Research

Our research emphasizes questions that have strong theoretical implications for how biological systems work across multiple scales and directs application towards overcoming sustainability challenges. Most of our work uses sensor technology, remote sensing, field surveys, and numerical modeling techniques to generate multiple lines of evidence in answering questions. Our research has generally focused on the relationships between the carbon cycling, hydrologic cycling, energy partitioning, and biodiversity in dryland ecosystems across a diversity of land uses. We have explored these relationships both in terms of understanding carbon cycle responses to precipitation variability, and the role of vegetation for mitigating urban heat islands, and trade-offs in ecosystem services from high temperature agriculture. Together we aim to understand interacting sustainability trade-offs associated with natural, urban, and agricultural ecosystems across regional landscapes.

Much of my work is collaborative and I value opportunities to work with researchers from other disciplines, institutions, and nations. I also like to analyze data for as many uninterrupted hours as possible.

Currently the lab has three main thrusts:
    -- the role of vegetation in urban ecosystem resilience to climate changes
    -- aridland carbon and nitrogen trace gas emission responses to climate change and exotic invasions
     -- agricultural sustainability in southern California

Coupled Carbon and Nitrogen Cycling in High Temperature Drylands

My research on ecosystem responses to precipitation variation is directed towards developing and testing new processes and parameterizations for the land surface components of earth systems models (for example the Community Land Model by the National Center for Atmospheric Research). A major challenge for ecologists is scaling between organismal processes to landscape patterns. My lab investigates the reciprocal relationships between organisms and landscapes using field observation, experimental, numerical modeling approaches. I have characterized differences in contrasting patch types such as grass and tree or underneath plant canopy or the interplant spaces using networks of ecosystem sensors. I have shown differences in key plant functional types and water-use strategies – where a tree dominated ecosystem regulated water use more strongly through stomatal control, the grass dominated ecosystem regulated water use through leaf area control. Currently, we are examining how grass invasions into chaparral landscapes is both a response to climate changes and mediator of ecosystem feedbacks to climate.

Representative Citations

Liang LL, DA Grantz, and GD Jenerette. 2016. Multivariate regulation of CO₂ and N₂O pulse emissions from agricultural soils. Global Change Biology 22:1286-1298

Oikawa PY, C Ge, J Wang, JR Eberwein, LL Liang, L Allsman, DA Grantz, and GD Jenerette. 2015. Unusually high soil nitrogen oxide emissions influence air quality in high temperature agricultural region. Nature Communications 6:8753 DOI: 10.1038/NCOMMS9753

Eberwein JR, PY Oikawa, LA Allsman, and GD Jenerette. 2015. Carbon availability regulates soil respiration response to nitrogen and temperature. Soil Biology and Biochemistry 88:158-164

Jenerette GD and A Chatterjee. 2012. Soil metabolic pulses: water, substrate, and biological regulation. Ecology 93:959-966

Vegetation in Cities: Biogeography and Ecosystem Services image description

My research on urban ecosystem dynamics is directed towards understanding the role of vegetation on urban microclimates and ecosystem service production. We are in the process of documenting trajectories of biodiversity and ecosystem services within Los Angeles, CA, Phoenix AZ, across a network of southwestern U.S. cities, and globally. With three on-going NSF projects this research is going in many directions and rapidly maturing. I have on-going interests in extending these individual city approaches to regional and global syntheses of urbanization. Previous work at the global scale has evaluated patterns of land use change and urban water requirements in a changing world.
Within Los Angeles, CA region our group is studying the distribution of plant biodiversity within the urbanized landscape. We are currently assessing patterns of tree assemblages and evaluating patterns of phenological variation. We are also quantifying biodiversity in urban gardens and the services provided by these gardens. Both the tree and garden studies examine how the constructed biodiversity changes through time and begins identifying the trade-offs in ecosystem services provided by urban biodiversity. We are showing that vegetation as a climate adaptation tool shows a 5-fold magnitude of variation in effectiveness. Recently, we have shown a correlation between individual parcel surface temperatures with heat related health outcomes. Linking land cover decisions about vegetation may have important outcomes for building more climate resilient cities.

Representative Citations

Jenerette GD, SL Harlan, A Buyantuev, WL Stefanov, J Declet-Barreto, BL Ruddell, S Myint, S Kaplan, and X Li. 2016. Micro scale urban surface temperatures are related to land cover features and heat related health impacts in Phoenix, AZ USA. Landscape Ecology 31:745-760
Tayyebi A and GD Jenerette. 2016. Increases in the climate change adaption effectiveness and availability of vegetation across a coastal to desert climate gradient in metropolitan Los Angeles, CA, USA. Science of the Total Environment 548-549:60-71

Clarke LW, GD Jenerette, and A Davalia. 2013. The luxury of vegetation and the legacy of tree biodiversity in Los Angeles, CA. Landscape and Urban Planning 116:48-59

Jenerette GD, SL Harlan, W Stefanov, and C Martin. 2011. Ecosystem services and urban heat riskscape moderation: Water, green spaces, and social inequality in Phoenix, USA. Ecological Applications 21:2637-2651

Agricultural Sustainability
We are expanding our research into understanding resource and land use efficiencies in agricultural production with goals of increasing production while minimzing negative consequences. Our work here is directed to better understanding distributions and dynamics of urban agriculture. In Los Angeles we have documented immense diversity of garden plants. As a cautionary note, we have also shown many gardens contain high concentrations of many trace metals. Currently, we are taking a life-cycle approach coupled with intensive field measurements. We also are examining effects of larger scale agricultural practices in high temperature environments. We recently began a five year project examining life-cycle consequences for Sorghum production and testing new pulse ecosystem physiological theories. This work has led to new plant-soil models of carbon exchange and has documented through several approaches the potentially high rates of N trace gas emissions that can influence regional air quality.

Representative Citations

Clarke LW, GD Jenerette, and DJ Bain. 2015. Urban legacies and soil management affect the concentration and speciation of soil metals in Los Angeles community garden soils. Environmental Pollution 197:1-12

Clarke LW and GD Jenerette. 2015. Biodiversity and direct ecosystem service regulation in the community gardens of Los Angeles, CA. Landscape Ecology 30:367-653

Oikawa PY, GD Jenerette, and DA Grantz. 2015. Offsetting high water demands with high productivity: Sorghum as a biofuel crop in a high irradiance arid ecosystem. Global Change Biology Bioenergy 7:974-983