Variations in CSR strategies along stress gradients in the herb layer of submediterranean forests (central Italy)

Abstract

Background and aims – Species grouping in plant functional types (PFTs) according to Grime’s CSR theory has been found useful in understanding ecosystem functioning and processes and in quantifying variation along environmental gradients. However, little is known about the relationship between herbaceous plant strategies and stress gradients in submediterranean forest ecosystems. Our aim was to\ud assess variations in CSR strategies along three stress gradients (related to the amount of photosynthetically\ud active radiation, soil water deficit, and soil total nitrogen content) in the herb layer of submediterranean forests.\ud Material and methods – We collected floristic (species cover in the herb layer) and environmental data about topography, soil and light conditions in 48 sampling plots in a forest landscape of central Italy.\ud We performed canonical redundancy analyses (RDAs) of species and PFT data sets, constrained by photosynthetically active radiation, soil water deficit and soil total nitrogen content. Cover trends of PFTs along the environmental gradients were graphically represented.\ud Key results – All the environmental factors considered did affect ecological strategies in the herb layer, but the variation of both species and PFT data sets were best explained by photosynthetically active radiation. Competitors were favoured by low/intermediate stress levels, with regard to soil water and light intensity. Competitive stress-tolerant ruderals peaked in moderate light stress intensity and in well-watered soils. Stress-tolerant competitors peaked in conditions of strong light and moderate dryness.\ud Conclusions – Spatial variations in environmental conditions and in the related stress gradients determine predictable variations in the functional composition of the herb layer. Therefore, it may be possible to use Grimes’s PFTs for assessing environmental constraints and predicting whether a species with a specific strategy is likely to be positively or negatively affected by changes in environmental stress due, for instance, to climate change

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

“…Tree layer SCA (a proxy for light conditions) was the most important factor. This is in line with the study of Catorci et al (2011), who found that the variation in trait data in the herb layer of Sub-Mediterranean forests was best explained by photosynthetically active radiation. Looking at the patterns for our plots, the C-score increased along the tree layer SCA gradient, suggesting that competitors are more abundant in shaded understory environments.…”

“…In mature forest stands the closed tree layer canopy induces a strong filtering effect by limiting light availability at the forest floor. Species composition and diversity and the cover of herb-layer communities might be additionally filtered by other environmental stressors, such as low nutrient availability on silicate bedrock or a water deficit on drier sites (lower soil moisture and air humidity) (Catorci et al 2011). Similarly, coldinduced stress at higher altitudes favours species with a notable degree of conservatism, e.g.…”

Environmental filtering is the primary driver of community assembly in forest–grassland mosaics: A case study based on CSR strategies

“…Similar to Catorci et al. (2011) and Han et al. (2021), we found that the CSR strategy types offer a useful tool for the study of plant‐community assembly rules along gradients.…”

“…Similar to Catorci et al (2011) and Han et al (2021), we found that the CSR strategy types offer a useful tool for the study of plantcommunity assembly rules along gradients. However, a considerable limitation of our study was the limited length of the gradient.…”

Pedo-climatic and land use preferences of Gentiana lutea subsp. lutea in central Italy

“…These data were processed using the software developed in Microsoft Office Excel 2000 by Armiraglio et al (2003), to calculate soil water deficit (mm yr -1 ), namely the difference between potential and actual evapotranspiration in a given site. This method allows estimation of the available water capacity and of the summer water deficit of the soil, so that the resulting values can be used for making comparisons among sites within homogeneous macro-environmental conditions (Catorci et al 2011b). As AWC and summer water deficit are key factors to understand the ecological needs of the species, we represented their frequency distribution using box-plots, to search for the possible presence of outliers to be excluded in the definition of the optimal range for the species.…”