4.3 Land use conversion characteristics and wild tending areas planning in the climate-stable areas of T. chinense
Human activities are a major factor leading to global change, which overwhelm the natural changes brought about by climate change in the past few thousand years (Houghton et al., 1990). Human activities such as agriculture, forestry, and other land management have changed the entire landscape, thus affecting the flora and fauna communities of many ecosystems worldwide (Ojima et al., 1994). In China, the climate-stable areas of T. chinense are mainly distributed in humid and semi-humid areas, and the major changes of land use types in this area in the future are mainly construction land and grassland. It is predicted that the construction land in the region will expand rapidly in the next hundred years, an increase of about 46.94% compared with 2015. The distribution of construction land is mainly related to population density. Future population projections indicate that although the proportion of the population in the southeast of China will decrease over the next 20 years, the change will only be between 0.1% and 0.3% (L. Wang et al., 2014). Although the overall pattern of spatial population distribution in China will not change fundamentally, with the southeast being densely populated and the northwest being sparsely populated, the scale and degree of population agglomeration in urban agglomerations are gradually increasing, and the trend of population agglomeration is more obvious (L. Wang et al., 2014) Therefore, this study predicted that the rapid growth of the construction land ofT. chinense in the future climate-stable areas in China is in line with the actual situation.
In addition to the rapidly expanding construction land, the grassland areas in the climate-stable areas have also changed significantly, and their areas have decreased by 15.18% compared with 2015. Grassland ecosystem is the largest ecosystem in land surface types and occupies an extremely important role in the terrestrial ecosystem. The impact of human activities on the grassland ecological system in recent years growing (X. Zhang et al., 2022). Since the 21st century, the Chinese government has invested vigorously in ecological restoration projects and carried out ecological restoration work, such as returning farmland to grassland, which significantly affects the restoration of grassland soil nutrients (carbon) (C. Chen et al., 2019). In the climate-stable areas of T. chinense in the next hundred years, there will be no such transfer from 2050 to 2090, except that a small amount of cultivated land will be transferred to grassland from 2015 to 2050. Therefore, the soil nutrients restored by returning cultivated land to grassland in the next hundred years will be very low. In the future, the areas of construction land transferred to grassland in the region will increase yearly. It is estimated that by 2090, the areas of construction land transferred from 2070 will account for about 1.22% of the grassland areas in 2090. Large scale construction projects have not only seriously damaged grassland vegetation and topsoil, resulting in a sharp decline in grassland carbon storage, which will take many years to recover, but also exacerbated climate change and indirectly affected grassland ecosystem, causing a certain impact (X. Chen & Shang, 2011). Therefore, in the context of future climate change and land use change, the natural habitat suitable for the growth of T. chinense will face a huge threat.
Under land use and climate change, although climate change increases the total suitable areas of T. chinense , it will seriously threaten the high suitable areas. In the climate-stable area of T. chinense under different climate scenarios, the habitat areas suitable for the growth of T. chinense will gradually reduce due to the change in land use. These future changes may limit the expansion of wild populations. Furthermore, combined with excessive harvesting, wild resources are increasingly depleted, making it difficult for the species to continue. At present, wild resources can not meet the needs of medicine, but its artificial breeding technology is not mature. And according to the Non-grain Production policy in China, cultivated land is forbidden to grow economic crops. Therefore, it is necessary to carry out wild tending of T. chinense , which can promote the recovery and sustainable utilization of T. chinense population. Wild tending is an available approach to solve the contradiction between the shortage of wild resources of medicinal plants and the large market demand. It is a production mode of artificially or naturally increasing the population of target medicinal materials, which can not only greatly increase the available resources, but also maintain the community balance after over-collecting, and continuously supply genuine-quality medicinal materials (S. Chen et al., 2004). The wild tending area has the characteristics of primitive environment, less human intervention and far away from pollution sources. It is very important to predict the change range of the suitable habitat of T. chinense for formulating agricultural policies and planting planning (Shen et al., 2021). Based on the current high suitable areas of T. chinense in China, combined with the future climate and land use change, this study planned the wild tending areas of T. chinense for hundred years. This can effectively avoid the huge economic losses caused by blind planting. According to the results of the wild tending area, we made the following recommendations: (1) The wild tending areas of T. chinense in China are mainly distributed in the north, northeast, and southwest of China. In the future, most of the areas will be high suitable area, and only a few areas will be transformed into medium or low suitable areas. It is suggested that germplasm collection and diversity evaluation of wild plants should be carried out in the climate transformation areas, which is conducive to the conservation and domestication of the core germplasm of T. chinense . (2) The local government should take more actions to protect the natural ecology, enhance the awareness of the protection and restoration of local natural land types, and avoid irreversible damage to them. (3) The planned wild tending area of T. chinense should be combined with local policies, integrate ecological, economic, and social benefits, and strengthen the establishment of wild tending medicinal material bases. This will effectively solve the contradiction between T. chinenseecological protection and biodiversity, resources and supply demand. (4) The precondition of artificial breeding and wild tending is to master the basic characteristics of growth and development of TCM. Therefore, we should strengthen the research on population ecology and developmental biology, especially on the influence of different hosts on the composition and the mixed cultivation mode with other crops. This can not only maintain the stability of T. chinense population, but also improve the quality and yield of T. chinense . At the same time, the mixed cultivation mode can effectively make full use of land resources and make up for the shortage of grassland resources in some areas due to the dense population.