Table 1 .- -Position and treatment of field plots 



Treatment 

 designation 



Pine canopy position ' 

 relative to plot ' 



Seedbed treatment 



Pine -influenced 







Canopy 



Directly overhead 



Litter, duff, and vegetation 







removed to mineral soil 



Litter 



Not directly overhead 



Litter and duff undisturbed. 







vegetation removed 



Stemf low 



Tree in center, small 



Litter, duff, and vegetation 





canopy overhead 



removed to mineral soil 



Near 



Not directly overhead 



Litter, duff, and vegetation 







removed to mineral soil 



Natural 



Directly overhead 



Litter, duff, and vegetation 







undisturbed 



Fire 



Variable 



Litter, duff, and vegetation 







burned 



Opening 







Cleared 



None 



Litter, duff, and vegetation 







removed to mineral soil 



Litter 



None 



Litter, duff, and vegetation 







removed and replaced with 







pine litter and duff 



Natural 



None 



Litter, duff, and vegetation 



undisturbed 



During the last week of October 1974, which was an excellent seed year, the number 

 of naturally occurring ponderosa seeds was counted for each plot by a systematic sample 

 using twelve 8- by 20-inch (20- by 50-cm) quadrats. 



A spherical densiometer was used to determine amount of canopy covering each plot. 



An Eppley pyrheliometer was used to measure solar energy falling on individual 

 treatments. Measurements were made only once, on July 9, 1975, because of infrequent 

 cloudless days and instrument complications. Readings were taken on all plots at approx- 

 imately 10:00 a.m., 12:00 noon, and 3:00 p.m. (MDT) . Total radiant energy from 9:30 a.m. 

 to 3:30 p.m. was calculated by assuming the 10:00 a.m. reading represented energy re- 

 ceived from 9:30 to 11:30, the 12:00 noon reading represented energy received from 

 11:30 to 1:30, and the 3:00 p.m. reading represented that from 1:30 to 3:30. 



Maximum soil surface temperatures were measured with a series of heat-sensitive 

 pellets on each plot in July 1975, the month during which the highest air temperatures 

 were recorded. 



Soils collected for moisture content were also analyzed for nutrient concentrations. 

 At each of the five dates mentioned earier, ammonium and nitrate ion concentrations 

 were determined by specific ion electrode analyses following KCL and water extraction, 

 respectively. A glass electrode measurement of the water extract was used to determine 

 soil pH. Analyses were also made for manganese, potassium, magnesium, phosphates, cal- 

 cium, sodium, iron, copper, and zinc on the June 4, July 21, and September 3 samples. 

 Following ammonium acetate extractions, the cations were measured by atomic absorption. 

 Phosphates were determined colorimetrically . The soil sampling depths varied with 

 sample dates, as before, to better compare nutrient concentrations within the seedling 

 root zone. 



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