土壤水分胁迫对树木N2O排放速率的影响

采用封闭罩-气相色谱法观测研究了干旱胁迫对长白山阔叶红松林的几种优势树种-红松(Pinus koraiensis)、水曲柳(Fraxinus mandshurica)、胡桃楸(Juglans mandshurica)、椴树(Tilia amurensis)和蒙古栎(Quercus mongolica)叶片N2O排放。并同步测定5种树木叶片净光合速率、呼吸速率和气孔导度。结果表明：土壤水分胁迫明显降低树木叶片气孔导度、净光合速率和N2O排放速率，叶片气孔是树木N2O排放的主要通道。树木N2O排放以白天为主，在相同的水分条件下，不同的苗木有不同的N2O排放速率，同种苗木的N2O排放随干旱胁迫的加重而减少，在受到不同干旱胁迫时，针叶树红松N2O的排放速率降至正常水分条件下的34.43％和100．6％、阔叶树种N2O排放平均降至31．93％和86.35％。不同干旱胁迫的红松、水曲柳、胡逃楸、椴树和蒙古栎幼树叶片N2O排放速率为34．43、14．44、33．02、16.48和32．33ngN2O．g^-1DW．h^-1。图1表1参12。

Effect of water stress on N2O emission rate of 5 tree species

The N2O emission rates, photosynthesis, respiration and stomatal conductance of the dominant tree species from broadleaf/Korean pine forest in Changbai Mountain were measured by simulated water stress with the closed bag-gas chro-matography. A total of five species seedlings were involved in this study, i.e., Pinus koraiensis Sieb. et Zucc, Fraxinus mand-shurica Rupr, Juglans mandshurica Maxim, Tilia amurensis Rupr, and Quercus mongolica Fisch. ex Turcz.. The results showed that the stomatal conductance, net photosynthetic rate and N2O emission of leaves were significantly reduced under the water stress. The stoma in the leaves of trees is the main pathway of N2O emission. N2O emission in the trees mainly occurred during daytime. N2O emission rates were different in various tree specie seedlings at the same water status. In the same tree species, N2O emission rates decreased as the reduction of soil water contents. At different soil water contents (MW, LW) the N2O emis-sion rates of Pinus koraiensis decreased by 34.43% and 100.6% of those in normal water condition, respectively. In broadleaf arbor decreased by 31.93% and 86.35%, respectively. Under different water stresses N2O emission rates in five tree species such as Pinus koraiensis, Fraxinus mandshurica, Juglans mandshurica, Tilia amurensis, and Quercus mongolica were 38.22, 14.44, 33.02, 16.48 and 32.33 ngN2Og-1DWh-1, respectively.