Simulating Harvest Schedule for Timber Management and Multipurpose Management in Teak Plantations

Tiryana, T. 2016. Simulating harvest schedule for timber management and multipurpose management in teak plantations. Jurnal Manajemen Hutan Tropika 22(1): 1–12. Available at: http://journal.ipb.ac.id/index.php/jmht/article/view/11879/9595

Abstract

Sustainable management of teak plantations in Java requires an improvement of the existing yield regulation method to optimize multiple benefits of the plantations at risk of stand destruction. This study was therefore aimed to formulate an alternative harvest scheduling model that integrates risk of stand destruction for supporting multipurpose management of teak plantations. The proposed model used a state-space planning model to simulate the dynamic of plantations due to timber harvesting and stand destruction, and then sought optimal solutions for two management scenarios, i.e. timber management that optimized total harvest volume and multipurpose management that optimized net present value (NPV) while increasing carbon stocks. Using a case study on a typical teak plantation, this study confirmed that increasing destruction rates reduced harvest volumes, NPV, carbon stocks, and resulted in imbalanced ending age-class structures. Reducing cutting-age limit increased harvest volumes and NPV, but it also reduced carbon stocks of the plantations. Although the multipurpose management generated lower financial benefit, it maintained carbon stocks and produced better ending age-class structures compared to timber management. The proposed harvest scheduling model provides a useful planning tool for managing teak plantations.

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Review of Existing Sustainable Forest Management (SFM)-Based Projects in Indonesia

Rusolono, T. and Tiryana, T. 2011. Review of Existing Sustainable Forest Management (SFM)-Based Projects in Indonesia. Ministry of Forestry and International Tropical Timber Organization (ITTO), Jakarta. (in English and Indonesian)

Summary

Since the 13th climate change conference (COP 13) in 2007, sustainable forest management (SFM) has been considered as an option for reducing emissions through REDD+ mechanism. Such international agreement provides a great opportunity for Indonesia to highly involve in the REDD+ mechanism, because Indonesia has abundant forest resources. The REDD+ mechanism through SFM, however, needs to be further investigated because until now there is no real implementation yet. This study was aimed to review the progress of SFM practices and REDD+’s demonstration activity projects in Indonesia, to analyze several SFM scenarios for reducing emissions, and to formulate relevant strategies for reducing emission through SFM.

Forest management in Indonesia has initially focused on the utilization of natural production forests to achieve sustained timber yield. Such forest management practice, which was started on around 1970 through forest concessionary licenses, tended to exploit the natural forest resources that resulted in high deforestation and forest degradation. In the period 1990–2009, the number of forest concessions decreased up to 45%, indicating an unsustain management of the natural production forests. Among 308 concessions, which were still exist until June 2011, only five concessions granted SFM certificates by FSC (Forest Stewardship Council) or LEI (Lembaga Ekolabel Indonesia, the Indonesian Ecolabeling Institute).

Considering the decline of natural forest resources, since 1989 Indonesian government has been developing industrial plantation forests (especially in outside of Java) to fulfill increased demands for timber and to improve productivity of critical lands. Until 2008, total area of plantation forests reached 4.3 million hectares. However, until June 2011 there were only three plantation forest management units certified by LEI.

Community forest management shows a promising progress, which is indicated by the increase of community forest areas in Indonesia, although most of the community forests (approximately 50%) concentrate in Java. Until June 2011, five community forest management units have been certified by FSC and twelve other FMUs were certified by LEI. Until now, forest management practices at natural production forests, plantation forests, and community forests do not integrate yet the potential benefits of carbon sequestration into their management objectives.

The implementation of REDD+ mechanism in Indonesia is still limited to demonstration activities at national, provincial, district, or project level. Currently, there are at least 30 demonstration activity projects in Indonesia that are financially supported by various parties, e.g. Korea, Australia, Germany, United Kingdoms, The United Nations, ITTO (International Tropical Timber Organization), TNC (The Nature Conservancy), and WWF (World Wildlife Fund). The REDD+’s demonstration activity projects were implemented for a duration of 2–5 years.

