Key Findings

Key Findings

The Luquillo LTER has evolved through an iterative process of key conclusions found within each proposal (LUQ I-IV).  We initially focused on patch dynamics in one forest type (tabonuco forest) as a unifying theme (LUQ I).  In LUQ II we developed the concept of “ecological space” (see Waide & Willig 2012 for history) to describe how antecedent and current conditions influence the biota and biochemical dynamics responding to the disturbance regime.  In LUQ III we focused on detrital dynamics as our unifying theme, while expanding our studies to include all of the LEF, including life zones at elevations above tabonuco forest.  We studied ecosystem services in LUQ IV, extending our studies to urban and other zones at the base of the Luquillo Mountains. Three main key conclusions were found in LUQ I-III

1. Disturbance shapes the climatic, biotic, and biogeochemical characteristics of the Luquillo Mountains, but responses to disturbance are mediated by initial conditions and characteristics of the disturbance (Waide & Lugo 1992, Walker & Willig 1999, Brokaw et al. 2012). Thus, the effects of disturbance are contingent on previous disturbance events. Hurricanes exert their primary effects through canopy opening and organic matter deposition, in order of importance (Shiels & González 2014).   

2. Climate is a primary determinant of the distribution of biota and rates of biogeochemical cycling in the LEF (Barone et al. 2008, González et al. 2013). Long-term directional change in climate is taking place in the LEF, and rates of change are more rapid than previously realized.  Both models and empirical data suggest that rainfall is decreasing and temperature is increasing in the Luquillo Mountains (Scatena 1998, van der Molen 2010, Schaefer 2003, González et al. 2013). 

3. The interaction between changing climate and disturbance regime will result in ecosystems characterized by novel species compositions, with altered structures, biogeochemistry, and ecosystem services (Doyle 1981, Sanford et al. 1991, Covich et al. 1991, 1996, O’Brien et al. 1992,  Silver 1998,  Wang et al. 2002a, b, Erickson & Ayala 2004, Dodds 2006, Bouskill et al. 2013). Determining how these new ecosystems will develop and evolve under dynamic climate and disturbance regimes is a long-term theme of LUQ.

References:

      Barone, J. A., J. Thomlinson, P. A. Cordero, and J. K. Zimmerman. 2008. Metacommunity structure of tropical forest along an elevation gradient in Puerto Rico. Journal of Tropical Ecology 
      
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Bouskill, N. J., H. C. Lim, S. Borglin, R. Salve, T. E. Wood, W. L. Silver, and E. L. Brodie. 2013. Pre- exposure to drought increases the resistance of tropical forest soil bacterial communities to extended drought. The ISME Journal 7:384-394.

Brokaw, N. V. L., A. T. Crowl, A. E. Lugo, W. H. McDowell, F. N. Scatena, R. B. Waide, and M. R. Willig. 2012. A Caribbean Forest Tapestry: The Multidimensional Nature of Disturbance and Response. Oxford University Press, New York, New York.

Covich, A., A. T. Crowl, A. H. Johnson, D. Varza, and D. Certain. 1991. Post-Hurricane Hugo increases in atyid shrimp abundances in a Puerto Rican montane stream. Biotropica 23:448-454.

Covich, A. 1996. Stream biodiversity and ecosystem processes. Bulletin of the North American Benthological Society 13:294-303.

Dodds, W. K. 2006. Eutrophication and trophic state in rivers and streams. Limnology and Oceanography 51:671-680.

Doyle, T. W. 1981. The role of disturbance in the gap dynamics of a montane rain forest: an application of a tropical forest succession model in Forest succession. Springer New York.

Erickson, D. L., and G. Ayala. 2004. Hurricane-induced nitrous oxide fluxes from a wet tropical forest. Global Change Biology 10:1155-1162.

González, G., M. R. Willig, and R. B. Waide. 2013. Advancements in the understanding of spatiotemporal gradients in tropical landscapes: a Luquillo focus and global perspective. Ecological Gradient Analyses in a Tropical Landscape 54:245-250.

O'Brien, S. T., B. P. Hayden, and H. H. Shugart. 1992. Global climatic change, hurricanes, and a tropical forest. Climatic Change 22:175-190.

Sanford, R. L., Jr., W. J. Parton, D. S. Ojima, and D. J. Lodge. 1991. Hurricane effects on soil organic matter dynamics and forest production in the Luquillo Experimental Forest, Puerto Rico: results of simulation modeling. Biotropica 23:364-372.

Scatena, F. N. 1998. Climate change and the Luquillo Experimental Forest of Puerto Rico: assessing the impacts of various climate change scenarios. American Water Resources Association TPS 98:91- 96.

Schaefer, D. A., W. H. McDowell, F. N. Scatena, and C. E. Asbury. 2000. Effects of hurricane disturbance on stream water concentrations and fluxes in eight tropical forest watersheds of the Luquillo Experimental Forest, Puerto Rico. Journal of Tropical Ecology 16:189-207.

Shiels, A. B., and G. González. 2014. Understanding the key mechanisms of tropical forest responses to canopy loss and biomass deposition from experimental hurricane effects. Forest Ecology and Management 332:1-10.

Silver, W. L. 1998. The potential effects of elevated CO2 and climate change on tropical forest biogeochemical cycling. Climatic change 39:337-361.

Van der Molen, M. K., H. Vugts, L. A. Bruijnzeel, F. N. Scatena, R.A. Pielke Sr., and L. J. M. Kroon. 2010. Meso-scale climate change due to lowland deforestation in the maritime tropics in L. A. Bruijnzeel, F. N. Scatena, L. Hamilton, editors. Tropical Montane Cloud Forests. Cambridge University Press.

Waide, R. B., and A. E. Lugo. 1992. A research perspective on disturbance and recovery of a tropical montane forest. Pages 173-190 in J. G. Goldammer, editor. Tropical forests in transition: ecology of natural and anthropogenic disturbance processes. Berkhauser-Verlag, Basel, Switzerland.

Waide, R. B., and M. R. Willig. 2012. Conceptual overview disturbance, gradients, and ecological response. Pages 42-71 in N. V. L. Brokaw, A. T. Crowl, A. E. Lugo, W. H. McDowell, F. N. Scatena, R. B. Waide, and M. R. Willig, editors. A Caribbean Forest Tapestry: The Multidimensional Nature of Disturbance and Response. University Press, Oxford.

Walker, L. A., and M. R. Willig. 1999. An introduction to terrestrial disturbance. Pages 1-15 in L. A. Walker, editor. Ecosystem of the World 16: Ecosystems of Disturbed Ground. Elsevier Science, Amsterdam, Netherlands.

Wang, H., C. S. Hall, J. Cornell, and M. P. Hall. 2002a. Spatial dependence and the relationship of soil organic carbon and soil moisture in the Luquillo Experimental Forest, Puerto Rico. Landscape Ecology 17:671-684.

Wang, J., J. D. Cornell, C. A. S. Hall, and D. P. Marley. 2002b. Spatial and seasonal dynamics of surface soil carbon in the Luquillo Experimental Forest, Puerto Rico. Ecological Modeling 147:105-122.