遮荫对水曲柳和蒙古栎光合、生长和生物量分配的影响

为探讨水曲柳(Fraxinus mandshurica)和蒙古栎(Quercus mongolica)苗期对光的适应性及其生长最适光强,设置4种光环境(全光(FL)、75%光(LS)、50%光(MS)、25%光(HS)),观测了2年生水曲柳和蒙古栎苗木气体交换参数、叶绿素含量(Chl)和比叶重(LMA)、生长及生物量的分配。结果表明:随着光强的减弱,2个树种的LMA、单位叶鲜质量(LFA)和根冠比均呈下降趋势;叶绿素含量(Chl)呈上升趋势,且差异显著(p<0.05);光补偿点(LCP)和暗呼吸速率(Rd)呈"N"形变化,但差异均不显著(p>0.05);水曲柳的最大光合速率(Pmax)在HS处理下最大,Rd在HS处理下最小;蒙古栎的最大光合速率(Pmax)在LS处理下最大,Rd也较小;在全光处理下苗高增量均低于HS处理,地径增量均高于HS处理。研究结果进一步确定水曲柳苗期具有一定的耐荫性,在弱光强下生长较好;蒙古栎苗期对光照要求较高,在相对较强光照下生长较好。

Effects of Shading on the Photosynthetic Characteristics,Growth,and Biomass Allocation in Fraxinus mandshurica and Quercus mongolica

In order to explore the acclimation of Fraxinus mandshurica and Quercus mongolica to light regimes and the optimal light for growth,2-year-old F.mandshurica and Q.mongolica were cultivated under four light intensity regimes(100%,75%,50% and 25% of full light,which were termed as FL,LS,MS and HS,respectively).The parameters of gas exchange,chlorophyll content(Chl),leaf mass per unit area,growth,and biomass allocation were determined during the growth season.The results showed that leaf dry mass per unit leaf area(LMA),leaf fresh mass per unit leaf area(LFA),root/shoot ratio of these two species were decreased along with the decreasing irradiance;Chlorophyll content(Chl) was increased(p<0.05) with the decreasing irradiance;Light compensation point(LCP) and dark respiration rate(Rd) were in a "N" form change,but the differences are not significant(p>0.05);F.mandshurica had the greatest Pmax and the smallest Rd under HS,Q.mongolica had the greatest Pmax and small Rd under LS;Height growth of full light treatment was lower than that of the HS for these two species,basal diameter growth of full light treatment was higher than that of the HS.The results suggested that F.mandshurica was moderately shade-tolerant at the seedling stage,and the growth was better under the low light intensity;The requirement of Q.mongolica to light is higher and growth was better under relatively high light intensity.