Status of Soil Fertility at Sloping Land Cassava Cultivation in Protected Area of Mount Muria, Central Java
INAFOR 11G-054
INTERNATIONAL CONFERENCE OF INDONESIAN FORESTRY
RESEARCHERS (INAFOR)
Section G Forest Environment and Climate Change
Status of Soil Fertility at Sloping Land Cassava Cultivation in Protected
Area of Mount Muria, Central Java
Dona Octavia
Forestry Research Institute of Surakarta
Jl. Ahmad Yani, Pabelan, Surakarta, 57102, INDONESIA
Paper prepared for The First International Conference of Indonesian Forestry Researchers (INAFOR)
Bogor, 5 – 7 December 2011
INAFOR SECRETARIAT Sub Division of Dissemination, Publication and Library
FORESTRY RESEARCH AND DEVELOPMENT AGENCY Jl. Gunung Batu 5, Bogor 16610
Status of Soil Fertility at Sloping Land Cassava Cultivation in Protected
Area of Mount Muria, Central Java
Dona Octavia
Forestry Research Institute of Surakarta
Jl. Ahmad Yani, Pabelan, Surakarta, 57102, INDONESIA
ABSTRACTInappropriate land utilization and management practices that do not consider the aspects of soil conservation will lead into land degradation. The degradation will have implications for increasing critical land inside and outside the forest area. This paper aims to analyze soil fertility at rehabilitation demonstration plots in the protected area of Mount Muria, which is sloping land for cultivation of cassava. Soil sampling conducted in 12 points to represent an area of 5 hectare demonstration plot. The results showed arrays of variation in soil texture that ranges from sandy loam to heavy clay. Soil was classified as slightly acid to acid (pH H O) which has low organic 2 matter content (< 2%). The soil has low cation exchange capacity and very low nitrogen availability. The land is basically no longer appropriate for cassava cultivation. Several efforts are needed to increase soil fertility and decrease erosion, including planting pioneer trees of legume as green manure as well as applying legumes cover crops and manure.
Keywords: Soil degradation, soil organic matter, land utilization
1. INTRODUCTION
Bare land with no trees and cover crops increase the chances of soil erosion which can ultimately reduce the soil fertility physically, chemically and also biologically. Inappropriate land utilization and management practices without considering the aspects of soil conservation will lead to land degradation. Soil erosion was allegedly increased the extent of degraded land. Critical land in the mountainous region is often found in areas where forests have been damaged, especially the steep sloping areas and poor of cover plant. It generally occurs due to landslides and erosion that result into peeling up of upper soil layers and often opened up the layers into a rocky form.
The farmers Mount Muria perceived that continuous decreased of cassava production in the area was obviousely as result of degraded land. Soil organic matter (SOM) is a main key to support plant growth. The low organic matter and other important nutrients on degraded land demanded vegetative rehabilitation efforts. This can be done particularly by ‗fertilizer tree system‘ through the planting of the legume tree including Falcataria moluccana , acting as a continuous green manure as well as planting leguminous cover crops and applying manure to improve soil fertility and reduce erosion. By knowing the status of soil fertility on a critical land, then the appropriate handling treatment to the requirements of land recovery can be pursued more thoroughly.
This paper aims to analyze soil fertility at the area of demonstration plots for rehabilitation in the protected area of Mount Muria. The plots are located at the sloping area and cultivated with . The cultivation will be used as an initial description for applying land recovery.
2. EXPERIMENTAL METHODS
This research was conducted in March 2011 at the village of Gunungsari, Tlogowungu District, Pati Regency, Central Java. The research has undertaken to area approximately 5 ha which are considered as private lands inside the protected area of Mount Muria. Study area lies in altitude between 500-600 m above sea level. The everage monthly rainfall during the plant growth is 129 mm, which occurs primarily during November-Maret 2011. Mean temperature is 27 C which ranges from 22 C (minimum) to 36 C (maximum). The average relative humidity varies between 63% and 80%.
The soils in the study area are classified as Latosols and Red Yellow Mediteran. Soil texture is dominated by clay that varies from sandy loam to heavy clay. This research applies four model plots of tree planting combination as a treatment including a control plot. The four models were: 1). Plot dominated by sengon (Falcataria moluccana), 2). Plot dominated by Jabon (Anthocepalus cadamba), 3). Plot dominated by combination of Sengon and Jabon, and 4) Plot control (no planting treatment). Soil sampling was conducted in 12 points of each model plot to represent an area of 5 hectare demonstration plot. The twelve soil samples were taken on a topsoil layer in 30 cm depth. It was conducted prior to do planting based on models that will be applied. Analysis of soil physical and chemical properties include soil texture, pH, organic matter content, carbon (C), nitrogen (N) total, Posphate (P) available, Potassium (K) available and Cation Exchange Capacity (CEC).
