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Changes in community-weighted trait mean, functional diversity, soil chemical properties and temperature along an elevational gradient in Tenerife, Canary Islands

Citation

Ratier Backes, Amanda; Frey, Larissa; Arévalo, José Ramón; Haider, Sylvia (2021), Changes in community-weighted trait mean, functional diversity, soil chemical properties and temperature along an elevational gradient in Tenerife, Canary Islands, Dryad, Dataset, https://doi.org/10.5061/dryad.66t1g1k37

Abstract

This dataset comprises community-weighted trait means and functional diversity of leaf traits, chemical soil properties and temperature recorded in roadside (disturbed) and interior (less disturbed) plots, along an elevational gradient of 2,300 m in Tenerife, Canary Islands. The leaf traits measured were specific leaf area (SLA), nitrogen, nitrogen to phosphorus ratio, leaf dry matter content (LDMC) and carbon to phosphorus ratio. The soil chemical properties measured were pH, nitrogen, nitrogen to phosphorus ratio, carbon to phosphorus ratio, calcium, potassium, magnesium and cation exchange capacity. Also the scores of the three first axes derived from a PCA analysis including the soil chemical properties are included. The temperature variables consist of bioclimatic variables Bio10 (mean temperature of the warmest quarter) and Bio11 (mean temperature of the coldest quarter). This dataset has been used for the analysis presented in Ratier Backes et al. (2021).

Methods

Data collection took place in April and May 2018. All data and samples were retrieved from permanent plots established in 2008, following the design of the standardized mountain road survey of the Mountain Invasion Research Network (MIREN). Three roads on the island’s southern slopes were selected, spanning from the coast to the crater of Mt. Teide. On each road, twenty sampling locations were distributed evenly over the ascent of approximately 2,300 m. At each sampling location, two plots with 2 m x 50 m each were established, one directly adjacent and with the long side parallel to the road, and a second one perpendicular to the roadside plot, at 50-100 m away from the road. Steep topography and private property prevented sampling in some locations, resulting in a total of 111 plots.

Temperature data

Near-surface soil temperature was measured using miniature loggers (HOBO 64K Pendant, with 0.53 °C accuracy, Bourne, MA, USA). They were installed in the center of the roadside plot and 50 m away from it, at the start of the distant plot, at a depth of 3 cm below the soil surface. They were programmed to log at 1.5 h intervals from May 2018 until April 2019. After data quality control, the bioclimatic variables Bio10 (mean temperature of the warmest quarter) and Bio11 (mean temperature of the coldest quarter) were calculated following the definitions of WorldClim.

Soil sampling and soil analysis

From three locations in each plot, we collected a bulked soil sample from the upper 10 cm of the mineral soil layer. The samples were sieved (<2 mm) and remaining, visible plant particles were removed. Soil pH was measured in 1 molar KCl. For gas-chromatographically measuring total soil carbon and nitrogen concentrations, fresh soil was dried for 72 hours at 105 °C and then milled to fine powder. To determine the concentrations of the base cations calcium, magnesium and potassium, fresh soil was percolated in a solution of 0.1 molar barium chloride. Afterwards, the cation concentrations were measured by atomic absorption spectrometry (ContrAA 300 AAS, Analytik Jena, Jena, Germany). The concentration of hydrogen ions was measured by determining the pH of the percolates, and the cation exchange capacity (CEC) was calculated as the sum of ion equivalents of all measured exchangeable cations (Ca, K, Mg and H). For the determination of bioavailable phosphorus, the soil samples were analyzed using the method proposed by Olsen (1954). The ratios of N:P and of C:P were calculated based on the results for N, C and P.

Species richness, community-weighted trait means and functional diversity

Species richness, community-weighted trait means and functional diversity were calculated based on vegetation surveys and leaf samples collected on the plots. See Ratier Backes et al. (2021) for more details. Species richness was defined as the total number of species recorded per plot. Community-weighted trait means (CWMs) were calculated for each of the five leaf traits (SLA, LDMC, leaf N, leaf N:P ratio, leaf C:P ratio) and for each plot, as follows:

CWM = i=1Npitraiti      (1)

where pi is the relative cover of species i in the community, and traiti is the trait value of species i.

To quantify functional diversity (FD), we calculated Rao’s quadratic entropy for each plot:

Rao’s Q = i=1N-1j=i+1Npipjdij   (2)

where the species’ trait distances are weighted by their relative abundance in the community. N is the number of species in the plot, pi and pj are the relative cover of species i and j, and dij is the trait distance between species i and j. Thus, Rao’s Q gives the mean functional distance between any two species in a plot. We included all five leaf traits in the calculation of Rao’s Q (multi-trait functional diversity).

Usage Notes

Missing values in the bioclimatic variables bio10 and bio11 correspond to plots where the loggers could not be installed, were lost or damaged. For the soil samples, missing values correspond to plots where samples could not be taken (e.g., on purely rocky areas) or samples for which phosphorus measurement failed. For CWMs, NAs represent plots with no species, and for Rao's Q they correspond to plots with less than 2 species. Please refer to the ReadMe file for more information.

Funding

Deutsche Forschungsgemeinschaft, Award: DFG—FZT 118, 202548816