Nitrogen Content and Other Soil Properties Related to Age of Red Alder Stands
1981
Bormann, B. T. | DeBell, D. S.
The magnitude and pattern of nitrogen (N) accretion and other changes in soil properties were assessed for red alder stands (Alnus rubra Bong.) 5 to 41 years old growing on the same soil type in the same general area. Regression of soil nitrogen (N) content over stand age revealed that N has accumulated at a nearly constant rate of about 35 kg ha⁻¹ year⁻¹ in the mineral soil (0- to 20-cm depth) beneath alder stands. After an apparently rapid build-up in the first decade, forest floor N increased linearly from 10 to 40 years at a rate of 15 kg ha⁻¹ year⁻¹. Other mineral soil characteristics beneath alder stands differed markedly from those beneath adjacent Douglas-fir stands [Pseudotsuga menziesii (Mirb.) Franco]; organic matter content was 20% higher, and pH and bulk density were much lower. The rate of N accretion and improvement of other soil characteristics suggest opportunities for increasing yields of Douglas-fir grown in mixed or rotational culture with red alder.
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