3. RESULTS AND DISCUSSION
The results (Table 1) showed variation on soild texture exists, from sandy loam to heavy clay. Soil is classified as slightly acid to acid (pH H O) which has low organic matter content 2 (mostly < 2%). The soil has low cation exchange capacity and very low nitrogen availability. K- available varies from ‗low to high‘, as well as P-available, that ranges from very low to very high.
However, in general P available is very high (> 46 ppm). Table 1. Status of Soil fertility at demonstration plots
pH pH C SOM N total P-available K-available CEC Soil Type Code H 2 O KCl % % % ppm me/100 g T1
5.44
4.32
0.74
1.27
0.04
9.06
0.20 10.91 heavy clay T2
5.02
3.65
0.81
1.40
0.08
4.87
0.36 7.71 clay loam T3
4.90
3.68
0.91
1.56
0.09
55.05
0.65 8.23 clay T4
5.98
4.30
1.13
1.95 0.08 167.95
0.95 5.18 sandy clay T5
5.56
4.29
0.97
1.68 0.07 103.48
0.16 6.85 clay loam T6
5.04
3.84
0.82
1.41 0.08 100.68
0.23 8.16 loam T7
5.71
4.25
0.74
1.27 0.06 178.33
0.41 7.77 loam T8
5.27
4.18
1.39
2.40 0.09 200.85
0.43 7.12 clay loam T9
5.22
3.85
0.90
1.56 0.07 101.04
0.15 9.44 clay T10
5.13
3.62
0.80
1.34
0.08
4.85
0.31 7.70 clay loam T11
5.96
4.71
1.07
1.84
0.11
35.14
1.14 6.10 clay loam T12
5.87
3.96
0.95
1.63
0.10
38.19
0.66 7.64 clay
Remarks: T = Point of taken soil; C = Carbon; SOM = Soil Organic Matter; P = Phosphate; K = Kalium; CEC =
Cation Exchange CapacityTable 1 shows result of the analysis from demonstration plots around Mount Muria, that explain the plots have degraded as indicated by low content of C organic and organic matter (1- 2%) and very low soil N total content (mostly < 0.1%). The condition even worse, as being presented by low soil CEC (5-11 g me/100) and most of the soil are acidic. Due to this condition, the practice of total harvesting for cassava is no longer appropriate for cultivating sloping land at 9
- – 45%, as such practices will extract nutrients from the soils without returning back its fertility. As result of declining soil nutrients, planting cassava for income source that has become a community tradition in this region will require high inputs of organic matter.
indicator for soil quality. Gong et al. (2009) in a research at China proved that C and N contents
and also the total soil culturable microbial counts (including bacteria, fungi, and actinomycetes)
were highest in the Organic Manure treatment, while the unfertilizer treatment showed the lowest
value. Application of half organic manure with mineral fertilizer NPK significantly increased C
and N contents in soil in comparison with application of mineral fertilizer alone. Many studies
have shown that application of organic manure, either alone or in combination with mineral
fertilizers, is more effective in increasing SOM and its fractions than mineral fertilizers alone
(Gong et al., 2009).The availability of K and P that have been indicated to be in a range from ‗low to high‘ and from very low to very high were due to application of manure by land owners. General understanding says manure contains both nutrients of macro and micro, and this may explain high contain of P component that reaches >46 ppm, or it is available at the point of T3 up to T9 or between 55 and 220 ppm.
3.1 Maintenance of Soil Organic Matter for Physical, Chemical and Biological Soil
FertilityThe role of organic matter on physical soil fertility is to influence the formation of soil aggregates, which is important in the formation of soil structure in order to make it more crumbs. The role of organic matter on chemical soil fertility is to increase Cation Exchange Capacity, which has a behavior like
‗chellate‘ (binding), so that nutrients are not easily leached. Organic matter increases the water holding capacity to maintain soil humidity and improve soil permeability (Rosmarkam and Yuwono, 2002).
