Robert M. Scheller

Simulating landscape-scale effects of fuels treatments in the Sierra Nevada, California, USA

In many coniferous forests of the western United States, wildland fuel accumulation and projected climate conditions increase the likelihood that fires will become larger and more intense. Fuels treatments and prescribed fire are widely recommended, but there is uncertainty regarding their ability to reduce the severity of subsequent fires at a landscapescale.Ourobjectivewastoinvestigatetheinteractionsamonglandscape-scalefireregimes,fuelstreatmentsand fireweatherinthesouthernSierraNevada,California.Weusedaspatiallydynamicmodelofwildfire,successionandfuels management to simulate long-term (50 years), broad-scale (across 2.2 � 10 6 ha) effects of fuels treatments. We simulated thin-from-below treatments followed by prescribed fire under current weather conditions and under more severe weather. Simulated fuels management minimised the mortality of large, old trees, maintained total landscape plant biomass and extended fire rotation, but effects varied based on elevation, type of treatment and fire regime. The simulated area treated had a greater effect than treatment intensity, and effects were strongest where more fires intersected treatments and when simulatedweatherconditionswere moresevere. Inconclusion,fuelstreatmentsinconiferforestspotentiallyminimise the ecological effects of high-severity fire at a landscape scale provided that 8% of the landscape is treated every 5 years, especially if future fire weather conditions are more severe than those in recent years.

Studying fire mitigation strategies in multi-ownership landscapes: balancing the management of fire-dependent ecosystems and fire risk

Public forests are surrounded by land over which agency managers have no control, and whose owners expect the public forest to be a “good neighbor.” Fire risk abatement on multi-owner landscapes containing flammable but fire-dependent ecosystems epitomizes the complexities of managing public lands. We report a case study that applies a landscape disturbance and succession model (LANDIS) to evaluate the relative effectiveness of four alternative fire mitigation strategies on the Chequamegon-Nicolet National Forest (Wisconsin, USA), where fire-dependent pine and oak systems overlap with a rapidly developing wildland–urban interface (WUI). We incorporated timber management of the current forest plan and fire characteristics (ignition patterns, fire sizes, and fuel-specific fire spread rates) typical for the region under current fire suppression policies, using a combination of previously published fire analyses and interactive expert opinion from the national forest. Of the fire mitigation strategies evaluated, reduction of ignitions caused by debris-burning had the strongest influence on fire risk, followed by the strategic redistribution of risky forest types away from the high ignition rates of the WUI. Other treatments (fire breaks and reducing roadside ignitions) were less effective. Escaped fires, although rare, introduced significant uncertainty in the simulations and are expected to complicate fire management planning. Simulations also show that long-term maintenance of fire-dependent communities (that is, pine and oak) representing the greatest forest fire risk requires active management. Resolving conflict between the survival of fire-dependent communities that are regionally declining and continued rural development requires strategic planning that accounts for multi-owner activities.

Climate change effects on northern Great Lake (USA) forests: A case for preserving diversity

Under business as usual (BAU) management, stresses posed by climate change may exceed the ability of Great Lake forests to adapt. Temperature and precipitation projections in the Great Lakes region are expected to change forest tree species composition and productivity. It is unknown how a change in productivity and/or tree species diversity due to climate change will affect the relationship between diversity and productivity. We assessed how forests in two landscapes (i.e., northern lower Michigan and northeastern Minnesota, USA) would respond to climate change and explored the diversity-productivity relationship under climate change. In addition, we explored how tree species diversity varied across landscapes by soil type, climate, and management. We used a spatially dynamic forest ecosystem model, LANDIS-II, to simulate BAU forest management under three climate scenarios (current climate, low emissions, and high emissions) in each landscape. We found a positive relationship between diversity and productivity only under a high emissions future as productivity declined. Within landscapes, climate change simulations resulted in the highest diversity in the coolest climate regions and lowest diversity in the warmest climate region in Minnesota and Michigan, respectively. Simulated productivity declined in both landscapes under the high emissions climate scenario as species such as balsam fir (Abies balsamea) declined in abundance. In the Great Lakes region, a high emissions future may decrease forest productivity creating a more positive relationship between diversity and productivity. Maintaining a diversity of tree species may become increasingly important to maintain the adaptive capacity of forests.

