Journal articles by Jerome K Vanclay
Annals of Forest Science, 2013
Context: A 20 year old Nelder wheel planted with hoop pine (Araucaria cunninghamii Aiton ex D.Don... more Context: A 20 year old Nelder wheel planted with hoop pine (Araucaria cunninghamii Aiton ex D.Don) and Queensland maple (Flindersia brayleyana F.Muell.) in 18 spokes and 8 rings represents nominal point densities of 3580, 2150, 1140, 595, 305, 158, 82 and 42 stems/ha and offers an opportunity to examine competition and spatial interaction between these two species. Aims: To evaluate the intra-and inter-specific competition between two contrasting tree species, and determine the distance over which competition can be observed. Methods: Competition was estimated using Hegyi's index, implemented using the Simile visual modelling environment, and calibrated using non-linear least squares with PEST. Results: Interactions were detected between pairs of stems closer than D ij <40(d i +d j ) where D is distance (cm) and d is stem diameter (cm dbh). F. brayleyana trees surrounded by A. cunninghamii trees suffer negligible competition whereas A. cunninghamii surrounded by F. brayleyana trees experience strong competition. Forty times diameter offers a useful guide to the extent of competition in even-aged stands planted with these species. Competition can be observed empirically when pairs of trees are closer than 40 times the sum of their diameters, but the intensity of the competition may vary considerably with species.
Calibration of the self-thinning frontier in even-aged monocultures is hampered by scarce data an... more Calibration of the self-thinning frontier in even-aged monocultures is hampered by scarce data and by subjective decisions about the proximity of data to the frontier. We present a simple model that applies to observations of the full trajectory of stand mean diameter across a range of densities not close to the frontier. Development of the model is based on a consideration of the slope s = ln(N t /N t-1 )/ln(D t /D t-1 ) of a log-transformed plot of stocking N t and mean stem diameter D t at time t. This avoids the need for subjective decisions about limiting density and allows the use of abundant data further from the selfthinning frontier. The model can be solved analytically and yields equations for the stocking and the stand basal area as an explicit function of stem diameter. It predicts that self-thinning may be regulated by the maximum basal area with a slope of -2. The significance of other predictor variables offers an effective test of competing self-thinning theories such Yoda's -3/2 power rule and Reineke's stand density index.
Forest Ecology and Management, 1994
Although logging ceased in the tropical rainforests of north Queensland following their World Her... more Although logging ceased in the tropical rainforests of north Queensland following their World Heritage Listing in 1988, they provide a good basis for simulation studies on sustainability of timber harvesting as reliable logging records, inventory and growth data are available. A growth model for these forests has been developed and published. The growth model is dynamic, responding to changes in stand density, composition and management history. A harvesting simulator predicts the trees removed by selection logging, and predicts changes in the residual stand. Simulation studies employ cutting cycle analysis and yield scheduling to demonstrate the sustainability of harvesting. These studies indicate that selection harvesting could sustain a viable timber harvest of about 60 000 m 3 year -1 . These results are indicative rather than definitive, as the model has not yet been formally validated with independent data.
Forest Ecology and Management, 1995
Informed plantation management requires a good database, since the quality of information depends... more Informed plantation management requires a good database, since the quality of information depends on the quality of data, girofih models and other planning tools. There are several important questions concerning permanent plots: how many plots, where to put them, and how to manage them. Plot measurement procedures are also important. This paper illustrates graphical procedures to evaluate existing databases, to identify areas ofweakness, and to plan remedial sampling. Two graphs, one of site index versus age, another with stocking versus tree size, may provide a good summary of the site and stand conditions represented in the database. However, it is important that these variables, especially site index, can be determined reliably. Where there is doubt about the eflicacy of site index estimates, it is prudent to stratify the database according to geography, soil/geology or yield level (total basal area or volume production). Established perrnanent ptot systems may sample a limited range of stand conditions, and clinal designs are an efficient way to supplement such data to provide a better basis for silvicultural inference. Procedures are illustrated with three data sets: teak plantations in Burma, Norway spruce in Denmark, and a clinal spacing experiment in India.
Use-values have been advocated as a tool to compare the value of not just individual species, but... more Use-values have been advocated as a tool to compare the value of not just individual species, but also of plant families and forest types to local people, in order, for example, to identify species or habitats in need of special management or conservation. We estimated use-values in three forest types (upper restinga, lower restinga, tahuampa) on the Amazon flood plain south of Iquitos (Peru), compared two methodologies, identified the most valuable species and contrasted these valuations with the actual use of forest resources in local villages. A new method for estimating use-values was contrasted with the method of Phillips and Gentry (1993a). Despite philosophical and procedural differences, estimates were highly correlated (R2=0.86). We discuss limitations of both methods and suggest some possible enhancements. The need to discriminate between past, present and potential uses is emphasised.
Canadian Journal of Forest Research, 1992
VANCLAY, J.K. 1992. Modelling regeneration and recruitment in a fopical rain forest. Can. J. For.... more VANCLAY, J.K. 1992. Modelling regeneration and recruitment in a fopical rain forest. Can. J. For. Res. 22: 1235Res. 22: -1248 A two-stage model predicts the recruitment (i.e., the number of stems reaching or exceeding l0 cm DBH) of the 100 species that account for 97Vo of all the recruitment observed on 217 permanent sample plots in ihe tropical rain forest of north Queensland. The first stage predicts the probability of the occurrence of any recruitment from stand blsal area and the presence of that species in the existing stand. These probabilities can be implemented stochastically, or deterministically by summing the probabilities and initiating recruitment on unity. The second stage indicates the expected amount of recruitment, given that it is known to occur, and employs stand basal area, the relative number of trees of that species in the stand, and site quality. This approach is easily implemented in growth models and planning systems. VRNCLRY, J.K. 1992. Modelling regeneration and recruitment in a tropical rain forest. Can. J. For. Res. 22 : 1235-1248.
Forest Science, Dec 1, 1991
Abstract: A single growth model can provide both deterministic and stochastic predictions which a... more Abstract: A single growth model can provide both deterministic and stochastic predictions which are compatible. Change may be expressed using probabilistic functions which can represent proportions of populations or probabilities for individuals. The former represents determinism while the latter enables the stochastic implementation. The same functional relationships may thus be used to generate compatible deterministic and stochastic predictions. All components of forest growth and change, including diameter increment, ...
Uploads
Journal articles by Jerome K Vanclay