Adaptive cycles of floodplain vegetation response to flooding and drying

Thapa, Rajesh; Thoms, Martín; Parsons, Melissa; Reid, Michael

doi:10.5194/esurf-4-175-2016

Cited by 13 publications

(7 citation statements)

References 42 publications

(56 reference statements)

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“…The productivity response of vegetation within the Narran floodplain has previously been shown to have a distinct pattern consistent with an adaptive cycle (Thapa, Thoms, Parsons, ; Thapa, Thoms, Parsons, & Reid, ). The current study demonstrates that productivity responses for different vegetation community types are also consistent with an adaptive cycle.…”

Section: Discussionmentioning

confidence: 91%

“…Whether patterns in these responses can be considered as following distinct and repeated adaptive cycles and whether they can provide insight as to the sensitivity of floodplain plant communities to potential changes in state over the course of the adaptive cycle remain to be seen and are an obvious direction for future study (cf. Thapa, Thoms, Parsons, ; Thapa, Thoms, Parsons, ).…”

Section: Discussionmentioning

confidence: 99%

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Do adaptive cycles of floodplain vegetation response to inundation differ among vegetation communities?

Thapa

Thoms

Reid

et al. 2019

River Research & Apps

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Flooding is a key driver of floodplain vegetation productivity. Adaptive cycles provide a model for examining the productivity of floodplain vegetation communities in response to hydrology. Accordingly, floodplain inundation drives vegetation productivity responses through an adaptive cycle of wetting (exploitation phase), wet (conservation phase), drying (release phase), and dry (reorganization phase). We examined changes in the productivity of four floodplain vegetation communities (lignum, coolibah, grass, and poplar box) through the four phases of an adaptive cycle and explore the various strategies used by these vegetation communities to cope with variation in water availability. All four vegetation communities showed significant differences in productivity, as indicated by changes in the normalized difference vegetation index between the adaptive cycle phases. Differences were evident in the total area of vegetation that showed a productivity response, the quality or the vigour of the response, the trajectory of change overtime (i.e., towards higher or lower productivity), and the probability of change. Although the four vegetation communities exhibited response patterns in relation to flooding and drying that fit the adaptive cycle model, differences were evident in the timing of transitions between the four phases and the duration spent in those phases for each vegetation community. Poplar box and coolibah communities showed a higher productivity response during the drying or release phase. By comparison, the highest productivity response for the grassland and lignum shrubland was observed during the wetting or exploitation phase.Overall, the results showed that the four vegetation communities are sensitive to the degree of wetting at different phases in the adaptive cycle. Knowledge of floodplain vegetation response in each phase of an adaptive cycle will enable better management of floodplains, as management activities can be tailored to adaptive phase patterns associated with each community.

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Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Do adaptive cycles of floodplain vegetation response to inundation differ among vegetation communities?

Thapa

Thoms

Reid

et al. 2019

River Research & Apps

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“…Moreover, the rooting depth influences metal mobilisation/immobilisation and element specific uptake into the roots which also affects the transfer into the shoots (Chrzan, 2016;Overesch et al, 2007). Thapa et al (2016) also demonstrated a change in semi-arid Australian floodplain vegetation productivity in response to flooding and drying cycles; flooding brings nutrients which increases net primary productivity. These changes in vegetation productivity could also initiate structural changes in floodplain vegetation communities in natural and semi-natural ecosystems (Overesch et al, 2007).…”

