Invasive alien plants can severely impact ecosystem diversity and function. While the effects of individual species are often studied, interactions between multiple invasive species are less understood. This study examines how Asclepias syriaca and Solidago spp. (including Solidago gigantea and S. canadensis) influence taxonomic and functional diversity in sandy old-fields. The aims are to: (1) assess the individual and combined impacts of Asclepias and Solidago on resident plant diversity and (2) determine whether interactions between these species alter their effects on the invaded community.
Gödöllő Hills, Central Hungary.
I sampled 80 plots (2 m × 2 m) on sandy old-fields with varying levels of Asclepias and Solidago cover. Plant species cover was visually estimated, and trait data were obtained from databases. Species richness, community completeness, and community-weighted means (CWM) for plant traits, along with Rao functional diversity, were analyzed. Generalized linear and mixed models were used to evaluate the effect of invasive cover on resident diversity and traits, both with and without considering the invasives' traits in community indices.
While Asclepias had no significant effect, Solidago cover significantly reduced species richness and community completeness. When invasive species traits were excluded from the analysis, only the CWM and Rao's diversity of the bud bank index were significantly related to Solidago cover. Including the invasives' traits revealed that their trait values influenced community indices significantly. Asclepias and Solidago cover were negatively correlated, but did not alter each other's effects.
Solidago has a stronger negative impact on resident species richness than Asclepias, which appears neutral. Trait-based mechanisms underlying reduced species richness under Solidago dominance require further investigation. The lack of interaction between these invaders suggests their individual impacts dominate over potential synergies or antagonisms.
This study examined the impact of tephra fall on microsite conditions and plant–plant interaction networks, as well as the extent to which different nurse species groups with varying traits (evergreen and deciduous) influence the outcomes of microsite conditions and facilitated species composition.
Four shrublands located in Nahuel Huapi National Park, in Northern Patagonia, Argentina (41°11′55.34″ S, 71°19′43.07″ W).
We selected 10 woody species as nurse species: five evergreens and five deciduous species. We recorded the microsite conditions, species composition and total cover below nurse species and in open spaces during three consecutive years: two previous to tephra fall that differed in their rainfall and one after tephra fall. We determined the facilitated species with the relative interaction intensity in plants (RII) index, constructed facilitation networks and analysed the species composition below nurses and in open spaces. We experimentally determined the tephra effect on the emergence and survival of two emblematic tree species, the native Austrocedrus chilensis and the exotic conifer Pseudotsuga menziesii.
Our study detected significant changes in microsite conditions, species composition and relative abundance due to tephra fall. The characteristics of microsites were changed by tephra fall, homogenising the studied shrubland and consequently affecting the plant–plant interaction. The experimental results demonstrated that the factor influencing the emergence of the coniferous trees under investigation was the thickness of the tephra, rather than the seedling species or type of tephra.
Our findings provide insights into the patterns and mechanisms of facilitation networks in Patagonian shrublands. We found that networks were robust and, despite some decreases in facilitation interactions, the generalist network structure was resilient to microsite changes due to the tephra and contributed to community maintenance. Although tephra fall is a natural disturbance in the region, it is necessary to deepen the implications for the exotic pine invasion dynamics in future research.
Neltuma juliflora (formerly Prosopis juliflora) was introduced to Botswana's Kgalagadi District in the 1980s to combat desertification and bind sand dunes. The species has since spread to the adjacent Gantsi District, and it is currently a pervasive problem in several arid and semi-arid regions. However, studies on the ecological consequences of N. juliflora invasion in Botswana are scarce. We assessed vegetation community characteristics and soil variables in paired invaded and uninvaded plots to explore the impact of N. juliflora invasion.
Savanna rangeland, Gantsi District, Botswana.
We established 10 × 10 m pairwise plots of invaded (with N. juliflora; n = 20) and uninvaded (without N. julifora; n = 20) communities, and compared them in terms of vegetation characteristics (richness, density, diversity, composition and dominant native species) and soil properties (soil carbon, magnesium, potassium, phosphorous, calcium, sodium, pH, nitrogen and cation exchange capacity) and assessed an invasion index.
