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Full-Text Articles in Physical Sciences and Mathematics
Autoregressive Moving Average Models Of Conifer Crown Profiles, Samantha J. Gill, Gregory S. Biging
Autoregressive Moving Average Models Of Conifer Crown Profiles, Samantha J. Gill, Gregory S. Biging
Natural Resources Management and Environmental Sciences
A time-series autoregressive moving average (ARMA) approach was used to develop stochastic models of tree crown profiles for five conifer species of the Sierran mixed conifer habitat type. Models consisted of three components: (1) a polynomial trend; (2) an ARMA model; and (3) random error. A Bayesian information criterion was used to evaluate alternative models. It was found that 70% of the crown profiles could be modeled using first-order ARMA [AR(1) or MA(1)] models, and that an additional 25% could be modeled using a white noise model [(AR(0)]. When the coefficients of the ARMA models were statistically significant, the models …
An Ecological Basis For Managing Giant Sequoia Ecosystems, Douglas D. Piirto, Robert R. Rogers
An Ecological Basis For Managing Giant Sequoia Ecosystems, Douglas D. Piirto, Robert R. Rogers
Natural Resources Management and Environmental Sciences
A strategy for management of giant sequoia groves is formulated using a conceptual framework for ecosystem management recently developed by Region Five of the USDA Forest Service. The framework includes physical, biological, and social dimensions. Environmental indicators and reference variability for key ecosystem elements are discussed in this paper. The selected ecosystem elements include: 1) attitudes, beliefs, and values; 2) economics and subsistence; 3) stream channel morphology; 4) sediment; 5) water; 6) fire; 7) organic debris; and 8) vegetation mosaic. Recommendations are made for the attributes of environmental indicators that characterize these elements. These elements and associated indicators will define …
Autoregressive Moving Average Models Of Crown Profiles For Two California Hardwood Species, Samantha J. Gill, Gregory S. Biging
Autoregressive Moving Average Models Of Crown Profiles For Two California Hardwood Species, Samantha J. Gill, Gregory S. Biging
Natural Resources Management and Environmental Sciences
Time-series Autoregressive Moving Average (ARMA) models were employed to model tree crown profiles for two California hardwood species (blue oak and interior live oak). There are three major components of these models: a polynomial trend, an ARMA model, and unaccounted for variation. The polynomial trend was used to achieve a stationary series. For these crown profiles, the use of a quadratic trend resulted in a stationary series for 60% of the profiles. A cubic trend was used for another 23%, and a quartic for 7%. It was found that 80% of the tree crown profiles could be modeled using a …