JFS

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Vol. 28, No. 4, pp. 199-204, November, 2012 http://dx.doi.org/10.7747/JFS.2012.28.4.199

The Development of Climax Index by Analysis of Eco-morphological Characters for Major

Deciduous Tree Species

Ji Hong Kim*, Sang Hoon Chung, Jeong Min Lee and Se Mi Kim

Department of Forest Management, College of Forest & Environmental Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea

Abstract

This study was conducted to estimate climax index by eco-morphology for major 36 tree and sub-tree species in natural deciduous forests so as to interpret seral position of each species in the forest community. Fourteen eco-morphological characters which were considered to be associated with successional gradient in the forest were selected for the study.

Four levels per character for each species were given on a standardized scale of increasing climax, and the index was computed by the proportion of the sum of total scores, expressed by percent values. With calculated mean value of 54.8 for all indices, Carpinus cordata had the highest index value of 90.5, and Populus davidiana recorded the lowest of 13.2. The most climax group, greater than 70 of the index, contained only 8 species, intermediate group, between 41 to 70 of the index, had 23 species, and the most pioneer group, less than 40 of the index comprised 5 species.

The result has noticed that the large number of species would take advantage of most diverse resource and niche in the intermediate stage of the sere in the forest. By cluster analysis all 36 species were subjected to be classified into several species groups which had common similar eco-morphological characteristics. The indices were additionally plotted on the two dimensional graph to recognize the positions related to the light absorption factor and reproduction factor. The climax index of tree and sub-tree species developed by this study could be applied to understand the present status of successional stage on the basis of species composition by the method of summing up the indices. And comparison of forest successional stage among various forest communities could be done by summing up the climax indices of composed species in each community. However, this kind of applied methodology should be limited to the forest of similar species composition and site condition.

Key Words: forest succession, deciduous species, tree eco-morphology, climax index, cluster analysis

Received: March 13, 2012. Revised: October 25, 2012. Accepted: October 30, 2012.

Corresponding author: Ji Hong Kim

Department of Forest Management, College of Forest & Environmental Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea

Tel: 82-33-250-8333, Fax: 82-33-243-4484, E-mail: [email protected]

Introduction

The development of forest communities and relative sta- bility are two major aspects of the succession process.

Succession is a natural change in the deciduous forest that involves the gradual, continuous replacement of one group

of species by another. The early stages of forest succession are commonly characterized by communities containing a small number of species. The direction of change is toward more diverse, making physiognomy more complex. The impetus for this change comes from the plants themselves as pioneering species create conditions that prevent them

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from regeneration. In time the pioneers are replaced by plants that can reproduce in the changed circumstances.

The theoretical endpoint of this process is reached when plants that can reproduce in the environmental conditions they create take over a forest community. This endpoint, self-maintaining steady state, is called the climax (Kim 2002).

The dominant growth form of deciduous dicotyledonous trees of the deciduous forest exhibit a wide variety of morphology and ecophysiology connected with seral stage, and therefore should produce insights applicable to the forest in general (Kim 1993). The pioneer species, such as Populus spp. and Betula spp., are characterized by rapid opportun- istic invasion of ephemerally open, sunny sites, free of dense vegetation, and hence at first with reduced levels of com- petition or interference among species for light, soil mois- ture, and mineral nutrients (Jin and Kim 2005; Yeom and Kim 2011). Seedlings of pioneers are usually very intolerant of shade because of reduced photosynthetic efficiency at low light intensity, and because of reduced energy reserves in the seed correlative with reduced seed weight, which is correlative with greatly augmented number of seeds, reaching transiently open sites at some distance from the parent tree.

Potential canopy trees of pioneer character have rapid and excurrent growth, the strong apical dominance ensuring enough height to maintain the crown in full sunlight, but at the expense of crown breadth and richness of branching orders, thereby favoring light penetration (Kang and Kim 2000; Kang et al. 2000).