Invasion of N. juliflora was associated with a significantly lower total species richness (−19%), native species richness (−26%), forb species richness (−34% lower), total plant density (−22%), and native plant density (−29%), while grass species richness and density were unchanged. Diversity indices were lower in invaded plots considering all plant species, native plant species and forbs. Total nitrogen and cation exchange capacity were 36% and 40% higher in invaded plots, respectively.
Our results suggest that N. juliflora invasion is associated with lower native biodiversity and higher values for some soil chemical properties. As uninvaded plots had denser and taller stands of native tree species, maintaining and protecting native vegetation will likely help slow invasion. Further research is needed to understand ongoing impacts and quantify the effect of N. juliflora invasion on ecosystem carbon storage and biodiversity of non-plant taxa.
How high-altitude plant communities will respond to climate change is unclear as studies often investigate warming effects in isolation. We asked how a species-rich subalpine meadow community responds to the combination of warmer, drier conditions using experimental manipulations. Specifically, we quantified responses to climate manipulation using Hill diversity, Bray–Curtis dissimilarity and abundance change at community, functional group and individual species levels.
Subalpine meadow, Tasmania, Australia.
In an orthogonal design, we used open-top warming chambers and rainout shelters to simulate warm, drought and heatwave conditions. Responses of the plant community were assessed through estimates of species cover taken at peak biomass using an array of 400 contiguous 25 × 25 mm cells in fixed-position quadrats.
After 3 years of climatic manipulations, warmed plots were less diverse than their respective controls, whereas neither drought nor heatwave treatments influenced community diversity or composition. Community composition in warmed plots diverged substantially from controls, driven by a reduction in grass, moss and small rosette forb abundance and an increase in sedge abundance with warming, though species responses within functional groups varied. Furthermore, compositional changes caused by warming were most pronounced in drier conditions, indicating this system may be vulnerable to simultaneous changes in temperature and precipitation.
Experimental warming caused a marked shift in community composition of this subalpine meadow, with the greatest response to warming occurring in dry sites. Our results indicate a crucial role of local soil water availability in mediating global climate change impacts on subalpine plant communities.
How do tree canopy cover and soil nutrients shape the taxonomic, phylogenetic, and functional diversity of sub-Mediterranean grasslands?
Valdebezana's valley (Burgos, Northern Spain).
We measured 10 above- and belowground plant functional raits related to resource acquisition strategies and dispersal ability from four sub-Mediterranean grasslands dominated by species with different biogeographic origins (Eurosiberian vs. Mediterranean). Then, we estimated patterns in taxonomic composition and compared the levels of taxonomic, phylogenetic, and functional diversity indices among communities and estimated their phylogenetic and functional assembly patterns, together with the decoupled functional diversity. Additionally, we estimated the influence of tree canopy and soil nutrients in shaping such patterns.
Communities segregated according to their biogeographic origin (Eurosiberian vs. Mediterranean) along a soil resource gradient, matching the economics spectrum expectation. Taxonomic diversity differed significantly between biogeographic origins, but phylogenetic or functional diversity did not. Assembly patterns showed phylogenetic over-dispersion accompanied by functional clustering, with a significant effect of decoupling. Differences in taxonomic diversity were driven by edaphic factors, while canopy closure mainly influenced phylogenetic and functional patterns.
Sub-Mediterranean grasslands are highly rich in all facets of biodiversity (taxonomic, phylogenetic, and functional) and in assembly processes. In these habitats, local conditions may influence the structure and composition of herbaceous plant communities, highlighting the fragility of ecotones to environmental variations. Our results underline the need to develop proper management actions to preserve ecotone grassland communities; for instance, the creation of heterogeneous environments combining forest patches with open areas to maximize their biodiversity and functionality.
