半干旱黄土高原丘陵山羊牧道景观结构与形成机制

发布时间：2018-08-03 15:26

【摘要】：牧场占陆地表面25%以上,对全球生态过程和社会经济具有重要影响。放牧牲畜采食踩踏形成的小路径,即牧道,广泛分布于干旱、半干旱以及湿润和高山地区的坡地牧场。半干旱黄土高原丘陵分布有典型的牧道景观,本文定量刻画了山羊牧道景观基本景观单元结构、牧道网络结构,并分析了牧道网络中的山羊活动行为。在基本景观单元结构方面,我们首先将基本景观单元划分为三个组成部分,分别为:牧道、凸肩区和坡间区,继而通过样方法和自制微地形采样框,获取了每个组成部分的微地形特征、植物群落特征和土壤特征。在牧道网络结构方面,通过摄影测量和地理信息系统相结合,运用图论方法,对牧道网络结构进行了定量刻画。在山羊活动行为方面,通过对山羊走过牧道景观过程的拍摄,重建了山羊在牧道网络中的移动轨迹,刻画了山羊采食和路径选择行为。上述研究得到如下主要结果:1.牧道景观具有显著的微地形、植物和土壤空间异质性,形成带状格局。牧道景观的基本景观单元从上到下包含三个组成部分,牧道、凸肩区和坡间区。牧道的坡度低,土壤容重高,具有表层土壤硬壳,很少有植物和生物结皮覆盖。凸肩区的坡度居中,土壤容重最低,植物地上生物量和土壤养分含量最高。坡间区坡度最大,土壤容重居中,土壤养分含量最低,生物结皮覆盖面积(80%)最高。降水后水分分配具有相应的空间异质性:牧道最多,坡间区最少,凸肩区中等。通过地表径流和地下存贮方式,牧道为凸肩区植物生长提供水分。2.牧道网络结构与山羊采食行为相适应。节点密度0.3个/m2,其中约30%为2度节点,60%为3度节点,10%为4度节点,没有发现度数大于4的节点。牧道网络由平行牧道和连接牧道组成,平行牧道几乎平行于水平面,偏转角(与所在山坡水平线夹角)8.0°,连接牧道偏转角27.4°,作为平行牧道之间的连接。牧道网络的基本连接单元可以看作是由一个节点和直接与该节点连接的所有边组成,本文发现牧道网络由14种基本连接单元组成,继而分析了每种类型的结构。牧道网络中多边形长宽比超过4,水平长度3~8 m,垂直长度仅0.6~1.6 m。3.牧道网络可能会提高山羊采食效率。牧道平缓的坡度和坚硬的表面有助于山羊更加平稳的站立和通过,减少移动能量消耗。牧道植被覆盖低,植物对山羊移动阻挡小,减少了移动距离而增加了效率。山羊实际使用牧道偏转角和转角都相对小,偏转角平均11°,转角平均16°。连接牧道偏转角具有一定程度的优化性,爬山效率可能较高。超过93%的采食发生于牧道,牧道不仅是牲畜行走道路,也是采食道路。牧道网络中山羊采食位点主要分布于山羊上前方约80 cm半径内,该距离意味着山羊无需离开牧道即可采食88.0%的非牧道区域。4.牧道景观维持过程中,存在一个正反馈过程。山羊踩踏降低牧道坡度、增加土壤容重、形成表面土壤硬壳,这有助于牧道捕获并且二次分配水到凸肩区,形成凸肩区的植物条带和“条带状肥料岛”;牧道网络有助于减少能量消耗,增加采食效率,从而山羊更倾向于使用牧道。牧道也具有可能的动态机制,坡间区下部、牧道和凸肩区对沉积物的有效捕获将导致牧道宽度向内增加,使得牧道向上移动。总之,牧道对微地形、水文、植物群落、土壤和山羊采食效率具有重要影响。半干旱黄土高原丘陵,存在与不存在牧道情况下,景观结构和功能明显不同。深入了解这些不同可能会对完善当前该区域正在实施的水土保持政策和在丘陵牧场禁牧的政策有帮助。
[Abstract]:Pasture accounts for more than 25% of the land surface, which has an important impact on the global ecological process and social economy. The small path formed by grazing animal feeding and trampling is widely distributed in arid, semi-arid and humid and alpine areas. The Hilly of the semi-arid Loess Plateau has a typical pasture landscape. This paper quantitatively depicts the goat. The basic landscape unit structure of the pastoral landscape, the structure of animal husbandry network, and the activity behavior of goat in the pastoral network are analyzed. In the basic landscape unit structure, we first divide the basic landscape units into three components, namely, pasture, bump area and interslope area, and then through sample method and self-made micro terrain sampling frame, we get the results. The microtopography of each component, the characteristics of the plant community and the characteristics of the soil. In the structure of the animal husbandry network, the structure of the animal husbandry network was quantified by the combination of photogrammetry and geographic information system, and the graph theory was used. In the activity of goats, the mountain was taken to reconstruct the mountain through the shooting of the landscape process of the goat through the pasture. The moving track of sheep in the pastoral network depicts the behavior of goat feeding and path selection. The main results are as follows: 1. the pasture landscape has significant microtopography, spatial heterogeneity of plants and soils, and forms a banded pattern. The basic landscape units of the pastoral landscape contain three components, pasture, shoulder area and slope from upper to lower. In the interspace area, the slope of the pasture is low, the soil bulk density is high, the soil crust of the surface soil is high, and there are few plants and biological crust covering. The slope of the shoulder area is in the middle, the soil bulk density is the lowest, the aboveground biomass and soil nutrient content are the highest. The slope degree is the largest in the interslope area, the soil bulk density is the lowest, the soil soil nutrient content is the