Indirect Measurement of Leaf Area Index in Sagebrush-Steppe Rangelands

Abstract

Leaf area index (LAI) is defined as the one-sided area of leaves above a unit area of ground. It is a fundamental ecosystem parameter that is a required input of process-based plant growth and biogeochemical models. Direct measurement of LAI is the most accurate method, but is destructive, time-consuming, and labor-intensive. LAI is highly variable in time and space on sagebrush-steppe rangelands, and a rapid, nondestructive method is desirable to understand ecosystem processes. The pointintercept method is nondestructive and has been demonstrated to provide accurate LAI estimates, but the method is timeconsuming. LAI measurement with the Accupar ceptometer (Decagon Devices, Pullman, WA) is nondestructive and faster than the point-intercept method, but has not been evaluated on sagebrush-steppe rangelands. The objective of this study was to evaluate the ceptometer for measurement of LAI in sagebrush-steppe rangelands. Ceptometer and point-intercept LAI data were collected at six sites in sagebrush-steppe rangelands and the values were compared. We found that 1) ceptometer LAI data were consistently greater than point-intercept LAI data, 2) ceptometer data were much more variable than the point-intercept data based on standard deviations, and 3) the overall correlation between the two methods was very weak (r 2 5 0.15). The much greater ceptometer LAI values were, at least partly, due to the large woody component of the vegetative cover. We attribute the high variability of ceptometer-measured LAI to high instrument sensitivity of the angle of the instrument relative to the sun. Resumen El índice de área foliar (IAF) se define como el área de hoja verde (un solo lado) por unidad de área de suelo. Este es un parámetro fundamental en los ecosistemas que requiere un proceso basado en el crecimiento de la planta y modelos bio-geoquímicos. Mediciones directas de IAF es el método más preciso pero es destructivo, consume tiempo y mucho trabajo. IAF es muy variable en tiempo y espacio en los pastizales de matorrales de estepa, por lo que se requiere un método no destructivo para entender el proceso del ecosistema. El método del punto de intercepción es no destructivo y ha demostrado en proveer estimaciones de IAF precisas. El Accuper ceptometor (Decagon Devices, Pullman, WA) es un método no destructivo que es más rápido que el punto de intercepción pero no ha sido evaluado en pastizales de estepa con artemisa. El objetivo de este estudio fue evaluar el ceptometro para medir el IAF en pastizales de estepa con artemisa. Se recolectaron datos de IAF del ceptometro y del punto intercepto en seis sitios de pastizal de estepa de artemisa y los valores fueron comparados. Encontramos que 1) los datos de IAF del ceptometro fueron más consistentes que los del punto intercepto, 2) los datos del ceptometro fueron mucho más variables que los del punto intercepto y 3) la correlación general entre los dos métodos fue muy endeble (r 2 5 0.15). Los valores de IAF mayor con el ceptometro el menos en parte se debió a la gran composición de ...

Regulation of precipitation‐associated vegetation dynamics on catchment water balance in a semiarid and arid mountainous watershed

“…NS > 0·73, Table I) suggested that R-RHESSys can reasonably capture the variation of daily streamflow and baseflow for the Cleve Creek. The point-intercept-measured LAI for sagebrush-steppe ecosystems in the western USA averaged 0·33 m 2 m À2 (Finzel et al, 2012). Simulated annual mean LAI in the shrub-dominated watershed (Figure 1b) averaged 0·27 m 2 m À2 and ranged from 0·19 to 0·37 m 2 m À2 during 1991-2012, closing to reported data for similar ecosystems.…”

“…In addition, given that there is a lack of observed vegetation data, we compared the ranges of simulated leaf area index (LAI) and net primary productivity (NPP) of vegetation with previously published data for similar vegetation types (Gibbens et al, 1996;White et al, 2000;Tian et al, 2010;Finzel et al, 2012). These periods were selected because of the consistency of both weather records and observed daily streamflow data from the US Geological Survey gauge station.…”

“…These periods were selected because of the consistency of both weather records and observed daily streamflow data from the US Geological Survey gauge station. In addition, given that there is a lack of observed vegetation data, we compared the ranges of simulated leaf area index (LAI) and net primary productivity (NPP) of vegetation with previously published data for similar vegetation types (Gibbens et al, 1996;White et al, 2000;Tian et al, 2010;Finzel et al, 2012).…”

Leaf area index assessment for tomato and cucumber growing period under different water treatments

“…Using ceptometer, measurement of LAI is an easy, quick and non-destructive method which has been used to observe various agronomic (switch grass, sagebrush-steppe, rangelands, maize, giant reed etc.) physiology and vegetative growth (Finzel et al 2012, Francone et al 2014. Nevertheless, this instrument has not been used in horticultural crops such as tomato and cucumber.…”

A Novel Approach for Retrieving Tree Leaf Area from Ground-Based LiDAR

“…Therefore, "indirect" non-contact measurements have been developed and are typically preferred. These techniques include a multitude of non-contact leaf area index (LAI) measurement tools, such as hemispherical photography, the Hemi-view Plant Canopy Analyser [3] from Delta-T Devices, the LAI-2000 Plant Canopy Analyser [4] from LI-COR Biosciences, the LP-80 AccuPAR ceptometer [5] from Decagon Devices, a mobile sensor combined with the canopy light transmittance model [6], the prototype sun-fleck LAI instrument named Tracing Radiation and Architecture of Canopies TRAC [7] and a Moderate Resolution Imaging Spectra-radiometer [8]. In addition, light detection and ranging technology (LiDAR), which has been applied to airborne [9] and terrestrial instruments [10], has been used to assess canopy structure and estimate vegetation attributes [11].…”