JOURNAL OF NANJING FORESTRY UNIVERSITY ›› 2018, Vol. 42 ›› Issue (05): 53-58.doi: 10.3969/j.issn.1000-2006.201708003

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A study on new and old branch's leaf photosynthetic capacity and water use efficiency of natural Larix gmelinii forest in the northern Great Xing'an Mountains

SONG Hao, MAN Xiuling*, DUAN Beixing, LIU Jialing   

  1. College of Forestry, Northeast Forestry University,Harbin 150040, China
  • Online:2018-09-15 Published:2018-09-15

Abstract: 【Objective】Larix gmelinii is the climax vegetation in the northern Great Xing'an Mountains. The pronounced differences between new and old branches may cause significant variations of photosynthetic capacity and water use efficiency. Exploring the difference of photosynthetic capacity between new branch and old branch and the response of photosynthetic capacity of L. gmelinii can definitely help to accurately estimate the photosynthetic capacity and water use efficiency of the climax vegetation in Great Xing'an Mountains.【Method】The leaf photosynthetic capacity(Pn,max), transpiration rate(Tr)and water use efficiency(CWUE)of the new and old branches of different differentiation grade L. gmelinii were examined in the study site of Mohe Forest Ecosystem Research Station from June to September in 2016.【Results】The results showed that the average Pn,max of new and old branches were 5.654 and 3.248 μmol/(m2·s), The average Tr were 1.291 and 0.779 μmol/(m2·s)respectively. The Pn,max and Tr of new branch were 74.1% and 65.7% higher than those of the old branch. The CWUE of new branch was 6.61% higher than that of the old branch with the average values of 5.077 and 4.762 μmol/mmol, respectively. 【Conclusion】The analysis indicated that the differences of Pn,max and Tr between new and old branches were significant(P<0.01). The difference of average CWUE between new and old branches was not statistically significant(P>0.05), although the CWUE in June was significantly(P<0.01)different from those in the other months. Thus, we concluded that the Pn,max and Tr of L. gmelinii between new and old branches exhibited great differences, while the difference of CWUE was much small.

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