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Fire severity, frequency, and extent are expected to change dramatically in coming decades in response to changing climatic conditions, superimposed on the adverse cumulative effects of various human-related disturbances on ecosystems during the past 100 years or more. To better gauge these expected changes, knowledge of climatic and human influences on past fire regimes is essential. We characterized the temporal and spatial properties of fire regimes in ponderosa pine forests of the southern San Juan Mountains of southwestern Colorado by collecting 175 fire-scarred tree samples from nine sites across a wide range of topographic settings. All tree rings and fire scars were dated using standard dendrochronological...
The Colorado River Basin, poor in water and rich in energy resources, is examined to see if water quality can be sustained for U.S. and Mexican users. Activities to mine, process, transport, and convert resources to energy and to reclaim the land all require water, although development is expected to continue in spite of uncertainties. Projections of water requirements for different energy sources are summarized for the 1990-2000 time period. Restrictions on water supply derive from both quantity limitations and such institutional barriers as water rights and contracts. Projections of the sources and occurrences of salinity levels and pollutants are detailed for each section of the Basin. Salinity is concluded to...