On the other hand, the major characters of climax tree species are interference with light penetration and competi- tion for other resources, among closely spaced and often su- perposed individuals. Climax species tend to have large energy and nutrient reserves in the endosperm of their seeds, which provide a heterotrophic head-start for the seedling, en- abling it to put down deeper, more competitive roots. The in- creased seed weight carries with it conservative, short-range dispersal ability, because of the correlative reduction in seed numbers and because of their lack of mobility, which usually causes them to fall in the shade of the forest canopy. The low light intensity under the closed canopy has evidently selected for photosynthetic efficiency in the most climax spe- cies, such as Acer pictum subsp. mono and Tilia amurensis, which are tolerant of shade at the seedling and sapling

stage. Climax trees in the deciduous forest tend to have slow and deliquescent growth with weak apical dominance re- sulting in broad and spreading crowns with numerous branching orders and intricately arranged ultimate twigs and leaves that cast deep shade. Reproductive maturity is delayed in favor of vegetative establishment (Jin and Kim 2006; Kim et al. 2011).

It is recognized that eco-morphological characteristics of each tree species appearing in the sere can be used as a con- venient index to estimate successional stage or the past dis- turbance history of the forest community in spite of the dif- ficulties of species composition analysis and insufficient of historical evidence. Based upon the analysis of eco-morphological characters of light absorption factors and reproduction factors, this study was conducted to develop climax index which might interpret the position of the successional sere for the canopy species in the natural deciduous forest in Baekdudaegan Mountains.

Materials and Methods

Having noticed the close relationship between eco-morphological characteristics of trees and successional stage of forest community, the climax index, which was mentioned in the introduction, was estimated for thirty six broad-leaved tree species growing in natural deciduous forests. The prin- cipal dominant and co-dominant tree species were selected in the natural deciduous forest of the Baekdudaegan Mountains such as Guryongsan, Bonghwangsan, and chungoksan, where no artificial silvicultural activities had been taken place for the last several decades. The 14 eco-morphological characters adopted in the study were summarized as follows:

Light absorption factors

1) Apical dominance: Excurrent growth habit of shoot in the pioneering way of tree life (Horn 1971; Kim 1993; Lee 2011)

2) Branch order: More branch orders likely in climax species (Wells 1976; Kim 1993; Lee 2011)

3) Phyllotaxy: Maximal interception of light efficiently arranged leaf mosaics in pioneer species (Horn 1971; Kim 1993; Lee 2011)

4) Leaf division: Leaflets or lobes likely in the pioneer-

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Table 1. The segmentation of scoring for 14 eco-morphological characters to estimate the climax index Eco-morphological

characters Segmentation of scoring

Apical dominance Branch order Phyllotaxy Leaf division Leaf blade (cm²) Leaf orientation Leaf oscillation Cuticle luster Pigmentation Seed dispersal Age to fruit (yrs) Mast period (yrs) Live crown ratio Shade tolerance

Excurrent=0 2-3=0 Spiral=0 Compound=0

<10=0 Vertical=0 High=0 Lustrous=0 Yellowish=0 Wind=0

<10=0 1=0

＜20=0 Low=0

Semi-excurrent=1 3-4=1 Alternate=1

>1/2 lobed=1 10-50=1 Semi-vertical=1 Mid-high=1 Semi-lustrous=1 Light green=1 Windㆍgravity=1 10-20=1 1-2=1 20-40=1 mid-low=1

Semi-decurrent=2 4-5=2 Opposite=2

<1/2 lobed=2 51-100=2 Semi-horizontal=2 Mid-low=2 Semi-dull=2 Green=2 Bird=2 21-30=2 3-4=2 40-60=2 Mid-high=2

Decurrent=3 5-6=3 2-ranked=3 Undivided=3

>100=3 Horizontal=3 Low=3 Dull=3 Blue-green=3 Mammal=3

>30=3

>4=3

>60=3 High=3 ing way of tree life (Horn 1971; Kim 1993; Lee 2011)

5) Area of leaf blade: Broader leaves likely in climax species (Wells 1976; Kim 1993; Lee 2011)

6) Leaf orientation: Vertically oriented leaves in the pioneering way of tree life (Wells 1976; Kim 1993; Lee 2011) 7) Leaf oscillation: Quaking habit of leaves in the pioneering way of tree life (Wells 1976; Kim 1993; Lee 2011) 8) Cuticle luster: Clear and waxy material of outer layer of leaves in the pioneering way of tree life (Wells 1976; Kim 1993; Lee 2011)

9) Pigmentation: light yellowish green color of leaves in the pioneering way of tree life (Wells 1976; Kim 1993; Lee 2011)

Reproduction factors

10) Seed weight and dispersal: Light seeds and dispersal by wind in the pioneering way of tree life (Harper et al.

