Variation in floristic and trait composition along environmental gradients in the herb layer of temperate forests in the transition zone between Central and SE Europe

Abstract

Species- and trait-environment linkages in forest plant communities continue to be a frequent topic in ecological research. We studied the dependence of floristic and functional trait composition on environmental factors, namely local soil properties, overstory characteristics, climatic parameters and other abiotic and biotic variables. The study area comprised 50 monitoring plots across Slovenia, belonging to the EU ICP Forests monitoring network. Vegetation was surveyed in accordance with harmonized protocols, and environmental variables were either measured or estimated during vegetation sampling. Significant predictors of species composition were identified by canonical correspondence analysis. Correlations between plant traits, i.e. plant growth habit, life form, flowering features and CSR signature, were examined with fourth-corner analysis and linear regressions. Our results show that variation in floristic composition was mainly explained by climatic parameters (mean annual temperature, mean annual precipitation), soil properties (pH) and tree layer-dependent light conditions. Trait composition was most closely related with tree layer characteristics, such as shade-casting ability (SCA, a proxy for light availability in the understory layer), tree species richness and tree species composition. Amongst soil properties, total nitrogen content and soil texture (proportion of clay) were most frequently correlated with different species traits or trait states. The CSR signature of herb communities was associated with tree layer SCA, soil pH and mean annual temperature. The floristic composition of the studied herb-layer vegetation depended on temperature and precipitation, which are likely to be influenced by ongoing climate change (warming and drying). Trait composition exhibited significant links to tree layer characteristics and soil conditions, which are in turn directly modified by forest management interventions.

Bryophyte diversity, composition and functional traits in relation to bedrock and tree species composition in close-to-nature managed forests

“…arundinacea (Schrank) K. Richt, ferns Pteridium aquilinum (L.) Kuhn, Blechnum spicant (L.) Roth and berries Vaccinium myrtillus and V. vitis-idaea are common. In some of the study plots, the forest floor was almost completely covered by these species (Kermavnar and Kutnar 2020;Kermavnar et al 2021aKermavnar et al , 2021b. This is consistent with an experimental study of traits in which the bryophyte specific shoot length increased with increasing vegetation height and litter cover, indicating stronger competition from vascular plants (Van Zuijlen et al 2021).…”

Mixed signals of environmental change and a trend towards ecological contraction in ground vegetation across different forest types

“…We opted for: tree layer shade-casting ability (EIV-L), mean annual temperature (EIV-T), soil moisture (EIV-F), soil pH (EIV-R) and total nitrogen content in the soil (EIV-N). All these variables were available from our previous study (Kermavnar et al 2022). In the Results section, the variable with higher explanatory power is presented.…”

Environment shapes tree community traits in China's forests

“…It is important to note that we considered only woody plants in the tree communities, whereas Bruelheide et al (2018) included understorey plants, such as herbaceous plants and shrubs, in forests. The trait composition of the understorey layer is influenced by not only the environment (Cubino et al, 2021), but also canopy shading (Kermavnar et al, 2021). Recently, studies have also found variable trait–environment relationships between trees and herbs (Simova et al, 2018; Cheng et al, 2022).…”