Biomass and allocation of young Azadirachta indica and Acacia auriculiformis for different restoration patterns in dry-hot valley

Key words: 
• forest ecology /
• dry-hot valley /
• Azadirachta indica /
• Acacia auriculiformis /
• biomass allocation /
• restoration pattern

Abstract: To understand biomass and its allocation in tree species for plantations using different restoration patterns for dry-hot areas，and to evaluate the benefits of mixed patterns of tree species，biomass and allocation characteristics in nine-year-old Azadirachta indica and Acacia auriculiformis were studied in the dry-hot Yuanmou Valley. Data from sample trees were averaged to determine biomass and allocation，and 17 Azadirachta indica trees and 16 Acacia auriculiformis trees in different diameter classes were cut to build allometric equations. One-way ANOVA showed no significant differences between biomass per plant of Azadirachta indica or Acacia auriculiformis in the pure and mixed plantations. Biomass in the mixed plantation was 16.525 thm-2；with Azadirachta indica it was 7.837 thm-2；and for Acacia auriculiformis it was 27.802 thm-2. Biomass of Azadirachta indica organs varied as follows: in the pure plantation：stem＞root＞branch＞bark＞leaf and in the mixed plantation：stem＞branch＞root＞leaf＞bark；whereas Acacia auriculiformis varied as follows: in the pure plantation：branch＞stem＞root＞leaf＞bark and in the mixed plantation：stem＞branch＞root＞leaf＞bark. The root/shoot ratio of Azadirachta indica in the mixed plantation （0.280） was significantly smaller （P＜0.05） than in the pure plantation（0.400） and for Acacia auriculiformis mixed （0.163） it was larger （P＞0.05） than the pure plantation （0.132）. Relationships between organs or the organ and stem diameter （D） or stem diameter square multiplied by tree height （D2H） of the two species showed allometry with an allometric equation being y=axb. The allometric rate of the organs was as follows：for Azadirachta indica-branch＞leaf and stem＞root with aboveground＞belowground；whereas for Acacia auriculiformis-branch＞stem＞root＞leaf with aboveground＞belowground. In the dry-hot valley，when the two species were planted in the mixed pattern and compared to the pure plantation，biomass increased for Azadirachta indica and decreased for Acacia auriculiformis with biomass allocation for organs changing for the same tree species in different restoration patterns.［Ch，4 tab. 38 ref.］