Reich Peter B, Rich Roy L, Lu Xingjie, Wang Ying-Ping, Oleksyn Jacek
Department of Forest Resources, University of Minnesota, St. Paul, MN 55108; Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW 2751, Australia;
Department of Forest Resources, University of Minnesota, St. Paul, MN 55108;
Proc Natl Acad Sci U S A. 2014 Sep 23;111(38):13703-8. doi: 10.1073/pnas.1216054110. Epub 2014 Sep 15.
Leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. We hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. This hypothesis was supported, because across 127 sites along a 2,160-km gradient in North America individuals of Picea glauca, Picea mariana, Pinus banksiana, and Abies balsamea had longer needle life span and lower tissue nitrogen concentration with decreasing mean annual temperature. Similar patterns were noted for Pinus sylvestris across a north-south gradient in Europe. These differences highlight needle longevity as an adaptive feature important to ecological success of boreal conifers across broad climatic ranges. Additionally, differences in leaf life span directly affect annual foliage turnover rate, which along with needle physiology partially regulates carbon cycling through effects on gross primary production and net canopy carbon export. However, most, if not all, global land surface models parameterize needle longevity of boreal evergreen forests as if it were a constant. We incorporated temperature-dependent needle longevity and %nitrogen, and biomass allocation, into a land surface model, Community Atmosphere Biosphere Land Exchange, to assess their impacts on carbon cycling processes. Incorporating realistic parameterization of these variables improved predictions of canopy leaf area index and gross primary production compared with observations from flux sites. Finally, increasingly low foliage turnover and biomass fraction toward the cold far north indicate that a surprisingly small fraction of new biomass is allocated to foliage under such conditions.
叶寿命是一种重要的植物性状，与叶、生物体和生态系统过程中的种间变异相关。我们假设裸子植物针叶性状随纬度的种内变异反映了对适应相关温度和水分梯度的性状的选择和适应。这一假设得到了支持，因为在北美沿着2160公里梯度的127个地点，白云杉、黑云杉、班克松和香脂冷杉的个体随着年平均温度的降低，针叶寿命更长，组织氮浓度更低。在欧洲，欧洲赤松沿南北梯度也观察到了类似的模式。这些差异突出了针叶寿命作为一种适应性特征，对广泛气候范围内北方针叶树的生态成功至关重要。此外，叶寿命的差异直接影响年叶更新率，年叶更新率与针叶生理一起通过对总初级生产力和冠层净碳输出的影响，部分调节碳循环。然而，即使不是全部，大多数全球陆地表面模型都将北方常绿森林的针叶寿命参数化为一个常数。我们将温度依赖的针叶寿命、氮含量百分比和生物量分配纳入陆地表面模型“社区大气生物圈土地交换”，以评估它们对碳循环过程的影响。与通量站点的观测结果相比，纳入这些变量的实际参数化改进了冠层叶面积指数和总初级生产力的预测。最后，在寒冷的极北地区，叶更新率和生物量比例越来越低，这表明在这种条件下，分配给叶的新生物量比例小得出奇。
