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Optimizing the quantity and spatial patterns of farmland shelter forests increases cotton productivity in arid lands

Li, Xiaoyu, Liu, Lijuan, Xie, Jiangbo, Wang, Zhongyuan, Yang, Shuya, Zhang, Zhenyu, Qi, Shanzhong, Li, Yan
Agriculture, ecosystems & environment 2020 v.292 pp. 106832
Gossypium hirsutum, agricultural land, arid lands, cotton, crop yield, desertification, farming systems, forests, land degradation, landscape ecology, landscapes, models, radiation use efficiency, shelterbelts, water resources, watersheds, China
Land degradation/desertification occurs widely in arid lands and its outcomes are ecologically, economically, and socially negative. It is one of the most serious environmental problems that the world has to face today. The establishment of shelterbelts is an effective way to combat desertification and increase crop productivity in arid land farming practices. The ideal state of a farmland shelterbelt should be one that provides maximum protective effect with minimum use in terms of land and water resources. The positive effects of the shelter forest in desertification control were widely demonstrated. However, its effects on crop productivity are somewhat equivocal. Most studies were carried out at the plot or field scale, for evaluation on areas larger than the field-scale or plot-scale is difficult to undertake due to difficulties in setting controls. Thus, a comprehensive evaluation of the shelterbelt effect on crop yield at landscape scale is highly required. This study presents a rare insight into the optimum balance between minimizing the quantity of shelterbelts and maximizing the yield of crops based on the combination of a light-use-efficiency model (CASA) and landscape indices from a landscape ecology perspective. Farmland has rapidly expanded by 43 % in the Manas River Basin of Xinjiang, Northwest (NW) China, since 2000. Overexploitation of land resources and limited water resources lead to serious land degradation. However, development of shelterbelts was left behind in this area with an increase of 29.39 % only during this period. The shelterbelts are not only quantitively insufficient but also irrational in spatial patterns. Cotton productivity was significantly correlated with the spatial patterns of shelterbelts. The optimum of shelterbelt-to-patch ratio for maximizing cotton yield was 3.5 % in the study area. When the amount of shelterbelts is higher than 3.5 %, it is no longer associated with improved cotton yield. Simultaneously, higher connectivity and ring values always corresponded to higher cotton yields. Hence, in future practices, we should first ensure a certain amount of shelterbelts, while simultaneously optimizing the spatial configuration of shelterbelts to maximize their benefits. After the quantity of shelterbelts reached 3.5 %, however, improving the quality (the spatial configuration) --- increasing their connectivity and ring value, becomes the only effective way to improve crop yield.