Ecological relationships of wild rice, Zizania aquatica. 7. Sediment nutrient depletion following introduction of wild rice to a shallow boreal lake

Abstract

A marked decline in wild rice production was observed 5 years after a northwestern Ontario lake was seeded. A paired-comparison t-test detrmined that sediment manganese, zinc, copper, magnesium, and potassium had all declined in concentration, but nitrogen showed the greatest decrease. Discriminant analysis indicated that sediment nitrogen contributed most to a function distinguishing between years. A controlled experiment using several fertilizer formulations also found that addition of nitrogen to sediment from the lake promoted the greatest increase in wild rice growth. Changes in distribution of wild rice and in values of water depth, organic matter, dry weight of other macrophytes, and wild rice density and dry weight indicated that the decrease in sediment nitrogen was probably associated with movement of wild rice straw within the lake.