1970; Wells 1976; Lee 2011)

11) Age of first fruiting: Younger age of first fruiting in the pioneering way of tree life (Fowells 1965; Lee 2011)

12) Periodicity of seed production: Annual production of seeds in the pioneering way of tree life (Wells 1976; Lee 2011)

13) Live crown ratio: Greater ratio of live crown likely in climax species (Lorimer 1982; Lee 2011)

14) Shade tolerance: More shade tolerance likely in climax species (Kim 1999; Lee 2011)

Each species was scored for the 14 eco-morphological characters according to available data, which were arbitra- rily segmented into mostly 4 steps per character on a standardized scale of increasing climaxness. For those characters that would likely appear in the early successional stage were marked as "0", and characters of more likely in climax stage were given as maximum of "3", matching four scoring ar- rangement (Table 1).

At least ten trees were sampled for each species. Each sample tree was correspondingly scored from 0 to 3 for fourteen characters. The score of a certain character of a species was calculated by numerical mean. The next ap- proach was the summation of the scoring values for all characters in the vector of each species. In order to express these values as a climax index, the sums were transformed into percentages of maximum possible value.

The independently derived climax indices were subjected to cluster analysis to classify and recognize species groups which probably possessed common eco-morphological characters. The analysis was done by Ward's method, also known as Minimum variance clustering, on the basis of 14x36 data matrix of the character analysis (Orloci 1967; Everitt, 1973; Hartigan 1975). This method has great intuitive appeal because it is based on the simple un- derlying principle that at each stage of clustering the variance within clusters is minimized with respect to the variance between cluster (Ludwig and Reynolds 1988). The

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Fig. 1. Frequency distribution of 36 tree species on the climax index class.

Table 2. The list of species codes and climax indices (CI) for 36 broadleaved deciduous tree species. The codes are applied in Figures 3, 4, and 5

Code No. of

samples Species CI (%)

CC CL AG AM AP UP UL TA MS SO SA QM

CV CR QS AN JM PG CW QD PP FR FM MB MA QA PA QV QL PS KP BC BS BD BP PD

12 25 17 32 19 13 15 33 14 14 17 30 13 16 18 12 10 15 13 18 11 19 11 18 14 19 12 19 13 10 10 13 14 13 16 13

Carpinus cordata Carpinus laxiflora Acer tegmentosum Acer pictum subsp. mono Acer pseudosieboldianum Ulmus davidiana var. japonica Ulmus laciniata

Tilia amurensis Magnolia sieboldii Styrax obassia Sorbus alnifolia Quercus mongolica Cornus controversa Castanea crenata Quercus serrata Acer mandshuricum Juglans mandshurica Prunus sargentii Cornus walteri Quercus dentata Prunus padus Fraxinus rhynchophylla Fraxinus mandshurica Morus bombycis Maackia amurensis Quercus acutissima Phellodendron amurense Quercus variabilis Quercus aliena Platycarya strobilacea Kalopanax septemlobus Betula costata Betula schmidtii Betula davurica

Betula platyphylla var. japonica Populus davidiana

90.5 88.0 82.6 80.0 79.1 77.5 77.0 74.8 67.6 67.3 60.7 55.0 54.2 54.0 53.4 53.2 53.0 52.5 52.4 52.4 52.4 51.0 50.0 48.8 47.8 47.6 47.3 45.4 45.2 43.5 42.9 37.2 27.9 27.3 21.4 13.2 SPSS Statistics 18.0 (SPSS, Inc.) software was employed to implement the analysis.

Results and Discussion

Climax indices

Thirty six tree species were subjected to set ordination

according to their succession oriented eco-morphology from the data of Table 1. The outset of climax index was the summation of scoring values for all averaged characters in the vector of each species. The row score sums were ob- tained in this way range from 5.6 (Populus davidiana) to 38.0 (Carpinus cordata) on a potential scale of 0 to 42. The conversion of these values to a climax index was done by calculating percentage of the maximum possible value. On this scale the range was from 13.2 of Populus davidiana to 90.5 of Carpinus cordata (Table 2), objectively agreeing with empirical observation for P. davidiana as pioneer species and for Carpinus cordata as climax species.

