Ecosystem services may outlast their ecosystems: Regional carbon stocks minimally affected by multiple disturbances and coniferous-to-deciduous regime change

Background/Question/Methods

Ecosystem disturbances such as wildfire or insect outbreaks are disruptive to socioeconomic systems, but are also catalysts of the inevitable change inherent in a warming climate.  Climate change brings with it the potential for increases in both disturbances and disturbance interactions - situations where multiple events impact the same area in a short period of time. These interactions can overwhelm the resistance and resilience mechanisms of ecosystems, leading to more severe effects and long-lasting implications for landscape structure and function.  Ecosystem services, such as water filtration, wildlife habitat, or wood production may be altered as a result.  The presented study identifies a particular ecosystem service, carbon storage, and looks at the implications of three disturbances in a Colorado coniferous subalpine forest:  wind, logging, and fire.  Using field surveys (112 plots), the ~12,000 ha landscape is experiencing spatially variable recovery resulting from the interaction. Recovery was modeled using the Fire and Fuel Extension (FFE) of the Forest Vegetation Simulator (FVS) to investigate the effect of the disturbance interactions on future carbon storage.  Model runs were initiated using field data and bootstrapped to develop a range of 100-year projections. 

Results/Conclusions

While a significant loss in coniferous forest cover was found in many areas (down to 0 conifer seedlings/hectare) as a result of the interactions, future carbon sequestration seems unexpectedly resilient as a result of a large influx of aspen (up to 15,000 seedlings/ha) spread across most disturbance histories.  No significant variation in aboveground carbon stocks is expected despite shifts from coniferous to deciduous ecosystems in areas of severe blowdown and fire in the near term; long-term alterations in C-stocks are more uncertain, but may occur due to the loss of coniferous species in high blowdown+fire areas.  Different climate change scenarios produce radically different C-stock trends, with alternate regimes becoming established in some models.  C-stocks will likely become more heterogeneous across the landscape.  This landscape demonstrates the type of adaptive change which will likely become more common as disturbance interactions increase in frequency - potentially dramatic changes in community structure, but differing impacts on specific ecosystem services.  A change in forest types or loss of forest to meadow does not necessarily mean a loss in some ecosystem services; individual services may also be enhanced or unaffected.  Adaptation recognizes that ecosystem change is, in many cases, inevitable but particular ecosystem services may be maintained or enhanced through those very same changes, management interventions, or both.