An outcome-based model for predicting recovery pathways in restored ecosystems : The Recovery Cascade Model
- Authors: Robson, Belinda , Mitchell, Bradley , Chester, Edwin
- Date: 2011
- Type: Text , Journal article
- Relation: Ecological Engineering Vol. 37, no. 9 (2011), p. 1379-1386
- Full Text: false
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- Description: Restoration is increasingly the focus of ecosystem management. Few conceptual models exist for predicting the consequences of restoration, especially those that predict the stages of recovery following restoration. Existing models focus either on defining endpoints for recovery or on defining ecosystem processes, but often do not identify barriers to recovery or potential negative effects of restoration. We describe a conceptual model that identifies the outcomes of the recovery pathways following flow restoration in rivers: the Recovery Cascade Model. The model identifies six general aspects of recovery following restoration: physical ecosystem change; creation of, or improvement in habitat condition; reconnection of the restored area to adjacent ecosystems; recolonization of the restored area; resumption of ecological processes; re-establishment of biotic interactions and reproduction by colonists in the restored area. These aspects may occur in sequence, such that recovery is blocked by a single barrier. The model accommodates feedback loops and includes strong connections between physical processes and ecosystem processes, but also identifies factors that are important in achieving endpoints such as potential barriers to further recovery. Identification of barriers to recovery enables improved planning to maximise the positive effects of restoration. By focussing on outcomes, the model provides a planning tool for managers that can be adapted for different ecosystems and restoration methods and which can be used to identify the amenities that an ecosystem will deliver at different stages of recovery. Ecosystem recovery is as much about overcoming barriers as it is about restorative actions. © 2011 Elsevier B.V.
Disturbance and the role of refuges in mediterranean climate streams
- Authors: Robson, Belinda , Chester, Edwin , Mitchell, Bradley , Matthews, Ty
- Date: 2013
- Type: Text , Journal article
- Relation: Hydrobiologia Vol. 719, no. 1 (2013), p. 77-91
- Full Text: false
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- Description: Refuges protect plant and animal populations from disturbance. Knowledge of refuges from disturbance in mediterranean climate rivers (med-rivers) has increased the last decade. We review disturbance processes and their relationship to refuges in streams in mediterranean climate regions (med-regions). Med-river fauna show high endemicity and their populations are often exposed to disturbance; hence the critical importance of refuges during (both seasonal and supraseasonal) disturbances. Disturbance pressures are increasing in med-regions, in particular from climatic change, salinisation, sedimentation, water extraction, hydropower generation, supraseasonal drought, and wildfire. Med-rivers show annual cycles of constrained precipitation and predictable seasonal drying, causing the biota to depend on seasonal refuges, in particular, those that are spatially predictable. This creates a spatial and temporal mosaic of inundation that determines habitat extent and refuge function. Refuges of sufficient size and duration to maintain populations, such as perennially flowing reaches, sustain biodiversity and may harbour relict populations, particularly during increasing aridification, where little other suitable habitat remains in landscapes. Therefore, disturbances that threaten perennial flows potentially cascade disproportionately to reduce regional scale biodiversity in med-regions. Conservation approaches for med-river systems need to conserve both refuges and refuge connectivity, reduce the impact of anthropogenic disturbances and sustain predictable, seasonal flow patterns. © 2012 Springer Science+Business Media Dordrecht.
- Description: C1
Size and quantity of woody debris affects fish assemblages in a sediment-disturbed lowland river
- Authors: Howson, Travis , Robson, Belinda , Matthews, Ty , Mitchell, Bradley
- Date: 2012
- Type: Text , Journal article
- Relation: Ecological Engineering Vol. 40, no. (2012), p. 144-152
- Full Text: false
- Reviewed:
- Description: Responses by fish assemblages to individual restoration actions among a suite of channel modifications are not well understood. We investigated whether increasing woody debris abundance, without significant change to channel morphology, would increase native fish abundance and species richness in a sediment-disturbed river channel (Glenelg River, Victoria, Australia). We conducted a Before-After, Control-Impact design experiment at twelve locations containing either a high (n=6) or low (n=6) quantity of large woody debris (LWD). We added small woody debris (SWD) to half (n=6: 3 high, 3 low LWD densities) of the locations to increase woody debris complexity without the impacts on channel morphology associated with LWD manipulations. Fish species richness and abundance was quantified using electrofishing surveys before (4 sampling trips) and after (3 sampling trips) SWD addition. Fish species richness was not associated with high or low quantities of LWD or with types of woody debris (LWD or SWD). Addition of SWD altered fish assemblage composition but the effect depended on LWD quantity. SWD additions to locations with low LWD quantities increased abundance of two, wood-affiliated species: Philypnodon grandiceps and Gadopsis marmoratus. SWD additions to locations with high LWD quantities increased abundance of P. grandiceps and Galaxias olidus. Fish body size was important in detecting a response to added SWD because for two species, only certain size classes responded: adults of P. grandiceps (>50. mm TL) and juveniles of G. marmoratus (<123. mm TL). Fish assemblages responded positively to increased density of SWD through local increases in abundance, despite channel sedimentation. Unlike LWD, SWD is relatively cheap to place in rivers because it does not require heavy machinery and can be obtained without tree mortality. The use of SWD to assist in habitat restoration, especially for small species of native fish and juvenile fish, should be considered as a strategy in river restoration. © 2012.