【作者】 张永红；

【导师】 孙国钧；

【作者基本信息】 兰州大学 ， 生态学， 2020， 硕士

【摘要】 放牧干扰对草地生态系统具有重要的影响。在放牧过程中,由于牲畜的自由采食和踩踏,在空间尺度上增加了景观多样性。我国黄土高原半干旱区广泛分布着由牲畜踩踏形成小路径和植物斑块组成的景观,即牧道景观。本研究以黄土高原半干旱丘陵区山羊牧道景观为研究对象,选取三块草地（G₀、G₁和G₂）为研究区域,并将它们翻耕以去除原始的山羊牧道,其中无山羊通行的草地作为对照（G₀）。同时拣出G₀和G₁内的植株,保留G₂内的植株。利用摄影测量和遥感技术,开展为期6年的野外观测。试验通过牧道密度和牧道节点两个方面定量刻画了山羊牧道网络的形成和动态变化过程,并对比分析了研究区域内植物群落特征和物种多样性特征,进而探讨了山羊牧道景观的发育和演化过程。本研究得出的结果如下:1.在山羊牧道网络的形成过程中,随着牧道的增加,各阶段优势种也不断更替。G₀、G₁和G₂样地内的植物群落共计14科21属24种,菊科（35.71%）和禾本科（28.57%）所占比例大于其他科植物。放牧干扰对植物群落组成结构具有显著的影响。与G₀相比,G₁和G₂样地的植物丰富度和多样性指数增长,但由于山羊的采食和踩踏使其植物群落密度和盖度降低。2.山羊牧道网络由牧道和节点组成,牧道转弯或交叉处即为节点。翻耕一个月后出现少量平行牧道,其并未贯穿于整个样地,四个月后出现平行牧道贯穿于整个样地并形成分叉,半年后,平行牧道在样地内均匀分布,形成山羊行走的主干道,且平行牧道间出现连接牧道。在牧道网络恢复过程中,一度节点逐渐下降,二度节点先增加后下降,三度节点逐渐增加,四度节点逐渐下降最后消失。牧道密度与节点总数呈正相关关系,牧道网络连通性增强。3.牧道网络的形成与植物群落具有密切的关系。翻耕前,G₁和G₂样地的牧道密度分别为24.88%和20.84%,一度节点分布频率都为0,二度节点分布频率分别为37.28%和33.94%,三度节点分布频率分别为57.40%和60%,四度节点分布频率均最低。翻耕后的第6年（2019年）,牧道网络仍未恢复到原始状态。G₁和G₂的牧道密度分别为20.27%和19.38%,一度节点分布频率都为0,二度节点分布频率分别为51.20%和43.82%,三度节点分布频率分别为48.80%和56.18%,四度节点分布频率也都为0。在相同恢复时间内,G₂出现更多可采食的植物,继而增加了山羊的踩踏频率和停留时间,其牧道网络形成速度较快,更接近原始牧道网络。4.山羊是山羊牧道景观的主要驱动力。翻耕后,对于无山羊经过的样地内未出现牧道;而对于有山羊经过的样地,半年内便变形成主干牧道,且与周围植物群落相互作用形成植物斑块,即形成牧道景观。更多还原

【Abstract】 Grazing disturbance has an important impact on the grassland ecosystem.During the grazing process,landscape diversity has been increased on a spatial scale due to the free feeding and stamping of livestock.The landscape composed of small paths and plant patches trampled by livestock,named of track landscape,is widely distributed in the semi-arid area of the Loess Plateau in China.In this study,the goat track landscape in the semi-arid hilly area of the Loess Plateau was taken as the research object.The three grasslands（G₀,G₁,and G₂）were selected as the study area,and ploughed to remove the original goat pasture.Grassland without goats was used as a control（G₀）.The plants in G₀ and G₁ were picked out,and the plants in G₂were retained.The field observation was carried out for 6 years by using photogrammetry and remote-sensing technology.The experiment quantitatively depicts the formation and dynamic changes of the goat track network through track density and vertices,and comparatively analyzes the characteristics of plant communities and species diversity in the study area,and then discusses development and evolution process of the goat track landscape.The results of the study are as follows:1.During the formation of the goat track network,the dominant species at various stages have been continuously replaced with the development of track.The plant communities in the G₀,G₁ and G₂ plots had 14 families,21 genera and 24species,and the proportion of Compositae（35.71%）and Gramineae（28.57%）were greater than that of other families.The disturbance of grazing has a significant effect on the composition and structure of plant communities.Compared with G₀,the plant richness and diversity index of G₁ and G₂ increased,but the plant density and cover decreased due to feeding and trampling of goats.2.The goat track network consists of track and vertices,and the track road turns or crosses are vertices.A few parallel track appeared one month after tilling,which did not penetrate the entire plot.Four months later,parallel track penetrated the entire plot and formed bifurcations.Half a year later,parallel tracks were evenly distributed and formed a main road for goats to walk,and connecting track roads appeared between parallel track roads,and the connectivity of the track network was enhanced.Throughout the process,the first-degree vertices gradually decreased,the second-degree vertices first increased and then decreased,the third-degree vertices gradually increased,and the fourth-degree vertices finally disappeared.The density of the track was positively correlated with the total number of vertices,so the connectivity of the track network was enhanced.3.The formation of the track network has a close relationship with the plant community.Before tilling,the track density of the G₁ and G₂ plots were 24.88%and20.84%respectively,the first-degree vertices distribution frequency were 0,the second-degree vertices distribution frequency were 37.28%and 33.94%,the third-degree vertices distribution frequency were 57.40%and 60%,the distribution frequency of the fourth-degree vertices were the lowest.In the 6th year after ploughing（2019）,the track network has not yet returned to its original state.The track density of G₁ and G₂ were 20.27%and 19.38%respectively,the first-degree vertices distribution frequency were 0,the second-degree vertices distribution frequency were51.20%and 43.82%,the third-degree vertices distribution frequency were 48.80%and 56.18%respectively,the fourth-degree vertices distribution frequency was also 0.During the same recovery time,more edible plants appeared in G₂,which increased the trampling frequency and residence time of goats.The formation speed of the track network was faster and closer to the original track network.4.Goats are the main driving force of goat track landscape.After ploughing,there was no track in the plot without goats.For the plot with goats,it would become a main track within six months,and interact with the surrounding plant communities to form plant patches,that is,track landscape.更多还原