What We Do
Our research combines large-scale observational studies across biogeographic regions, field experiments, functional and phylogenetic approaches, and advanced statistics and modeling to address environmental issues and to explore fundamental questions in ecology. We are broadly focused on two main themes: 1) Community assembly - mechanisms across local, landscape, and biogeographic scales; and 2) Global change biology - applying community assembly theory to environmental issues. We also explore other topics of interest including herbivory, disturbance, and plant hemiparasites
Integrating mechanisms across local, landscape, and biogeographic scales
A key challenge at the interface of ecology and conservation is to understand the mechanisms by which communities assemble and lead to the diversity observed in nature. In the Spasojevic lab, we integrate processes across multiple scales, from continental-scale biogeographic processes to local interactions among coexisting species, to better elucidate mechanisms of community assembly. Our approach focuses on using quantitative examinations of taxonomic, functional and phylogenetic diversity coupled with spatial and environmental data to elucidate the role of multiple interacting mechanisms.
Global Change Biology
Applying community assembly theory to environmental issues
Community assembly theory provides a powerful framework for understanding how multiple global change factors are changing plant communities and altering ecosystem function. A key goal of the Spasojevic lab is to integrate multiple ecological processes across different scales to understand key questions related to global change. We conduct this research using a combination of experiments, observational studies, and data synthesis and do research in alpine, dryland, and forest ecosystems.
Pinyon Flats rainfall manipulation experiment
We are examining how changes to the amount of rain in different seasons influences plant community dynamics and ecosystem functioning in a Pinyon-Juniper woodland. This system gets both summer and winter rain and our treatments include: Summer only receives ambient summer precipitation and has a roof during winter to exclude all winter rainfall; Winter only receives ambient winter precipitation and has a roof during summer to exclude all summer rainfall; Control receives both ambient summer and ambient winter and has no manipulations; Summer+ receives ambient winter precipitation and has water added during the summer; Winter+ receives ambient summer precipitation and has water added during the winter. The results of the first two years can be found in the link below. We are now collecting the 5th year of data and are running a seedbank study.
San Jacinto Forest Dynamics Plot
Forests play key roles in biodiversity maintenance and climate regulation. Globally, forests support over half of all described species and provide many valuable ecosystem functions and services such as timber, clear air, clean water, and carbon storage. However, forests worldwide are being threatened by habitat loss, drought , and changes in fire frequency, which have all resulted in losses to biodiversity and alterations to key ecosystem functions and services. Understanding and predicting how forests will respond to ongoing and pervasive changes to the environment is critical for biodiversity conservation and for the management and maintenance of ecosystem services. Our Forest Dynamics Plot on Mt. San Jacinto in Southern California will be part of the Smithsonian’s Forest Global Earth Observatory network. The overarching goal of this project is to conduct research on forest biodiversity and ecosystem functioning and to establish long-term monitoring of forest health in Southern California.
Niwot Ridge LTER project
As part of the Niwot LTER, Marko is collaborating with a great group of PIs and grad students to understand how early snowmelt influences biodiversity and ecosystem functioning in the alpine. In 2018 we initiated an experiment to manipulate growing season length by spreading a very fine layer of black sand on large (10x40m) plots at maximum snowpack at five sites. The black sand increases albedo and speeds melt by 5-15 days, depending on site. We have completed two years of data collection and are planning to continue these manipulations for 6-8 years to both identify shifts in limiting resources as well as the responses to those shifts in plant production, species composition, phenology, and woody plant demography. We are initiating work on how early growing season affects plant-pollinator interactions, in conjunction with shifts in plant phenology and on how structure-forming biota might affect climate exposure and create refugia.
Growing Season Length Experiment
Understanding which species will be able to disperse to new habitats in response to changing climate is critical for conservation. Here, using FIA data Erin is modeling seedling and adult distributions to try and understand which species are showing elevational or latitudinal shifts. Erin has found that 18 of 25 species are shifting north and these species tend to have animal dispersal syndromes.
Range shifts in Western Forests
Niwot Ridge LTER project
Jared is examining how the mechanisms driving the biodiversity-ecosystem function relationship (niche complementarity and mass ratio effects) should be expected to shift under environmental change scenarios. Using long-term monitoring data from the Niwot Ridge LTER Jared found that that mass ratio effects were the dominant mechanism by which biodiversity influenced NPP in the alpine, but that niche complimentarity became more important in years with hot dry summers.
Climate change alters the relative importance of Mass Ratio and Niche Complementarity effects
understanding vegetation responses to recent climate change
Climate change is inducing the rapid restructuring of vegetation globally, and particularly along elevational gradients in mountainous terrain. The Deep Canyon Transect, is a steep elevational gradient spanning an elevation gain of 2,438 meters over a distance of 16 kilometers and was previously sampled in 1977 and 2008. Tesa resampled this transect to understand how vegetation has responded to ongoing climatic changes.
Deep Canyon Transect
Using a Multi-scale Framework to Understand Variation in Plant Community Assembly Across Complex Landscapes
Niwot Ridge LTER project
AJ is investigating how the processes of plant community assembly vary across multiple spatial scales at the Niwot Ridge LTER. This involves using a spatially explicit sampling design that combines community composition surveys at multiple spatial scales with spatial and environmental data to infer variation in assembly processes. Specifically, AJ will investigate what drives landscape-scale differences among community types (topography and snow), among patches of the same community type (dispersal), among communities within a single community type (soils and microtopography), and within a community (species interactions and microenvironment).
Long term alpine plant responses to global change
Niwot Ridge LTER project
High alpine systems are experiencing a variety of rapid global changes and predicting how species will respond to these changes is a major challenge for conservation and management. Jon is leveraging a variety of long-term global change experiments at Niwot Ridge LTER to investigate whether we can use plant functional traits to help predict how species will respond to Nitrogen deposition, changing snow accumulation patterns, and warming temperatures. Overall, it looks like plant responses to global changes depend on their functional traits, meaning that we can likely use plant functional traits to help predict how alpine systems will change in the future.
Elevational range shifts in tropical alpine ecosystems
Climate change is expected to cause major shifts in plant species ranges towards the poles and higher elevations. However, as plants have begun shifting their ranges, several plant populations are following different trajectories. Because of this, factors such as how plants interact with each other must be considered to correctly make predictions about future plant species ranges under climate change. For this purpose, Sisi is using transplant experiments and open-top chambers in tropical mountain ecosystems, specifically in the Andes, to simulate the predicted elevational range shifts and increased temperatures that plant communities would be experiencing under climate change. She will be measuring how plant communities will be shaped under these conditions and the role of plant interactions in shaping those communities.