The Effect of Nitrogen Fertilization, Rock Type, and Habitat Type on Individual Tree Mortality
Abstract:An individual tree mortality model for nitrogen fertilized Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) stands was developed using data from permanent research plots located throughout the inland Northwest. The proposed linear logistic model included the following independent variables: a dummy variable for the two habitat types, a set of dummy variables for the five rock types, a set of dummy variables for the three N fertilizer treatments, diameter at breast height, crown ratio, and crown competition factor. The results show that N fertilization, rock type, and habitat type significantly affect individual tree mortality. The probabilities of tree mortality on fertilized plots were greater than those on control plots and increased with increasing N fertilizer application rates. Trees growing on granitic and metasedimentary rocks had lower foliar potassium concentration and exhibited greater probabilities of mortality than did those growing on other rocks. The probabilities of mortality for trees growing on sedimentary rocks were very low. Moist sites had lower soil fertility and produced higher mortality rates than dry sites. Furthermore, the N fertilization response ratio, defined as the annual mortality probability of a fertilized tree over the annual mortality probability of a unfertilized tree with identical tree and stand characteristics, was estimated based on the mortality model. The response ratios were nearly constant (about 1.4) across a range of tree diameters for all rock types with the 224 kg N treatment. The response ratios were also nearly constant (about 2.1) across a range of tree diameters for all rock types with the 448 kg N treatment. Finally, the mortality prediction model passed a validation test on independent data not used in model development. For. Sci. 47(2):203–213.
Keywords: Pseudotsuga menziesii var. glauca; environmental management; foliar potassium; forest; forest management; forest resources; forestry; forestry research; forestry science; logistic function; mortality prediction; natural resource management; natural resources; soil fertility
Document Type: Miscellaneous
Affiliations: 1: Graduate Research Assistant Department of Forest Resources, University of Idaho, Moscow, ID, 83844-1133, Phone: (208) 885-3703 firstname.lastname@example.org 2: Professor Department of Forest Resources, University of Idaho, Moscow, ID, 83844-1133, Phone: (208) 885-7421 email@example.com 3: Dean College of Natural Resources, University of Idaho, Moscow, ID, 83844-1138, Phone: (208) 885-6442; Fax: (208) 885-5534 firstname.lastname@example.org
Publication date: May 1, 2001
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