Abstract: Eucalyptus is well-known as an effective reforestation tree species, due to its fast growth and high adaptability to various environments. Howev er, the introduction of Eucalyptus could have negative effects on the local envi ronment, e.g., inducing soil degradation, decline of groundwater level, and decr ease of biodiversity, and especially, there still have controversies on the effe cts of introduced Eucalyptus on the understory biodiversity of indigenous pl ant communities and related mechanisms. Based on a detailed analysis of the literatu res at home and abroad, it was considered that the indigenous plant species in t he majority of introduced Eucalyptus plantations were lesser than those in n atural forests and indigenous species plantations but more than those in other exoti c species plantations, mainly due to the unique eco-physiological characteristi cs of Eucalyptus and the irrational plantation design and harvesting techniq ues, among which, anthropogenic factors played leading roles. Be that as it may, the negative effects of introducing Eucalyptus on local plant biodiversity coul d be minimized via more rigorous scientific plantation design and management based o n local plant community characteristics. To mitigate the negative effects of Eucalyptus introduction, the native trees and understory vegetation in plantations should be kept intact during reforestation with Eucalyptus to favor the normal d evelopment of plant community and regeneration. At the same time, human disturba nce should be minimized to facilitate the natural regeneration of native species.

Key words: drought monitoring, evapotranspiration, triangle algorithm, simplified evapotranspiration stress index (SESI).