Spatio‐temporal structure of multi‐storied, multi‐aged interior Douglas fir (Pseudotsuga menziesii var. glauca) stands

Abstract

Summary1. We used replicated, repeated-measures data to examine the spatio-temporal structure of multistoried, multi-aged interior Douglas fir (Pseudotsuga menziesii var glauca (Mirb.) Franco) stands growing on dry sites under more than 50 years of fire protection. Along with the univariate and bivariate Ripley's K and related functions, we used a random coefficients mixed model to investigate the variation in these functions over replicates and time. 2. The spatio-temporal analyses revealed that trees greater than 1.3 m in height were clustered over space, and clustering was more evident for small trees (i.e. diameter at breast height (d.b.h.) £ 7.0 cm). 3. Bivariate functions indicated that small trees were spatially aggregated with large trees, indicating higher germination success and early survival near large trees. For these dry sites, moisture is more limiting than light and large trees provide moister microsites. 4. Dead trees were clustered, more commonly smaller in size and aggregated near large trees, indicating competition for moisture. 5. For the 16-year period of the study, there was very little evidence that the spatio-temporal patterns changed from a clustered to a more regular arrangement over time, unlike evidence from studies in other forest types. 6. Using the random coefficients mixed model approach, the majority of spatio-temporal variation was due to differences among replicates, with little variation over time. 7. Under fire protection, interior Douglas fir stands on dry sites might be expected to have lower mortality but any increase in density will be limited by moisture availability. Since interior Douglas fir is moderately shade-tolerant, this may result in an approach to a steady state of regeneration and death over the long term. 8. Synthesis. Spatio-temporal analysis using replicated, repeated-measures data, including a random coeffcieints mixed model approach, gave useful insights into mortality and recruitment in multi-storied and multi-aged stands. Similar patterns might be expected in other naturally occurring multi-storied and multi-aged stands. The use of replicated, repeated-measures data rather than chronosequence data allows for the examination of true changes in spatial patterns over time.

A spatio-temporal dataset of forest mensuration for the analysis of tree species structure and diversity in semi-natural mixed floodplain forests

“…In addition, sampling design allows integration of this dataset with other ones available from previous studies (e.g. Aguirre et al 2003;Hui and Pommerening 2014;LeMay et al 2009), useful for comparative, large-scale studies. The data allowed a traditional set of forest parameters to be extracted like stand variables (stocking rate, basal area, species composition, dominant height, mean diameter).…”

“…Extension of spatial analyses to include changes in time allows the examination of changes in stand structure due to mortality, growth, regeneration and competition (LeMay et al 2009). In this line, the relevant strength of the dataset is that it allows performing an integrated set of tree structure and diversity analyses at both spatial and temporal scales.…”

“…However, because of cost and time constraints, very few studies have performed spatial-temporal analysis of forest stands dynamics (e.g. LeMay et al 2009). In addition, most studies employed chronosequences rather than true time series (repeated measures on permanent plots), which may introduce some uncertainties in interpreting trends over time.…”

Spatial statistics in ecological analysis: from indices to functions

“…If objects within the spatial window are clumped, then the K-function receives higher values (K(r) > πr 2 or L(r) > 0), and if they are regularly (evenly) spaced -the K-function shows low values (K(r) < πr 2 or L(r) < 0) (Illian et al 2008;LeMay et al 2009). In the first case the typical point is a part of the cluster and has few nearest neighbors and the local density is larger than λ.…”

Spatial diversity of planted and untended silver birch (Betula pendula L.) stands

“…Of particular importance are changes in stand structure occurring during its various stages of development. The long life of trees, however, means that studying forest dynamics requires long-term work and analyses, repeated every several or several dozen years (Szymański 1964;Ward et al 1996;Kenkel et al 1997;Hessburg et al 2000;Woods 2000;Szmyt 2004;Wolf 2005;Saunders, Wagner 2008;LeMay et al 2009). Most research on forest dynamics has been conducted on natural forests; much less so on artificially established forests.…”