Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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The significance of refuge heterogeneity for lowland stream caddisfly larvae to escape from drift
Brouwer, J.H.F. de; Kraak, M.H.S. ; Besse-Lototskaya, A.A. ; Verdonschot, P.F.M. - \ 2019
Scientific Reports 9 (2019)1. - ISSN 2045-2322

The process of macroinvertebrate drift in freshwater lowland streams is characterized by dislodgement, drift distance and subsequent return to the bottom. Refuges are important to all drift phases, since they may help larvae to avoid dislodgement and to escape from drift, even more so if the refuge structure is complex and heterogeneous. The aim of the present study was therefore to determine the influence of refuge heterogeneity on the ability of caddisfly larvae to return to the bottom from drift and to avoid secondary dislodgement. To this purpose a series of indoor flume experiments were undertaken, testing six Limnephilidae (Trichoptera) species, that occur on a gradient from lotic to lentic environments. Bed morphology (plain, refuges with or without leaf patches) and flow velocity (low (0.1 m/s), intermediate (0.3 m/s) and high (0.5 m/s) were manipulated. We showed that all species were favoured by refuges and that especially for species on the lentic end of the gradient (L. lunatus, L. rhombicus and A. nervosa), the ability to escape from drift and to avoid secondary dislodgement was increased. Moreover, we showed that all species spent more time in refuges than in open channel parts and more time in heterogeneous refuges (leaf patches) than in bare refuges, the latter being especially the case for larvae of the lotic species. For lentic species, not well adapted to high flow velocity, refuges are thus crucial to escape from drift, while for the lotic species, better adapted to high flow velocity, the structure of the refuge becomes increasingly important. It is concluded that refuges may play a crucial role in restoring and maintaining biodiversity in widened, channelized and flashy lowland streams.

Flow thresholds for leaf retention in hydrodynamic wakes downstream of obstacles
Brouwer, J.H.F. de; Eekhout, J.P.C. ; Besse-Lototskaya, A.A. ; Hoitink, A.J.F. ; Braak, C.J.F. ter; Verdonschot, P.F.M. - \ 2017
Ecohydrology 10 (2017)7. - ISSN 1936-0584 - 10 p.
current velocity - flow velocity - leaves entrainment - leaves transport - lowland streams - wake

Leaves are the major component of terrestrial litter input into aquatic systems. Leaves are distributed by the flow, accumulate in low flow areas, and form patches. In natural streams, stable leaf patches form around complex structures, such as large woody debris. Until now, little is known about flow conditions under which leaf patches persist. This study aims to quantify flow conditions for stable leaf patches and entrainment of leaf patches. We hypothesize that entraining flow processes, such as turbulence, Reynolds stress, or lift forcing (vertical flow velocity), best explain local leaf retention. This study was performed in an unscaled flume experiment, which conditions coincide with conditions found in low-energetic lowland streams. We positioned a wooden obstacle perpendicular to the flow on the bed of the flume. A leaf patch was positioned downstream from the wooden obstacle. The experiment was performed under 5 flow conditions. We monitored leaf patch cover and near-bed flow conditions in the area downstream of the wooden obstacle. We showed that near-bed flow velocities explain leaf retention better than more complex flow velocity derivatives such as turbulence, Reynolds stress, and vertical flow velocity. The entrainment near-bed flow velocity for leaves ranges from 0.037 to 0.050 m/s. Flow velocities frequently exceed those values, even in low-energetic lowland streams. Therefore, complex structures, such as woody debris, create flow conditions to support stable leaf patches. Thus, adding instead of removing obstacles may be a key strategy in restoring biodiversity in deteriorated streams.

Flow velocity tolerance of lowland stream caddisfly larvae (Trichoptera)
Brouwer, J.H.F. de; Besse-Lototskaya, A.A. ; Braak, C.J.F. Ter; Kraak, M.H.S. ; Verdonschot, P.F.M. - \ 2017
Aquatic Sciences 79 (2017)3. - ISSN 1015-1621 - p. 419 - 425.
Drift - Flow velocity - Lowland streams - Return rates - Trichoptera
The process of macroinvertebrate drift in streams is characterized by dislodgement, drift distance and subsequent return to the bottom. While dislodgement is well studied, the fate of drifting organisms is poorly understood, especially concerning Trichoptera. Therefore, the aim of the present study was to determine the ability of six case-building Trichoptera species to return to the stream bottom under different flow velocity conditions in a laboratory flume. The selected species occur in North-West European sandy lowland streams along a gradient from lentic to lotic environments. We determined species specific probability curves for both living and dead (control) specimens to return to the bottom from drift at different flow velocities and established species specific return rates. Species on the lotic end of the gradient had highest return rates at high flow velocity and used active behaviour most efficiently to return to the bottom from drift. The observed gradient of flow velocity tolerance and species specific abilities to settle from drift indicate that, in addition to dislodgement, the process of returning to the bottom is of equal importance in determining flow velocity tolerance of Trichoptera species.
Morphological assessment of reconstructed lowland streams in the Netherlands
Eekhout, J.P.C. ; Hoitink, Ton ; Brouwer, J.H.F. de; Verdonschot, P.F.M. - \ 2015
Advances in Water Resources 81 (2015). - ISSN 0309-1708 - p. 161 - 171.
Lowland streams - Morphodynamics - Re-meandering - Stream restoration - Water management

