DOI: 10.5061/dryad.cfxpnvx9w
title: Data from: Community-level canopy reflectance in grazed grasslands is linked to the habitat preferences of individual plant species

description: Spectral remote sensing provides tools for biological monitoring and can
 be used to characterize habitat quality in grasslands. These data have
 been used to study the relationships between plant community composition
 and remotely sensed canopy reflectance in grazed grasslands. The study
 area is located on the island of Öland, Sweden, and the data were
 collected in grazed grasslands that represent a succession from previously
 arable fields to old semi-natural pastures. All included grassland sites
 have been assigned to three different classes of grassland age, defined by
 the grazing continuity in years: young (5–14 years), intermediate-aged
 (15–49 years), and old (&gt;50 years). The plant community data
 consist of presences/absences for 100 vascular plant species in 104 (4 m ×
 4 m) sample plots positioned in open grassland vegetation. Information on
 species’ habitat preferences is included and has been used to explain the
 associations between plant species’ occurrences and the variation in
 community-level canopy reflectance. The remote sensing data consist of 317
 hyperspectral bands in the wavelength regions 414–1322 nm, 1496–1797 nm,
 and 2050–2351 nm, and show the mean reflectance in each spectral band for
 the 104 sample plots. The main gradient in the hyperspectral data is
 characterized by contrasting reflectance values between bands located in
 the NIR spectra and bands located in the red, blue, and SWIR spectra.
 Grassland canopy reflectance was able to explain variation in the
 occurrences of individual plant species, particularly those with distinct
 habitat preferences. Species' habitat preferences indicated that
 vegetation reflectance in the red, blue, SWIR, and NIR spectra was linked
 to the plant-availability of mineral nitrogen. In contrast, species’
 phosphorus preferences showed stronger associations with reflectance in
 the green and red-edge spectra.
description: The study area (centred on
 56°40'49.0"N 16°33'58.0"E) measures approximately 5 km ×
 5 km and represents an agricultural
 mosaic landscape near the village of Algutsrum on the Baltic island of
 Öland, Sweden. The overall topography is flat, and the soils are neutral
 to basic (mean soil pH=7.0). The studied grassland sites were grazed by
 cattle and represent a succession from previously arable land to old
 semi-natural grassland. The ages of the grasslands have been determined
 with the help of historical map data (see Johansson et al., 2008), and the
 included sites are assigned to three categories of grassland age (defined
 by the number of years since the first historical map where the site was
 classified as grassland): young (5–14 years), intermediate-aged (15–49
 years), and old (&gt;50 years). Data are
 presented for 104 (4 m × 4 m) sampling plots that were positioned in open and
 relatively homogeneous grassland vegetation. Each plot belongs to a pair
 of plots in a total of 52 grassland sites (17 young, 18
 intermediate-aged, and 17 old). Grassland site selection and the positioning of
 sampling plots were carried out to minimize edge effects and shadows –
 detailed descriptions of the procedure are given in Möckel et al. (2014).
 Data on the grassland canopy reflectance were
 acquired on 9 July 2011 by two airborne hyperspectral sensors
 (Norsk Elektro Optikk AS (NEO), Lörenskog, Norway). The flight height was 1500 m and the spatial
 resolution in the raw data was 0.5–1.0 m. The spectral data
 consist of 317 narrowbands: 160 bands from the first sensor
 (3.6 nm bandwidth; 414–991 nm), and 156 bands from the second sensor (6.0
 nm bandwidth; 991–1322 nm, 1496–1797 nm, and 2050–2351 nm). The spectral data were pre-processed following
 the descriptions given in the section “2.4.1 Remote Sensing Data” in
 Möckel et al. (2014), and included corrections of atmospheric disturbance
 and topographic illumination effects, random noise reduction, and
 conversion of digital values to spectral reflectance. For each sampling
 plot, mean reflectance for each spectral band was extracted using a
 4 m × 4 m pixel window. Vegetation data were collected between
 15 May and 15 July 2011. The data represent the
 presence/absence of 100 vascular plant species in the 104 sampling plots.
 Information on species’ habitat preferences was extracted from a previous
 study (Löfgren et al., 2020), and was used to explain species’
 relationships with grassland canopy reflectance. The earlier study
 analysed species’ relationships with variation in soil concentrations of
 phosphorus, ammonium, and nitrate, and also used latent variable modelling
 to capture spatially dependent patterns in species occurrences at four
 fine-to-coarse spatial scales (S1, S2, S3, and S4). The species’ habitat
 preference values (Phosphorus, Ammonium, Nitrate, S1, S2, S3, and S4)
 consist of the species’ mean model-response parameters from the analysis
 in Löfgren et al. (2020). <strong>References</strong> Johansson, L.J., Hall, K., Prentice, H.C., Ihse, M., Reitalu, T., Sykes, M.T., & Kindström, M. (2008). Semi-natural grassland continuity, long-term land-use change and plant species richness in an agricultural landscape on Öland, Sweden. <em>Landscape and Urban Planning, 84</em>(3-4), 200–211. https://doi.org/10.1016/j.landurbplan.2007.08.001 Löfgren, O., Hall, K., Schmid, B.C., & Prentice, H.C. (2020). Grasslands ancient and modern: soil nutrients, habitat age and their relation to Ellenberg N. <em>Journal of Vegetation Science, 31</em>(3), 367-379. https://doi.org/10.1111/jvs.12856 Möckel (Astor), T., Dalmayne, J., Prentice, H.C., Eklundh, L., Purschke, O., Schmidtlein, S., & Hall, K. (2014). Classification of grassland successional stages using airborne hyperspectral imagery. <em>Remote Sensing, 6</em>(8), 7732-7761. https://doi.org/10.3390/rs6087732