Postponed and Rescheduled for October 7th

California Native Grassland Association GRASS Award Speaker Series

Join us for this season's GRASS Speaker Series showcasing the amazing work undertaken in California Grasslands by some of our Grassland Research Awards for Student Scholarship Winners.

Talks are on Tuesdays from 6 PM - 7 PM PST featuring a one 40-minute talk, or one or two 20-minute talks, with time for Q&A. 

Members: Free      Non-Members: $10       Non-Member Students: Free with Student ID

Title: Community assembly along environmental niche gradients: contrasting patterns of functional convergence and divergence in California coastal grasslands

Speaker: Ernesto Chavez-Velasco

October 7, 2025 6:00 PM to 7:00 PM

Abstract: Plant community assembly processes are often thought to be hierarchical and scale-dependent, with broad-scale environmental filters constraining the composition of local communities. Within local communities, ecosystem functions may be best predicted by the mass-ratio hypothesis, where the functions of dominant species drive ecosystem functions like productivity. Alternatively, the niche complementarity effect predicts that a diverse assemblage of functions among species drives productivity. I investigated how these hierarchical assembly processes shape communities at different spatial scales and how local assemblages affect productivity across three California coastal grassland sites spanning a ~1000 km gradient. At these sites, I measured community composition, standing biomass, four functional traits (plant height, specific leaf area, leaf dry matter content, and leaf lobedness), and estimated species’ environmental niches. To identify assembly mechanisms and link them to ecosystem function, I used null models to test for patterns of trait similarity (convergence) or dissimilarity (divergence) at different scales. My results suggested scale-dependent assembly patterns driven by species' environmental niches. At broad spatial scales, trait divergence indicated that plants were sorted by large-scale differences in aridity. Within sites, however, trait convergence suggested that local environmental filtering favored species with similar functional strategies that matched soil properties and precipitation. When assessing productivity, the traits of the most dominant species were the strongest predictors of standing biomass with functional diversity complementing productivity. My findings support a hierarchical assembly model where scale-dependent mechanisms select for species with particular traits, and the aggregated traits of these dominant species support ecosystem function. 

Bio: I recently completed my master's degree in Natural Resources at Cal Poly Humboldt where I researched commonly unused plant diversity in California grassland restoration projects. I completed my undergraduate degree from UC Santa Cruz in 2021, where I first gained research and restoration experience concerning California grasslands. Since 2019, I have been a restoration practitioner in Santa Barbara County and in Point Blue's Students and Teachers Restoring a Watershed Program in the Bay Area. Most recently, I was an assistant field botanist for CNPS in the North Coast bioregions. I also volunteer and participate in regional prescribed burn associations where I can apply "good fire" in our grassland ecosystems. I enjoy sharing my genuine appreciation and love for California's grassland systems for their often-overlooked beauty and their vital role in supporting the state's diverse flora and fauna. 

Contact Justin Luong (jluong4@ucsc.edu) with any questions.

CNGA 2024 GRASS Award Speaker Series 2025 Schedule (Tuesdays, 6 - 7 pm)

• September 9 - Katherine Brafford (UCD)
• September 16 - Andrea Nebhut (Stanford); Deborah Ayala (Texas A&M)
• October 7 - Ernesto Chavez-Velasco (Cal Poly Humboldt)
• October 14 - Jessica Solis (SFSU)
• October 21 - Sophie Noda (UCD) 
• October 28 - Lauren Glevanik (UCLA)

Help Support Student Research - Donate to the GRASS Program

CNGA's GRASS Program: 

• Focuses student research on important grassland-related questions. 
• Inspires students to become more involved in California Grassland Conservation and Restoration. 
• Trains future employees for your agency or company.
• Creates advocates for California Grasslands