Correcting non-linearity and slope effects in the estimation of the leaf area index of forests from hemispherical photographs

Schleppi, Patrick; Conedera, Marco; Sedivy, Isabella; Thimonier, Anne

doi:10.1016/j.agrformet.2007.02.004

Cited by 179 publications

(138 citation statements)

References 12 publications

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“…An example would be the scaffolding approach, which would be more complicated on a steep terrain but is not generally impossible. For indirect methods, often, mathematical solutions exist to correct for topographic effects in the data, such as those presented by Schleppi et al (2007) for hemispherical photographs. The decision if a method is used for a study is to a certain extent dependent on the topography as one factor characterizing the study site, but there are others more that have to be taken into account, such as infrastructure (road access, electricity) or available time.…”

Section: Comparison Of Techniques and Discussionmentioning

confidence: 99%

Review of ground-based methods to measure the distribution of biomass in forest canopies

Seidel

Fleck

Leuschner

et al. 2011

Annals of Forest Science

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& Context Ecological research and an effective forest management need accurate information on the structure of the forest canopy to understand the biochemical, physiological and biogeochemical processes within a forest. & Research question This paper reviews the currently available instruments for measuring the distribution of biomass within forest canopies. We compare the most well-established approaches and present the different measurable parameters. A special focus lies on the resolution of the obtained data. & Results It was found that only 3D laser scanners offer data with the resolution required by ecologists, private landholders, the forest industry and the public to detect trends in tree growth patterns and canopy interactions in all three spatial dimensions. But data validation, data analysis and parameter extraction are still under development, and the price of the instrument is quite high. & Conclusion Research should focus on the parameter extraction from terrestrial laser scanner data as this could allow the calculation of functional attributes for different sections of a canopy on a high spatial resolution. It could also help ecologists characterize the structure of forest stands in a quick and precise way.

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Section: Comparison Of Techniques and Discussionmentioning

confidence: 99%

Review of ground-based methods to measure the distribution of biomass in forest canopies

Seidel

Fleck

Leuschner

et al. 2011

Annals of Forest Science

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“…1.5.3 (Schleppi et al 2007). According to Nobis & Hunziker (2005), automatic thresholding was used for image analysis, while for the LAI estimation the Lang's method was preferred (Lang 1987).…”

Section: Canopy Leaf Areamentioning

confidence: 99%

“…According to Nobis & Hunziker (2005), automatic thresholding was used for image analysis, while for the LAI estimation the Lang's method was preferred (Lang 1987). Parts of the trees other than their leaves, such as stems and branches, can influence the values of LAI; thus, the corrections recommended by Schleppi et al (2007) for non-linearity and slope and by Chen & Cihlar (1995) for clumping effect were integrated into the calculations.…”

Section: Canopy Leaf Areamentioning

confidence: 99%

“…Hemispherical photography is a common technique used to determine the percentage of light transmission through canopy gaps (Dignan & Bren 2003, Schleppi et al 2007. Three hemispherical photographs were taken at each experimental site using a Sigma 8 mm fisheye lens mounted on a Canon EOS 5D digital SLR camera.…”

Section: Canopy Leaf Areamentioning

confidence: 99%

“…Interception or transmission of light is also related to LAI (Spanner et al 1994). In addition, LAI is a major structural characteristic of the forest ecosystem as it affects several significant ecological processes, including evapotranspiration, photosynthesis, rainfall, interception, surface albedo, and dry deposition (Maass et al 1995, Schleppi et al 2007). According to Perry et al (2008), LAI firmly combines with litterfall, microclimate and productivity, thus directly and indirectly affecting the forest floor and soil properties.…”

Section: Introductionmentioning

confidence: 99%

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Effects of altitudinal gradients on leaf area index, soil microbial biomass C and microbial activity in a temperate mixed forest ecosystem of Northwestern Turkey

Bolat¹,

Öztürk²

2017

iForest

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A high leaf area index (LAI) can provide indications of high fertility, such as optimal health and productivity in forest ecosystem. Yet, studying the microbial biomass and inherent activity in any forest ecosystem may enable better understanding of the role of microorganisms in soil quality and nutrient cycling. This study was carried out in the western Black Sea region of Turkey with the aim to determine the influence of elevation on LAI, microbial biomass and activity in a mixed forest ecosystem. Marked differences in the LAI, light transmission, soil temperature, Corg/Ntotal ratio, and microbial properties were found at sites sampled at different elevations along an altitudinal gradient (i.e., 1200, 1300 and 1400 m a.s.l.). The LAI was statistically (P < 0.05) higher at 1300 ( ) elevations compared to 1200 m (2.84 m 2 m -2 ) elevation, whereas the light transmission was statistically (P < 0.05) lower at 1300 and 1400 m elevations than that at 1200 m elevation. The amount of microbial biomass C at 1300 m (892.26 µg g -1 ) and 1400 m (725.99 µg g -1 ) elevations was significantly (P < 0.05) higher than that at 1200 m (650.84 µg g -1 ) elevation. Basal respiration did not vary significantly (P > 0.05) along the altitudinal gradient. An increase in respiration per unit biomass (i.e., increasing the metabolic quotient -qCO2) was also found in the sampling sites at 1200 m a.s.l. There was a positive relationship between the microbial biomass C and LAI (r = 0.612, P < 0.01) and negative relationship between the qCO2 and LAI (r = -0.592, P < 0.01). Our results showed that the elevation gradient has a significant influence on the LAI, microbial biomass C and microbial activity in the forest stand type analyzed. A subdivision of the forest stand types into different sub-types according to their productivity and development is advisable and recommended for forest management and administration purposes.

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Improved snow interception modeling using canopy parameters derived from airborne LiDAR data

Moeser

Stähli

Jonas³

2015

Water Resources Research

118

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Forest snow interception can account for large snow storage differences between open and forested areas. The effect of interception can also lead to significant variations in sublimation, with estimates varying from 5 to 60% of total snowfall. Most current interception models utilize canopy closure and LAI to partition interception from snowfall and calculate interception efficiency as an exponential decrease of interception efficiency with increasing precipitation. However, as demonstrated, these models can show specific deficiencies within heterogeneous canopy. Seven field areas were equipped with 1932 surveyed points within various canopy density regimes in three elevation bands surrounding Davos, Switzerland. Snow interception measurements were taken from 2012 to 2014 ($9000 samples) and compared with measurements at two open sites. The measured data indicated the presence of snow bridging from a demonstrated increase in interception efficiency as precipitation increased until a maximum was reached. As precipitation increased beyond this maximum, the data then exhibited a decrease in interception efficiency. Standard and novel canopy parameters were developed using aerial LiDAR data. These included estimates of LAI, canopy closure, distance to canopy, gap fraction, and various tree size parameters. These canopy metrics and the underlying efficiency distribution were then integrated to formulate a conceptual model based upon the snow interception measurements. This model gave a $27% increase in the r 2 (from 0.39 to 0.66) and a $40% reduction in RMSE (from 5.19 to 3.39) for both calibration and validation data sets when compared to previous models at the point scale. When upscaled to larger grid sizes, the model demonstrated further increases in performance.

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Correcting non-linearity and slope effects in the estimation of the leaf area index of forests from hemispherical photographs

Cited by 179 publications

References 12 publications

Review of ground-based methods to measure the distribution of biomass in forest canopies

Review of ground-based methods to measure the distribution of biomass in forest canopies

Effects of altitudinal gradients on leaf area index, soil microbial biomass C and microbial activity in a temperate mixed forest ecosystem of Northwestern Turkey

Improved snow interception modeling using canopy parameters derived from airborne LiDAR data

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