Causes and consequences of exotic plant invasions

Photo by Tiffany Knight Why are some exotic plant species able to become dominant in a community while others remain minor constituents?
To date, research presents mixed and contradictory results of the relationship between phylogenetic novelty and invasiveness. We aim to resolve some of this variation with a synthetic approach that explicitly considers spatial scale, environmental gradients and stage of invasion. We conduct field experiments that examine multiple mechanisms of invasion and their interactions on exotic plant population dynamics. In addition, we are synthesizing the effects that natural enemy introductions have on the fitness and population dynamics of exotic weeds.

• Community assembly and macroecology of islands
• Role of functional traits in explaining highly invaded Hawaiian ecosystems
• Synthesis of biocontrol agent effects on focal and non-target plants

Pollination Ecology

Recent global reports such as the IPBES have documented that pollinators are declining in abundance and diversity at local, regional, and global spatial scales due to human changes to the landscapes. How will these pollinator declines change the structure of plant-pollinator interactions and the function of pollination?

We collect plant-pollinator network data and conduct pollination experiments in grassland ecosystems along elevation, latitudinal and land use gradients. We have developed collaborations in understudied regions of Europe that have high densities of traditionally managed meadows. We use hands-on summer schools to grow our database while training the next generation of pollination ecologists. We synthesize the causes and consequence of pollen limitation for plant species. We examine the history of science for this rapidly changing field of study.

• Plant-pollinator networks in European meadows
• History of the field of pollination ecology
• Meta-analysis of pollen limitation
• Changes in plant-pollinator networks across long time intervals
• Pollination in agro-ecosystems

Restoration of degraded habitats

Grassland and coastal ecosystems provide valuable ecosystem services, including large contributions to global biogeochemical cycles and flood mitigation. However, many of these ecosystems have become heavily degraded by human activities. We examine the effects of habitat size, shape, exotic plant invasions, and dispersal limitation on plant community assembly. We study how to best optimize our monitoring efforts to identify at-risk species and their threats. We study the responses of rare plant species to large-scale habitat restoration.

• Experimental restoration of grassland ecosystems
• How do we prioritize species for conservation?
• Restoration of coastal sand dunes

Climate Change

Present and future climate change is a major driver of change in world´s ecosystems. How will changes in temperature and precipitation influence plant demography and population dynamics and plant biodiversity?

We are synthesizing the state of our knowledge on how climate change effects plant populations using COMPADRE, a global database of plant matric models and in collaboration with the sAPROPROS working group. We are synthesizing the state of our knowledge on how climate change effects plant biodiversity using studies that experimentally manipulate temperature and precipitation. Further, we have initiated our own research to fill in gaps in our knowledge for certain plant species and regions of the world.

Projects:

• Effects of climate change on plant population dynamics and biodiversity
• Range limits and demography of Carpobrotus edulis
• Effects of climate change on plant demography in the Global Change Environmental Facility (GCEF)

Forest community dynamics

Forest ecosystems have economic and cultural value, and provide vital ecosystem services. The loss of forests in developing countries is a globally recognized environmental crisis. There is an urgent need to synthesize the state of our knowledge on patterns of tree species distributions and their threats.

We contribute to global efforts to understand the macroecological patterns of tree species, and assess the threat to these species. We collaborate with the Foundation for Ecological Security (FES) in India to identify important tree species, model their species distribution and assess threats to their populations by collecting demographic data.

• Global tree synthesis
• India tree distributions and demography

Prof. Tiffany Knight
Alexander von Humboldt Professorship Spatial Interaction Ecology
phone +49 341 9733198
fax +49 341 9739360
E-mail Tiffany.Knight@idiv.de

Kati Kietzmann
Assistant Spatial Interaction Ecology
phone +49 341 9733198
fax +49 341 9739360
E-mail Kati.Kietzmann@idiv.de

Nina Becker
Scientific Manager
phone +49 341 9733159
fax +49 341 9739360
E-mail Nina.Becker@idiv.de

Valentin Stefan
Scientific Programmer
phone +49 341 9733210
E-mail Valentin.Stefan@idiv.de

Dr. Dylan Craven
Research Officer - PostDoc
phone +49 341 9733117
E-mail Dylan.Craven@idiv.de

