DOI: 10.5061/dryad.xpnvx0kj0
title: Sharing land via keystone structure: retaining naturally regenerated trees may efficiently benefit birds in plantations

description: Meeting food/wood demands with increasing human population and per-capita
 consumption is a pressing conservation issue, and is often framed as a
 choice between land sparing and land sharing. Although most empirical
 studies comparing the efficacy of land sparing and sharing supported land
 sparing, land sharing may be more efficient if its performance is tested
 by rigorous experimental design and habitat structures providing crucial
 resources for various species––keystone structures––are clearly involved.
 We launched a manipulative experiment to retain naturally regenerated
 broad-leaved trees when harvesting conifer plantations in central
 Hokkaido, northern Japan. We surveyed birds in harvested treatments,
 unharvested plantation controls and natural forest references one-year
 before the harvest and for three consecutive post-harvest years. We
 developed a hierarchical community model separating abundance and
 space-use (territorial proportion overlapping treatment plots) subject to
 imperfect detection to assess population consequences of retention
 harvesting. Application of the model to our data showed that retaining
 some broad-leaved trees increased total abundance of forest birds over the
 harvest rotation cycle. Specifically, pre-harvest survey showed that the
 amount of broad-leaved trees increased forest bird abundance in a concave
 manner (i.e., in a form of diminishing-return). After harvesting, a small
 amount of retained broad-leaved trees mitigated negative harvesting
 impacts on abundance though retention harvesting reduced the space-use.
 Nevertheless, positive retention effects on the post-harvest bird density
 as the product of abundance and space-use exhibited a concave form. Thus,
 small profit reductions were shown to yield large increases in forest bird
 abundance. The difference in bird abundance between clear-cutting and low
 amounts of broad-leaved tree retention increased slightly from the first
 to second post-harvesting years. We conclude that retaining a small amount
 of broad-leaved trees may be a cost-effective on-site conservation
 approach for the management of conifer plantations. Retention of 20-30
 broad-leaved trees per ha may be sufficient to maintain higher forest bird
 abundance than clear-cutting over the rotation cycle. Retention approaches
 can be incorporated into management systems using certification schemes
 and best management practices. Developing an awareness of the roles and
 values of naturally regenerated trees is needed to diversify plantations.
description: We conducted
 a bird survey to examine the efficacy of retention forestry in conifer
 plantations. We surveyed birds in harvested treatments, unharvested
 plantation controls and natural forest references before and after the
 treatment (harvesting).  Here we
 upload the source data, R statistical code used to get the results shown
 in the main text, and parameter estimates obtained.
description: We upload the following four
 items: before_after_harvest-excl-edge-incl-large.R: R
 statistical code bird_before_after_harvest.csv: bird census data
 we collected in the field site_v2.csv: IDs of 23 surveyed
 stands site_v3.csv: properties of 23 stands used in the
 analysis parameter estimates - excl_edge_incl_large.xlsx:
 parameter estimates from the analysis by excluding edge records while
 including large-sized species<br>