Biogeochemical calcium cycling of Andropogon scoparius Michx. in two contrasting soil types

Abstract

Techniques of dry ashing plant material and column extracting soil material were developed to convert ⁴⁵Ca to a chloride salt. Calcium-45 recovery efficiency was approximately 90% for plant material and 95% for soil. Movement and distribution within Andropogon scoparius Michx. tillers, clones, and associated ecosystems were investigated in greenhouse and field studies using ⁴⁵Ca as a tracer. Two contrasting soil types, Heiden-Hunt clay and Tabor fine sandy loam, were utilized. Calcium-45 introduction was achieved by both foliar and soil application techniques. Initial movement of foliar applied ⁴⁵Ca was rapid in greenhouse-grown tillers. Movement from point of introduction was basipetal and acropetal with activity observed in every tiller compartment and the soil within 1 hour following isotope introduction. Temporary redistribution was observed between leaf and sheath (major compartments of accumulation) during 100.5 hr following isotope introduction. Over time ⁴⁵Ca was immobilized and accumulated in the leaf, sheath, and senescent material. Calcium in the sheath was remobilized and transported to developing seed culms. Field studies indicated ⁴⁵Ca distribution within clonal tillers was similar to that observed in greenhouse-grown tillers. Over 56% of foliar applied ⁴⁵Ca had been transferred from clay-grown clones to the soil compartment while 11% was in the associated vegetation compartment after 4 mo. The sand soil compartment contained over 63% of the total applied activity with 8% in the associated vegetation compartment. At the end of the second growing season, the soil compartment contained about 85% of the applied ⁴⁵Ca, regardless of soil type. An active calcium cycle on the clay ecosystem was not identified, while a rapid cycle was documented on the sand ecosystem.