silvicultural practice and growth of the jabon tree(anthocephalus

Print ISSN 1598-5504Online ISSN 2383-8272

농업생명과학연구 49(4) pp.81-93 http://dx.doi.org/10.14397/jals.2015.49.4.81Journal of Agriculture & Life Science 49(4) pp.81-93

Silvicultural practice and growth of the jabon tree(Anthocephalus cadamba Miq.) in community

forests of West Java, Indonesia Jin-Won Seo1,2·Hyungho Kim4·Jung-Hwa Chun5·Irdika Mansur1·Chang-Bae Lee3*

1Department of Silviculture, Bogor Agricultural University, Darmaga Bogor 16680, Indonesia2Subsidiary Management Team, Samtan Co., Ltd. Seoul 06182, South Korea

3Korea Green Promotion Agency, 121 Dunsanbukro, Seogu, Daejeon 35236, South Korea4Department of Forest Environmental Resources(Institute of Agriculture and Life Science), Gyeongsang National University,

Jinju, Gyeongnam, 52828, South Korea5Division of Forest Ecology, Korea Forest Research Institute, 57, Hoegiro, Dongdaemungu, Seoul 02455, South Korea

Received: MAR. 13. 2015, Revised: AUG. 11. 2015, Accepted: AUG. 11. 2015

ABSTRACTJabon tree(Anthocephalus cadamba Miq.) is a native and fast growing species in Indonesia

that is preferred by the local community because of its good adaptability and economic profitability. However, information on this tree and its appropriate silvicultural practices are still lacking. Therefore, the aims of this study were to (1) document the existing silvicultural practices used by local communities, (2) investigate tree growth performance among different sites, and (3) examine the linkage between silvicultural practices and soil fertility and their effects on stand quality in West Java. The results obtained from interviews indicated that most of the jabon plantations are owned by outsiders from Jakarta or other cities. In addition, there are three types of management: partnership, hiring employees and direct management. There are only a few practitioners with silvicultural training; however, all practitioners have implemented basic silvicultural practices. Jabon plantations in West Java were inventoried and 53 plots were established across 19 sites. This species was introduced into Java in 2008; therefore, tree age ranges from 0.5 to 3.5years. The mean diameter ranges from 2.45 to 14.57cm with a maximum of 29.3cm, and the mean height ranges from 1.29 to 12.62m with a maximum of 18.68m in Situgede. Regression modeling was performed using dominant height, and the Chapman model was selected to generate a site index curve: Hd=10.6982(1-exp(-0.8915t))1.3078, with an R2 value of 0.6513. This model divided the 19sites into three categories, i.e., good, medium and poor. Based on these results, there are 2 good, 11 medium and 6 poor sites. Three DBH-age equations were generated based on site classification. A comparison between good and poor sites suggests that site conditions and soil fertility have more significant effects on the growth of jabon than silvicultural practices such as fertilization and site maintenance.

Key words - Anthocephalus cadamba, Community forest, Silvicultural practices, Site index

*Corresponding author: Chang-Bae LeeTel: +82-42-603-7324Fax: +82-42-603-7310E-mail: [email protected]

82 … Journal of Agriculture & Life Science 49(4)

I. Introduction

As a country that is rich in tropical forests, Indonesia produced approximately 42million m3 of timber in 2010, which comprised 5.25million m3 from natural forests, 14.49million m3 from land clearing and 18.56million m3 from plantation forests. Although Indonesia is the largest tropical timber producer among International Tropical Timber Organization (ITTO) countries, this country imports wood products, including logs, from other countries such as China, Japan, and Malaysia(ITTO, 2011). Ironically, however, Indonesia will likely face a wood shortage due to increasing GDP and domestic demands. Moreover, many areas of natural forests have been dramatically deforested and plantation forests also face serious social conflicts with local communities (Nawir & Santoso, 2005). In addition, the Indonesian forest market is affected by China, which has emerged as the largest forest market in terms of production, consumption and importation of wood products(Nilsson & Bull, 2005).

