An Improved Method for Estimating the Transition Probability Using Diameter Growth in Even-aged Forest Stands

The method of Zeng et al. (1991) employed diameter growth to estimate the transition probability of the matrix model in uneven-aged forest stands. In this paper the Weibull distribution for even-aged forest stands instead of uniform distribution chosen by Zeng is used. By comparing the results of the improved method with those of the original method of Zeng, it turns out that the improved method of Zeng given in this paper is more efficient.

Influence of Residual Basal Area on Longleaf Pine (<i>Pinus palustris</i>Mill.) First Year Germination and Establishment under Selection Silviculture

Even-aged silvicultural methods have been successfully used to manage longleaf pine (Pinus palustris Mill.) forests for wood production;however, successful use of uneven-aged methods to manage this ecosystem is less well documented. In this study, the effects of varying levels of residual basal area (RBA) (9.2, 13.8, and 18.4 m2·ha-1) on longleaf pine germination and establishment under selection silviculture marked using the Proportional-B method were observed. In addition to RBA, photosynthetically active radiation (PAR) was measured, and the relationships between light penetration, germination, and growth were examined. The study found an inverse relationship between RBA and the number of germinants, but the mortality of germinants was not influenced by RBA. PAR also had a significant positive effect on germination, but, did not affect mortality of germinants. In addition, RBA and PAR had no effect on mortality or growth of planted seedlings. Continued monitoring of seedling recruitment into the stand will be required to determine the efficacy of the system. However, nothing in the first year data suggests that this approach will not be successful in sustaining an uneven-aged stand.

Stand management optimization——the role of simplifications

Background:Studies on optimal stand management often make simplifications or restrict the choice of treatments,Examples of simplifications are neglecting natural regeneration that appears on a plantation site,omitting advance regeneration in simulations,or restricting thinning treatments to low thinning(thinning from below).Methods:This study analyzed the imparts of simplifications on the optimization results for Fennoscandian boreal forests.Management of pine and spruce plantations was optimized by gradually reducing the number of simplifying assumptions.Results:Forced low thinning,cleaning the plantation from the natural regeneration of mixed species and ignoring advance regeneration all had a major impact on optimization results.High thinning(thinning from above) resulted in higher NPV and longer rotation length than thinning from below.It was profitable to leave a mixed stand in the tending treatment of young plantation.When advance regeneration was taken into account,it was profitable to increase the number of thinnings and postpone final felling.In the optimal management,both pine and spruce plantation was gradually converted into uneven-aged mixture of spruce and birch.Conclusions:The results suggest that,with the current management costs and timber price level,it may be profitable to switch to continuous cover management on medium growing sites of Fennoscandian boreal forests.

Simultaneous optimization of even flow and land and timber value in forest planning:a continuous approach

Background:Forest management planning involves deciding which silvicultural treatment should be applied to each stand and at what time to best meet the objectives established for the forest.For this,many mathematical formulations have been proposed,both within the linear and non-linear programming frameworks,in the latter case generally considering integer variables in a combinatorial manner.We present a novel approach for planning the management of forests comprising single-species,even-aged stands,using a continuous,multi-objective formulation(considering economic and even flow)which can be solved with gradient-type methods.Results:The continuous formulation has proved robust in forest with different structures and different number of stands.The results obtained show a clear advantage of the gradient-type methods over heuristics to solve the problems,both in terms of computational time(efficiency)and in the solution obtained(effectiveness).Their improvement increases drastically with the dimension of the problem(number of stands).Conclusions:It is advisable to rigorously analyze the mathematical properties of the objective functions involved in forest management planning models.The continuous bi-objective model proposed in this paper works with smooth enough functions and can be efficiently solved by using gradient-type techniques.The advantages of the new methodology are summarized as:it does not require to set management prescriptions in advance,it avoids the division of the planning horizon into periods,and it provides better solutions than the traditional combinatorial formulations.Additionally,the graphical display of trade-off information allows an a posteriori articulation of preferences in an intuitive way,therefore being a very interesting tool for the decision-making process in forest planning.