Noel Michelle Holbrook

Noel Michelle Holbrook

Faculty Project: The Contribution of Stem Water Storage to the Water Balance of "Palo Borracho" along a Rainfall Gradient in Northwestern Argentina: Morphological Plasticity and Physiological Performance of Arid Zone Trees
Faculty Project: Cavitation Reversal in Tropical Dry Forest Trees: Linking Leaf Hydraulic Properties with Patterns of Embolism Repair – Santa Rosa National Park, Costa Rica
Faculty Project: Puerto Rico Winter Institute 2007

The Contribution of Stem Water Storage to the Water Balance of "Palo Borracho" along a Rainfall Gradient in Northwestern Argentina: Morphological Plasticity and Physiological Performance of Arid Zone Trees

A collaborative research sponsored by DRCLAS with University of Buenos Aires laid groundwork for significant and sustained scientific interactions between Harvard and the laboratory of Guillermo Goldstein at the University of Buenos Aires. Including students from both universities, a full annual cycle of measurements and experiments will result in the first field study of water storage in Chorisia insignes, a tree known locally as palo borracho and native to Argentina, Paraguay and Bolivia. C. insignes is cultivated as an ornament tree in parks and along the roads, not only in Latin America but worldwide. In addition, the silky white floss of the fruits and the soft wood are used by local peoples. The key element for this study is that C. insignes exhibits morphological plasticity related to water availability, making it an excellent model system for understanding the adaptive significance of succulent stems in tropical and subtropical ecosystems subject seasonally to shortage of soil water. The goal is to quantify the ways in which water reserves contribute to photosynthesis and the physiological and biomechanical integrity of this iconic tree of the Argentine Chaco. Research is conducted in northwestern Argentina at five studies sites along a rainfall gradient, documenting key aspects of the physiology, phenology, and stem structure of ten of C. insignes during the year. The successful outcome of this study will be to augment the understanding of the functioning of the Chaco ecosystem, while allowing for testing of general hypotheses regarding the contribution of stem water reserves to arid zone trees. The greater understanding of the survival strategies of the tree will help develop an appreciation for nature and biodiversity.                       

Participating Harvard Faculty: Noel Michele Holbrook, Professor of Biology and Charles Bullard Professor of Forestry, Department of Organismic and Evolutionary Biology
Collaborators: Guillermo Goldstein, Professor, University of Buenos Aires                                                  

Collaborating Institutions:  University of Buenos Aires

Cavitation Reversal in Tropical Dry Forest Trees: Linking Leaf Hydraulic Properties with Patterns of Embolism Repair – Santa Rosa National Park, Costa Rica

With support from a DRCLAS faculty grant, Professor Missy Holbrook is looking at questions concerning the transport of water in plants. Plants “pull” water from the soil and supply it to their leaves due to the negative pressures generated by the curvature of air: water interfaces at the sites of evaporation in leaves. While this mechanism allows trees to transport hundreds of gallons of water each day, it threatens their primary supply-line due to the fact that water at pressures <0 is in a metastable state and thus at risk of the spontaneous conversion to the gas phase in a process known as cavitation. A number of laboratory studies suggest that at least some species have evolved the ability to reverse cavitation and to refill embolized conduits. Such repair capacity clearly must entail some costs and/or constraints as cavitation remains a significant impediment to the vascular system of plants and its avoidance a major factor guiding the evolution of wood structure. Professor Holbrook’s research examines the extent to which embolism repair occurs among co-occurring trees growing in Santa Rosa National Park in northwest Costa Rica and explores the costs and constraints associated with different strategies of embolism management.

Participating Harvard faculty: Noel M. Holbrook, Professor of Biology and Charles Bullard Professor of Forestry, Department of Organismic and Evolutionary Biology, Harvard University

Collaborating Institutions: Santa Rosa National Park, Costa Rica

Puerto Rico Winter Institute 2007

Puerto Rico Winter Institute 2007: Water and Environment: from Plants to Landscapes
January 10-24, 2007

Faculty Lead: Noel Michelle Holbrook

The David Rockefeller Center for Latin American Studies, jointly with the University of Puerto Rico, sponsored a two-week Winter Institute in San Juan. In its third year, the Institute focused on "Water and Environment: from Plants to Landscapes." Each week, four professors, two from Harvard University and two from the University of Puerto Rico, co-taught a seminar on a topic related to this major theme. The goal of the Institute was to stimulate research, collaboration, and intellectual exchange between Harvard and key institutions of higher learning in Puerto Rico. Seminar participants included faculty and students from Harvard and Puerto Rican institutions. Made possible by the generous support of the Wilbur Marvin Foundation

Program Details

Week 1: Water flux through plants: cellular to whole-plant processes

Elvira Cuevas – Professor, Department of Biology, University of Puerto Rico
N. Michele Holbrook – Charles Bullard Professor of Forestry, Department of
Organismic and Evolutionary Biology, Harvard University
Ernesto Medina – Investigador Titular, Instituto Venezolano de Investigacions
Cientificas (IVIC) and Adjunct Professor, International Institute of Tropical Forestry
(IITF), USDA-Forest Service, Puerto Rico
Maciej A. Zwieniecki – Sargent Fellow, Arnold Arboretum, Harvard University

Plants are the principle biological interface between soil and air and thus play a key role
in the hydrologic cycle at a variety of spatial and temporal scales. The goal of this first
week of the PRWI is to present a comprehensive overview of physiological phenomena
that are responsible for plants’ ability to dynamically influence rates of water movement
from soil to atmosphere. Topics to be covered include the micro-hydrology of roots,
stems and leaves, hydraulic impacts on soil processes and nutrient availability, adaptation
to variations in moisture availability, and ecological processes and life history traits that
influence overall rates and patterns of water transport. Overall, the emphasis will be
physiological, although links to ecosystem level processes and evolutionary innovations
relating to plant water use will be discussed.

Week 2: Plants to landscapes: eco-hydrologic processes and systems

Rafael Bras – Edward A. Abdun-Nur Professsor, Department of Civil and
Environmental Engineering, Massachusetts Institute of Technology
Paul Moorcroft – Associate Professor of Biology, Department of Organismic and
Evolutionary Biology, Harvard University
Carla Restrepo – Assistant Professor, Department of Biology, University of Puerto Rico

The second week of this year’s PRWI explores hydrologic processes operating at the
landscape scale from an ecological perspective. The goal will be to understand how
physical and biological processes controlling the movement of water influence ecological
interactions and long term ecosystem dynamics and hydrologic function. Topics to be
covered include: scaling from plants to ecosystems, regional-scale eco-hydrology, the
dynamics of the biosphere-atmosphere-hydrosphere interaction, and the geomorphology
of tropical landscapes.

People Taxonomy

Faculty Grant Recipient?