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
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