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Sharing land via keystone structure: retaining naturally regenerated trees can efficiently benefit birds in plantations

Citation

Yamaura, Yuichi; Unno, Akira; Royle, J. (2022), Sharing land via keystone structure: retaining naturally regenerated trees can efficiently benefit birds in plantations, Dryad, Dataset, https://doi.org/10.5061/dryad.xpnvx0kj0

Abstract

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 sharing and sparing. Although most empirical studies the efficacy comparing land sparing/sharing supported land sparing, land sparing may be more efficient if habitat structures providing crucial resources for various species––keystone structures–– are clearly involved and its performance is tested by rigorous experimental design. 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 with treatments) 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. 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 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 between clear-cutting and low amounts of 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 broad-leaved trees per ha may be sufficient to maintain forest bird abundance higher than clear-cutting over the rotation cycle. Retention approaches can be incorporated into management systems using certification schemes and best management practices. We should develop an awareness of the roles and values of naturally regenerated trees to diversify plantations.

Methods

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.

Usage Notes

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

Funding

Mitsui and Company, Award: R12-G2-225, R15-0025

Japan Society for the Promotion of Science, Award: JP25252030, JP18H04154