The relationship between plant species richness and soil pH vanishes with increasing aridity across Eurasian dry grasslands

Abstract

Aim Soil pH is considered an important driver of fine‐scale plant species richness in terrestrial ecosystems. However, it is unclear to what extent this relationship is influenced by precipitation, which often directly affects both soil pH and species richness. We asked: (1) what is the relationship between fine‐scale vascular plant species richness and soil pH in regions with different levels of precipitation and (2) what are the relative effects of soil pH and precipitation on species richness? Location Dry grasslands in eight regions of northern Eurasia. Methods Species richness and soil pH were measured in 1055 10 m × 10 m plots and precipitation values were derived from global datasets. Relationships between variables were explored using general linear models, mixed‐effect models and partial regressions. Variation partitioning was used to assess the relative effect of each predictor on species richness. Results In wetter regions, soil pH range was broader, mean species richness was higher and the richness–pH relationship was unimodal. In drier regions, mean soil pH was higher and its range narrower, species richness was on average lower and less variable, and the richness–pH relationship was negative or absent. The richness–pH relationship persisted after controlling for the effect of precipitation, but precipitation, uniquely or together with soil pH, explained more variation in species richness in most regions than did pH alone. Main conclusions The relationship between plant species richness and soil pH in dry grasslands changes from unimodal, through negative, to none with decreasing regional precipitation in Eurasia. However, it seems that the species richness–soil pH relationship in dry grasslands over broad areas is substantially influenced and confounded by precipitation either indirectly, by shortening and shifting the pH gradient, or directly, by decreasing the negative effects of drought stress on richness.

Water or soil—What is the dominant driver controlling the vegetation pattern of degraded shallow mountain peatlands?

“…(Jeglum, ; Swanson & Grigal, ), whereas much more diverse plant communities occur in soligenic fens (minerotrophic) with higher species numbers (Hill et al, ). The abundance of species within bogs could be constrained by high phytotoxicity and nutrient limitations (Palpurina et al, ) resulting from high soil acidity. On the other hand, the occurrence of undesired species denotes peatland disturbances (Feldmeyer‐Christe & Küchler, ) caused predominantly by direct human interventions (Glina et al, 2016; Luscombe et al, ).…”

“…Vegetation is spatially heterogeneous and its constituent species show patterning, that is, departure from randomness of distribution (Grieg‐Smith, ). The identification of mechanisms that affect the variation in plant species distribution is an important goal in vegetation ecology (e.g., Hulisz, Piernik, Mantilla‐Contreras, & Elvisto, ; King, Richardson, Urban, & Romanowicz, ; Palpurina et al, ; Sewerniak & Jankowski, ). The need to perform such investigations has escalated in the last decades due to ongoing climate change and human activities (Koenig, Feldmeyer‐Christe, & Mitchell, ).…”

Groundwater Depth and Soil Properties Are Associated with Variation in Vegetation of a Desert Riparian Ecosystem in an Arid Area of China

“…In our study, species richness, community coverage and FPC were not highest in the sites with the shallowest groundwater depth (high pH and low EC; Tables 1 and 2), whereas the maximum species richness (i.e., S3) mainly occurred in the sites with low soil pH and EC (Table 2). Potential mechanisms for this result may be that physiological stress limits the number of species adapted to high pH [61]. In the lower reaches of the Heihe River, species richness, community coverage and FPC were mainly influenced by groundwater depth, and then affected by soil saline-alkali when groundwater depth increased to a specific value, at which point community coverage decreased.…”

Holocene matters: Landscape history accounts for current species richness of vascular plants in forests and grasslands of eastern Central Europe

“…In Eurasia, the species‐richest local communities occur in the forest‐steppe zone (Chytrý et al, ; Dengler, Janišová, Török, & Wellstein, ; Feurdean et al, ) rather than in dry steppes (Horsák & Chytrý, ; Palpurina et al, ). Hence, plant species richness usually increases with humidity within the steppe biome (Palpurina et al, ; Polyakova et al, ). In the region of species‐rich grasslands in our study area, mesic soils show the highest local species richness (Hájek et al, ).…”

“…Biodiversity loss is one of the most serious environmental risks nowadays. It is hence of prime importance to identify areas of high species richness and their ecological determinants (Kreft & Jetz, ; Palpurina et al, ; Zobel, ). While tropical rainforests and Mediterranean‐type vegetation are commonly reported as global hotspots of plant species richness (Archibold, ; Kreft & Jetz, ), exceptionally species‐rich communities have also been identified in the temperate zone, in particular in the forest‐steppe biome (Feurdean, Ruprecht, Molnár, Hutchinson, & Hickler, ; Večeřa et al, ).…”