Aim:

Climate warming is increasing fire activity in many of Earth’s forested ecosystems. Because fire is an important catalyst for change, investigation of post-fire vegetation response is crucial for understanding the potential for future conversions from forest to non-forest vegetation types. To better understand effects of wildfire and climate warming on forest recovery, we assessed the extent to which climate and terrain influence spatiotemporal variation in past and future post-fire tree regeneration.

Location:

Montane forests, Rocky Mountains, USA

Time Period:

1981-2099

Taxa Studied:

Pinus ponderosa; Pseudotsuga menziesii

Methods:

We developed a network of dendrochronological samples (n = 717) and field plots (n = 1301) from post-fire environments spanning a range of topographic and climatic settings. We then used boosted regression trees to predict annual suitability for post-fire seedling establishment and generalized linear mixed models to predict total post-fire seedling abundances, reconstructing recent trends in post-fire recovery and projecting future dynamics using three general circulation models (GCMs) under moderate and extreme emission scenarios.

Results:

Though 1981-2015 declines in growing season (April-September) precipitation were associated with declining suitability for seedling establishment, 2021-2099 trends in precipitation were widely variable among GCMs, leading to mixed projections of future establishment suitability. In contrast, climatic water deficit (CWD), strongly tied to warming temperature and increased evaporative demand, was projected to increase throughout our study area. Our projections strongly suggest that future increases in CWD and an increased frequency of extreme drought will reduce post-fire seedling abundances.

Main Conclusions:

Our findings highlight the key roles of warming and drying in declines in forest resilience to wildfire. The striking differences in projections of post-fire recovery between moderate and extreme emissions scenarios suggest that the most extreme impacts on forest resilience in the latter part of the 21^st century may be mitigated with aggressive emissions reductions in the next two decades.

This archive includes field data and various spatial datasets used in Rodman et al. (2020; Global Ecology and Biogeography).

Individual datasets in the Dryad archive include the following:

1) Gridded climate data (annual actual evapotranspiration, annual climatic water deficit, growing season precipitation) for the 1981-2015 period and future climate projections (2021-2099). All climate data were spatially downscaled to c. 250 m.

2) Statistical models and outputs (.rds objects, example spatial models, and summaries of statistical outputs)

3) Terrain variables (60-m resolution) of topographic position index and heat load index. Soil available water capacity at a 4km-resolution.

4) Shapefiles of fire perimeters included in the study and the boundary of the study area (i.e., EPA Level III Ecoregion #21)

5) Field data summarized in this study including 1) 1301 individual field plots characterizing post-fire conifer seedling abundance, forest structure, and ground cover and 2) 717 destructively sampled seedlings dated to establishment/germination year.

These data are a synthesis of five previously published studies that surveyed post-fire seedling abundance and the timing of seedling establishment, as well as previously unpublished data following the study design of Chambers et al. (2016). As methods of collection vary slightly among individual studies, we refer the user to the original published studies (listed below). See "README.txt" for a description of the processing and development of new datasets (i.e., gridded climate data, terrain variables, spatial models, and statistical models).

Chambers, M. E., P. J. Fornwalt, S. L. Malone, and M. A. Battaglia. 2016. Patterns of Conifer Regeneration Following High Severity Wildfire in Ponderosa Pine ñ Dominated Forests of the Colorado Front Range. Forest Ecology and Management 378:57ñ67.

Ouzts, J. R., Kolb, T. E., Huffman, D. W., and A. J. Sánchez Meador. 2015. Post-fire Ponderosa Pine Regeneration With and Without Planting in Arizona and New Mexico. Forest Ecology and Management 354:281ñ290.

Rother, M. T., and T. T. Veblen. 2016. Limited Conifer Regeneration Following Wildfires in Dry Ponderosa Pine Forests of the Colorado Front Range. Ecosphere 7:e01594.

Rother, M. T., and T. T. Veblen. 2017. Climate Drives Episodic Conifer Establishment after Fire in Dry Ponderosa Pine Forests of the Colorado. Forests 8:1-14.

Rodman, K. C., Veblen, T. T., Chapman, T. B., Rother, M. T., Wion, A. P., and M. D. Redmond. 2020b. Limitations to Recovery Following Wildfire in Dry Forests of Southern Colorado and Northern New Mexico, USA. Ecological Applications 30:e02001.

See "README.txt" and metadata within the compressed archive files for usage notes. We encourage the user to contact