Section: Plantsmentioning

confidence: 97%

The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil – A review

Ponting

Kelly

Verhoef

et al. 2021

Science of The Total Environment

104

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The frequency and duration of flooding events are increasing due to land-use changes increasing runoff of precipitation, and climate change causing more intense rainfall events. Floodplain soils situated downstream of urban or industrial catchments, which were traditionally considered a sink of potentially toxic elements (PTEs) arriving from the river reach, may now become a source of legacy pollution to the surrounding environment if PTEs are mobilised by unprecedented flooding events.When a soil floods, the mobility of PTEs can increase or decrease due to the net effect of five key processes; (i) the soil redox potential decreases which can directly alter the speciation, and hence mobility, of redox sensitive PTEs (e.g. Cr, As), (ii) pH increases which usually decreases the mobility of metal cations (e.g. Cd 2+ , Cu 2+ , Ni 2+ , Pb 2+ , Zn 2+ ), (iii) dissolved organic matter (DOM) increases, which chelates and mobilises PTEs, (iv) Fe and Mn hydroxides undergo reductive dissolution, releasing adsorbed and co-precipitated PTEs, and (v) sulphate is reduced and PTEs are immobilised due to precipitation of metal sulphides. These factors may be independent mechanisms, but they interact with one another to affect the mobility of PTEs, meaning the effect of flooding on PTE mobility is not easy to predict. Many of the processes involved in mobilising PTEs are microbially mediated, temperature dependent and the kinetics are poorly understood.Soil mineralogy and texture are properties that change spatially and will affect how the mobility of PTEs in a specific soil may be impacted by flooding. As a result, knowledge based on one river catchment may not be particularly useful for predicting the impacts of flooding at another site. This review provides a critical discussion of the mechanisms controlling the mobility of PTEs in floodplain soils. It summarises current understanding, identifies limitations to existing knowledge, and highlights requirements for further research.

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“…Heterogeneity is a feature of floodplain surfaces that influences diverse functional responses to flooding (Scown et al, 2016b). For example, floodplain inundation was shown by Thapa et al (2016;2020) to drive vegetation productivity responses through an adaptive cycle of wetting (r), wet (K), drying (Ω), and dry (α) phases. Adaptive cycles characterize a diversity of responses as a cycle comprised of four phases: exploitation (r), conservation (K), release (Ω), and renewal (α) (cf.…”

Section: Flow Chain Modelmentioning

confidence: 99%

Enhancing the functionality of environmental flows through an understanding of biophysical processes in the riverine landscape

Yarnell

Thoms

2022

Front. Environ. Sci.

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While water resource managers and river scientists recognize the inherent interconnections among hydrology, river structure, biophysical processes and ecological patterns, management of environmental flows still pays insufficient attention to the ecological and geomorphological functionality of particular aspects of the flow regime. Implementation of more natural flow regimes has improved habitat conditions for native species in many moderately impaired rivers but mimicking a natural flow regime in heavily modified riverine landscapes cannot be expected to yield successful ecological outcomes unless such flows trigger functional processes. For example, the restoration of peak flows may not regenerate habitats if the river is starved of sediment or if the river channel is highly confined. High biodiversity is supported when variable flow regimes interact with spatially variable (heterogeneous) river channel and floodplain forms. In contrast, as rivers become homogeneous, biodiversity decreases when these dynamic spatiotemporal interactions are limited by flow alterations, blocked by channel levees, or perturbed by sediment deficit or surplus. Thus, the design of a more natural environmental flow regime without consideration of the implications for sediment transport and implicit recognition of channel–floodplain geomorphology is likely to have limited success in river management and restoration. To enhance the functionality of environmental flows, considerations of physical, biogeochemical, and ecological processes and the inherent heterogeneity of the riverine landscape must be included. A Functional Flows approach enhances the benefits from limited environmental flow allocations by focusing on the ecological and geomorphological functionality of particular aspects of the flow regime, considering geomorphic context, and emphasizing spatiotemporal diversity at key locations in the riverscape, such as adjacent floodplains or tributary junctions. In this paper, we outline and illustrate the concept of Functional Flows using a flow-chain model and provide two case study examples from Australia and the United States, where improvements in channel habitat and reconnection with the floodplain help to achieve the desired functionality of environmental flows.

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Adaptive cycles of floodplain vegetation response to flooding and drying

Cited by 13 publications

References 42 publications

Do adaptive cycles of floodplain vegetation response to inundation differ among vegetation communities?

Do adaptive cycles of floodplain vegetation response to inundation differ among vegetation communities?

The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil – A review

Enhancing the functionality of environmental flows through an understanding of biophysical processes in the riverine landscape

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