Table 1 show that soil was dominated by clay. The influence of organic matter on soil structure is closely related to soil texture. Organic matter applied on heavy clay soil leads to changes in soil structure, which was originally has strong and rough blocky structure into a more refined structure that make the soil easier to be cultivated. On the other hand, organic matter applied on sandy soil leads to changes in soil structure, which was originally has a single-grained structure into a blocky shape, thereby increasing the degree of structure and size of the aggregate (Scholes et al., 1994 in Atmojo, 2003). Furthermore, soil organic matter can alter soil structure, which was originally has no structure (solid) into crumbs (a better structure).
Organic matter may influence soil pH by increasing or decreasing soil acidity, depending on the maturity level of organic matter and the soil type. The role of organic matter on biological soil fertility is to increase the activity and populations of macro-and micro-organisms that play an important role in decomposition and mineralization of organic matter (Atmojo, 2003). This is because organic matter is a source of energy for them.
3.2 Organic Matter as A Source of Soil Nitrogen
One of the solution to improve soil fertility in the study area, it is necessary to establish legume trees plantation, they include Falcataria moluccana and other green manure tree such as
Leucaena leucocephala, Glericidia sepium and Calliandra calothyrsus. These three last mentioned plants
are also suitable as a hedge (in a hedgerow intercropping) which can be pruned regularly so that their litters are able to increase soil organic matter content. Planting of leguminous cover crops also play an important role in maintaining soil productivity (nutrient cycling) and reducing soil erosion. Pruned leaves and twigs could be a fodder for livestock or mulch matters which is rich of nitrogen as a source of organic matter. Organik matter or humus which is the result of decomposition of litter is one source of soil nitrogen (Tisdale et al., 1985).
In southern Africa, in response to the declining soil fertility and the negative effects that leads into food insecurity, fertilizer tree systems (FTS) were developed as technological innovation to help smallholder farmers to build soil organic matter and fertility in a sustainable manner (Ajayi et. al., 2011). Dropped leaf and twigs litter become the primary nitrogen cycle and other nutrients which are returned to the ground (Daniel et al., 1979).
3.3 Effect of Organic Matter on Soil pH
Table 1 shows the soil is generally clay-textured (loam to heavy clay) which has the level + of soil acidity (pH H O) slightly acid to acid. Conditions of pH KCl is lower than pH H O, that 2 2 indicates sufficient number of ions H . The ion causes soil acidity that adsorbed in soil colloid layer. Soil colloid is generally in the form of clay (colloidal inorganic) and humus (organic colloids). Dropped litter, especially leaf litter of F. moluccana which is rapidly decomposed and applied manure can help to increase soil pH. In one research, Octavia (2010) proved that soil N total has increased 13 % after applying of 105 g leaf litter of F. moluccana on soil medium of regosols. This study found that the soil given litter has a higher pH (average pH value of 6.22) than that with no litter (an average pH value of 6.14).
Chintu et al. (2004) also proved that leaf litter of F. moluccana can increase soil inorganic N and reduces soil acidity needed by crops including grains. They found that leaves of
F. moluccana
caused a marked significant reduction in soil acidity within the first 20 days after amendment. T he
potential usefulness of organic matters to raise pH and hence ameliorate heavy metal toxicity in
strongly weathered soils is quickly gaining recognition from several authors (Wong et al. 1998 in
Chintu, 2004).Applied manure was also able to reduce soil acidity. Octavia (2010) showed that soil acidity decreases (pH increases) compared to initial soil acidity before planting. The increase in soil pH, which was initially slightly acid to acid for all treatments that change into rather neutral (pH > 6), is likely to be caused by manure application. Manure from herbaceous livestock + 2+ 2+ contains higher Ca , Mg and K as grasses absorb more alkaline metal that will reduce soil acidity when it is decomposed. Atmojo (2003) suggested that the increase in soil pH will also occur if the organic matter has decomposed further (mature) because mineralized organic matter will release its minerals, in the form of base cations.
4. CONCLUSION
Low soil organic matter, soil organic carbon, cation exchange capacity and very low soil nitrogen are indicators for the poor soil quality that describes the low soil fertility on private land in protected areas of Mount Muria. Several efforts are needed to increase soil fertility and to decrease erosion including planting pioneer trees of legume as green manure as well as applying leguminous cover crops and manure.
