Physioecology Research Of Betula Ermanii On Changbai Mountain

To study the ecophysiological mechanisms in environment adaptation of Betula ermanii in Changbai Mountain,a National Natural Reserve in Southeastern China,we studied the specific leaf area(SLA),content of Chla,Chlb and Chl(a+b), malondialdehyde(MDA),the membrane permeability(MP),and the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and ascorbate peroxidase(APX) in leaves of B.ermanii from different altitudes(A1:1700 m,A2:1800 m,A3:1900 m,A4:2000 m and A5:2050 m) in Changbai Mountain.The results showed that SLA decreased with increasing altitude;Chla,Chlb and Chl(a+b) reduced with increasing altitude,At A5,they decreased 15.03%,24.55%and 17.23%,respectively, compared with that in A1.As taking the north lope of Changbai Mountain as sampling sites,the investigation of the tissue non-structural carbohydrates(NSC) content of B.ermanii at the positions from lower elevations to timberline during the periods of vigorous growth indicated that the overall altitudinal trends of NSC in the B.ermanii revealed no depletion of carbon reserves near the tree limit,suggesting that sink limitation predominates woody plant life across this timberline ecotone community.The results also suggest that the stronger frost resistance of the plants located at a timberline altitude are associated with their stronger synthesis of the carbohydrates.MP and content of MDA reach minimum values in A3 and maximum in A5, indicating that B.ermanii was least damaged in A3 and most in A5.The activities of SOD, POD,CAT and APX in B.ermanii leaves had the same change pattern along the altitudinal gradient,they were all the weakest in A3,relatively lower at middle altitude (1900 m) and relatively higher at lower(1700-1800 m) and higher altitudes(2000-2050 m),but decreased at the altitude near the upper limit of forest vertical distribution.In general,1900 m is the best for the growth of B.ermanii,while above altitude 2000 m is the poorest.