the farmland utilization decision-making of farmers and herdsmen under the background of climate change and labor force migration,and quantitatively studies the influencing factors of farmland utilization decision-making of farmers and herdsmen.The results show that under the background of climate change and labor migration,farmers and herdsmen mostly adopt the intensive strategy,mainly with long-term investment,and fewer farmers and herdsmen adopt the reclamation strategy.Finally,according to the results of the study,the relevant policy recommendations are put forward.Specifically,the results are as follows:(1)The perception of farmers and herdsmen in the study area is basically consistent with the meteorological station data except the perception of precipitation.Most farmers and herdsmen perceive that the climate conditions are still "warm-dry",and that the snowstorms decrease and droughts increase.In addition,most farmers and herdsmen believe that climate change has not a significant impact on agriculture.(2)Under the background of climate change,with the acceleration of urbanization,farmers and herdsmen are increasingly recognized for non-agricultural work,coupled with government control,making the phenomenon of reclamation not universal.Only 18.16% of the farmers and herdsmen have reclamation behavior,and most of the area of reclaimed land is between 0.02—0.20 hm2.Through the analysis of the survey data,it is confirmed that the reclamation of farmers and herdsmen is the result of climate change and population pressure.The econometric results also show that there is a significant negative correlation between farmers’ and herdsmen’s reclamation decision-making and their annual income per capita.(3)The level of mechanization in the study area is relatively high,reaching more than 70%.Farmers and herdsmen mainly purchase agricultural tractors and mechanical ploughs,but invests less in micro-tillers and pumps,and most farmers and herdsmen buy agricultural equipment after 2000.At the same time,farmers and herders’ income from non-agricultural activities has promoted the mechanization of local farmland.In addition,the econometric results also show that there is a significant positive correlation between the mechanized investment of farmers and herdsmen and their perception of the overall change trend of spring frost and the number of livestock.(4)The irrigation level of cultivated land in the study area is relatively high,and furrow irrigation is the main method.Irrigation plots are small,ranging from 0.02 to 0.30 hm2.Most irrigation facilities are built by the government,while the investment of farmers and herdsmen in irrigation is relatively low.The main reasons promoting their own investment in irrigation are the perception of overall change trend of frost in spring and the average area of farming plots,while the high per capita monthly income inhibits farmers and herders’ investment in irrigation.(5)The majority of farmers and herders’ independent fertilizer input basically did not change,only 28.83% of farmers and herders’ fertilizer input increased.The results show that the decision-making of increasing fertilizer input by farmers and herdsmen is negatively correlated with their perception of winter duration,precipitation and dependency ratio,and positively correlated with their perception of spring frost,the number of livestock,the distance from residence to town,and the average area of farming land.更多还原