Effects of Different Weeding Methods on the Biomass of Vegetation and Soil Evaporation in Eucalyptus Plantations

Eucalyptus is a fast-growing, short-cycle, and high-efficiency tree species that is widely planted all over the world. Weeding is a special practice for Eucalyptus plantations that aims to cultivate seedlings and reduce vegetation competition for nutrients. In this study, a typical Eucalyptus plantation was selected as the research object, and the effects of two different weeding methods on soil evaporation and plant growth were studied. The results showed that mechanical weeding could effectively remove harmful weeds at an early stage, but after 30 days of weeding, all kinds of plants gradually recovered; herbicide weeding required long-term maintenance. The herbicide had the best control effect on Microstegium vagans (Nees ex Steud.) A. Camus, Dicranopteris dichotoma (Thunb.) Bernh, and Blechnum orientale, but the effect on shrubs was not obvious. The evaporation rate of soil increased rapidly within five days after mechanical weeding. After 139–200 days of weeding, the differences in evaporation between non-weeding, herbicide weeding, and mechanical weeding was decreased. The average daily evaporation was 0.52, 0.48, and 051 mm/d under these three practices. Meanwhile, weeding could promote Eucalyptus growth. Our results showed that weeding could significantly increase the height, diameter at breast height, and volume of Eucalyptus. One month after herbicide weeding or mechanical weeding (July), the height, DBH, and volume of Eucalyptus were significantly greater than those under non-weeding, but there was no significant difference between herbicide weeding and mechanical weeding. In addition, according to the different initial moisture contents, the evaporation rate increased with increasing initial moisture content and showed a very significant correlation.