What is it about?
Mark variograms are widely adopted in forest ecosystem studies for analyzing spatial interaction among trees. Inference on mark variograms can be performed under a model-dependent perspective (ergodic variograms) or under a deterministic perspective (non-ergodic variograms).
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Why is it important?
A simple and workable definition of non-ergodic mark variogram is introduced based on distances between pairs of trees distinguished by distance classes. Design-based estimators of mark variogram values are proposed as the ratio of two Horvitz–Thompson estimators using replicated plots randomly located on the study area and using the inclusion probabilities of the pairs of trees. A jackknife estimator of the variance of such an estimator has been proven to give conservative estimates of precision.
Perspectives
The use of sample plots in forest surveys is a well-investigated and well-experienced technique. Guidelines for the effective implementation of plot sampling in real forests are available in many textbooks on environmental and forest sampling. In accordance with these considerations, the paper provides a design-based, straightforward estimation criterion of mark variograms based on a sampling scheme of practical importance, being one of the most widely adopted in forest investigations.
Piermaria Corona
CREA Research Centre for Forestry and Wood
Read the Original
This page is a summary of: Design-based estimation of mark variograms in forest ecosystem surveys, Spatial Statistics, April 2019, Elsevier,
DOI: 10.1016/j.spasta.2019.02.002.
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