Indonesia has some experiences in involving local people in plantation activities, such as re-greening with community forests(MoF, 2012) and community- based forest management(Van Noordwijk et al., 2011). These activities were designed to vitalize the local economy and compensate the shortage of wood supply from local community forests. Under low wood supply conditions, community forests can be an effective alternative and hence the Indonesian government has allocated 5.6 million ha of state production forests for community forest programs (Emila, 2007).

Recently, jabon(Anthocephalus cadamba Miq.), which is native to Indonesia, has been widely planted as a main tree species in community forests and other locations such as mining rehabilitation areas,

re-vegetation areas and industrial plantations because of its good adaptability and economic profitability (Soerianegara & Lemmens, 1993; Mansur & Tuheteru, 2010). Although some general information exists on this species in various sources such as books and journals(Mansur & Tuheteru, 2010; Mulyana et al., 2011; Krisnawati et al., 2011; Wahyutomo, 2011), it is difficult for local communities to apply these methods to their own forest because these are too general and lack specific examples. Moreover, this information does not consider specific local conditions and cannot describe the tree performance.

In Indonesia, considerable research has been conducted on jabon trees in local community forests(Kallio et al., 2011; Krisnawati et al., 2011). Kallio et al.(2011) reported that the socioeconomic factors of local communities strongly correlate with jabon stand quality. However, these factors are not sufficient to explain the effect of silvicultural practices and stand quality because of the absence of soil quality and detailed explanations on the practices implemented in the community. The results presented by Krisnawati et al.(2011) are appropriate guidelines for jabon farmers because they include sufficient information ranging from ecology to silviculture. However, their research was conducted in Kalimantan and is not applicable to the Java area. Local communities who intend to plant jabon in Java require references as well as information on the effects of silvicultural practices and socioeconomic factors. In addition, further study of jabon will provide local growth performance data for this species in the Java area. In this context, the aims of this study were to (1) document the existing silvicultural practices of jabon implemented by local communities, (2) investigate tree growth performance among different sites, and (3) examine the linkage

Seo et al: Silvicultural practice and growth of the jabon tree(Anthocephalus cadamba Miq.) in community forests of West Java, Indonesia … 83

Region Subdistrict Village No. of sites

No. of plots

Elevation (m)

Precipitation (mm/year)

Average Temperature(°C)

Bogor West Bogor Situgede 2 2 250 3,219-4,671 24.9-25.8

Megamendung Sukaresmi 1 3 900 3,179 17.8-23.9

Pamijahan Gunung Bunder 3 9 435 2,500-3,000 24-28

Jonggol Sukadamai 4 12 410 3,206 24.5-32.7

Gunung Batu 3 9 520 3,206 24.5-32.7

Sukabumi Kalibunder Kalibunder 2 6 305 3,517 19-29

Taman Jaya Ciemas 1 3 250 4,079 28-35

Purwakarta Cibodas Campaka 3 9 20 3,093 17-28

Table 1. Information of the study areas in West Java, Indonesia

between silvicultural practices and soil fertility and their effects on stand quality in West Java.

II. Materials and Methods

2.1 Study area and data collectionThis study was conducted at various community

forest sites in three areas, i.e., Bogor, Sukabumi and Purwakarta in West Java province, Indonesia. A total of 19 community forest sites that included 13sites in Bogor, 3 in Sukabumi and 3 in Purwakarta were selected through discussion with local forest agencies and communities(Table 1). Direct interviews with local people were conducted using questionnaires that included topics that were related to ownership, site history, and silvicultural practices including planting methods, tree spacing, thinning cycles and fertilizing. The interviews were conducted to obtain a description of each site and were recorded using a voice recorder. The questionnaires used in the interviews were based on previous community forestry research(Kallio et al., 2011; Krisnawati et al., 2011).

