Stand Stability of Pure and Mixed-<i>Eucalyptus</i> Forests of Different Tree Species in a Typhoon-Prone Area

<i>Background and Objectives</i>: The stable stand structure of mixed plantations is the basis of giving full play to forest ecological function and benefit. However, the monocultural <i>Eucalyptus</i> plantations with large-scale and successive planting that caused ecologica...

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Bibliographic Details
Main Authors: Haiyan Deng, Linlin Shen, Jiaqi Yang, Xiaoyong Mo
Format: Article
Language:English
Published: MDPI AG 2021-04-01
Series:Forests
Subjects:
Online Access:https://www.mdpi.com/1999-4907/12/4/458
Description
Summary:<i>Background and Objectives</i>: The stable stand structure of mixed plantations is the basis of giving full play to forest ecological function and benefit. However, the monocultural <i>Eucalyptus</i> plantations with large-scale and successive planting that caused ecological problems such as reduced species diversity and loss of soil nutrients have presented to be unstable and vulnerable, especially in typhoon-prone areas. The objective of this study was to evaluate the nonspatial structure difference and the stand stability of pure and mixed-<i>Eucalyptus</i> forests, to find out the best mixed pattern of <i>Eucalyptus</i> forests with the most stability in typhoon-prone areas. <i>Materials and Methods</i>: In this study, we randomly investigated eight plots of 30 m × 30 m in pure and mixed-<i>Eucalyptus</i> (<i>Eucalyptus urophylla</i> S. T. Blake × <i>E. grandis</i> W. Hill) plantations of different tree species (<i>Neolamarckia cadamba</i> (Roxb.) Bosser, <i>Acacia mangium</i> Willd., and <i>Pinus elliottii</i> var. <i>Elliottii</i> Engelm. × <i>P. caribaea</i> Morelet) on growth status, characterized and compared the distribution of nonspatial structure of the monoculture and mixtures, and evaluated the stand quality and stability from eight indexes of the nonspatial structure, including preservation rate, stand density, height, diameter, stem form, degree of stem inclination, tree-species composition, and age structure. <i>Results</i>: <i>Eucalyptus</i> surviving in the mixed plantation of <i>Eucalyptus</i> and <i>A. mangium</i> (EA) and in the mixed plantation of <i>Eucalyptus</i> and <i>P. elliottii</i> × <i>P. caribaea</i> (EP) were 5.0% and 7.6% greater than those in pure <i>Eucalyptus</i> plantation (EE), respectively, while only the stand preservation rate of EA was greater (+2.9%) than that of the pure <i>Eucalyptus</i> plantation. The proportions of all mixtures in the height class greater than 7 m were fewer than that of EE. The proportions of EA and mixed plantation of <i>Eucalyptus</i> and <i>N. cadamba</i> (EN) in the diameter class greater than 7 m were 10.6% and 7.8%, respectively, more than that of EE. EN had the highest ratio of branching visibly (41.0%), EA had the highest ratio of inclined stems (8.1%), and EP had the most straight and complete stem form (68.7%). The stand stability of the mixed plantation of <i>Eucalyptus</i> and <i>A. mangium</i> presented to be optimal, as its subordinate function value (0.76) and state value (<i>ω</i> = 0.61) of real stand were the largest. <i>Conclusions</i>: <i>A. mangium</i> is a superior tree species to mix with <i>Eucalyptus</i> for a more stable stand structure in the early growth stage to approach an evident and immense stability and resistance, which is of great significance for the forest restoration of <i>Eucalyptus</i> in response to extreme climate and forest management.
ISSN:1999-4907