Sarah Passonneau
Research Officer for bibliometrics, bibliographic management and research in ecology
phone +49 341 9733231
E-mail Sarah.Passonneau@idiv.de

Dr. Lotte Korell
Research Officer - PostDoc
phone: +49 345 5585308
E-mail Lotte.Korell@ufz.de

Dr. Demetra Rakosy
Research Officer - PostDoc
E-mail demetra.rakosy@ufz.de

Dr. Jeroen Everaars
Research Officer
E-mail jeroen.everaars@ufz.de

Elena Motivans
Student Research Assistant
E-mail elena.motivans@idiv.de

Martin Andrzejak
Student Research Assistant

Members from Martin Luther University:

Dr. Joanne Bennett (on maternity leave)
Research Officer - PostDoc
phone +49 341 9733155
E-mail Joanne.Bennett@idiv.de

Index:

You could use our publication index for further requests.

2018 (4)

• Bialic-Murphy, L., Gaoue, O.G., Knight, T., (2018):
  Using Transfer Function Analysis to develop biologically and economically efficient restoration strategies
  Sci. Rep. 8 , art. 2094
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• Crandall, R.M., Knight, T.M., (2018):
  Role of multiple invasion mechanisms and their interaction in regulating the population dynamics of an exotic tree
  J. Appl. Ecol. 52 (2), 885 - 894
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• Pardini, E.A., Parsons, L. S., Ştefan, V., Knight, T.M., (2018):
  GLMM BACI environmental impact analysis shows coastal dune restoration reduces seed predation on an endangered plant
  Restor. Ecol.
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• Thompson, A.H., Knight, T.M., (2018):
  Exotic plant species receive adequate pollinator service despite variable integration into plant–pollinator networks
  Oecologia 187 (1), 135 - 142
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2017 (5)

• Crawford, K.M., Knight, T.M., (2017):
  Competition overwhelms the positive plant–soil feedback generated by an invasive plant
  Oecologia 183 (1), 211 - 220
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• Pardini, E.A., Patten, M.V., Knight, T.M., (2017):
  Effects of seed density and proximity to refuge habitat on seed predation rates for a rare and a common Lupinus species
  Am. J. Bot. 104 (3), 389 - 398
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• Schuler, M.S., Chase, J.M., Knight, T.M., (2017):
  Habitat patch size alters the importance of dispersal for species diversity in an experimental freshwater community
  Ecol. Evol. 7 (15), 5774 - 5783
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• Schuler, M.S., Chase, J.M., Knight, T.M., (2017):
  Habitat size modulates the influence of heterogeneity on species richness patterns in a model zooplankton community
  Ecology 98 (6), 1651 - 1659
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• Vitt, P., Knight, T.M., Schutzenhofer, M., Kleiman, W., Havens, K., Bittner, T., (2017):
  Experimental grazing and grass-specific herbicide application benefit rare forb recruitment
  Nat. Areas J. 37 (2), 161 - 169
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2016 (2)

• Bernardo, H.L., Albrecht, M.A., Knight, T.M., (2016):
  Increased drought frequency alters the optimal management strategy of an endangered plant
  Biol. Conserv. 203 , 243 - 251
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• Guthrie, S.G., Crandall, R.M., Knight, T.M., (2016):
  Fire indirectly benefits fitness in two invasive species
  Biol. Invasions 18 (5), 1265 - 1273
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2015

Crandall, R., and T.M. Knight (2015)
Positive frequency dependence undermines the success of
restoration using historical disturbance regimes. Ecology Letters 18: 883–891.

2013

Burkle, L.A., Marlin, J.C., and T.M. Knight (2013)
Plant-Pollinator Interactions over 120 Years: Loss of Species, Co-Occurrence and Function. Science 339: 1611-1615.

Powell, K.I., J.M. Chase, and T.M. Knight (2013)
Invasive plants have scale-dependent effects on biodiversity by altering the species-area relationship. Science 339: 316-318.

Burns, J.H., E.A. Pardini, M.R. Schutzenhofer, Y.A. Chung, K.J. Seidler, and T.M. Knight (2013)
Greater sexual reproduction contributes to differences in demography of invasive plants and their noninvasive relatives. Ecology 94: 995-1004.
 

Research Gate Profile Tiffany Knight