Tree measurements were conducted at each community forest site. Specifically, the tree height, diameter at breast height(DBH), and tree age were measured, the total and commercial jabon volume were calculated, and the self-pruning ability was noted. Especially, information on tree age was obtained from the questionnaires. These measurements were conducted in two or three replicates of each 0.02-ha or 0.04-ha sampling plot except for Situgede (0.2-ha sampling plot). Site-specific characteristics were described using planting distance, agroforestry and homogeneity records. Soil samples were collected from one sampling point per site because of the relatively uniform conditions. The soil samples were collected to a depth of 30cm using a soil borer. The soil samples were stored in plastic bags and analyzed at SEAMEO BIOTROP(Bogor Agricultural University, Indonesia) using a standard procedure. In this study, only five soil parameters were analyzed, i.e., N, P, K, organic C content and soil texture. The soil conditions provided valuable information for evaluating the growth performance of jabon in addition to the silvicultural practices and environmental conditions.


2.2 Data analysisThe analysis of the silvicultural practices was

based on the results of the questionnaire. The main purpose of this analysis was to document the existing silvicultural practices and to understand the present situation in the field. In this study, these data were categorized into one socioeconomic aspect and four silvicultural practices using the quantitative and qualitative information obtained from the interviews. These data provided detailed descriptions and comparisons between the various community forest sites.

Jabon growth was estimated based on field measurements of 53 temporary sample plots across 19sites. These temporary sample plot data were used to derive a provisional site index curve for classifying the various sites because permanent sample plot data were not available. Other studies such as Nunifu & Murchison(1999) and Torres et al.(2012) have also used temporary sample plot data to derive site index curves with acceptable results. In this study, we followed the basic concept of Patricia(2006) to derive the site index curves. First, a growth model for dominant height was derived based on dominant height(the mean height of 100 dominant and co-dominant trees per hectare) data collected from each plot. We analyzed three growth models, i.e., Chapman, Sigmoid and Gompertz, to identify the most accurate model. Model selection for calculating the site index curve was based on the highest coefficient of determination(R2). Second, the site index values for each sample plot were calculated based on the selected dominant height model using a base age of 3.5years, which was the maximum stand age. Each sample plot was classified into one of three site categories, good, medium, or poor, based on the site index value. Then, DBH-age equations were developed for each site category. The good and

poor sites were compared with respect to their silvicultural practices and site quality, including soil data and land use history.

III. Results

3.1 Silvicultural practices in community forests, West Java

The silvicultural practices in West Java were examined by interviewing 8 different practitioners or owners in the study areas. The interview results, which contain basic information on management type, silvicultural practices and maintenance activities in the study areas, are shown in Table 2. Jabon plantations are considered as an investment with economic gain. Therefore, most of these plantations are owned by outsiders from Jakarta as opposed to local communities or those in close proximity to the villages. The jabon plantations can be categorized into three types based on management type: partnership, hiring employees and direct management. The partnerships are referred to as ‘kemitraan’, which is similar to cooperative management. The investors provide seedlings, fertilizer and seed-money, while the farmers or local communities provide land and manpower for jabon plantations. After tree harvesting, the profit is divided based on individual contributions. In contrast to a ‘partnership’, employee hiring involves farmers that are hired and paid to maintain jabon plantations. In direct management, which is common in Gunung Bunder, Gunung Batu and Campaka, owners directly manage their plantations by hiring daily workers and regularly visiting the plantations. The primary difference between hiring and a partnership is that in the former, the investor or owner participates strongly in plantation management. However, information on jabon


Situgede Sukaresmi Gunung Bunder Sukadamai Gunung Batu Kalibunder Ciemas CampakaManagement type Partnership Employment Ownership Employment Ownership Employment Employment Ownership

Silvicultural training None Training None None None None None None

Motivation Economic Economic Economic Economic Economic Economic/Promotion1 Economic Economic

Land clearing Whole Whole Whole Whole Whole Partial/Whole Whole WholePlanting source Seedling Seedling Seedling Seedling Seedling Seedling Seedling Seedling

