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Estimation of net primary productivity of young teak plantations under the intensive Tumpangsari system in Madiun, East Java

TROPICS Vol. 3 () Issued October 30, 003 Estimation of net primary productivity of young teak plantations under the intensive Tumpangsari system in Madiun, East Java Ris Hadi PURWANTO ), Hasanu SIMON ),
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TROPICS Vol. 3 () Issued October 30, 003 Estimation of net primary productivity of young teak plantations under the intensive Tumpangsari system in Madiun, East Java Ris Hadi PURWANTO ), Hasanu SIMON ), and Seiichi OHATA ) ) Graduate School of Agriculture, Kyoto University, Kyoto , Japan ) Faculty of Forestry, Gadjah Mada University, Yogyakarta 558, Indonesia ABSTRACT Teak plantations ( to 7-year-old) under an agroforestry system (tumpangsari) in a humid tropical region in the Madiun Forest District, East Java, were analyzed for aboveground biomass and net primary productivity through the stratified clip techniques. Tumpangsari is an agroforestry system adopted in Indonesia to establish teak plantations. Tumpangsari means co-occupation for a limited period, and the co-occupants are agricultural crops in the forest area. The research was carried out from October, 996 to September, 000, and allometric relationships were determined relating diameter at breast height and total height to weights of stem, branches and leaves. Root weight was estimated from the weight of non-photosynthetic components (stem and branch). The total biomass ranged from.76 for - year stands to t ha for 7-year stands. The annual amount of leaf litter fall in the 7-year-old stands was 5.58 t ha. The annual consumption of leaves by herbivores varied considerably by stand age, ranging between t ha ; equivalent to % of leaf biomass. The net primary productivity (NPP) increased with age, and was greater in trees living in open spaces previously covered by cash crops under tumpangsari. The mean productivity was t ha yr in 7-year-old stands. The estimated NPP was higher than those of teak plantations in a dry tropical region in Chakia, India, whose largest productivity was 5.60 t ha yr. The large productivity of teak trees at the young stage in the Madiun Forest District is considered to be partly because of the high humidity and temperatures in East Java. However, the high productivity also seems to be influenced by the teak plantation management of tumpangsari, which includes applying intensive cultural practices such as soil work (tillage in land preparation and weeding), fertilization with both chemicals and manure, and thinning. Key words: allometry, East Java, large productivity, tumpangsari, young teak forests INTRODUCTION As the main timber species, teak (Tectona grandis Linn.), has been planted in Indonesia for the past two hundred years in the lowlands of monsoon climate regions (Cordes, 88; Whitmore, 98). The management of teak plantations in Java is based on the Management Strategy of Teak Forest Plantations proposed by the Dutch in 938, which does not consider the prevailing socio-economic conditions of the society living around the forests (Simon, 993). Now the management of teak plantations in Java is under the authority of Perhutani, the State Forest Enterprise in Indonesia. The commonly used method for reforestation of both clear-felled and degraded areas is the taungya (locally called the tumpangsari) system. Tumpangsari is an agroforestry system adopted in Indonesia to establish teak plantations. Tumpangsari means co-occupation for a limited period, and the co-occupants are agricultural crops in the forest area (Kartasubrata, 979). In this system, landless farmers receive 0.5 hectares of forest land on which they have to plant trees and cash crops until the third year, and the labour wage is paid in-kind with the yields of the cash crops. The results of the tumpangsari system are not always optimal for both the harvest of crops and teak trees when pressure on land is high. To increase forest land productivity, Perhutani initiated a social forestry programme in 99 in cooperation with the Faculty of Forestry Gadjah Mada University. This programme aimed to improve forest management to increase forest productivity and local people s income under the intensive tumpangsari system. To encourage farmer involvement, the farmers get the opportunity to plant cash crops on the forestland, subsidies to buy agricultural devices, fees for land preparation, and fertilizers (both chemical and manure) in the newly established tumpangsari sites. The management of tumpangsari in Indonesia has a long tradition. Consequently, there is an extensive body of empirical knowledge on the use and management of the trees and associated crops. The economic productivity of the crops is relatively well documented, but more tree studies should be undertaken (Kartasubrata, 979). Though teak forests have been raised on a large scale by the State Forest Enterprise, a database on biomass and teak productivity in Java is lacking. This report presents the results of a study on the productivity of young teak forests under the intensive tumpangsari 0 R. H. PURWANTO, H. SIMON, & S. OHATA system. MATERIALS AND METHODS Description of study area The study area is located at the eastern foot of Mt. Lawu (7 30 S and 30 E) in East Java, Indonesia and is managed by Madiun Forest District, a State Forest Enterprise under the control of Perhutani in Java. The Madiun district is a regency city in East Java Province covering an area of ca.,5 (5,00 ha). The Madiun Forest District covers an area of 30,395 ha, or 6% of the total area. According to the provincial administration, the forest area includes three towns, namely Madiun town covering 5, ha (50.7%), Ponorogo town with 3,36 ha (.