California State University Bakersfield
Welcome to the Webpage of
Dr. Anna L. Jacobsen
Plant Ecology and Evolutionary Biology
Dr. Jacobsen's Homepage Jacobsen Lab Research Methods Page Jacobsen Lab Publications
Current lab members:
Jackeline Medina Arreguin (undergraduate)
Laura Boots (graduate)
Jaycie Fickle (graduate) (CSUB CREST fellow 2018-2020)
Marta Percolla (graduate) (CSUB CREST fellow 2016-2018)
The Jacobsen lab in summer 2016 working to carefully excavate an intact long poplar root from a juvenile tree in our on-campus research plot:
Dr. Jacobsen, Marta, Jessica, Jackie, Jaycie, Catherine, Daniela, Emily, Alex (from foreground to background).
The combined Jacobsen and Pratt labs in January 2014:
Daniela, Marta, Justin, Courtney, Sam, Dr. Pratt, Dr. Jacobsen, Dr. Venturas (post-doc), Evan, Hayden, Jessica
Past lab members:
Mark Bersentes (CSUB Student Research Scholars Program 2011-2012)
Jaycie Fickle (CSUB Student Research Competition 2017 1st Place Undergraduate Presentation; CSUB Student Research Scholars Program 2017-2018)
Mark De Guzman
Marta Percolla (CSUB Student Research Scholars Program 2012-2013, Botanical Society of America Physiological Section Student Best Student Poster 2013)
Aaron Ramirez (CSUB Outstanding Graduating Senior in the College of Natural Sciences, Mathematics and Engineering 2008)
F. Daniela Rodriguez-Zaccaro (CSUB Outstanding Graduating Senior in the College of Natural Sciences, Mathematics and Engineering 2016, CSUB Student Research Program Poster Competition 3rd Place University-wide Undergraduate Winner 2015)
Catherine Sanchez (CSUB Biology Outstanding Graduating Senior 2018)
Jessica Valdovinos-Ayala (Ecological Society of America Physiological Ecology Section Student Travel Award 2015)
Robert Atwood (committee)
Genetic variation among populations of the Bakersfield cactus Opuntia basilaris var. treleasei, based on amplified fragment length polymorphisms.
Alex Baer (advisor)
(CSUB Student Research Scholars Program 2016-2017)
Xylem functional traits at different tree positions within Populus trichocarpa.
Aaron Baumgardner (committee)
(CSUB Crest Fellow 2018-2020)
Ecological effects of drought with a focus on its abiotic drivers: A case study examining southern California chaparral shrublands.
Mitchell Coleman (committee)
(CSUB Student Research Competition 2017 1st Place Graduate Presentation)
Factors affecting Atriplex polycarpa (Chenopodiaceae) seedling recruitment in invasive annual grasslands in the San Joaquin Valley of California: the role of residual dry matter and competition
Dawn Fetzer (MS Geology) (committee)
Study of Summer Lake, OR BB3-1 Core via biogeochemical molecular and isotopic analysis for paleoclimate reconstruction
Heather Keldgord (committee)
The distribution of sexes across a rainfall gradient in a subdioecious southern Californa chaparral shrub Rhus ovata S. Watson (Anacardiaceae).
Evan MacKinnon (co-advisor)
(CSUB School of Natural Sciences, Mathematics, & Engineering Outstanding Graduate Thesis 2013)
A trait-based approach to restoring southern California habitats invaded by the Mediterranean grass Bromus madritensis ssp. rubens (Poaceae).
Justin Martinez (advisor)
(CSUB Student Research Scholars Program 2013-2014, CSUB Graduate Student Research and Scholarship Initiative 2013-2014)
Hydraulics of different varieties of grapevine
Courtney Traugh (committee)
Stem and root xylem trade-offs in carbohydrate storage, water stress tolerance, and biomechanics or sprouting and non-sprouting chaparral species.
Dr. Martin Venturas (2014-2015)
High school students (REVS-UP Program):
Estevan Ramirez (teacher)
Jacobsen laboratory high school research participants in the REVS-UP Summer 2015.
Jacobsen laboratory high school student and teacher research participants in REVS-UP (left) and with other members of the Jacobsen and Pratt labs (right) in Summer 2014.
Some of our current lab research topics/projects include:
Examining xylem vessel network structure and function in woody plants using developmental and intra-organismal systems (NSF IOS-1252232)
Natural resource solutions for water-limited paired mountain/valley systems (CSUB CREST, NSF HRD-1547784)
Plant hydraulic structure and function
Plant hydraulic responses to extreme drought
Fire ecology of Mediterranean-type climate region shrubs
Community convergence among arid and semi-arid shrublands in Mediterranean-type climate regions
Jacobsen laboratory research summary
Plants transport water through specialized water transport cells. In flowering plants, these cells, called vessel elements, combine to form long multi-cellular jointed tubes termed xylem vessels. In the Jacobsen lab, we are working to understand the structure of these vessels at the cellular-level and at the tissue-level. We are particularly interested in examining the structure of the three-dimensional vessel network of woody plants (i.e. how vessels develop and connect with one another throughout the tissues of a plant). Additionally, we are examining how vessel structure relates to the hydraulic function of plants. Vessels have three-dimensional structure, including significant curvature of vessels and significant changes in diameter of vessels (even along the length of a single vessel). Species can vary greatly in the interconnectedness of the vessel network and the density and structure of pitting between adjacent vessels. Work in our lab to examine inter- and intra-specific patterns in vessel length has yielded particularly interesting and exciting results, especially since this trait has sometimes been called the "neglected dimension" of vessel structure! Many students in the lab have conducted research or are continuing to conduct research examining vessel structural traits, including measuring vessel pit traits, vessel diameter, vessel length, and connectivity of the vessel network. As a lab, we are working to combine data from different levels of xylem organization (cellular to tissue) to develop a model of the vessel network. We are also working to quantify other elements of xylem structure, such as fiber and parenchyma cell structure and abundance.
Nearly all of the research projects in the lab are based on the broad idea of how plants use and move water, especially in response to stress. Thus, all of the research projects in the lab measure plant hydraulic function in some way. The most common measures of plant hydraulic function that are completed in the lab include measures of xylem resistance to water stress induced cavitation and measures of hydraulic conductivity (transport efficiency). Additional information about our methods for these measures may be found here. These methods have been important research tools that have allowed us to examine how plants respond to water stress. Extreme drought in California over recent years has enabled us to use these methods to investigate many different plant species, communities, and ecosystems to understand the impacts of drought.
There are five Mediterranean-type climate regions globally and they are each dominated by evergreen, tough-leaved shrub species; California represents one of these regions. The evergreen shrubs in these regions respond to fire by resprouting from modified root structures, recruiting through fire-cued seed germination, or through a combination of these strategies. We are currently investigating hypotheses related to how the xylem structure of resprouting plants relates to differential recovery of species post-fire, including why some species tend to suffer massive mortality during the first few years of post-fire recovery while other species are more resilient. Additionally, fire can have a profound effect on community composition of Mediterranean-type shrub communities. Several long-term collaborative research projects are investigating plant species and community response to fire, particularly in response to additional stresses such as heavy browse or drought. This work is being conducted at field sites in several locations throughout southern California, including the San Gabriel and Santa Monica Mountains, as well as on Santa Catalina Island off the coast of Los Angeles, California, and in the Western Cape Region of South Africa.
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