Distribution and Abundance of Ground Vegetation in Traditional Gold Mining
Area of Sekotong, West Lombok, West Nusa Tenggara**
Retno P. Sancayaningsih*, S.H. Susanto, Purnomo, and A.H. Umam
Faculty of Biology, Universitas Gadjah Mada Jl. TenikaSelatan, Sekip Utara, Yogyakarta 55281, Indonesia * e-mail:retpeni@ugm.ac.id; retpeni@yahoo.com
Abstract
Gold mining activity often destroys tropical rain forest ecosystem, especially gold mining area that has not been managed professionally. Sekotong is one of gold mining areas that some illegal traditional gold mining, so called PETI, had appeared agrressively lately. The miners used mercury for their mining processes. The aims of the study were to examine the effect of mercury to the distribution and abundance of ground vegetation and the response of the community to mercury pollution in this area. The study was conducted in three locations of Sekotong area: Simba reserved forest, Selodong, and Pelangan sub-watersheds. Vegetation communities were taken randomly by using the 1 x 1 m2
quadrat method. Sixty nine of quadrat plots were taken from several study sites with randomly stratified strucuture. In addition, mercury concentration in plants leaves and soils, and also some physicochemistry of soils were also taken. Morphometric measurements of leaves taken from the most widely distributed plants, Eupatorium inulifolium, were also performed from each study sites. The results of the study showed that two grasses genera of Cynodon dactylon dominated the quarry mining area of Selodong by 36.4 m-2, and Ischaemum sp. dominated quarry in Pelangan by 25.1 m-2.
Likewise, Eupatorium inulifolium dominated in the forest reserved area by 32.1 m-2. Mercury content
in the quarry at Pelangan (184,3 ppb) was higher than in Selodong (39,7 ppb) followed the number of PETI which was 628 in Pelangan comparred to 274 in Selodong respectively. Eupatorium inulifolium is a mercury hyper accumulator plant, with the ability to absorb 100 times mercury higher than in soils. Ordination analysis showed that eventhough there were 3 groups of vegetations, the biggest group was vegetation that responsed to Pelangan mercury polluted condition, which was in a physiological stress condition. This conclussion was also supported by the reality that leaves and stems of the most distributed species was smaller size than that grown in Selodong or in forest reserved area.
Introduction
Gold mining activity often destroys tropical rain forest ecosystem. The area of Sekotong, West Lombok is one of the gold-rich region in Indonesia. Lately, an illegal traditional gold mining called PETI has appeared in this region. This mining uses mercury in its process. According to Butler (2010), for extracting the gold from the big stone, it is used sluice box (gelondong) which contains mercury to collect the gold. In Indonesia, the exploration for gold mining are taking place by many companies such as PT Newmont in Sumbawa Barat, PT Freeport in West Papua, PT East Asia Mineral Corporation in Aceh and PT Indotan Inc. in West Lombok. The traditional gold mining is also being conducted in some areas of Indonesia such as Kalimantan, Aceh, and Lombok.
Sekotong area is an area that has been opened for the benefit of traditional gold mining lately. The process of plant succession occurred very fast in this area, characterized by the turn of the life form of grass and herb into a shrub life form in Simba reserve forest. A very high content of mercury can cause damage to the body of organisms within a certain period of time and this also affects the ground vegetation surrounding the gold mining areas. Mercury hyper accumulator plants can survive and distribute widely in the area of mercury contaminated like Sekotong. There are problems arise in this study as follows: How does mercury from PETI change the distribution and abundance of ground vegetation in the area of Sekotong? Is there any mercury hyper accumulator species? How are the effects of mercury polluted atmosphere to the growth of well adapted species in this area? The aims of the study were to examine the effect of mercury to the distribution and abundance of ground vegetation and the response of the well adapted plant community to mercury pollution in this area.
Materials and methods
This research was conducted at 3 location of Sekotong; Simba reserve forest, Selodong, and Pelangan in October 2009. Ground vegetation communities were taken by using the purposive random sampling using quadrat plot methods (1 x 1 m2). Sixty nine of plots were analyzed. In addition,
we also performed morphometric growth measurements of Eupatorium inulifolium, mercury content in the soils close to the quarries and also in Eupatorium inulifolium leaves. Measurement of several physicochemical factors such as soil temperature, air temperature, soil pH, and soil humidity were also performed. Species identification of ground vegetation communities were carried out by using identification book of Backer (1973) and Steenis (1975). All vegetation analysis parameters were calculated and ordination analysis was used to group all plots characteristics (Barbour, 1987, Krebs, 2009).
Results and discussion
The results of the study showed that two grasses genera of Cynodon dactylon dominated the quarry mining area of Selodong by 36.4 m-2, and Ischaemum sp. dominated quarry in Pelangan by
25.1 m-2. Likewise of the shrub life form, Eupatorium inulifolium dominated in the forest reserved area
at Simba by 32.1 m-2.
