Spatial Distribution Pattern of Root Sprouts under the Canopy of Malus sieversii in a Typical River Valley on the Northern Slopes of the Tianshan Mountain

Malus sieversii is a precious wild fruit tree resource, and its sustainable reproduction is of great significance to the conservation of wild fruit tree germplasm resources and the stability of wild fruit forest ecosystems. In recent years, the natural population number and area of distribution of the Malus sieversii have been declining due to pests, water limitations, and human activities. Root sprouts are a primary means of rejuvenation of the Malus sieversii. A reasonable spatial distribution pattern is conducive to the growth of Malus sieversii plants and the ecological restoration of wild fruit forest populations. However, the spatial distribution pattern of root sprouts still needs to be discovered, which constrains our understanding of the mechanisms underlying the damage and management of Malus sieversii. Therefore, this paper examines the study area of the Gilgalang River Malus sieversii forest in Gongliu County, Ili Valley, Xinjiang. The topographic data and high-resolution images were first obtained using ultra-low-altitude photogrammetry and total station measurement techniques, then spatial pattern analysis and standard deviation ellipse analysis were used to investigate the spatial distribution pattern of root sprouts, and, finally, the factors affecting the spatial distribution pattern of root sprouts were investigated by principal component analysis and grey correlation analysis. The results show that: (1) Under-canopy Malus sieversii root sprouts are clustered and randomly distributed along the root system, with the degree of clustering decreasing with increasing distance; (2) Spatial orientation and distance from the maternal plant are the main factor affecting the sprouting of Malus sieversii roots, explaining 73.69% of the total variance; (3) Under sediment accumulation and water erosion, the root sprouts under the canopy are mainly distributed in the downslope direction. The shape is similar to the “clover type”. The results of this study can provide a theoretical basis for conserving Malus sieversii germplasm resources and a solid scientific basis for the ecological restoration of plants under anthropogenic disturbance.