Ecosystem Processes Show Uniform Sensitivity to Winter Soil Temperature Change Across a Gradient from Central to Cold Marginal Stands of a Major Temperate Forest Tree

Abstract

The magnitude and frequency of soil frost events might increase in northern temperate regions in response to climate warming due to reduced insulation caused by declining snow cover. In temperate deciduous forests, increased soil frost severity can hamper tree growth and increase the mortality of fine roots, soil fauna and microorganisms, thus altering carbon and nutrient cycling. From single-site studies, however, it is unclear how the sensitivities of these responses change along continental gradients from regions with low to high snowfall. We conducted a gradient design snow cover and soil temperature manipulation experiment across a range of lowland beech forest sites to assess the site-specific sensitivity of tree growth and biogeochemical cycling to soil cooling. Even mild and inconsistent soil frost affected tree increment, germination, litter decomposition and the retention of added 15N. However, the sensitivity of response (treatment effect size per degree of warming or cooling) was not related to prevailing winter climate and snow cover conditions. Our results support that it may be valid to scale these responses to simulated winter climate change up from local studies to regional scales. This upscaling, however, needs to account for the fact that cold regions with historically high snowfall may experience increasingly harsh soil frost conditions, whereas in warmer regions with historically low snowfall, soil frost may diminish. Thus, despite the uniform biotic sensitivity of response, there may be opposing directions of winter climate change effects on temperate forests along continental temperature gradients due to different trends of winter soil temperature.

Warmer winters result in reshaping of the European beech forest soil microbiome (bacteria, archaea and fungi)—With potential implications for ecosystem functioning

“…Generally, we found more significant responses among the bacteria/archaea than fungi, which is in line with another finding of bacteria/archaea showing higher responsiveness than fungi to short‐term environmental changes, as shown for beech forest soil microbiomes (Choma et al, 2020). Such short‐term responsiveness is in line with our third hypothesis, namely that microorganisms might undergo changes at a different time scale than, for example, plants (no response was seen for the forest understory composition; Weigel et al, 2021). Such a decoupling in response might affect ecosystem functioning and the availability of plant nutrients (Bardgett et al, 2013; Yanai et al, 2004).…”

“…Such a decoupling in response might affect ecosystem functioning and the availability of plant nutrients (Bardgett et al, 2013; Yanai et al, 2004). In accordance, a reduced tree growth was observed from the short‐term soil cooling experiment (S− affected plots) as well as from soil frost‐affected sites along the gradient (Weigel et al, 2021). Among the bacteria, the core‐member genus Bradyrhizobium had a consistently reduced relative abundance under short‐ and long‐term cold conditions.…”

“…Distance‐based redundancy analysis (dbRDA) was carried out using Bray–Curtis dissimilarity matrix. Investigated variables were ‘Site (KO, GR, DE, WE, KA, BB, NZ, HH and BH)’, ‘treatment (C, S− and S+)’, ‘Shannon Diversity index for the vegetation’, ‘sample score for 1 st NMDS axis for the vegetation composition’ and ‘sample score for second NMDS axis for the vegetation composition’ (obtained from Weigel et al, 2021), ‘soil frost‐degree‐hours’, ‘average soil temperature’, ‘minimum soil temperature’, ‘freeze–thaw‐cycles', ‘NO3‐N availability’, ‘NH4‐N availability’ (measured as absorption to resin plates throughout the experimental winter, for details see Weigel et al, 2021), ‘Green tea decomposition’, ‘Tree stem growth’. The partitioning of variance on the significant axis was reported ( p < 0.05, PERMANOVA with 999 permutations).…”

Plant diversity stabilizes soil temperature

“…Although the effect size was much smaller in winter (Fig. 1a, b), it is nonetheless important because even a small difference can imply freezing vs. non-freezing soil conditions 26 .…”

Spatial variation of soil temperature fields in a urban park

“…Soil thermal regime is one of the most important factors in soil formations [36] and living conditions for terrestrial biota [37,38]. A significant horizontal variation in the temperature of the upper soil horizons was found, which in forest ecosystems is related to the spatial heterogeneity of the tree stand and the understorey [39,40]. The studies of temperature fields with long time series began with the advent of programmable sensors.…”