REFERENCES
Ajayi, O C, F Place, F K Akinnifesi (2011): Agricultural success from Africa: the case of fertilizer tree systems in southern Africa (Malawi, Tanzania, Mozambique, Zambia and Zimbabwe).
International Journal of Agricultural Sustainability 9(1):129p.
Atmojo, S W (2003): Peranan Bahan Organik Terhadap Kesuburan Tanah dan Upaya Pengelolaannya. Pidato Pengukuhan Guru Besar Ilmu Kesuburan Tanah Fakultas Pertanian. Universitas Sebelas Maret. Surakarta.
Chintu, R, A R Zaharah and A K Wan Rasidah (2004): Decomposition and Nitrogen Release Patterns of Paraserianthes falcataria Tree Residues under Controlled Incubation." Agroforestry System 63:45-52.
Daniel, T W, J A Helm and F Baker (1987): Prinsip-prinsip Silvikultur. (D. Marsono, Penterj). Gadjah Mada University Press. Yogyakarta.
Gong, W, X Yan, J Wang, T Hu and Y Gong (2009): Long-term manure and fertilizer effects on
soil organic matter fractions and microbes under a wheat –maize cropping system in northern
China. Geoderma 149:318 –319.Octavia, D (2010): Kajian respon Padi Gogo (Oryza sativa L.) terhadap Perbedaan Intensitas Cahaya dan Masukan Serasah dengan Media Tanah Asal Hutan Rakyat Sengon. Thesis. Unpublished. Rosmarkam, A dan N W Yuwono (2002): Ilmu Kesuburan Tanah. Penerbit Kanisius. Yogyakarta. Tisdale, S L, W L Nelson and J D Beaton (1985): Soil Fertility and Fertilizer. Four Edition Mac Millan Publ. Co. Inc. New York.
INAFOR 11G-055
INTERNATIONAL CONFERENCE OF INDONESIAN FORESTRY
RESEARCHERS (INAFOR)
Section G Forest Environment and Climate Change
Species Richness and Composition of Vegetation in Logged Over Forest
PT. BFI SOTEK, East Kalimantan
1 2 Nurul Silva Lestari and Adi Susilo1 Dipterocarps Research Center, Jl. AW. Syahrani No. 68, Samarinda, East Kalimantan 75119, INDONESIA
1 Corresponding ema
The Center for Research and Development on Forest Conservation and Rehabilitation
Jl. Gunung Batu 5, Bogor 16610, INDONESIA
Paper prepared for The First International Conference of Indonesian Forestry Researchers (INAFOR)
Bogor, 5 – 7 December 2011
INAFOR SECRETARIAT Sub Division of Dissemination, Publication and Library
FORESTRY RESEARCH AND DEVELOPMENT AGENCY Jl. Gunung Batu 5, Bogor 16610
Species Richness and Composition of Vegetation in Logged Over Forest
PT. BFI SOTEK, East Kalimantan
1
2 1 Nurul Silva Lestari and Adi SusiloDipterocarps Research Center, Jl. AW. Syahrani No. 68, Samarinda, East Kalimantan 75119, INDONESIA
1 Corresponding emaThe Center for Research and Development on Forest Conservation and Rehabilitation
Jl. Gunung Batu 5, Bogor 16610, INDONESIA
ABSTRACTForest degradation due to timber harvesting generates ecological changing including biodiversity. This study investigated the impact of logging activities on species richness and composition of vegetation. Heavily degraded forest (recently logged, all commercial trees at dbh of >40 cm were cut), lightly degraded forest (old degraded forest, ready for the next cuting cycle), and nearby protected forest (as control) were sampled. Result showed that species richness in the heavily degraded forest is lowest in all size classes. The lightly degraded forest has the highest species richness in the seedlings, saplings and trees size classes. While the highest species richness of the poles was in the protected forest. Species density of saplings and trees were highest in the protected forest, seedlings were in the heavily degraded forest and poles were in the lightly degraded forest. Dipterocarps species as commercial timber has highest composition in the heavily degraded forest forest in seedlings and poles classes. Dipterocarps species composition of saplings was highest in the protected forest and trees were in the lightly degraded forest. The lightly degraded forest and protected forest have the most in common species. Vegetation assesment in logged over forest should be carried out periodically to verify the impact and determine the appropriate management intervention to support forest sustainability.
