Open Journal of Forestry
2013. Vol.3, No.2, 62-65
Published Online April 2013 in SciRes (http://www.scirp.org/journal/ojf) http://dx.doi.org/10.4236/ojf.2013.32010
62
Evaluation of Broadleaf Tree Diversity at the
Basin Scale—In Case of Artificial
Chamaecyparis obtusa Forests
Sayumi Kosaka, Yozo Yamada
Graduate School of Bio-Agricultural Sciences, Nagoya University,
Nagoya, Japan
Received November 22nd, 2012; revised February 4th, 2013; accepted February 26th, 2013
Copyright © 2013 Sayumi Kosaka, Yozo Yamada. This is an open access article distributed under the Creative
Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly cited.
In recent years, the various functions required of forests, especially the conservation of biodiversity, have
been attracting increasing attention in Japan and worldwide. In Japan, 67% of national land is covered by
forest, 41% of which is artificial forest (i.e., plantations). Therefore, forest biodiversity conservation ef-
forts should also target artificial forests. In this paper, we seek to promote sustainable forest management
that considers biodiversity conservation by examining indices that can be used by forest managers to
evaluate the diversity of broadleaf trees. The result was that evaluation of broadleaf tree diversity in arti-
ficial forests at a basin scale was possible by combining several types of indicators.
Keywords: Artificial Forest; Forestry Management; Basin Scale; Species Diversity Index; Land Use
Diversity Index
Introduction
In recent years, various functions have been required of for-
est ecosystems; these include not only the production of wood,
but also the conservation of biodiversity, landslide prevention,
cultivation of water sources, overall ecosystem health, and pre-
vention of global warming. In particular, the conservation of
biodiversity is considered a necessary function to promote sus-
tainable land use and to conserve biodiversity of surrounding
land-use types at a basin scale.
In Japan, approximately 67% of national land is covered by
forest, approximately 41% of which is artificial forest (The
Forest Agency, 2012). Therefore, in addition to natural ecosys-
tems, conserving biodiversity within artificial forests is also
crucial. To this end, management efforts within plantations
must include thinning of the planted conifers and the mainte-
nance of naturally regenerated broadleaf trees and understory
vegetation. Forest managers must have a deep understanding of
the unique species diversity of the broadleaf trees within their
forests so as to promote forest management that considers tree
conservation. However, clear guidelines or management ap-
proaches have not yet been established. Furthermore, appropri-
ate studies are rare, both in Japan and worldwide, and tend to
examine forests only at a small scale.
In this paper, we seek to promote sustainable forest man-
agement that considers biodiversity conservation by examining
indices that can be used by forest managers to evaluate the
diversity of broadleaf trees. We used several indices for evalua-
tion, and we focused on the basin scale, which corresponds to
the whole-forest level.
Survey Location and Methods
Survey Location
The survey was conducted at Hayami Forest located in Kiho-
kucyou Kita, Mie Prefecture, Japan. Plots were established in
Ootaga Forest (93 ha; 10 - 380 m above sea level; angle of in-
clination, 3 - 45 degrees) within Hayami Forest. Average an-
nual temperature is 16.1˚C, and annual precipitation is 4200
mm (Meteorological Agency of Japan, 2012). Forest compart-
ments vary in age and form a mosaic landscape.
Hayami Forest is currently managed using an intensive nur-
turing system aimed at the production of good wood over long-
term cutting periods. Chamaecyparis obtusa, which is well suit-
ed to regional conditions, is the main production wood. Hayami
Forest was the first forest to obtain forest certification from the
Forest Stewardship Council A.C. (FSC) of Japan in February
2002.
Methods
Our research was conducted within five compartments that
varied in age. We established 10 × 10 m plots within areas rep-
resentative of the compartment, i.e., those lacking gaps, edge
effects, and mountain streams. We examined all broadleaf and
planted trees that were taller than 1 m. Broadleaf trees were
chosen because they are affected by management efforts and
they can be managed and investigated easily. For all broadleaf
trees, we determined the number of species and the population
size. We also measured tree height and diameter at a height of
50 cm from the ground, as we were unable to measure many
individuals at heights of 1 - 1.3 m. For planted trees, we also

