Associate Professor (on leave F '13)
Research | Articles
Book Chapter | Peer-reviewed Abstracts
Ph.D. Forest Resources, University of Minnesota
M.S. Botany, University of Vermont
B.S. Biology, Universidad de Los Andes, Bogota, Colombia
Department of Biology
Pontificia Universidad Javeriana
Department of Forest Resources
University of Minnesota
Community Population Ecology Lab
Pontificia Universidad Javeriana
Pontificia Universidad Javeriana
Instructor of Community Ecology
Universidad de Los Andes, Bogota, Colombia
BIOL 2: Organismal and Population Biology
This is a team taught introductory course in the study of organisms, emphasizing morphology, physiology, behavior, ecology, and evolution of whole organisms and populations.
BIOL 036: Ecology
The distribution and abundance of organisms in nature through an understanding of how they interact with their abiotic and biotic environments. Students will gain ecological literacy and practice by studying processes that operate within and between hierarchical levels or organization such as individuals, populations, communities, and ecosystems. All this knowledge will be applied to understand the current global changes occurring in nature as a result of human activities.
BIOL 137: Biodiversity and Ecosystem Functioning
Can the current decline in global biodiversity alter the functioning and stability of ecosystems? The answer to this question can be reached by evaluating the ecological consequences of changing patterns in biodiversity, through either extinction or addition of species. We will review the relative or specific role of extrinsic factors (climate, disturbance, soils, etc.), genetic, taxonomic, and functional diversity in ecosystem functioning using both experimental and natural evidence.
My research focuses on understanding the processes controlling the structure and dynamics of temperate and tropical forest communities and ecosystems. It is based on how species-specific variation in growth, survival, reproduction, morphology, and physiology, are influenced by the physical environment and by interactions with other individuals. The research requires a broad understanding of ecological processes such as carbon, water and nutrient cycling, light use, above and belowground productivity, biodiversity and their associated feedback mechanisms. The approach I take in addressing research questions is broadly comparative and I use experimental and analytical methods for integrating physiological and ecological processes across individuals, communities and ecosystems.
The following are some of my current projects:
- Maintenance of Positive Carbon Budget in Understory Seedlings with Long Leaf Life Span (with Dr. Kaoru Kitajima, University of Florida, Gainesville and Smithsonian Tropical Research Institute, Panama)
- Stoichiometry of the soil-plant-atmosphere continuum: a long-term ecological field research curriculum for biology undergraduates (with members of Bio 36 Ecology 2002, 2003, 2004 and Bio 137 seminar 2004)
- Seasonal variation in light availability and canopy structure of invasive Norway maple and native sugar maple and American beech (with Ryan Esquejo '05)
- Experimental approach to the removal of an invasive species: the case of Japanese knotweed (with Michael DeFillipo '04, Kirsten Vannice '04 and Bradley String - Biology Teacher from Ridley High School)
- Digital conversion of Samuel Palmer's drawings of local flora and plant specimens of the Biology department herbarium collection (with Laura Carballo '05, Bpantamars Phadungchob '05 and Rachel Wallace, Biology laboratory instructor)
- Intra and interspecific root competition: trade-offs or game theory? (with Erik J. Elwood '04)
- Evaluation of geographical information system to study growth and distribution of English Ivy in the Crum woods of Swarthmore College (with Aja Peters-Mason '04 and Elisha Gaston '03)
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- Reich, et. al. 2008. Ecology Letters. In press.
- Reich, P.B., M.G. Tjoelker, J-L. Machado and J. Oleksyn. 2006. Universal scaling of respiratory metabolism, size and nitrogen in plants. Nature. 439: pp. 457- Reprint
Commentary in News and Views: Hedin, L.O. 2006. Plants on a different scale. Nature 439:399-400 Reprint
- Machado, J-L. and P. B. Reich. 2006. Dark respiration rate increases with plant size in saplings of three temperate tree species despite decreasing tissue nitrogen and nonstructural carbohydrates Tree Physiology 26:915-923 Reprint
- Parrado-Rosselli, A., J-L. Machado. and T. Prieto-Lopez. 2006. Comparison between two methods for measuring fruit production in a tropical forest Biotropica 38:267-271 Reprint
- Machado, J-L., M.B. Walters, and P. B. Reich. 2003. Below-ground resources limit seedling growth in forest understories but do not alter biomass distribution. Annals of Forest Research 60:319-330 Reprint
- Frelich, L.E., Machado, J.-L. and Reich, P.B. 2003. Fine-scale environmental variation and structure of understorey plant communities in two old-growth pine forests. Journal of Ecology 91:283-293 Reprint
- Reich, P.B., Buschena, C., Tjoelker, M.G., Wrage, K., Knops, J., Tilman, D. and Machado, J.-L. 2003. Variation in growth rate and ecophysiology among 34 grassland and savanna species under contrasting N supply: a test of functional group differences. New Phytologist 157:617-631 Reprint
- Machado, J.-L., and P. B. Reich. 1999. Evaluation of several measures of canopy openness as predictors of photosynthetic photon flux density in deeply shaded conifer-dominated forest understory. Canadian Journal of Forest Research 29:1438-1444. Reprint
- Machado, J-L. and M. T. Tyree. 1994. Patterns of hydraulic architecture and water relations of two tropical canopy trees with contrasting leaf phenologies: Ochroma pyramidale and Pseudobombax septenatum. Tree Physiology 14(3):219-40. Reprint
- Coley, P. D., T. A. Kursar and J-L. Machado. 1993. Colonization of tropical rain forest leaves by epiphylls: the effects of site and host plant leaf lifetime. Ecology 74(2):619-23. Reprint
- Wright, J. S., J-L. Machado, S. S. Mulkey and A. P. Smith. 1992. Drought acclimation among tropical forest shrubs (Psychotria, Rubiaceae). Oecologia 89: 457-63.