Keywords: Species richness, composition, vegetation, logged over forest
1. INTRODUCTION
Indonesia has extensive degraded lands arising from intensive exploitation of forest resources in recent decades (Kartawinata et al, 2001). In 1990, degraded forest due to timber harvesting covered 22.44 million ha. The acreage of logged over area grew into 29.29 million ha in 2000 and climbed up to 38.55 ha by 2005 (Ekadinata et al, 2011). Forest harvesting can be a major cause of anthropogenic disturbance for the forests. The most direct impacts of harvesting are clearly on the tree species being harvested. Harvesting may also impact on other species. If trees are felled, this can cause a significant damage to other trees and the understorey (Newton, 2007). Direct damage in logged forest depends on many factors, including, soil type and variety of techniques intended to reduce damage, but the most important variable is logging intensity. The damage that is caused by logging activities includes dead and injured remaining trees, large canopy opening that encourage the growth of climbers and pioneers, as well as increasing fire risk, and soil compaction, leading to decreased infiltration, increased erosion and slow regeneration (Corlett, 2009).
Studies about ecological impact on logged over forest have been carried out in several countries (Bischoff et al., 2005; Canon et al., 1998; Ho et al., 2004; Parotta et al., 2002; Tran et al., 2005). However, study on the vegetation impact for Indonesia‘s tropical forest is still rare. Most studies of the botanical impact of logging in lowland dipterocarps have been done for only 1-6 years after logging, or in old logged-over secondary forests without post-logging management, so the long term impacts of present-day logging practices are largely unknown (Bischoff et al., 2005).
Ecological aspect is one of the issue in sustainable forest management. Several institutions take biodiversity aspect as criteria on sustainable forest management implementation. According to ITTO (1998), this criterion relates to the conservation and maintenance of biological diversity, including ecosystem, species, and genetic diversity. Biological diversity can also be conserved in forests managed for other purposes, such as for production, through the application of appropriate management practices. Forest Stewardship Council (1998) principles and criteria (1998) mentions that Forest management shall conserve biological diversity and its associated values. Forest management should also include the research and data collection needed to monitor environmental and social impacts of harvesting. Meanwhile, Ministry of Forestry has been considering biodiversity as indicator to verify and asses the performance of sustainable forest management implementation in production forest.
Understanding the impact of logged over forest is important to determine the appropriate management for sustainable timber production in natural forest. This study investigates the logging impact on vegetation by assessing the differences of species richness and composition of vegetation between heavily degraded forest and lightly degraded forest comparing to protected forest.
2. METHODS
2.1 Study Site
Research was conducted at PT. BFI Sotek, East Kalimantan, geographically located between 116 ˚ 01‘ - 116˚ 45‘ E and 00˚ 42‘ - 01˚ 18‘ S. Administratively the area is situated in the three (3) districts namely Pasir (21%), Penajam Paser Utara (39%), and Kutai Barat District (40%).
Behaviour scale
Figure 1: Study site The company has been operating since 1969 in a lowland forest dominated by
Dipterocarps species. Research plots were laid in the forest areas that have been harvested. We also established plot in Mount Meratus protected forest adjacent to PT. BFI Sotek. The site has mean monthly temperatures 26.4 - 27 ˚C and mean annual precipitation of 2.709 mm. The study site lies at 300-400 m above the sea level. Data were collected in June-July 2011.
2.2 Data Collection
Sampling was carried out in three forest types – heavily degraded forest, lightly degraded forest, and protected forest. These forest types are defined as:
Heavily degraded forest – recently logged, all commercial trees of dbh > 40 cm were cut
- – Old degraded forest, ready for the next cutting cycle - Lightly degraded forest Protected forest - prohibited logged forest, as control
- Vegetation data was collected using line transect. It measures 100x20 m laid purposively in the heavily degraded forest and protected forest due to the site condition in those forest types is not uniform. Meanwhile, the line transect were laid randomly in the lightly degraded forest. As many as 2 transect were made in each forest types. The transect was divided into five plots measuring 20x20 m. Inside these plots the sub plots of 2x2 m, 5x5 m and 10x10 m were made. Vegetation data was collected in the each size class. Data of seedlings (height < 2m) were taken at 2x2 m subplots, saplings (height >2m - dbh<10 cm) at 5x5 m subplots, poles (10 cm≤dbh<20cm) at 10x10 m subplots and the trees size class (dbh≥ 20 cm) were at 20x20 m plots. For each plots and subplots, we recorded name on the species, number of individuals, dbh and tree height (Soerianegara and Indrawan, 1998).
