Response of sugar maple (Acer saccharum, Marsh.) tree crown structure to competition in pure versus mixed stands

Published Date
15 August 2016, Vol.374:20–32, doi:10.1016/j.foreco.2016.04.047

Title 
Response of sugar maple (Acer saccharum, Marsh.) tree crown structure to competition in pure versus mixed stands

• Author 

• Martin-Ducup Olivier ^a,,
• Schneider Robert ^a,
• Fournier Richard A. ^b,

• aChaire de recherche sur la forêt habitée, Département de biologie, chimie et géographie, Université du Québec à Rimouski (UQAR), 300 allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
• bCentre d’Applications et de Recherches en Télédétection (CARTEL), Département de géomatique appliquée, Université de Sherbrooke, 2500, boul. de l’université, Sherbrooke, Québec J1K 2R1, Canada

Received 12 January 2016. Revised 14 April 2016. Accepted 23 April 2016. Available online 2 May 2016.

Highlights

• •
  New competition indices (CI) and crown metrics using TLS data are proposed.
• •
  Competitive pressure for sugar maple is higher in pure than in mixed stands.
• •
  Canopy space occupation is better in mixed than in pure stands.
• •
  TLS based CI are good predictors of crown structure variability.

Abstract

Characterizing tree crown structure and quantifying its relationships with the surrounding environment is of critical importance in forest ecology and management. These relationships depend heavily on species plasticity and local competition for light. It is however difficult to study forest canopies due to their inaccessibility and complexity. The objective of this study was thus to use terrestrial laser scanning (TLS) data to overcome the limits of traditional canopy studies and to quantify the differences in sugar maple (Acer saccharum, Marsh.) tree crowns between stands with different composition and developmental stage. A total of 72 sugar maple trees and their immediate surroundings were scanned using a TLS. We developed eight crown structure metrics and three competition indices using TLS data. We found that competitive pressure is higher in pure stands, when compared to mixed ones. Sugar maple crowns were bigger, less dense, and more sinuous and open in mixed stands. Moreover, differences between trees were generally more pronounced for trees in mature stands. Finally, TLS competition indices are better predictors of crown metric variability than stand type, highlighting the potential of TLS data to quantify tree competition and space occupancy. Our competition indices are good proxies of the canopy structure and thus seem promising to predict tree growth.

Keywords

• Crown plasticity
• Competition index
• Crown volume
• Alpha shape
• Convex hull
• Structure–environment loop

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 Table A.1

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• ⁎ 
  Corresponding author.

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http://www.sciencedirect.com/science/article/pii/S0378112716302213