%) and Magetan town,,537 ha (5.%)(Fig. ). Various aged forests grow on volcanic soil from 50m to 600m in altitude. The forests are predominantly teak plantations with 6,69 ha (88%) and many other species such as cajeput (Melaleuca leucadendron), Casia siamea, Acacia spp, Swietenia spp, Schleichera oleosa, Gmelina arborea, Paraserianthes falcataria, Leucaena glauca, Melia azedarach, Dalbergia spp, Eucaliptus spp, etc. are commonly found either as mono or mixed plantations. The climate is monsoonal with two distinct seasons: a dry season (May-September) and rainy season (October-April). Air temperature is relatively stable throughout the year with mean daily temperatures of 8.8. Mean annual precipitation during the past 0 years was 900 mm, ranging from 693 to 9 mm. On Whitmore s map of rainfall types for the tropical Far East, the area is classified into types C and D or as a seasonal type (Whitmore, 98). The ground vegetation cover in teak plantations during the rainy season consisted of ca. 3 species. Eupatorium pallescens is the dominant shrub species as undergrowth (Pudyatmoko, 998). The accumulated litter fall in the forest floor together with shrubs and grasses is a potential fire risk during the dry season. The geological structure in most of the area is volcanic, the soil type is a redbrownish latosol, and the topography is gently undulating and slightly rocky (Margono et al., 989). Magetan West Java INDIAN OCEAN 0 3km N Madiun Ponorogo JAVA SEA Central Java Mt. Lawu Caruban INDONESIA East Java Study area : Town : Forest area : River : Road : Forest District Boundaries Fig.. Map showing the study site. Plant materials The research included teak plantations planted in 99, 995, and 996, extending over an area of ca ha. During the establishment years (99-996), tillage, weeding and fertilization were performed. 7 kg N/ha and 3 kg N/ha of urea were applied at a half and one and a half years after sowing, respectively. Manure fertilizer (cow dung, poultry manure and/or decomposed rice straw) was applied in an amount of 50 kg/ha for teak and agricultural crops every year throughout the entire growing season for four years. Teak seeds are directly sown on the site using a spacing of 3 m, equivalent to 3300 trees ha -. Wide inter-spaces, having no shade, were utilized for planting the main cash crops such as peanuts, chilies, cassava, maize and rice. Cash crops are commonly not cultivated until the fifth year, at the moment of teak canopy closure. Leguminous species (Leucaena glauca), which supply fodder and green manure, are grown by line planting between teak rows in the initial stage. Because of its nitrogen fixing ability, stems of Leucane glauca trees are usually cut 0 cm above ground level when half-year-old after sowing to cover the land surface and improve conditions for decomposition. Thinning Thinning was done to immature stands in order to stimulate the growth of teak trees and increase the total yield. The thinning method used for the teak plantations is low thinning. The first thinning in stands planted in 99 was carried out four and half years after sowing, and the thinning was more or less 50% of original stock, depending upon the growth, density and site quality of the plantations. Pure teak stands are usually formed in the sixth year. Estimation of Net Primary Productivity of Young Teak Plantations under the Intensive Tumpangsari System in Madiun, East Java Plot establishment To estimate teak biomass and net primary productivity, thirteen sample plots of 7 m (0.03 ha) in size were randomly placed in five different to 7-year-old teak forest plantations during the period of 996 to 999 (Table ). 