2.3 Data Analysis
Species richness for all size classes was analyzed using rarefaction. Rarefaction is a statistical method for estimating the number of species expected in a random sample of individuals taken from a collection. Rarefaction answers this question: if the sample had consisted of n individuals (n<N), what number of species (s) would likely have been seen? Note that if the total sample has S species and N individuals, the rarefied sample must always have n < N and s < S (Krebs, 2003). The calculation uses ecological method software developed by Krebs.
In order to determine species density for each size class, we devided number of individual 2 recorded by sample area, resulting the number of individual/m (for seedlings and saplings) and
- – the number of individual/ha (for poles and trees). The species were classified into two category Dipterocarps species and non Dipterocarps species. Then we calculated the proportion of the individual number of Dipterocarps species and non Dipterocarps species against the total individual number recorded.
Similarity within species among all sampled sites were calculated by using the Morosita- Horn Index using EstimateS 750 software. This index is not strongly influenced by species richness and sample size (Maguran, 2003). The collected data were tested for significance and correlation with chi square and Pearson product-moment correlation test (Minitab 16).
3. RESULT AND DISCUSSION
3.1 Results
3.1.1 Species Richness
A total of 171 species was collected from three different forest types. Rarefaction analysis showed that Lightly degraded forest and Protected forest have the highest number of species (30 species) with 75 individual seedlings being observed. Heavily degraded forest have the lowest species richness. For observation in all sites, at least 25 species were expected to be found if we collect 75 individuals. The difference in species richness was not significant among the sites (p=0.709).
The analysis for saplings shows, Lightly degraded forest has the highest species richness as well (48 species) with 67 individual observed. The heavily degraded forest have the lowest species richness. There was no significant difference in species richness of the saplings (p= 0.303). Meanwhile in the poles size class, the species richness in all sites were almost similar (13 species) for 17 individual observed. The difference in species richness of poles was not significant between the sites (p= 0.984).The species richness of the trees was highest in the lightly degraded forest (38 species) and lowest in the heavily degraded forest for 52 individual observed. The species richness of the trees was not significantly different between all forest types (p= 0.676).
Sp ec ies r ichn es s Species Richness of Poles
13 13,21 13,89
5
10
15
20
25
30
35
40
45
50 Heavily Degraded Forest Lightly
Degraded Forest Protected Forest
31 38,26 35,93
Degraded Forest Protected Forest
5
10
15
20
25
30
35
40
45
50 Heavily Degraded Forest Lightly
Degraded Forest Protected Forest
Sp ec ies r ichn es s Species Richness of Trees
Sp ec ies r ichn es s Species Richness of Saplings
50 Heavily Degraded Forest Lightly
Figure 2: Species richness for each size of forest class
40
The density of seedlings was highest in the heavily degraded forest (2.25 individual/m 2 ).
In contrast, the density of seedlings was lowest in the lightly degraded forest (1.18 individual/m 2 ).
In the saplings class, the densities of all sites was almost similar with the highest one in the protected forest (0.152 individual/m 2 ). The density of poles was highest in the lightly degraded forest (300 individual/ha) and lowest in the heavily degraded forest. While in the trees size class, the density was highest in the protected forest (157.5 individual/ha) and lowest in the lightly degraded forest (120 individual/ha). There was no significant difference in density between seedings, saplings and trees. The difference in species density of poles was significant between the sites (p< 0.05).
25,00 30,79
30
5
10
15
20
25
30
35
45
45
50 Heavily Degraded Forest Lightly
Degraded Forest Protected Forest
Sp ec ies r ichn es s Species Richness of Seedlings 32,31 45,85
38
5
10
15
20
25
30
35
40
3.1.2 Species Density
2 Seedlings Density
260 100 200 300 400 Heavily
Ind ivid u/ ha Trees Density
Forest Protected Forest
Degraded Forest Lightly Degraded
50 100 150 200 250 300 350 Heavily
157,5
Ind ivid u/ ha Poles Density 130 120
Forest Protected Forest
Degraded Forest Lightly Degraded
Figure 3: Species density for each size of forest class There was no significant relationship between individual number of seedlings and individual number of trees in the heavily degraded forest (r=-0.077, p=0.833), lightly degraded forest (r=0.227, p=0.336) and protected forest (r=0.207, p=0.567).
