快速升温对东北地区樟子松生长响应差异的影响研究

Global climate warming influenced the forest distribution dynamics in the middle to high latitude of Northern Hemisphere. Pinus sylvestris is a dominant species in Northeast forest. The rapid warming trend in northeast China in recent years made the Pinus sylvestris forest located at the southernmost of the local distribution shrink, while the radial growth of Pinus sylvestris was benefit from the temperature increment in the northern region. Thus, the influence of rapid warming on distribution dynamics of Northeast forest was depended on regions. Predicting the regional divergences of future distribution dynamics of Pinus sylvestris forest in the context of rapid warming has significant meanings for maintaining the regional ecological and environmental security. In this study, based on the dendrochronology, forest ecology, stable.isotope and simulated experiments, the main dominant species in northeast China - Pinus sylvestris was used to study the regional divergence response of the radial growth of Pinus sylvestris to rapid climate warming, investigate the dynamics of suitable growth regions under the background of rapid warming, reveal the water demand divergence in different responsive regions, simulate the forest distribution dynamics in the context of future continued warming. Our results could improve our ability for the prediction of Pinus sylvestris forest distribution dynamics in the context of rapid warming, and provide the scientific basis and data supply for the reasonable forest protect planning in the northeast China.

全球气候变暖深刻影响着北半球中高纬度的森林分布动态。樟子松是我国东北森林主要的优势树种。近年来，东北地区气候的快速变暖使得东北南端的天然樟子松林呈现出萎缩趋势；而气候变暖可以促进东北北部樟子松的径向生长。因此，快速变暖对东北森林分布动态的影响存在区域差异。预测不同区域的天然樟子松林在快速变暖背景下的分布变动趋势差异对于维护区域生态及环境安全具有重要的意义。本研究拟以东北地区主要的建群种樟子松为研究对象，基于树木年轮学、森林生态学、稳定同位素技术以及模拟试验等手段，研究樟子松径向生长对气候快速变暖响应的空间差异，探测快速变暖背景下樟子松生长适宜区的动态变化，揭示不同区域樟子松生长的水分供需差异，模拟未来继续变暖背景下樟子松分布的动态变化。研究结果将加强我们对快速变暖背景下东北樟子松天然林分布动态的预测能力，为森林保护决策提供重要的理论依据和数据支持。

东北地区的快速变暖影响该区域主要优势树种的生长和森林的分布动态。樟子松是我国东北天然针叶林中主要的优势树种之一。本项目通过在东北地区对樟子松进行大量的树木年轮采样，发现东北南部干旱区的樟子松生长呈现衰退趋势，而北区半湿润区的樟子松生长呈现加速趋势，使得樟子松的分布有逐渐北移的趋势，而同区域蒙古栎呈现不断的扩张趋势。较高温度在未升温时期（1958-1986）对樟子松生长是负效应，而在快速升温时期（1987-2014）是正效应。很多研究认为升温容易造成生理干旱，从而对树木生长产生负效应，而在未升温时期，高温减缓了北方低温区的低温限制而促进树木生长，而该研究结果推翻了这种观点，并发现这种转换主要是由于生长季水分来源的变化而引起的。快速变暖背景下，生长季前期的水分供给对于樟子松生长至关重要。积雪融水在升温阶段成为生长季前期重要的水分来源。这种树木生长过程中生态因子变化的复杂性增大了很多树木生长预测模型的不确定性。虽然快速变暖促进了我国东北北部地区樟子松的生长，但是东北南部地区天然分布的沙地樟子松林面临萎缩，并有消失的危险。我国东北南部的沙地樟子松需要加强人为经营管理，必要时需要设置种源保护区，以保护我国沙地樟子松的重要种源基地。