Quantifying the effects of rangeland conversion on ecosystem functions: Linking land use systems to enhance farm profitability

Progress report for SW19-908

Project Type: Research and Education
Funds awarded in 2019: $349,327.00
Projected End Date: 12/31/2022
Host Institution Award ID: G255-19-W7500
Grant Recipients: UC Division of Agriculture and Natural Resources; Southern Illinois University
Region: Western
State: California
Principal Investigator:
Fadzayi Elizabeth Mashiri
University of California
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Project Information

Summary:

Conversion of land use in western states has increased over the past few years. In California, land use conversion is typified by depletion of rangeland to cropland and to urbanization. Between 1983 and 2008 for example, approximately 20,000 acres of prime rangeland were lost every year, mainly in the Central Valley region. While it is generally recognized that the rapid and widespread conversion of rangeland in the absence of sound conservation management would negatively affect ecosystem services, little is known about the full range of ecosystem changes (negative and positive) that occur on converted grounds of rangeland. This project will provide new insights into the essentials of ecosystem function changes during rangeland conversion to cropland. The project will also examine areas where rangeland functionality is weak in terms of soil health and develop extension and educational strategies to propose remediation/conservation measures that optimize rangeland ecosystem functions while maintaining and improving rangeland economic returns. We will use field data collection and computer modeling to evaluate the impacts of rangeland conversion on ecosystem functionality by comparing environmental quality data between rangeland and almond fields. We will set up and monitor three study sites, each with a rangeland site adjacent to almond orchards over a period of three years in collaboration with producers. We will collect field data to compare how infiltration, water flux, evapotranspiration (ET), soil nutrient content, runoff, soil microbial activity, soil carbon, plant production, plant, vertebrate and invertebrate species diversity, weed infestation, and soil compaction vary between rangeland and almond orchard sites. We will use modeling to evaluate the impacts of various conversion arrangements on hydrology at a watershed scale and explore the potential for linking and integrating production systems (i.e. mixed production approach) that can enhance overall ranch and farm profitability. We will also utilize the exiting literature to identify the institutional requirements for building resilience in rangelands, and apply those insights in analyzing the existing policies and institutional mechanisms for the governance of rangelands in the Central Valley of California. We will monitor the initial costs of converting rangeland to cropland and costs associated with maintaining recently established cropland given potential changes in ecosystem functions. We will monitor revenue per acre earned from recently converted cropland across various potential crops and compare to returns earned over time. Data collected will be used to construct a simulation model to test economic implications of conversion over time. We expect this project to lead to improved recommendations for conversion of rangelands in California and western states in order to help optimize environmental sustainability of rangelands. The project will provide science-based information to assist producers and ranchers determine which conservation practices/arrangements may work in their operations. The installation and results of this project will be incorporated into Extension and Outreach programming and other educational activities that will be released through a variety of outlets to inform producers and ranchers about the potential ecosystem changes that occur following conversion of rangelands.

Project Objectives:

The goal of this project is to provide insight into the basics of negative and positive ecosystem function changes during rangeland conversion to cropland. The project will propose measures to optimize rangeland ecosystem functions and will also explore the potential for establishing more integrated yet diversified agricultural production systems when land use changes occur to improve ecological sustainability. The specific objectives of this projects are to:

  1. Establish field study sites for educational demonstration of rangeland conversion to cropland;
  2. Evaluate the impacts of rangeland conversion on ecosystem functions (plant production, species diversity, soil condition and water budget) at field scales;
  3. Use modeling to evaluate watershed scale impacts of selected ecosystem functions of rangeland conversion to cropland;
  4. Synthesize the relevant literature to identify the institutional requirements for enhancing resilient rangeland systems, and assess the performance of existing institutional mechanisms for the governance of rangelands and their adequacy in promoting sustainable and resilient working landscapes.
  5. Evaluate the on-farm and off-farm costs of rangeland conversion to cropland and costs of maintaining converted cropland given potential changes in ecosystem functions over time.
  6. Develop appropriate farm and watershed level management strategies to optimize farm/ranch profitability and ecological sustainability; and
  7. Disseminate research findings to
Timeline:

The proposed project milestones and timeline are shown below.

Cooperators

Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Laurent Ahiablame (Educator and Researcher)
  • Dr. Kofi Akamani (Educator and Researcher)
  • Theresa Becchetti (Educator and Researcher)
  • Diane Bohna - Producer (Educator and Researcher)
  • Rose Marie Burroughs - Producer (Educator and Researcher)
  • Dr. Anthony Fulford (Educator and Researcher)
  • Dr. Phoebe Gordon
  • Paul Ichord - Producer
  • Pamela Kan-Rice (Educator and Researcher)
  • Dr. Fadzayi Mashiri (Educator and Researcher)
  • Dr. Daniel Sumner (Educator and Researcher)

Research

Hypothesis:

Land-use conversion from rangelands to orchards is associated with changes in ecosystem functions (soil organic matter, nutrient content, water infiltration, plant and insect diversity, and production) which in turn affect ecosystem services provided by landscapes.

This project focuses on analyzing ecosystem changes, both positive and negative and explores the potential to integrate land-use systems,  determine complementarity between mixed land uses, and evaluate watershed management strategies that can be adopted with the conversion of land use to optimize farm/ranch profitability.

The study investigates also the drivers behind the decisions for land-use change and the socio-economic implications of the changes.

Materials and methods:

Completed Activities:

Activity 1: Set up 3 study sites with rangelands in proximity to almond orchards (2 conventional and 2 integrated) with help from the collaborating producers. Samples are collected in three macroplots in each production system (rangelands and orchards) with four soil samples collected within each macroplot. In the orchard systems, two samples are collected within rows about half-point between a central tree within the macroplot and two neighboring trees; and two samples between rows of the almond trees to capture potential differences in the two microsites of the almond orchards.

