DOI: 10.5061/dryad.k6djh9whp
title: Large wood supports hydrologically variable floodplain environments and aquatic biodiversity

description: It is increasingly recognized that riparian vegetation and wood play
 crucial roles in enhancing spatial heterogeneity in rivers. Historical
 removal of large wood and cutting of streamside forests around the world
 have simplified rivers and substantially reduced aquatic habitat
 complexity. To understand how (semi-)natural rivers sustain complex
 geomorphology and hydrology, and how they support aquatic diversity, we
 carried out an interdisciplinary field study in a stream flowing through a
 natural forest in Hokkaido, Japan. We mapped 65 side channels (a total of
 10.1 km long) along a 9.2 km length of the main channel. More avulsions
 and side channels were present in stream sections with a higher density of
 large wood and logjams. At flood stage, 90% of the side channels were
 inundated with through-flowing river water, while the other 10% remain
 disconnected from the river and harbor stagnant water. At low flow, only
 20% of the side channels had flow from the mainstream river, 46% contained
 stagnant water, and 34% were dry. In sum, the total surface area of side
 channels with permanent flow was 20%, side channels with transient flow
 were 9%, and disconnected side channels were 6% of the surface area of the
 main channel. We estimated the contribution of each habitat type with
 different hydrological regimes to the entire populations of aquatic
 animals in the studied segment. The analysis demonstrated that four out of
 eleven fish taxa, five out of 26 benthic macroinvertebrate taxa, three out
 of three plankton taxa, and two out of two amphibian taxa primarily
 utilized transient or disconnected channels. Furthermore, cohort analysis
 of dominant fish Salvelinus leucomaenis showed that they exhibit
 ontogenetic habitat shifts: they primarily utilize channels with transient
 flow as juveniles and then shift their primary habitats to channels with
 permanent flow, indicating the need for both types of habitats and their
 connectivity. Our results demonstrate form and process characteristic of
 the mostly lost and forgotten “baseline” of rivers in Japan; how
 geomorphologically and hydrologically complex a natural river can be; and
 how aquatic organisms rely on such complexity. Large wood potentially
 plays important roles in sustaining such complexity, and further studies
 should investigate these mechanisms.
description: # Large wood supports hydrologically variable floodplain environments and
 aquatic biodiversity
 [https://doi.org/10.5061/dryad.k6djh9whp](https://doi.org/10.5061/dryad.k6djh9whp) ## Description of the data and file structure All methods are described in the paper: "Large wood supports hydrologically variable floodplain environments and aquatic biodiversity", submitted to Ecological Applications. **202206Butokama_habitat2.xlsx**: Physical environment of the study sites * SiteID: site ID * L: length in meters * W: width in meters * Depth1,2,3: depth in cm * Sed1,2,3: organic sediment depth in cm * Flow1,2,3: flow rate cm/sec * sediment 1: primary sediment size * sediment 2: secondary sediment size, if applicable **202206Butokama.amph2.xlsx** * Site: study siteID * Frog: presence/absence of frog (1 is present, 0 is absent) * Salamander: presence/absence of salamander (1 is present, 0 is absent) * shrimp: presence/absence of shrimp (1 is present, 0 is absent) * note: note **202206Butokama.benthos2.xlsx** * Site: siteID * sampling: sampling method and replicate number. x 1/4 means 1/4 subsample were sorted. NA in Sampling indicated that there were not enough wet area where we could sample with the Surber net. * Area (m2): area that the sample (or subsample) represents. * Column D and after: number of benthic macroinvertebrate taxa counted in the sample (or subsample) **202206Butokama.connectivity2.xlsx** * Date: date (month/day/year) * Time: time of the day * Column C and after: hydrological connectivity data of each side channel to the mainstream river 1 indicates that it is hydrologically connected at the upstream end. (mainstream water flow through the channel) **202206Butokama.fish2.xlsx**: Fish data * Date: survey date * Site: siteID * Name: taxa name* * FL: fork length (mm) * Wt: weight (g) *correspondence of the taxon name and scientific name | Name | scientific name | Abbreviation | | :------ | :------------------------------------ | :------------------ | | fuku | *Barbatula\_barbatula* | B. oreas | | kajika | *Cottus\_nozawae* | C. nozawae | | yamame | *Oncorhynchus\_masou* | O. masou | | suna | *Lethenteron\_reissneri* | L. reissneri | | ukigori | *Gymnogobius\_urotaenia* | G. urotaenia | | iwana | *Salvelinus\_leucomaenis* | S. leucomaenis | | ugui | *Tribolodon\_hakonensis* | Pseudaspius spp. | | ito | *Parahucho perryi* | P. perryi | | yoshi | *Rhinogobius* sp. | Rhinogobius sp. | | yachi | *Rhynchocypris perenurus sachalinensis* | R.p. sachalinensis | | dojo | *Misgurnus anguillicaudatus* | M. anguillicaudatus | **202206Butokama.plankton2.xlsx**: Plankton data * site: siteID * Volume: sampled volume of water (all 10 liters in this study) * \&gt;500 Copepod: number of copepods in the sample (filtered on 500 micro meter-mesh) * \&gt;500 Cladocera: number of cladocera in the sample (filtered on 500 micro meter-mesh) * \&gt;500 Culicidae: number of Culicidae in the sample (filtered on 500 micro meter-mesh) **sectiontrait.csv**: Longitudinal physical environment data | column name | description | | :------------- | :---------------------------------------------------------------------------------------------- | | Section | longitudinal section in meters (each section is 50 meters long; lower numbers indicate downstream) | | NUMchannel | number of channels across valley | | NUMavulsion | number of channel avulsions within the section | | JAM | number of logjams  | | INDwood | number of woods (not in logjam) | | Mwood | number of medium-sized wood | | Lwood | number of large wood | | ORGANIC | organic materials | | MaxDepth | maximum depth in the section | | channel width | channel width (meter) | | valley width | valley width (meter) | | mainstream | number of channels in respective flow category in the section (mainstream) | | constant\_flow | number of channels in respective flow category in the section (constant flow) | | stopflowing | number of channels in respective flow category in the section (stop flowing) | | dry\_up | number of channels in respective flow category in the section (dry up) | | pond | number of channels in respective flow category in the section (pond) | | slope | slope (%) | | elevation | elevation (meter) | **side_channel.csv**: Spatial and physical characters of side channels | Column name | Description | | :------------- | :------------------------------------------------------------------------------------------------------------------------ | | Section | mainstream section where the side channel diverts (upstream end of the side channel) | | endsection | mainstream section where the side channel meets the mainchannel (downstream end of the side channel) | | origin.channel | Channel ID if the side channel diverts from another side channel. NA if diverted from the main channel. | | end.channel | Channel ID if the side channel meets with another side channel, but not the main channel. NA if diverted from the main channel. | | OBJECTID | Channel ID | | Lowflow | flow category of the channel | | sidelength.m | side channel length (meter) | | sidewidth.m | side channel width (meter) | | note | siteID if it is the channel that is the target of the biological survey |