Fast determination of light availability and leaf area index in tropical forests

An important property of plant communities is the Leaf Area Index (LAI), which is the vertically integrated surface of leaves per unit of ground area. Leaves are the primary sites of photosynthesis and transpiration, thus the LAI, which conditions the light interception by the canopy, is directly related to carbon and water exchange with the atmosphere at the stand scale (McNaughton & Jarvis 1983). LAI also has an impact on tree growth through the interception of light. Light availability below canopies is the principal limiting factor of tree recruitment and growth in forests (Denslow et al. 1990). Several methodologies have been used for measuring LAI in the field. These can be classiffed in four categories (Marshall & Waring 1986): (1) direct measurements by litterfall collection or destructive sampling, (2) allometric correlations with variables such as tree height or tree diameter, (3) gap-fraction assessment (e.g. with hemispherical photographs), (4) measurement of light transmittance with optical sensors.

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DIEBACK, LEAF AREA INDEX AND YIELD OF YOUNG EUCALYPT CLONES PLANTATION IN THE BRAZILIAN SAVANNAH REGION

Revista Árvore ◽

10.1590/1806-90882017000300009 ◽

2018 ◽

Vol 41 (3) ◽

Author(s):

Geraldo Gonçalves dos Reis ◽

Frederico de Freitas Alves ◽

Maria das Graças Ferreira Reis ◽

Felippe Coelho de Souza ◽

Diogo Sena Baiero ◽

...

Keyword(s):

Leaf Area Index ◽

Soil Water ◽

Leaf Area ◽

Water Deficit ◽

Tree Height ◽

Low Fertility ◽

Limiting Factor ◽

Soil Water Deficit ◽

Area Index ◽

Brazilian Savannah

ABSTRACT Eucalypt has been widely planted in Brazil, in the savannah region, which is characterized by high soil water deficit and low fertility. Dieback, leaf area index (LAI) and yield of young stands of 16 eucalypt clones were studied in Vazante, MG, Brazil (17º36’09"S and 46º 42’02"W). It was determined for each clone: a) the proportion of the tree height with dieback symptoms in the apical terminal (HWD%) and the proportion of trees with dieback (NWD%), at 13 months (end of the first dry season); b) the LAI at 13 and 21 months, and c) the yield at the age of 13, 19 and 25 months. HWD% reached 5-9%, and NWD%, 50-80%, for the five most susceptible clones, when the soil water deficit reached 508 mm in the year. LAI varied from 0.61 to 1.56, at 13 months, and from 2.31 to 3.48 at 21 months, presenting inverse relationship with dieback. The least susceptible clones to dieback achieved the highest yield up to 25 months of age. There was interaction between dieback and fertilizer levels only for three clones. There was a positive correlation (p < 0.001) between the LAI at the age of 13 months and the periodic monthly increment from 0 to 11 months, and from 11 to 19 months. The difference in dieback susceptibility among clones allows the selection of genotypes for regions where the soil water deficit is a major limiting factor.

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Potential and Limits of Retrieving Conifer Leaf Area Index Using Smartphone Camera Sensors

10.20944/preprints201701.0077.v1 ◽

2017 ◽

Author(s):

Yonghua Qu ◽

Jian Wang ◽

Jinling Song ◽

Jindi Wang

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Zenith Angle ◽

Tree Height ◽

Measuring Instruments ◽

Conifer Forest ◽

Area Index ◽

Gap Fraction ◽

Smartphone Sensors ◽

Camera Sensors

Plant leaf area index (LAI) is a key characteristic affecting field canopy microclimate. In addition to traditional professional measuring instruments, smartphone camera sensors have been used to measure plant LAI. However, when smartphone methods were used to measure conifer forest LAI, very different performances were obtained depending on whether the smartphone was held at the zenith angle or at a 57.5° angle. To validate further the potential of smartphone sensors for measuring conifer LAI and to find the limits of this method, this paper reports the results of a comparison of two smartphone methods with an LAI-2000 instrument. It is shown that both methods can be used to reveal the conifer leaf-growing trajectory. However, the method with the phone oriented vertically upwards always produced better consistency in magnitude with LAI-2000. The bias of the LAI between the smartphone method and the LAI-2000 instrument was explained with regard to four aspects that can affect LAI: gap fraction, leaf projection ratio, sensor field of view (FOV), and viewing zenith angle (VZA). It was concluded that large FOV and large VZA cause the 57.5° method to overestimate the gap fraction and hence underestimate conifer LAI, especially when tree height is greater than 2.0 m. For the vertically upward method, the bias caused by the overestimated gap fraction is compensated for by an underestimated leaf projection ratio.