Activity 2: Collected 84 soil samples to evaluate the effects of rangeland conversion on soil health and condition All soil samples were analyzed for nutrient availability, microbial activity, soil structure, and water budget.

Activity 3: Eighty-four soil cores were collected to measure seed bank plant diversity in the orchard and rangeland systems. The soil cores were broken up and seeded and grown in pots in a greenhouse. Plant species and their respective number were recorded.

Activity 4: We measured 2 seasons of herbaceous plant production and diversity at peak standing biomass in late spring on rangelands only. Data were collected using the harvest method in 20 randomly placed 30 x 30 cm quadrats within the 10 x 50m macroplots. Weed management in orchard systems where most weed treatment is preemergent created a scenario that limited the use of such data for comparison with rangeland data. As a result, we decided against collecting herbaceous plant biomass in orchards.

 

Ongoing and future activities:

Activity 5: Insect diversity samples were collected in 3 different ways every two weeks from spring to early summer of 2021. During every sampling period: 84 pitfall trap samples, 28 sticky trap samples, and 28 sweep net samples were collected. Insect Identification is still ongoing.  

Activity 6:  Use modeling to evaluate watershed-scale impacts of selected ecosystem functions of rangeland conversion to cropland. To get more accurate models we installed soil sensors to detect water movement through the soil profile, which we will use as ground-truthing data that can calibrate the hydrology models. The next steps include evaluating changes in water quantity and quality following the conversion at a watershed scale using the Soil and Water Assessment Tool (SWAT). Quantify the dynamic balance of water in the soil profile at the field and watershed scale.

Activity 7: Identify the institutional requirements for enhancing resilient rangeland systems, and assess existing policies and institutional mechanisms for the governance of rangelands. Based on the assumption that rangeland systems are complex social-ecological systems that are constantly exposed to multiple drivers of change to which they must build the capacity for adaptation and transformation in order to be sustainable, we will conduct a comprehensive review of the literature to identify the institutional requirements for the sustainable governance of rangeland systems.

Activity 8: Work to evaluate the costs of rangeland conversion to cropland and costs of maintaining converted cropland given potential changes in ecosystem functions over time will start this summer. We will use established methodologies (almond harvest, and forage production estimates) to assess the costs and returns on newly converted cropland for various crops typically grown in the study region.

Activity 9: As the data analysis continues and clear patterns emerge we will start developing more holistic farm and watershed level management strategies to optimize farm/ranch profitability and ecological sustainability.

Activity 10: Disseminate research findings to stakeholders through the popular press, social media, and public events working with collaborating producers.

Research results and discussion:

One of the almond research sites used a more integrated/regenerative orchard production system and was analyzed separately

A total of 84 soil samples were collected for each of the following: soil nutrient analysis, seed bank study, bulk density, and related properties. All soil samples have been processed for bulk density and related properties (porosity, estimated volumetric water content, estimated water infiltration rate, microbial respiration, and routine nutrient content (N, P, K).

The seed bank samples (84) were germinated in a greenhouse from December 2019 until spring 2020. We recorded plant species and numbers, and the approximate timing of plant emergence was recorded. We are using this data to calculate Simpson's Diversity Index.

Insect Diversity Data was collected from Spring 2021 using sticky traps, pitfall traps, and sweep nets- through the end of summer. We continue to process the samples - insect ID and count

The landscape hydrology assessment portion of the project started in the fall of 2021. So far we have installed soil sensors for field measurements and we are in the process of developing models. This work will continue into fall 2022 ideally through spring 2023.

Literature review to identify the drivers for land use conversion and institutional requirements for the sustainable governance of rangeland systems continues.

Work on economic assessment will start in summer.

Lab closures due to the COVID-19 pandemic slowed down or completely stopped some soil tests in 2020. Fieldwork was slowed down by the social distancing requirements which limited field crews in 2020. 

 

 

 

Research conclusions:

Preliminary results show higher nutrients, more respiration, plant diversity, and insect diversity in integrated almond orchards and rangelands and less in conventional orchards in general. For insect diversity - we are seeing evidence of seasonal changes in the species and numbers.

Regenerative ag field day

Participation Summary
5 Producers participating in research

Research Outcomes

No research outcomes

Education and Outreach

1 On-farm demonstrations
1 Published press articles, newsletters
3 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

310 Farmers participated
50 Ag professionals participated
Education and outreach methods and analyses:

Mashiri F.E (2022) Quantifying the Effects of Rangeland Conversion on Ecosystem Function: Soil Organic Matter, Plant Diversity, and Insect Diversity. Society for Range Management Conference February 21-25, 2022.

Mashiri F.E (2022) Measuring Ecosystem Function Across Farming Systems: Soil Organic Matter, Plant Diversity, and Insect Diversity. Regenerative Almond Field Day Feb 17, 2022, Regenerative ag field day

Theresa Becchetti and I were interviewed by the Public Policy Institute of California, discussing the associated land-use changes, impacts, and future management strategies. Some of our answers were informed by preliminary results from this ongoing research project- https://www.ppic.org/blog/could-rangeland-return-to-the-central-valley/ - This one is difficult to measure the number of people reached by blog - my LinkedIn post of the blog has 820 impressions.

 

 

Education and Outreach Outcomes

Recommendations for education and outreach:

With increasing acres of crop fields going fallow in California due to water shortages and the SGMA law - follow up research on best land rehabilitation practices, weed control etc

Key areas taught:
  • Not done yet
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.