Periodic Reporting for period 2 - ALIENIMPACTS (Predicting impacts of alien plant invasions on community diversity)
Okres sprawozdawczy: 2022-10-01 do 2024-03-31
The Anthropocene is defined by human-induced environmental change, including climate change, land use change and alien species invasions. These changes have sparked a global biodiversity crisis. Human introduction of species beyond their historical biogeographic boundaries is one of the defining characteristics of the Anthropocene. Over 13,000 alien plant species are naturalised worldwide with numbers growing year on year. Here is the conundrum: alien species introductions could augment local and regional biodiversity, increasing ecosystem stability and productivity. If this were true, alien invasions could ameliorate some of the negative effects of native species loss. However, alien species that have become invasive are themselves among the top threats to biodiversity and have already contributed to at least 1,215 species extinctions worldwide. So, we must ask, under what conditions, through what processes and in what ways does alien plant invasion affect plant community diversity?
The fundamental aim of ALIENIMPACTS is to develop an approach for accurately predicting impacts of alien plants on floristic diversity, and to identify the circumstances under which negative impacts will occur, using temperate grasslands as a model system.
Using temperate grasslands as a model system, ALIENIMPACTS will:
1. Characterise the cause-effect relationships (dose-response curves) associated with the principal causes and mechanisms of invasion impact, and how they vary depending on context.
2. Quantify the proportion of alien plant species that have higher ecological fitness than co-occurring native species, the magnitude of that fitness advantage, and how long it lasts.
3. Develop new models, and a modelling approach, to predict the establishment and abundance of invading plant species in a site, and the resulting impact on plant community diversity.
By achieving its three project objectives, ALIENIMPACTS will realise its fundamental aim of developing the capacity to predict the impact of alien plant invasions on plant diversity at a community-scale. The modelling framework will be applied to temperate grasslands in three continents, but adaptable to other systems. This predictive capacity – and associated identification of indicators of high-risk high-impact invasions – will support biosecurity and natural resource management, guide conservation policies and practice, and inform trade, transport and production at local, regional and global scales. Extensions of ALIENIMPACTS would enable the efficacy of possible mitigation and management actions, and their trade-offs, to be evaluated.
The fundamental aim of ALIENIMPACTS is to develop an approach for accurately predicting impacts of alien plants on floristic diversity, and to identify the circumstances under which negative impacts will occur, using temperate grasslands as a model system.
Using temperate grasslands as a model system, ALIENIMPACTS will:
1. Characterise the cause-effect relationships (dose-response curves) associated with the principal causes and mechanisms of invasion impact, and how they vary depending on context.
2. Quantify the proportion of alien plant species that have higher ecological fitness than co-occurring native species, the magnitude of that fitness advantage, and how long it lasts.
3. Develop new models, and a modelling approach, to predict the establishment and abundance of invading plant species in a site, and the resulting impact on plant community diversity.
By achieving its three project objectives, ALIENIMPACTS will realise its fundamental aim of developing the capacity to predict the impact of alien plant invasions on plant diversity at a community-scale. The modelling framework will be applied to temperate grasslands in three continents, but adaptable to other systems. This predictive capacity – and associated identification of indicators of high-risk high-impact invasions – will support biosecurity and natural resource management, guide conservation policies and practice, and inform trade, transport and production at local, regional and global scales. Extensions of ALIENIMPACTS would enable the efficacy of possible mitigation and management actions, and their trade-offs, to be evaluated.
Work has progressed on all five work packages.
WP1.1 focuses on a seed addition experiment that I established in 2012. As part of the experimental design, I have continued to disturb and add seeds of invaders to some of the plots, and this treatment was repeated in autumn 2021 as planned (disturbance by tilling and mowing, and seed addition of up to 18 species at two different seeding rates into a selection of 168 plots). This treatment, and the survey conducted in summer of 2021, were successfully implemented. One paper has been published from this experiment, and two papers are in draft form.
WP1.2 features on a 30-year old seed addition experiment where 50 species were added. As planned, this experiment was surveyed in summer 2022, with initial data analysis underway.
WP1.3 involves establishment of a new field experiment to quantify impacts of plant invaders released from natural enemies by experimentally reducing insect and fungal attack on sown invaders. Two surveys have been conducted and key insights already gained. A journal paper is under revision and conference talks have been given.
For WP1.5 an extended synthesis on the enemy release hypothesis has been accepted by the journal Ecology Letters, one of the premier journals in ecology. This synthesis develops a new framework for the study of the enemy release hypothesis. A further manuscript based on old field data described in WP5.2 is undergoing revision.
WP2 uses time-series data from a globally replicated grassland experiment, the Nutrient Network or NutNet (nutnet.org) to disentangle impacts of invasion from impacts of other forms of global change. Good progress has been made towards WP2, with a conceptual framework prepared, hypotheses articulated, and preliminary results completed following a dedicated workshop and field sampling. Two draft manuscripts have been prepared. We have found that native species diversity is declining and alien plant abundance increasing. These trends are heightened in plots with added nitrogen, phosphorous and potassium compared with control plots.
