福建长汀重建植被马尾松与木荷光合特性比较

比较了福建长汀水土流失区重建植被措施治理后,2个不同恢复程度生境中的马尾松(Pinus massoniana)与木荷(Schima superba)光合特性季节变化及日进程,结果表明:(1)马尾松净光合速率(Pn)具有明显的季节变化特征,其中恢复程度较低生境(样地Ⅰ)马尾松Pn最大值出现在秋季,恢复程度较高生境(样地Ⅱ)马尾松Pn春季最大,秋季次之;样地Ⅱ马尾松Pn日均值冬季显著低于样地Ⅰ(P<0.05),春季极显著高于样地Ⅰ(P<0.01),反映出样地Ⅱ马尾松抵御低温胁迫的能力强于样地Ⅰ马尾松.(2)样地Ⅰ和样地Ⅱ木荷Pn季节变化趋势一致,最大值均出现在夏季,且样地Ⅱ木荷Pn高于样地Ⅰ;此外,样地Ⅱ木荷Pn秋季仍维持在较高水平.说明重建植被措施治理后,木荷在恢复程度较高生境中生长良好.(3)根据气孔导度、胞间CO2浓度和气孔限制值的变化方向判断,夏季和秋季样地Ⅰ马尾松与木荷Pn主要受气孔因素影响,8:00后呈缓慢下降趋势,显示在长期较为恶劣的生境条件下,马尾松与木荷已形成一种趋同的生理生态适应机制,即通过气孔调节限制蒸腾失水,但这种适应是以降低光合速率为代价的,这也是样地Ⅰ马尾松与木荷生长缓慢的一个重要原因.(4)同一生境,木荷Pn与蒸腾速率(Tr)均明显高于马尾松,尤其样地Ⅱ2树种间的差异更显著,表明重建植被措施实施后,生态恢复程度较高生境中,木荷生长、竞争优势强于马尾松.

Comparison on photosynthetic characteristics between Pinus massoniana and Schima superba at the two different rehabilitation vegetation, Changting County, Fujian Province

The seasonal variation and daily dynamics of photosynthesis of Pinus massoniana and Schima superba were compared at the two different ecological restoration stages in the soil erosion area, Changting County, Fujian Province. The results showed that the net photosynthetic rate (P_n) of P. Massoniana displayed variations in seasonal pattern with a peak in October at the initial restoration stage (plot Ⅰ) and two peaks at the subsequent restoration stage (plotⅡ), the higher one in April and the lower one in October. Moreover, the mean P_n in winter for P. Massoniana was significantly lower in plotⅡ than in plot I (P<0.05), while it reversed in April (P<0.01), indicating higher cold tolerance of P. Massoniana in plot II than in plot I. In addition, there was a similar seasonal dynamics of P_n for S. Superba both in plot Ⅰ and plotⅡ, with a peak in July. However, the P_n in plot II was higher than in plot Ⅰ, which still remained high in October, implying that S. Superba in plotⅡgrew better after ecological recovery. Based on the variations in stomata conductance, intercellular CO_2 concentration and stomata limitation, it was suggested that the slow decrease of P_n after 8:00 a.m. In P. Massoniana and S. Superba in July and October was closely related to the stomata. This result indicated there was convergent adaptation between these two species under the extreme stress,I.e., limiting evaporation by stomata adjustment, which would lead to the decease in photosynthesis as well. This decrease mainly accounted for the slow growth for the both species in plot Ⅰ. The transpiration rate (T_r) and P_n of S. Superba were higher than those of P. Massoniana both in plot Ⅰ and plotⅡ, particularly in plotⅡ, suggesting that S. Superba may be more competitive than P. Massoniana during the ecological restoration.