Technical Note: Lightweight Camera Stand for Close-to-Earth Remote Sensing

Booth, D. Terrance; Cox, Samuel E.; Louhaichi, Mounier

doi:10.2458/azu_jrm_v57i6_booth

Cited by 5 publications

(9 citation statements)

References 4 publications

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“…Repeat photographs of each experimental plot were taken in the same location within each plot biweekly from end of March until end of October from 2007 to 2012 and March–July 2013 using a 2‐m tall camera stand with a 1‐m 2 ground frame (Booth et al . ). In 2008, we were only able to take photographs once per month.…”

Section: Methodsmentioning

confidence: 97%

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland

et al. 2015

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1. Vegetation greenness, detected using digital photography, is useful for monitoring phenology of plant growth, carbon uptake and water loss at the ecosystem level. Assessing ecosystem phenology by greenness is especially useful in spatially extensive, water-limited ecosystems such as the grasslands of the western United States, where productivity is moisture dependent and may become increasingly vulnerable to future climate change.2. We used repeat photography and a novel means of quantifying greenness in digital photographs to assess how the individual and combined effects of warming and elevated CO 2 impact ecosystem phenology (greenness and plant cover) in a semi-arid grassland over an 8-year period.3. Climate variability within and among years was the proximate driver of ecosystem phenology. Individual and combined effects of warming and elevated CO 2 were significant at times, but mediated by variation in both intra-and interannual precipitation. Specifically, warming generally enhanced plant cover and greenness early in the growing season but often had a negative effect during the middle of the summer, offsetting the early season positive effects. The individual effects of elevated CO 2 on plant cover and greenness were generally neutral. 4.Opposing seasonal variations in the effects of warming and less so elevated CO 2 cancelled each other out over an entire growing season, leading to no net effect of treatments on annual accumulation of greenness. The main effect of elevated CO 2 dampened quickly, but warming continued to affect plant cover and plot greenness throughout the experiment. The combination of warming and elevated CO 2 had a generally positive effect on greenness, especially early in the growing season and in later years of the experiment, enhanced annual greenness accumulation. However, interannual precipitation variation had larger effect on greenness, with two to three times greater greenness in wet years than in dry years. 5.Synthesis. Seasonal variation in timing and amount of precipitation governs grassland phenology, greenness and the potential for carbon uptake. Our results indicate that concurrent changes in precipitation regimes mediate vegetation responses to warming and elevated atmospheric CO 2 in semi-arid grasslands. Even small changes in vegetation phenology and greenness in response to warming and rising atmospheric CO 2 concentrations, such as those we report here, can have large consequences for the future of grasslands.

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Section: Methodsmentioning

confidence: 97%

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland

et al. 2015

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“…Plant cover (percent of ground cover occupied by plants) in each plot was determined by obtaining digital photography from about 2·5 m aboveground in a process similar to that of Booth et al . (). The images were printed and the areas occupied by vegetation and bare ground were manually separated and measured with a CID‐202 laser area meter (CID Bioscience, Camas, WA).…”

Section: Methodsmentioning

confidence: 97%

Growth, water productivity, and biomass allocation of Great Basin plants as affected by summer watering

Evans

Mata-González

Martin³

et al. 2012

Ecohydrology

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This study measured water‐use efficiency of wildland vegetation at the whole‐plant level during two contrasting years to better understand ecosystem responses to precipitation fluctuations in the Great Basin, USA. Biome‐representative species included grasses (Distichlis spicata, Leymus triticoides, and Sporobolus airoides), desert shrubs (Artemisia tridentata, Atriplex confertifolia, and Ericameria nauseosa), wetland/riparian plants (Glycyrrhiza lepidota, Juncus arcticus, and Salix exigua), and an exotic annual (Salsola tragus). Plants were grown in 5·8 m2 plots in a common garden in eastern California. Four watering treatments were applied monthly during two summers: control (no water other than natural precipitation), low (1·3 cm), medium (2·6 cm), and high (3·9 cm). Water‐use efficiency, here termed water to production (WTPa), was the ratio of water transpired to aboveground biomass produced. Biomass production was 50% lower and WTPa was five times higher during 2009 than 2010. WTPa decreased with watering during 2009 but increased with watering during 2010. Year differences determined vegetation productivity and response to summer watering and were related to the lower winter/spring precipitation during 2009 than 2010. Desert shrubs were more drought tolerant than grasses and wetland plants. Yet, an increase in summer precipitation would primarily benefit herbaceous species and not desert shrubs. Desert shrubs achieved greater standing crop but lower root‐to‐shoot ratio (RSR) than herbaceous species. Nonetheless, the grass S. airoides had the greatest standing crop overall, mainly because of its greater root production (RSR 5·5). Species differences in growth, WTPa, and biomass allocation should be considered in land management and conservation practices. Copyright © 2012 John Wiley & Sons, Ltd.

