The implications of possible increases in carbon dioxide and other greenhouse gases on water resources have attracted increasing attention. Well-established techniques have been used to relate air temperature scenarios produced by GISS, GFDL and OSU global climate models to surface water temperatures and, subsequently, to water quality through a waste load allocation model for streams across the southern United States. There is a consensus among the 3 GCM scenarios studied that surface water temperature increases of up to 7 ' C can be expected. Results of the application of a Streeter-Phelps waste load allocation model indicate that even though existing advanced treatment technology would be sufficient to maintain desirable levels of instream dissolved oxygen under elevated water temperature conditions, the use of such technology would be necessary on a much wider scale than at present. The use of extensive riparian vegetative shading was considered as a supplement to advanced water treatment technology. Results show that under 2 of the 3 climate change scenarios and projected patterns of forest migration, shading could appreciably offset the greenhouse-induced water temperature increases east of longitude 97 "W. If present maximum levels of natural riparian assemblages were maintained but no species migration were to take place, water temperatures could still rise in some areas as much as 7 "C. If other environmental or anthropogenic stresses were to result in a major decrease in vegetative cover, such water temperature increases could easily be exceeded.
We used the process model BIOMASS version 13.0 to simulate contemporary net pnmary production (NPP) and NPP response to climate prolections for a doubhng of atmospheric CO2 concentration from 2 general circulation models (GCMs) that vary in their CO2 sensitivity: the less sensitive GFDL and the more sensitive UKMO. Increased GCM sensitivity to CO2 is reflected in increased predictions in the magnitude, vanation, and range of the clunate variables. Smulations used a 40 yr historical climate record, and 2 stand and site conditions to standardize the total NPP response estimates for eighteen 1x1" grid cells across the southern U n~t e d States. Contemporary NPP and NPP response estimates from the 18 cells were smoothed using a cell search algonthm to obtain a n NPP response index matrix for the entlre loblolly pine (Pinus taeda) forest-type We conducted a sensitivity analysis of the environmental variables projected to change in a 2xC0, environment to help interpret simulation output. Contemporary NPP varied from 2.5 to 8.5 Mg C ha-' yr-' over the range of loblolly pine High leaf area index (LA1) sirnulations had 1.5 to 2 times the productlvity of low LA1 simulations, but the regional patterns were similar, NPP was correlated with regional ddferences in precipitation and temperature. The NPP response to future climate and atmospheric changes depended on the GCM used, and on the stand and site condition assumed. Inter-annual estimates for the 18 cell simulations resulted in a +22 to + 8 4 % NPP response for the GFDL climate projections and a -30 to +94% NPP response for the UKMO clunate prolections. The 40-year average NPP response for the smoothed data ranged from + 4 3 to + 6 5 % and 1 to + 9 4 % for the GFDL and the UKMO climate prolections, respectively. Consequently, the magnitude and range of the 40-year average NPP response to the climate prolections was directly correlated with the GCM CO2 sensitivity. Although ~ncreased CO2 sensitivity resulted in broader extremes in the predicted temperature response, precipitation response for the 2 models was similar. The NPP response was also correlated with the patterns in predicted climate change, w~t h regional differences coupled to local climatic conditions. Climate projections from both models produced similar NPP responses when predicted temperatures and precipitation regvnes were similar. Elevated ambient CO2 had a greater effect on NPP response than temperature or precipitation in the sensitivity comparisons. Simulations indicate that a CO2 fertilizer effect, assuming no CO2 acclimation, more than compensates for decllnes in productlvity over most of the loblolly pine forest-type associated with projected decreased precipitation and/or projected low to moderate increases in temperature and, therefore, increased maintenance respiration costs.
The role of c l~m a t e research as i t applies to the emerging area of monitonng and assessment of ecolog~cal status health and trends IS discussed Such applicat~ons requlre techniques that synthesize mult~ple, often interacting sources of climate-denved ecological stress These stresses operate across multiple plant and animal species and span a range of temporal and spatial hierarchical scales A working hypothesis of forest ecosystem/climate interactions 1s proposed The basis of the hypothesis is the definition of climatological persistence and disturbance characterist~cs of a region A climate database was assembled for the northeastern Unlted States Summaries that synthesize the spatial distribution, frequency, area and magnitude of climatological disturbance events are presented These summanes are specifically d e s~g n e d to facilitate the testing of the interaction hypothesis proposed in the present study Conclusions concerning climate stress 111 the area, as suggested by a 1961 to 1970 disturbance summary, are compared to results of recent research concerning declines In high elevation red spruce The present research IS the f~rst step in the developinent of regional scale c l~m a t e disturbance/forest ecosystem relat~onships Future research will seek to l~n k operational observat~ons of forest status and behavior with these mult~var~ate, climatolog~cal summanes O Inter-Research 1992
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