台州市乔木林树种结构变化模拟与预测

Simulation and prediction of tree species composition change of forests in Taizhou City

【目的】阐明浙江省台州市乔木林1994—2019年25 a间3个树种组(松类、杉类和阔叶类)之间的结构变化规律以及未来可能的变化趋势,为今后森林结构调控提供依据。【方法】基于6期台州市森林资源连续清查固定样地数据,建立非线性方程组自约束树种结构模型,模拟25 a来3个树种组的株数比例和材积比例变化规律,并预测其变化趋势。【结果】①台州市松类受松材线虫Bursaphelenchus xylophilus病以及自然演替中的不利因素影响其比例持续降低,杉类的比例在1999—2004年达到最大值后缓慢下降,阔叶类比例呈现持续快速稳定增加的趋势;②经预测,松类、杉类和阔叶类各树种组林木株数占乔木林总株数的比例将分别从2019年的14.00%、24.90%和61.20%趋向于极限4.09%、7.02%和88.89%,占乔木林总材积的比例将从2019年的24.60%、29.70%和45.70%趋向于极限10.07%、11.94%和77.99%。【结论】整体上,台州市过去25 a间乔木林资源总量持续增加,树种结构“针减阔增”,朝着结构更合理的顶级植被群落方向演替。松类和杉类的比例虽然在下降,但最终会稳定在一定的比例而不会消亡。本研究提出的非线性方程组自约束树种结构模型对乔木林的株数比例和材积比例模拟具有较好的适应性,对变化趋势的预测具有较好的合理性。图2表7参26。

[Objective]This study,with an exploration of the composition changes among three tree species groups of pine,fir and broadleaf within 25 years between 1994 and 2019 in Taizhou City,Zhejiang Province,is aimed to investigate the possible future change trends so as to provide theoretic basis for future forest composition regulation.[Method]Based on six batches of continuous forest inventory data collected in Taizhou City,a self-constrained model with nonlinear equations was developed to simulate the proportion of numbers of trees and proportion of stem volume of three species over 25 years,and predict their future trends.[Result](1)As a result of Bursaphelenchus xylophilus and natural succession,the proportion of pine species in Taizhou suffered a decrease,that of fir species reached a maximum between 1999 and 2004 and then decreased slowly whereas that of broadleaf species enjoyed a continuous and steady increase;(2)The proportions of trees of the pine,fir and broadleaf groups accounting for the total numbers will change from 14.00%,24.90%and 61.20%in 2019 to 4.09%,7.02%and 88.89%eventually,whereas the proportions of the three groups in terms of volumes will change from 24.60%,29.70%and 45.70%in 2019 to 10.07%,11.94%and 77.99%eventually.[Conclusion]The total amount of forest resources in Taizhou increased in the past 25 years and,with a structural change of tree species featured as“an increase in broadleaf and a decrease in coniferous forests”,it’s gradually developing into a top vegetation community.Although the proportion of pine and fir trees decreases continuously,it will eventually stabilize at a certain proportion instead of going extinct.Also,the proposed self-constrained model of nonlinear equations demonstrated good performance in the simulation of tree number proportion and volume proportion of forests.[Ch,2 fig.7 tab.26 ref.]