Commonly, the REDD+’s demonstration activity projects conduct five main activities: 1) determining an appropriate baseline, 2) calculating the emission reduction of a project against the business as usual (BAU) scenario, 3) formulating procedures for monitoring, reporting, and verification (MRV) of emission reduction activities, 4) accounting tradable carbon units, and 5) developing distribution system for the payment of carbon trading to involved parties. Those projects are expected to provide lessons learned on methods and technical implementation of REDD+ mechanism in Indonesia. Until now, however, there is no REDD+’s demonstration activity project implemented in a forest management unit level, which could provide lessons learned for forest managers on how to reduce emission through SFM practices.

 To explore the potency of SFM as an option for reducing emission in the REDD+ mechanism, this study developed and analyzed several scenarios for managing natural production forests, plantation forests, and community forests. For natural production forests, a case study in Sari Bumi Kusuma (SBK, Central Kalimantan) concession showed that emission reduction benefits can be gained if forest management unit (FMU) applies a multisystem silviculture (i.e. combination of TPTI and TPTJ systems) coupled with AAC (Annual Allowable Cut) reduction. For 30 years, such scenario could reduce carbon emission up to 447.75 MtCO2e for a total effective area of 119,607.45 ha or an average of 124.78 tCO2e/ha/yr. The emission reduction benefit of such scenario was similar to that of applying TPTI system to the entire effective area, which reduced carbon emission up to 443.82 MtCO2e or an average of 123.69 tCO2e/ha/yr. The FMU would gain lower emission reduction benefits if it implements either TPTJ system to the entire area (i.e. 83.75 tCO2e/ha/yr) or a multisystem silviculture without AAC reduction (i.e. 103.48 tCO2e/ha/yr).

In addition to avoiding deforestation, another effort for reducing emissions is avoiding forest degradation. The case study of teak plantations in KPH Kebonharjo (Perum Perhutani Unit I, Central Java) confirmed that the FMU would gain the highest benefit of emission reduction (i.e. 202,630 tCO2e/yr for KPH Kebonharjo or equal to 11.38 tCO2e/ha/yr) if forest managers can avoid forest degradation. Such scenario, however, seems difficult to implement because teak plantations in Java always experience various disturbances that result in forest degradation. Alternatively, if FMU can control the rate of degradation to less than 2% per year (as occurred in KPH Kebonharjo in the period 1977–1987), the FMU would still gain relatively high benefit of emission reduction (average of 152,450 tCO2e/yr or equal to 8.56 tCO2e/ha/yr). These findings confirmed that avoiding forest degradation is a must to gain more benefits of emission reduction through plantation forests management.

Community forest management can also be used as an option to reduce emission. The case study of community forests managed by Koperasi Hutan Jaya Lestari (KHJL, South Konawe, Sulawesi) showed that KHJL could gain the benefit of emission reduction up to 1.03 MtCO2e for 30 years (average of 34,459 tCO2e/yr) if forest managers increase harvestable diameter limit from 20 cm to 30 cm coupled with replanting of harvested trees. The emission reduction benefit can be increased to a total of 3.1 MtCO2e or average of 103,469 tCO2e/yr if KHJL expands their FMU by recruiting new member, replanting, and regulating harvestable diameter limit.

This study concluded that SFM practice (especially in natural production forests, plantation forests, and community forests) can be used as a promising option for reducing emissions in the REDD+ mechanism. Several strategies for reducing emissions at FMU level are: 1) controlling harvest level, 2) reducing logging damages, 3) minimizing land clearing for infrastructures, 4) eliminating or avoiding forest degradation, 5) conducting rehabilitation or restoration of unproductive areas, 6) tending residual stands to improve regrowth, 7) allocating some portions of production areas to protected areas, 8 ) selecting appropriate silvicultural systems that increase carbon stocks, and 9) optimizing growing space for maximizing forest biomass. Forest managers, however, need to be aware that trade-offs between emission reduction and sustained timber yield objectives are unavoidable. Incentive systems for forest managers, therefore, need to be formulated to support the implementation of REDD+ mechanism through SFM practices.

