Environmental and physiological control of needle conductance for bare-root black spruce, white spruce, and jack pine seedlings on boreal cutover sites

摘要

A study was conducted to examine the influence of environmental conditions of boreal cutover sites on plant water status and needle conductance of newly planted bare-root black spruce (Picea mariana(Mill.) B.S.P.), white spruce (Picea glauca(Moench) Voss.), and jack pine (Pinus banksianaLamb.) seedlings. As absolute humidity deficit between the needles and air (AHD) increased, xylem pressure potentials (psi;x) became most negative in black spruce, intermediate in white spruce, and least negative in jack pine seedlings. Needle conductance (gwv) was strongly related to AHD in all three species, with increasing AHD resulting in a decrease ingwv. However, at low levels of AHD,gwvvalues for black and white spruce seedlings were approximately 50 and 25 higher, respectively, than those for jack pine seedlings. For black and white spruce seedlings,gwvdecreased as psi;xbecame more negative, while jack pinegwvresponded to more negative psi;xwith a threshold for stomatal closure at approximately minus;1.7ensp;MPa. In all three species, increasing photosynthetically active radiation (PAR) resulted in greatergwvat all AHD levels. However, at high AHD levels,gwv, response to PAR was suppressed. The findings of this study indicate species differences in physiological response to atmospheric conditions under nonlimiting soil moisture conditions. The implications for successful reforestation are discussed.