DOI: 10.5061/dryad.crjdfn3d8
title: Nutrients, isolation and lack of grazing limit plant diversity in restored wetlands

description: Agricultural intensification has led to the loss of most natural wetlands
 from human-dominated landscapes but, in recent decades, wetland
 restoration has gained traction worldwide. Restoration of suitable habitat
 conditions is hampered by nutrient residues from decades of high-input
 farming, by continued input of nutrients from surrounding farmland, and by
 incomplete restoration of natural hydrology. We assessed the
 effect of wetland restoration and disturbance (grazing) on vascular plant
 and bryophyte diversity in restored wetlands in Denmark at plot and
 landscape scales. Compared to near-natural wetlands, we found a
 lower species richness and community uniqueness in restored wetlands, but
 we also found that grazing had a positive effect on vascular plant
 richness in restored wetlands. The size of the local species pool, the
 presence of near-natural habitat prior to restoration, and near-natural
 restored hydrology all had positive effects on plant diversity, while high
 soil iron and nitrogen had negative effects. Synthesis and applications:
 Restoration of plant diversity in wetlands is challenging, but our results
 point to potential remedies: plan restoration areas near colonisation
 sources of the target biota, restore hydrology to near-natural conditions,
 discontinue nutrient loads from surrounding arable land and restore
 near-natural grazing regimes. Bryophytes may be particularly useful as
 indicators for successful restoration of wetlands.
description: We conducted this study on landscape (hectares) scale and plot
 (m<sup>2</sup>) scale. At the landscape scale, we used
 landscape-scale predictors to evaluate the plant biodiversity in wetlands
 that had been restored under The Action Plans on the Aquatic Environment
 and compared those sites with near-natural reference sites. At the plot
 scale, we evaluated the effects of grazing (no active management vs.
 grazing) and local environmental predictors on plant biodiversity in
 restored and near-natural wetlands. We define restoration success as
 similarity between restored and near-natural sites in terms of plant
 species richness, community uniqueness and community
 composition.
description: # Nutrients, isolation and lack of grazing limit plant diversity in
 restored wetlands
 [https://doi.org/10.5061/dryad.crjdfn3d8](https://doi.org/10.5061/dryad.crjdfn3d8) ## Description of the data and file structure We conducted this study on landscape (ha) scale and plot (m2) scale. At the landscape scale, landscape-scale predictors (Dataset 1 Landscape_scale_data) were used to evaluate the plant biodiversity in restored wetlands in comparison to near-natural reference sites (Dataset 2 Landscape_scale_monitoring_data). At the plot scale, we evaluated the effects of grazing (no active management vs. grazing) and local environmental predictors on plant biodiversity in restored and near-natural wetlands (Datasets 3 Plot_scale_vegetation_data and 4 Plot_scale_data). #### **Dataset 1 Landscape**\_**scale**\_**data** | Variable | Description, data source | | :---------------------------------------------- | :------------------------------------------------------------------------------------------------------------------- | | polygon\_id | Wetland polygon identifier (Aarhus University, 2023; Miljøministriet, 2023) | | wetland\_id | Wetland identifier (Landbrugsstyrelsen, 2022) | | vascular\_plant\_richness | Vascular plant richness (Aarhus University, 2023; Miljøministriet, 2023) | | sir\_vascular\_plant | Vascular plant community uniqueness, calculated as sum of inverse range sizes (Hartvig and Vestergaard, 2015) | | bryophyte\_presence\_absence | Bryophyte presence-absence (Aarhus University, 2023; Miljøministriet, 2023) | | local\_wetland\_species\_pool | Local wetland species pool (Hartvig and Vestergaard, 2015) | | x\_coordinates | West-East gradient - projected longitudinal coordinates for each wetland centroid (Landbrugsstyrelsen, 2022) | | protected\_wetland\_grassland\_habitats\_buffer | Protected wetland and grassland habitats within a 500 m buffer zone (Aarhus University, 2023; Miljøministriet, 2023) | | mean\_grazing\_density | Mean grazing density (Ejrnæs et al. 2021) | | restoration\_age | Restoration age (Aarhus University, 2023; Miljøministriet, 2023) | | sand\_gravel | Sand and