Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, D-07745 Jena, Germany.
Tree Physiol. 2010 Jun;30(6):689-704. doi: 10.1093/treephys/tpq027. Epub 2010 May 7.
The periodic production of large seed crops by trees (masting) and its interaction with stem growth has long been the objective of tree physiology research. However, very little is known about the effects of masting on stem growth and total net primary productivity (NPP) at the stand scale. This study was conducted in an old-growth, mixed deciduous forest dominated by Fagus sylvatica (L.) and covers the period from 2003 to 2007, which comprised wet, dry and regular years as well as two masts of Fagus and one mast of the co-dominant tree species Fraxinus excelsior (L.) and Acer pseudoplatanus (L.). We combined analyses of weather conditions and stem growth at the tree level (inter- and intra-annual) with fruit, stem and leaf production, and estimates of total NPP at the stand level. Finally, we compared the annual demand of carbon for biomass production with net canopy assimilation (NCA), derived from eddy covariance flux measurements, chamber measurements and modelling. Annual stem growth of Fagus was most favoured by warm periods in spring and that of Fraxinus by high precipitation in June. For stem growth of Acer and for fruit production, no significant relationships with mean weather conditions were found. Intra-annual stem growth of all species was strongly reduced when the relative plant-available water in soil dropped below a threshold of about 60% between May and July. The inter-annual variations of NCA, total NPP and leaf NPP at the stand level were low (mean values 1313, 662 and 168 g C m(-2) year(-1), respectively), while wood and fruit production varied more and contrarily (wood: 169-241 g C m(-2) year(-1); fruits: 21-142 g C m(-2) year(-1)). In all years, an annual surplus of newly assimilated carbon was calculated (on average 100 g C m(-2) year(-1)). The results suggest that stem growth is generally not limited by insufficient carbon resources; only in mast years a short-term carbon shortage may occur in spring. In contrast to common assumption, stem growth alone is not a sufficient proxy for total biomass production or the control of carbon sequestration by weather extremes.
树木的周期性大种子作物生产（结实）及其与茎生长的相互作用一直是树木生理学研究的目标。然而，对于结实对茎生长和总净初级生产力（NPP）的影响，在林分尺度上知之甚少。本研究在一个以欧洲山毛榉（Fagus sylvatica (L.)）为主的古老、混合落叶林中进行，研究时间为 2003 年至 2007 年，包括湿润、干燥和正常年份，以及欧洲山毛榉的两次结实和优势树种白蜡（Fraxinus excelsior (L.)）和挪威槭（Acer pseudoplatanus (L.)）的一次结实。我们将树木水平上的天气条件和茎生长分析（年内和年际）与果实、茎和叶的产量以及林分水平上的总 NPP 估算相结合。最后，我们将每年用于生物量生产的碳需求与通过涡度相关通量测量、室测量和建模得出的净冠层同化（NCA）进行了比较。欧洲山毛榉的年茎生长最有利于春季温暖期，白蜡的年茎生长最有利于 6 月的高降水。对于挪威槭和果实的年茎生长，没有发现与平均天气条件的显著关系。当 5 月至 7 月期间土壤中植物可利用水的相对值降至约 60%以下时，所有物种的年内茎生长都会急剧减少。林分水平上的 NCA、总 NPP 和叶 NPP 的年际变化很小（平均值分别为 1313、662 和 168 g C m(-2) year(-1)），而木材和果实的产量变化更大且相反（木材：169-241 g C m(-2) year(-1)；果实：21-142 g C m(-2) year(-1)）。在所有年份中，都计算出了新同化碳的年盈余（平均为 100 g C m(-2) year(-1)）。结果表明，茎生长通常不受碳资源不足的限制；只有在结实年，春季可能会出现短期的碳短缺。与常见的假设相反，单独的茎生长并不是总生物量生产或控制天气极端条件下碳封存的充分替代物。