99 teak trees per plot were sampled when there was no mortality in the plots. Trees were tagged and their diameter at breast height (D,.3 m above ground level) and total height were measured once a year at the beginning of the growing season from 996 until 999. Dominant height (the average of the 00 tallest trees per ha or equivalent, which are uniformly distributed) within each plot was determined to estimate the site quality in Java, as suggested by Wuelfing (93). Descriptions of the sampled teak plantations are listed in Table. To estimate leaf production per year, fifteen litter traps, each in size, were randomly placed under trees in the 6- year-old plantations and the litter was collected every weeks from October 997 to September 998. The litter was dried at 80 and weighed. Table. Description of the sampled teak plantations Dominant height Plantation Date Plot Density at measuring time (m)* no. planted no. (trees ha - ) Oct 96 Oct 97 Oct 98 5a 66b 79 5b 53b Total Oct 96 Oct 96 Oct 95 Oct 9 Oct * Dominant height is the mean height of the 00 tallest trees per ha or equivalent (Wuelfing, 93). In this study, the three highest trees per plot were used to define the dominant height. Oct Estimation of biomass and productivity We estimated the aboveground biomass of teak forests using allometric relationships (Ogawa & Kira, 977). To produce the allometric equations, the stem diameter at.3 m above the ground (D) and height (H) of trees were measured to determine allometric relationships between D and stem diameter at the lowest major living branch (D B ). 3 trees stem weight (W S ), 7 trees branch weight (W B ) and 9 trees leaf weight (W L ) was also measured. Leaf area (U) was measured by utilizing the allometric of W L (9 trees) and adding a tree around the plot, so that 0 trees determined the U-W L relationships. Leaf area index (LAI, one-side leaf area per unit ground area) was obtained by multiplying the mean leaf area of those individual trees by the number of trees per unit area on the ground. Sampling was done in the growing season (April 000) and at the end of the dry season (September 000). Dry weight was calculated after drying the samples at 80. Teak has a shallow root system. Young teak trees develop fine rootlets in the upper-moist soil layers during the rainy season to absorb nutrient from the surface layer. However, in the dry season, these fine rootlets die off and roots develop in the deeper layers of soil strata where adequate aeration is available (Bebarta, 999). Many authors have studied the root biomass of various species. Negi et al. (995) reported that the percentage of root biomass in different teak plantations varies from 8 to 6 percent of the aboveground biomass of non-photosynthetic organs (stem and branch), equivalent to 7 to percent of the total above ground biomass. In this study, a moderate value of 0 percent, (Whittaker & Marks, 975), is used to estimate root biomass from the total stem and branch biomass. Various allometric relationships between individual tree characteristics as mentioned above, were determined and shown in Table. R. H. PURWANTO, H. SIMON, & S. OHATA Table. Values of constants (a,b) in allometric relations (y=ax b ) between tree dimensions Dimensions* b a No. of units samples of (trees) measurements r D B D cm,cm 0.97 W S D H kg,,m 0.99 W B D H kg,,m 0.98 W L D B kg, 0.98 U W L ,kg 0.99 * Symbols D B, W S, W B, W L, U, D and H show the stem diameter at the lowest major living branch, weight of stem, branches and leaves, total leaf area, stem diameter at breast height and height of trees, respectively. Field observations suggested that the consumption of leaves by herbivorous animals and insects (G) was significant, so the G-term was included in our measurement of net primary productivity. Teak has large leaves 0-50 cm long and 5-0 cm wide, and they are broadly elliptic, obovate, and rough on the surface (Tewari, 999). The consumption of leaves by herbivorous animals and insects (G) in Madiun Forest District seemed relatively uniform in all of the crown forests. To estimate the leaf loss by grazing, 3 trees around the plots were felled in the growing season (April 000). Their crowns were divided into three layers (lower, middle and upper), and 5 - leaves were randomly sampled from each layer of a sample tree, so that in total 8 leaves were sampled. The amount of leaf loss by grazing of herbivores (G) was measured from holes and the discolored areas of the sample leaves (Larsen & Kershaw, 99). Net primary productivity for 7-year-old teak plantations was calculated by the following equation (Kira & Shidei, 967; Möller et al., 95). NPP = B + L + G () where B is the annual forest biomass change between time and time. L and G are the annual amounts of litter fall and leaf loss by grazing during the period. It was difficult, however, to measure leaf litter in 5 year-old or younger stands where cash crops were planted. The leaf litter fall in the and 5-year-old plantations was estimated from leaf biomass (Y L ) among the plots and turnover rate of leaves (L/Y L ) in the 7-year-old stands. RESULTS AND DISCUSSION Biomass and leaf area index The regression coefficients of allometric relationships to estimate stem, branch, leaf weights and leaf area are shown in Table. The relationships between tree characteristics were linear in log log scale diagrams with r over 0.97, suggesting the growth pattern of tree characteristics were closely inter-dependent. Table 3. Teak biomass of various stand ages (mean valuesse) Stand Number Y age of S Y B Y R * Y Total L biomass LAI (years) plots (t ha - ) (t ha - ) (t ha - ) (t ha - ) (t ha (ha ha - ) ) Y S, Y B, Y R, Y L : stem, branch, root and leaf biomass, respectively. LAI: Leaf Area Index (one-side leaf area per unit ground area). * Estimated from weight of