Weed abundance is positively correlated with native plant diversity in grasslands of southern Australia

Published: June 1, 2017Weeds are commonly considered a threat to biodiversity, yet interactions between native and exotic species in grasslands are poorly understood and reported results vary depending on the spatial scale of study, the factors controlled for and the response variables analysed. We tested whether weed presence and abundance is related to declines in biodiversity in Australian grasslands. We employed existing field data from 241 plots along a disturbance gradient and correlated species richness, cover and Shannon diversity for natives and exot- ics, controlling for seasonal rainfall, climatic gradients and nutrient status. We found no neg- ative relationships in terms of emergent diversity metrics and occupation of space, indeed, many positive relationships were revealed. When split by land-use, differences were found along the disturbance gradient. In high-moderately disturbed grasslands associated with land-uses such as cropping and modified pastures, positive associations were enhanced. Tolerance and facilitation mechanisms may be involved, such as complementary roles through different life history strategies: the exotic flora was dominated mainly by annual grasses and herbs whereas the native flora represented more diverse growth-forms with a higher proportion of perennials. The positive relationships existing between native and exotic plant species in high-moderately disturbed grasslands of South Australia are most likely due to facilitation through different strategies in occupation of space given that the effect of habitat suitability was controlled for by including environmental and disturbance fac- tors. Consequently, although particular weeds may negatively impact biodiversity, this can- not be generalised and management focusing on general weed eradication in grasslands might be ineffectual.Irene Martín-Forés, Greg R. Guerin, Andrew J. Low

Service Learning Questionnaire

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Functional acclimation across microgeographic scales in Dodonaea viscosa

Intraspecific plant functional trait variation provides mechanistic insight into persistence and can infer population adaptive capacity. However, most studies explore intraspecific trait variation in systems where geographic and environmental distances co-vary. Such a design reduces the certainty of trait-environment associations, and it is imperative for studies that make trait-environment associations be conducted in systems where environmental distance varies independently of geographic distance. Here we explored trait variation in such a system, and aimed to: (i) quantify trait variation of parent and offspring generations, and associate this variation to parental environments; (ii) determine the traits which best explain population differences; (iii) compare parent and offspring trait-trait relationships. We characterized 15 plant functional traits in eight populations of a shrub with a maximum separation ca. 100 km. Populations differed markedly in aridity and elevation, and environmental distance varied independently of geographic distance. We measured traits in parent populations collected in the field, as well as their offspring reared in greenhouse conditions. Parent traits regularly associated with their environment. These associations were largely lost in the offspring generation, indicating considerable phenotypic plasticity. An ordination of parent traits showed clear structure with strong influence of leaf area, specific leaf area, stomatal traits, isotope δ¹³C and δ¹⁵N ratios, and Narea, whereas the offspring ordination was less structured. Parent trait-trait correlations were in line with expectations from the leaf economic spectrum. We show considerable trait plasticity in the woody shrub over microgeographic scales (<100 km), indicating it has the adaptive potential within a generation to functionally acclimate to a range of abiotic conditions. Since our study shrub is commonly used for restoration in southern Australia and local populations do not show strong genetic differentiation in functional traits, the potential risks of transferring seed across the broad environmental conditions are not likely to be a significant issue.Zdravko Baruch, Alice R. Jones, Kathryn E. Hill, Francesca A. McInerney, Colette Blyth, Stefan Caddy-Retalic, Matthew J. Christmas, Nicholas J. C. Gellie, Andrew J. Lowe, Irene Martin-Fores, Kristine E. Nielson and Martin F. Bree

Anthropocene, the challenge for "Homo sapiens" to set its own limits

The Anthropocene as a distinct geological era has been the subject of active discussion within the scientific community. This era includes the notion that Homo sapiens has had a large impact on global planetary processes. Here, we aim at connecting the notion and nature of the Anthropocene with the social-economic success and the unexpected or unplanned environmental impacts of the anthropogenic activity. Some of the main achievements along the history of humankind have been important developmental steps for many human civilisations but they have also had undesired results that we could not foresee, including the rise of greenhouse gases emissions, the shifts in the area of species distributions or the affection of all major biogeochemical cycles. Increasing human life expectancy and health has promoted an exponential population growth, which together with the increased environmental footprint per capita has pushed many core variables for Earth functioning (e.g. biodiversity, nitrogen cycle, climate change) out of their safety limits. We illustrate examples of many ecosystems that have collapsed around the world because we have crossed the limits of their sustainable exploitation. Paradoxically, it is humanity itself who is pushing the Planet to conditions in which our own survival will unlikely be possible. The reason behind such a strong ecological and functional impact on the Planet within a relatively short space of time is an unsustainable economic system based on the assumption that a perpetual economic growth is not only possible but also desirable. Our awakening should lie on a global framework aimed at changing our relationship with the Planet.El Antropoceno como era geológica diferenciada ha sido objeto de discusión activa dentro de la comunidad científica. Esta era incluye la noción de que Homo sapiens ha tenido un gran impacto en los procesos globales planetarios. Aquí intentamos conectar la noción y naturaleza del Antropoceno con el éxito socioeconómico y los impactos no esperados ni planificados de la actividad antropogénica. Algunos de los principales logros a lo largo de la historia de la humanidad han sido pasos importantes para muchas civilizaciones humanas, pero también han dado lugar a consecuencias indeseadas que no se podían prever, incluyendo el incremento de gases de efecto invernadero, los cambios en las áreas de distribución de especies o la afección a los grandes ciclos biogeoquímicos. El aumento de las expectativas de vida humana y la salud han promovido un incremento exponencial de la población, que junto con la mayor huella ambiental per capita han llevado a muchas variables esenciales para el funcionamiento de la Tierra (por ejemplo, la biodiversidad, el ciclo del nitrógeno, el cambio climático) fuera de sus límites de seguridad. Ponemos ejemplos de muchos ecosistemas que han colapsado en el mundo debido a que han cruzado los límites de su explotación sostenible. Paradójicamente, es la propia humanidad la que está empujando al Planeta hacia condiciones en las que su supervivencia no será posible. La razón que está detrás de este fuerte impacto ecológico y funcional en el Planeta en un plazo relativamente corto es un sistema económico insostenible basado en la asunción de que un crecimiento económico permanente es no solo posible sino también deseable. Nuestro despertar debería descansar en un marco global dirigido a cambiar nuestras relaciones con el Planeta

Which features at home make a plant prone to become invasive?

Determining the factors that pre-adapt plant species to successfully establish and spread outside of their native ranges constitutes a powerful approach with great potential for management. While this source-area approach accounts for the bias associated with species’ regions of origin, it has been only implemented in pools of species known to be established elsewhere. We argue that, in regions with well-known introduction histories, such as the Mediterranean Biome, the consideration of co-dominant non-introduced species as a control group allows a better understanding of the invasion process. For this purpose, we used occurrence data from GBIF and trait data from previous studies to find predictors of establishment and invasion. We compare the frequency, climatic niche and functional traits of 149 co-dominant plant species in their native region in southern Spain, considering whether they have colonised other Mediterranean-climate regions or not and their level of invasion. We found that large native ranges and diverse climatic niches were the best predictors of species establishment abroad. Moreover, coloniser species had longer bloom periods, higher growth rates and greater resource acquisition, whereas coloniser species becoming invasive had also greater reproductive height and nitrogen use efficiency. This framework has the potential to improve prediction models and management practices to prevent the harmful impacts from species in invaded communities.Javier Galán Díaz, Enrique G. de la Riva, Irene Martín-Forés, Montserrat Vil