Seedling size(cm) 40~50 40~60 30~80 30~50 30 30~50 15 30~40Size of planting

hole(cm) 30~40 40×40×40 30×30×40 40×40×40 40×40×40 30~80 10×15×10 20×20×20

Planting space(m) 3×3 3×3 2×2.5,3×3,3×2.5

2×2, 2.5×2, 2.5×2.5

2.5×2.5,3×3,2×2 2.5×3 2×2.5 3×2.5

Mortality(%) 10 3 20～30 10～15 20 30 30 10～50Replanting Replanting Replanting Replanting Replanting Replanting Replanting Replanting Replanting

Weeding frequency Irregular 2～3 times/year 3times/year 3times/year 4times/year Irregular 4times/year every month

Pruning first year only 25% intensity every 6months None None Y/NI2 None None

Fertilization

Frequency Once Twice Once Twice Once Three times Three times TwiceN, P, K Y/NI 100g/tree 200g/tree None Y/NI None Y/NI 100g/tree

Animal manure None 2kg/hole* 3~5kg/tree 20kg/tree Y/NI Y/NI None 2kg/treeSP363 None 300g/hole* None None None None None None

Organic None None Liquid 6liter/ha None None None None NoneUrea None None None 10g/tree Y/NI Y/NI Y/NI NoneTSP4 None None None None Y/NI None None None

Dolomite None None None Y/NI None None None NonePest control

TypeA. hilaralis5,

Attacus atlas, uret

A hilaris, 1UI6

A. hilaris, Attacus atlas,

M. procris7, 2UI

A. hilaris, Attacus atlas,

M. procris A. hilaris A. hilaris A. hilaris

A. hilaris, T. ephemeraeformis8,

bagwormsFrequency Not often Not often Rarely Not often Rarely Not often Not often Rarely

Control Insecticide Insecticide Mechanical/Insecticide Insecticide Insecticide None None None

1Donation of jabon plantation to local community by government, 2Y/NI indicates ‘implemented but no information, 3Superphosphate(36 percent P2O5), 4Triple superphosphate, 5Arthroschista hilaris, 6unidentified species, 7Moduza procris, 8Thyridopteryx ephemeraeformis, *Fertilization at Sukaresmi is performed before the seedlings are planted

Table 2. Summary of ownership, silvicultural practices and maintenance activities in the study areas of West Java, Indonesia.

silvicultural practices is still lacking, and even though most owners and investors plant jabon to generate a profit, they do not have formal silvicultural training and gained their knowledge from other planters or

their own experience. Most practitioners plant jabon trees based on their own experience gleaned from sengon(Paraserianthes falcataria) or other tree species. In addition, owners typically order farmers or


hired employees to plant jabon trees without specific guidelines or directions. Each village has one main manager who usually plants jabon trees and maintains the plantation areas. This manager is asked to work together with investors because few farmers or people have experience with jabon plantations. Therefore, most of the jabon plantations in a village are managed using the same silvicultural practices; the only difference is the frequency of operations, which depends on the owner’s investment.

Land preparation is the first step in jabon plantation management. The two commonly used methods are whole and part land preparation. In West Java, the whole land preparation method is more dominant, with costs ranging from 2~2.5million rupiah per ha. Unfortunately, most owners do not know how much they spent on land preparation. The owners cleared the sites at Situgede themselves and therefore there was no cost, and in Campaka, the land was already cleared because it was ex-rice field and therefore did not require land preparation. Practitioners plant jabon seedlings obtained from various sources; the majority of seedlings are purchased from private nurseries. Seedling price and size vary, e.g., the price ranges from 1,000 to 5,000rupiah and seedling size ranges from 15 to 80cm. The trees are planted into holes that vary in size, e.g., 40×40×40cm is the preferred size, whereas other holes are 10×15×10cm or 20×20×20cm. Tree spacing is variable, e.g., 3×3m, 2×2m, 2×2.5m and 2.5×2.5m(Table 2).