Alpine grasslands are affected by a range of global change drivers, including land-use change, climate warming and pollution. How these drivers interact and affect plant functional communities is poorly understood. We used plant functional traits to test the single and interactive effects of warming, nitrogen addition and grazing on alpine grassland communities and assessed the importance of intraspecific trait variation.
Alpine and sub-alpine grasslands in western Norway.
For three years, we applied global change treatments to test the effects of warming with nitrogen addition, and warming with grazing at an alpine and sub-alpine plant community. We measured six plant functional traits related to plant size and leaf economics, including intraspecific trait variation.
Our results show that warming and nitrogen addition shifted size-related traits in plant communities towards taller plants with larger leaves, and more strongly in the alpine than in the sub-alpine plant community. Warming also affected leaf economic traits, promoting faster traits in the alpine and slower traits in the sub-alpine plant community. Grazing shifted communities to faster leaves (grazing tolerant) in the sub-alpine community and slower leaves (grazing avoidance) in the alpine community. There were no interactive effects between the global change drivers. The relative contributions of species turnover and intraspecific trait variation to overall trait variation differed between origins of the two plant communities.
We show that these global change drivers shift alpine and sub-alpine plant communities in different directions, likely due to differences in resource availability. Our results support the need for site-specific management strategies in these systems.
The role of microclimate in influencing range limits and vegetation shifts, especially in topographically heterogeneous mountain ecosystems, has gained attention in recent years. However, disturbance by large animals and snow pressure complicate reliable year-round time series of microclimatic measurements near the soil surface, calling for more robust logger setups.
Swiss Alps.
We presented a novel, low-cost, and effective method to monitor above- and belowground microclimate in mountain environments year-round that withstands large animals and snow pressure and is suitable for remote areas. Specifically, we customized the widely used TOMST TMS-4 data loggers and tested their functionality and reliability in a factorial field experiment as well as in a regional-scale field study in heterogeneous mountain terrain.
We found that standard TMS-4 loggers were frequently destroyed by snow creep or snow pressure over winter, but customized loggers remained intact. In addition, camera-trap footage demonstrated that only customized loggers were efficiently protected against large mammals, such as wolves, foxes, red deer, and chamois. The customization of loggers had ecologically negligible effects on the recorded above- and belowground microclimate.
With this method, we enable combined monitoring of air, surface, and soil temperatures as well as soil moisture in alpine environments throughout the year, and thus the collection of crucial microclimatic variables for research in mountain ecosystems.
Rapid revegetation of burnt forest is essential for recovering ecosystem functioning, especially in the context of climate change–driven shifts in fire regime. This study aimed to provide a comprehensive understanding of how abiotic factors (topography, fire behaviour) and biotic factors (pre-fire forest characteristics, plant reproductive strategies, land-use trajectories) influence the recovery of Pinus halepensis forests, identifying regeneration vulnerabilities that could inform management practices.
A P. halepensis forest burnt in 2019 (4000 ha) in NE Iberian Peninsula.
We established 72 sampling sites within the burnt forest, covering gradients of pre-fire canopy cover (PCC), topography, fire severity and land-use history. At each site, we recorded the abundance of P. halepensis seedlings within a 100-m2 plot. We also conducted a floristic inventory of all associated woody species along two parallel 20-m transects to assess woody species cover, richness and distribution. Woody species were classified based on their post-fire reproductive strategies (obligate seeding, facultative resprouting and resprouting) to explore the relationship between functional characteristics and plant distribution along the studied gradients.
Northern exposures enhanced the abundance of P. halepensis, whereas coexisting woody species cover was higher on southern ones, probably due to the contribution of obligate seeders, as fire-responsive reproductive traits vary along the north–south gradient. PCC boosted pine regeneration and species richness, while high fire severity reduced both cover and richness of woody species, likely due to damage to reproductive structures.
We show that the drivers of post-fire regeneration influence in different and even divergent ways the vegetation components considered (canopy and shrub layer), as in the case of aspect. From a management perspective, post-fire forest interventions should be tailored to restoration objectives and to the post-fire vegetation communities that better respond to them.
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