WP3 uses observational global demographic and functional trait data to determine whether alien plants i) have higher “ecological fitness” than their native counterparts; and ii) have experienced an increase in fitness on movement to a new range or whether the observed fitness advantages are inherent. Substantive work has been undertaken on WP3, including preparation of a draft manuscript for journal submission. we have found that invasive alien species have higher demographic rates than native species.
WP4 is developing theoretical models of invasion impacts on plant diversity. The first set of models incorporate niche pre-emption and are being tested against data from Cedar Creek experiments. These models show that predictions are more robust when niche pre-emption is considered, and niche pre-emption can both help and hinder invasion depending on the situation.
For WP5, a mechanistic model has been developed that predicts the establishment and abundance of invading plant species in a site, and can be used to predict impacts on community diversity (WP5.1). The model has been parameterised using grassland data from Cedar Creek Ecosystem Science Reserve in the USA, and initially tested against two grassland experiments that have run for up to 28 years. This work demonstrates that we can accurately predict community dynamics and that multiple mechanisms are involved in species coexistence, including competition, dispersal and nice differentiation. Two manuscripts have been drafted and conference presentations given.
WP1.1 focuses on a seed addition experiment that I established in 2012. As part of the experimental design, I have continued to disturb and add seeds of invaders to some of the plots, and this treatment was repeated in autumn 2021 as planned (disturbance by tilling and mowing, and seed addition of up to 18 species at two different seeding rates into a selection of 168 plots). This treatment, and the survey conducted in summer of 2021, were successfully implemented. One paper has been published from this experiment, and two papers are in draft form.
WP1.2 features on a 30-year old seed addition experiment where 50 species were added. As planned, this experiment was surveyed in summer 2022, with initial data analysis underway.
WP1.3 involves establishment of a new field experiment to quantify impacts of plant invaders released from natural enemies by experimentally reducing insect and fungal attack on sown invaders. Two surveys have been conducted and key insights already gained. A journal paper is under revision and conference talks have been given.
For WP1.5 an extended synthesis on the enemy release hypothesis has been accepted by the journal Ecology Letters, one of the premier journals in ecology. This synthesis develops a new framework for the study of the enemy release hypothesis. A further manuscript based on old field data described in WP5.2 is undergoing revision.
WP2 uses time-series data from a globally replicated grassland experiment, the Nutrient Network or NutNet (nutnet.org) to disentangle impacts of invasion from impacts of other forms of global change. Good progress has been made towards WP2, with a conceptual framework prepared, hypotheses articulated, and preliminary results completed following a dedicated workshop and field sampling. Two draft manuscripts have been prepared. We have found that native species diversity is declining and alien plant abundance increasing. These trends are heightened in plots with added nitrogen, phosphorous and potassium compared with control plots.
WP3 uses observational global demographic and functional trait data to determine whether alien plants i) have higher “ecological fitness” than their native counterparts; and ii) have experienced an increase in fitness on movement to a new range or whether the observed fitness advantages are inherent. Substantive work has been undertaken on WP3, including preparation of a draft manuscript for journal submission. we have found that invasive alien species have higher demographic rates than native species.
WP4 is developing theoretical models of invasion impacts on plant diversity. The first set of models incorporate niche pre-emption and are being tested against data from Cedar Creek experiments. These models show that predictions are more robust when niche pre-emption is considered, and niche pre-emption can both help and hinder invasion depending on the situation.
For WP5, a mechanistic model has been developed that predicts the establishment and abundance of invading plant species in a site, and can be used to predict impacts on community diversity (WP5.1). The model has been parameterised using grassland data from Cedar Creek Ecosystem Science Reserve in the USA, and initially tested against two grassland experiments that have run for up to 28 years. This work demonstrates that we can accurately predict community dynamics and that multiple mechanisms are involved in species coexistence, including competition, dispersal and nice differentiation. Two manuscripts have been drafted and conference presentations given.
ALIENIMPACTS will mark a step-change from current state-of-the-art research in invasion science and global change biology by combining empirical and theoretical approaches to focus on the processes underlying diversity impacts of plant invasion. The tight integration of targeted field experiments, global observations, development of fundamental theory and mechanistic modelling in ALIENIMPACTS offers a unique, powerful and innovative way to quantify, characterise and predict the impacts of alien invasions on plant community diversity. ALIENIMPACTS will develop a modelling framework for predicting the impact of plant invasions on floristic diversity – applied to temperate grasslands in three continents, but adaptable to other systems. This predictive capacity – and associated identification of indicators of high risk high-impact invasions – will support biosecurity and natural resource management, guide conservation policies and practice, and inform trade, transport and production at local, regional and global scales. Extensions of ALIENIMPACTS would enable the efficacy of possible mitigation and management actions, and their trade-offs, to be evaluated.