Timing of Arrival and Native Biomass Are Better Proxies of Invasion Suppression in Grassland Communities

A challenge in many restoration projects, in particular when establishing de novo communities, is the arrival and later dominance of invasive alien plants. This could potentially be avoided by designing invasion-resistant native communities. Several studies suggest achieving this by maximizing trait similarity between natives and potential invaders (“limiting similarity”), but evidence supporting this approach is mixed so far. Others pose that the relative time of arrival by native and invasive species (“priority effects”) could play a stronger role, yet this factor and its interaction with trait similarity is not fully understood in the context of ecological restoration. Thus, we hypothesized that multi-trait similarity would increase suppression of invasive species by native communities, and that the effect would be stronger when natives arrive first. We established two distinct communities of native central European grassland species based on native–invasive trait similarity, and then tested the introduction of invasive Ambrosia artemisiifolia and Solidago gigantea separately when arriving in the native communities at two times, i.e., sown either at the same time as the natives or 2 weeks after. For the traits selected, our data did not provide evidence for a limiting similarity effect, but rather supported priority effects. Both native communities more effectively suppressed invaders that arrived after the natives. In addition, the native community that produced the most biomass suppressed both invasive species more than the most ecologically similar community. This effect of biomass revealed that prioritizing native–invader ecological similarity can fail to account for other community characteristics that affect invasion resistance, such as biomass. Instead, native communities could be designed to enhance priority effects through the inclusion of early and fast developing species. We conclude that native community composition plays a significant role in the establishment success by invasive species, and resource pre-emption seems more significant than trait similarity. In terms of grassland restoration, native species should be selected based on plant traits related to fast emergence and early competitiveness

Fifteen emerging challenges and opportunities for vegetation science: A horizon scan by early career researchers

With the aim to identify future challenges and opportunities in vegetation science, we brought together a group of 22 early career vegetation scientists from diverse backgrounds to perform a horizon scan. In this contribution, we present a selection of 15 topics that were ranked by participants as the most emergent and impactful for vegetation science in the face of global change. We highlight methodological tools that we expect will play a critical role in resolving emerging issues by providing ways to unveil new aspects of plant community dynamics and structure. These tools include next generation sequencing, plant spectral imaging, process-based species distribution models, resurveying studies and permanent plots. Further, we stress the need to integrate long-term monitoring, the study of novel ecosystems, below-ground traits, pollination interactions and global networks of near-surface microclimate data at fine spatio-temporal resolutions to fully understand and predict the impacts of climate change on vegetation dynamics. We also emphasize the need to integrate traditional forms of knowledge and a diversity of stakeholders into research, teaching, management and policy-making to advance the field of vegetation science. The conclusions reached by this horizon scan naturally reflect the background, expertise and interests of a representative pool of early career vegetation scientists, which should serve as basis for future developments in the field

Fifteen emerging challenges and opportunities for vegetation science: A horizon scan by early career researchers

With the aim to identify future challenges and opportunities in vegetation science, we brought together a group of 22 early career vegetation scientists from diverse backgrounds to perform a horizon scan. In this contribution, we present a selection of 15 topics that were ranked by participants as the most emergent and impactful for vegetation science in the face of global change. We highlight methodological tools that we expect will play a critical role in resolving emerging issues by providing ways to unveil new aspects of plant community dynamics and structure. These tools include next generation sequencing, plant spectral imaging, process-based species distribution models, resurveying studies and permanent plots. Further, we stress the need to integrate long-term monitoring, the study of novel ecosystems, below-ground traits, pollination interactions and global networks of near-surface microclimate data at fine spatio-temporal resolutions to fully understand and predict the impacts of climate change on vegetation dynamics. We also emphasize the need to integrate traditional forms of knowledge and a diversity of stakeholders into research, teaching, management and policy-making to advance the field of vegetation science. The conclusions reached by this horizon scan naturally reflect the background, expertise and interests of a representative pool of early career vegetation scientists, which should serve as basis for future developments in the field

Functional diversity and invasive species influence soil fertility in experimental grasslands

