Responses of floodplain grassland plants to extreme climate events: survival, growth and flowering

Abstract

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 experiment. 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
Original language	English
Awarding Institution	University of Brighton