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Metode Burns, masihkah relevan untuk Perhutani?

Tiryana, T. 2011. Metode Burns, masihkah relevan untuk Perhutani? Duta Rimba No. 40-Th.6/Des 2011. (in Bahasa Indonesia)

Akhir-akhir ini wacana tentang metode pengaturan hutan (forest regulation) di Perhutani semakin mengemuka. Banyak pihak yang menganggap bahwa metode Burns, yang mendasari lahirnya SK 143/Kpts/Dj/I/1974 tentang Peraturan inventarisasi dan penyusunan RPKH kelas perusahaan jati, kurang layak dipakai untuk pengaturan hutan pada kondisi saat ini. Hasil penilaian Smartwood (2000) di KPH Kebonharjo turut memperkuat anggapan tersebut. Namun demikian, belum banyak pihak yang membahas mengapa metode tersebut kurang layak diterapkan. Tulisan ini dimaksudkan untuk memberikan pemahaman mengenai metode Burns dengan mengungkap asal-usulnya, menganalisis kelemahannya, serta memberikan rekomendasi untuk penyempurnaan metode pengaturan hutan di Perhutani.

=> Artikel selengkapnya (only in Bahasa Indonesia): PDF-1 (high quality, 3.16 MB) atau PDF-2 (low quality, 908 KB)

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Modeling survival and destruction of teak plantations in Java, Indonesia

Tiryana, T., Tatsuhara, S., and Shiraishi, N. 2011. Modeling survival and destruction of teak plantations in Java, Indonesia. Journal of Forest Planning 16: 35–44. Available at: http://ci.nii.ac.jp/naid/110008799927/ or here: http://tinyurl.com/7bg5mwp

Abstract

Teak plantations in Java show severely declining productivity due to various disturbances. The risk of stand destruction, however, is still ignored in determining annual allowable cuts, partly due to the lack of reliable methods to estimate the rate of stand destruction. This study therefore proposed an alternative method, based on the theory of survival analysis coupled with forest register data, for estimating survival probability and destruction rate of teak plantations. We used the forest register data of teak plantations in Kebonharjo, Central Java, for the period 1977–2007. Survival and destruction of plantations were modeled using probability distribution models. To estimate model parameters, we used the maximum likelihood estimation method designed for left-truncated and right-censored data. Results showed that survival probability and destruction rate varied over stand age and planning period. Rates of stand destruction were relatively low (< 2% per year) in the period 1977‒1987, but increased up to 3% and 14% per year in the period 1987‒1997 and 1997‒2007, respectively. The highest rate of destruction mostly occurred in young stands (≤ 30 years old), indicating an alarming condition for the sustainability of teak plantations. The survival and destruction models are useful for forest managers to quantify the range of historical variability in forest disturbances and to support the development of alternative harvest scheduling methods that incorporate the risk of stand destruction for teak plantations in Java. The proposed method can also be applied to other regions, especially when only forest register data are available.

Keywords: teak, destruction rate, survival analysis, Weibull, log logistic

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Empirical models for estimating the stands biomass of teak plantations in Java, Indonesia

Tiryana, T., Tatsuhara, S., and Shiraishi, N.  2011.  Empirical models for estimating the stands biomass of teak plantations in Java, Indonesia.  Journal of Forest Planning16: 177‒188. Available at: http://ci.nii.ac.jp/naid/110009357768/ or here: http://tinyurl.com/75tmr3y

Abstract

The development of empirical biomass models has gained a great deal of attention during recent decades. These models have been constructed to facilitate the quantification of forest biomass and carbon sequestration benefits, but few empirical models exist for estimating the stand biomass of teak (Tectona grandis L.f.) plantations. This study therefore sought to develop stand-level biomass models that use minimum input data for teak plantations in Central Java, Indonesia. Stand biomass and other stand variables were derived from forest inventory data in Balo (Kebonharjo, Central Java). We used linear and nonlinear regression to develop four types of biomass models: volume to biomass, basal area to biomass, age to biomass, and age and basal area to biomass. These models were then validated using an independent data set. Results indicated that teak stand biomass was accurately estimated using the volume-to-biomass model. In addition, while the accuracy of the age and basal area-to-biomass model was comparable to that of the volume-to-biomass model, the basal area-to-biomass and age-to-biomass models were less accurate. Depending on the availability of input data, at least one of these models will be appropriate for estimating teak stand biomass. Thus, these models should prove quite valuable in supporting the multipurpose management of teak plantations in Java.

