Abstract: The valleys in Southwest China are hot and dry because of rain shadow effect.On their slopes,the main vegetation is savanna.Due to heavy human disturbance,the vegetation has been devastated or severely degraded,resulting in severe water and soil erosion.Some tree species such as Eucalypt,Acacia,and Leucaena have been introduced for revegetation and shown good growth during the past ten years,but little is known whether the insect community diversity is recovered along with the revegetation.This study investigated the species diversity of insect community collected from six different vegetation formations in Yuanmou dry and hot valley,including two natural (twitch-grass and aalii brushwood) and four artificial vegetations (pure Eucalyptus,Eucalyptus camaldulensis+Leucaena leuacocephala mixed forest,Acacia auriculaeformis+Leucaena leucocephala mixed forest,and Eucalyptus camaldalensis+Acacia auriculaeformis mixed forest).The results showed that vegetation component was the key factor affecting the species diversity of insect community.Mixed forestation was an effective forestation technology,which promoted insect community diversity and helped local insect settle down in degenerated place.By using principal component analysis,the six vegetation formations were divided into tow groups.The first group was eucalyptus pure plantation,with its environment unitary and wilder,and the second group was made up by the other five vegetation formations,with richer species diversity and higher moisture.The characteristics and quantities of the dominant and peculiar insects in different vegetation formations showed that among three mixed forests,Acacia auriculaeformis+Leucaena leucocephala mixed forest was the best afforestation model which could improve environment and increase insect species diversity,although some factors such as human activity slowed down the recovery of insect community diversity.

Key words: Stock density indices, Community structure, Species diversity, Nekton, Taiwan Strait