Effects of Habitat Heterogeneity on Crop Yield and Biodiversity

Progress report for GW19-199

Project Type: Graduate Student
Funds awarded in 2019: $24,971.90
Projected End Date: 07/31/2022
Grant Recipient: 1992
Region: Western
State: Montana
Graduate Student:
Major Professor:
Expand All

Project Information

Summary:

Agricultural ecosystems comprise roughly half of the global land surface and are faced with the competing tasks of feeding a growing population and conserving global biodiversity. Agriculture has often been viewed as a primary driver of habitat fragmentation and biodiversity loss, but recent studies have questioned the habitat-matrix paradigm with findings of positive relationships between landscape configurational heterogeneity and biodiversity in agricultural landscapes. Current research suggests the adoption of a mosaic landscape matrix paradigm, in which landscape heterogeneity enhances biodiversity with neutral or positive effects on crop yield. This study uses ecological refugia (uncropped islands in production fields) to examine habitat heterogeneity and the effects on crop yield and biodiversity in farmland. Precision agriculture data is used to create yield maps that enable farmers to identify low-producing areas in their fields that can be taken out of production to save time and money and create conservation habitat in the agricultural ecosystem. We quantify the effects of heterogeneity to determine if ecological refugia provide benefits to farmers such as enhanced biodiversity, ecosystem functions and farm productivity in agroecosystems.

Project Objectives:

My goal is to quantify the agronomic, economic and biodiversity impacts of midfield islets (refugia) in dryland small grain production region of the Northern Great Plain (NGP). Specifically, I will quantify the effects of habitat heterogeneity on yield and biodiversity in production fields.

  1. Quantify what costs and benefits midfield islets bring to farm production. We aim to determine if midfield islets affect agricultural production by looking for significant differences in crop yield and crop quality between homogeneous and heterogeneous fields and landscapes.
  2. Determine the tradeoff between ecosystem services and disservices that midfield islets create for producers. We aim to determine if midfield islets affect ecosystem resilience by looking for significant differences in pollinator, parasitoid, bird and small mammal populations, plant species richness, and pest and weed predation between homogeneous and heterogeneous fields.
  3. Share findings of on-farm experimentation through farmer-to-farmer networks, evaluate producers’ attitudes towards biodiverse farming methods and identify barriers to producer adoption.
Timeline:

GanttChart_Duff_2019

Objective 1: Crop Quality and Yield Maps

Previous precision agriculture data from our 3 producers will be researched in spring 2019. Yield and profit maps will be generated in the spring for all 6 fields from 2019-2021. Results and field prescriptions will be presented at the PARA meeting in November. Grain samples will be collected in summer 2019 and 2020 and sent for trace element analysis at the UC Davis Lab. All crop quality and profit maps of will be analyzed, shared with participating producers and submitted for publication by spring 2021.

Objective 2: Biodiversity Surveys

Biodiversity monitoring methods will be researched and prepared in spring 2019. Field surveys of pollinators, mammals, vegetation, and insects will be conducted across 6 fields in summer and fall 2019-2021. Data analysis will be ongoing following summer 2019. Results will be shared continuously with participating producers and presented to PARA members at the November meeting in 2019 and 2020. Results will be submitted for publication by spring 2021.

Objective 3: Producer Adoption

Preliminary surveys of PARA producers’ willingness to adopt wildlife friendly farming techniques will be prepared and conducted in spring 2019 and 2020. Post surveys of producer willingness to adopt wildlife friendly farming techniques will be conducted in winter 2021. Amoeba diagrams of producer perceptions of on-farm biodiversity and ecosystem services will be prepared and completed in spring 2019 and 2020. Ongoing evaluations of producer satisfaction, adoption of agroecological methods and mastery of precision agriculture technology will be designed and completed by Pheasants Forever-associated producers in the spring of 2019 and 2020. Data analysis will be ongoing following the first spring of surveys. Results will be shared during farmer field tours July 2019-2020 and annual PARA meeting November 2019-2020, with journal submissions spring 2021.

