This study aims to select the optimal field tree species based on the photosynthesis process at the leaf scale. Experimental results indicate that, in terms of average water use efficiency, the ranking from highest to lowest is as follows: Populus tomentosa, Populus nigra, Salix matsudana, Elaeagnus angustifolia, and Populus euphratica. In terms of daytime transpiration water consumption, the ranking from highest to lowest is: Salix matsudana, Populus tomentosa, Populus euphratica, Elaeagnus angustifolia, and Populus nigra. Regarding the response relationship between light intensity and transpiration rate, Populus nigra and Elaeagnus angustifolia show a high degree of consistency in the timing of changes in transpiration rate and light intensity. Based on these research results, Populus nigra is the most suitable field tree species. The commonly perceived drought-resistant tree, Populus euphratica, has high transpiration water consumption and significant groundwater competition with crops, making it unsuitable as a field shelterbelt species. This study provides theoretical support for the selection of shelterbelt tree species in the oasis farmlands of southern Xinjiang and offers guidance for the optimal configuration of field tree species.