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Question: Rocky outcrops generally restrict recruitment and survival of plant species due to their environmental conditions including low soil moisture, nutrient shortages and microclimate harshness. Under such severe conditions, nurse plants may play critical roles in preserving plant biodiversity. Although the nurses' effects on plant biodiversity are fully understood in different major biomes, the relative effects of abiotic factors and nurse plants as important factors have rarely been studied in rocky outcrops, and compared to those in the surrounding rangelands. Therefore, we sought to assess the effects of two dominant shrub species (Artemisia aucheri and Prunus pseudoprostrata) on all biodiversity components including taxonomic, functional and phylogenetic diversity across some environmental gradients such as precipitation and soil gradients in rocky outcrops and their surrounding rangelands. Location: The study was conducted on six sites located in rocky outcrops and their surrounding rangelands across a precipitation gradient (160–910 mm) and under different soil fertility levels in northern Iran. Methods: We established 80 1‐m2 (1 m × 1 m) plots in each site with respect to the presence of nurse shrubs, and measured biodiversity components within the plots using Rao Q entropies (q0, q1 and q2) and mean pairwise distance (MPD) indices. The relative interaction index (RII) was also calculated to quantify the interaction type and intensity. Finally, variation partitioning analysis was performed to determine the relative importance of biotic interactions and abiotic factors such as precipitation, electrical conductivity (EC) and phosphorus on structuring biodiversity components. Results: Plant–plant interactions and abiotic factors consistently influenced different components of biodiversity in rocky outcrops and their surrounding rangelands. However, nurse shrubs showed stronger effects on plant biodiversity than abiotic factors by providing suitable microenvironments to harbor less‐tolerant plant species under the severe conditions of outcrops. In addition, microhabitats beneath nurse shrubs significantly responded to soil EC and precipitation gradients, with a decrease in competition intensity under intermediate levels of the gradients. In contrast, nurse shrubs negatively affected different components of biodiversity, with a decrease in biodiversity under intermediate levels of environmental gradients in surrounding rangelands. Conclusions: Our findings show critical roles of nurse shrubs for maintaining plant biodiversity in rocky outcrops depending on their growth form and the biodiversity component considered. In this case, nurse shrubs could reduce double environmental filtering, consistent with establishing a functional paradox trade‐off to support a wide range of plant species with functionally divergent relatedness. [ABSTRACT FROM AUTHOR]

Climate and soil factors induce substantial controls over plant biodiversity in stressful ecosystems. Despite of some studies on plant biodiversity in extreme ecosystems including rocky outcrops, simultaneous effects of climate and soil factors have rarely been studied on different facets of biodiversity including taxonomic and functional diversity in these ecosystems. In addition, we know little about plant biodiversity variations in such extreme ecosystems compared to natural environments. It seems that environmental factors acting in different spatial scales specifically influence some facets of plant biodiversity. Therefore, we studied changes in taxonomic and functional diversity along precipitation and soil gradients in both landscapes (i) rocky outcrops and (ii) their nearby rangeland sites in northeast of Iran. In this regard, we considered six sites across precipitation and soil gradients in each landscape, and established 90 1m2 quadrates in them (i.e. 15 quadrats in each site; 15 × 6 = 90 in each landscape). Then, taxonomic and functional diversity were measured using RaoQ index, FDis and CWM indices. Finally, we assessed impacts of precipitation and soil factors on biodiversity indices in both landscapes by performing regression models and variation partitioning procedure. The patterns of taxonomic diversity similarly showed nonlinear changes along the precipitation and soil factors in both landscapes (i.e. outcrop and rangeland). However, we found a more negative and significant trends of variation in functional diversity indices (except for CWMSLA) across precipitation and soil factors in outcrops than their surrounding rangelands. Variations of plant biodiversity were more explained by precipitation factors in surrounding rangelands, whereas soil factors including organic carbon had more consistent and significant effects on plant biodiversity in outcrops. Therefore, our results represent important impacts of soil factors in structuring plant biodiversity facets in stressful ecosystems. While, environmental factors acting in regional and broad scales such as precipitation generally shape vegetation and plant biodiversity patterns in natural ecosystems. We can conclude that rocky outcrops provide suitable microenvironments to present plant species with similar yields that are less able to be present in rangeland ecosystems. [ABSTRACT FROM AUTHOR]