The fertilizer type, dose and mixing method vary considerably among practitioners. However, fertilizer materials such as chicken/goat manure, organic matters, urea and chemicals such as NPK and dolomite are commonly used. The fertilization frequency is also variable, e.g., some farmers fertilize every six months and others fertilize only once or twice at plantation establishment. In addition, between one and four

types of fertilizer are used(Table 2).The rate of replanting is closely related to the rate

of mortality. Jabon mortality ranged from 2 to 50%(Table 2). Gunung Bunder and Campaka suffered high seedling mortality during the dry season due to a lack of water supply. Wilted seedlings were replanted as soon as possible. However, the owner at Gunung Bunder stated that the growth of the replanted seedlings would not catch up with the original seedlings unless they were planted before age six months. Weeding practices were carried out every three or four months depending on the owner and the growth of jabon. Jabon has the ability to self-prune(Mansur & Tuheteru, 2010; Krisnawati et al., 2011; Mulyana et al., 2011; Wahyutomo, 2011) and many managers do not prune for this reason. However, 25% of the branches in Situgede, Sukaresmi and Gunung Bunder were already pruned. The manager at the Sukaresmi site stated that their jabon trees were not able to self-prune and therefore pruning was carried out. The manager at Gunung Bunder stated that pruning would be performed if he thought there was an economic benefit.

Pest and disease control is one of the most important issues in forest investment. Pests such as Arthroschista hilaris, Attacus atlas, Moduza procris, Thyridopteryx ephemeraeformis and three unidentified species have been observed in West Java(Table 2). Though the frequency of pest occurrence is low and not serious, most practitioners use commercial insecticides such as Furadan, Jidor and Emamectin, and Furadan is applied before and after tree planting as a preventative method. If the trees are attacked by pests, insecticide or mechanical methods are used for pest control. Almost half of the practitioners believe these pests do not severely affect the growth of jabon and therefore have not implemented pest management practices.


SitePlot size(ha)

Age(year)

DBH1 (cm)

Height (m)

Hd2

(m)Site

classification

Soil analysis

pH Organic C(%)

Total N(%)

Available P(ppm)

Available K(ppm) Texture

Situgede-1 0.2 3 9.11 6.74 10.51 Medium 5.2 1.02 0.16 5.04 65.50 Clay

Situgede-2 0.2 3 14.57 12.62 17.26 Good 5.2 1.06 0.14 2.70 198.90 Clay

Sukaresmi-1 0.04 2.42 11.01 7.78 10.00 Medium 5.5 3.82 N/A3 3.14 153.3 Sandy Loam

