Seasonal Changes in Standing Crop and Primary Production in a Sedge Wetland and an Adjacent Dry Old‐Field in Central Minnesota

Seasonal changes in above— and below—ground standing crop and primary production in a Carex rostrata wetland and an adjacent dry Poa pratensis old field were determined. Above ground, the Carex rostrata standing crop of green material varied from a minimum of 114 g/m 2 frozen in the winter ice to a high of 852 g/m 2 in late August. Maximum daily production averaged about 11 g/m 2 ° day from mid—June to mid—July. Below—ground standing crop was highest in winter at 328 g/m 2 in late July. Below—ground standing crop then increased at a rate averaging about 1 g/m 2 #?day. Poa pratensis growth was rapid in early spring, the green above—ground standing crop peaked at 114 g/m 2 in late May—early June. A definite midsummer cessation of growth then occurred, the average summer standing crop averaging jut 87 g/m 2 during July and August. A second greater peak of production then occurred with a maximum standing crop of 149 g/m 2 reached in late September. The daily production rate at this maximum was 3.3 g/m 2 °day. Below ground the standing crop in the 0—20 cm level was at the season's high of 1667 g/m 2 in winter and then declined to an average summer low of 1194 g/m 2 after which it rose to 1458g/m 2 in late October.