Adding large woody material into a headwater stream has immediate benefits for macroinvertebrate community structure and function

Abstract

Hydromorphological rehabilitation through installing large woody material (LWM) is increasingly being used to reverse degradation of stream ecosystems. There have been many criticisms of stream rehabilitation projects, because many have not met their goals and many others have not been monitored well enough to assess whether their goals were met. In a before–after–control design (with samples collected 1 year before and two successive years after LWM installation), instream biotopes and their macroinvertebrate assemblages were used as structural and functional units to assess the effectiveness of LWM installed at the Rolleston Brook, a headwater tributary of the River Welland in Leicestershire, UK. The project was successful in enhancing the coefficient of variation of channel water depth and width, wetted surface area, number of instream biotopes, and the biotope diversity in the rehabilitated reach. LWM installation led to significant increases in macroinvertebrate total density, total biomass, and taxon richness. Macroinvertebrate community composition was also enhanced, so that it became more similar to that of the control reach. Small increases in the number of instream biotopes (appearance of gravel and leaf litter) and changes in biotope proportions (decreasing percentage of silt) were significantly related to changes in the macroinvertebrate community metrics in the rehabilitated reach. The results show that using macroinvertebrate community composition is more effective than only using taxon richness and/or diversity metrics for understanding the relationship between LWM installation and macroinvertebrate community responses. To be effective, samples must also be collected in a predefined sampling protocol stratified at the instream biotope level. This approach would be of great benefit in evaluating biodiversity conservation value, and could be incorporated into the advice provided by Natural England concerning restoration and protection of English rivers that are designated as Sites of Special Scientific Interest under UK legislation or Special Areas of Conservation under European legislation.

Hydromorphological rehabilitation improves channel morphology, instream biotopes, and macroinvertebrate communities, and thus enhances the conservation of an urban river

“…They have recently been shown, on a smaller scale, to be an effective measure of restoration of large woody material in a lowland stream (Al-Zankana, Matheson & Harper, 2021).…”

“…Rehabilitation projects – particularly in the UK – have generally focused on relatively large physical units: for example, by installing large woody material to act as flow deflectors, by constructing riffle areas, or by widening reaches to reinstate multichannel planforms (e.g. Biggs et al, 1998; Harrison et al, 2004; Pretty & Dobson, 2004; Smith & Chadwick, 2014; Thompson, 2015; White et al, 2017; Al‐Zankana, Matheson & Harper, 2021).…”

“…A subsequent reanalysis of the full set of original data from 10 UK rivers, used to identify functional habitats (Demars et al, 2012), renamed, with ecological justification, these river microhabitat units as ‘biotopes’. They have recently been shown, on a smaller scale, to be an effective measure of restoration of large woody material in a lowland stream (Al‐Zankana, Matheson & Harper, 2021).…”

Numerical Modeling of Potential Large Wood Entrainment in Rivers: Application of Hybrid Modeling in the Inter‐Dam Reach of the Dyje River, Czechia

“…The flux of large wood in drainage networks (LW, i.e., the pieces with a minimum diameter and length of 0.1 and 1 m, respectively; Wohl et al., 2010; Máčka et al., 2011) has become a research focus in the past two decades (Wohl et al., 2023). While the benefits of stable in‐channel LW for ecological and geomorphic functioning of fluvial systems were greatly appreciated (e.g., Al‐Zankana et al., 2021; Andreoli et al., 2007; Melina & Hinch, 2009), LW may account for a hazardous factor augmenting flood risk and endangering river infrastructures such as bridges, weirs, and reservoir dams (Mazzorana et al., 2018; Wohl et al., 2016). LW accumulations may intensify the adverse effects of floods by clogging the channel, raising water upstream, diverting flow, and enhancing the scour of channel bed and banks (e.g., Comiti et al., 2016; Ruiz‐Villanueva et al., 2013).…”

Winter dynamics of functional diversity and redundancy of riffle and pool macroinvertebrates after defoliation in a temperate forest stream

“…In temperate streams, particularly, leaves from riparian vegetation intensively fall in autumn and are accumulated in the riffles and pools ( Kobayashi and Kagaya, 2002 , 2004 ). As leaves are not only an important food source, but also can modify habitat heterogenicity, sudden accumulated leaves and thereafter decomposition can influence the structure and dynamics of macroinvertebrate community during winter ( Richardson, 1992 ; Mendes et al, 2017 ; Al-Zankana et al, 2021 ). Leaves are unevenly distributed in riverbeds and form so-called litter patches in both riffles and pools.…”