Analysis of an Alpine Environment

Abstract

If plant physiological approaches are to be applied to the solution of ecological problems, it is essential that the field environment and the response of plants to it be described and understood, even to the level of the microenvironment surrounding the responding constituents of the cell. We have studied the environment of the alpine zone on the northern border of Rocky Mountain National Park since 1960, and results of these studies are summarized here. The approach attempts to emphasize the time factor, considering the periods and amplitudes of cyclical changes in environmental parameters at four levels of cycle lengths: short cycles (seconds to hours), diurnal cycles, secular cycles (several days), and annual cycles. In addition to this analysis of change, the usual averages must also be considered in any environmental description. Light intensity, measured continuously with a pyrheliograph, was analyzed primarily from the standpoint of total daily incoming radiation and number of fluctuations (due to clouds) per day, but the temperature records, obtained with a hygrothermograph in a special dome-shaped weather shelter near the ground, were analyzed more intensively. Total daily temperature fluctuations and number of cycles were measured, and these values were considered as a function of location, time during the season, and year. Diurnal cycles were also described, and changes in these constituted secular weather cycles having periods of about 10-22 days. A temperature index was derived from the daily short-cycle variations, the diurnal temperature amplitude, and the daily average temperature. This index proved valuable in detection of secular cycles, differences between various locations, etc. For the summer of 1965, a comparison was made between the station in Rocky Mountain National Park and a new station placed on Independence Pass in central Colorado. Other factors of the environment were also studied, including wind velocity, precipitation, atmospheric humidity, and various soil factors. These parameters were not emphasized in the present study, but they should be an important part of any future attempt to understand the physiological ecology of the alpine tundra. Implications of these environmental studies in the field for future (and current) laboratory studies using controlled environments are briefly considered.