Ecotypic differentiation, reflected in substantial trait differences across populations, has been observed in various plant species distributed across aridity gradients. Nevertheless, ecotypic differentiation in leaf silicon concentration, known to alleviate drought stress in plants, remained hardly explored. Here, we provide a systematic test for ecotypic differentiation in leaf silicon concentration along two aridity gradients in the grass Brachypodium hybridum in Israel. Seed material was sampled in 15 sites along a macroclimatic aridity gradient (89 – 926 mm mean annual rainfall) and from corresponding north (moister) and south (more arid) exposed slopes (microclimatic gradient) at similar altitudes (mean north: 381 m a.s.l., mean south: 385 m a.s.l.). Plants were subsequently grown under common conditions and their leaf silicon concentration was analysed. Leaf silicon concentration increased with increasing aridity across the macroclimatic gradient, but did not differ between north and south slopes. The higher leaf silicon concentrations under more arid conditions can enhance the ability of plants to cope with more arid conditions by two mutually not exclusive mechanisms: (i) withstanding drought by reducing water loss and increasing water uptake or (ii) escaping drought by facilitating fast growth. Our study highlights that leaf silicon concentration contributes to ecotypic differentiation in annual grasses along macroclimatic aridity gradients.

Silicon (Si) content in plant tissues is considered a functional trait that can provide multiple morpho-physiological benefits to plant individuals. However, it is still unclear whether and how these individual benefits extend to plant community processes and ecosystem functioning. Here we investigated how plant Si content is associated with plant community properties and the ecosystem structure of herbaceous communities in Israel. We sampled 15 sites across the Mediterranean and desert ecosystems and built models to evaluate how plant silicon content (community-weighted mean and standard variation) is associated with variables such as species richness, biomass production, plant cover, and functional diversity. Finally, we used model selection techniques to test whether models depicting plant Si content perform better than models using data on soil Si instead. Sites with lower susceptibility to drought had significantly more Si-accumulating grass species and higher soils Si content. Models with plant Si content instead of soil Si, always performed better, although those considering Si content variation had overall stronger associations with community properties than only mean Si content. For instance, up to 51% of plant Si content variation was explained by climate, biomass production, and species richness, combined. Still, mean plant Si content and plant cover combined explained up to 42% of plant functional diversity. Our results suggest the that plant Si content serves as a proxy for understanding the ecological properties and functioning of arid and Mediterranean ecosystems. Nevertheless, the significance of Si has not been fully explored in other ecosystem types, where its influence may be less pronounced compared with the ecosystems examined in this study. In light of various global change scenarios, enhancing our understanding of Si as a plant functional trait could help bridge existing knowledge gaps and improve ecological modeling, thus enabling more accurate forecasts of changes in plant distributions.

Functional biogeography is the discipline that studies the geographic distribution of organismal traits and their relationships with environmental conditions and ecosystem functioning. Trait multifunctionality can be a major challenge in such analyses, so deciphering trait geographic distributions from functions is not always straightforward. We studied spinescence in the flora of Israel and the Palestinian Authority as a case of a multifunctional trait, associated mainly with antiherbivory defence, aridity alleviation, and propagule and seed dispersal. We studied how the proportion of spiny species in the flora of Israel and the Palestinian Authority and the distribution of different spine locations within the plants vary along a very strong bioclimatic (especially rainfall) gradient in Israel and the Palestinian Authority. We found that plant spinescence, as expressed in species proportion, is more frequently positively associated with increasing aridity and summer heat, and more generally with resource limitations. However, spinescence of reproductive plant parts, which in many species aids seed dispersal, presents opposite trends. These patterns reflect the differing importance of each of the three major roles attributed to plant spinescence, and point to the relative importance of each in driving overall spinescence geographic distribution. Thus, the traits’ geographic distribution patterns can elucidate these traits’ multifunctionality and improve our understanding of the evolution and spatial variation among these functions.

Arid environments are characterized by rare rain events that are highly variable, as a result of which plant populations often exhibit episodic recruitment and mortality dynamics. However, direct records and observations of such events are rare because of the slow development of woody species. In this study, we described how a decrease in annual precipitation affected acacia tree population dynamics in two hydrological regime types: small wadis and salt flats. This study combines 15 years of continuous, yearly field monitoring of individual acacia trees and data from a historical Corona satellite image, which has extended the time scope of the research. Results indicate that the annual mortality of acacia trees in small wadis reflects the cumulative effective rain events in the preceding five years, whereas the population on the salt flats was not affected by annual rainfall fluctuations. Moreover, in small wadis, rain events of less than 8 mm did not increase acacia tree survival rates. The mortality pattern and dynamics of each plot was unique, suggesting unsynchronized mortality and recruitment episodes on a regional scale. Mortality in all plots was documented both in “old” trees (i.e., recognized in 1968) and “new” trees (not recognized in 1968), but varied highly between plots. More than 50% of the dead trees recorded at the sites had died during the previous dry period (2000–2010). Combining field monitoring and historical satellite image data provided a unique database of acacia population dynamics. This record revealed the response of the acacia population to climate fluctuations and a period of episodic mortality.

Spatial heterogeneity affects plant community composition and diversity. It is particularly noticeable in annual plant communities, which vary in space and time over short distances and periods, forming meta-communities at the regional scale. This study was conducted at the coastal dune ecosystem in Nizzanim nature reserve, Israel. This study aimed to analyze the effect of the spatial heterogeneity, which is expressed in differences in the fixation levels of the dunes and patches outside and beneath the dominant Artemisia monosperma shrubs, on the characteristics of the annual plant meta-community and its temporal stability, considering the mechanisms that may affect it. Thirteen dunes were studied: three mobile, seven semi-fixed, and three fixed dunes. Data on the annual plants were collected during the spring seasons of 2006, 2007, 2009, 2014, 2015, and 2016. For each dune, 72 quadrats of $40\times 40$ cm were sampled yearly, with 24 quadrats per slope aspect (windward, leeward, and crest), 12 under the shrub, and 12 in the open. The results indicate that the transition from mobile dunes through semi-fixed to fixed dunes is characterized by an increase in annual plant cover, species richness, species diversity, changes in plant communities, and stability driven by the asynchrony of species population fluctuations. Asynchrony affected the stability of the meta-community of this ecosystem in patches beneath the shrubs but not in the open patches.