Aims Species composition and diversity of the mountainous rangelands are results of interactions between environmental severities, heterogeneous topography and facilitative effects by nurse plants. This research was aimed to compare relative effects of these three environmental variables on the natural vegetation of a mountainous rangeland. For a more detailed understanding, effects of four different nurse species were separately compared on the various plant growth forms and on two community plant responses (diversity and abundance). Methods A mountainous semiarid rangeland was selected in Baharkish, Quchan, Northeast of Iran. Density and canopy cover of all plant species were recorded under the canopy of four different shrubs and in open areas, in north and south-facing aspects, and in a normal and a drought year. Shannon diversity, total abundance (% cover) and the abundance of different growth forms were used as criteria for assessing effects of the environmental variables. Data were arranged in a factorial combination and analyzed by three-way analysis of variance using a GLM analysis. Important Findings (i) Drought, aspect and canopy created niche differentiation: annual forbs and shrubs were more affected by drought, whereas geophytes and grasses were more responsive to slope aspects. Effects of drought and slope aspect were more profound on species diversity, whereas that of canopy facilitation was stronger on plant abundance. (ii) Canopy facilitation was dependent on severity of the abiotic factors and life history of interacting species. Canopy facilitation allowed for the persistence of only annual forbs, but it was disadvantaged during the drought year. Plant community responses to abiotic factors (slope and drought) were more dependent on the plant growth form, while responses to canopy facilitation were more dependent on the morphology and/or ecology of nurse shrubs. (iii) Effect of shrubs was dependent on their morphology and ecology: shrubs with larger canopy area and nitrogen fixation capability increased, but those with allelopathic effects or a dense canopy structure decreased the diversity of the understory species. [ABSTRACT FROM AUTHOR]

Livestock grazing is a major driver of ecosystem functions in drylands and would be expected to influence soil biota such as termites. We examined changes in soil chemistry and plant community composition on mounds constructed by the subterranean termiteAnacanthotermes ahngerianusalong a gradient in grazing intensity in an arid steppe in north-eastern Iran. The grazing gradient was represented by increasing distance from an area used by resting livestock, and plant and soil attributes measured within three adjacent microsites (termite mounds, non-mound controls, intervening annular zone surrounding the mounds). Values of soil EC; pH; exchangeable Ca, Mg, and Na; and total nitrogen and organic carbon were greatest in mound soils and declined from mounds to control microsites. Mounds were completely devoid of plants. Annular zones had three-times less cover than the control sites, but there were no differences in diversity or evenness. Electrical conductivity values were ten-times greater on mounds than controls close to resting sites, but the difference diminished rapidly with distance from resting sites. For all other soil and plant variables, differences between microsites were consistent across the grazing gradient. Increased grazing intensity was associated with increasing soil pH, EC and sand content, and reduced plant cover. Overall our study shows that the effects of termites on soil chemistry and plant cover varied little across the grazing gradient. Our results suggest that termite mounds may sustain their role as sites of enhanced soil nutrients under even high levels of grazing. [ABSTRACT FROM PUBLISHER]

The original article can be found online at https://doi.org/10.1038/s41598-022-13123-2. Correction to: I Scientific Reports i https://doi.org/10.1038/s41598-022-13123-2, published online 30 May 2022 The original version of this Article contained an error in Affiliation 3, which was incorrectly given as 'Herbarium of Nowshahr Botanical Garden, Research Center of Agriculture and Natural Resources of Mazandaran, Mazandaran, Iran'. [Extracted from the article]