S. KOSAKA, Y. YAMADA
measured height and diameter and counted the number of plant-
ed trees in 20 × 20 m areas to calculate stand density.
Analysis at the Compartment Scale
We analyzed the current conditions of compartments using
stand density, which is an important measure of forest mainte-
nance. For the analysis of broadleaf tree diversity within com-
partments, we used the number of species, population size,
proportion of basal area (BA), and several species diversity
indices. A 50-cm aboveground cross section was used to calcu-
late BA as follows: BA = sum of 50 cm aboveground cross
sections of a specific layer in the plot/sum of 50 cm above-
ground cross sections of all trees in a plot. The proportion of
BA of the natural forest was not calculated because no conifers
exist within the natural areas of Hayami Forest, and thus the
calculation result would be 100%. We used the Shannon-Wien-
er index (1), the inverse Simpson index (4), and the inverse log-
arithm Simpson index (5) as indices of species diversity (Yo-
shiaki & Kazunori, 2002):
Shannon-Wiener index (H')
2
logHpi

pi (1)
where
N
i
pi
N
 is the relative frequency of i; Ni is the popula-
tion size of I; N is population size.
Index of Simpson (D)
2
Dpi (2)
An unbiased estimator (D')



1
1
Ni Ni
DNN


 (3)
An inverse Simpson index (L)
1
L
D

 (4)
An inverse logarithm Simpson index (L')
1
logLD
 (5)
Analysis at the Basin Scale
The land use diversity index (LUDI) was used for the analy-
sis of forests at the basin scale. The LUDI is commonly used in
landscape studies to improve the measurement of diversity at
the landscape scale. This index enables the evaluation of all
types of landscapes using mathematically weighted functions
based on landscape structure and composition. The formula for
the LUDI is as follows (6):


1
2π
21
1
m
j
aj
mjWcjkjkj aj
pj
MAm



 








(6)
where
M
 is the weighted land-use diversity index; m is the
number of patch types present in a landscape unit
j is 1,···,m is patch type;
Wcj is the compositional weight of patch type j;
kj is the upper limit of the structural weight of patch type j;
pj is the sum of the perimeter of patch type j;
aj is the sum of the area of patch type j;
A is the sum of patch areas in a landscape unit.
Here, we divided all compartments in Ootaga Forest into five
groups based on stand density. Thus, a value of 5 was used for
m, and Pj, aj, and A were calculated using a geographic infor-
mation system (GIS). In addition, evaluation results for com-
partments were used for Wcj, after correcting each value so that
the maximum was 1. To determine the maximum value of the
LUDI, we considered the maximum as M1max and compared
these results with M'.
Results and Inquiry
Analysis of Compartments
Stand density exhibited a decreasing trend as the age of forest
compartments within Hayami Forest increased (Figure 1).
Stand density within Hayami Forest was lower than forestry
association of Kashimo and prefectural forest of Aichi, indicat-
ing that the management of Hayami Forest maintains low stand
density in accordance with its forest management plan.
Number of Species
The total number of species peaked at a forest age of 49. Af-
ter this age, species number declined with forest age (Figure 2).
However, the total number of species did not largely differ
among forest ages. On the other hand, when considering layer
structure, the number of trees located lower in the canopy de-
creased with age, whereas the number of trees at intermediate
levels increased with age. After age 67, an upper layer began to
form, indicating that layer composition becomes more complex
as the forest matures. In particular, layer composition within
forests at age 99 approaches that of natural forests.
Figure 1.
Forest age and stand density.
0
2
4
6
8
10
12
14
16
18
21496799Natural forest
The number of species
Forest age
Upper layer
Middle layer
Lower layer
Figure 2.
Forest age and number of species.

