干热河谷次生稀树灌木林物种组成变化及群落结构动态

Dynamics of community composition and structure in secondary savanna shrub forest of arid-hot valley in National Nature Reserve of Cycas panzhihuaensis

关键词:  物种组成, 群落多样性, 群落演替, 干热河谷次生稀树灌木林, 四川攀枝花苏铁国家级自然保护区

Key words:  species composition, community diversity, community succession, secondary savanna shrub forest of the arid-hot valley, National Nature Reserve of Cycas panzhihuaensis

摘要:

为揭示四川攀枝花苏铁国家级自然保护区干热河谷次生稀树灌木林群落演替动态规律,该研究以2015年群落内建立的1 hm²永久固定样地为研究对象,经2020年首轮复查,对物种组成、群落多样性、重要值、死亡率、补员率以及胸径(DBH)进行调查研究,以分析5年间群落物种组成及结构动态。结果表明:(1)2020年,群落木本植物共18种,隶属15科18属,较2015年新增1属1种,优势物种组成并无变化,但优势度变化显著。与2015年相比,在重要值(IV)> 1的6个种群中,5个树种IV增高,仅攀枝花苏铁种群IV降低,但其仍为群落优势建群种,铁橡栎和滇榄仁等乔木种群优势度显著增加。(2)2020年,群落中DBH≥1 cm的木本植物个体数增至1 710株,平均胸径由11.10 cm增至11.17 cm。群落年死亡率0.29%,死亡个体平均胸径11.84 cm,年补员率2.75%,补员个体平均胸径4.96 cm。与2015年相比,群落中7个种群出现个体死亡,9个种群出现补员个体。(3)虽然沙针种群规模缩小,但仍有9个种群规模扩大,4个种群规模保持稳定。只有攀枝花苏铁和沙针种群平均胸径减小,其余种群平均胸径均有不同程度的增大。随着森林演替的进行,群落内种间竞争的重要性将逐渐增大,铁橡栎和滇榄仁等乔木树种将在未来演替进程中占据优势地位,但短期内并不会威胁攀枝花苏铁种群优势地位,大径级植株个体的死亡是其优势度显著降低的主要原因。在未来群落演替进程中,攀枝花苏铁将与铁橡栎、滇榄仁等乔木树种组成以乔木树种逐渐占据优势的干热河谷次生稀树灌木林向气候顶极群落演替的过渡型次生林群落。

Abstract:

In order to reveal dynamics of community succession of a secondary savanna shrub forest of the arid-hot valley in National Nature Reserve of Cycas panzhihuaensis in Sichuan, based on the first(2020)reexamined data of 1 hm² permanent fixed plot which was established in 2015, community dynamics over the past five years were analyzed by species composition, community diversity, importance value, mortality rate, recruitment rate and diameter at breast height(DBH). The results were as follows:(1)Woody plants in community changed from 15 families, 17 genera, and 17 species in 2015 to 15 families, 18 genera, and 18 species in 2020. There was no significant change for dominant species composition but a significant change for degree of dominance in the past five years. For the six common populations with higher importance values(>1)in 2020, the importance values of five populations increased, and the population of C. panzhihuaensis decreased only, when compared with their importance values in 2015. C. panzhihuaensis was still the most dominant species and constructive species in the plot, but its importance value declined significantly. However, a significant increase of importance values occurred for some arbor species such as Quercus cocciferoides and Terminalia franchetii.(2)The number of woody plants with DBH≥1 had increased to 1 710 until 2020, the average DBH of all woody plant individuals in this community increased from 11.10 cm to 11.17 cm. The average annual mortality was 0.29%, and the average annual recruitment rate was 2.75%, the average DBH of dead and recruited individuals were 11.84 cm and 4.96 cm respectively. Compared with the woody plants living in 2015, individual trees from seven species had died, and those from nine species were recruited over the past five years.(3)The results also indicated that although Osyris quadripartita declined, the populations of nine species increased, and four were stable from 2015 to 2020. The average DBH of Cycas panzhihuaensis and Osyris quadripartita decreased only, but the others increased to different extents. With forest succession, the importance of interspecific competition within community will increase gradually. Dominant position in community will be occupied by arbor tree species such as Quercus cocciferoides and Terminalia franchetii during process of succession in the future, but dominant position of Cycas panzhihuaensis is not threatened in a short term. The main reason of significant decrease of dominance of Cycas panzhihuaensis is plant individual death of larger diameter class. In the future, a transitional-type secondary community from secondary savanna shrub forest to climax which is occupied by arbor tree species gradually will been consisted of Cycas panzhihuaensis, Quercus cocciferoides, Terminalia franchetii and other arbor trees.