Francine M.R. Hughes

Managing river flows to restore floodplain forests

River damming has dramatic environmental impacts and while changes due to reservoir flooding are immediate, downstream impacts are more spatially extensive. Downstream environments are influenced by the pattern of flow regulation, which also provides an opportunity for mitigation. We discuss impacts downstream from dams and recent case studies where collaborative efforts with dam operators have led to the recovery of more natural flow regimes. These restoration programs, in Nevada, USA, and Alberta, Canada, focused on the recovery of flow patterns during high flow years, because these are critical for riparian vegetation and sufficient water is available for both economic commitments and environmental needs. The restoration flows were developed using the “Recruitment Box Model”, which recommends high spring flows and then gradual flow decline for seedling survival. These flow regimes enabled extensive recruitment of cottonwoods and willows along previously impoverished reaches, and resulted in improvements to river and floodplain environments. Such restoration successes demonstrate how instream flow management can act as a broadly applicable tool for the restoration of floodplain forests.

Restoring Riparian Ecosystems: The Challenge of Accommodating Variability and Designing Restoration Trajectories

Flood disturbance processes play a key role in the functioning of riparian ecosystems and in the maintenance of biodiversity along river corridors. As a result, riparian ecosystems can be described as mobile habitat mosaics characterized by variability and unpredictability. Any river restoration initiative should aim to mimic these attributes. This paper suggests that there needs to be an increased institutional capacity to accept some levels of both variability and unpredictability in the ecological outcomes of river restoration projects. Restoration projects have frequently used some form of historical or contemporary reference system to define objectives and to help in the evaluation process. Using these reference systems can give a false sense of the predictability of ecological outcomes. We suggest that reference systems need to be used with caution for six reasons: (1) there are often no appropriate reference systems to use, (2) many catchment parameters have changed since the times of chosen historic reference systems, (3) climate change has been continuous throughout the Holocene, (4) projected climate change is of uncertain magnitude, (5) alien species cannot be avoided, and (6) landscape context changes through time. As well as defining short-term objectives, we suggest that river restoration projects should also formulate longer- term (decadel) restoration trajectories that are less predictable but more representative of real system attributes. Restoration trajectories could be defined using a range of ecological outcomes to accommodate interannual variability. The challenges of defining what levels of variability are important for restoring European floodplain forests are used to demonstrate the difficulties of broadening approaches and creating trajectories. In particular, the changing significance of variability at different spatial and temporal scales is discussed. An account is given of a restoration project at Wicken Fen in the United Kingdom in which nondeterministic approaches to goal setting have been initiated.

The influence of hydrological regimes on sex ratios and spatial segregation of the sexes in two dioecious riparian shrub species in northern Sweden

River management practices have altered the hydrological regimes of many rivers and also altered the availability of regeneration niches for riparian species. We investigated the impact of changed hydrological regimes on the sex ratios and the Spatial Segregation of the Sexes (SSS) in the dioecious species Salix myrsinifolia Salisb.–phylicifolia L. and S. lapponum L. by studying the free-flowing Vindel River and the regulated Ume River in northern Sweden. We surveyed sex ratios of these species in 12 river reaches on the Vindel River and in 17 reaches on the Ume River. In addition, we surveyed the sex and location above mean river stage of 1,002 individuals across both river systems to investigate the SSS of both species. Cuttings were collected from male and female individuals of S. myrsinifolia–phylicifolia from both rivers and subjected to four different water table regimes in a greenhouse experiment to investigate growth response between the sexes. We found an M/F sex ratio in both river systems similar to the regional norm of 0.62 for S. myrsinifolia–phylicifolia and of 0.42 for S. lapponum. We found no evidence of SSS in either the free-flowing Vindel River or the regulated Ume River. In the greenhouse experiment, hydrological regime had a significant effect on shoot and root dry weight and on root length. Significantly higher shoot dry weights were found in females than in males and significantly different shoot and root dry weights were found between cuttings taken from the two rivers. We concluded that changed hydrological regimes are likely to alter dimensions of the regeneration niche and therefore to influence sex ratios and SSS at an early successional stage, making it difficult to find clear spatial patterns once these species reach maturity and can be sexed.

Benefits and costs of ecological restoration: Rapid assessment of changing ecosystem service values at a U.K. wetland.

Restoration of degraded land is recognized by the international community as an important way of enhancing both biodiversity and ecosystem services, but more information is needed about its costs and benefits. In Cambridgeshire, U.K., a long-term initiative to convert drained, intensively farmed arable land to a wetland habitat mosaic is driven by a desire both to prevent biodiversity loss from the nationally important Wicken Fen National Nature Reserve (Wicken Fen NNR) and to increase the provision of ecosystem services. We evaluated the changes in ecosystem service delivery resulting from this land conversion, using a new Toolkit for Ecosystem Service Site-based Assessment (TESSA) to estimate biophysical and monetary values of ecosystem services provided by the restored wetland mosaic compared with the former arable land. Overall results suggest that restoration is associated with a net gain to society as a whole of

The challenges of integrating biodiversity and ecosystem services monitoring and evaluation at a landscape-scale wetland restoration project in the UK

199 ha−1y−1, for a one-off investment in restoration of

Restoring Floodplain Forests in Europe

2320 ha−1. Restoration has led to an estimated loss of arable production of

A comparison of created and ancient fenland using ground beetles as a measure of conservation value

2040 ha−1y−1, but estimated gains of

Quantifying Soil Hydrology to Explain the Development of Vegetation at an Ex-Arable Wetland Restoration Site

671 ha−1y−1 in nature-based recreation,

Ecophysiology of riparian cottonwoods: stream flow dependency, water relations and restoration†

120 ha−1y−1 from grazing,

TESSA: A toolkit for rapid assessment of ecosystem services at sites of biodiversity conservation importance

48 ha−1y−1 from flood protection, and a reduction in greenhouse gas (GHG) emissions worth an estimated