S. KOSAKA, Y. YAMADA
The number of species is an effective index for forest man-
agement, as species richness is a good indicator of current for
est conditions. However, the evenness of species must also be
considered. Furthermore, the number of species tends to in-
crease as plot size increases.
Population Size
Although population size exhibited a pattern similar to the
number of species, the overall trend was different (Figure 3).
Compared to the number of species, the proportion of lower-
layer trees increased within compartments that harbor large po-
pulation sizes. Therefore, if the diversity of broadleaf trees is
evaluated using population size, lower-layer trees are relatively
dominant to middle and upper-layer trees.
The population size offers the advantage of assessing even-
ness between species. However, when several species are co-
dominant, the index will overestimate the importance of those
species.
Proportion of BA
Planted trees accounted for 88% - 99% of the proportion of
BA at all ages of forests, as the study was located within an
artificial forest (Figure 4).
Broadleaf trees clearly continue to grow as the forest ages, as
the dominance of broadleaf trees and the proportion of middle-
and upper-layer trees increases with forest maturation. Because
the proportion of BA is calculated from the sum of BA,
lower-layer trees that exhibit low BA dominance will decrease
even if the population size is large. In contrast, middle- and
0
20
40
60
80
100
120
140
160
21496799Natural forest
The Population size
Forest a
g
e
Upper layer
Middle layer
Lower layer
Figure 3.
Forest age and population size.
0%
2%
4%
6%
8%
10%
12%
21 49 67 99
The proportion of BA
Forest age
Upper layer
Middle layer
Lower layer
Figure 4.
Forest age and proportion of BA.
upper-layer trees that exhibit high BA dominance will be
abundant even if the population size is small. Considering this,
the proportion of BA serves as an index that expresses the
dominance of each layer and thus differs from the number of
species. In addition, the equality of species can be accessed
from this index in a manner different from population size.
However, high dominance does not always indicate high diver-
sity.
Species Diversity Index
All of the species diversity indices exhibited maximum val-
ues at a compartment age of 21, in which both the number of
species and population size were lowest (Figure 5).
On the other hand, compartments of age 67, in which popu-
lation size was largest, exhibited the lowest species diversity.
These results suggest that evaluations using species diversity
indices may be erroneous. In Hayami Forest, each compartment
age varied little in species number, although population size
varied greatly. Because species diversity indices are calculated
using combinatorics, if species numbers vary little, plots with
large populations will exhibit high values of species diversity.
Species diversity indices offer the advantage that results are
easy to understand and to compare, as the result is just one
number. However, the validity of the results must be assessed
using the number of species or population size. Therefore, us-
ing species diversity indices alone is not a recommended ap-
proach.
Evaluati on Using LUDI
The results of the four indices used to evaluate the diversity
of broadleaf trees and the age of forests were used to evaluate
the current distribution of compartments for Wcj. As a result,
maximum M' was the number of species (Table 1) because the
Figure 5.
Forest age and species diversity indices.
Table 1.
Results of LUDI.
Wcj M' M'/M1max
Forest age 3.262 0.393
Number of species 5.214 0.628
Population size 3.816 0.459
An inverse logarithm Simpson index 3.928 0.473
BA 3.577 0.431
1 6.710 0.808
M1max 0.000 -
64

S. KOSAKA, Y. YAMADA
number of species attained a high value regardless of forest age.
On the other hand, other indices were almost equal in value for
M' and were lower than that of the number of species. These
indices exhibited low overall values because they were also low
at the compartment level. However, the overall value of the
LUDI cannot be determined by M' alone.
suggesting that the current diversity of species is ensured at a
certain level. The value of M'/M1max when Wcj was 1 was
0.808. Because the value of M' when Wcj is 1 represents the
distribution of compartments, this value suggests a high evalua-
tion of the distribution of compartments. Furthermore, diversity
at the basin scale will be enhanced by declines in old forests
(age 39 - 99) and increases in young forests (age 22 - 38), ac-
cording to this analysis.
Therefore, to determine the maximum LUDI, we randomized
the grouping of compartments, with the qualifications that the
area, perimeter, and placement would not change and Wcj
would be fixed at 1 (i.e., no weighting). We then calculated
M1max for the maximum LUDI using 500 randomizations. The
M1max results suggested that the ideal diversity of land use
occurs at the basin scale. We also calculated M/M1max; that is,
how much M' contributed to M1max. Furthermore, the ideal
can easily be determined by depicting the results using GIS
(Figures 6 and 7).
Originally, the LUDI was used as an index to evaluate land-
use diversity and not for the evaluation of broadleaf tree diver-
sity. However, by using the results of the four indices for Wcj,
it is possible to evaluate diversity. Furthermore, this approach
allows us to determine what proportion of M1max was achi-
eved by M' by calculating M'/M1max. Using this index, the
LUDI can be used as an index to evaluate the diversity of broad-
leaf trees. Furthermore, the LUDI can be employed by forest
managers to determine the ideal distribution of compartments.
One potential issue is that the method used to calculate maxi-
mum LUDI in this paper involved several qualifications; there-
fore, the results of LUDI alone are not adequate for designing a
sustainable forest management approach.
The M'/M1max of the number of species was high at 0.628,
Conclusion
Our results demonstrated that all tested indices were similar
in their effectiveness, as they each evaluate different aspects of
diversity. Moreover, we determined that the diversity of broad-
leaf trees at the basin scale can be evaluated using the LUDI.
However, results obtained using individual indices must be
evaluated with caution. Another issue is that we only used data
for Chamaecyparis obtusa in Hayami Forest. It is unknown
whether similar results would be obtained if data were used for
forests of Chamaecyparis japonica and Larix leptolepis or for
forests with an insufficient management regime. Future re-
search should collect data within forests other than those of
Chamaecyparis obtusa.
Although each index offers advantages and disadvantages,
we found that the diversity of broadleaf trees at the basin scale
was most effectively evaluated using these indices in combina-
tion. Alternatively, a method could be developed to use all in-
dices in one model. We hope that this topic will be further ex-
plored and clarified through interdisciplinary research.
Figure 6.
The present distribution of compartments depicted using
GIS.
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Figure 7.
Results of the LUDI depicted using GIS.