DOI: 10.5061/dryad.80gb5mkp3
title: Efficacy of cover crops for pollinator habitat provision and weed suppression

description: Pollinator declines have been documented globally, but little information
 is available about native bee ecology in Midwestern US agriculture. This
 project seeks to optimize pollinator support and weed suppression in a
 3-year crop rotation with a fallow growing season. During fallow, one of
 five cover crop treatments (T1: crimson, red, and ladino clover and Bob
 oats [Trifolium incarnatum, T. pratense, T. repens, Avena sativa]; T2:
 crimson clover and oats; T3: red clover and oats; T4: ladino clover and
 oats; T5: no cover crop; T6/control: winter wheat [Triticum aestivum]) was
 seeded in one-half of 25 agricultural fields, while wheat was left
 unharvested in the other half as a comparison. Treatments that provide
 season-long floral resources support the greatest bee diversity and
 abundance (T1), and treatments with red clover support declining Bombus
 species (T1 and T3). Late-season floral resources may be important, yet
 limited (T1 and T4), and some species of agricultural weeds provide floral
 resources. Floral diversity may be less important than flower abundance or
 timing for pollinator diversity (T1 – T4). Weed diversity was greatest in
 the no cover crop treatment (T5), least in winter wheat (T6), and
 intermediate in cover crop treatments (T1 – T4) with no differences in
 weeds of economic concern. Wheat suppresses weeds but does not provide
 floral resources for pollinators. These results may also be applicable to
 marginal lands taken out of cultivation or field margin pollinator
 plantings in a typical corn-soybean rotation. Floral resource availability
 across the landscape is critical to maintain pollinator diversity.
description: Data collection and processing is outlined in detail in Bryan et
 al., Efficacy of cover crops for pollinator habitat provision and weed
 suppression, in the journal Environmental Entomology. Methodology is also
 included in the usage notes section below. 
description: COMMUNITY DATA: The first
 two files listed below contain community data for bee species and weedy
 plant species, respectively. The first column is ‘Ordcode’ and corresponds
 to the given environmental data files (Bee_ENV.csv, Weeds 2017 ENV.csv)
 and site and treatment information, as well as survey timings for species
 occurrence. The other columns contain species codes. In the bee dataset,
 species names are composed of the first three letters of the genus name
 and the first three letters of the species name. In the weeds community
 dataset, the species names are 5-letter codes, which typically represent
 the first three letters of the genus name and the first two letters of the
 species name, following the European and Mediterranean Plant Protection
 Organization (EPPO) coding system (https://www.eppo.int).
 For weed species sampling, a chevron-patterned transect was designed in
 ArcGIS prior to conducting surveys. Transects consisted of 20 points,
 spaced 10-20 m apart. Researchers navigated to each point and sampled
 community data using a 0.5 x 1 m quadrat. Species and percent cover were
 measured at each plot. FILE:
 Bee_community_1s_removed.txt (Bray-Curtis dissimilarity was
 used to ordinate samples, since it is one of the most robust ordination
 methods. Survey rounds where one sample had zero taxa were removed for
 multivariate analysis. The dataset used in analysis is provided here with
 some omitted samples.) FILE: Weeds 2017.txt
 ENVIRONMENTAL DATA: The
 environmental datafiles provided for multivariate analysis, which
 correspond to the community data files, are: Bee_ENV.csv, Bee
 ENV_remove0_1s_removed.csv, and Weeds 2017 ENV.csv. FILE: Bee_ENV.csv Ordcode – This is the code
 provided to relate the community and environmental datasets for
 multivariate analysis. Field – Fields were located at
 Crab Orchard National Wildlife Refuge in Marion, Illinois, USA. A map is
 available in Bryan et al. (accepted) Environmental Entomology. Field sizes
 ranged from 3.82 to 9.48 ha and averaged 5.36 ha. Fields were divided in
 half; one half was planted in the control treatment, Triticum aestivum L.