non-photosynthetic components, assuming 0 percent of the total stem and branch biomass. Biomass and LAI of young teak plantations are shown in Table 3. The total biomass and leaf area index of teak trees Estimation of Net Primary Productivity of Young Teak Plantations under the Intensive Tumpangsari System in Madiun, East Java 3 increased with age and in trees in open spaces previously planted with cash crops. Mean total biomass of teak was estimated to be t ha - at 7 years old. Leaf biomass also increased with age and had a mean value of 3.5 t ha - at 7 years old. The mean value of leaf area index (LAI) was calculated as.86 ha ha - in the 7-year-old forests. This value is comparable to many communities of deciduous woody plants having LAIs of 3 to 6 (Kramer & Kozlowski, 979). Amount of litter fall The average litter fall in the 7-year-old forest was t ha - (Table ), comprising of 00 percent leaf litter. This leaf litter value was almost the same as that of the average measured in over twenty tropical forests, at 5.50 t ha - (UNESCO, 978), and falls 0.9 within the range of average leaf litter of teak forests in India from 3. to 6.9 t ha - (George & Buvaneswaran, 00). It is generally found that litter 0.6 production is a function of age and tree density. Compared with the leaf biomass, the leaf litter production of the 7-year-old forest was nearly two times as large as leaf biomass, so that the average 0.3 annual turnover of leaves was estimated as.6 yr -. The apparent mean longevity of the leaves was estimated as 0.6 years. Although the teak tree is 0 usually considered a deciduous species in tropical 97 Oct. Nov. Dec. 98 Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. monsoon climates, it is often evergreen in moist Rainy season Dry season regions (Riffle, 997). Young teak trees in the Madiun Forest District usually grow in all seasons, except the extreme dry season. In this study site, young teak trees often have only a few leaves at the Month Fig.. Pattern of leaf litter fall in 7-year-old teak plantations in the Madiun Forest District, East Java from October, 997 to September, 998. stem top in the dry season. The mean seasonal pattern of leaf litter fall in 7-year-old forests is shown in Fig.. The leaf litter fall was continuous throughout the year, and the peak leaf-fall period was during the months of May and June, which is the end of the growing season in this plantation area. Table. Teak productivity of various stand ages (mean valuesse) Stand age (years) Number of plots 9 At time (t ha - ) Leaf litter fall (t ha- yr-) Total biomass (stem,branch,root,leaf) At time (t ha - ) B (t ha - yr - ) L (t ha - ).70.9* * G (t ha - ) NPP (t ha - yr - ) B : biomass (stem, branch, root and leaf ) increment of the forest. L : leaf litter during the period. G : leaf loss by grazing during the period. NPP : Net Primary Productivity =B+L+G. * Leaf litter fall in the and 5-year-old stands was estimated from leaf biomass among the plots and turnover rate of leaves in the 7- year-old stands. Amount of grazing The consumption of leaves by herbivores (G) varied between t ha - with stand age; equivalent to % of leaf biomass (Table ). In most teak forests in Java, teak bee-hole borer and insects pests such as leaf-eating caterpillars, leafrolling and leaf-mining caterpillars, leaf-eating beetles and grasshoppers can be found. They vary in abundance by season, R. H. PURWANTO, H. SIMON, & S. OHATA from locality to locality and also year to year, possibly due to varied climatic and topographical conditions (Tewari, 999). In East Java, these defoliating insects, leaf-eating caterpillars and grasshoppers are commonly found in the early rainy season, November December. Jha (999) and Tewari (999) reported many species of leaf eating caterpillars in teak forests in India, and the most important are the teak skeletonizar Eutectona machaeralis (Lepidoptera : Pyralidae) and Hyblaea puera (Lepidoptera : Hyblaeidae). In both cases, total or partial leaf damage is reported to be 8.% of leaf biomass. Kira (970) reported that the consumption of leaves by caterpillars in Pasoh forests was %, which is obviously a minimum estimate of biomass consumption by heterotrophs. Net primary productivity The amount of organic matter produced in one year (net primary productivity or NPP), for each stand was estimated using Equation, shown in Table. The values of NPP varied from.88 t ha - yr - to t ha - yr -. The net productivity in the 5- year-old forests was about a third of the productivity in the 7-year-old forests. The low productivity in the 5-year-old plantations was probably due to the thinning at four and half years after sowing. The NPP in the 7-year-old forests was t ha - yr -. This was larger than that of a -year-old plantation of teak forests in a dry tropical region in Chakia, India, whose largest productivity was 5.60 t ha - yr -, where mean annual precipitation is 76 mm and temperature is 30 (Karmacharya & Singh, 99). A tropical rain forest in Khao Chong, Thailand had an NPP of 8.60 t ha - yr - and mean annu
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