The features of agroforest ecosystems and their impact on the environmental indicators of Chushandian reservoir’s buffer strips

Abstract

The rational for choosing the research topic. The contribution of buffer zones to global climate change has been widely recognized. However, the management and use of riparian zones remains problematic worldwide, especially as demand for agricultural land increases. Thus, the combination of agricultural production with environmental benefits has become an important obstacle for the sustainable development of coastal zones (reservoir banks). The development of agroforest ecosystems provides a compromise solution to these conflicts and has great potential for popularization in the future. Agroforest ecosystems advocate the harmonious combination of forest trees or shrubs with organic agriculture or livestock, integrating and synergizing the benefits of above- and belowground ecological niches to maximize the landscape, ecological, and economic benefits of the land. Research on the characteristics and environmental impacts of adapted agroforest ecosystems in the riparian buffer strips is still insufficient and knowledge is limited. Thus, strengthening research on environmental indicators (vegetation succession, soil structure, soil properties, soil ecology, and microbial community) and economic productivity (yield and economic income) of adapted agroforest ecosystems in the riparian buffer strips contributes to the development and promotion of this technical measure in the riparian zones. It is also of great importance for understanding the relationship between “soil-vegetation cover” and “bank-water system” and the environmental benefits of the “land-water ecotone”. The scientific novelty of the obtained results. For the first time, a comprehensive survey was carried out in order to generalize the state of development and the application potential of the existing agroforest ecosystems in the buffer zones of the Chushandian reservoir. For the first time, the ecological effectiveness of such factors as soil properties, soil aggregate stability, changes in carbon stocks, vegetation biodiversity, and microbial community structure for adapted agroforest ecosystems in reservoir buffer strips was investigated. For the first time, the main factors affecting the ecological efficiency of adapted agroforest ecosystems in the specified research region were analyzed. The economic potential of these adapted agroforest ecosystems has been established for the first time. Improved understanding of ecological efficiency for adapted agroforest ecosystems (at a fine scale relative to distance). The expediency of creating adapted agroforest ecosystems in the protective strips of the reservoir is substantiated. Measures to increase economic productivity and preventive measures for organic farming in adapted agroforest ecosystems in the buffer zones of the reservoir are recommended. The practical significance of the obtained results. The thesis provides strong evidence of the feasibility of adapted agroforest ecosystems in the buffer zones of the reservoir. Through a comprehensive literature review, it was concluded that adopted agroforest ecosystems in reservoir buffer zones are an important trade-off between agricultural production and environmental benefits that can maximize environmental benefits while preserving agricultural production and have great potential for application in future riparian zone management and operation. The author proved that adapted agroforest ecosystems in the buffer zone of the reservoir have an advantage in increasing the biodiversity of vegetation and maintaining species population. Adapted agroforestry ecosystems in the buffer strips of the reservoir have the highest number of plant species (27) than other land use types. The author established that adopted agroforest ecosystems in the reservoir’s buffer strips can maintain soil vitality and improve the riparian habitat quality. Adopted agroforest ecosystems in reservoir’s buffer strips showed lower NH4-N (ammonium nitrogen) content - 39.55 mg/kg and higher NO3-N (ammonium nitrogen) - 3.62 mg/kg than the other land-use types. These ecosystems in reservoir’s buffer strips showed higher MBC (microbial biomass carbon) content - 239.52 mg/Kg, MBN (microbial biomass nitrogen) content - 27.75 mg/Kg and DOC (dissolved organic carbon) content - 18.38 mg/Kg than the other land use types. The TP (total phosphorus) content - 0.26g/Kg in woodland was lower than the other land-use types, which indicated that adopted agroforest ecosystems in the reservoir’s buffer strips have low capacity to adsorb and retain phosphorous. The BD (bulk density) content - 0.99 g/cm3 and SWC (soil water) content - 19.28 % in woodland were lower than in other land use types, indicating that adapted agroforest ecosystems in buffer strips of the reservoir can effectively reduce soil water content and accelerate water infiltration. The author established that adapted agroforest ecosystems in buffer strips of the reservoir can support higher microbial activity of the soil, improve the carbon storage potential in the soil. The TC (total carbon) content - 14.78 g/Kg and TN (total nitrogen) content - 1.307 g/Kg in woodland was higher than in other land-use types, indicating that adapted agroforest ecosystems in reservoir buffer strips can improve soil carbon sequestration potential. The Simpson index, distance to the watercourse and MBN (microbial biomass nitrogen) were the main factors that influenced the soil properties in the reservoir’s buffer strips. In addition, the author proved that the type of land use affects soil properties through soil stoichiometry, and the distance to a watercourse affects soil properties through plant biodiversity. The author found that adopted agroforest ecosystems in the reservoir’s buffer strips can maintain stable soil structure, regulate carbon stock change. The MWD (mean weight diameter) in agroforest ecosystems was higher than the other land-use types. The OCP (organic carbon pool) content - 4468.07 g/m2 in W20 (on the site of the agroforestry ecosystem in the reservoir’s buffer strips) was highest than all the other sites. The silt particle- size which was associated with carbon - TC2) may play the role of carbon turnover property intermediary. The thesis confirms that adapted agroforest ecosystems in reservoir buffer strips can improve microbial diversity, maintain stable community structure, and enhance microbial metabolic activity. The most common type in buffer strips of reservoirs of agroforest ecosystems is Proteobacteria, Acidobacteriota, Actinobacteria, and Chloroflexi. The adopted agroforest ecosystems in the reservoir’s buffer strips showed that more ASVs (amplicon sequence variants) were deplete, and the top 5 abundance classified at Phylum level were Acidobacteriota, Actinobacteriota, Proteobacteria, Chloroflexi. The co-occurrence network shows that adopted agroforest ecosystems have low diameter (5.569) and clustering coefficient (5.689), higher negative links (872). Functional microbial community abundance, cell motility, and signal transduction were significantly lower in agroforest ecosystems, and terpenoid, polyketide, carbohydrate, amino acid terpenoid, and polyketide metabolism were significantly higher than in other land use types. This indicates that the adapted agroforest ecosystems in the buffer strips of the reservoir have stronger metabolic activity to maintain the functional stability of the microbial community. Homogeneous selection followed by dispersal limitation was the main process that dominated microbial community structure in agroforest ecosystems. It was established that TC (total carbon) is the main driving factor affecting the structure of the microbial community in the reservoir’s buffer strips. The thesis shows that adapted agrofores ecosystems in buffer zones of the reservoir can support stable economic income. Given the extensive management of agroforestry ecosystems in the buffer zones of the reservoir, the author notes that there is still considerable potential for increased yields and economic productivity. Suggestions and questions for the management's attention are provided. The author recommends that farmers pay attention to strengthening the management of the drive areas to improve the quality of the soil and maintain the productivity of the land. In addition, the use of phosphorus-containing compounds (fertilizers, pesticides, etc.) should be strictly prohibited and the use of biological control measures should be improved, and organic farming should be used whenever possible.