Study On The Technique Of Balanced Pruning Of Root And Shoot In The Transplanting Of Betula Platyphylla

Betula platyphylla,with high value of landscape,is widely distributed around the north China.However,Betula platyphylla is limited severely in construction due to the immature transplanting technology.This research utilize the Betula platyphylla as experimental materials,by having four levels root pruning and shoot pruning respectively of Betula platyphylla,in order to study different effects of root pruning and shoot pruning with various degrees and explore the correlation between roots,photosynthesis and growth of Betula platyphylla.Finally,the pruning pattern of keeping root cap balance was selected.It is hoped that this research could provide a theoretical guidance to improve transplanting survival rate of Betula platyphylla and realize the efficient utilization of afforestation trees in China.The main conclusions are as follows:With the decrease of the transplanting size of root,the potential maximum photochemical efficiency Fv/Fm,PS ? quantum utilization efficiency Yield,photochemical quenching coefficient qP and electron transfer rate ETR all decreased,while accommodative energy dissipation Y(NPQ)and non regulated energy dissipation Y(NO)increased.Taking the 16 times of DBH root size as references,under the circumstance of 13 times,10 times and 7 times of DBH root size,Fv/Fm decreased by 1.4%,6.1%and 10.2%respectively;Yield decreased by 0.4%,21.5%and 44.4%respectively;qP decreased by 8.7%,18.8%and 24.3%respectively;ETR decreased by 7.6%,16.0%and 41.2%;Y(NPQ)increased by 0.1%,6.1%and 10.3%respectively;Y(NO)increased by 3.4%,7.7%and 14.4%respectively.With the increase of shoot pruning degree,taking the full crown as reference,Fv/Fm increased by 0.1%,0.3%and 0.2%respectively;Yield increased by 5.1%,11.2%,and 6.8%respectively;qP increased by 1.2%,5.9%and 2.2%respectively;ETR increased by 0.1%,5.9%and 2.6%respectively;Y(NPQ)decreased by 0.6%,3.7%and 2.9%respectively;Y(NO)decreased by 5.2%and 5.3%respectively with lightly and moderately shoot pruning,while increased by 1.7%with heavily shoot pruning.With the decrease of the transplanting size of root,the net photosynthetic rate Pn,the stomatal conductance Gs,the intercellular CO2 concentration Ci and the transpiration rate Tr decreased markedly.Taking the 16 times of DBH root size as reference,under the circumstance of 13 times,10 times and 7 times of DBH root size,Pn decreased by 15.7%,44.8%and 52.3%respectively;Gs decreased by 7.5%,44.0%and 58.9%respectively;Ci decreased by 5.6%,8.0%and 4.7%respectively;Tr decreased by 18.7%,38.1%and 45.3%respectively.With the increase of shoot pruning degree,taking the full crown as reference,Pn increased by 6.0%,13.1%and 7.1%respectively;Gs increased by 8.9%,34.9%and 13.2%respectively;Ci decreased by 5.6%and 5.9%respectively with lightly and heavily shoot pruning,while increased by 1.2%with moderately;Tr increased by 11.8%,19.3%and 16.4%respectively.With the decrease of the transplanting size of root,the DBH,the height increment,the area of a single leaf as well as the chlorophyll content all reduced markedly.Taking the 16 times of DBH root size as reference,under the circumstance of 13 times,10 times and 7 times of DBH root size,the DBH increment of Betula platyphylla decreased by 13.1%,45.0%,69.6%respectively;the height increment decreased by 38.5%,59.8%and 86.4%respectively;the area of a single leaf decreased by 4.7%,21.4%and 39.7%respectively;the chlorophyll content decreased by 7.5%,21.8%and 33.1%respectively.With the increase of shoot pruning degree,taking the full crown as reference,the DBH increment increased by 46.2%and 76.0%under the circumstance of lightly and moderately shoot pruning,while the DBH increment decreased by 17.9%with heavily shoot pruning;the height increment increased by 5.4%and 10.1%respectively with the lightly and moderately shoot pruning,decreased by 33.5%with heavily;the area of a single leaf increased by 51.3%,80.2%and 103.6%respectively;chlorophyll content increased by 1.3%,6.7%and 2.6%respectively.The transplanting size of root was 16 times of the DBH in the period of growing of Betula platyphylla in this research.The best effect appeared when the moderately shoot pruning was adopted.