Mule Deer Impede Pando’s Recovery: Implications for Aspen Resilience from a Single-Genotype Forest

Aspen ecosystems (upland Populus-dominated forests) support diverse species assemblages in many parts of the northern hemisphere, yet are imperiled by common stressors. Extended drought, fire suppression, human development, and chronic herbivory serve to limit the sustainability of this keystone species. Here we assess conditions at a renowned quaking aspen (Populus tremuloides) grove—purportedly the largest living organism on earth—with ramifications for aspen biogeography globally. The “Pando” clone is 43 ha and estimated to contain 47,000 genetically identical aspen ramets. This iconic forest is threatened in particular by herbivory, and current management activities aim to reverse the potential for type conversion, likely to a non-forest state. We set out to gauge agents affecting recent deterioration through a network of monitoring plots and by examining a chronosequence of historic aerial photos to better understand the timing of putative departure from a sustainable course. Sixty-five permanent forest monitoring plots were located in three management regimes existing within Pando: no fencing, fencing with active and passive treatments, fencing with passive-only treatment. At each sample plot we measured live and dead mature trees, stem recruitment and regeneration, forest and shrub cover, browse level, and feces counts as a surrogate for ungulate presence. Ordination results indicate that aspen regeneration was the strongest indicator of overall forest conditions at Pando, and that mule deer (Odocoileus hemionus) presence strongly impacts successful regeneration. Additionally, fencing with active/passive treatments yielded the most robust regeneration levels; however, a fence penetrable by ungulates in the passive-only treatment most likely played a role in this outcome. The aerial photo sequence depicts various human intrusions over the past seven decades, but perhaps most telling, a decline in self-replacement beginning 30–40 years ago. Aspen communities in many locations in North American and Europe are impacted by unchecked herbivory. The Pando clone presents a unique opportunity for understanding browse mechanisms in a forest where tree genotype, closely aligned with growth and chemical defense, is uniform

Co-managing wildfire suppression in southwestern Utah

2 pagesIn a given area, there are commonly multiple agencies that manage wildfire suppression on different jurisdictions. These agencies can face divergent or even competing missions and mandates, yet must also address the cross-boundary nature of managing wildfire risk. Therefore, how can they more effectively co-manage fire suppression? Co-management in this context refers to communication, coordination, and collaboration between entities for meaningful collective action that shares the resources, costs, and burdens of managing fire risk. We examine factors that facilitated and limited co-management in a case study in southwestern Utah.FUNDER: Joint Fire Science Program

Large-Diameter Trees Dominate Snag and Surface Biomass Following Reintroduced Fire

The reintroduction of fire to landscapes where it was once common is considered a priority to restore historical forest dynamics, including reducing tree density and decreasing levels of woody biomass on the forest floor. However, reintroducing fire causes tree mortality that can have unintended ecological outcomes related to woody biomass, with potential impacts to fuel accumulation, carbon sequestration, subsequent fire severity, and forest management. In this study, we examine the interplay between fire and carbon dynamics by asking how reintroduced fire impacts fuel accumulation, carbon sequestration, and subsequent fire severity potential. Beginning pre-fire, and continuing 6 years post-fire, we tracked all live, dead, and fallen trees ≥ 1 cm in diameter and mapped all pieces of deadwood (downed woody debris) originating from tree boles ≥ 10 cm diameter and ≥ 1 m in length in 25.6 ha of an Abies concolor/Pinus lambertiana forest in the central Sierra Nevada, California, USA. We also tracked surface fuels along 2240 m of planar transects pre-fire, immediately post-fire, and 6 years post-fire. Six years after moderate-severity fire, deadwood ≥ 10 cm diameter was 73 Mg ha−1, comprised of 32 Mg ha−1 that persisted through fire and 41 Mg ha−1 of newly fallen wood (compared to 72 Mg ha−1 pre-fire). Woody surface fuel loading was spatially heterogeneous, with mass varying almost four orders of magnitude at the scale of 20 m × 20 m quadrats (minimum, 0.1 Mg ha−1; mean, 73 Mg ha−1; maximum, 497 Mg ha−1). Wood from large-diameter trees (≥ 60 cm diameter) comprised 57% of surface fuel in 2019, but was 75% of snag biomass, indicating high contributions to current and future fuel loading. Reintroduction of fire does not consume all large-diameter fuel and generates high levels of surface fuels ≥ 10 cm diameter within 6 years. Repeated fires are needed to reduce surface fuel loading

Use of biochar by sheep: impacts on diet selection, digestibility, and performance

