Cordell S, Goldstein G, Meinzer F C, Vitousek P M
Department of Botany, University of Hawaii, Honolulu 96822, USA.
Tree Physiol. 2001 Jan;21(1):43-50. doi: 10.1093/treephys/21.1.43.
Leaf-level studies of Metrosideros polymorpha Gaud. (Myrtaceae) canopy trees at both ends of a substrate age gradient in the Hawaiian Islands pointed to differential patterns of adjustment to both nutrient limitation and removal of this limitation by long-term (8-14 years) nitrogen (N), phosphorus (P) and N + P fertilizations. The two study sites were located at the same elevation, had similar annual precipitation, and supported forests dominated by M. polymorpha, but differed in the age of the underlying volcanic substrate, and in soil nutrient availability, with relatively low N at the young site (300 years, Thurston, Hawaii) and relatively low P at the oldest site (4,100,000 years, Kokee, Kauai). Within each site, responses to N and P fertilization were similar, regardless of the difference in soil N and P availability between sites. At the young substrate site, nutrient addition led to a larger mean leaf size (about 7.4 versus 4.8 cm2), resulting in a larger canopy leaf surface area. Differences in foliar N and P content, chlorophyll concentrations and carboxylation capacity between the fertilized and control plots were small. At the old substrate site, nutrient addition led to an increase in photosynthetic rate per unit leaf surface area from 4.5 to 7.6 micromol m(-2) s(-1), without a concomitant change in leaf size. At this site, leaves had substantially greater nutrient concentrations, chlorophyll content and carboxylation capacity in the fertilized plots than in the control plots. These contrasting acclimation responses to fertilization at the young and old sites led to significant increases in total carbon gain of M. polymorpha canopy trees at both sites. At the young substrate site, acclimation to fertilization was morphological, resulting in larger leaves, whereas at the old substrate site, physiological acclimation resulted in higher leaf carboxylation capacity and chlorophyll content.
对夏威夷群岛底物年龄梯度两端的多花铁心木（桃金娘科）冠层树木进行的叶级研究表明，长期（8 - 14年）施加氮（N）、磷（P）和N + P肥料后，树木对养分限制及这种限制解除的调整模式存在差异。两个研究地点海拔相同，年降水量相似，且均以多花铁心木为主的森林，但底层火山底物的年龄以及土壤养分有效性不同，年轻地点（夏威夷瑟斯顿，300年）土壤氮含量相对较低，而最古老地点（考艾岛科基，410万年）土壤磷含量相对较低。在每个地点内，无论地点间土壤氮和磷有效性存在差异，对氮和磷施肥的响应都是相似的。在年轻底物地点，添加养分导致平均叶面积增大（约7.4平方厘米对4.8平方厘米），从而使冠层叶表面积增大。施肥区和对照区之间叶片氮和磷含量、叶绿素浓度及羧化能力的差异较小。在古老底物地点，添加养分使单位叶面积光合速率从4.5微摩尔·米⁻²·秒⁻¹增加到7.6微摩尔·米⁻²·秒⁻¹，而叶面积没有相应变化。在该地点，施肥区叶片的养分浓度、叶绿素含量和羧化能力明显高于对照区。年轻和古老地点对施肥的这些不同适应响应导致两个地点多花铁心木冠层树木的总碳增益显著增加。在年轻底物地点，对施肥的适应是形态学上的，导致叶片更大，而在古老底物地点，生理适应导致叶片羧化能力和叶绿素含量更高。
