The diversity of species combinations observable in sampling units reflects a species' uneven distribution and preference for specific abiotic and biotic conditions – a phenomenon most commonly ...expressed in terms of ecological assembly rules of plant communities and other sessile organisms (e.g. subtidal algae, invertebrates and coral reefs). We present comspat, a new R package that uses grid or transect data sets to measure the number of realized (observed) species combinations (NRC) and the Shannon diversity of realized species combinations (compositional diversity; CD) as a function of spatial scale. NRC and CD represent two measures from a model family developed by Pál Juhász‐Nagy based on information theory. Classical Shannon diversity measures biodiversity based on the number and relative abundance of species, whereas the specific version of Shannon diversity presented here characterizes biodiversity and provides information on species coexistence relationships; both measures operate at fine‐scale within the sampling unit or within the community. comspat offers two commonly applied null models, complete spatial randomness and random shift, to disentangle the textural, intraspecific and interspecific effects on the observed spatial patterns. Combined, these models assist users in detecting and interpreting spatial associations and inferring assembly mechanisms. Our open‐sourced package provides a vignette that describes the method and reproduces the figures from this paper to help users contextualize and apply functions to their data.
ABSTRACT
The prevailing paradigm about the Quaternary ecological and evolutionary history of Central European ecosystems is that they were repeatedly impoverished by regional extinctions of most ...species during the glacial periods, followed by massive recolonizations from southern and eastern refugia during interglacial periods. Recent literature partially contradicts this view and provides evidence to re‐evaluate this Postglacial Recolonization Hypothesis and develop an alternative one. We examined the long‐term history of the flora of the Carpathian (Pannonian) Basin by synthesising recent advances in ecological, phylogeographical, palaeoecological and palaeoclimatological research, and analysing the cold tolerance of the native flora of a test area (Hungary, the central part of the Carpathian Basin). We found that (1) many species have likely occurred there continuously since before the Last Glacial Maximum (LGM); (2) most of the present‐day native flora (1404 species, about 80%) can occur in climates as cold as or colder than the LGM (mean annual temperature ≤+3.5°C); and (3) grasslands and forests can be species‐rich under an LGM‐like cold climate. These arguments support an alternative hypothesis, which we call the Flora Continuity Hypothesis. It states that long‐term continuity of much of the flora in the Carpathian Basin is more plausible than regional extinctions during the LGM followed by massive postglacial recolonizations. The long‐term continuity of the region's flora may have fundamental implications not only for understanding local biogeography and ecology (e.g. the temporal scale of processes), but also for conservation strategies focusing on protecting ancient species‐rich ecosystems and local gene pools.
Display omitted
•Alpha diversity measures do not capture crucial information about plant interactions.•We propose an index called Compositional Diversity which takes into account species ...combinations.•Old-growth forests have unique understorey species assemblages.•Restoring forest plant assemblages requires a longer time scale than restoring alpha diversity.•Species combinations may be used to assess whether a given forest has reached old-growth features.
Biodiversity is changing rapidly, and ecologists use various measures to monitor and conserve it, but not all are equally effective. In the European temperate forests, ecologists are tasked with assessing the impact of global changes on plant species richness; however, this fails at capturing vital information about plant interactions. Using a chronosequence of beech forest stands, spanning 600 years of growth, we demonstrate the application of a different measure of diversity compared to classical species richness in the understorey. This measure, called compositional diversity (CD), considers the number of species combinations and their relative frequency within a community. The response of both classical species richness and CD along with succession, corresponded with our expectations based on ecological theory’s U-shape prediction of diversity along the successional gradient. However, after 300 years, there was a significant decoupling between the two measures’ responses. While species richness remained low and constant across old-growth and primeval forests, CD peaked in primeval forests, implying that the same number of late-successional species generated more diverse assemblages. This new information emphasises the need to protect old-growth and primeval forests not only to conserve species richness but also to preserve their unique network of species co-occurrence patterns – a factor not well represented by the classical species richness measure.
