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Terrestrial laser scanning (TLS) data on tree crown morphology and neighbourhood competition from both Cuellar and Alto Tajo, Spain

Citation

Owen, Harry; Lines, Emily; Flynn, William (2021), Terrestrial laser scanning (TLS) data on tree crown morphology and neighbourhood competition from both Cuellar and Alto Tajo, Spain, Dryad, Dataset, https://doi.org/10.5061/dryad.0k6djhb0m

Abstract

1. Tree crown morphology is a key driver of forest dynamics, determining not only the competitiveness of an individual but also the competitive effect exerted on neighbouring trees. Multiple ecological theories, including Metabolic Scaling Theory (MST), predict crown morphology from first principles, but typically lack consideration of competition. The accurate quantification of crown morphology to test theoretical predictions, and the canopy interactions that could alter them, has historically been limited by the simplicity and associated error of traditional crown measurements.

2. In this study, we calculate high resolution two and three-dimensional crown metrics from Terrestrial Laser Scanning data for 1441 Pinus. sylvestris, P. nigra, Quercus. faginea and Q. ilex trees from a water-limited forest community in central Spain and test height-crown metric scaling relationships. We demonstrate new TLS methods to define symmetric and asymmetric neighbourhood metrics based on tree height, crown size and neighbour projected crown area, and test the importance of neighbourhood genus diversity on crown morphology by separating competition from congeneric and heterogeneric neighbours.

3. Competition negatively impacted all crown metrics except crown depth where only P. nigra showed sensitivity. Asymmetric competition was the strongest driver of pine crown morphology, but oaks were more sensitive to symmetric competition, in line with shade tolerance expectations. Congeneric competition reduced Q. faginea crown size and changed its shape, but we found no significant effects of heterogeneric neighbours. Most species and crown dimensions had height-crown scaling exponents below those predicted by MST, which may be due to water-limitation effects. Pines and oaks showed large differences in crown depth to height scaling, with the former shallower and the latter deeper, in contrast to theoretical predictions.

4. Synthesis. Our study is the first to demonstrate the ability of TLS to characterise crown morphology from leaf-wood separated clouds and competitive neighbour effects in a water-limited forest community, and to use TLS metrics to test ecological crown scaling theory. Most crown metrics scaled below theoretical predictions. Pines were more sensitive to competition by larger neighbours and oaks to crowding from all neighbours, with competition from neighbours of the same genus having a consistently negative effect.

Methods

See published article in Journal of Ecology for all methodological information. 

Usage Notes

The file focaltree_dataset.csv includes:

Each tree id with the prefix "alt" and "cue" corresponding to alto tajo and cuellar field sites. 

Fields 1:2 contain tree height and dbh for each focal tree. DBH values of 0 are NA's. 

Fields 4:9 contain crown morphological metrics. 

Fields 10:11 contain species and genus.

Fields 12:17 contain neighbourhood competition metrics. 

Field 18 contains binary column on whether species is [1] or isn't [0] a miltistemmed tree. 

Field 19 contains plot ID. 

Field 20 contains site ID.

Funding

Natural Environment Research Council