Do Human-modified Landscapes Affect Solitary Bee Diversity, Foraging, and Reproduction in Northern Florida?

Project Overview

GS10-092
Project Type: Graduate Student
Funds awarded in 2010: $10,000.00
Projected End Date: 12/31/2013
Grant Recipient: University of Florida
Region: Southern
State: Florida
Graduate Student:
Major Professor:
Dr. Katie Sieving
Wildlife Ecology / UF

Annual Reports

Commodities

  • Additional Plants: native plants

Practices

  • Education and Training: on-farm/ranch research
  • Natural Resources/Environment: biodiversity, habitat enhancement, hedgerows, wildlife
  • Production Systems: holistic management

    Abstract:

    We are studying the influence of land cover and farm habitat on solitary bee diversity and pollen collection. Of approximately 1,200 solitary bee specimens collected, 750 have been identified. Pollen processing is nearly complete at 100 samples, and identification has begun. ArcGIS facilitated characterization of land cover types in farm buffers. Preliminary results indicate 1) variation in bee community composition and abundance across farms in the study, 2) that pollen-carrying bees typically only carried 1-2 types of pollen, and 3) that 66 five hundred meter farm buffers across the study contained 8 land cover classes, pine being dominant.

    Introduction

    Purpose

    The purpose of this project is to assess the availability and possible contribution of native bees to sustainable agriculture in Northern Florida, and to identify factors that encourage diverse bee populations. Our study focused on pollination and species diversity on farms in two landscape contexts (natural and agricultural) to determine the influence landscape context has on shaping native bee populations. We ask the following questions: What native bees are found on sustainable farms and what do they pollinate? And, do the different landscape contexts affect the distribution and abundance of bees?

    Our initial proposal included bee reproduction as a response variable and the urban/suburban landscape context. However, over the life of the project these two aspects proved to be unfeasible. We could not find enough farms nested in urban/suburban areas, but found a number of them in the natural and agricultural contexts. Bee reproduction proved not to be feasible to include because of the difficulty (established by a preliminary study) in attracting Northern Florida’s solitary bees to nest in artificial structures. The purpose statement above reflects these changes in the project focus.

    Problem and Rationale

    Even though native bees have great potential as pollinators, their pollination choices (e.g. crop plants and/or native plants) have not been well studied here. With honeybees in decline or not meeting agriculture's growing demand for pollination (Johnson 2010) the native bees of Florida may already play a role as effective pollinators of crop plants (Hall 2010). The amount of pollination services native bees provide and how this varies with land management practices are unknown (Kremen 2002). And, with the variety of their body dimensions and tongue lengths, individual native bees are generally more effective than non-native honey bees as crop pollinators (Bohart 1972, Klein et al. 2007). Florida has over 300 species of native bees (Pascarella and Hall 2013) of which 140 species have been reported in this area (Hall and Ascher 2010).

    Kremen et al (2002) observed that solitary bees could provide full pollination services to an organic watermelon crop on a farm near natural habitat but not for farms at greater distances away or for those practicing conventional agriculture. Bees are influenced on the landscape scale by habitat fragmentation (Steffan-Dewenter et al 2002) with small bee species diversity and abundance increasing in proximity to semi-natural habitats. Thus we are aware that bee abundance, diversity, and pollination services interact with both landscape configuration and local farm management. But which is more important? Can farmers manage their farm vegetation to encourage native bees, or are native bee populations reliant on the landscape beyond the farmer’s control?

    This study examines the influence of landscape level factors and local, low-pesticide farm vegetation management practices on native bee diversity and abundance. We also use a proxy for pollination services- pollen carrying preferences of different bee species to indicate their potential-to-pollinate. Successfully determining the interaction of bees with farms and the surrounding landscape will give insight into managing native bee communities and indigenous pollination services that can be shared with farmers operating in Northern Florida landscapes.