 

Cooperators

Click linked name(s) to expand
  • Gary Broyles - Producer (Researcher)
  • Casey Bailey - Producer (Researcher)
  • Ole Norgaard - Producer (Researcher)

Research

Materials and methods:

In this study, we examine the potential for wildlife habitat conservation within agricultural systems by evaluating the potential for uncropped islands to serve as ecological refugia for biodiversity in production fields. We will evaluate heterogeneity at the field and landscape level using an index of vegetative heterogeneity (plant cover type) and landscape heterogeneity (ecological refugia) to determine its impact on biodiversity (including insects, plants and small mammal activity) and associated agroecosystem services. Three fields with and three fields without ecological refugia were selected from three farms across Montana to compare yield and biodiversity data between homogeneous (fields without ecological refugia) and heterogeneous fields (fields with ecological refugia). Farm 1 pictured below shows a 2.12 acre (8,593 m2) ecological refuge within a 74.4 acre (310,168 m2) field. Farm 2 shows a 45.9 acre (185,745 m2 ) refuge within a 156 acre (632,280 m2) field. Lastly, Farm 3 shows a 0.39 acre refuge (1,596 m2 ) within a 241 acre (1,135,179 m2) field.

 

Fahrig’s definition of functional landscape heterogeneity will be used to identify functional cover types that are based on the resource dependencies of species rather than physical habitat characteristics. Functional cover types will be designated across all six fields to compare how yield and biodiversity vary with habitat spatial heterogeneity. In addition, the mean regional crop diversity within ten kilometers of the center of each field (over the past four years) will be accessed using USDA CropScape (USDA, 2015). Within field heterogeneity will be estimated using a vegetative cover type index and within field biodiversity will be evaluated with plant and insect field surveys. We will use these survey results to model patterns of biodiversity distribution across vegetative cover types and test the hypothesis that heterogeneity in vegetation structure provides a greater variety of habitat for wildlife.

Methods for Objective 1: Precision agriculture technology (combine harvester mounted yield monitors and grain protein analyzers) will be used to create yield maps and identify low-yield and high-input areas in each field. These will be converted to profit maps that quantify the costs and benefits of converting low-producing areas to refugia (e.g. wildlife habitat). The same maps will be used to highlight any effects of habitat spatial heterogeneity on crop yield and quality by mapping yield and protein content in relation to the spatial configuration (distance to, size, etc.) of ecological refugia. Spatial differences in yield and nutrient concentration will determine if midfield islets offer costs or benefits to producers by determining if crop yield and quality vary significantly between homogeneous and heterogeneous fields as a function of distance to refuge. 

Methods for Objective 2: Plant, insect and seed predation surveys will be used to compare ecosystem services associated with agrobiodiversity across field types. Six 100 meter transects were established in a radial design from the center of each refuge and extended out to the cropped area for each type of survey. Sweep nets were used to trap and identify pollinators and parasitoids (bees, butterflies, wasps, etc.) along each transect in 20 meter segments, with a total of 100 sweeps per transect. One sweep was considered as one step taken as the net is swept in a 180 degree arc as low as possible to the ground. All collected insect specimens from 2020 were frozen and identified in the winter of 2020. All collected specimens from 2021 will be identified in the winter of 2021. The number of total individuals captured will be weighed for biomass and sorted to the order level to compare winged insect diversity between the two types of fields. In the summer of 2021, 240 pitfall traps were set in all fields to assess ground-dwelling beetle biomass and species richness. These insects are currently preserved and will be processed in the winter of 2021.

Vegetation monitoring plots were used to compare plant species richness

1. between homogenous and heterogeneous fields

2. as a function of distance from refugia within heterogeneous fields.

To assess plant diversity, occurrence of all grasses, forbs and shrubs were recorded at 10-m intervals along the pre-established transects in quarter meter squared frames. There was a total of 60 vegetation sampling frames per field. Species richness was defined as the total number of plant species encountered in a frame. Plant species diversity was evaluated with Shannon's Diversity Index.

 

Seed traps were used to assess seed predation and small mammal activity in production fields.  Five seed traps were be placed in each field at 20-meter intervals along the six transects, for a total of 30 seed traps per field. Each seed trap offers two weed seeds (field pennycress and wild oat) and two crop seeds (pea and wheat). Seed predation outcomes were assessed by counting the number of seeds eaten from each trap. Predation patterns were assessed by examining the proportion of weed predation to crop predation in fields with and without ecological refugia.

