川西亚高山天然林岷江冷杉的更新结构与数量动态

Regeneration structure and dynamics of Minjiang fir in four typical natural forest types in subalpine area in western Sichuan,China

岷江冷杉(Abies fargesii var.faxoniana)的天然更新是川西亚高山地区天然次生林生态恢复的关键。为揭示川西亚高山4种典型天然林林型(杜鹃-岷江冷杉林、箭竹-岷江冷杉林、红桦-岷江冷杉林和红桦林)中岷江冷杉的更新结构和其幼龄植株的生存过程,基于4块1 hm2样地的调查,通过单因素方差分析和多重比较对比不同林型中岷江冷杉的更新结构和更新质量;通过对数回归建立了岷江冷杉幼龄植株高度与年龄间的关系;通过建立幼龄植株的静态生命表、绘制存活曲线和计算数量动态指数分析其生存特征和存活瓶颈期。结果表明:4种林型中岷江冷杉的更新质量和幼龄植株存活状态依次为杜鹃-岷江冷杉林>红桦林>红桦-岷江冷杉林>箭竹-岷江冷杉林。各林型中岷江冷杉幼龄植株的死亡率与相邻龄级间的个体数量动态(V_(n)指数)随龄级增加的波动大。综合死亡率与V_(n)指数的龄级差异,杜鹃-岷江冷杉林和箭竹-岷江冷杉林中幼龄植株存活的年龄瓶颈期分别为第21—25年(树高0.66—1.04 m)和第11—15年(树高0.46—0.73 m);红桦-岷江冷杉林和红桦林中幼龄植株存活的年龄瓶颈期分别为第16—20年(树高0.60—0.89 m)和第11—15年(树高0.19—0.40 m)。本研究通过比较川西亚高山4种典型天然林中岷江冷杉的更新结构和其幼龄植株数量动态,揭示了各林型中岷江冷杉的更新质量,探明了制约幼龄植株存活的瓶颈阶段。本研究可为川西亚高山天然林中岷江冷杉更新的抚育和管理提供技术支撑。

The natural regeneration of Minjiang fir(Abies fargesii var.faxoniana)plays an important role in the forest ecology restoration in the subalpine region of western Sichuan Province.Previous studies on the regeneration of Minjiang fir have mainly focused on the density of seedlings in different forest types,the effects of bamboo abundance and temperature increase on seedlings,spatial association analysis between young individuals and dominant species trees of different diameter classes,regeneration dynamics in the treeline ecotone,etc.However,comparative studies on the regeneration structure,regeneration quality of Minjiang fir,and the survival bottleneck periods of young Minjiang fir between primary forest with Minjiang fir as the dominant species and natural secondary forest after logging are rare.Therefore,the objective of this study was to reveal the size-class structure,regeneration quality of Minjiang fir and the age structure,quantitative dynamics,and development trend of the young Minjiang fir population in four typical natural forest types(Rhododendron-Minjiang fir forest,Fargesia-Minjiang fir forest,Betula albosinensis-Minjiang fir forest,and B.albosinensis forest)of the subalpine forest in western Sichuan.Based on four 1 hm2 plots for each forest type,we analyzed the size-class structure,regeneration quality,and survival bottleneck stages of young Minjiang fir in the four forest types by height-age regression models,the crude density of regeneration,stationary life table,survival curve,and dynamic quantization of age structure.The results showed that the order of regeneration quality and survival status of Minjiang fir in the four forest types was Rhododendron-Minjiang fir forest,B.albosinensis forest,B.albosinensis-Minjiang fir forest,and Fargesia-Minjiang fir forest.The mortality and dynamic index of the population age structure(V_(n) index)of the young Minjiang fir population fluctuated greatly with the increasing age of young Minjiang fir.The results of the mortality and the V_(n) index showed the survival bottleneck stages for the growth of the young Minjiang fir in the Rhododendron-Minjiang fir forest and Fargesia-Minjiang fir forest were from the ages of 21 to 25(tree heights of 0.66—1.04 m)and the ages of 11 to 15(tree heights of 0.46—0.73 m).The survival bottleneck stages for the growth of the young Minjiang fir were from the ages of 16 to 20(tree heights of 0.60—0.89 m)and the ages of 11 to 15(tree heights of 0.19—0.40 m),respectively,in the B.albosinensis-Minjiang fir forest and B.albosinensis forest.By comparing the regeneration structure and quantitative dynamics of young Minjiang fir,we revealed the regeneration quality of Minjiang fir and explored the age bottleneck and height bottleneck stages that critically constrain the survival of Minjiang fir in the four typical forest types.Our findings provide support for the targeted care and management of young Minjiang fir individuals in subalpine natural forests of western Sichuan Province.