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

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.