- Mulkey, S. S., A .P. Smith, S. J. Wright, J-L. Machado and R. Dudley. 1992. Contrasting leaf phenotypes control seasonal variation in water loss in a tropical forest shrub. Proceedings National Academy Sciences, USA. 89: pp. 9084-88 Reprint Commentary in News and Views: Moore, P.D. 1992. A leaf for all seasons. Nature 360:110-111 Reprint
- Tyree, M.T., J. Alexander, and J.-L. Machado. Loss of hydraulic conductivity due to water stress in intact juveniles of Quercus rubra and Populus deltoids. Tree Physiology 10:411-415 Reprint
- Cavelier, J., J-L. Machado, D. Valencia, J. Montoya, A. Laignelet, A. Hurtado, A. Varela, and C. Mejia. 1992 Leaf demography and growth rates of Espeletia barclayana Cuatrec. (Compositae), a caulescent rosette in a Colombian Paramo. Biotropica 24(1): 52-63. Reprint
- Tyree, M. T., D. A. Snyderman, T. R. Vilmont and J-L. Machado. 1991. Water relations and hydraulic architecture of a tropical tree (Scheflera morototoni): data, models and a comparison to two temperate species (Acer saccharum and Thuja occidentalis). Plant Physiology 96: 1105-13
- Hogan, K. and J-L. Machado. 2002. The light environment in tropical forests: biological implications and measurements. In: Neotropical Forest Ecology and Conservation. Eds. M. R. Guariguata & G. H. Kattan. Agroamerica Press, San Jose, Costa Rica (written in Spanish). pp,. 119-144 Book Review
- Zagt, R.J. J.-L. Machado, and P.B. Reich. 1997. Distribution and demography in relation to light and size for seedlings of three Guyanese tropical rain forest species. In: Tree Demography in the Tropical Rain Forest of Guyana. Ed. R.J. Zagt. Tropenbos-Guyana Series 3. Tropenbos-Guyana Programme, Georgetown, Guyana. ISBN 90-393-1741-0, pp. 158-203 Abstract
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Peer-reviewed Abstracts (* indicates Undergraduate Students)
- The impact of white-tailed deer on tree regeneration and plant invasions in an eastern North American forest fragment. With Lauren Fety*, Keefe Keeley*, Bryan Lantz*, Rachel Collins and Rachel Merz Society for Conservation Biology , San Jose, California. June 24 - 28, 2006
- Leaf life span and leaf age effects on photosynthetic rates in shade vs. gap-grown seedlings of five neotropical shade tolerant trees. With Carla Stefanescu, Joseph Wrigth and Kaoru Kitajima Ecological Society of America, Montreal, Canada August 6 - 12, 2005
- Seasonal variation in the understory light availability and canopy structure of invasive Norway maple and native sugar maple and American beech. With Ryan Esquejo* Ecological Society of America , Montreal, Canada. August 6 - 12, 2002
- Surprising patterns of dark respiration, tissue nitrogen, and biomass distribution of saplings of three tree species in relation to plant size and understory light regime. With Peter B. Reich Gordon Research Conference: Metabolic Basis of Ecology, Bates College, Lewiston, ME. July 4 - 9 2004
- Secondary succession in Mountain Forest of the Central Cordillera in Colombia: Changes in Structure and Composition of tree species. With Juliana Monsalve* Association for Tropical Biology, Panama City, Republic of Panama. July 29 - August 3, 2002
- Fruit Production of a terra firme forest in the Colombian Amazon region: A comparison between traps above the forest floor and direct observation at the canopy level. With Tatiana Prieto-Lopez* and Angela Parrado-Roselli. Association for Tropical Biology, Panama City, Republic of panama. July 29 - August 3, 2002
- In deeply shaded forest understories, belowground resource limitations decrease tree seedling growth but do not alter biomass allocation patterns and survival. With P.B. Reich and M.B. Walters. Ecological Society of America, Spokane, Washington, USA. August 8-12, 1999.
- Spatial heterogeneity of light and nitrogen influences the distribution, density and growth of tree species in the understory of old growth white pine forest in northern Minnesota. With P. B. Reich. Ecological Society of America, Providence, Rhode Island, USA. August 10-14, 1996.
- Effect of irrigation on stomatal conductance in leaves of Psychotria species. With J.S. Wright, S.S. Mulkey and A.P. Smith. Ecological Society of America, Snowbird, Utah, USA. July 29 August 2, 1990.
- Fotosíntesis de dos fenotipos de hojas de un arbusto del sotobosque (Psychotria marginata) en el bosque tropical húmedo. With S.S. Mulkey, A.P. Smith, S.J. Wright. VII Congreso Científico Nacional, Universidad de Panamá, Republic of Panamá. November 1990.
- Estudio de la biología de poblaciones de Espeletia barclayana: 2. Dinámica foliar de las rosetas gigantes. With J. Cavelier, and D. Valencia.IV Congreso Latinoamericano de Botánica. Medellín, Colombia, June 1986.
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