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Recovery of Forested Hilltops Impacted by Fire


Historically, southwestern ponderosa pine forests were open and park-like with large pine trees, a healthy grass cover on the forest floor, and a low abundance of small trees or underbrush. In addition, prior to Euro-American settlement (1870-1890), frequent, low-intensity fires occurred in these ecosystems every 2-20 years. Due to different human activities, exclusion of fire and lack of other disturbances, the historical structures of some of these forests has been greatly altered. Present day characteristics of these forests include: increased tree mortality, irruption of insects and diseases, a decrease in herbaceous plant and shrub quantity, and higher fuel loads. These conditions encourage fires that burn at intense and detrimental temperatures rather than more moderate temperatures which promote forest health. There is a lot of research being done to understand how restore these ecosystems back to their healthy historical structures.

My project will be focused on how wildfire severity affects the seeds buried in the soil and what consequences this has for vegetative regeneration in a southwestern Ponderosa pine forest. I will also be looking at the effects of soil erosion due to fire severity on the movement of seeds. The study area is located by the pueblo of Jemez, New Mexico in the Valles Caldera National Preserve and has recently experienced a fire (the Thompson Ridge Fire) of varying severities during the summer of 2013. The vegetation in the study area consists mostly of ponderosa pine forest, with smaller proportions of mixed conifer forests present on north-facing slopes and a variety of grasses and grass-like vegetation. Though numerous studies have characterized the soil seed bank in southwest ponderosa pine forests pre-fire and post fire, studies that have examined seed movement due to erosion, which could affect the regeneration of the vegetation, are lacking. The objectives of my study are to analyze how different fire severities and/or slopes affect how the soil seed bank in this ecosystem changes over time, the extent of post-fire erosion, how seeds are displaced due to post-fire erosion, and how these qualities and processes affect the regeneration of vegetation after a wildfire.

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