Keywords: teak plantations, biomass, carbon, stand-level model, multipurpose management

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Quantitative Models for Supporting Multipurpose Management Planning of Teak Plantations in Java, Indonesia

Tiryana, T.  2010.  Quantitative Models for Supporting Multipurpose Management Planning of Teak Plantations in Java, Indonesia.  PhD thesis, The University of Tokyo, Japan.

Abstract

Current forest management planning of teak plantations in Java, Indonesia, has limitations in supporting sustainable forest management (SFM).  It ignores the potential risk of destruction in determining annual allowable cuts, whereas forest destruction seems to be an inevitable problem in teak plantations.  In addition, the existing harvest scheduling method only concerns with achieving sustained timber yields, while SFM demands for achieving sustainability of multiple forest benefits. Up to now, however, there is still lack of management planning tools for supporting SFM of teak plantations.  This study aimed to develop quantitative models for supporting multipurpose management planning (especially timber production and carbon sequestration) of teak plantations at risk of destruction.

Considering the lack of reliable and practical methods for estimating survival probability and destruction rate of teak plantations, this study proposed an alternative method based on the theory of survival analysis coupled with forest register data. The forest register data were obtained from Kebonharjo forest management unit (FMU), Central Java, for the period 1977–2007. Survival and destruction of the plantations were modeled using probability distribution models. Model parameters were estimated using the maximum likelihood estimation method designed for left-truncated and right-censored data.  Results showed that survival probability and destruction rate varied over stand age and planning period.  The rates of stand destruction were relatively low (<2% per year) in the period 1977–1987, but increased up to 3% and 14% per year in 1987–1997 and 1997–2007, respectively. The highest rate of destruction mostly occurred in young stands (≤ 30 years old), implying an alarming condition for the sustainability of teak plantations. Survival and destruction models are useful for forest managers to evaluate the risk of stand destruction over a specific planning period and to support the development of alternative harvest scheduling methods for teak plantations in the presence of forest destruction.

Despite a wide array of forest benefits, this study concerned on quantifying carbon sequestration benefits by developing empirical biomass models for teak plantations. Stand biomass and other stand variables were derived from forest inventory data of the FMU.  Linear and nonlinear regression models were used to develop four types of biomass models: volume-to-biomass, basal area-to-biomass, age-to-biomass, and age and basal area-to-biomass, which were validated using an independent data set.  Results indicated that teak stand biomass was accurately estimated using the volume-to-biomass model.  While the accuracy of the age and basal area-to-biomass model was comparable to that of the volume-to-biomass model, the basal area-to-biomass and age-to-biomass models were less accurate.  Depending on the availability of input data, at least one of these models will be appropriate for estimating teak stand biomass.  These models should prove quite valuable in supporting the multipurpose management of teak plantations.

Furthermore, this study developed an alternative harvest scheduling model for optimizing multiple benefits (i.e., timber and carbon sequestration) of teak plantations at risk of destruction.  The proposed model simulated the dynamic of age-class structures from one (a 5-year) period to another and then optimized harvest levels through a planning horizon using linear programming models.  The optimal harvest levels were sought for three management scenarios: optimizing harvest volumes, optimizing net present values (NPV), and optimizing NPV while increasing carbon stocks.  Each scenario was evaluated using four destruction rates (i.e., zero, low: 4.4−6.3% per period, medium: 9.4−15.9% per period, and high: 18.5−49.6% per period) and three cutting-age limits (i.e., 51, 61, and 71 years).  The results confirmed that increasing destruction rates resulted in the reduction of harvest levels, financial benefits, carbon stocks, and led to imbalance age-class structures. Meanwhile, reducing cutting-age limits increased harvest levels and financial benefits, but reduced mature stands and carbon stocks.  Although incorporating carbon sequestration benefits into the management objectives resulted in the reduction of financial benefits, such multipurpose management scenario produced better forest structures than timber management.  This study suggested that the proposed harvest scheduling model provides greater flexibility for forest managers to develop appropriate management scenarios at risk of destruction; hence, it can be used as an alternative harvest scheduling model for supporting multipurpose management planning of teak plantations.