 

Six grain samples were taken at 20-meter intervals along one transect from each field for a total of 36 grain samples in the summer of 2021. Grain samples were tested at Montana State University's Barley, Malt & Brewing Lab for moisture, protein, iron and total plant phenols. These results are used to assess crop nutrition and crop quality as a function of distance from the refuge.

Significant differences in winged insect & ground-dwelling carabid diversity and abundance, plant species richness, seed predation habits and crop quality between homogeneous and heterogeneous fields will be considered to assess the role of ecological refugia in providing accompanying ecosystem services such as pollination, pest-control, wildlife habitat and plant diversity to producers.

Objective 3: Producer Adoption

Due to delays surrounding COVID-19, surveys of PARA producers’ willingness to adopt wildlife friendly farming techniques will be prepared and brought to the Precision Agriculture Research Association annual meeting on December 3, 2021. However, in the summer of 2021, we were able to conduct and video a long form interview with producers Paul and Gary Broyles about the benefits of precision agriculture technology and on farm experimentation. Their interviews will be discussed with all of the producers at the PARA meeting this December and a link to the video can be shared for this final report. In addition, amoeba diagrams of producer perceptions of on-farm biodiversity and ecosystem services will be prepared and completed in spring 2022. Results were shared at the Montana Organics Association, Precision Agriculture Research Association and Ecological Society of America annual meetings in 2020 and 2021. These results are quite promising and were received with a lot of enthusiasm by producers at both the Montana Organics Association annual conference and Precision Agriculture Association annual meeting in 2020. I believe that this important work on the effects of habitat heterogeneity on crop yield and biodiversity can be applied for the benefit of producers and habitat quality alike. As a result, the 2021 results from this project will be shared and discussed at the annual MOA, PARA and ESA meetings in the coming year.

Research results and discussion:

First, we found that production fields with an ecological refuge had higher plant species richness and plant diversity than fields without a refuge for two of three farms. 

 

 

 

 

Fields with an ecological refuge on the Bailey and Broyles farms had significantly higher plant species richness than the control fields that had no refuge.

 

 

 

 

 

 

Second, we found that plant species richness declined significantly with distance from the refuge on both the Broyles and Bailey farms.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

However, the field with a refuge on the Norgaard farm had lower plant species richness than the control field. Unlike the other two farms, plant species richness increased with distance away from the refuge. One explanation may be that the control field has higher species than the refuge at this farm because Norgaard's refuge was a bare patch of alkaline land that is in the process of being restored. We would expect the trend in plant species richness to change as the refuge is restored and plant diversity is enhanced within the refuge.

 

 

 

 

We found that plant diversity also decreased with distance from the refuge for Bailey and Broyles farms,  increased with distance from the refuge for the Norgaard farm. These results were the same for 2020 and 2021 data.

                                 

                              Bailey p-value = 0.0131                                        Broyles  p-value = 0.0107                              Norgaard p-value = 0.0064

 

 

 

 

As a basic proof of concept, we also found that despite the small size of the refugia, they are able to host higher plant species richness than the crop field. The lefthand figure shows actual field observations of higher plant species richness in the refuge. The figure on the right shows a Kriging interpolation that predicts higher plant species richness in the refuge than in the crop field.

 

 

 

 

Furthermore, we found that contrary to producer's fears, there was higher nonnative plant species richness in the crop field than in the refuge. We also found that native plant species richness was higher in the refuge than in the crop field. This indicates that ecological refugia are not sources of weeds, but are sources of native plant diversity in agricultural landscapes.

 

Transitioning to insect analysis, we found that insect species richness decreased significantly with distance from the refuge for all 3 farms.

 

When we broke insect diversity down, we found that more beneficial insects were found in the refuge than in the field without a refuge.

For the Bailey farm, individual insect counts from the insect orders Hymenoptera, Araneae and Odanata were significantly higher in the field with a refuge. These orders are generally associated with pollinators, and pest predators in agricultural settings. This means that more beneficial insects are associated with refugia than fields without refugia.

