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Nutrient accumulation and cycling in pure and mixed plantations of Azadirachta indica and Acacia auriculiformis in a dryhot valley, Yunnan Province, southwest China.

GAO Cheng-jie1, LI Kun1,2, TANG Guo-yong1,2, ZHANG Chun-hua1,2, LI Bin1   

  1. (1Research Institute of Resource Insects, Chinese Academy of Forestry, Kunming 650224, China; 2Yuanmou Desertification Ecosystem Research Station, State Forestry Administration, Kunming 650224, China)
  • Online:2014-07-18 Published:2014-07-18

Abstract: To ease the implementation of effective nutrient management for plantations with different vegetation restoration patterns and to assist in the selection of appropriate species and forestation patterns, nutrient (N, P, K, Ca and Mg) accumulation and cycling were investigated and compared in three plantations (10-year-old Azadirachta indica, Acacia auriculiformis and mixed A. indica-A. auriculiformis plantations) in Yuanmou Valley, a dry-hot valley of Yunnan Province, Southwestern China. The result showed that total nutrient accumulations were 333.05, 725.61 and 533.85 kg·hm-2 in pure plantations of A. indica and A. auriculiformis, and in A. indica-A. auriculiformis mixed plantation, respectively. The nutrient accumulation of various organs was ranked as branches > stems > roots > leaves > bark in the A. indica plantation and branches > stems > leaves > roots > bark both in the A. auriculiformis plantation and in the mixed plantation. Changes in accumulation of various nutrients in the mixed plantation were similar to that in the A. auriculiformis plantation (Ca > N > K > Mg > P), which were different from the A. indica plantation (Ca > K > N > Mg > P). Annual net nutrient accumulation, return and absorption in these plantations ranged from 62.72 to 162.19 kg·hm-2·a-1, 48.82 to 88.86 kg·hm-2·a-1 and 111.54 to 251.05 kg·hm-2·a-1, respectively, which were all the highest in the A. auriculiformis plantation, followed by the mixed plantation, and were the lowest in the A. indica plantation. The nutrient utilization coefficient, the cycling coefficient and the recycling period were estimated to be from 0.34 to 0.39, 0.35 to 0.44, and 6.54 to 8.17 a, respectively. The lower nutrient return and circulation rate of N or P in the A. indica plantation showed that this plantation had a poor ability to maintain soil fertility, while the highest nutrient circulation rate of N or P was observed in the A. auriculiformis plantation that displayed the advantage  in maintaining soil nutrients and stand productivity. The nutrient return and nutrient absorption in the mixed plantation were 167.2% and 186.2%, of those in the A. indica plantation, and the circulation rate of N, P and K were higher than those in the A. indica plantation, while the recycling period of Ca in mixed plantation was 50% shorter than that in A. auriculiformis plantation. Soil fertility and  nutrient supply were improved in the A. indica and A. auriculiformis mixed plantation.