Channelisation measures taken halfway the 20th century have had destructive consequences for the diversity of the ecology in the majority of the lowland streams in countries such as the Netherlands. Re-meandering is the common practice in restoring these lowland streams. Three reconstructed streams were monitored during the initial two years after construction of a new channel. The monitoring program included morphological surveys, sediment sampling, habitat pattern surveys, and discharge and water level measurements. Adjustments of the longitudinal bed profile formed the main morphological response. These adjustments were most likely caused by a lack of longitudinal connectivity of the streams as a whole, interrupting transport of sediment at locations of weirs and culverts. Bank erosion was observed only in a limited number of channel bends, and was often related to floodplain heterogeneity. Longitudinal channel bed adjustments and bank erosion were mainly caused by exogenous influences. In channel bends, the cross-sectional shape transformed from trapezoidal to the typical asymmetrical shape as found in meandering rivers. This behaviour can be attributed to an autogenous response to the prevailing flow conditions. Due to the prevailing fine sediment characteristics, bed material is readily set in motion and is being transported during the entire year. The existing design principles fail to address the initial morphological development after reconstruction. An evaluation of pre-set targets to realise water depth and flow velocity ranges shows the current procedures to be deficient. Based on this unfavourable evaluation, and the two-dimensional nature of habitat patterns needed to improve the conditions for stream organisms, we recommend to predict morphological developments as part of the design procedures for lowland stream restoration in the Netherlands.

More cells, bigger cells or simply reorganization? Alternative mechanisms leading to changed internode architecture under contrasting stress regimes
Huber, H. ; Brouwer, J.H.F. de; Wettberg, E.J. von; During, H.J. ; Anten, N.P.R. - \ 2014
New Phytologist 201 (2014)1. - ISSN 0028-646X - p. 193 - 204.
shade-avoidance responses - impatiens-capensis balsaminaceae - phenotypic plasticity - population differentiation - arabidopsis-thaliana - nutrient availability - morphogenic responses - adaptive plasticity - stoloniferous herb - trifolium-repens
Shading and mechanical stress (MS) modulate plant architecture by inducing different developmental pathways. Shading results in increased stem elongation, often reducing whole-plant mechanical stability, while MS inhibits elongation, with a concomitant increase in stability. Here, we examined how these organ-level responses are related to patterns and processes at the cellular level by exposing Impatiens capensis to shading and MS. Shading led to the production of narrower cells along the vertical axis. By contrast, MS led to the production of fewer, smaller and broader cells. These responses to treatments were largely in line with genetic differences found among plants from open and closed canopy sites. Shading- and MS-induced plastic responses in cellular characteristics were negatively correlated: genotypes that were more responsive to shading were less responsive to MS and vice versa. This negative correlation, however, did not scale to mechanical and architectural traits. Our data show how environmental conditions elicit distinctly different associations between characteristics at the cellular level, plant morphology and biomechanics. The evolution of optimal response to different environmental cues may be limited by negative correlations of stress-induced responses at the cellular level.
Beekdalbreed Hermeanderen : bouwstenen voor de ‘leidraad voor innovatief beek- en beekdalherstel’
Verdonschot, P.F.M. ; Besse, A.A. ; Brouwer, J.H.F. de; Eekhout, J.P.C. ; Fraaije, R. - \ 2012
Amersfoort : Stowa (Rapport / STOWA 2012-36) - 56
beekdalen - ecosystemen - waterlopen - herstelbeheer - ecologisch herstel - natuurtechniek - aquatische ecologie - morfologie - brook valleys - ecosystems - streams - restoration management - ecological restoration - ecological engineering - aquatic ecology - morphology
Het doel van het project Beekdalbreed Hermeanderen was om in de praktijk in beekherstelprojecten een gedempt afvoer- en een stabiel en gevarieerd habitatpatroon te realiseren door morfologische en hydrologische maatregelen in samenhang uit te voeren. In 6 beekdalbreed uitgevoerde hermeanderingsprojecten en in 7 projecten, waarbij dood hout is ingebracht, is onderzocht welke hydrologische, morfologische, terrestrisch- en aquatisch-ecologische effecten optraden.
Wood addition to improve macro-invertebrate habitat suitability in Dutch streams
Brouwer, Jan de - \ 2011
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