Ecosystem properties can be positively affected by plant functional diversity and compromised by invasive alien plants. We performed a community assembly study in mesocosms manipulating different functional diversity levels for native grassland plants (communities composed by 1, 2 or 3 functional groups) to test if functional dispersion could constrain the impacts of an invasive alien plant (Solidago gigantea) on soil fertility and plant community biomass via complementarity. Response variables were soil nutrients, soil water nutrients and aboveground biomass. We applied linear mixed-effects models to assess the effects of functional diversity and S. gigantea on plant biomass, soil and soil water nutrients. A structural equation model was used to evaluate if functional diversity and invasive plants affect soil fertility directly or indirectly via plant biomass and soil pH. Invaded communities had greater total biomass but less native plant biomass than uninvaded ones. While functional diversity increased nutrient availability in the soil solution of uninvaded communities, invasive plants reduced nutrient concentration in invaded soils. Functional diversity indirectly affected soil water but not soil nutrients via plant biomass, whereas the invader reduced native plant biomass and disrupted the effects of diversity on nutrients. Moreover, invasive plants reduced soil pH and compromised phosphate uptake by plants, which can contribute to higher phosphate availability and its possible accumulation in invaded soils. We found little evidence for functional diversity to constrain invasion impacts on nutrients and plant biomass. Restoration of such systems should consider other plant community features than plant trait diversity to reduce establishment of invasive plants.publishedVersio

Moving Away From Limiting Similarity During Restoration: Timing of Arrival and Native Biomass Are Better Proxies of Invasion Suppression in Grassland Communities

A challenge in many restoration projects, in particular when establishing de novo communities, is the arrival and later dominance of invasive alien plants. This could potentially be avoided by designing invasion-resistant native communities. Several studies suggest achieving this by maximizing trait similarity between natives and potential invaders (“limiting similarity”), but evidence supporting this approach is mixed so far. Others pose that the relative time of arrival by native and invasive species (“priority effects”) could play a stronger role, yet this factor and its interaction with trait similarity is not fully understood in the context of ecological restoration. Thus, we hypothesized that multi-trait similarity would increase suppression of invasive species by native communities, and that the effect would be stronger when natives arrive first. We established two distinct communities of native central European grassland species based on native–invasive trait similarity, and then tested the introduction of invasive Ambrosia artemisiifolia and Solidago gigantea separately when arriving in the native communities at two times, i.e., sown either at the same time as the natives or 2 weeks after. For the traits selected, our data did not provide evidence for a limiting similarity effect, but rather supported priority effects. Both native communities more effectively suppressed invaders that arrived after the natives. In addition, the native community that produced the most biomass suppressed both invasive species more than the most ecologically similar community. This effect of biomass revealed that prioritizing native–invader ecological similarity can fail to account for other community characteristics that affect invasion resistance, such as biomass. Instead, native communities could be designed to enhance priority effects through the inclusion of early and fast developing species. We conclude that native community composition plays a significant role in the establishment success by invasive species, and resource pre-emption seems more significant than trait similarity. In terms of grassland restoration, native species should be selected based on plant traits related to fast emergence and early competitiveness

Indicators of landscape organization and functionality in semi-arid former agricultural lands under a passive restoration management over two periods of abandonment

Abandoned lands previously used for agricultural purposes may constitute an opportunity for understandingthe variables involved in the restoration of native ecosystems over time. In this study, weassessed the functional status of an abandoned farmland currently used for conservation, using a methodologybased on indicators of landscape organization and soil surface. We analyzed changes in plant cover,patch and interpatches structure and several soil surface properties during two periods of land abandonment(less and more than 40 years). Using this methodology, we characterize the potential of theecosystem to capture and transfer resources, and the state of functional properties such as infiltrationcapacity, soil stability and nutrient cycling.We detected a significant development of the shrub layer and an increase of the number, type andarea occupied by vegetated patches in old fields. The contribution of vegetated patches to the recovery ofstability, infiltration and nutrient functions was significant at the local scale. Nonetheless, when analyzingthe landscape as a whole only the nutrient cycling index was significantly higher in old fields. The lackof improvement of the stability and infiltration in old fields can lead to further degradation and indicatesthat even though vegetation cover may have improved over time in old fields, the current cover mightnot be enough to prevent further degradation by erosion. Our results reinforce the importance of usingfunctionality indexes in future studies focused on adequate restoration measures to protect the functionof desert ecosystems, especially when aimed for biodiversity conservation. Hence, the use of monitoringsystems based on organization and function indicators is a useful tool to represent the current state andpotential recovery of previously disturbed ecosystems, provided that the time scale is taken into account.Fil: Tabeni, Maria Solana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Yannelli, Florencia A.. Technische Universität München. Chair of Restoration Ecology; AlemaniaFil: Vezzani, Nazareth. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias; ArgentinaFil: Mastrantonio, Leandro Eloy. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias; Argentin

Data from: Importance of soil legacy effects and successful mutualistic interactions during Australian acacia invasions in nutrient poor environments

