The Errors in Visual Estimation of Plants Cover in the Context of Education of Phytosociology

Chmura, Damian; Salachna, Anna

doi:10.1515/cdem-2016-0006

Cited by 6 publications

(8 citation statements)

References 17 publications

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“…The assumptions of the LAI-2000 are that the potato leaves are small for the observed field of view (148° FOV), are an optical black in the wavelength region below 490 nm (i.e., not transmitting or reflecting incident radiation), and are randomly oriented with respect to azimuth [ 61 ]. For fCover, visual assessment is widely used in plant communities, due to its simplicity and rapid measurement; however, it can be a potential source of error, due to its subjective dependency and the difficulty in measuring the variable accurately [ 96 ]. Furthermore, when calculating the LCC from SPAD measurements using Equation (1) , the transfer function should be calibrated to the particular crop of interest [ 97 ].…”

Section: Discussionmentioning

confidence: 99%

Comparison of Crop Trait Retrieval Strategies Using UAV-Based VNIR Hyperspectral Imaging

et al. 2021

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Hyperspectral cameras onboard unmanned aerial vehicles (UAVs) have recently emerged for monitoring crop traits at the sub-field scale. Different physical, statistical, and hybrid methods for crop trait retrieval have been developed. However, spectra collected from UAVs can be confounded by various issues, including illumination variation throughout the crop growing season, the effect of which on the retrieval performance is not well understood at present. In this study, four retrieval methods are compared, in terms of retrieving the leaf area index (LAI), fractional vegetation cover (fCover), and canopy chlorophyll content (CCC) of potato plants over an agricultural field for six dates during the growing season. We analyzed: (1) The standard look-up table method (LUTstd), (2) an improved (regularized) LUT method that involves variable correlation (LUTreg), (3) hybrid methods, and (4) random forest regression without (RF) and with (RFexp) the exposure time as an additional explanatory variable. The Soil–Leaf–Canopy (SLC) model was used in association with the LUT-based inversion and hybrid methods, while the statistical modelling methods (RF and RFexp) relied entirely on in situ data. The results revealed that RFexp was the best-performing method, yielding the highest accuracies, in terms of the normalized root mean square error (NRMSE), for LAI (5.36%), fCover (5.87%), and CCC (15.01%). RFexp was able to reduce the effects of illumination variability and cloud shadows. LUTreg outperformed the other two retrieval methods (hybrid methods and LUTstd), with an NRMSE of 9.18% for LAI, 10.46% for fCover, and 12.16% for CCC. Conversely, LUTreg led to lower accuracies than those derived from RF for LAI (5.51%) and for fCover (6.23%), but not for CCC (16.21%). Therefore, the machine learning approaches—in particular, RF—appear to be the most promising retrieval methods for application to UAV-based hyperspectral data.

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Section: Discussionmentioning

confidence: 99%

Comparison of Crop Trait Retrieval Strategies Using UAV-Based VNIR Hyperspectral Imaging

et al. 2021

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“…We averaged the percentage cover for all species in the four subplots to produce a single estimate for each sample unit. Although this approach can have some limitations due to subjectivity of the observer, there is evidence that, compared to other more objective techniques, visual evaluation can detect more plant species, including rare ones (Dethier et al, 1993;Chmura and Salachna, 2016). Besides, in this work, potential individual observer effects were likely minimal, as the field team was roughly the same during the entire evaluation period, thus making data comparable among plots.…”

