Abstract
Abstract. Close-to-nature management (CTNM) has been proposed as a promising forestry management approach to improve the structure and quality of forests, which integrates wood production and ecological service functions. Research on the effect of CTNM on the univariate and bivariate distribution of the spatial structure of forest stands provides a scientific basis for the evaluation of CTNM implemented in forestry. Here, we analyzed and compared the spatial-structure characteristics of Masson pine (Pinus massoniana) plantations (young, middle-age, and near-mature stages) under CTNM 8 years after selective cutting and unmanaged control. We used univariate and bivariate distribution of three spatial-structure parameters: mingling (M), dominance (U), and uniform-angle index (W). Results showed that the effect of CTNM on spatial structure was more remarkable in middle-aged and near-mature Masson pine forests compared with the young forest. CTNM significantly improved mingling degree and promoted the horizontal distribution, thereby changing from a cluster to a random distribution. Moreover, CTNM improved the proportion of trees with a high mixing degree and random distribution and the proportion of trees having a micro-structure of random distribution with a high degree of mixture and dominance with a high degree of mixture in middle-aged and near-mature Masson pine forest. Overall, the implementation of CTNM 8 years ago showed a positive effect on the improvement of the spatial structure of Masson pine forest, but the present spatial structure is suboptimal. Further implementation of CTNM to adjust the mingling and uniform-angle index is necessary, and CTNM according to this method of frequency distribution of stand structure parameters can improve the success of forest management.
Highlights
Close-to-nature management (CTNM) is a promising forestry management approach, which simultaneously integrates wood production and ecological service functions of a forest at a relatively small spatial scale, such as stand level, by developing a structure similar to that of an original forest (O’Hara, 2016; Wang et al, 2018)
Most trees in all stands were concentrated with a structural combination of M = 0.00 and U = 0.00–1.00, which showed a total frequency in the control and managed treatments of 0.885 and 0.697 in young stands, 0.701 and 0.351 in middle-aged stands, and 0.646 and 0.320 in near-mature stands, respectively
Regardless of the kind of stand, the M–W bivariate distribution showed that the maximum frequency appears at M = 0 at each row of the uniform-angle index (W ), and the frequency at each column of mingling (M) initially increased and decreased with the increase of W classes, which reached its maximum at W = 0.5
Summary
Close-to-nature management (CTNM) is a promising forestry management approach, which simultaneously integrates wood production and ecological service functions of a forest at a relatively small spatial scale, such as stand level, by developing a structure similar to that of an original forest (O’Hara, 2016; Wang et al, 2018). In this method, trees of different ages and sizes are distributed in the same stand, new trees are established through natural recruitment, and lumber harvest selectively occurs throughout the forest stand (Li et al, 2014a). Previous studies mainly used univariate distribution or the average value of these parameters to evaluate the spatial-
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