Lightning, precipitation and vegetation at landscape scale

We investigated the question "Is there a relationship between seasonality i n precipitation and vegetative cover in Pole Canyon, NM?" GIS and statistic al methods were used to determine the degree of association between either summer or winter precipitation and percent canopy cover for trees, graminoi ds and total vegetation. Monsoon (summer) precipitation was predicted for t he years 1986-1994 from lightning strike and relative humidity data by mult iple regression. Winter precipitation, the percent of annual precipitation that occurs during winter, and vegetative cover were derived from the Fores t Service Terrestrial Ecosystem Survey. Vegetation and precipitation data w ere ranked and classified (e.g., high, medium, low) and cross-tabulations w ere generated to compare the spatial distribution of vegetation classes wit hin each precipitation class. Results indicate that seasonality in precipitation affects the distribution and spatial pattern of vegetation at landscape scales. Winter precipitatio n is a key factor that influences the distribution and spatial pattern of t ree cover. Monsoon precipitation may affect the spatial pattern of graminoi d cover where Bouteloua gracilis dominates. Winter precipitation may affect the distribution and spatial pattern of graminoid cover where Festuca ariz onica dominates. Some of the unexplained relationships may be due to compet ition between trees and graminoids for moisture and other limiting factors. The importance of temperature was implicit in the division between summer (monsoon) and winter seasons. Annual precipitation, elevation, topography a nd edaphic factors probably contributed to the observed relationships.