Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy

Summary

Fast and precise leaf area index (LAI) estimation in terrestrial ecosystems is crucial for a wide range of ecological studies and calibrating remote sensing products. Presented here is the protocol for using the new LP 110 optical device for taking ground-based in situ LAI measurements.

Abstract

Leaf area index (LAI) is an essential canopy variable describing the amount of foliage in an ecosystem. The parameter serves as the interface between green components of plants and the atmosphere, and many physiological processes occur there, primarily photosynthetic uptake, respiration, and transpiration. LAI is also an input parameter for many models involving carbon, water, and the energy cycle. Moreover, ground-based in situ measurements serve as the calibration method for LAI obtained from remote sensing products. Therefore, straightforward indirect optical methods are necessary for making precise and rapid LAI estimates. The methodological approach, advantages, controversies, and future perspectives of the newly developed LP 110 optical device based on the relation between radiation transmitted through the vegetation canopy and canopy gaps were discussed in the protocol. Furthermore, the instrument was compared to the world standard LAI-2200 Plant Canopy Analyzer. The LP 110 enables more rapid and more straightforward processing of data acquired in the field, and it is more affordable than the Plant Canopy Analyzer. The new instrument is characterized by its ease of use for both above- and below-canopy readings due to its greater sensor sensitivity, in-built digital inclinometer, and automatic logging of readings at the correct position. Therefore, the hand-held LP 110 device is a suitable gadget for performing LAI estimation in forestry, ecology, horticulture, and agriculture based on the representative results. Moreover, the same device also enables the user to take accurate measurements of incident photosynthetically active radiation (PAR) intensity.

Introduction

Canopies are loci of numerous biological, physical, chemical, and ecological processes. Most of them are affected by canopy structures¹. Therefore, accurate, rapid, non-destructive, and reliable in situ vegetation canopy quantification is crucial for a wide range of studies involving hydrology, carbon and nutrient cycling, and global climate change^2,3. Since leaves or needles represent an active interface between the atmosphere and vegetation⁴, one of the critical canopy structural characteristics is leaf area index (LAI)⁵, d....

Protocol

NOTE: Before beginning to take planned field measurements, sufficiently charge the battery of the LP 110 device. Connect the instrument (USB connector, see Figure 1) and the computer through the attached cable. Battery status is shown in the left-upper corner of the device display.

1. Calibration before measurement

NOTE: For the LP 110, perform a dark calibration of the LAI sensor and in-built inclinometer calibrations before beginning each field measurement campaign.

1. LAI sensor's dark calibration
   1. Turn on the instrument by pressing and holding the ....

Results

The spatial structure obtained from both tested devices obviously differed in all studied plots, i.e., thinned from above (A), thinned from below (B) and a control without any silvicultural intervention (C; see Table 2 for more details). At the stand level, similar differences in LAI values obtained from the LP 110 and the Plant Canopy Analyzer were confirmed between thinned plots with various densities (A vs. B) using ANOVA and Tukey's test. For the Plant Canopy Analyzer, significantly higher LAI va.......

Discussion

What are the differences between the LP 110 as a newly presented device for estimating LAI (or taking PAR intensity measurements) and the LAI-2200 PCA as an improved version of the previous standard LAI-2000 PCA for estimating LAI via an indirect method? Beyond the price being about fourfold higher for the Plant Canopy Analyzer compared to the LP 110, the number of output parameters, measurement conditions, methodological approaches, and possibilities of estimating LAI for different canopies, accuracy of results, etc., c.......

Materials

Name	Company	Catalog Number	Comments
AccuPAR	METER Group, Inc., Pullman, WA, USA	AccuPaR LP-80	https://www.metergroup.com/environment/products/accupar-lp-80-leaf-area-index/
DEMON	CSIRO, Canberra, Australia	DEMON
File Viewer	LI-COR Biosciences Inc., NE, USA	FV2200C Software	https://www.licor.com/env/products/leaf_area/LAI-2200C/software.html
FluorPen	Photon System Instruments Ltd. (PSI), Czech Republic	FluorPen 1.1.2.3 Sofware	https://handheld.psi.cz/products/laipen/#download
Hand-held GPS device	Garmin Ltd., Czech Republic	Garmin eTrex 32x Europe46	https://www.garmin.cz/garmin-etrex-32x-europe46/80117
Hand-held device for leaf area index estimation(LP 110)	Photon System Instruments Ltd. (PSI) Czech Republic	LaiPen LP 110	https://handheld.psi.cz/products/laipen/#info
Plant Canopy Analyser	LI-COR Biosciences Inc., NE, USA	LAI-2000 PCA	LAI-2200 PCA or LAI-2200C as improved versions of LAI-2000 PCA can be used, see: https://www.licor.com/env/products/leaf_area/LAI-2200C/
Statistical software	Systat Software Inc., CA, USA	SigmaPlot 13.0	https://systatsoftware.com/products/sigmaplot/sigmaplot-version-13/?gclid=Cj0KCQjwzYGGBhCTARIs AHdMTQzgfb42vv0mWmcbVcflNO UvrLl802Lrhkfh23Qie2mIZfw4O8kp 7p0aAsoiEALw_wcB
Statistical software	StatSoft Inc., OK, USA	STATISTICA 10.0	For LAI visualization, wafer-plots in STATISTICA 10.0 were employed.
SunScan	Delta-T Devices, Ltd., Cambridge, UK	SS1 SunScan	https://www.delta-t.co.uk/product/sunscan
TRAC	3rd Wave Engineering, Ontarion Canada	Tracing Radiation and Architecture of Canopies	http://faculty.geog.utoronto.ca/Chen/Chen's%20homepage/res_trac.htm
Tripod	Any	NA	Tripod with standard nut
Water level	Any	NA