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Assessing sustainability of timber production of teak plantations under the risk of destruction

Tiryana, T., Tatsuhara, S., and Shiraishi, N. 2010.  Assessing sustainability of timber production of teak plantations under the risk of destruction.  The Japanese Forestry Society Congress 121, April 3, 2010, Tsukuba-Japan (oral presentation).  Available at: http://www.jstage.jst.go.jp/article/jfsc/121/0/41/_pdf

Extended Abstract:

1. Introduction

Recently, there has been increasing public concerns on the sustainability of timber production of teak plantations in Java, Indonesia, mainly because most of the plantations are dominated by young stands and they always face with the high risk of destruction.  A number of criteria and indicators for sustainable forest management also require forest managers to demonstrate that their forests could produce a perpetual sustained yield of timber.  However, the existing method to determine annual allowable cut (AAC) of teak plantations in Java, which is based on a neoclassical method of area and volume controls, is less suitable for assessing the sustainability of plantations under the risk of destruction.  In this study, we proposed an alternative method to assess the effect of forest destruction to the sustainability of timber productions and to determine optimal harvest levels of teak plantations under the risk of destruction.

2. Methods

This study was conducted in Kebonharjo forest management unit (FMU), located in Central Java, Indonesia.  Teak plantations in the FMU are dominated by young stands (<30 years). We used a dynamic linear programming (LP) method proposed by Reed and Errico (1986) to project a 5-year age class distributions from one (a 5-year) period to another and then optimize their harvest levels through a 140-year planning horizon.  The projection of age class distributions was conducted using probability transition matrices consisting of destruction and survival probabilities, which were derived from a survival analysis (Tiryana et al., 2009).  To estimate timber yields, we used the existing yield table of middle site class (for clear-cutting and thinning yields) and the lowest site class (for salvage-cutting yield).  Optimal harvest levels under four destruction rates, i.e. zero, low (4.4−6.3% per period), medium (9.4−15.9% per period), and high (18.5−49.6% per period) were determined by developing 12 LP models with the objective of maximizing total harvest volume (of clear-cutting, salvage-cutting, and thinning) subject to the constraints of sequential harvest flows (±10%) and minimum cutting-ages (of 71, 61, and 51 years).  The optimal solutions were compared to each other to analyze the trend of timber volume and age class distribution at the end of planning horizon.

3. Results and Discussion

The optimal harvest levels of teak plantations were greatly affected by the rate of destructions.  Depending on the limit of cutting-age used in the LP models, the harvest levels generally decreased with increasing the destruction rates.  Compared to the no destruction scenarios, total harvest volumes decreased to about 0.6−2.6%, 3.6−10.3%, and 14.1−25.8% when the destruction rates were assumed to be low, medium, and high, respectively.  While the harvest levels under the high destruction rates decreased over planning periods, the harvest levels under the scenario of low and medium destruction rates tended to gradually increase until the rotation periods and then gradually decrease towards the end of planning horizon.  This behavior is reasonable because from one period to another the plantations grow continuously and the use of minimum cutting-age constraints allows the increase of mature stands.  The increase of allowable harvest levels on a forest with less mature stands was also reported by Armstrong (2004).  In addition, reducing the limit of cutting-ages from 71 to 61 or 51 years increased the total harvest volume up to 15.2% (low destruction), 9.4% (medium destruction), and 1.5% (high destruction).  However, reducing the length of rotations tended to produce ending age class distributions with less mature stands (≥30 years old).  Although the present teak plantations are dominated by young stands, our results confirmed that the FMU can maintain the sustainability of timber production if they can control and minimize forest destructions.  More importantly, forest managers should set up AAC within the range of harvest levels estimated under the high and low destruction rates.  In this context, the proposed method can help forest managers to determine an appropriate harvest level under a certain assumption of destruction rate.  The proposed method can also be extended to include other management objectives (e.g. maximize net present value) and non timber benefits (e.g. carbon sequestration).  These issues will be investigated in our further studies.

