Alpine Ecosystem Observation and Experiment Station of Gongga Mountain, Institute of Mountain Hazard and Environment, Chinese Academy of Sciences, Chengdu, China.
PLoS One. 2012;7(3):e34213. doi: 10.1371/journal.pone.0034213. Epub 2012 Mar 30.
Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.
许多研究试图解释高山林线现象的生理机制，但由于不同研究得出的结果相反，关于高山林线形成的争论仍然存在争议。本研究探讨了一种生长在其海拔上限的高山灌木物种（Quercus aquifolioides）的碳生理学，与较低海拔相比，以测试高山灌木（<3 米高）的海拔上限是否由碳限制或生长限制决定。我们研究了在中国西南部哲多山海拔 3000 米、3500 米和海拔上限 3950 米处生长的 Q. aquifolioides 的非结构性碳水化合物（NSC）及其库大小的季节性变化。沿着海拔梯度的组织 NSC 浓度随季节变化显著，反映了季节性的碳平衡。组织中的 NSC 水平在生长季节初期最低，表明植物利用冬季储备储存物来促进早春的重新生长。在生长季节，海拔上限处生长的植物的 NSC 浓度并不比较低海拔处的植物低，但在冬季，储存组织，特别是根，在海拔上限处的植物中的 NSC 浓度明显低于较低海拔处的植物。本研究结果表明冬季储备在储存组织中的重要性，这可能决定了 Q. aquifolioides 灌木在高海拔地区冬季的生存和早春的重新生长，从而形成了最高分布极限。这一结果与高山林线形成的最新假说一致。
