Biomass, nutrient distribution and litterfall in Populus, Pinus and Picea stands on two different soils in Minnesota

Pole sized stands ofPopulus tremuloides Michx.,Picea glauca (Moench.) Voss,Pinus resinosa Ait., andPinus banksiana Lamb., were sampled on both a very fine sandy loam and a loamy sand. Relative species ranking in above-ground tree biomass (Pinus resinosa\u3ePopulus\u3ePicea\u3ePinus banksiana) and above-ground tree nutrient (N, P, K, Ca, Mg) weights (Populus\u3ePicea\u3ePinus resinosa\u3ePinus banksiana) were similar on both soils. Particularly large proportions of biomass and nutrients were found in aspen bark and spruce foliage and branches on both soils. Harvesting entire above-ground trees would remove up to three times more nutrients than would harvesting only the bole. Herbs and shrubs had less than 3% of the total vegetation organic matter but contributed as much as one-half of the total annual litterfall nutrients. Litterfall weights and nutrient concentrations, and especially forest floor nutrients, were all less on the loamy sand. Nutrients in the rooting zone of the loamy sand were 12 to 29% less than in the very fine sandy loam except for P which averaged 24% higher. On both soils, exchangeable Ca in the surface soil was much lower under Populus and Picea than under the pines, owing to species differences in uptake and apparently slow release of Ca by weathering. Ca in the above-ground Populus amounted to 18% (very fine sandy loam) to 25% (loamy sand) of the exchangeable Ca in the total complex. Intensive utilization of this species in particular could stress the Ca economy of these sites