highest, and the biological crust covering area (80%) is the highest. The water distribution after precipitation has the corresponding spatial heterogeneity: most of the pastoral route, the lowest interslope area and the middle of the convex shoulder area. Through surface runoff and underground storage, the animal husbandry channel provides water.2. network structure to the goats' feeding behavior. The node density is 0.3 /m2, of which about 30% are 2 degrees, 60% are 3 degrees, 10% For the 4 degree node, there is no node with a degree greater than 4. The pastoral network is composed of parallel grazing and connection pastes. The parallel pasture is almost parallel to the horizontal plane. The deflection angle (with the angle of the horizontal line at the slope of the mountain) is 8 degrees and the pasture deflection angle is 27.4 degrees. The basic connection unit of the pastoral network can be regarded as a one. It is found that the node and all sides are directly connected to the node. In this paper, it is found that the pastoral network is composed of 14 basic connection units. Then, each type of structure is analyzed. The length and width ratio of polygon is over 4, the horizontal length 3~8 m, the vertical length only 0.6~1.6 m.3. grazing network may improve the feeding efficiency of the goat. The degree and the hard surface help the goat to stand and pass more smoothly, reduce the movement energy consumption. The vegetation cover of the pasture is low, the growth of the goat's movement is smaller, the moving distance is reduced, and the efficiency is increased. The goats are actually using the grazing angle and angle are relatively small, the deflection angle is 11 degrees and the rotation angle averages 16 degrees. With a certain degree of optimization, the efficiency of mountain climbing may be higher. More than 93% of the grazing occurred on the animal husbandry Road, and the grazing road is not only the road of livestock walking, but also the way of feeding. The goat feeding sites in the animal husbandry network are mainly distributed within the 80 cm radius of the goat on the front of the goat. This distance means that the goat can take 88% of the non grazing area without leaving the animal road. There is a positive feedback process in the process of maintaining the landscape of the.4. pasture. The goats tread down the slope of the pasture, increase the soil bulk density, and form the hard shell of the surface soil, which is helpful to the grazing and two distribution of the water to the convex shoulder area, the plant strip of the convex shoulder area and the "strip fertilizer island", and the animal husbandry network helps to reduce the energy consumption and increase the energy consumption. Grazing efficiency, thus the goat is more inclined to use animal husbandry. Animal husbandry also has a possible dynamic mechanism. The lower part of the interslope area, the effective capture of the pasture and the shoulder area will lead to the increase of the pasture width and make the pasture move upwards. In short, the pasture has an important effect on the microtopography, hydrology, plant community, soil and goat feeding efficiency. The landscape structure and function of the Hilly of the semi-arid Loess Plateau is distinctly different from that of the non existence of pasture. Understanding these differences may help to improve the current policy of soil and water conservation in the region and the policy of prohibiting the grazing in the hilly pasture.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S812.9;S827

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