Abiotic data are collected at three locations along the transect that are thought to be representative of the abiotic environment of each association. Further, to ensure that the data is representative, an effort is made to keep the data collection activities within a small time frame. For example, we strive to get simultaneous measurements of each variable at the three sites. By necessity however, each groups (A,B,C) data might be collected at a different time of the day or even on a different day.
Temperature of the air, litter and soil is measured both in the sun and shade. Air temperature is taken waist high and soil temperature is measured at a depth of 5 centimeters. A hand held, alcohol type thermometer is used. Measurements taken are recorded in the Abiotic Factor data table.
A sling psychrometer is used to measure the relative humidity of the air at each location. The reading is taken in direct sunlight if possible and then the difference between the wet and dry bulb temperatures is used to estimate the relative humidity from a conversion table. Humidity values obtained are recorded in the data table.
A photometer is used to measure the light intensity at each location. Here, the observer holds the instrument level and takes readings while the sensor opening is pointed in each compass direction (N,E,S,W). The average value of the four readings is recorded.
The association soil moisture value is obtained by weighing a soil sample (approximately 500 grams) collected from an assigned interval of the association. After the moist soil value is obtained and recorded the sample is dried in an oven. The following day the dry weight of the sample is found. The percent soil moisture is found by calculation ((weight difference / moist soil weight) X 100). The soil sample is stored in a plastic bag after collection and before it is weighed in order to prevent drying. Litter is also removed from the ground before the soil sample is taken.
LaMotte (12) test kits are
used to find soil pH, soil nitrogen, soil potassium, soil phosphorus
and soil composition (sand, silt, clay). Typically, the soil samples
are collected in the morning, dried during the afternoon and tested
during an evening laboratory. Students are assigned a specific
test and conduct repeated tests on each sample in order to obtain
consistent results. Again, it is necessary to remove litter from
the ground before the soil sample is taken. Also, all organic
debris (roots, twigs, etc.) is removed from the soil before it