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A new method to estimate clumping index integrating gap fraction averaging with the analysis of gap size distribution

Canadian Journal of Forest Research ◽

10.1139/cjfr-2018-0213 ◽

2019 ◽

Vol 49 (5) ◽

pp. 471-479 ◽

Cited By ~ 5

Author(s):

Francesco Chianucci ◽

Jie Zou ◽

Peng Leng ◽

Yinguo Zhuang ◽

Carlotta Ferrara

Keyword(s):

Leaf Area Index ◽

Size Distribution ◽

Leaf Area ◽

New Method ◽

Gap Size ◽

Area Index ◽

Canopy Density ◽

Gap Fraction ◽

Direct Measurements ◽

Clumping Index

Estimates of clumping index (Ω) are required to improve the indirect estimation of leaf area index (L) from optical field-based instruments such as digital hemispherical photography (DHP). A widely used method allows estimation of Ω from DHP using simple gap fraction averaging formulas (LX). This method is simple and effective but has the disadvantage of being sensitive to the spatial scale (i.e., the azimuth segment size in DHP) used for averaging and canopy density. In this study, we propose a new method to estimate Ω (LXG) based on ordered weighted gap fraction averaging (OWA) formulas, which addresses the disadvantages of LX and also accounts for gap size distribution. The new method was tested in 11 broadleaved forest stands in Italy; Ω estimated from LXG was compared with other commonly used clumping correction methods (LX, CC, and CLX). Results showed that LXG yielded more accurate Ω estimates, which were also more correlated with the values obtained from the gap size distribution methods (CC and CLX) than Ω obtained from LX. Leaf area index estimates, adjusted by LXG, are only 5%–6% lower than direct measurements obtained from litter traps, while other commonly used clumping correction methods yielded more underestimation.

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Measuring Canopy Geometric Structure Using Optical Sensors Mounted on Terrestrial Vehicles: A Case Study in Vineyards

Agriculture ◽

10.3390/agriculture11030208 ◽

2021 ◽

Vol 11 (3) ◽

pp. 208

Author(s):

Daniel Queirós da Silva ◽

André Silva Aguiar ◽

Filipe Neves dos Santos ◽

Armando Jorge Sousa ◽

Danilo Rabino ◽

...

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Optical Sensors ◽

Precision Agriculture ◽

Real Data ◽

Relevant Information ◽

Normal Operation ◽

Area Index ◽

Sensory Data ◽

The Right

Smart and precision agriculture concepts require that the farmer measures all relevant variables in a continuous way and processes this information in order to build better prescription maps and to predict crop yield. These maps feed machinery with variable rate technology to apply the correct amount of products in the right time and place, to improve farm profitability. One of the most relevant information to estimate the farm yield is the Leaf Area Index. Traditionally, this index can be obtained from manual measurements or from aerial imagery: the former is time consuming and the latter requires the use of drones or aerial services. This work presents an optical sensing-based hardware module that can be attached to existing autonomous or guided terrestrial vehicles. During the normal operation, the module collects periodic geo-referenced monocular images and laser data. With that data a suggested processing pipeline, based on open-source software and composed by Structure from Motion, Multi-View Stereo and point cloud registration stages, can extract Leaf Area Index and other crop-related features. Additionally, in this work, a benchmark of software tools is made. The hardware module and pipeline were validated considering real data acquired in two vineyards—Portugal and Italy. A dataset with sensory data collected by the module was made publicly available. Results demonstrated that: the system provides reliable and precise data on the surrounding environment and the pipeline is capable of computing volume and occupancy area from the acquired data.

