江西武夷山中亚热带南方铁杉针阔混交林群落组成与结构

Community composition and structure of a mid-subtropical coniferous (Tsuga chinensis var. tchekiangensis) and broadleaf mixed forest in Jiangxi Wuyishan,China

长期监测型固定样地是研究物种分布格局、群落动态和生物多样性维持机制等森林生态系统特征、过程与机理的重要平台。我国亚热带地区已建立的森林固定样地多为阔叶林类型,而针叶(阔叶混交)林类型十分有限。按照巴拿马Barro Colorado Island大型森林固定样地的建设规范,于2014年在江西武夷山国家级自然保护区内海拔1800 m左右的南方铁杉(Tsuga chinensis var. tchekiangensis)天然种群分布区域建立中亚热带针阔混交林6.4 hm^2固定样地。木本植物调查结果表明:(1)样地内胸径≥1 cm的木本植物共有29科53属89种,显著低于我国亚热带阔叶林样地平均水平,但显著高于温带针叶(阔叶混交)林样地平均水平;(2)在区系组成上,科以热带成分为主,而属以温带成分为主;(3)样地内独立个体数密度为2252株/hm^2,与温带针叶(阔叶混交)林平均水平相当,但显著低于亚热带阔叶林平均水平;(4)胸高断面积为37.89 m^2/hm^2,与亚热带阔叶林样地平均水平相当,但显著低于温带针叶(阔叶混交)林平均水平;(5)群落成层现象显著,优势种明显,多度排名前4位的物种的个体数占总个体数的55%,而排名后40的物种仅占1%;(6)群落总径级结构呈倒"J"型分布,其中胸径≤10 cm的小径木占总个体数的76.9%,而胸径>30 cm的大径木仅占5.3%;(7)主要树种的径级结构有偏正态分布和"L"型分布等类型,但它们的种群在空间上均呈现显著的聚集分布特征;(8)南方铁杉虽然是群落现阶段最重要的优势种,但它的种群更新缓慢。研究结果充分显示该样地对中国森林多样性监测以及南方铁杉种群保育的重要意义。

Long-term plots are important platforms for research on forest ecosystem characteristics, processes, and functioning such as species spatial distribution, community dynamics, and mechanisms for the maintenance of biodiversity.Many long-term forest plots have been established in subtropical China, but most of them are broadleaf forests. Plots that focus on coniferous （ and broadleaf mixed） forests in that region are still scarce. Following the field protocol of the large long -term plot on Barro Colorado Island in Panama, a 6.4 hm2 mid-subtropical coniferous and broadleaf mixed forest long-term plot was established in the natural distribution area of Tsuga chinensis var. tchekiangensis （Pinaceae） at an elevation of around 1800 m in Jiangxi Wuyishan National Nature Reserve in 2014. The first inventory of woody plants with diameter at breast height （DBH） /〉 1 cm in the plot showed that （ 1 ） there were a total of 89 woody species belonging to 53 genera of 29 families ; these values were significantly lower than the averages of subtropical broadleaf forest （ SBF ） plots, but significantly higher than those of temperate coniferous （ and broadleaf mixed） forest （TCF） plots in China. （2） Tropical areal types were the major floral components at the family level, whereas temperate areal types were the major floral components at the genus level. （3） The density of independent individuals was 2252 /hm2, which was similar to the average of TCF plots, but significantly lower than that of SBF plots. （4） The basal area at breast height of the plot was 37.89 mZ/hm2, which was similar to the average of SBF plots, but significantly lower than that of TCF plots. （5） Canopy layering was evident and dominant species were distinct in the community. The sum of the abundance of the four most- abundant species was as high as 55% of the total abundance; however, the sum of abundance of the 40 least-abundant species was only 1% of the total. （6） The DBH distribution of the community appeared as a reversed ＇ J＇ shape. The number of small-size （ DBH ~〈 10 cm） individuals was around 76.9% of the total abundance, whereas the number of large- size （DBH 〉 30 cm） individuals was only 5.3% of the total. （7） For the major species, DBH distribution shapes appeared as various types, such as a skewed distribution and ＇ L＇ shape, but spatially they all showed aggregated distribution patterns within the plot. （8） Though T. chinensis var. tchekiangensis was the most dominant species at the current successional stage, its recruitment rate was low. These findings demonstrate important values of this long-term plot for the monitoring of forest biodiversity and conservation of T. chinensis var. tchekiangensis in China.