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<br />3.5.1 <br /> <br />Forests <br /> <br />. (a) Conduct a historical study of major insect and <br />disease outbreaks in the Sierra Nevada and summarize the main com- <br />ponents Of the weather for the five years prior to each outbreak. The <br />necessary information should be available from local and regional <br />Forest Service establishments and published weather summaries. <br />(b) Conduct a study to determine the effect of winter precipitation and <br />spring snowpack levels on the water stress profiles of forest tree <br />species during the subsequent growing season. These profiles could <br />be' used as a basis for evaluating stand susceptibility in relation to <br />~ather changes. (c) Develop a correlation between snowfall patterns <br />and the level of physical damage sustained by various tree species as <br />a means of generating estimat es of stand susceptibility to insects and <br />disease. This is important as intermittent damage may serve as <br />beneficial pruning, whereas regular damage may predispose the trees <br />to insects and pathogens. <br /> <br />Scientific studies with respect to this recommendation <br />are to be coordinated by Dr. James Smith of the U. S. Forest Service, <br />Pacific Southwest Forest and Range Experiment. This work will be based <br />in part on Dr. Smith's investigation of the impact of augmentation on <br />snowpack structure. A number of elements of the design study are of <br />hnportance to this work, including specific bas in, rates and accumulation <br />of precipitation expected, and times and targeting of seeding events. <br /> <br />3.5.2 <br /> <br />Seeding Mate rials <br /> <br />. The several agencies supporting research in weather <br />modification should jointly establish a working group, comprised of <br />both governmental and non-governmental scientists, to assess the <br />pre sent state of knowledge about ecological aspects of seeding agents, <br />identify potential problem areas, and recommend specific research <br />topics. The ultimate goal of this working group should be to prepare <br />a. comprehensive analys is of the environmental impact of seed ing agents, <br />an analys is which can be applied directly to any weather modification <br />project anywhere. This study could perhaps be undertaken by the <br />National Academy of Sciences -National Re search Council. <br /> <br />14 <br />