DOI: 10.5061/dryad.n8pk0p38b
title: Data from: Experimental warming does not change fluctuating asymmetry in three willow species

description: Fluctuating asymmetry (FA) is often proposed as an early warning indicator
 of subtle changes in plant functioning. Here, we tested whether leaf FA
 responds consistently to the alleviation of cold stress in three boreal
 willow species—Salix caprea, S. myrsinifolia, and S. phylicifolia. We
 enclosed 10 naturally growing individuals of each species in open-top
 chambers at budburst and compared their leaf traits to those of unenclosed
 control plants after leaf development had ceased. All measurements were
 conducted blind to treatment. Willows in open-top chambers showed a 9 %
 increase in specific leaf area, indicating that the 1–2 °C warming within
 chambers affected leaf development. However, neither leaf length nor FA
 responded significantly to the warming treatment. FA also did not differ
 among species or individual plants, suggesting that it may reflect
 statistical noise rather than a reliable biological signal in this
 context. These findings add to growing concerns that many reported FA
 responses to environmental change may result from confirmation bias—an
 issue that can be mitigated by adopting blind measurement protocols.
description: # Data from: Experimental warming does not change fluctuating asymmetry in
 three willow species Dataset DOI:
 [10.5061/dryad.n8pk0p38b](https://doi.org/10.5061/dryad.n8pk0p38b) ##
 Description of the data and file structure This study was conducted at the
 Central Manor site of the Lapland Biosphere Reserve (67°39′09″ N,
 32°38′35″ E; 140 m a.s.l.), located approximately 130 m below and 1 km
 from the alpine treeline. The experimental plot (50 × 50 m size) was
 originally cleared in the 1970s for use as a helicopter landing pad within
 a sparse spruce forest (Fig. 1). After maintenance ceased in the late
 1980s, the area was naturally recolonised by willows. We selected 20
 individuals per willow species (*Salix caprea* L., *S. myrsinifolia*
 Salisb., and *S. phylicifolia* L.), each between 50 and 120 cm tall, and
 randomly assigned them to either ambient conditions or the open-top
 chamber (OTC) treatment. The OTCs were rectangular structures (80 × 80 cm
 at the base and 160 cm tall) constructed from 120 μm polyethylene film
 mounted on metal frames. They were installed on 2 June 2000, shortly after
 budburst in willows. Prior assessments indicated that these chambers
 consistently raised air temperature by approximately 1–2 °C compared to
 ambient conditions. On 8 July 2000, once the willow leaves had reached
 their final size, we haphazardly collected 10 leaves from each individual,
 prioritising leaves located midway along the current year’s shoots. The
 collector was blinded to the study hypothesis. The leaves were press-dried
 and mounted as standard herbarium specimens on sturdy A4 paper (210 × 297
 mm) in preparation for scanning (Data S1). All measurements were performed
 using the freeware ImageJ 1.54g program. Image files were anonymised to
 ensure that the measurer was blinded to the treatment applied to each
 sample. Based on the image dimensions (2480 × 3507 px), the measurement
 tool in ImageJ was calibrated using the ‘Set Scale’ function. Measurements
 were taken using the ‘Line’ tool. Leaf blade length was measured as the
 distance from the tip to the base of the blade, excluding the petiole. A
 line perpendicular to the main vein was drawn from the midpoint of the
 line connecting these landmarks using an ImageJ macro. The distances from
 the main vein to the left and right edges of the blade were then measured
 along this line to the nearest 0.01 mm. All values were recorded in the
 Results Manager. Each measurement was conducted twice, with a one-week
 interval. The second set of measurements was performed blindly with
 respect to the first set (Data S2). After scanning, every second leaf was
 removed from the sheet. The samples of five leaves per plant were dried at
 105 °C for 24 h and weighed to the nearest 0.1 mg (Data S3). The specific
 leaf area (SLA) was calculated as the ratio of leaf area to dry mass. ###
 Files and variables #### File: Gavrikov-etal-DataS3-120725.txt
 **Description:** Measurements of leaf weight and area. ##### Variables *
 Column 1: Species (salcap, *Salix caprea*; salmyr, *S. myrsinifolia*;
 salphy, *S. phylicifolia*). * Column 2: Treatment (y, enclosed in open-top
 chamber; n, unenclosed control). * Column 3: Plant individual (1 to 20,
 nested within each species). * Column 4: Average leaf weight (mg). *
 Column 5: Average leaf area (mm^2^). #### File:
 Gavrikov-etal-DataS2-120725.txt **Description:** Measurements of leaf
 length and half-width. ##### Variables * Column 1: Species (salcap, *Salix
 caprea*; salmyr, *S. myrsinifolia*; salphy, *S. phylicifolia*). * Column
 2: Treatment (y, enclosed in open-top chamber; n, unenclosed control). *
 Column 3: Plant individual (1 to 20, nested within each species). * Column
 4: Leaf number (1 to 10, nested within each plant). * Column 5: Leaf
 length (mm), 1st measurement. * Column 6: Left half-width (mm), 1st
 measurement. * Column 7: Right half-width (mm), 1st measurement. * Column
 8: Leaf length (mm), 2nd measurement. * Column 9: Left half-width (mm),
 2nd measurement. * Column 10: Right half-width (mm), 2nd measurement. ####
 File: Gavrikov-etal-DataS1-120725.pdf **Description:** Images of measured
 leaves. Pages 1–14: *Salix caprea*. Pages 15–21: *S. myrsinifolia*. Pages
 22–26: *S. phylicifolia*. Within each species, plants are numbered 1–20,
 and leaves within each plant are numbered 1–10 from left to right. Image
 size: 210 × 297 mm. ## Code/software Data S1 is .pdf file; Data S2 and
 Data S3 are space-delimited .txt files.