A Spatial Relationship between Canopy and Understory Leaf Area Index in an Old-Growth Cool-Temperate Deciduous Forest

Mitsuru Hirota,Yihan Cai,Yosuke Tanioka,Hideyuki Ida

doi:10.3390/f11101037

Mitsuru Hirota, Yihan Cai + Show 2 more

Open Access

https://doi.org/10.3390/f11101037

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Journal: Forests	Publication Date: Sep 25, 2020
Citations: 8	License type: CC BY 4.0

Affiliation: University of Tsukuba, Shinshu University, Ōtani University

Abstract

Quantification of leaf area index (LAI) is essential for understanding forest productivity and the atmosphere–vegetation interface, where the majority of gas and energy exchange occurs. LAI is one of the most difficult plant variables to adequately quantify, owing to large spatial and temporal variability, and few studies have examined the horizontal and vertical distribution of LAI in forest ecosystems. In this study, we demonstrated the LAI distribution in each layer from the understory to canopy using multiple-point measurements (121 points) and examined the relationships among layers in a cool-temperate deciduous forest. LAI at each point, and the spatial distribution of LAI in each layer, varied within the forest. The spatial distribution of LAI in the upper layer was more heterogeneous than that of LAI at the scale of the entire forest. Significant negative correlations were observed between the upper- and lower-layer LAI. Our results indicate that the understory compensates for gaps in LAI in the upper layer; thus, the LAI of the entire forest tends to remain spatially homogeneous even in a mature forest ecosystem.

Highlights

To evaluate the productivity of terrestrial ecosystems, it is important to quantify the amount of leaf area and its spatial distribution, as leaves are the only plant organ that can produce organic matter through photosynthesis in most ecosystems
This study focuses on the hierarchical structure of leaf area index (LAI) and attempts to partition the LAI by evaluating each three layers of LAI
No significant differences were observed between LAI2.5 and LAI5 in 2019 (p = 0.21)

Summary

Introduction

To evaluate the productivity of terrestrial ecosystems, it is important to quantify the amount of leaf area and its spatial distribution, as leaves are the only plant organ that can produce organic matter through photosynthesis in most ecosystems. Previous studies have reported positive correlations between LAI and several variables, such as net primary production, light absorption, microclimate, and water interception [1,2]. Research such as the long-term monitoring of LAI and remote sensing with satellites has been conducted in various ecosystems, and the observed LAI data have been applied to the estimation of productivity [1,2,3,4,5,6]. The amount of leaf will vary among points even in the same ecosystem depending on the structural heterogeneity at each location. Forest heterogeneity can involve factors such as gap formation caused by the death of tall trees via wind or fungal or insect infestations [8,9]

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Conclusion