 (winter wheat), and the other half was planted in one of five clover cover
 treatments. Treatments were replicated 5 times and completely randomized
 across the Refuge land. Treatments were planted immediately prior to
 soybean harvest in September 2016. Method – This is the method of
 bee specimen capture: ‘Net’ or pan ‘Trap’. Treatment – This is abbreviated
 ‘T’. Numbers in parentheses represent the seeding rates of each cover
 species in kg/ha. Fields were assigned one of 6 treatments: T1 - Clover
 3-Way and Bob Oats [<i>Trifolium incarnatum</i> (7.8),
 <i>T. repens</i> (4.5), <i>T. pratense</i> (1.7),
 and <i>Avena sativa</i> (16.8)], T2 - Crimson Clover and Bob
 Oats [<i>T. incarnatum</i> (16.8) and <i>A.
 sativa</i> (22.0)], T3 - Red Clover and Bob Oats [<i>T.
 pratense</i> (11.0) and <i>A. sativa</i> (22.0)], T4 -
 Ladino Clover and Bob Oats [<i>T. repens</i> (4.5) and
 <i>A. sativa</i> (22.0)], T5 - No Cover Crop [None], T6 -
 Control: Winter Wheat [<i>Triticum aestivum</i>
 (112.0)]. NestedT
 – This variable groups the field halves, T1-5 or T6, for analysis. This
 allows comparison of the paired treatment with the control.
 Round – Six surveys or
 ‘rounds’ were performed. Bee sampling occurred approximately every three
 weeks from mid-April to late-August 2017. CorT – This denotes control ‘C’
 or treatment ‘T’. Field.CT – This is a combination
 of ‘Field’ code and ‘C’ or ‘T’ notation. S – Richness, or number of
 species, per sample. N – Number of individuals per
 sample. d –
 Diversity. ‘****’ here and throughout notes that species and individuals
 were too few to calculate. J' – Pielou’s
 evenness H'(loge) – Shannon-Weiner
 diversity index eH – the effective number of
 species 1-Lambda' – Simpson
 index FA.S –
 Floral abundance richness FA.N – Floral abundance number of
 individuals FA.J
 – Floral abundance evenness FA.H – Floral abundance
 diversity FA.eH –
 Floral abundance effective number of species Apimel – Abundance of honey
 bees  
 FILE: Bee
 ENV_remove0_1s_removed.csv Variables are coded in the same
 way as the file above. The difference is that this file corresponds to the
 bee community file provided, with the same survey rounds
 removed. FILE:
 Weeds 2017 ENV.csv Ordcode - This is the code
 provided to relate the community and environmental datasets for
 multivariate analysis. Field – Fields were located at
 Crab Orchard National Wildlife Refuge in Marion, Illinois, USA. A map is
 available in Bryan et al. (accepted) Environmental Entomology. Field sizes
 ranged from 3.82 to 9.48 ha and averaged 5.36 ha. Fields were divided in
 half; one half was planted in the control treatment, Triticum aestivum L.
 (winter wheat), and the other half was planted in one of five clover cover
 treatments. Treatments were replicated 5 times and completely randomized
 across the Refuge land. Treatments were planted immediately prior to
 soybean harvest in September 2016. Treatment – This is abbreviated
 ‘T’. Numbers in parentheses represent the seeding rates of each cover
 species in kg/ha. Fields were assigned one of 6 treatments: T1 - Clover
 3-Way and Bob Oats [<i>Trifolium incarnatum</i> (7.8),
 <i>T. repens</i> (4.5), <i>T. pratense</i> (1.7),
 and <i>Avena sativa</i> (16.8)], T2 - Crimson Clover and Bob
 Oats [<i>T. incarnatum</i> (16.8) and <i>A.
 sativa</i> (22.0)], T3 - Red Clover and Bob Oats [<i>T.
