0651-B1

Classification of vegetation ecological groups and their Relations with physiographic characteristics.

Esmaiel Kouhgardi, Gh. Zahedi Amiri and A.Pazira ¹

Abstract

In order to identify the plant ecological groups and determining their distribution pattern with physiographic characteristic, this research was carried out in an area of 124 hectare at altitude of 80 - 1200 meter from sea level, in Bousher province, south of Iran. To identify and classification of vegetation cover, 248 grid permanent plots with 256 square meter for tree - shrub layer and 64 square meter for herbal layer were chosen on of basis the Brun - Blanquet combined cover - abundance scale.The phytosociologycal study was carried out in last parts of growing season (March and April 2002) in two distinct layer (tree - shrub and herb cover). Clustering method used in order to vegetation analysis. Classification analysis was done using TWINSPAN to identify plant ecological groups. GIS application was used to develop mapping plant ecological groups and Digital Elevation Model (DEM). Comparison among plants ecological groups, slope, aspect and elevation map were shown a significant relation between vegetation and elevation, but there was not a significant relation among vegetation and slope and aspect.

Introduction

Phytosociology is one of the plant ecology that get through to recognition and discription of species and plant community.Study about phytosociology show that there are deep relative between plant and environmental conditions.The species that have similar ecological requerment or similar "Niche"collected with together and made plant ecological groups. Plant community is basic concept in the study of vegetation cover and it used ferst time by Hembold(1805).There are many methods for discription of community charactrestics(Cragg,1962),that among them can mention following methods:Systematic method (Broun-Blanquet),Typological concept (Tansley,1920),Individualistic continuum cocept(Clements,1939)and Exclusiveof communities concept(Walter,1971).

According to above methods, many research achieved in the world and gradually caused development of phytosociology, so that nowadays use of computer programs such as: TWINSPAN1, CCA2, DCA3, PCA4, have increased accuracy and velocity of studies and cause to obtain have better analysis from relations between plant elements and environmental conditions.

1. Two-way indicator species analysis.
2. Canonical correspondence analysis.
3. Detrended correspondence analysis.
4. Principal component analys

Materials and Methods

The study area have 124 hectare at the altitude of 80-1200 meter from sea level, in longitudes 52 30 E and latitudes 27 38 N is located in Boushehr province,south of Iran.

For showing weather information used data of Dayer station(12 meter from sea level) and Kangan station (655 meter from sea level) (table 1).

For sampling ; Permanent square plots were distributed by systematic random grid. The grid size were 100 m (Parallel with elevation contour) * 50 m (vertical on elevation contour) and point of ribs confluence, selected as plot center.In order to determining size of plots were used from " Minimal area " (Nested plots) method, plot size determined for tree-shrub layer 256 square meter and for herbal layer 64 square meter.According to area and size, 248 grid permanent plots distributed in area and studied present or absent of species and abundance factor of vegetation cover in these plots,by use of the Broun-Blanquet combined cover-aboundance scale(Table2). In order to analysing of vegetation cover used from Clustering analysis. Clustering analysis carried out with TWINSPAN program (Hill, 1979).

Table 1. Weather information of study area.

Results

Vegetation cover analysis was carried out in 7 divisions in both tree-shrub layer and herbal layer and have recognized 4 ecological groups. (after that, the igen value was not significant) then indicator species in 4 groups and also plot numbers of each group identified (Figure 1 and 2).

In order to study the ecological similarity between ecological groups used from Sarson Index (Table 3and 4). Excess of Sarson Index between 1 and 2 groups in both layer showed that these groups are very similar,so mixed and identified with one groups (Group 1).

With due attention to distinguished plots of each groups, the map of these ecological groups are provided. For providing physiographic characteristic map(aspect,slope,elevation classes), is used from Digital Elevation Model (DEM). prepared maps reclased to different classes,then determined the correlation of each reclased maps with vegetation ecological maps and determined the best of classification degrees for each physiographic factors (Figure 3, 4 and 5).

The correlation test showed that altitude from sea level (abs) factor had high correlation with vegetation cover changes(more than 90%),slope (less than 30%) and aspect(less than 5%) factors had low correlation with vegetation cover changes.

According to above cases, the mixed map of vegetation cover and altitude (abs) developed. this map was include the unites that shows the position of ecological groups of both layer(tree-shrub layer and herbal layer) in relation to latitudinal changes of the study area (Figure 6 and 7).

Table 2. Broun-Blanquet combined cover-aboundance scale.

Table 3. Percentage of Sorensen index in ecological groups of tree-shrub layer.

Table 4. Percentage of Sorensen index in ecological groups of herbal layer.

Figure 1. Map of vegetation ecological groups for herbal layer.

Figure 2. Map of vegetation ecological groups for tree-shrub layer.

Figure 3. Hypsometric map of the study area.

Figure 4. Aspect map of the study area.

Figure 5. Slope map of the study area.

Figure 6. Combined map of vegetation cover and altitude from sea level for herbal layer.

Figure 7. Combined map of vegetation cover and altitude from sea level for herbal layer.

Discussion

According to mixed map of altitude-vegetation cover is distinguished that in the herbal layer ; the group 1 starts from coastal area up to 900m from sea layer,the group 2 starts from 300m up to uper part of altitudes and the group 3 starts from 600m up to uper part of altitudes.

These results show the groups 1 and 2 have extensive distribution in the study area and have excessive tolerance range than altitude changes of sea level, but the group3 have distribution only the upper half of altitudes, also from sea level up to 300 meter is specially adapted for group1 and there are not other groups in these section. All of groups (1, 2 and 3) there are in range of 600-900 meter from sea level.

In tree-shrub layer; group1 starts from 600 meter up to upper most altitude boundaries. Thegroup2 have distribution only in 300-600 meter. The group3 starts from sea level and distributions to 900 meter from sea level.

These results show that from coast to 300 meter from sea level is only specially adapted for group3 and other groups there are not in this section. Also group3 have over tolerance range than altitudes changes, but the group1 is fined only in upper half of altitudes. The altitudinal class of 300-600 meter is common between group2 and 3, and the altitudinal class of 600-900 meter is common between group3 and 1, and altitudes more than 900 meter is specially adapted for group 1.

We appreciate from all persons who have had cooperation with us.

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¹ Tehran university, Faculty of Natural Resources - Karaj. Iran
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