Gunung Bunder-1 0.04 0.58 3.63 2.73 3.75 Medium 4.8 1.16 0.17 4.73 55 Clay

Gunung Bunder-2 0.04 0.92 7.89 6.19 8.00 Good 4.6 1.62 0.19 10.34 147.6 Clay

Gunung Bunder-3 0.04 1.42 8.30 6.32 8.55 Medium 4.7 1.2 0.2 7.39 50.4 Clay

Sukadamai-1 0.02 1.5 3.88 2.83 4.07 Poor 4.3 1.45 N/A 5.79 135.1 Clay

Sukadamai-2 0.04 2 7.62 6.19 8.36 Medium 4.4 1.42 N/A 5.8 211.5 Clay

Sukadamai-3 0.02 1.5 5.62 4.50 6.82 Medium 4.4 1.77 N/A 16.55 125.9 Clay

Sukadamai-4 0.02 2.5 6.70 6.06 8.46 Medium 4.8 2.38 0.18 6.04 120.4 Clay

Gunung Batu-1 0.02 0.75 3.46 2.79 3.64 Poor 4.2 2.2 N/A 3.39 136.2 Clay

Gunung Batu-2 0.04 2.5 8.27 5.82 7.91 Poor N/A N/A N/A N/A N/A N/A

Gunung Batu-3 0.02 1.5 5.20 4.21 6.31 Medium N/A N/A N/A N/A N/A N/A

Kalibunder-1 0.02 1.5 6.35 5.17 7.39 Medium 4.6 1.72 0.2 21.8 263.7 Clay

Kalibunder-2 0.02 2.5 8.15 6.99 9.39 Medium 4.7 1.96 0.19 3.29 69.6 Clay

Ciemas-1 0.04 3.5 7.55 6.26 8.65 Poor 5 2.08 0.22 2.1 108.8 Clay

Campaka-1 0.02 0.58 3.93 2.01 2.72 Poor 5 0.51 0.08 0.91 N/A Clay

Campaka-2 0.02 0.58 5.14 2.88 3.49 Medium 5 0.51 0.08 0.91 N/A Clay

Campaka-3 0.02 0.58 2.45 1.29 2.17 Poor 5.1 0.52 0.08 0.33 N/A Clay1Diameter at breast height, 2Dominant height, 3Not available

Table 3. Summary of sample distribution of tree stem analysis and soil characteristics in the study areas of West Java, Indonesia.

3.2 Growth of jabon trees in community forests, West Java

Jabon trees were introduced into West Java in 2008; therefore, tree age ranges from 0.5 to 3.5years (Table 3). The mean diameter ranges from 2.45 to 14.57cm with a maximum of 29.3cm, and mean height ranges from 1.29 to 12.62m with a maximum of 18.68m in Situgede.

Soil samples were analyzed for pH, organic compounds(organic C), total nitrogen, available phosphorus, available potassium and texture at SEAMEO Biotrop, Bogor. Most soil has a clay texture except for the Sukaresmi area in West Java(sandy loam). The overall soil pH ranges from 4.2 to 6.1.

Forest site quality refers to the sum of factors that influence the production capacity of a forest.


Fig 1. Site index curves based on the Chapman model for jabon trees in the study areas of West Java, Indonesia: (a)Chapman dominant height(Hd) growth curve and (b)site index classes based on dominant height using a base age of 3.5years. Dotted lines indicate lower and upper ranges of the three index classes.

Therefore, site quality is closely correlated with timber production. In general, site quality is determined using the site index, which is based on the mean height of the dominant trees in permanent sample plots. However, there are no permanent sample plots or long-term data for jabon in West Java because this study is based on exploratory field surveys. Therefore, the site index curves from temporary sample plots were used to determine the site quality of jabon plantations in West Java. First, the dominant height(i.e., the mean height of the 100 tallest trees per hectare(Hd; dominant height) or its estimation through permanent or temporary sample plots needs to be determined for each plot. The measurement of dominant height depends on plot size. For example, if the size of a sample plot is 0.02ha, the two tallest trees are selected for the determination of dominant mean height.

Second, the most reasonable model to fit mean dominant height growth functions is needed. In this study, Chapman’s three-parameter model was selected based on the R2 value after comparison with two

other model types(i.e., Sigmoid and Gompertz). Though the R2 values did not vary greatly among three models, the R2 value of the Chapman model was slightly higher(Chapman R2=0.6513, Sigmoid R2=0.6441, Gompertz R2=0.6481, P<0.001 in all cases).

Site index was calculated using a base age of 3.5years based on the available inventory data. A site index equation was derived following equation(1) and a curve was drawn using the dominant height growth model(Fig. 1a).

Hd=10.6982(1-exp(-0.8915t))1.3078 ··················· eq.(1)

where Hd and t indicate dominant height and tree age, respectively. Equation(1) was used to calculate the regression coefficient ‘a’ for each plot using equation(2):

a=Hd/(1-exp(-0.8915t))1.3078······························eq.(2)

The site index(SI) at base age 3.5years was


Site index classes

Site indexNumber of sitesLower

range(m)Upper

range(m)

Good 13.33 17.86 2

Medium 8.79 13.32 11

Poor 4.25 8.78 6

Table 4. Site index classes and lower and upper ranges based on dominant height in the study areas of West Java, Indonesia.

Fig. 2. Curves and equations predicting DBH from age based on the site index classes of jabon trees in the study areas of West Java, Indonesia.

estimated on a per plot basis using the a’ coefficient and equation(3):

SI=a(1-exp(-0.8915(3.5)))1.3078 or SI = a(1-exp(-3.12025))1.3078····· eq.(3)

Site index ranged from 4.25m to 17.86m(Table 4). The difference between the minimum and maximum site index was used to classify each site as good, medium or poor. Then, site index curves were generated and each plot was categorized into one of the three groups based on the site index value(Fig. 1b).