In the seedlings size class, heavily degraded forest has highest composition of Dipterocarps species (61.11 %) than another forest types. Dipterocaps species has the highest composition in the protected forest in the saplings class (17.91 %). The percentage of poles Dipterocarps was the highest in the heavily degraded forest (41.18 %). In contrast, it has the lowest percentage in the trees size class (26.92 %) while the highest one was in the lightly degraded forest (36.46 %).
Ind ivid u/ m
Degraded Forest Protected Forest
Heavily Degraded Forest Lightly
0,136 0,142 0,152 0,5 1 1,5 2 2,5
Ind ivid u/ m
Degraded Forest Protected Forest
Heavily Degraded Forest Lightly
1 1,5 2 2,5
2,25 1,18 1,88 0,5
2 Saplings Density 170 300
3.1.3 Species Composition The compositions of the Dipterocarps and non Dipterocarps species are shown in Fig. 3.
Saplings Species Composition Seedlings Species Composition 100%
100% age
38,89
56 80% age
77,53 82,09 87,02
90,28 50% 60% 61,11
44 ercent
40% 22,47 P ercent
20% 0% 17,91 12,98
9,72 P
0% Heavily Lightly Protected Heavily Lightly Protected Degraded Degraded Forest
Degraded Degraded Forest Forest Forest Forest Forest Dipterocarpaceae Non Dipterocarpaceae
Poles Species Composition Trees Species Composition Dipterocarpaceae Non Dipterocarpaceae 100%
100% 80% 80% 58,82 61,54
63,54 age
68,25 73,08 78,33 60%
60% ntage
40% 40% 41,18
38,46 36,46 ercent erce 31,75
26,92 20% 20% 21,67
P P
0% 0% Heavily Lightly Protected Heavily Lightly Protected
Degraded Degraded Forest Degraded Degraded Forest Forest Forest Forest Forest
Dipterocarpaceae Non Dipterocarpaceae Dipterocarpaceae Non Dipterocarpaceae
Figure 4: Species composition for each size of forest class
3.1.4 Species Similarity
In the seedlings size class, heavily degraded forest and protected forest have the highest number of shared species (11 species). Morisita-Horn values showed that lightly degraded forest and heavily degraded forest have the highest similarity based on seedlings abundance (0.07) (Table 1). This means the number of individual of shared species in both location is more similar than the other sites. In protected forest and heavily degraded forest, although the number of shared species is high, the similarity index is low because the number of individuals for each species is different between the two sites.
Table 1. Species similarity of seedlings
No. of species No. of species Shared Species Morisita- First Site Second Site first site second site Observed Horn Index Lightly degraded
Protected forest
35
30 8 0.063 forest Lightly degraded Heavily degraded
35
28
9
0.07 forest forest Heavily degraded Protected forest
30
28 11 0.026 forest
The highest number of shared species for saplings was found in between the lightly degraded forest and protected forest (21 species). Morisita-Horn values also showed that both sites have the highest similarity based on sapling abundance (0.197). Table 2. Species similarity of saplings
No. of species No. of species Shared Species Morisita- First Site Second Site first site second site Observed Horn Index Lightly degraded
Protected forest
71
38 21 0.197 forest Lightly degraded Heavily degraded
71
34 19 0.074 forest forest Heavily degraded Protected forest
38
34 13 0.091 forest
The number of shared species between all forest types of poles was not as much as in seedlings, saplings and trees size classes. There was only 2 shared species observed between lightly degraded forest and protected forest and heavily degraded forest. Meanwhile, Morisita- Horn values showed that protected forest and heavily degraded forest have the highest similarity, although only 1 shared species observed.
