A set of theoretical question in biogeography that remains unresolved regarding some forests relates to historical natural disturbances. Were these disturbances infrequent, large, and of high severity, suggesting landscapes that were in disequilibrium, having a shifting, patchy spatial structure? Were the disturbances frequent and of low severity, maintaining an enduring, spatially uniform old-growth forest? Or were these disturbances variable in severity with a mixture of patterns across landscapes? The answers have broad implications, as laws, policy, industries, and public uses are affected. The questions remain unanswered for some major forest types, such as ponderosa pine forests in the western United States, because data are limited about forest structure and disturbance before widespread EuroAmerican land uses. The General Land Office (GLO) survey, which was conducted when lands were initially surveyed for EuroAmerican settlement, has systematic data across the U.S. The surveys, largely done in the late-1800s in the West, recorded data on "witness trees" at surveyed corners, including tree species, diameter, bearing, and distance from the corner. The GLO survey also recorded high-severity disturbances, such as crown fires and blowdowns. This research project will use calibrated and refined methods for analyzing the GLO data to address four general questions about ponderosa pine landscapes: (1) How spatially uniform or variable was forest structure (e.g., tree density, tree diameter distributions) across large landscapes? (2) What were the key agents (e.g., fire) of high-severity disturbance, and the rates and patterns of these across landscapes? (3) Did the spatial structure and the role of high-severity disturbance vary among regions? (4) Were forest structure and high-severity disturbance linked, and, if so, what was the pattern of linkage? The investigators will use the GLO data to reconstruct forest structure and disturbances across three large ponderosa pine landscapes in the western U.S. and analyze the reconstructions to address the four general questions and nine specific hypotheses related to them.
The pattern and scale of variation in some major western forests, such as ponderosa pine forests, are poorly known before alteration by widespread land uses. Only a few small, scattered reconstructions, historical anecdotes, and early photographs are available for these important western forests. This project will expand understanding of these forests by using early survey records to reconstruct the attributes of late-1800s ponderosa pine forests across three large, representative land areas. The project will provide data about fires and other disturbances and maps of reconstructed forest variation. These data should aid policy formulation by agencies and interest groups and be useful in management and restoration. The maps and information will also be valuable in management and restoration, as specific data will be provided on tree densities, sizes, and other forest characteristics.