Growth equations for DBH and height were constructed using the Chapman regression model in Fig. 2.

IV. Discussion

For many people, jabon planting was economically motivated. Ironically, however, nobody received any type of silvicultural training, and most of their silvicultural knowledge was obtained from their own

experience or other planters(Table 2). In Kalimantan, for example, only 21% of farmers had received silvicultural training even though 97% of them mentioned economic motivation for tree planting(Kallio et al., 2011). These farmers learned silvicultural practices from other planters(45%) or their own experience(31%). Though the research areas and management types of the current study differ from those in the study conducted by Kallio et al.(2011), there are similarities with respect to the lack of silvicultural training and economic motivation for tree planting. In both studies, most planters implemented silvicultural practices relatively well. In the study conducted by Kallio et al.(2011), the majority of farmers adopted more than three types of tree planting practices based on economic motivation and their own experience. In spite of the best maintenance practices, silvicultural training and knowledge of jabon are lacking. In this and the study conducted by Kallio et al.(2011), there were a maximum of four farmers who learned planting practices from the government. Salam et al.(2000) mentioned forest extension activities can positively affect tree planting. Jabon planters who were long-term members of a farmer’s group were more active in silvicultural management because interaction with other farmers encouraged better farming


practices(Bebbington, 1996; Kallio et al., 2011). Therefore, silvicultural practices and support of farmer’s group can be motivators for jabon planters.

The planted seedlings ranged in size from 15-80cm (Table 2). Mansur & Tuheteru(2010) recommended a seedling height of 25-30cm and a diameter of approximately 0.5cm, while Krisnawati et al.(2011) suggested a seedling height of 30-40cm and a diameter of approximately 1cm. In this study however, some planters bought seedlings that were cheap(Campaka) or too small(Ciemas). These types of seedlings can result in high mortality rates(Table 2). In the study conducted by Krisnawati et al.(2011), fertilizers were required to attain optimal growth on infertile land and therefore in South Kalimantan, urea and triple super phosphate(TSP) were widely applied on more than one occasion during the first two years of growth. In West Java, NPK, animal manure and urea were widely applied, but only TSP was added in Gunung Batu(Table 2). The application of 15g of urea per seedling resulted in a rapid increase in jabon growth(Soerianegara & Lemmens, 1993), and some fertilizer research on this species has been conducted at Bogor Agricultural University(Mansur & Surahman, 2011; Wulandari et al., 2011; Supriyanto & Fiona, 2012).

The mean diameter of jabon trees less than 5 years old in South Kalimantan ranged from 6 to 16.4 cm with a maximum diameter of 25.3cm(Krsinawati et al., 2011). The mean height ranged from 4.1m to 14.6m with a maximum value of 17.1m. The mean diameter and height in the current study are less than those reported for South Kalimantan; however, the maximum diameter and height are greater(Table 3). Krisnawati et al.(2011) documented higher growth rates of diameter and height in Java compared with South Kalimantan. Although stand ages in Java ranged from 0.5 to 3.5years, the maximum values

were higher and the mean values were not different from those measured in South Kalimantan.

The 19 sites in West Java were categorized into good, medium or poor sites based on the site index curve generated from the temporary sampling plots. Two sites were categorized as good, six as poor and the remainder as medium(Table 4).

Though the site index curves for jabon were derived from 0.5- to 3.5-year-old plantations, these are useful data to estimate future productivity by comparing with a previous study conducted by Sudarmo(1957). Compared with the results presented by Sudarmo(1957), the site index curve for jabon (Fig. 1) can be matched to a particular site index class and future long-term growth can be estimated. For example, the site index of a good site ranges from 13.33m to 17.86m, which can be matched to site class IV or V. Sudarmo(1957) reported that several jabon plantation areas in Java could reach a maximum volume mean annual increment(MAI) of 20㎥/ha/year by age 9years on a good quality site. On a medium quality site, an MAI of 16㎥/ha/year can be attained in 9years compared with an MAI of 13㎥/ha/year at age 24years on poor quality sites.

