Photosynthetic capacity increases in Acacia melanoxylon following form pruning in a two-species plantation
Photosynthetic capacity increases in Acacia melanoxylon following form pruning in a two-species plantation
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DOI：
10.1016/j.foreco.2006.05.016
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发表时间：
2006-09
影响因子：
3.7
通讯作者：
J. Medhurst;E. Pinkard;C. Beadle;D. Worledge
中科院分区：
文献类型：
--
作者：
J. Medhurst;E. Pinkard;C. Beadle;D. Worledge
在种植有辐射松护理作物的 5 年生金合欢种植园中，研究了修剪对部分落叶的光合作用反应。形状修剪，即去除大树枝或竞争性主干，用于去除整个树冠中 25% 或 50% 的树叶，并比较与未修剪树木的反应。在 12 个月的时间内定期测量光合能力，以光饱和光合速率 (Amax) 表示。修剪后 2 至 6 周内观察到叶状植物光合能力的增加，并且 50% 修剪处理中增加的幅度更大。光合能力的增加仅限于树冠的上部三分之二。虽然最大气孔导度 (gs) 值在 50% 修剪后通常更大，但修剪引起的光合水分利用效率 (WUE) (Amax/gs) 没有变化。修剪处理不会改变叶面养分水平。 Amax的变化与叶状磷含量呈强相关，与叶状氮含量呈弱相关。水分利用效率、叶状养分含量和光合效率没有相应的变化，表明观察到的光合能力的增加是由碳源：库比的变化驱动的。仅从树冠上游除去叶子的修剪可能会降低树冠光合作用增强的总体程度，并对黑木木 A. melanoxylon 的生长产生最大的负面影响。
The photosynthetic responses to partial defoliation through pruning were examined in a 5-year-old Acacia melanoxylon plantation grown with a Pinus radiata nurse crop. Form pruning, the removal of large branches or competing leaders, was used to remove either 25 or 50% of tree foliage from throughout individual tree crowns and compare responses to unpruned trees. Photosynthetic capacity, expressed as light-saturated photosynthetic rate (Amax), was measured periodically over a 12-month period. An increase in photosynthetic capacity of phyllodes was observed between 2 and 6 weeks after pruning and the magnitude of the increase was greater in the 50% pruning treatment. The increase in photosynthetic capacity was confined to the upper two-thirds of the crown. While maximum stomatal conductance (gs) values were generally greater following 50% pruning, there were no pruning-induced changes in photosynthetic water-use efficiency (WUE) (Amax/gs). Foliar nutrient levels were not altered by pruning treatment. Changes in Amaxwere strongly correlated with phyllode phosphorus content and only weakly correlated with phyllode nitrogen content. The absence of corresponding changes in water-use efficiency, phyllode nutrient content and photosynthetic efficiency suggests that the observed increases in photosynthetic capacity were driven by changes in the carbon source:sink ratio. Form pruning that removes foliage solely from the upper reaches of the crown is likely to reduce the overall magnitude of photosynthetic enhancement in the crown and have the greatest negative effect on the growth of A. melanoxylon.