If this range of climax index was divided into 3 incre- ments of 20 points each, an unequal distribution of species among 3 categories was observed. In the pioneer group (CI of 10-40), there were 5 species. In numerical ordination these were aspen and birches. The second group of intermediate species (CI of 41-70) was by far the largest because of most number of 23 species of oaks, ashes, cherries, dog- woods, walnut, and various deciduous species. It is likely because the duration of mid-successional stage would be quite long period of time, generally hundreds of years, many tree species could invade and be adopted to the inter- vally changing environment. This meant that the large number of species would take advantage of most diverse resources and niches in the intermediate stage of the sere in the forest. The third, most climax group (CI of 71-100) contained 8 species. They were hornbeams, maples, elms, and basswood (Table 2).

The frequency distribution of selected species on the climax index class of 10 units was diagrammed in Fig. 1. The

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Table 3. The list of species climax indices done by Kim (1993)

Species CI Species CI

Acer barbinerve Acer ginnala Acer triflorum

Acer tschonoskii var. rubripes Ailanthus altissima Alnus hirsuta Alnus japonica Betula chinensis Betula ermani Carpinus tschonoskii

60.4 29.2 54.2 60.4 39.6 47.9 50.0 58.3 60.4 77.7

Celtis jessoensis Celtis sinensis Lindera erythrocarpa Picrasma quassioides Populus tomentiglandulosa Robinia pseudo-acasia Salix koreensis Sorbus commixta

Syringa reticulata var. mandshurica Zelkova serrata

66.7 68.8 64.6 52.1 20.8 39.6 35.4 39.6 50.0 81.3

Fig. 2. Dendrogram of the relationship of 36 species. The Rescaled Distance value of 3.5 resulted in 5 species groups. Letter codes for species were given in Table 2.

overall average value was 54.84, showing quite variation and somewhat of normal distribution. The most number of 12 species was apportioned in the climax index class of 50s, and 8 species in the class of 40s, taking up 56% of the total.

The authors presented additional list of species climax indices not in Table 1, but in the previous study done by Kim (1993) by similar methodology (Table 3).

Cluster analysis and plotting

In order to recognize species group which would have common eco-morphological characters, selected species were subjected to be classified by cluster analysis. Cluster analysis is a classification technique for placing similar enti- ties or objects into groups or clusters. The cluster analysis models are used to place similar samples into clusters, which are arranged in a hierarchical treelike structure called a dendrogram.

The analysis was done by Ward’s method, also known as minimum variance clustering, for 36 species on the basis of 14x36 data matrix of the character analysis. The authors took “rescaled distance cluster combine” 3.5 as the stand- ard, the species were classified into 5 groups, diagrammed in Fig. 2.

Group 1 contained the most pioneer charactered species such as aspen and birches. They are characterized by shade intolerance and fast growing with serrated small leaves.

They usually have very small-sized seed with dispersal mechanism by wind. Group 2 included such species as Fraxinus rhynchophylla, F. mandshurica, Acer mandshuricum, Phellodendron amurense, and Platycarya strobilacea. They have apparent common feature of pinnately compound

leaves. Group 3 was divided by those species of Prunus pa- dus, P. sargentii, Styrax obassia, Magnolia sieboldii, and Sorbus alnifolia. They commonly bear drupes, having a single hard stone that encloses a seed which is dispersed by animal, mainly birds. They also have medium to large sized leaves and intermediate shade tolerance. Group 4 contained largest number of species by 12. Six representative oak species were belong to this group, and so were Castanea crenata, Cornus controversa, C. walteri, Morus bombycis, and Kalopanax septemlobus. They produce large sized leaves and medium to large sized heavy seeds that are dispersed by an- imals such as rodents and birds. Group 5 had most climax charactered species. They were Carpinus cordata, C. laxi- flora, Acer tegmentosum, A. pictum subsp. mono, A. pseudosie- boldianum, Ulmus davidiana var. japonica, U. laciniata, and

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Fig. 3. Distribution of 36 species by Light absorption and Reproduction.

Letter codes for species were given in Table 2.

Tilia amurensis.

The study species were plotted on the axes of light absorption factor and reproduction factor (Fig. 3). The two factors were considerably correlated, noting that the higher light absorption values were estimated, the higher reproduction values were presented. And the results to form groups indicated similar pattern with cluster analysis.

Acknowledgements

This study was conducted with the support of 'Forest Science & Technology Projects (Project No. S211012 L030110)' provided by Korea Forest Service.

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