Model-based ideas in finite-population sampling have received renewed discussion in recent years.Their relationship to the classical ideas in sampling theorydo not appear to be universally well understood by samplers in applied disciplines such as forestry, and ecology more broadly.The two inferential paradigms are constrasted, andexplanations are supplemented with examples of discrete aswell as continuously distributed populations. The treatment of spatial structureis examined, also.

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Almost any type of sample has some utility when estimating population quantities. The focus in this paper is to indicate what type or combination of types of sampling can be used in various situations ranging from a sample designed to establish cause-effect or legal challenge to one involving a simple subjective judgment. Several of these methods have little or no utility in the scientific area but even in the best of circumstances, particularly complex ones, both probabilistic and non-probabilistic procedures have to be used because of lack of knowledge and cost. We illustrate this with a marbled murrelet example.

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Traditionally, forest crown position is classified into one of four categories: dominant, codominant, intermediate, and suppressed. The crown definitions have two primary components: a tree's stature relative to the stand's canopy level and the amount and type of light received by its crown. While this classification is meant primarily for even-aged, single level canopy stands, it is applied widely to uneven-aged stands and to those with multilevel canopies. The objective of this study was to examine the repeatability of estimating crown position in a variety of stands in the southern Appalachian spruce–fir forest. We found that crown position was difficult to similarly reclassify on the second visit in uneven-aged stands. Distinguishing a dominant from a codominant crown resulted in the lowest remeasurement proportion of agreement. We propose that the canopy position definitions be clarified and suggest an alternate system of crown classification.