Table 3. Species similarity of poles
No. of species No. of species Shared Species Morisita- First Site Second Site first site second site Observed Horn Index Lightly degraded
Protected forest
37
20 2 0.028 forest Lightly degraded Heavily degraded
37
13 2 0.023 forest forest Heavily degraded Protected forest
20
13
1
0.1 forest
In the trees size class, lightly degraded forest and protected forest have the highest number of shared species (21 species). Both sites also have the highest Morosita-Horn index value (0.553). Table 4. Species similarity of trees
No. of species No. of species Shared Species Morisita- First Site Second Site first site second site Observed Horn Index Lightly degraded
Protected forest
57
41 21 0.553 forest Lightly degraded Heavily degraded
57
31 14 0.293 forest forest Heavily degraded Protected forest
41
31 6 0.143 forest
3.2 Discussion
The result suggested that the lowest species richness in all class sizes were in the heavily degraded forest. Timber harvesting intensity is one factor impacting species richness in logged over forest. Trees with dbh> 40 cm were logged in the heavily degraded forest. Although the cutting was only for the commercial ones, it affected species richness in the entire area. However, the differences were not significant in all size classes. Some studies in tropical rainforest also mentioned that tree species richness of all size classes was not significantly different among forest harvesting treatments (Parotta, 2002). The result also showed that species richness in the lightly degraded forest could be similar or higher than protected forest. The forest was able to recover its species richness naturally without enrichment planting. Previous study in West Kalimantan (Cannon et al., 1998), showed tree species richness for all trees >20 cm in diameter was significantly higher in 8-year logged forest than in unlogged forest. High species richness may be associated with increased habitat heteroginity after logging due to patchy canopy disturbance
(Cannon et al., 1998). Species richness is also affected by several ecological factors, including climatic and edaphic. The relationship between those factors and species richness is beyond this study, and therefore their relationships need to be identified and isolated.
Surprisingly, seedlings density in the heavily degraded forest is higher than the other forest types. Nevertheless, the seedlings were not equitably distributed, but merely clustered in certain area. As the area has recently been logged in 2009, the present of seedlings were predicted to come from germination of those fruits and seeds of the fallen trees. In the trees class size, species density in the heavily degraded forest is higher than lightly degraded forest altough it has just been cut. It is perhaps due to lack of commercial species in the area, as a conseqences a lot of trees are still remaining in the heavily degraded forest. The remaining trees in the site dominated by pioneer and un-commercial species, such as Macaranga spp. and Artocarpus spp. Ecological aspect that has direct impact from the number of trees density is light availability which influence the growths of seedlings. In the lowland tropical forest, seedling densities are typically low, so competition between seedlings is much less important as a cause of mortality than competition between seedlings and canopy trees (Paine et al., 2008). However, result in this study suggested that there is no relationship between the number of seedlings and the number of trees. The growth of seedlings depends on species characteristics. Rapid growth characterizes light demanding species, while high survival is found in shade tolerant species (Corlett, 2009). Sapling growth rates also vary within a species, largely due to crown size and variation in exposure to light degree (King et al, 2005). It affects poles density in the lightly degraded forest to become the highest although saplings density is lower than protected forest.
Species classification consisting of Dipterocarps species and non Dipterocarps species is based on the fact that Dipteropcarps is a pre dominant family in Bornean lowland forest. Beside its ecological role, Dipterocarps species are also major commercial timber in Indonesia, so the species is the main target of timber extraction. In the seedlings size class, dipterocarps species in the heavily degraded forest have the highest composition than the other forest types. However, it is dominated only by one species. From 55 individuals of Dipterocarps species found, 38 individuals is Shorea potoensis. The rest are Shorea leavis, Shorea faguetiana, Dryobalanops lanceolata,
Hopea dryobalanoides, and Hopea mengarawan. These may show the area has a high potential number
of commercial trees in the future. On contrary, the composition of Dipterocarps species in the heavily degraded forest is the lowest in comparison with the other sites in trees size class. It is affected by recent logging activities that harvested the commercial ones.
In the saplings size, composition of Dipterocarps species is under 20%, and the rest of size classes were up to 20%. It is unclear whether it was caused by logging activities or other factors. Dipterocarp species composition of trees in the lightly degraded forest is quite high (36,46%). It indicates that Dipterocarps species may grow well in the logged over forest. Analysing clear changes in floristic composition in tropical rain forest is difficult because majority of the species in any area represented by only a few trees. Study conducted in Peninsular Malaysia found that there were no distinct changes in species composition and the number of Dipterocarps species before and after logging (Ho et al., 2004). In Vietnam species composition of secondary forest post logged 12 years contain 15% of Dipterocarps (Tran et al., 2005). A long term research with more sample sizes in every size class of vegetation is needed to find out changes in species composition.
Patterns of similarity in species composition are influenced by the combined effects of environmental variation, the position of the area along environmental gradients, the dispersal properties of the component species, and the scale (both spatial extent and grain size) at which the patterns are examined (Steinitz et al., 2006). Although the number of shared species varies in each size classes, it is unclear why the poles size class only has two and one shared species between the sites. The lightly degraded forest and protected forest have more shared species and highest similarity. Both of these sites probably have the same environmental condition that support the similar species to grow.