DOI: 10.5061/dryad.3tx95x6pd
title: Tropical agroforestry supports insect pollinators and improves bean yield

description: Pollination services contribute to crop productivity worldwide, but insect
 pollinators are declining in most agricultural landscapes, mainly due to
 agricultural expansion and an increase in intensive agricultural
 practices. To reduce the negative effects of agricultural expansion and
 intensification, farmers can adopt ecological interventions, such as
 diversifying agricultural systems through agroforestry. However, there
 have been variable results on the effectiveness of agroforestry in
 enhancing pollinators and pollination services. Furthermore, most of the
 information has been generated in temperate regions, while the impact of
 agroforestry in tropical East Africa is largely unknown. Using common
 beans (Phaseolus vulgaris L.) as the focal crop, this study tested whether
 a tropical agroforestry system called Chagga home gardens supports
 pollinator communities and improves pollination and crop yield. We
 examined 16 agroforestry plots paired with 16 non-agroforestry plots
 located along a gradient of woody (trees and shrubs) cover within a 1 km
 radius to document the abundance, species richness and visitation rates of
 pollinating insects on bean flowers and how they contributed to bean
 yield. The beans planted in the agroforestry plots had almost twice the
 abundance of insect pollinators, three times the richness of the species,
 and almost twice the visitation rates than those planted in
 non-agroforestry plots. We also found a significant positive effect of
 woody cover in the surrounding landscape on insect pollinator abundances,
 but not on species richness and visitation rates. Additionally, the
 abundance and richness of insect pollinators increased significantly with
 flower abundance, while the overall plant richness in a plot significantly
 increased insect pollinator abundance and their visitation rate. The
 difference in bean yield between unbagged flowers (in which insect
 pollinators were allowed to access bean flowers) and bagged flowers and
 the total yield were higher in agroforestry than in non-agroforestry
 plots. Synthesis and Applications: This study showed that, compared to
 monoculture, agroforestry generally promotes pollination services in a
 tropical context. Furthermore, we found that agroforestry is likely to be
 particularly helpful for pollinators when it increases flower abundance
 and plant richness and if it is coordinated so that woody cover also
 increases at the landscape scale.
description: # Tropical agroforestry supports insect pollinators and improves bean
 yield
 [https://doi.org/10.5061/dryad.3tx95x6pd](https://doi.org/10.5061/dryad.3tx95x6pd) ## Description of the data and file structure The dataset contains three files. 1. Insect pollinator data: These data were used to analyse insect pollinator abundance, species richness, and visitation rates. The file contains 11 columns and 33 rows. All the column headings are self-explanatory. For the rows, apart from the headings row, the file has 32 rows (16 for agroforestry plots and 16 for non-agroforestry plots) Farming system: This column contains the plots of the two farming systems studied in this paper (16 agroforestry and 16 non-agroforestry plots) PairID: This column contains the pairs identification numbers, eg. we had 16 pairs and 32 plot, so pair 1 contains two plots, one is agroforestry and one is non-agroforestry PlotID: This column contains plot identification number, eg. Pair 1 has two plots, P1A = Pair one agroforestry, P1N = Pair one non-agroforestry Flower visitors abundance (Insect pollinator abundance): This contain number insect pollinators that visited bean flower in each plot during field survey. The abundance of insect pollinators per plot was calculated as the total number of individuals recorded visiting bean flowers within plots during study time. Flower visitors richness (Insect pollinator richness): This contains number of insect pollinator taxa that visited bean flower in each plot during field survey. The species richness per plot was calculated as the total number of insect pollinator taxa that visited bean flowers within plots during study time Visitation rate: This column contains mean number visitation per flower per observation time in each plot. Visitation rate was calculated as the total number of visits per flower per observation time Wood cover: The mapping of woody cover at the landscape level started by dividing the study area into grids of 500 x 500 m in the QGIS software. The created grids were then converted to KML files. After that, the KML file was imported into Google Earth to guide the digitization, which was done in grids. The digitization of woody cover was done in Google Earth using Google Earth photos from the year 2022, the year that this study was conducted. After digitization, the woody cover layer was imported into QGIS to estimate the proportion (%) of woody cover within 1 km (1000 m) radii around each agroforestry and non-agroforestry plot. Flower richness: The flower richness was estimated as the total number of wood and herbaceous plant species/taxa that were in bloom during the time of the survey. Flower abundance (x10): For trees and shrubs, the overall abundance and species richness were obtained by recording all species and counting their individuals in each plot (Delaney et al., 2020). Furthermore, their flower abundance was subjectively estimated using a scale of 1 to 4 as per Samnegård et al. (2016). One (1) was given to a tree or shrub with &lt;10 flowers while 2 =10-100 flowers, 3 = 101-1000 flowers and 4 = &gt;1000 flowers. Subsequently, each scale was translated into an estimated average number of flowers, with 1 = 5 flowers, 2 = 50 flowers; 3 = 500 flowers, and 4 = 5000 flowers (Samnegård et al., 2016). For example, a tree with less than 10 flowers will be given a scale of 1 and its estimated average number of flowers will be 5. Herb floral resources and overall abundance and species richness were estimated in subplots and then extrapolated for the whole plot. A total of 9 (1m^2) subplots were established in each plot and all flowers, individuals, and species of herb plants were recorded. Overall plant richness: This was estimated as total number of wood and herbaceous plant species in each plot Overall plant abundance: This was estimated as total number of wood and herbaceous plants in each plot 2. NMDS data: These data were used to make the NMDS plot, The file contains insect species on the columns and farming systems plots on rows. Some of the species (rare ones) were removed during NMDS plotting but the full list of species is available in the supplementary materials of the paper 3. Bean Yield data: These data were used to analyse bean yield between pollinated and un-pollinated beans in agroforestry and non-agroforestry plots Pair ID: This column contains the pairs identification numbers in which pollination experiment was conducted and we managed to harvest. This is because, we conducted pollination experiment in all pairs but in some plots farmers harvested their beans before we could harvest. We analysed bean yield in pairs where all the two plots were harvested so we can compare. Plot ID: This column contains plot identification number in which pollination experiments were conducted Habitat type: This term was used interchangeably with farming system, so it is the same thing Pollination treatment: This column contain type of pollination experiments studied (Bagged = Bean plants were bagged with polyethylene net. The mesh prevented insects from visiting the flowers, but allowed sunlight and airflow to the bagged bean plants, Open = the bean flowers were continuously accessible to insects, wind, and autonomous self-pollination) Plant ID in a plot: This column contain plant identifications number of the plants that were used for pollination experiment in each plot Pods: We recorded the fruit set as the number of pods per plant. Number of seed per pod: We recorded the seed set as the number of seeds per pod. Yield quantity (g): The quantity of yield was measured as the weight (grams) of air-dry bean seeds per plan