Extreme climate events such as floods and droughts represent major threats
to biological diversity, agricultural production and livelihoods. Extreme climate
events are of greater magnitude over shorter duration than incremental
climate means and are expected to increase in frequency, duration and
intensity in response to climate change.
Wetlands such as floodplain grasslands provide ecologically diverse and
economically productive habitats. Extreme climate events are most likely to
affect floodplains through any sudden changes in hydrological regime.
However, floodplain plant communities are adapted to regular disturbance
from flooding and management, and species carry traits to deal specifically
with disturbance regimes unique to floodplains. Floodplains can be utilised as
a template to gain insight into wetland responses to climate change.
This research aimed to determine the responses of floodplain grassland plants
to extreme climate events, specifically hydrological change, by evaluating
the responses of repeated extreme flooding on survival, growth and flowering;
to ascertain whether different resilience strategies support plants in flooding
stress; and to investigate how sustained hydrological change affects plants
immediately and over time. Characteristic species from floodplain grasslands
were used in mesocosm experiments and field studies. The mesocosm
experiments used a repeated flooding scenario, mimicking a real-world
extreme flooding event. The field site consisted of two contrasting floodplain
grassland communities and hydrologies, and was utilised in a transplant
The key results from both mesocosm and field experiments suggest that
acknowledged species’ tolerances to saturated soils, such as the Ellenberg
Indicator Values, do not predict actual responses to differing frequencies and
durations of flooding. Initial responses to short-term and infrequent flooding
may differ from longer-term responses. Flooding frequency is as important as
flooding duration in determining species’ ability to ameliorate the
consequences of flooding. Results also indicate that, in general, flooding
advances flowering across a range of floodplain species, while flowering
abundance reduces as flooding duration increases. The resilience strategy of
plant-to-plant facilitation specifically fosters elongation of leaves and stems,
attributes that enhance plant survival of flooding events.
Floodplain grassland plant responses to extreme climate events are variable
and dependent on the nature of the event. Longer-term stability may be
determined by the frequency and duration of extreme events in conjunction
with community composition. Results from this research are important, as they
are extendable to gauging wider implications for other wetland communities
to extreme climate events.
|Date of Award||Jul 2017|