Experimental warming does not change fluctuating asymmetry in three willow species

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 ..., , # 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) constructe...,