Increasing the reliability of ecological models using modern software engineering techniques.

Modern software development techniques are largely unknown to ecologists. Typically, ecological models and other software tools are developed for limited research purposes, and additional capabilities are added later, usually in an ad hoc manner. Modern software engineering techniques can substantially increase scientific rigor and confidence in ecological models and tools. These techniques have the potential to transform how ecological software is conceived and developed, improve precision, reduce errors, and increase scientific credibility. We describe our re-engineering of the forest landscape model LANDIS (LANdscape DIsturbance and Succession) to illustrate the advantages of using common software engineering practices.

Disturbance and climate microrefugia mediate tree range shifts during climate change

ContextMany tree species will shift their distribution as the climate continues to change. To assess species’ range changes, modeling efforts often rely on climatic predictors, sometimes incorporating biotic interactions (e.g. competition or facilitation), but without integrating topographic complexity or the dynamics of disturbance and forest succession.ObjectivesWe investigated the role of ‘safe islands’ of establishment (“microrefugia”) in conjunction with disturbance and succession, on mediating range shifts.MethodsWe simulated eight tree species and multiple disturbances across an artificial landscape designed to highlight variation in topographic complexity. Specifically, we simulated spatially explicit successional changes for a 100-year period of climate warming under different scenarios of disturbance and climate microrefugia.ResultsDisturbance regimes play a major role in mediating species range changes. The effects of disturbance range from expediting range contractions for some species to facilitating colonization of new ranges for others. Microrefugia generally had a significant but smaller effect on range changes. The existence of microrefugia could enhance range persistence but implies increased environmental heterogeneity, thereby hampering migration under some disturbance regimes and for species with low dispersal capabilities. Species that gained suitable habitat due to climate change largely depended on the interaction between species life history traits, environmental heterogeneity and disturbance regimes to expand their ranges.ConclusionsDisturbance and microrefugia play a key role in determining forest range shifts during climate change. The study highlights the urgent need of including non-deterministic successional pathways into climate change projections of species distributions.

Climate-Suitable Planting as a Strategy for Maintaining Forest Productivity and Functional Diversity

Within the time frame of the longevity of tree species, climate change will change faster than the ability of natural tree migration. Migration lags may result in reduced productivity and reduced diversity in forests under current management and climate change. We evaluated the efficacy of planting climate-suitable tree species (CSP), those tree species with current or historic distributions immediately south of a focal landscape, to maintain or increase aboveground biomass productivity, and species and functional diversity. We modeled forest change with the LANDIS-II forest simulation model for 100 years (2000-2100) at a 2-ha cell resolution and five-year time steps within two landscapes in the Great Lakes region (northeastern Minnesota and northern lower Michigan, USA). We compared current climate to low- and high-emission futures. We simulated a low-emission climate future with the Intergovernmental Panel on Climate Change (IPCC) 2007 B1 emission scenario and the Parallel Climate Model Global Circulation Model (GCM). We simulated a high-emission climate future with the IPCC A1FI emission scenario and the Geophysical Fluid Dynamics Laboratory (GFDL) GCM. We compared current forest management practices (business-as-usual) to CSP management. In the CSP scenario, we simulated a target planting of 5.28% and 4.97% of forested area per five-year time step in the Minnesota and Michigan landscapes, respectively. We found that simulated CSP species successfully established in both landscapes under all climate scenarios. The presence of CSP species generally increased simulated aboveground biomass. Species diversity increased due to CSP; however, the effect on functional diversity was variable. Because the planted species were functionally similar to many native species, CSP did not result in a consistent increase nor decrease in functional diversity. These results provide an assessment of the potential efficacy and limitations of CSP management. These results have management implications for sites where diversity and productivity are expected to decline. Future efforts to restore a specific species or forest type may not be possible, but CSP may sustain a more general ecosystem service (e.g., aboveground biomass).

