Settlements are comprehensive carriers of the material form expression and social appearance of human activities under specific geographical environmental choices. The analysis and preservation of their forms are important principles and strategies for rural settlement planning and construction. In this study, 28 settlements in the farming–pastoral zones in eastern Inner Mongolia were selected as the research objects. By combining fractal geometry and computer programming, the relationship between the boundary form, spatial structure, and architectural order of the settlements was quantitatively expressed, and quantitative indicators that better summarize the form of the settlements in the farming–pastoral zones in eastern Inner Mongolia were extracted. Then, factor analysis and cluster analysis were conducted using the Statistical Package for the Social Sciences software (SPSS26.0) to obtain the characteristic types of settlement forms. Finally, the classification results were combined with social and humanistic factors and the geographical environment to test the rationality of the results. The results show that (1) five form indicators effectively describe the settlement forms in the research area, among which the shape index, dimension of the public space, and architectural density play a crucial role in the spatial structure factors. (2) In this study, we mainly used a data collection and processing–principal component extraction and systematic clustering-type division method to complete scientific research on settlement form classification. (3) By combining the clustering results with the spatial form features and analysis mainly based on spatial structure factors, the settlement forms in the farming–pastoral zones in eastern Inner Mongolia are described as three typical types: multidirectional expanding settlement, settlement patterns extending at both ends, and centripetal development settlement. Furthermore, the characteristics of the human–land relationship implicit in each type of settlement form are explained, achieving a scientific representation and classification of the settlement forms. The research results provide useful quantitative guidance for rural revitalization, settlement form optimization, and preservation in the farming–pastoral zones in eastern Inner Mongolia

Salix psammophila C. Wang & C. Y. Yang is an important windbreak and sand-fixing shrub species in Northwest China, with excellent characteristics such as resistance to drought, wind, and sand. S. psammophila needs to be stubbed flat after several years of growth to continue to grow, otherwise, its growth rate will slow down and even begin to die. To understand the genetic regulatory mechanism of secondary growth in S. psammophila, cell structure and transcriptome analysis were performed on the secondary xylem and secondary phloem of stems. The results showed that the secondary xylem and the secondary phloem of S. psammophila were well developed at 1, 2, and 3-year-old stages, and the secondary growth changes mainly occurred in the secondary xylem at the 2 to 3-year-old stage, with a faster growth rate. The CSE2 and CSE1 genes that regulate CSE (caffeoyl shikimate esterase) have high sequence similarity (92% and 93%) with the CSE2 and CSE1 genes of the genus Populus, respectively, and regulate lignin biosynthesis. Notably, the expression levels of these two genes decreased in the secondary xylem of 3-year-old S. psammophila, indicating that the rapid growth of S. psammophila may be related to lignin biosynthesis. Weighted gene co-expression network analysis (WGCNA) was utilized to screen candidate TFs and genes involved in the secondary growth processes of S. psammophila, which were categorized into six co-expression modules. A total of 79 genes were selected from these co-expression modules, and co-expression network maps of the genes were constructed. The results indicate that the secondary growth of S. psammophila was regulated by a TF regulatory network. Interestingly, PLATZ TFs were involved in the rapid secondary growth and stress tolerance in S. psammophila. This hints that S. psammophila may promote secondary growth by increasing stress tolerance.