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“…The size of understorey vegetation also poses challenges for photographic cover measurement; the camera needs to be positioned high above the ground, and a large area needs to be photographically captured to represent the vegetation; hence, the use of frames or shading devices (e.g. Booth et al. 2004) is impractical.…”

Section: Introductionmentioning

confidence: 99%

Automated estimation of foliage cover in forest understorey from digital nadir images

Macfarlane

Ogden

2011

Methods Ecol Evol

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Summary1. Understorey vegetation can contribute significantly to the foliage cover and gas exchange of forest and impact the accuracy of remotely-sensed vegetation indices. Visual assessment is a rapid means of estimating cover, but its drawbacks include bias and inconsistency between observers and observation periods and the inability of observers to distinguish between cover intervals smaller than 10%. The accuracy of visual assessment is unlikely to be able to reliably detect changes smaller than 10%. Hence, there is a need for rapid and accurate alternatives for estimating understorey cover in forests. 2. Nadir (downward facing) photography is an alternative method that has been applied successfully in agriculture but not tested in forests. Detection of green foliage in images of forest understorey is far more challenging than in images of agricultural crops owing to the heterogeneity of the vegetation, the background and the lighting conditions. We tested several image analysis approaches to classifying and quantifying foliage cover in images taken from a height of 3-4 m above the ground using a digital SLR camera on an extendible pole. To reduce the impact of lighting variations on image processing, we converted red, green and blue (RGB) digital numbers from the RGB image to green leaf algorithm (GLA) values and to the CIE L*a*b* colour model prior to analysis. 3. The most successful classification method (LAB2) utilised the GLA, a* and b* values of each pixel to classify green vegetation using a minimum-distance-to-means classifier. A histogram-corner detection method (Rosin) was superior to other methods when cover was <10%. Between-class variance methods were the least accurate methods. Owing to the spectral complexity of the forest floor, it was necessary to filter noise from the classified images. Further work is needed to separate shades of gray from hues of green in images with sparse cover and coarse woody debris. 4. Synthesis and Applications. We propose that the LAB2 method be used to quantify foliage cover in nadir images of understorey with cover >10% but that the Rosin method be used for cover <10%. The automated methodology that we have developed yields estimates of foliage cover in forest understorey from digital photography that are rapid, objective and at least as accurate as visual assessment (i.e. within 5%). User intervention is limited to quality control. The improved method could be extended to indirect estimation of leaf area index for studies of forest water balance and productivity.

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Technical Note: Lightweight Camera Stand for Close-to-Earth Remote Sensing

Cited by 5 publications

References 4 publications

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland

Growth, water productivity, and biomass allocation of Great Basin plants as affected by summer watering

Automated estimation of foliage cover in forest understorey from digital nadir images

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Technical Note: Lightweight Camera Stand for Close-to-Earth Remote Sensing

Cited by 5 publications

References 4 publications

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO2 and warming in a semi‐arid grassland

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO2 and warming in a semi‐arid grassland

Growth, water productivity, and biomass allocation of Great Basin plants as affected by summer watering

Automated estimation of foliage cover in forest understorey from digital nadir images

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Product

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Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland

Seasonality of soil moisture mediates responses of ecosystem phenology to elevated CO₂ and warming in a semi‐arid grassland