This paper explores which traits are correlated with fine-scale (0.25 m
) species persistence patterns in the herb layer of old-growth forests. Four old-growth beech forests representing different ...climatic contexts (presence or absence of summer drought period) were selected along a north-south gradient in Italy. Eight surveys were conducted in each of the sites during the period spanning 1999-2011. We found that fine-scale species persistence was correlated with different sets of plant functional traits, depending on local ecological context. Seed mass was found to be as important for the fine-scale species persistence in the northern sites, while clonal and bud-bank traits were markedly correlated with the southern sites characterised by summer drought. Leaf traits appeared to correlate with species persistence in the drier and wetter sites. However, we found that different attributes, i.e. helomorphic vs scleromorphic leaves, were correlated to species persistence in the northernmost and southernmost sites, respectively. These differences appear to be dependent on local trait adaptation rather than plant phylogenetic history. Our findings suggest that the persistent species in the old-growth forests might adopt an acquisitive resource-use strategy (i.e. helomorphic leaves with high SLA) with higher seed mass in sites without summer drought, while under water-stressed conditions persistent species have a conservative resource-use strategy (i.e. scleromorphic leaves with low SLA) with an increased importance of clonal and resprouting ability.
Empirical studies that link plants intraspecific variation to environmental conditions are almost lacking, despite their relevance in understanding mechanisms of plant adaptation, in predicting the ...outcome of environmental change and in conservation. Here, we investigate intraspecific trait variation of four grassland species along with abiotic environmental variation at high spatial resolution (
n
= 30 samples per species trait and environmental factor per site) in two contrasting grassland habitats in Central Apennines (Italy). We test for phenotypic adaptation between habitats, intraspecific trait-environment relationships within habitats, and the extent of trait and environmental variation. We considered whole plant, clonal, leaf, and seed traits. Differences between habitats were tested using ANOVA and ANCOVA. Trait-environment relationships were assessed using multiple regression models and hierarchical variance partitioning. The extent of variation was calculated using the coefficient of variation. Significant intraspecific differences in trait attributes between the contrasting habitats indicate phenotypic adaptation to in situ environmental conditions. Within habitats, light, soil temperature, and the availability of nitrate, ammonium, magnesium and potassium were the most important factors driving intraspecific trait-environment relationships. Leaf traits and height growth show lower variability than environment being probably more regulated by plants than clonal traits which show much higher variability. We show the adaptive significance of key plant traits leading to intraspecific adaptation of strategies providing insights for conservation of extant grassland communities. We argue that protecting habitats with considerable medium- and small-scale environmental heterogeneity is important to maintain large intraspecific variability within local populations that finally can buffer against uncertainty of future climate and land use scenarios.
In this study eight temperate grassland sites were monitored for soil CO2 efflux (Rs) and the spatial covariate soil water content (SWC) and soil temperature (Ts) at fine scale in over 77 measurement ...campaigns. The goals of this multisite study were to explore the correlations between environmental gradients and spatial patterns of Rs, SWC and Ts, which are not site-specific and to quantify the relevance of biotic and abiotic controls over spatial patterns along increasing vegetation structural complexity. These patterns in water-limited ecosystems in East-Central Europe are likely to be influenced by summer droughts caused by the changing climate.
A consistent experimental setup was applied at the study sites including 75 sampling locations along 15m circular transects. Spatial data processing was mainly based on variography. Two proxy variables were introduced to relate the site characteristics in terms of soils, water status and vegetation. Normalised SWC (SWCn) reconciled site-specific soil water regimes while normalised day of year integrated temperature and vegetation phenology.
A principal component analysis revealed that the progressing closure of vegetation in combination with large Rs and SWCn values, as well as low Ts and Rs variability support the detectability of spatial patterns found in both the abiotic and biotic variables. Our results showed that apart from SWC the pattern of soil temperature also had an effect on spatial structures. We detected that when the spatially structured variability of Ts was low, a strong negative correlation existed between SWCn and the spatial autocorrelation length of Rs with r=0.66 (p<0.001). However, for high spatially structured variability of Ts, occurring presumably at low Ts in spring and autumn, the correlation did not exist and it was difficult to quantify the spatial autocorrelation of Rs. Our results are indicative of a potential shift from homogeneity and dominance of biotic processes to an increased heterogeneity and abiotic regulation in drought prone ecosystems under conditions of decreasing soil moisture.
•Goodness of soil respiration variogram model fit is probably under biotic control.•Open vegetation is not favourable for the appearance of spatial structures.•Patterns of soil moisture and temperature constrain patch size of respiration.•Future less soil moisture may uncouple spatial links of drivers and respiration.
