Correlation Analysis Procedures for Canopy Spectral Reflectance Data of Seashore Paspalum under Traffic Stress

Abstract

<jats:p>Traffic stresses often cause a decline in turfgrass quality. Analysis of spectral reflectance is valuable for assessing turfgrass canopy status. The objectives of this study were to determine correlations of narrow band canopy reflectance and selected reflectance indices with canopy temperature and turf quality for seashore paspalum exposed to wear and wear plus soil compaction traffic stresses, and to evaluate the effects of the first derivative of reflectance and degree of data smoothing (spectral manipulations) on such correlations. `Sea Isle 1' seashore paspalum (<jats:italic>Paspalum vaginatum</jats:italic> Swartz) was established on a simulated sports field during 1999 and used for this study. Compared to original reflectance, the first derivative of reflectance increased the correlation coefficient (<jats:italic>r</jats:italic>) of certain wavelengths with canopy temperature and turf quality under both traffic stresses. Among 217 wavelengths tested between 400 and 1100 nm, the peak correlations of the first derivative of reflectance occurred at 661 nm and 664 nm for both canopy temperature and turf quality under wear stress, respectively, while the highest correlations were found at 667 nm and 820 to 869 nm for both variables under wear plus soil compaction. Collectively, the first derivative of reflectance at 667 nm was the optimum position to determine correlation with canopy temperature (<jats:italic>r</jats:italic> &gt; 0.62) and turf quality (<jats:italic>r</jats:italic> &lt; -0.72) under both traffic stresses. All correlations were not sensitive to degrees of smoothing of reflectance from 400 to 1100 nm. A ratio of R936/R661 (IR/R, Infrared/red) and R693/759 (stress index) had the strongest correlations with canopy temperature for wear (<jats:italic>r</jats:italic> = -0.63) and wear plus soil compaction (<jats:italic>r</jats:italic> = 0.66), respectively; and a ratio of R693/R759 had the strongest correlation with turf quality for both wear (<jats:italic>r</jats:italic> = -0.89) and wear plus soil compaction (<jats:italic>r</jats:italic> = -0.82). The results suggested that the first derivative of reflectance could be used to estimate any single wavelength simultaneously correlated with multiple turf canopy variables such as turf quality and canopy temperature, and that the stress index (R693/R759) was also a good indicator of canopy stress status.</jats:p>

Evaluation of Remote Sensing to Measure Plant Stress in Creeping Bentgrass (Agrostis stolonifera L.) Fairways

“…Infrared reflectance is generally high because of cell structure in the leaf (Knipling, 1970; Woolley, 1971). Turfgrass research has examined the effect of irrigation (Fenstermaker‐Shaulis et al, 1997; Park et al, 2005; Baghzouz et al, 2006; Xiong et al, 2007; Dettman‐Kruse et al, 2008), nitrogen (Bell et al, 2002a; Baghzouz et al, 2006; Kruse et al, 2006; Xiong et al, 2007), mowing (Fitz‐Rodriguez and Choi, 2002), disease (Nutter et al, 1993; Green et al, 1998; Raikes and Burpee, 1998; Rinehart et al, 2002), wear (Trenholm et al, 1999; Jiang et al, 2003), traffic (Guertal and Shaw, 2004), cultivars, and species (Jiang and Carrow, 2005, 2007) on reflectance. Repeatedly these studies have found reflectance correlation with turf quality, increased visible reflectance with increasing turfgrass stress, and decreased to variable near‐infrared (NIR) reflectance with increasing turfgrass stress (Nilsson, 1995; Green et al, 1998; Guertal and Shaw, 2004).…”

Assessment of Narrow-band Canopy Spectral Reflectance and Turfgrass Performance under Drought Stress

“…Wavelength ( acteristic of canopy structure would be a factor influencing reflectance of seashore paspalum. Jiang et al (2003) found that reflectance from 756 to 804 nm were highly correlated with turf quality of seashore paspalum under wear stress. Trenholm at al.…”

“…These symptoms can be visually rated as a basis of turfgrass drought resistance, but accurate and rapid detection of early symptoms are often difficult and quantitative measurements would be preferred over visual rating. Remote sensing with broad-band spectral reflectance has been used for evaluation of turfgrass performance under drought stress (Fenstermaker-Shaulis et al, 1997;Jiang et al, 2004) and traffic stress (Jiang et al, 2003;Trenholm et al, 1999). This technology provides a rapid, non-destructive estimate of turf quality and could be a possible screening tool for identification of turfgrass stress tolerance.…”

Ultradwarf Bermudagrass Performance as Influenced by Cultivar Selection and Cultural Management Practice

“…The NDVI (Rouse et al, 1973) has been used in previous turfgrass research to document health status (Trenholm et al, 1999; Jiang et al, 2003, 2009; Jiang and Carrow, 2005; Kruse et al, 2006; Sönmez et al, 2008). In this study, NDVI was evaluated biweekly from June to November using a turf color meter (FieldScout Turf Color Meter 500 NDVI, Spectrum Technologies, Inc., Aurora, IL).…”