Special Sessions
Sponsored by the Geomorphology Specialty Group
Association of American Geographers 103rd Annual Meeting
San Francisco, California, April 17-21.

Scale Matters 2: The role of fine-scale phenomena in landscapes

Paper Session 1527
Tuesday, 4/17/07, from 4:00 PM - 5:40 PM

Sponsorship(s):

Biogeography Specialty Group
Geomorphology Specialty Group

Organizer(s):

Bronwyn Sigrid Owen - Truckee Meadows Community College
Jake E. Haugland

Chair(s):

Jake E. Haugland

Abstract(s):

• 4:00 PM Author(s):
  *Duane A. Griffin - Bucknell University
  

  Abstract Title: Fine-scale geomorphic pattern and biodiversity.

  
  

  Ecological diversity at patch, landscape, and regional scales reflects interactions between individual organisms and abiotic constraints. Biogeographers and ecologists have long recognized the key role geomorphology plays in these interactions through their effects on microclimate, moisture and nutrients supplies, disturbance regimes, and migration and dispersal. Less-well appreciated are the implications of fine-scale.

  Keywords: biodiversity, geomorphology, biogeography, simulation model

  
  
• 4:20 PM Author(s):
  *Don L. Hankins - California State University - Chico
  

  Abstract Title: Prescribed Fire in Riparian Ecosystems: A Fine Scale Process.

  
  

  Fire has been used for millennia by indigenous peoples of California tomaintain and conserve patches of riparian ecosystems. Based on applied research utilizing seasonally prescribed fires, I have studied the effects of prescribed fires on riparian vegetation and small mammal and reptiles within the riparian corridor. The implementation of seasonally-timed prescribed burns allows for creation of a mosaic of burned and unburned vegetation. Within this mosaic I have observed an increase in cover by native vegetation. Additionally, the seasonal application of prescribed fire in the late fall yielded no significant effects to small mammal or reptile use of the burned sites. The implementation of such burning practices can be used to manage and conserve biodiversity within California's riparian ecosystems.

  Keywords: Prescribed fire, Conservation, Indigenous land management

  
  
• 4:40 PM Author(s):
  *Ophelia Wang - University of Texas
  Kenneth Young - University of Texas at Austin
  Rodrigo Sierra - University of Texas at Austin
  Milton Tirado - Herbario Nacional en Ecuador
  

  Abstract Title: Causes and consequences of heterogeneity in tropical rain forest: A multi-scale study from the Ecuadorian Amazon.

  
  

  Tropical rain forests are remarkable not only for their high number of species, but for their great spatial heterogeneity, associated with subtle topographic changes, legacies of past disturbances, and resulting habitat diversity andother place-to-place changes in forest structure and composition. This project documented the fine-scale patterns of trees and palms found on two one-hectare plots inventoried for all plants with woody stems >greater than 10 cm in diameter. Each of the two tree inventory plots had approximately 580-620 individuals and consisted of 180-220 species. The dominant genera included Virola, Eschweilera, Oenocarpus, Inga, Ocotea, Pouteria, Licania, and Micropholys. There is little overlap in the composition of dominant species compared to the Amazonian forests in Yasuní National Park about 150 km away in northeastern Ecuador, indicating different forest communities, species distribution, and possible species endemism in the study area. There appeared to be two or three different tree communities within each plot, suggesting spatial heterogeneity of species diversity and distribution even at scales of 10 to 40 m. The average percentage canopy openness and leaf area index of the two plots were 5.6 and 3.7, respectively, and some within-plot heterogeneity appeared to be associated with changes in light environment. Ongoing and planned research will attempt to use this fine-scale detail to generalize to larger areas of rain forest in the study region through the use of high and relatively coarse remote sensing products (Quickbird, Landsat ETM).

  Keywords: Biodiversity, Scale, Tropical forests

  
  
• 5:00 PM Author(s):
  *Kathleen A. Farley - San Diego State University
  Sheila M Palmer - University of Leeds
  Gervasio Piñeiro - Universidad de Buenos Aires, Argentina
  Esteban G Jobbágy - Universidad de San Luis, Argentina
  Marcelo D Nosetto - Universidad de San Luis, Argentina
  Robert B Jackson - Duke University
  

  Abstract Title: Streams as integrators of land use effects at the watershed scale: acidification following eucalyptus establishment in grasslands.

  
  

  Streams act as an integrator of the effects of landscape change within watersheds, and the differences between alternative land use systems are reflectedin concentrations of dissolved nutrients. We examined the effects of afforestation of grassland watersheds by sampling soils and stream water in eight paired watersheds in Uruguay. We anticipated that plantation forestry would result in decreased soil pH and soil base cation concentrations due to base cation uptake by trees. We found that pH and exchangeable base cations were significantly lower in afforested soils compared to grassland soils. These changes were reflected in streamwater chemistry, with pH, base cation concentrations and alkalinities that were significantly lower in streams draining afforested watersheds compared to streams draining grassland watersheds. Our data suggest that repeated cycles of harvesting and replanting will negatively impact the soil store of base cations at these sites and contribute to an impairment of downstream water quality.

  Keywords: water quality, land use change, South America, stream, soil

  
  
• 5:20 PM Author(s):
  Nancy Hoalst Pullen - Kennesaw State University
  Robert F Stallard - USGS
  

  Abstract Title: Correlating tropical soils to soil hydrology: A fine-scale approach.

  
  

  Many tropical soil hydrology studies use augured holes in identifying saturated hydraulic conductivity (Ksat) rates of soils, but few if any studies haveexamined the soils removed from these augured holes, or any potential relationships between the soils and Ksat. In determining the fine-scale patterns and correlations between soil properties and Ksat rates, three permanent Center for Tropical Forest Science (CTFS) Forest Dynamics Plots (FDPs) were used for this study. Within each plot, 20-40 soil samples were collected, with four samples per Ksat augured hole (0-40cm depth, 10cm increments). These soil samples were later analyzed for physical (grain size, color, etc.) and chemical (pH, K, P, etc.) properties. Correlations between soil properties and Ksat varied widely among sampling sites and forest plots. In the Ecuadorian plot, limited vertical movement of water was directly linked to an impermeable clay soil layer at approximately 15cm depth. In the Malaysian plot, soil properties were highly variable and occasionally contradictory when compared to the Ksat measurements. In the Panamanian plot, topographic position influenced both Ksat and soil properties, with steep gradients promoting physical rather than chemical weathering, and flat regions showing increased Ksat rates with depth. As suggested with concurrent studies in Panama and Ecuador, these fine-scale patterns and correlations between soils and soil hydrology are in part the antecedent conditions influencing numerous non-random spatial distributions patterns of tropical plant species.

  Keywords: soil, soil hydrology, tropics. fine-scale