 

 

 

 

For the Broyles farm, insect counts from the insect orders Diptera and Hymenoptera were significantly higher in the field with a refuge than the field without one. These orders are typically associated with beneficial pollinators. Conversely, the orders Hemiptera and Orthoptera were significantly higher in the field without a refuge. These orders are typically associated with agricultural pests like aphids and grasshoppers. These results suggest that refugia host insect pest predator and serve as habitat for beneficial insects in agricultural landscapes.

 

 

 

 

Lastly, it is important to note that the results from the Norgaard farm were not necessarily consistent with the other farms. You can see that plant species richness was actually higher in the field than in the refuge and that beneficial insect versus pest insect data was inconsistent. The reversal of trends on the Norgaard farm may be explained by two different factors. The first factor is a management difference. The Norgaard farm is managed by an organic producer so there is very high diversity in the crop field from weeds, cover crops and volunteers. The second factor is a difference in timescales. The refuge at the Norgaard farm is newly planted and was converted from bare, alkaline soil rather than a pre-existing natural habitat like the other farm refugia. This experiment in restoring a small patch habitat should show interesting results about how plant and insect diversity change over time as the area recovers.

 

The seed predation results differed from farm to farm. The Bailey farm showed two benefits of ecological refugia. There was higher weed seed predation in the field with a refuge than the field without one. There was also lower crop seed predation in the field with a refuge than the field without one. However, the Broyles farm had higher crop seed predation in the field with a refuge than the control field. Weed seed predation was not significantly different between field types. The Norgaard farm showed higher overall seed predation in the field with a refuge than the field without one. Both Broyles and Norgaard results may be due to the drought conditions and abundance of grasshoppers found in both fields in the summer of 2021. 

The grain analysis results from 2021 were obtained from Broyles and Norgaard winter wheat samples. However, barley samples from the Bailey farm were taken but could not be analyzed due to lack of grain formation. 

For the Norgaard farm, we found that winter wheat moisture content was significantly higher in the field with a refuge. However we found that winter wheat protein, iron and total polyphenol content was significantly higher in the field without a refuge.

 

 

 

 

 

 

For the Broyles farm, we found that winter wheat protein andiron content were significantly higher in the field with a refuge. However we found that winter wheat moisture and total polyphenol content were significantly higher in the field without a refuge.

 

 

 

 

 

 

 

For the Norgaard farm, within the field with a refuge, we found that winter wheat moisture and protein content significantly declined with distance from the refuge. However we found that winter wheat iron and total polyphenol content significantly increased with distance from the refuge. 

 

 

 

 

For the Broyles farm, within the field with a refuge, we found that winter wheat moisture protein, and total polyphenol content significantly increased with distance from the refuge. However we found that winter wheat iron content significantly decreased with distance from the refuge. 

 

 

 

 

 

For the Norgaard farm, winter wheat moisture content was significantly higher in the field with a refuge. However, winter wheat protein content was significantly higher in the field without a refuge. Grain total polyphenols were significantly higher in the field without a refuge. Winter wheat iron content was not significantly different between field types.

For the Broyles farm, the trends were reversed, as winter wheat moisture content was higher in the field without a refuge (though not significantly) and protein content was significantly higher in the field with a refuge. Similar to the Norgaard farm, winter wheat total polyphenols were significantly higher in the field without a refuge. However, grain iron content was significantly higher in the field with a refuge.

                              Iron p-value = 0.01072
                              Polyphenol p-value = 0.003243. 

 

Economic Analysis Results:

 

For the Broyles farm, we assessed the economic aspect of ecological refugia by conducting an analysis with 2019 precision agriculture yield data. First, we broke down the crop field into 20-meter buffers (pictured on the left) and analyzed yield within each 20-meter buffer from the refuge (which is the blank white gap between the buffer zones).

 

 

 

We found that yield significantly declined with distance from the refuge. On average, yield decreased about 1.2 bushels/acre with every 20 m farther away from the refuge. However, we acknowledge that this trend could be due to other variables such as topography or soil type variation. This was a preliminary analysis of one field that we will replicate using more years of data from all three farms. These economic analyses will will be used to inform a final net return analysis of ecological refugia in production fields.