Non-native plants often alter environments they invade, favouring their own performance through positive feedbacks. Plant-soil interactions represent one such mechanism, but their complexity (e.g. invader-induced changes in soil nutrients, microbial communities, etc.) makes inferences of the precise mechanisms that benefit invaders difficult. Here we aimed to determine: 1) whether invasion by Australian acacias (genus Acacia L.) changes nitrogen-fixing soil microbial community diversity and structure, and 2) the importance of available rhizobial partners and overall invader-induced soil changes as significant facilitators of acacia performance. We sampled soils from various invaded and nearby uninvaded areas in South Africa’s Core Cape Subregion and, using next generation sequencing data, compared nitrogen-fixing soil microbial communities between invaded and univaded soils. We then determined the relative importance of soil status (invaded vs. uninvaded), in conjunction with the rhizobial addition, to the performance of invasive acacias under common garden conditions. Next generation sequencing data revealed that invaded soils generally harboured lower nitrogen-fixing microbial diversity and were compositionally more homogenous, compared to uninvaded soils. Bradyrhizobium strains, the most common known rhizobial associate of acacias, were more abundant in invaded than uninvaded sites. Our greenhouse experiments found significantly reduced growth performances of acacias in uninvaded relative to invaded soils for most species by site comparisons, and almost no influence of additional rhizobial inoculum However, the overall relationship between nodulation and growth kinetics was much steeper for plants grown in uninvaded soils compared to invaded soils. Despite invasive acacias homogenising nitrogen-fixing microbial community composition and reducing diversity, it appears that mutualist availability poses no significant barrier to acacia establishment. Although acacia-induced changes to soil conditions enhance plant performance, our successful nodulation seems important to early growth performance of acacias when encountering novel soil conditions. We provide evidence that invasions by Australian acacias affect the diversity and structure of soil rhizobial communities. Although overall soil changes benefit their performance independent of rhizobia addition, forming successful mutualistic interactions is critical during the establishment phase under novel environmental conditions. Taken together, our results indicate that interactions between soil abiotic and biotic conditions work in concert to enhance invader performance though positive feedbacks

Recent Anthropogenic Plant Extinctions Differ in Biodiversity Hotspots and Coldspots

International audienceDuring the Anthropocene, humans are changing the Earth system in ways that will be detectable for millennia to come [1]. Biologically, these changes include habitat destruction, biotic homogenization, increased species invasions, and accelerated extinctions [2]. Contemporary extinction rates far surpass background rates [3], but they seem remarkably low in plants [4, 5]. However, biodiversity is not evenly distributed, and as a result, extinction rates may vary among regions. Some authors have contentiously argued that novel anthropic habitats and human-induced plant speciation can actually increase regional biodiversity [6, 7]. Here, we report on one of the most comprehensive datasets to date, including regional and global plant extinctions in both biodiversity hotspots (mostly from Mediterra-nean-type climate regions) and coldspots (mostly from Eurasian countries). Our data come from regions covering 15.3% of the Earth's surface and span over 300 years. With this dataset, we explore the trends, causes, and temporal dynamics of recent plant extinctions. We found more, and faster accrual of, absolute numbers of extinction events in biodiversity hotspots compared to coldspots. Extinction rates were also substantially higher than historical background rates, but recent declines are evident. We found higher levels of taxonomic uniqueness being lost in biodiversity coldspots compared to hot-spots. Causes of plant extinctions also showed distinct temporal patterns, with agriculture, invasions , and urbanization being significant drivers in hotspots, while hydrological disturbance was an important driver in coldspots. Overall, plant extinctions over the last three centuries appear to be low, with a recent (post-1990) and steady extinction rate of 1.26 extinctions/year

Fifteen emerging challenges and opportunities for vegetation science - A horizon scan by early career researchers

With the aim to identify future challenges and opportuni-ties in vegetation science, we brought together a group of 22 early career vegetation scientists from diverse back-grounds to perform a horizon scan. In this contribution, we present a selection of 15 topics that were ranked by participants as the most emergent and impactful for vegetation science in the face of global change. We highlight methodological tools that we expect will play a critical role in resolving emerging issues by providing ways to unveil new aspects of plant community dynam-ics and structure. These tools include next generation se-quencing, plant spectral imaging, process- based species distribution models, resurveying studies and permanent plots. Further, we stress the need to integrate long-term monitoring, the study of novel ecosystems, below- ground traits, pollination interactions and global networks of near-surface microclimate data at fine spatio-temporal resolutions to fully understand and predict the impacts of climate change on vegetation dynamics. We also empha-size the need to integrate traditional forms of knowledge and a diversity of stakeholders into research, teaching, management and policy- making to advance the field of vegetation science. The conclusions reached by this hori-zon scan naturally reflect the background, expertise and interests of a representative pool of early career vegeta-tion scientists, which should serve as basis for future de-velopments in the fiel