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Extracting Leaf Area Index Using Viewing Geometry Effects - A New Perspective on High-Resolution Unmanned Aerial System Photography.

10.31220/osf.io/jcxa9 ◽

2020 ◽

Author(s):

Lukas Roth ◽

Helge Aasen ◽

Achim Walter ◽

Frank Liebisch

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Plant Ecology ◽

Growth And Yield ◽

Unmanned Aerial System ◽

Area Index ◽

Handheld Device ◽

Gap Fraction ◽

Rgb Images ◽

New Perspective

Abstract Extraction of leaf area index (LAI) is an important prerequisite in numerous studies related to plant ecology, physiology and breeding. LAI is indicative for the performance of a plant canopy and of its potential for growth and yield. In this study, a novel method to estimate LAI based on RGB images taken by an unmanned aerial system (UAS) is introduced. Soybean was taken as the model crop of investigation. The method integrates viewing geometry information in an approach related to gap fraction theory. A 3-D simulation of virtual canopies helped developing and verifying the underlying model. In addition, the method includes techniques to extract plot based data from individual oblique images using image projection, as well as image segmentation applying an active learning approach. Data from a soybean field experiment were used to validate the method. The thereby measured LAI 14 prediction accuracy was comparable with the one of a gap fraction-based handheld device (R2 of 0.92, RMSE of 0.42 m2 m2) and correlated well with destructive LAI measurements (R2 of 0.89, RMSE of 0.41 m2 m2). These results indicate that, if respecting the range (LAI ≤3) the method was tested for, extracting LAI from UAS derived RGB images using viewing geometry information represents a valid alternative to destructive and optical handheld device LAI measurements in soybean. Thereby, we open the door for automated, high-throughput assessment of LAI in plant and crop science.

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Use of airborne lidar for estimating canopy gap fraction and leaf area index of tropical montane forests

International Journal of Remote Sensing ◽

10.1080/01431161.2015.1041177 ◽

2015 ◽

Vol 36 (10) ◽

pp. 2569-2583 ◽

Cited By ~ 27

Author(s):

Janne Heiskanen ◽

Lauri Korhonen ◽

Jesse Hietanen ◽

Petri K.E. Pellikka

Keyword(s):

Leaf Area Index ◽

Leaf Area ◽

Canopy Gap ◽

Airborne Lidar ◽

Montane Forests ◽

Area Index ◽

Tropical Montane Forests ◽

Gap Fraction

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The effect of light availability on leaf area index, biomass production and plant species composition of park grasslands in Warsaw

Plant Soil and Environment ◽

10.17221/140/2013-pse ◽

2013 ◽

Vol 59 (No. 12) ◽

pp. 543-548 ◽

Cited By ~ 9

Author(s):

P. Dąbrowski ◽

B. Pawluśkiewicz ◽

Kalaji HM ◽

Baczewska AH

Keyword(s):

Solar Radiation ◽

Leaf Area Index ◽

Leaf Area ◽

Light Availability ◽

Vegetation Coverage ◽

Light Conditions ◽

Area Index ◽

Sward Height ◽

Poa Trivialis ◽

Leaf Density

How light conditions affect development of park grasslands is a question that has not been satisfactory addressed. The aim of this study was therefore determination of the level to which unfavorable light conditions influence grassy parks area and relationships between parameters which determine state of turf grasses. Researches were conducted in two parks in Warsaw, in various light conditions and included measurement of: leaf density, sward height, leaf area index (LAI), and botanical composition of the communities. The leaf density of shaded areas did not exceed 70%. LAI value varied from 0.5 to 0.9-fold lower than in the areas in half-shade and in sun. The participation of basic lawn species at Skaryszewski Park was higher under shade, while at Łazienki Królewskie was higher in full-sunlight areas. The state of tested grassy areas in limited solar radiation does not satisfy the requirements of recreational and representational functions. The development processes of vegetation coverage were inhibited at the sites of lower solar radiation. LAI was influenced by both leaf coverage and sward height. Agrostis stolonifera and Poa trivialis may be recommended to create grass areas under limited solar radiation.

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