两种连作模式下杨树苗木的气体交换及其生物量分配

Gas exchange and biomass distribution of poplar cuttings(I-107,Populus×Euramercana ‘Neva')under two continuous cropping types

以I-107杨为试材,采取当年扦插(A)和留根截干(B)两种不同的连作模式,研究两种不同连作方式下杨树苗木的气体交换及生物量分配。结果表明:A模式下,光合速率(Pn)、蒸腾速率(E)及气孔导度(Gs)均随连作代数的增加而降低,水分利用效率(WUE)则相反.B模式下,Pn和WUE随着连作代数的增加而降低,E相反,而Gs则先增加后降低。其中,A模式下1代、2代苗木的Pn、E及Gs均大于B模式;随着连作代数的增加,两种不同连作方式下的苗高、胸径及单株生物量均呈现下降趋势。其中,B连作模式下的苗高、胸径及单株生物量均高于同代的A连作模式;两种连作方式下的叶绿素a、b含量及叶绿素总量均随连作代数增加而降低。其中,A模式下苗木的叶绿素a、b含量及叶绿素总量高于B模式;随着连作代数的增加,A、B两种连作方式下根、茎部分生物量均降低,但两种连作模式下各部分生物量所占比例的变化趋势相反。其中,B连作模式下苗木的根、茎生物量明显高于A模式。

Gas exchange and biomass distribution of I--107 （Populus X Euramercana ＇ Neva＇） poplar cutting under two continuous cropping types （A represent one year cutting;B represent two years cutting shoot and one year cutting trunk） were studied. Result showed that, under A type, photosynthesis rate （Pn）, transpiration rate （E） and stomatal conductance （G,） decreased with generation increased, but water use efficiency （WUE） increased. Under B type, Pnand WUE decreased with generation increased, but E increased, Gs increased firstly, then decreased. Therein, Pn.E and Gs of 1st and 2nd generations under A type were higher than B type;As continuous generation increased, height （H）, diameter at breast height （DBH） and total biomass under the two types both decreased. Therein, H, DBH and biomass of poplar cuttings under B type were higher than A type in the same generation;Under two types, the chlorophyll a （chl Ⅱ a） content, chlorophyll b （chl Ⅱ b） content and total chlorophyll （chl Ⅱ ） content decreased with generation increased. Therein, the three parameters under A type were higher than B type; As the generation increased, root biomass and stem biomass of poplar cuttings under A and B types both decreased, but variation of the ratio of each part biomass under the two types showed the reverse trend. Therein, root biomass and stem biomass of poplar cuttings under B type were higher than A type.