Grass life form can dominate the Sekotong region because the grass has stolons, rhizomes or tuber roots. In addition, grasses have an effective propagule both vegetative and generative reproductions. Generatively, it reproduces very large number of seeds, and its fine hairs are easily distributes them, while vegetatively it forms stolon (Johnny, 2006). In contrast to the life form of grass and herb, shrub life form plants rarely have rhizomes therefore it reproduces generatively and this is less effective. Eupatorium inulifolium is an invasive species that colonizes open areas quickly. Historically, Simba reserve forest was an abandoned land which had been originally used as farm land by local community more than fifty years ago.
Ordination analysis of plants from 69 quadrat plots showed that there were 3 groups: A group (17 plots) belong to forest station, B group (12 plots) contained of forest and some plots from Selindungan and Pelangan stations, and C group (40 plots) contained of mostly plots from Pelangan and Selindungan stations (Fig. 1.). This grouping corresponds to the characteristics of each plots, the diversity and abundance of plant species, in response to the environmental condition
Fig.1. Ordination analysis results
Of that analysis, can be deducted that almost all studied plots in group B and C ( 75 %) had vegetation characters (species and their abundances) showed that were effected by mercury pollutant, while only 80% of plots in the Simba forest were far diffferent from those plant diversities and abundances in the gold mining area of Pelangan and Selodong.
distribution was less frequent in this area. However, species that dominated each station of studies such as Cynodon dactylon in Selodong, Ischaemum sp.2 in Pelangan, and Eupatorium inulifolium in reserve forests had clumped distribution pattern. Actually, clumped distribution can increase intra species competition, but the disadvantages are often compensated by an advantage that the plants that grow in groups can organize microclimate around as needed (Indriyanto, 2006).
The most invasive species Eupatorium inulifolium that found in three study areas was observed in its ability to absorb mercury from soils, and also their leaves measurements as its consequences to adapt to its heavy mercury polluted environment. Mercury content in the quarry at Pelangan was 184,3 ppb, while in Selodong was 39,7 ppb. This high content of mercury in quarry soils corresponded to the number of PETI, which was 628 in Pelangan comparred to 274 in Selodong respectively. The content of mercury in Eupatorium inulifolium leaves found in Pelangan was very high, reaching up to 2.8 ppm, while mercury content in leaves grown in Simba forest was only 28,9 ppb. This was almost 100 times higher mercury content in gold mining areas comparred to Simba forest as the control area that can be called as a hyperaccumulator (Butler, 2010). In the control area, plant leaves were also contaminated with mercury distributed through the air.
In terms of leaves measurements, it showed that there was a decrese in leaf size and stem diameter, especially plant found in Pelangan stations (Table 1.). This indicates that there was physiological stress of the species, and plant development was disturbed.
Table 1. Morphometry measurement of E. inulifolium
Station Morphometrical measurement (cm) of E. inulifolium Leaf length Leaf width Stem diameter
Nature forest 10.9 ± 1.7 6.8 ± 1.3 0.44
Selodong 10.4 ± 0.6 6.4 ± 0.3 0.34
Pelangan 9.9 ± 1.8 5.2 ± 1.7 0.20
Mercury can inhibit photosynthetic reactions causing metabolic disorders. As a result, plants may become stunted, yellowing leaves, and stems are not sturdy. The existence of mercury pollutant gives a sub lethal effect for which has mercury hyper accumulator character. Therefore it can be estimated that the area was heavily contaminated with mercury will cause the mercury content of the leaves also become increasingly high, as happened in the Pelangan.
Two genera of grasses Cynodon and Ischaemum dominated the quarry mining area. At Selodong area dominated by Cynodon dactylon by 36.4 m-2, and Ischaemum sp. dominated quarry in
Pelangan area by 25.1 m-2. Likewise of the shrub life form, Eupatorium inulifolium dominated in the
forest reserved area at Simba by 32.1 m-2.
Eupatorium inulifolium is a mercury hyper accumulator plant, because it can absorb mercury from soil and air more than two other life forms, grasses and herbs. The content of mercury in Eupatorium inulifolium leaves found very high in Pelangan, reaching up to 2.8 ppm, while mercury contents in the quarry soils at Pelangan was only 184,3 ppb, and this was higher than that in Selodong (39,7 ppb).
References
Backer, C. A. 1973. Atlas of 220 Weeds of Sugar-Cane Fields in Java. Ysel Press. Deventer.
Barbour, M. G., J. H. Burk and W. D. Pitts. 1987. Terrestrial plant ecology. 2th edition. Benjamin
Cummings, USA. pp. 51-54, 164
Butler, R.A. 2010. Environmental Impact of Mining in the Rainforest. Accessed on 24th January 2010,
from Mongabay.com / A Place Out of Time: Tropical Rainforests and the Perils They Face. Website: http://rainforests.mongabay.com/0808.htm
Indriyanto. 2006. Ekologi Hutan. PT. Bumi Aksara, Jakarta. p. 82, 83
Johnny, M. 2006. Dasar-Dasar Mata Kuliah Gulma di Jurusan Biologi. Department of Biology, Faculty of Mathematics and Natural Science, Universitas Udayana
Krebs, C.J. 2009. Ecology the experimental analysis of distribution and abundance. 6th edition.
Benjamin Cummings, Pearson. USA. pp. 85-94, 118, 569
