Pensa Margus, Jalkanen Risto
Rovaniemi Research Station, Finnish Forest Research Institute, P.O. Box 16, Rovaniemi FIN-96301, Finland.
Tree Physiol. 2005 Oct;25(10):1265-71. doi: 10.1093/treephys/25.10.1265.
Latitudinal variation in needle longevity of conifers in response to climatic variability is a well-known phenomenon, but its significance has only rarely been studied. Scots pine (Pinus sylvestris L.) stands were investigated in four locations in Lapland (northern Finland and northern Sweden, 67-68 degrees N) and in four locations in Estonia (59 degrees N) to test the hypothesis that plasticity in needle longevity results in similar needle biomass per foliated shoot length across latitudes. The needle-trace method (NTM) revealed the dynamics of needle fascicles attached to stem shoots. Long-term mean needle age was 2 years greater in Lapland than in Estonia. In both regions, mean needle age was strongly and negatively related to yearly needle-fascicle production rate relative to the number of needles on the same shoot axis. Although significantly fewer needle-fascicles were produced annually in trees in Lapland than in Estonia, the overall number of fascicles attached to the stem shoots, needle-fascicle density and individual needle dry mass did not differ between regions. Consequently, needle biomass per foliated shoot length was similar in trees in both regions. Thus, our results support the theory that plasticity in needle longevity helps Scots pine to compensate for reduced needle production so that the same foliar biomass per shoot is retained under a wide range of growth conditions.
针叶树针叶寿命随气候变异性的纬度变化是一个众所周知的现象，但其重要性却很少被研究。在拉普兰（芬兰北部和瑞典北部，北纬67 - 68度）的四个地点以及爱沙尼亚（北纬59度）的四个地点对苏格兰松（Pinus sylvestris L.）林分进行了调查，以检验以下假设：针叶寿命的可塑性导致不同纬度上单位叶生枝长度的针叶生物量相似。针叶痕迹法（NTM）揭示了附着在茎枝上的针叶束的动态变化。拉普兰的长期平均针叶年龄比爱沙尼亚大2岁。在两个地区，平均针叶年龄与相对于同一枝轴上针叶数量的年针叶束产生率均呈强烈负相关。尽管拉普兰树木每年产生的针叶束明显少于爱沙尼亚，但附着在茎枝上的针叶束总数、针叶束密度和单叶干质量在两个地区之间并无差异。因此，两个地区树木的单位叶生枝长度的针叶生物量相似。所以，我们的结果支持了这样一种理论，即针叶寿命的可塑性有助于苏格兰松弥补针叶产量的降低，从而在广泛的生长条件下保持相同的单枝叶生物量。
