Forest Investment Account (FIA) - Forest Science Program
FIA Project Y113162

    Crown competition, crown efficiency, tree growth and site type: quantification with terrestrial LIDAR
Project lead: Bruce Larson (University of British Columbia)
Contributing Authors: Ducey, Mark J.; Astrup, Rasmus; Pretzsch, Hans C.; Seifert, Stefan; Larson, Bruce C.; Coates, K. David; Tikina, Anna
Subject: Forest Investment Account (FIA), British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
Tree growth in complex stands is affected by intra- and inter-specific competition for growing space, site-specific nutrient and moisture availability, and spatial pattern of neighborhood trees of different canopy positions (e.g. Canham et al. 2006, Kobe 2006). To predict stand development and growth of complex stands we need to understand the how these factors interplay. To date, it is not fully described or understood how: (1) resource availability affects species-specific crown development patterns, (2) how crown efficiency is affected by moisture or nutrient availability, (3) how variation in crown development and crown efficiency account for differentiation of stand development patterns along a resource gradient, and (4) the relation between crown size and tree growth. These topics are addressed through the proposed study.

We propose to investigate crown structure in three dimensions and determine how crown efficiency (biomass increment/growing space (kg y-1 m2)) and crown structure is affected by a gradient of competition and below-ground resources. Quantification of three dimensional crown structures with traditional measurement techniques is very time consuming, expensive, and associated with large measurement errors. In this project, we will overcome the measurement impediments of past research through application of the new and innovative terrestrial LIDAR technology (e.g. Henning and Radtke 2006a, Henning and Radtke 2006b, Huang et al. 2007). Terrestrial LIDAR can create a three-dimensional model of all individual trees in an investigated plot (see examples in Figure 1, 2, & 3).

The 3D LIDAR data in combination with existing measurements on resource availability and growth rates will allow us to test hypothesis of general interest to foresters and ecologists. In this project, we will as a minimum test the following five hypotheses:

Hypothesis 1: Crown size is only dependent on neighbourhood composition not on below-ground resources

Hypothesis 2: Crown efficiency (biomass increment/growing space (kg y-1 m2)) depends on the crown size but not on crown shape

Hypothesis 3: Crown efficiency is positively correlated to below-ground resource availability

Hypothesis 4: Crown surface/per hectare increases with below-ground resources but the crown efficiency remains constant

Hypothesis 5: Due to asymmetric competition increased below-ground resources improve the competitiveness of suppressed and understory trees

In the past, these hypotheses were hard to test due to difficulty in quantifying the three dimensional nature of the topic. The application of terrestrial LIDAR allows us to efficiently obtain 3D information and hence to effectively test these novel hypotheses.

In the proposed study, we will utilize a set of existing research plots established across a gradient of below-ground resources (dry and poor to wet and rich) and competitive neighbourhoods (density and species) in the sub-boreal spruce zone in central British Columbia. The established plots have information related to site-type and resource availability.

Application of terrestrial LIDAR is a new development in silvicultural and ecological research.
To our knowledge, there has been no published comparison of results obtained with terrestrial LIDAR using different scanners at identical points within the same forest stand, despite the fact that commercially available instruments such as the Riegl and the Leica differ in terms of light wavelength, beam width, and intensity. In this project, we will mitigate this methodological gap by conducting scans over identical benchmarks with both a Riegl and a Leica LIDAR platform. These benchmark scans will allow us to: (a) compare scanner performance, (b) compare algorithms for extracting tree location, stem taper, and crown shape, and (c) compare the performance of the two scanners to existing traditional tree allometry measurements. Thus, this project will not only test interesting hypotheses relating to crown dynamics but also contribute to the methodological knowledge of application of terrestrial LIDAR in forest research and measurement.

References for Project Description and Methods and Experimental Design sections:

Binkley, D., 2004. A hypothesis about the interaction of tree dominance and stand production through stand development. Forest Ecology and Management 190:265-271.

Burnham, K.P. and D.R. Anderson. 2002. Model Selection and Multimodel Inference: a Practical Information-Theoretical Approach. Springer-Verlag, New York.

Canham, C. D., LePage, P. and Coates, K. D. 2004. A neighborhood analysis of canopy tree competition: effects of shading versus crowding. Can. J. For. Res. 34, 778-787.

Canham, D.C., Papaik, M.J., Uriarte, M., McWilliams, W.H., Jenkins, J.C., Twery, M. 2006. Neighborhood analysis of canopy tree competition along environmental gradients in New England forests. Ecological applications, 16: 540-554.

Chasmer, L.,
Related projects:  FSP_Y091162FSP_Y102162


Final Technical Report (1.4Mb)
Extension note (0.8Mb)
Comparison of forest inventory and canopy attributes ... (1.1Mb)

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Updated May 19, 2011 

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