Section: Field Datamentioning

confidence: 98%

Effect of Land Use History on Biodiversity of Pine Plantations

2021

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The growing replacement of native vegetation by forest plantations is considered a global threat to biodiversity. Significant variation in biotic communities among stands with similar management suggests that previous land use might have an effect on the capacity of forest plantations to harbor native species. The goal of our study was to determine the effect of land-use history on the biodiversity currently present in pine plantations in the coastal range of Central Chile. In particular, we hypothesized that plantations that directly replaced native forests should have higher diversity of plants and birds than plantations that were established in agricultural areas. We also expected that plantations of higher number of rotations should have fewer habitat-specialists and more generalists/exotics, reflecting a process of biotic homogenization. Using aerial photographs and satellite images encompassing a period of six decades, we classified 108 4-ha sampling units into native forests, and mature (17–20 year) pine plantations of first, second, and third rotation, of either forest or agricultural origin. At each site, we collected data on the abundance and richness of diurnal birds and understory plants, and analyzed their behavior in relation to the land-use history using Generalized Linear Models (GLMs). Also, we evaluated dissimilarity of communities of each pine plantation “treatment” to assess the occurrence of biotic homogenization. As predicted, pine plantations that directly replaced native forests had a higher abundance of forest specialists and less abundance of exotics and generalists than plantations of agricultural origin. In contrast, the number of rotations of pine plantations not only did not affect negatively the diversity and abundance of forest specialist species, but the models showed some signs of naturalization in the studied systems over time, such as the increase in the abundance of native herbs and a reduction in the abundance of their exotic counterparts. These results agree with the lack of evidence for a decrease in the dissimilarity of biotic communities in plantations with time, suggesting that the management of pine plantations in Central Chile is not promoting biotic homogenization, beyond the impact of the initial stages of land use change.

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“…On the contrary visual methods are faster and cheaper. BB scale is the most popular visual based data collection method and has frequently been employed by phytosociologist or vegetation ecologists (Chmura & Salachna, 2016). This method was initially developed in studies on the mountain ecosystems of Switzerland and on the Mediterranean ecosystems in France.…”

Section: Discussionmentioning

confidence: 99%

“…in the Case of Uncertainty Various integer or non-integer counts have been used or proposed for the code of BB scale (Poore, 1955;Westhoff & Van der Maarel, 1973;Campbell, 1974;Werger, 1974;Prieditis, 1997;Peet et al, 1998;Van der Maarel, 2007;Miller et al, 2014;Vahdati et al, 2014;Chmura & Salachna, 2016;Camiz et al, 2017). Numerical differences in description of code " " in the literature reveal that although certainly corresponds to " ", " " probably does not correspond to .…”

Section: Estimatingmentioning

confidence: 99%

“…In many basic and applied plant ecological studies, visual estimation methods have frequently been used. Amongst visual estimation methods Braun-Blanquet (BB) scale is the most popular method since it is faster, cheaper and easier to use when compared to the other botanical field survey methods (Chmura & Salachna, 2016). BB scale includes 7 degree (Table 1).…”

Section: Introductionmentioning

confidence: 99%

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Braun Blanquet Skalasından Doğru Tür Zenginliğinin Kestirimi

Özkan

2021

Kastamonu Üniversitesi Orman Fakültesi Dergisi

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Aim of study:The goal of the study was to estimate true species richness from Braun Blanquet (BB) scale data.Area of study: Yazılı Canyon Nature Park (YCNP) located in the Mediterranean Region of Turkey.Material and methods: A bias-corrected approach was adapted based on the Good-Turning frequency formula to estimate true species richness ( ) for 9 vegetation plots under three scenarios (Rare species are singletons: with 1/1 probability ( ), with 1/2 probability ( ), with 1/3 probability ( )).Main results: The results indicate that with increasing uncertainty about the number of singletons, the difference between expected species richness and observed species richness decreases. To estimate the species richness of the plots taken from YCNP, scenario III ( ) seems to be the best option due to existing maximum uncertainty concerning the number of singletons.Highlights: All the proposed bias-corrected estimators have been developed by considering the abundance or the incidence-based data except for . For employing , all the data consists of the number of singletons ( ) and super doubletons ( ). and can be obtained from BB scale because its code usually corresponds to . However, some scientists prefer to use in description of a few species. That causes an uncertainty about . Using , this study offers an approach and a spreadsheet program to estimate true species richness even though the number of singletons is uncertain.

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The Errors in Visual Estimation of Plants Cover in the Context of Education of Phytosociology

Cited by 6 publications

References 17 publications

Comparison of Crop Trait Retrieval Strategies Using UAV-Based VNIR Hyperspectral Imaging

Comparison of Crop Trait Retrieval Strategies Using UAV-Based VNIR Hyperspectral Imaging

Effect of Land Use History on Biodiversity of Pine Plantations

Braun Blanquet Skalasından Doğru Tür Zenginliğinin Kestirimi

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