Despite seminal papers that stress the significance of silicon (Si) in plant biology and ecology, most studies focus on manipulations of Si supply and mitigation of stresses. The ecological significance of Si varies with different levels of biological organization, and remains hard to capture. We show that the costs of Si accumulation are greater than is currently acknowledged, and discuss potential links between Si and fitness components (growth, survival, reproduction), environment, and ecosystem functioning. We suggest that Si is more important in trait-based ecology than is currently recognized. Si potentially plays a significant role in many aspects of plant ecology, but knowledge gaps prevent us from understanding its possible contribution to the success of some clades and the expansion of specific biomes.

Economics, ecology and archaeology study various aspects of resource utilisation and mobilisation, differing in the studied systems, objects and currencies. However, the three disciplines have developed mostly independently, resulting in limited dialogue among them. Emergent fields such as ecological economics and environmental archaeology are now linking the three disciplines and promoting dialogue among them, but a theoretical framework that links all three disciplines at once is missing. I propose that ecosystem services (ES) can serve as such a theoretical framework. Moreover, after an ES-centred framework establishes, it will be capable of further evolving – independently of ES—into a unified superdiscipline, relieving boundaries among disciplines. To demonstrate this potential, I present some examples of archaeology-ES linkages, relating to the past, present and future. I show, in general, how archaeology studies past ES and informs us on current ES, as well as how ES benefit archaeological practice. Thus, I demonstrate the strong interface between archaeology and ES, and how it can promote the dialogue among the three disciplines, provide them with new practical tools, and resolve theoretical issues as the sustainability of ancient societies and anthropocentricity and monetisation of ES.

Purpose

Silicon (Si) accumulation is an important strategy for plant defense against biotic and abiotic stress. Solid amorphous silica (ASi) deposits have been found to protect plants against different stressors (e.g., drought stress, ultraviolet radiation, herbivory, and pests). Most research on ASi deposits and their subsequent function is conducted under lab conditions. However, it is still unclear at which stage in ontogeny ASi deposits are developed to fulfill their function in plant protection under field conditions.

Methods

We combined SEM–EDX, NMR spectroscopy, and Si extractions to analyze silicification patterns in wheat leaves (blades and sheaths) in relation to ontogeny and soil Si availability.

Results

Silicification patterns in wheat leaves varied strongly in intensity between four different growth stages (tillering, stem extension, heading, and grain filling) and ASi deposition did not just continuously increase over the growing season. Newly formed leaf tissues showed relatively low Si concentrations, which increased over time. A high condensation state of the silica bodies and trichomes was found at all growth stages, referring to a high rigidity of the silica bodies.

Conclusions

Our results indicate that development of ASi deposits in wheat leaves depends on growth stage and Si availability. Detailed knowledge on solid ASi deposition in wheat during ontogeny and its consequences for stress mitigation is crucial for farmers worldwide.

Main conclusion

The divergences in propagule mass have been more consistently associated with divergences in seed development duration or fruit pedicel cross-sectional area than with divergences in any other biotic factors.

Abstract

Allometry and Corner’s rule became an important theme in evolutionary biology of plant trait structure and function. Being one of the most widely noticed plant traits, propagule (seed and fruit) mass variation mechanism across species is still controversial. Here we examined correlations between propagule mass and seed development duration as well as other traits, such as cross-sectional area of fruit pedicel, life form, fruit type and leaf area over four census years, to test an important life history strategy for propagule biomass allocation. We investigated 491 species, belonging to 91 families and 320 genera, representing 95% of native wild species in Beijing Botanical Garden. The scaling correlations between propagule mass and seed development duration and the other traits were determined using phylogenetic generalized linear models. Results show a significant positive relationship among propagule mass and seed development duration, leaf area and pedicel cross-sectional area for all species and for each life form (except vines) regardless of phylogeny. The variation in seed mass has been more consistently associated with variation in seed development duration than with divergences in any other variable, such as growth form, fruit type, pedicel cross-sectional area and leaf area, whereas variation in fruit weight was found to be more associated with variation in pedicel cross-sectional area than the other. Biotic factors, such as seed development duration, pedicel cross-sectional area, growth form and leaf area, mediate propagule size variation, of which seed development duration or pedicel cross-sectional area is the most important. The results further supported a hypothesis that large-seeded species evolved owing to high photosynthate availability and growth allometry in plant body. A mechanistic mathematical model involving seed development duration was provided to expound propagule mass variations across species.

Plants’ ability to take up silicon from the soil, accumulate it within their tissues and then reincorporate it into the soil through litter creates an intricate network of feedback mechanisms in ecosystems. Here, we provide a concise review of silicon’s roles in soil chemistry and physics and in plant physiology and ecology, focusing on the processes that form these feedback mechanisms. Through this review and analysis, we demonstrate how this feedback network drives ecosystem processes and affects ecosystem functioning. Consequently, we show that Si uptake and accumulation by plants is involved in several ecosystem services like soil appropriation, biomass supply, and carbon sequestration. Considering the demand for food of an increasing global population and the challenges of climate change, a detailed understanding of the underlying processes of these ecosystem services is of prime importance. Silicon and its role in ecosystem functioning and services thus should be the main focus of future research.