 pratense</i> (11.0) and <i>A. sativa</i> (22.0)], T4 -
 Ladino Clover and Bob Oats [<i>T. repens</i> (4.5) and
 <i>A. sativa</i> (22.0)], T5 - No Cover Crop [None], T6 -
 Control: Winter Wheat [<i>Triticum aestivum</i>
 (112.0)]. CorT –
 This denotes control ‘C’ or treatment ‘T’. Field.CT – This is a combination
 of ‘Field’ code and ‘C’ or ‘T’ notation. Round – There were 3 rounds or
 survey periods (early April, mid-June, and late July in 2016 and
 2017. Survey
 Year  - 2016 or 2017. Surveys in 2016 were taken while files were in a
 soybean rotation and were intended as a baseline comparison for the weed
 community data. Surveys in 2017 occurred while the fields were planted
 into the clover cover treatments. S – Richness, or number of
 species, per sample. J' – Pielou’s
 evenness H'(loge) – Shannon-Weiner
 diversity index eH – the effective number of
 species faS –
 Floral abundance richness faJ' – Floral abundance
 evenness faH'(loge) – Floral
 abundance diversity faeH – Floral abundance effective
 number of species faSumCover – Floral abundance sum
 of cover AVESA –
 Cover of Avena sativa L. TRFIN – Cover of Trifolium
 incarnatum L. TRFPR – Cover of Trifolium
 pratense L. TRFRE
 – Cover of Trifolium repens L. TRZAW – Cover of Triticum
 aestivum L.   FILE: Floral Abund.csv
 Sample – This corresponds
 to ‘Ordcode’ in other files. S – Richness, or number of
 species, per sample. N – Number of individuals per
 sample. J' –
 Pielou’s evenness H'(loge) – Shannon-Weiner
 diversity index e^H' – the effective number
 of species Field
 – Fields were located at Crab Orchard National Wildlife Refuge in Marion,
 Illinois, USA. A map is available in Bryan et al. (accepted) Environmental
 Entomology. Field sizes ranged from 3.82 to 9.48 ha and averaged 5.36 ha.
 Fields were divided in half; one half was planted in the control
 treatment, Triticum aestivum L. (winter wheat), and the other half was
 planted in one of five clover cover treatments. Treatments were replicated
 5 times and completely randomized across the Refuge land. Treatments were
 planted immediately prior to soybean harvest in September 2016.
 Treatment – This is
 abbreviated ‘T’. Numbers in parentheses represent the seeding rates of
 each cover species in kg/ha. Fields were assigned one of 6 treatments: T1
 - Clover 3-Way and Bob Oats [<i>Trifolium incarnatum</i>
 (7.8), <i>T. repens</i> (4.5), <i>T. pratense</i>
 (1.7), and <i>Avena sativa</i> (16.8)], T2 - Crimson Clover
 and Bob Oats [<i>T. incarnatum</i> (16.8) and <i>A.
 sativa</i> (22.0)], T3 - Red Clover and Bob Oats [<i>T.
 pratense</i> (11.0) and <i>A. sativa</i> (22.0)], T4 -
 Ladino Clover and Bob Oats [<i>T. repens</i> (4.5) and
 <i>A. sativa</i> (22.0)], T5 - No Cover Crop [None], T6 -
 Control: Winter Wheat [<i>Triticum aestivum</i>
 (112.0)]. NestedT
 – This variable groups the field halves, T1-5 or T6, for analysis. This
 allows comparison of the paired treatment with the control.
 Round – Six surveys or
 ‘rounds’ were performed. Floral abundance was measured at the same time as
 bee sampling, approximately every three weeks from mid-April to
 late-August 2017. CorT – This denotes control ‘C’
 or treatment ‘T’. Field.CT – This is a combination
 of ‘Field’ code and ‘C’ or ‘T’ notation.   ANALYSIS FILES: Bees PERMANOVA – This file
 contains the R code for the bee multivariate analysis. Floral Abund – This file contains
 the R code to analyze floral abundance. Weeds PERMANOVA – This file
 contains the R code for the weeds multivariate analysis.