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Modeling spatial variation in stand volume of Acacia mangium plantations using geographically weighted regression

Tiryana, T., Tatsuhara, S., and Shiraishi, N.  2010.  Modeling spatial variation in stand volume of Acacia mangium plantations using geographically weighted regression.  FORMATH 9: 103‒122. (in English). Available at: http://www.formath.jp/publication/book/vol09/Vol9/Vol9_p103_122.pdf  or here!

Abstract

Stand volume can be estimated from other stand variables by using multiple linear regression (MLR) or other ordinary regression models.  MLR, however, only produces global parameter estimates that cannot reveal spatial variations in stand variables.  In this study, we used a geographical weighted regression (GWR) method to investigate local spatial variations in the relationship between stand volume, stand age, and basal area of Acacia mangium plantations, and to examine whether a GWR model could provide better prediction accuracy than an MLR model.  Stand data and geographical coordinates were obtained from 247 plantation sample plots.  We analyzed the data using MLR and GWR methods by formulating a linear model that relates stand volume to stand age and basal area.  Performance of the GWR model was compared with the MLR model in terms of their parameter estimates and goodness-of-fit statistics.  We found that the GWR model was not only able to reveal local spatial variations in the relationship between stand volume, stand age, and basal area, but it also produced better prediction accuracy than the MLR model.  The GWR model reduced AIC by 2%, increased R2adj up to 3%, and reduced RMSE by 14%, compared with those of the MLR model.  The GWR model, therefore, could be useful for modeling spatial variations in stand attributes that cannot be revealed by ordinary regression models.

Keywords: stand volume, spatial variation, geographically weighted regression (GWR)

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Applicability of kriging to predict spatial distribution of carbon stocks of Acacia mangium plantations

Tiryana, T., Tatsuhara, S., and Shiraishi, N.  2009.  Applicability of kriging to predict spatial distribution of carbon stocks of Acacia mangium plantations.  Journal of Forest Planning 14(1): 17‒26. Available at: http://ci.nii.ac.jp/naid/110009357740 or here: http://tinyurl.com/6q8o9ea

Abstract

The prediction of carbon stocks is essential to evaluate the environmental benefits of forests. Although carbon stocks can be predicted by combining sample plots from several or all forest stands, this approach cannot directly provide spatial information on the distribution of the carbon stocks. We investigated the applicability of kriging as an alternative method to spatially predict the carbon stocks of an Acacia mangium plantation in Indonesia. The carbon stock data obtained from 247 sample plots and variogram analysis were used to characterize and model the spatial autocorrelation of the carbon stocks. The spatial prediction of carbon stocks was carried out using ordinary kriging (OK), universal kriging (UK), and co-kriging (CK) methods. UK used the geographical coordinates as a secondary variable, whereas CK used stand age. The prediction accuracy of the kriging methods was assessed using cross-validation. The carbon stocks were spatially autocorrelated up to a distance of 3600 m and tended to be more similar along the direction of 135. The kriging methods produced similar prediction maps of the spatial distribution of the carbon stocks. There were no significant differences among the kriging predictions and their standard deviations. Cross-validation, however, confirmed that CK performed better than OK and UK. The predicted carbon stocks varied from 7.25 to 37.95 tC/ha, with a standard deviation ranging from 9.44 to 12.21 tC/ha. Thus, kriging can be used as an alternative method to predict the spatial distribution of carbon stocks or other forest attributes.

Keywords: carbon stocks, geostatistics, kriging, spatial autocorrelation, variogram

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