DOI: 10.5061/dryad.z34tmpg8s
title: Data from: Retention forestry influences understory diversity and functional identity

description: In recent decades, a paradigm shift in forest management and associated
 policies has led to greater emphasis on harvest practices that retain
 mature, overstory trees in forest stands that would otherwise be clearcut.
 While it is often assumed that the maintenance of compositional and
 structural complexity, such as that achieved through retention forestry
 approaches, will also mitigate negative impacts to functional diversity,
 empirical evidence of this relationship is sparse. We examined the effects
 of an aggregated retention system on taxonomic and functional diversity in
 a regenerating aspen-dominated forest. Sampling was conducted along
 transects arranged to capture the transition from harvested (regenerating)
 forest to mature, unharvested forest (both intact forest stands and 0.1 ha
 retention aggregates). We then assessed the magnitude and distance of edge
 effects on multiple indices of taxonomic and functional diversity as well
 as functional identity.  Twelve years after harvest, the distance
 and magnitude of edge effects on functional and taxonomic diversity did
 not differ between the two unharvested patch sizes (intact vs. aggregate);
 however, intact forest exhibited greater resistance to edge effects and
 greater depth of edge influence into harvested areas for some traits
 compared to aggregates. Analyses relying on functional traits
 were generally applicable across sites within a highly variable forest
 type, and our results demonstrate the promise of using functional traits
 to assess management impacts on plant diversity across a landscape.
 Aggregates maintained some functional attributes associated with interior
 forest and influenced adjacent regeneration. However, trends in some
 traits (i.e. shade tolerance and seed mass), particularly in the seedling
 layer, suggest aggregates of this size provide primarily edge habitat.
description: We characterized the understory woody community by sampling two
 strata: 1) seedlings and small shrubs (“seedling layer”) and 2) saplings
 and large shrubs (“sapling layer”). Cover for the seedling layer (all
 woody stems &lt;1 m in height) was estimated to the nearest 1% (or
 nearest 0.1% if cover &lt; 1%) in paired, 1 m<sup>2</sup>
 subplots located 2 m perpendicular to and on either side of transects at
 each 10-m distance and nested within the plot used for quantifying larger
 vegetation (Figure 1c). Species abundance in the sapling layer was
 measured using a combination of two plot sizes (Figure 1c). Species and
 DBH (1.37 m) were recorded for larger stems (2.54 cm ≥ DBH ≤ 10 cm) in
 circular 5 m radius plots (78.5 m<sup>2</sup>) centered on
 each 10-m distance mark along transects. Smaller stems with height ≥ 1 m
 and DBH &lt; 2.54 cm were measured 15 cm above the root collar in
 circular, 1.26 m radius (5 m<sup>2</sup>) plots nested within
 the larger plots. Here, we have provided cover for
 seedling and small shrub species in the "seedling layer" at each
 10-m sampling point (an average of observations from the paired, 1
 m<sup>2</sup> plots located at each distance).  We have also
 provided biomass for woody species observed in the "sapling
 layer" estimated with allometric equations (Perala and Alban 1993)
 using the diameter measurements described above.
description: Excel spreadsheet contains two tabs: 1)
 Sapling layer biomass: Data are biomass (Mg/ha) estimated for the sapling
 layer at each transect distance. 2) Seedling layer
 cover: Data are the average of the percent cover estimated at two, paired
 1 m<sup>2</sup> plots located at each transect
 distance.