 

 

 

 

 

The next steps of this project will be to identify summer 2021 winged insect and carabid beetle samples during the winter of 2021. Economic analyses for all three farms will be finished by spring 2022 using 2020 harvest data. The extended end date for this project is August 31, 2022. By this date, we will have analyzed how plant species richness, insect species richness and seed predation relate to crop yield and crop quality. By this time, we will also have assessed habitat spatial heterogeneity (using a vegetative cover type index) and mean regional crop diversity (using Cropscape) to test the hypothesis that heterogeneity in vegetation structure provides a greater variety of habitat for wildlife. The final analysis of ecological and production tradeoffs will inform producers about how ecological refugia affect biodiversity and crop production on their farms and guide management practices towards agri-environment schemes.

You can continue to find updates on this project at the following StoryMap link: https://arcg.is/1SKLPP 

Participation Summary
4 Farmers participating in research

Educational & Outreach Activities

3 Consultations
1 Curricula, factsheets or educational tools
1 Tours
3 Webinars / talks / presentations
6 Workshop field days

Participation Summary:

5 Farmers
2 Ag professionals participated
Education/outreach description:

Our agroecology lab at MSU has been conducting on-farm precision experimentation (OFPE) with producers from the Precision Agricultural Research Association (PARA) of Montana since 2015. PARA functions as a Participatory Research Network for farmer-to-farmer education. We visit each producer multiple times throughout the year to tour, consult and conduct fieldwork on their farms. The three producers in this project (Gary Broyles, Ole Norgaard and Casey Bailey) will share this year's results with the other 42 producers in PARA and train fellow members to utilize technologies and generate tailored data for their own farms at the annual PARA meeting in November. We will also present a workshop to equip Montana farmers with the tools for profit mapping their own individual fields and calculating the costs and benefits of taking certain areas out of production.   

Project Outcomes

2 Farmers changed or adopted a practice
1 Farmers intend/plan to change their practice(s)
1 Grant received that built upon this project
Did this project contribute to a larger project?:
Yes
1 New working collaboration
Project outcomes:

This project offers an incentive to maintain uncropped, biodiverse areas within farmer's fields as refugia. We hope to show that refugia may not only result in the saved cost of seed, but offer non-monetary profits due to enhanced insect, plant and small mammal diversity. Refugia also contribute to higher quality of life for producers. Some have already commented on the enjoyment they receive from seeing wild animals and wild flowers on their property. 

 

Experimenting with farmland heterogeneity is especially pertinent to producers, since multifunction agricultural biodiversity has been identified as an important future research theme in sustainable agriculture and global food supply. This study aims to clarify the effects of habitat heterogeneity in agricultural ecosystems by quantifying yield and biodiversity responses. In regard to yield, farmers can profit from the use of precision agriculture and precision conservation technology to identify optimal crop areas, optimize nutrient inputs, and avoid economic loss. Farmers may also experience pest control benefits from on-farm biodiversity. Insects are estimated at saving producers approximately $4.5 billion/y in avoided crop damage in the United States alone. Furthermore, managing for heterogeneity increases pollinator populations, which have been shown to improve production of 70% of the most important crop species worldwide and influence 35% of global human food supply. Producers may also benefit from on-farm vegetative diversity, which has been shown to reduce soil and nutrient loss by more than 90% in a diversified corn-soybean system. Increased mammal diversity may also provide beneficial weed seed predation services. While habitat heterogeneity has been proven to provide financial and ecological benefits to producers, there are also possibilities when habitat conservation in farmland may reduce crop production by enhancing pests. This study aims to examine both the monetary costs and benefits as well as ecosystem services and disservices that accompany heterogeneity in agricultural systems in order to provide a management tool for producers that optimizes crop production and habitat creation in farmland

Knowledge Gained:

We continue to learn from our producers throughout the collaborative research process. This year we saw how On Farm Precision Experimentation can discourage producers by creating short term costs from "controls" or "0s". We are learning how to better design on-field experiments so they can minimize those costs for our producers while hopefully obtaining the data we need to maximize long term benefits. For example, two producers have agreed to plant a diverse cover crop mix or pollinator strips to benefit the pollinator communities on their farms. Though this is not the cheapest choice for producers, it may have positive outcomes for overall farm diversity and future yield.

Information Products

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.