Estimates of Tree Canopy Closure and Basal Area as Proxies for Tree Crown Volume at a Stand Scale

Guntis Brūmelis,Indrikis Krams,Iluta Dauškane,Didzis Elferts,Linda Strode,Tatjana Krama

doi:10.3390/f11111180

Guntis Brūmelis, Indrikis Krams + Show 4 more

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https://doi.org/10.3390/f11111180

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Abstract

Research Highlights: Studies on tree canopy dwelling species often require simple proxies of tree canopy volume estimated at a stand level. These include allometrically related tree crown parameters such as crown area and basal area, and canopy cover. Background and Objectives: In monoculture Scot’s pine and mixed pine/Norway spruce forest, we aimed to test the relationships between tree diameter at breast height (DBH) and tree crown volume at a tree level and between densitometer canopy closure estimates and tree crown volume at a stand level. Materials and Methods: The study was carried out in eastern Latvia (hemiboreal zone) in monoculture pine and mixed coniferous stands. On a subset of trees in 22 forest stands (88 100 m2 plots), we determined the best regression model that described the relationship between tree DBH and crown volume for spruce and pine. Tree crown volume at a stand level was determined from the individual tree volume estimates calculated from these regression models. On a stand level, we also calculated regression models for densitometer closure estimates versus total crown volume for pine and mixed stands. Results: Linear mixed effects models showed significant relationships between DBH and crown volume for pine (R2 = 0.63) and spruce (R2 = 0.40), indicating that basal area could be used as a predictor of crown volume at a stand level. Variance explained by a regression model of canopy closure versus tree crown volume at a stand level was R2 = 0.52. Conclusions: Tree basal area and crown closure can be used as proxies of tree crown volume at a stand scale in monoculture stands. In mixed stands estimates of crown volume based on basal area need to be calculated separately for each tree species, while canopy closure will provide an estimate of total crown volume.

Highlights

IntroductionThe fitness of individual organisms, are often determined by the quality of their habitats
Species richness and survival, and the fitness of individual organisms, are often determined by the quality of their habitats
In mixed stands estimates of crown volume based on basal area need to be calculated separately for each tree species, while canopy closure will provide an estimate of total crown volume

Summary

Introduction

The fitness of individual organisms, are often determined by the quality of their habitats. Forest habitat selection is mostly a function of a vegetation structure [1]. Safety and food availability are among the contested resources and belong to the most important habitat requirements affecting patterns of tree canopy use. Tree crown volume of habitat available in a tree canopy is related to the amount of available resources, which often lack a pronounced vertical gradient in arthropod communities in temperate forest, in contrast to tropical forest [2]. The upper canopy of coniferous trees is a foraging site most preferred by dominant members of the mixed-species groups composed by small passerine birds because of better availability of food and increased safety there.

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