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Presence–absence sampling for estimating plant density using survey data with variable plot size

Ståhl, Göran and Ekström, Magnus and Dahlgren, Jonas and Esseen, Per Anders and Grafström, Anton and Jonsson, Bengt-Gunnar (2020). Presence–absence sampling for estimating plant density using survey data with variable plot size. Methods in Ecology and Evolution. 11 , 580-590
[Research article]

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Abstract

* Presence–absence sampling is an important method for monitoring state and change of both individual plant species and communities. With this method, only the presence or absence of the target species is recorded on plots and thus the method is straightforward to apply and less prone to surveyor judgement compared to other vegetation monitoring methods. However, in the basic setting, all plots must be equally large or otherwise it is unclear how data should be analysed. In this study, we propose and evaluate five different methods for estimating plant density based on presence–absence registrations from surveys with variable plot sizes.
* Using artificial plant population data as well as empirical data from the Swedish National Forest Inventory, we evaluated the performance of the proposed methods. The main analysis was conducted through sampling simulation in artificial populations, whereby bias and variance of density estimators for the different methods were quantified and compared.
* Both for state and change estimation of plant density, we found that the best method to handle variable plot size was to perform generalized least squares regression, using plot size as an independent variable. Methods where plots smaller than a certain threshold were excluded or their registrations recalculated were, however, almost as good. Using all registrations as if they were obtained from plots with the nominal plot size resulted in substantial bias.
* Our findings are important for plant population studies in a wide range of environmental monitoring programmes. In these programmes, plots are typically randomly laid out and may be located across boundaries between different land‐use or land‐cover classes, resulting in subplots of variable size. Such splitting of plots is common when large plots are used, for example, with the 100 m2 plots used in the Swedish National Forest Inventory. Our methods overcome problems to estimate plant density from presence–absence data observed in plots that vary in size.

Authors/Creators:Ståhl, Göran and Ekström, Magnus and Dahlgren, Jonas and Esseen, Per Anders and Grafström, Anton and Jonsson, Bengt-Gunnar
Title:Presence–absence sampling for estimating plant density using survey data with variable plot size
Series Name/Journal:Methods in Ecology and Evolution
Year of publishing :2020
Volume:11
Page range:580-590
Number of Pages:11
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Accepted version
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
URN:NBN:urn:nbn:se:slu:epsilon-p-106546
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-106546
Additional ID:
Type of IDID
DOI10.1111/2041-210X.13348
ID Code:23244
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Resource Management
(NL, NJ) > Dept. of Forest Resource Management

(S) > Dept. of Wildlife, Fish and Environmental Studies
Deposited By: SLUpub Connector
Deposited On:12 Apr 2021 09:23
Metadata Last Modified:12 Apr 2021 09:31

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