High variability of soil respiration measured at fine spatial scale increases the uncertainty when trying to determine the representative average soil respiration (Rs) flux. A possible way to ...decrease the uncertainty, while also optimising measurement effort, could be the calculation of required number of Rs measurements (Nopt) together with the optimisation of their spatial arrangement. The goals of this study were to find explanatory variables of the structural parameters of fine-scale Rs spatial pattern and of Nopt for sampling optimisation. We conducted field Rs, soil temperature (Ts) and soil water content (SWC) measurements in a Hungarian sandy pasture over several years along circular transects of 75 evenly spaced (20cm distance) sampling positions. Structural parameters of patterns of Rs and the covariates were determined from variograms. Ranges of spatial autocorrelation varied between 0 and 3.6m for Rs, 0 and 3m for SWC and 0 and 2.9m for Ts. Patch size of Rs depended negatively on transect average SWC. To understand and quantify the spatial dependence of variables, cross-variograms were calculated. Rs proved to be positively spatially correlated to SWC at low water supply, while Ts-Rs and SWC-Ts spatial correlations were mostly negative, both due the direct effect of evaporative cooling on Ts. We found that spatial patchiness became less robust and the correlations generally decreased as soil moisture content was high. We found that explanatory variable of Nopt was also SWC, with negative correlation between them. We conclude that sampling could be optimized on the basis of the easily measurable actual SWC, which determines both the optimal number of Rs measurements and the minimum distances between individual samples in semi-arid ecosystems.
•Spatial patch structure of soil respiration showed large temporal variability.•Drought limitation of soil respiration was coupled with changes in spatial structure.•Soil water content determined required sample size for soil respiration.•Actual patch size should be considered in soil respiration sampling design.
Diversity of subalpine semi-natural grasslands is threatened by both overgrazing and abandonment, resulting in degradation and woody plants encroachment, respectively. The effects of overgrazing, ...followed by a sharp decline of grazing are rarely assessed in uncontrolled conditions. We aimed at assessing plant species and functional diversity within the grass-dwarf shrub mosaic. Species abundance and selected plant functional traits (leaf, height, seed) were assessed within 16 m
2
plots in adjacent grass-dominated and low-cover dwarf shrub vegetation patches. Species-based and functional patterns were quantified by Simpson's diversity, Rao's quadratic entropy, the plot weighted mean of plant traits and analysed with NMDS ordination and linear mixed-effect models. Despite the appearance of dwarf shrub canopy effect and light competition, higher species-based and functional diversity were found in the dwarf shrub patch. Our results point to the strong legacy of past overgrazing and the related filtering effects on the trait complex of assembling species, especially in the grass-dominated patches. We conclude that pastures incorporating dwarf shrubs at low cover are favourable in terms of species and functional diversity and recommend the maintaining of intermediate grazing intensity to support mosaic vegetation structures that are beneficial for biodiversity conservation in the study area.
From a surgical point of view, quantification cannot always be achieved in the developmental deformity in hip joints, but finite element analysis can be a helpful tool to compare normal joint ...architecture with a dysplastic counterpart. CT scans from the normal right hip of an 8-year-old boy and the dysplastic left hip of a 12-year-old girl were used to construct our geometric models. In a three-dimensional model construction, distinctions were made between the cortical bone, trabecular bone, cartilage, and contact nonlinearities of the hip joint. The mathematical model incorporated the consideration of the linear elastic and isotropic properties of bony tissue in children, separately for the cortical bone, trabecular bone, and articular cartilage. Hexahedral elements were used in Autodesk Inventor software version 2022 (“Ren”) for finite element analysis of the two hips in the boundary conditions of the single-leg stance. In the normal hip joint on the cartilaginous surfaces of the acetabulum, we found a kidney-shaped stress distribution in a 471,672 mm2 area. The measured contact pressure values were between 3.0 and 4.3 MPa. In the dysplastic pediatric hip joint on a patch of 205,272 mm2 contact area, the contact pressure values reached 8.5 MPa. Furthermore, the acetabulum/femur head volume ratio was 20% higher in the dysplastic hip joint. We believe that the knowledge gained from the normal and dysplastic pediatric hip joints can be used to develop surgical treatment methods and quantify and compare the efficiency of different surgical treatments used in children with hip dysplasia.
PDF