Michigan forest ecosystem vulnerability assessment and synthesis: a report from the Northwoods Climate Change Response Framework project

Forests in northern Michigan will be affected directly and indirectly by a changing climate during the next 100 years. This assessment evaluates the vulnerability of forest ecosystems in Michigans eastern Upper Peninsula and northern Lower Peninsula to a range of future climates. Information on current forest conditions, observed climate trends, projected climate changes, and impacts to forest ecosystems was considered in order to draw conclusions on climate change vulnerability. Upland spruce-fir forests were determined to be the most vulnerable, whereas oak associations and barrens were determined to be less vulnerable to projected changes in climate. Projected changes in climate and the associated ecosystem impacts and vulnerabilities will have important implications for economically valuable timber species, forest-dependent wildlife and plants, recreation, and long-range planning.

Divergent Carbon Dynamics under Climate Change in Forests with Diverse Soils, Tree Species, and Land Use Histories

Accounting for both climate change and natural disturbances—which typically result in greenhouse gas emissions—is necessary to begin managing forest carbon sequestration. Gaining a complete understanding of forest carbon dynamics is, however, challenging in systems characterized by historic over-utilization, diverse soils and tree species, and frequent disturbance. In order to elucidate the cascading effects of potential climate change on such systems, we projected forest carbon dynamics, including soil carbon changes, and shifts in tree species composition as a consequence of wildfires and climate change in the New Jersey pine barrens (NJPB) over the next 100 years. To do so, we used the LANDIS-II succession and disturbance model combined with the CENTURY soil model. The model was calibrated and validated using data from three eddy flux towers and the available empirical or literature data. Our results suggest that climate change will not appreciably increase fire sizes and intensity. The recovery of C stocks following substantial disturbances at the turn of the 20th century will play a limited but important role in this system. In areas characterized by high soil water holding capacity, reduced soil moisture may lead to lower total C and these forests may switch from being carbon sinks to becoming carbon neutral towards the latter part of the 21st century. In contrast, other areas characterized by lower soil water holding capacity and drought tolerant species are projected to experience relatively little change over the next 100 years. Across all soil types, however, the regeneration of many key tree species may decline leading to longer-term (beyond 2100) risks to forest C. These divergent responses were largely a function of the dominant tree species, and their respective temperature and soil moisture tolerances, and soil water holding capacity. In summary, the system is initially C conservative but by the end of the 21st century, there is increasing risk of de-stabilization due to declining growth and regeneration.

Measuring and managing resistance and resilience under climate change in northern Great Lake forests (USA)

ContextClimate change will have diverse and interacting effects on forests over the next century. One of the most pronounced effects may be a decline in resistance to chronic change and resilience to acute disturbances. The capacity for forests to persist and/or adapt to climate change remains largely unknown, in part because there is not broad agreement how to measure and apply resilience concepts.ObjectivesWe assessed the interactions of climate change, resistance, resilience, diversity, and alternative management of northern Great Lake forests.MethodsWe simulated two landscapes (northern Minnesota and northern lower Michigan), three climate futures (current climate, a low emissions trajectory, and a high emissions trajectory), and four management regimes [business as usual, expanded forest reserves, modified silviculture, and climate suitable planting (CSP)]. We simulated each scenario with a forest landscape simulation model. We assessed resistance as the change in species composition over time. We assessed resilience and calculated an index of resilience that incorporated both recovery of pre-fire tree species composition and aboveground biomass within simulated burned areas.ResultsResults indicate a positive relationship between diversity and resistance within low diversity areas. Simulations of the high emission climate future resulted in a decline in both resistance and resilience.ConclusionsOf the management regimes, the CSP regime resulted in some of the greatest resilience under climate change although our results suggest that differences in forest management are largely outweighed by the effects of climate change. Our results provide a framework for assessing resistance and resilience relevant and valuable to a broad array of ecological systems.

Evidence for a recent increase in forest growth is questionable

In a recent article, McMahon et al. (1) examined forest-plot biomass accumulation across a range of stands in the mid-Atlantic United States and suggest that climate change and trends in atmospheric CO2 explain an increase in forest growth. To show this increase, they fit a simple model to live above-ground forest biomass (AGB) as a function of stand age, and then propose that the derivative of this model is the expected rate of ensemble biomass change (). They conclude that biomass changes within census plots that exceed the ensemble expectation constitute recent increases in growth rates.