Actual and potential transpiration and carbon assimilation in an irrigated poplar plantation
Actual and potential transpiration and carbon assimilation in an irrigated poplar plantation
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DOI：
10.1093/treephys/28.4.559
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发表时间：
2008-04-01
期刊：
影响因子：
4
通讯作者：
Hinckley, Thomas M.
中科院分区：
文献类型：
--
作者：
Kim, Hyun-Seok;Oren, Ram;Hinckley, Thomas M.
我们研究了林分水平用水和碳吸收之间的权衡，结果时，在种植园树木的生物量生产最大化，通过去除养分和水的限制。一棵大叶杨x三角叶矮牵牛P deltoides Bartr. & Marsh。种植园得到灌溉，并接受频繁的营养补充，以优化生物量生产。树液流量密度连续测量超过四个生长季节的六个月，补充定期测量叶气体交换和水势。测量树的直径和高度被用来估计叶面积和生物量生产的异速生长关系的基础上。树干液流被转换为冠层电导率，并与经验模型进行分析，以隔离水分限制的影响。实际和土壤-水联合的潜在的CO，吸收估计冠层电导约束的碳同化（4C-A）计划，耦合实际或潜在的冠层电导与垂直梯度的光分布，叶水平电导，最大Rubisco容量和最大电子传递。净初级生产力（NPP）约为初级生产总值（GPP）的43%;当对个体树木进行估计时，这个比例与树木大小无关。根据NPP/GPP比率，我们发现与没有水分限制的生长相比，当前灌溉使生长减少了约18%。然而，要达到最大的生长，需要70%以上的蒸腾用水，并将减少27%的水分利用效率，从1.57至1.15克干木每公斤（-1）水。鉴于水的经济和社会价值，种植园管理者似乎已经优化了水的利用。
We examined the tradeoffs between stand-level water use and carbon uptake that result when biomass production of trees in plantations is maximized by removing nutrient and water limitations. A Populus trichocarpa Torr. x P deltoides Bartr. & Marsh. plantation was irrigated and received frequent additions of nutrients to optimize biomass production. Sap flux density was measured continuously over four of the six growing-season months, supplemented with periodic measurements of leaf gas exchange and water potential. Measurements of tree diameter and height were used to estimate leaf area and biomass production based on allometric relationships. Sap flux was converted to canopy conductance and analyzed with an empirical model to isolate the effects of water limitation. Actual and soil-water-united potential CO, uptakes were estimated with a canopy conductance constrained carbon assimilation (4C-A) scheme, which couples actual or potential canopy conductance with vertical gradients of light distribution, leaf-level conductance, maximum Rubisco capacity and maximum electron transport. Net primary production (NPP) was about 43% of gross primary production (GPP); when estimated for individual trees, this ratio was independent of tree size. Based on the NPP/GPP ratio, we found that current irrigation reduced growth by about 18% compared with growth with no water limitation. To achieve maximum growth, however, would require 70% more water for transpiration, and would reduce water-use efficiency by 27%, from 1.57 to 1.15 g stem wood C kg(-1) water. Given the economic and social values of water, plantation managers appear to have optimized water use.