    Justification

    Northern Florida provides an excellent study location because its projected urbanization will change the landscape context of farms here. Small farming operations in urbanizing foodsheds like North Central Florida’s are multiplying to fuel increasingly popular farmers markets (USDA 2013). Therefore this work will be especially relevant to farming in the urbanizing landscapes of this part of the state. Also, the decline in honeybee pollination services has been reported by beekeepers in this vicinity, so this is a great place to seek evidence that native bees may potentially be managed to fill the pollination gap.

    Project Relevance to Sustainable Agriculture

    Describing Native Bee Pollination: Florida has a diversity of bee species that may be important crop pollinators, but their importance to agriculture and what factors influence their pollination choices has not been studied here as it has been in other systems (e.g. Winfree et al. 2007in the Mid-Atlantic States and McIntyre et al. 2001 in Arizona). By identifying and collecting pollen from foraging native bees we will be able to identify which crops these bees have potential to pollinate (as with Westrich & Schmidt 1986) and provide information to farmers on which plants may be pollinated by native bees (and which bees) across different habitats. As a result of carrying out this project we hope be able to inform farmers in the area about whether or not they can take actions on the farm level to improve habitat for native bees. Our work will provide insight as to whether pollination as an ecosystem service performed by native bees is better in a natural landscape context than in more agricultural ones.

    Enhancing Ecosystem Services on Sustainable Farms

    Ideally, should sustainable farms should be located in biodiverse landscapes to allow the farms to take full advantage of ecosystem services like pest control by native enemies (Jones and Sieving 2006) and bee pollination? The success of sustainable agriculture is assessed unfairly because these farms are not located in their ideal contexts and assessment does not always consider what the farms return to their environs (e.g. cleaner water, healthier wildlife populations; Clerge et al. 2005). Also, the assessment of their success should not be entirely based on production of crop plants because these farms are expected to be more environmentally protective of ecosystem services (Wild Farm Alliance 2005). Our project will add to our knowledge of how and if sustainable farms support native bees (and vice versa) as an additional measure of benefits from these farms. On the practical side, this project will allow us to identify the set of native bee species that potentially pollinate crops.

    Project objectives:

    The central objective of our study is to determine the relative importance of a) on- farm management of vegetation and b) surrounding landscape factors as a predictor of native bee species richness, abundance, and pollen-carrying (Figure 1). The eleven farms in the study exhibit varied in on-farm vegetation management from closely mown lawn-like field verges to weedy edges and purposeful plantings of white clover and sunflowers as crops or ground cover. Do such plantings and vegetation affect the native bee diversity on these farms, or is diversity driven by landscape context? To answer this question, our study has four main objectives: 1) analysis of bee foraging habitat, 2) characterization of the landscape context of farms, 3) analysis of native bee species richness, and 4) analysis of pollen collection on farms by native bees.

      • • Landscape Context Effects: The landscapes around the 11 farms in the study are dominated by forest (pine plantations and mixed oak woodlands) and agricultural land covers (crops and pastures). The landscape mosaic around these farms also includes developed areas (i.e., roads, parking lots, and houses) and wetlands. Last year I included a table in my report that showed preliminary estimates of dominant and secondary land covers in the immediate vicinity of the farms. In 2012 I began the process of quantifying the land cover types around each farm out to a distance of three kilometers.
      • • Bee Foraging Habitat: The focus of this part of my study is to quantify the foraging habitat available for bees on the twelve farms. Foraging habitat includes crops that are flowering at different sampling times, farm edge vegetation, and habitat contained on some farms like preserved wetlands. I will determine if such habitats correlate with bee diversity on the farms.
      • • Bee Species Richness: This part of my study focuses on bee diversity and abundance on the farms. Two kinds of sampling contribute to this data: hand netting and bee bowls.
      • • Bee Pollen Choices: Here my study focuses on a possible pollination precursor- what bees are carrying as they forage on farms. Native bees collect and carry pollen to store for later consumption by their offspring, but the facts that they have this pollen on their bodies increases the likelihood that they may be pollinating flowers as they move between plants. Figuring out if they are actually pollinating flowers or their effectiveness at pollination is beyond the scope of this study.
    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.