In the current study, only good and poor sites were compared to clarify the differences between silvicultural practices and site conditions(including soil). There were no apparent differences in silvicultural practices between the good and poor sites. However, these sites differed with respect to fertilizing and pruning practices(Table 2). It was observed that higher amounts or more frequent applications of fertilizer were applied to the poor sites. It is possible that poor growth of jabon prompted practitioners to apply fertilizer. In addition, pruning was performed at least once on the good sites. Generally, jabon does require pruning because of its ability to self-prune. It is difficult to clearly


determine the effect of silvicultural practices on each site because similar practices are implemented at most sites.

Soil fertility and site conditions are complicated factors to describe and compare because of high variability between sites. Consequently, a comparison between each good and bad plot with closely located medium plots could be more reasonable and a means to reveal reliable information. The only two good sites were Situgede-2 and Gunung Bunder-2. The Situgede-2 site is located close to pond, and the Situgede-1(medium) site is located on an ex-rice field. Both of these sites appear to have similar conditions; however, the water level at Situgede-1 is so high that the tree roots cannot penetrate the soil, which results in slow growth. In addition, the available soil potassium at Situgede-2 is higher than Situgede-1. The Gunung Bunder-2 site contains more fertile soil than other closely located sites such as Gunung Bunder-1 and Gunung Bunder-3(Table 3). Some of the poor sites have highly acidic(Gunung Batu, Sukadamai-1) or infertile soils(Campaka-1, 3). Campaka-2 has better growth compared with closely located sites even though the soil conditions are same. However, agroforestry with red pepper was implemented at this site.

Many people continue to plant jabon in Indonesia for economic reasons. The results of this study will help to ensure successful jabon plantations. First, training is needed, including basic knowledge of silviculture and forestry. Few people have studied forestry or related fields and therefore they need training on basic information such as measuring height and diameter or selecting good quality seedlings. Government can support extension programs for investors as well as local farmers. Second, site selection is very important. Unfortunately, many investors or farmers planted jabon on barren land

because this was the only land available. However, site conditions must be considered before trees are planted. The results presented by Zuhaidi et al. (2012) indicate that jabon may not be suitable at high elevation sites or those without an adequate water supply. Similar results were observed in the current study, where favorable growth occurred at the Situgede-2 site located close to ponds. Moreover, Mansur & Tuheteru(2010) recommended that jabon be planted at an elevation of approximately 500m above sea level. Third, the seed origin needs to be checked and good quality seedlings must be selected in the nursery. More than half of the planters bought seedling from private dealers(Table 2). In addition, they did not know the origin of the seed and ordered as many seedlings as they needed. Genetic factors are very important to maximize tree growth. Therefore, farmers need to check the origin of seeds and to buy seeds from a good mother tree. Moreover, good quality seedlings guarantee good quality trees and lower mortality. Farmers can select good seedlings based on seedling height(25-35cm) and diameter(0.5cm)(Mansur & Tuheteru 2010). Finally, an agroforestry system should be considered as understanding practices and then implementing these in the field are totally different. In large plantations, agroforestry systems can help farmers or workers to continuously maintain the trees. As seen in the case of Campaka, agroforestry can ensure that plantations are maintained by farmers and workers.

In this study, we used only 19 sites comprised of 53 plots to investigate jabon tree growth and site index. More than hundreds of samples or permanent plots were analyzed in previous studies examining site index or growth equations of different tree species in Indonesia. However, jabon research in West Java is limited, e.g., this species was first planted in 2008 and therefore the trees are


young(Mansur & Tuheteru, 2010; Krsinawati et al., 2011). Despite these limitations, the growth equations and site index curves of jabon trees in West Java are useful for field practitioners to understand site conditions and tree growth.

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silvicultural practice and growth of the jabon tree(anthocephalus

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