The objective of this study was to determine the influence of biochar obtained from exothermic production of lodgepole pine (Pinus contorta) and quaking aspen (Populus tremuloides) on sheep performance and diet digestibility and on preference for a ration enriched with this carbon-based material. Twenty-four lambs were housed in individual pens and assigned to one of three treatment groups (eight animals per group), where they received: 1) a 60:40 ration of alfalfa:barley (Control), 2) an isoenergetic and isonitrogenous ration with alfalfa, barley, and 2% biochar (BC), and 3) a simultaneous offer of the Control and BC rations (Choice). Lambs were exposed to two consecutive feeding periods (Period 1: 13 d and Period 2: 21 d), representing time intervals where the evolution of intake, animal performance, and rumen parameters were assessed; in vivo digestibility was determined during the last 5 d of the study. Ration intake did not differ among groups of lambs (P \u3e 0.10), although during some days in Period 2, intake was greater for the BC and Choice groups than for the Control group (P \u3c 0.05). Lambs in Choice had a lower preference for BC than for the Control ration (Period 1: P \u3c 0.05; Period 2: P \u3c 0.10), although they incorporated a substantial amount of BC (39 and 40%, for Periods 1 and 2, respectively) into their diets. No differences in body weight gains (ADG) or gain-to-feed ratios were found among groups of animals (P \u3e 0.10), although dry matter digestibility and digestible dry matter intake was greater for lambs in the BC group than for lambs in Control group (P \u3c 0.05). The ruminal concentration of the volatile acid acetate in Period 2 was greater for BC than for Choice (P \u3c 0.05). During the same period, the concentration of valerate and ruminal pH values were greater in BC than in Control (P \u3c 0.05). Thus, the addition of biochar to grain-based diets enhanced diet digestibility and influenced some ruminal parameters in lambs. Nevertheless, these positive effects were not reflected in significant improvements on ADG or feed conversion efficiencies. Lambs offered choices between Control and BC rations formed a diet with concentrations of biochar of ~1.2%, suggesting that these animals would tolerate such levels without reductions in ration palatability

Code Descriptions for “Managed wildfire: A strategy limited by terminology, risk perception, and ownership boundaries.”

Files include README and Codebook in two formats.Federal land managers in the United States are permitted to manage wildfires with strategies other than full suppression under appropriate conditions to achieve natural resource objectives. However, policy and scientific support for “managed wildfire” appear insufficient to support its broad use. We conducted case studies in northern New Mexico and southwestern Utah to examine how managers and stakeholders navigated shifting barriers and opportunities to use managed wildfire from 2018-2021. Use of managed wildfire was fostered through an active network of civil society partnerships in one case, and strong interagency cooperation and existing policies and plans in the other. In both, the COVID-19 pandemic, drought, and agency direction curtailed recent use. Local context shapes wildfire response strategies, yet centralized decision making and policy also can enable or constrain them. Future research could refine understanding of social factors in incident decision making, and evaluation of risks and tradeoffs in wildfire response.This project was funded by the Joint Fire Science Program (Project # 17-1-06-6) in 2017 with the objective exploring how entities involved in wildfire mitigation and suppression can better coordinate actions before, during, and after wildfires. A total of 40 government agency and civil society actors engaged in wildfire mitigation and response in two different case studies: northern New Mexico (Santa Fe and Carson National Forests) and southwestern Utah (Dixie National Forest) were interviewed between fall 2018 and spring 2019. Repeat interviews of 12 selected interviewees in each case study occurred during spring-summer 2021. These data consist of themes used to code these interviews, such as factors shaping wildfire response strategies, examples of using managed fire, and pandemic impacts

Comparing stand-alone endovascular embolization versus stereotactic radiosurgery in the treatment of arteriovenous malformations with Spetzler-Martin grades I–III: a propensity score matched study

BackgroundArteriovenous malformations (AVMs) are uncommon cerebral lesions that can cause significant neurological complications. Surgical resection is the gold standard for treatment, but endovascular embolization and stereotactic radiosurgery (SRS) are viable alternatives.ObjectiveTo compare the outcomes of endovascular embolization versus SRS in the treatment of AVMs with Spetzler-Martin grades I–III.MethodsThis study combined retrospective data from 10 academic institutions in North America and Europe. Patients aged 1 to 90 years who underwent endovascular embolization or SRS for AVMs with Spetzler-Martin grades I–III between January 2010 and December 2023 were included.ResultsThe study included 244 patients, including 84 who had endovascular embolization and 160 who had SRS. Before propensity score matching (PSM), complete obliteration at the last follow-up was achieved in 74.5% of the SRS group compared with 57.8% of the embolization group (OR=0.47; 95% CI 0.26 to 0.48; P=0.01). After propensity score matching, SRS still achieved significantly higher occlusion rates at last follow-up (78.9% vs 55.3%; OR=0.32; 95% CI 0.12 to 0.90; P=0.03).Hemorrhagic complications were higher in the embolization group than in the SRS group, although this difference did not reach statistical significance after PSM (13.2% vs 2.6%; OR=5.6; 95% CI 0.62 to 50.47; P=0.12). Similarly, re-treatment rate was higher in the embolization group (10.5% vs 5.3%; OR=2.11; 95% CI 0.36 to 12.31; P=0.40) compared with the SRS group.ConclusionOur findings indicate that SRS has a significantly higher obliteration rate at last follow-up compared with endovascular embolization. Also, SRS has a higher tendency for fewer hemorrhagic complications and lower re-treatment rate. Further prospective studies are needed