gravel, % (Pedersen et al. 2011) | | clay | Clay, % (Pedersen et al. 2011) | | freshwater\_formations | Freshwater formations, % (Pedersen et al. 2011) | | mean\_hydrology\_score | Mean hydrology score (Ejrnæs et al. 2021) | | wetland\_area | Wetland area, ha (Landbrugsstyrelsen, 2022) | | landuse\_prior\_forest | Forest prior to restoration, % | | landuse\_prior\_arable\_land | Arable land prior to restoration, % | | landuse\_prior\_near-natural | Near-natural habitat prior to restoration, % | | landuse\_prior\_improved\_grassland | Improved grassland prior to restoration, % | | eiv\_n | Mean Ellenberg indicator value for soil fertility (Ellenberg et al., 1991)  | | eiv\_f | Mean Ellenberg indicator value for moisture (Ellenberg et al., 1991) | #### **Dataset 2 Landscape**\_**scale**\_monitoring\_**data** | Variable | Description, data source | | :--------------------------- | :-------------------------------------------------------------------------- | | wetland\_id | Wetland identifier (Landbrugsstyrelsen, 2022) | | vascular\_plant\_richness | Vascular plant richness (Aarhus University, 2023; Miljøministriet, 2023) | | bryophyte\_presence\_absence | Bryophyte presence-absence (Aarhus University, 2023; Miljøministriet, 2023) | #### **Dataset 3 Plot**\_**scale**\_vegetation\_**data** | Variable | Description | | :------- | :----------------------------------- | | species | Vascular plant and bryophyte species | | plot | Plot identifier | #### **Dataset 4 Plot**\_**scale**\_**data** | Variable | Description, data source | | :----------------------------- | :------------------------------------------------------------------------------------------------------------ | | plot | Plot identifier | | site | Site identifier | | stream | Stream identifier (OD - Odense, OM - Omme, TR - Trggevælde) | | richness\_vascular\_plant | Vascular plant richness | | sir\_vascular\_plant | Vascular plant community uniqueness, calculated as sum of inverse range sizes (Hartvig and Vestergaard, 2015) | | richness\_bryophyte | Bryophyte richness | | sir\_bryophyte | Bryophyte community uniqueness, calculated as sum of inverse range sizes (Naturbasen, 2024) | | grazing | Grazing (G - grazed, U- ungrazed) | | status | Status (R - restored, N - near-natural) | | soil\_moisture | Average soil moisture for May-September, % | | p\_soluble | Soluble P, µg 10 cm-2 4 weeks-1 | | n\_plant\_available | Plant-available N, NO3-N+NH4-N µg 10 cm-2 4 weeks-1 | | soluble\_fe | Soluble Fe, µg 10 cm-2 4 weeks-1 | | ca\_soluble | Soluble Ca, µg 10 cm-2 4 weeks-1 | | eiv\_n | Ellenberg indicator values for soil fertility (community weighted mean) | | eiv\_f | Ellenberg indicator values for moisture (community weighted mean) | | liiter\_pin\_point\_count | Standing and lying litter (count of pin-point hits) | | woody\_plant\_cover | Woody plant cover, % | | herbaceous\_vegetation\_height | Average height of herbaceous vegetation, cm | ## Sharing/Access information Data was collected in the field as well as derived from the following sources: * Aarhus University (2023). NOVANA program for terrestrial habitats and species. [https://novana.au.dk/](https://novana.au.dk/) (Accessed 08.03.2023.). * Ejrnæs, R., Bladt, J., Dalby, L., Pedersen, P. B. M., Fløjgaard, C., Levin, G., Baaner, L., Brunbjerg, A. K., Mellerup, K., Angelidis, I., & Nygaard, B. (2021). Udvikling af en dansk naturindikator (DNI). Videnskabelig rapport nr. 460. Aarhus: Aarhus Universitet, 60. * Ellenberg, H., Weber, H. E., Dull, R., Wirth, V., Werner, W., & Paulissen, D. (1991). Zeigerwerte von Pflanzen in Mitteleuropa. Scripta Geobotanica, 18, 1-248. * Hartvig, P., & Vestergaard, P. (2015). Atlas Flora Danica. København: Gyldendal, 1584. * Landbrugsstyrelsen (2022). Overview of map themes. Wetland restoration projects. [https://landbrugsgeodata.fvm.dk/](https://landbrugsgeodata.fvm.dk/) (Accessed 01.08.2022.). * Miljøministriet (2023). Protection of §3 habitat types. [https://mst.dk/natur-vand/natur/national-naturbeskyttelse/3-beskyttede-naturtyper/beskyttelse-af-3-naturtyper/](https://mst.dk/natur-vand/natur/national-naturbeskyttelse/3-beskyttede-naturtyper/beskyttelse-af-3-naturtyper/) (Accessed 08.03.2023.). * Naturbasen (2024). Naturbasen. [https://www.naturbasen.dk/](https://www.naturbasen.dk/) (Accessed 18.10.2024.). * Pedersen, S. A. S., Hermansen, B., Nathan, C., & Tougaard, L. (2011). Digitat map of Danish soil types 1: 200.000, version 2. København: GEUS, 5.