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The capacity of forests to resist structural change and retain material legacies–the biotic and abiotic resources that persist through disturbance–is crucial to sustaining ecosystem function after disturbance. However, the role of forest structure as both a material legacy and feature supporting carbon (C) cycling stability following disturbance has not been widely investigated. We used a large-scale disturbance manipulation to ask whether legacies of lidar-derived canopy structures drive 3-year primary production responses to disturbance. As part of the Forest Resilience Threshold Experiment (FoRTE) in northern Michigan, USA we simulated phloem-disrupting disturbances producing a range of severities and affecting canopy trees of different sizes. We quantified the legacies of forest structure using two approaches: one measuring the change in structure and primary production from pre-to post-disturbance and the second estimating resistance as log transformed ratios of control and treatment values. We found that total aboveground wood net primary production (ANPP w ) was similar across disturbance severities as legacy trees rapidly increased rates of primary production. Experiment-wide, the disturbance had limited effects on change in mean structural complexity values; however, high variance underscored large differences in the magnitude and direction of complexity's response at the plot-scale. Plot-scale structural complexity, but not vegetationmore »area index (VAI), resistance strongly predicted ANPP w resistance while temporal VAI and structural complexity changes did not. We conclude that the presence of material legacies in the form of forest structure may affect primary production stability following disturbance and that how legacies are quantified may affect the interpretation of disturbance response.« less

Carbon (C) cycling processes are particularly dynamic following disturbance, with initial responses often indicative of longer-term change. In northern Michigan, USA, we initiated the Forest Resilience Threshold Experiment (FoRTE) to identify the processes that sustain or lead to the decline of C cycling rates across multiple levels (0, 45, 65 and 85% targeted gross leaf area index loss) of disturbance severity and, in response, to separate disturbance types preferentially targeting large or small diameter trees. Simulating the effects of boring insects, we stem girdled > 3600 trees below diameter at breast height (DBH), immediately and permanently disrupting the phloem. Weekly DBH measurements of girdled and otherwise healthy trees (n > 700) revealed small but significant increases in daily aboveground wood net primary production (ANPPw) in the 65 and 85% disturbance severity treatments that emerged six weeks after girdling. However, we observed minimal change in end-of-season leaf area index and no significant differences in annual ANPPw among disturbance severities or between disturbance types, suggesting continued C fixation by girdled trees sustained stand-scale wood production in the first growing season after disturbance. We hypothesized higher disturbance severities would favor the growth of early successional species but observed no significant difference between earlymore »and middle to late successional species’ contributions to ANPPw across the disturbance severity gradient. We conclude that ANPPw stability immediately following phloem disruption is dependent on the continued, but inevitably temporary, growth of phloem-disrupted trees. Our findings provide insight into the tree-to-ecosystem mechanisms supporting stand-scale wood production stability in the first growing season following a phloem-disrupting disturbance.« less

Abstract. The fortedata R package is an open data notebook from the Forest Resilience ThresholdExperiment (FoRTE) – a modeling and manipulative field experiment that teststhe effects of disturbance severity and disturbance type on carbon cyclingdynamics in a temperate forest. Package data consist of measurements ofcarbon pools and fluxes and ancillary measurements to help analyze andinterpret carbon cycling over time. Currently the package includes data andmetadata from the first three FoRTE field seasons, serves as a central,updatable resource for the FoRTE project team, and is intended as a resourcefor external users over the course of the experiment and in perpetuity.Further, it supports all associated FoRTE publications, analyses, andmodeling efforts. This increases efficiency, consistency, compatibility, and productivity while minimizing duplicated effort and error propagation thatcan arise as a function of a large, distributed and collaborative effort.More broadly, fortedata represents an innovative, collaborative way of approachingscience that unites and expedites the delivery of complementary datasets tothe broader scientific community, increasing transparency andreproducibility of taxpayer-funded science. The fortedata package is available via GitHub:https://github.com/FoRTExperiment/fortedata (last access: 19 February 2021), and detaileddocumentation on the access, used, and applications of fortedata are available athttps://fortexperiment.github.io/fortedata/ (last access: 19 February 2021). The first publicrelease, version 1.0.1 is also archived athttps://doi.org/10.5281/zenodo.4399601 (Atkins et al., 2020b). Allmore »data products are also available outside of thepackage as .csv files: https://doi.org/10.6084/m9.figshare.13499148.v1 (Atkins et al., 2020c).« less