Effects of flowers on land surface albedo and soil microclimate

The phenology of vegetation, namely leaf-out and senescence, can influence
the Earth’s climate over regional spatial scales and long time periods
(e.g., over 30 years or more), in addition to microclimates over local
spatial scales and shorter time periods (weeks to months). However, the
effects of flowers on climate and microclimate are unknown. We investigate
whether flowers can influence light reflected by the land surface and soil
microclimate in a subalpine meadow. We conducted a flower removal
experiment with a common sunflower species, Helianthella
quinquenervis, for 3 years (2015, 2017, and 2019). The flower removal
treatment simulates the appearance of the meadow
when Helianthella flowers earlier under climate change
and loses its flowers to frost (other plant structures are not damaged by
frost). We test the hypotheses that a reduction in cover of yellow flowers
leads to a greener land surface, lower reflectance, warmer and drier
soils, and increased plant water stress. Flower removal plots are greener,
reflect less light, exhibit up to 1.2 °C warmer soil temperatures during
the warmest daylight hours, and contain ca. 1% less soil
moisture compared to controls. However, soils were warmer in only 2 of the
3 years, when flower abundance was
high. Helianthella water use efficiency did not differ
between removal and control plots. Our study provides evidence for a
previously undocumented effect of flowers on soil microclimate, an effect
that is likely mediated by climate change and flowering phenology. Many
anthropogenic environmental changes alter landscape albedo, all of which
could be mediated by flowers: climate change, plant invasions, and
agriculture. This study highlights how further consideration of the
effects of flowers on land surface albedo could improve our understanding
of the effects of vegetation on microclimate.