Moisture and vegetation cover limit ponderosa pine regeneration in high-severity burn patches in the southwestern US

Abstract Background Fire regimes are shifting in ponderosa pine (Pinus ponderosa Lawson & C. Lawson)-dominated forests, raising concern regarding future vegetation patterns and forest resilience, particularly within high-severity burn patches. The southwestern US has recently experienced a marked increase in large fires that produce large, high-severity patch interiors, with few surviving trees. These areas could be more susceptible for forest loss and conversions to alternative vegetation types than areas closer to the forest edge with more available seed sources. To better understand forest recovery, we surveyed ponderosa pine regeneration within edge and core areas (>200 m from edge) of high-severity patches in ten fires that burned between 1996 to 2008 across Arizona and New Mexico, USA. Specifically, we compared regeneration density, height, and canopy cover in patch edge and core areas and used generalized linear models to investigate the abiotic and biotic factors that contribute to ponderosa pine seedling establishment and density. Results High-severity burn-patch edge and core plots were not significantly different in seedling density, height, or canopy cover across fires. Seedling establishment was more likely at higher-elevation mesic sites and less likely when Gambel oak (Quercus gambelii Nutt.) was more abundant. Seedling density was negatively impacted by shrub, grass, and Gambel oak cover. Conclusions Regeneration density varied among fires but analysis of regeneration in aggregated edge and core plots showed that abundance of seed availability was not the sole factor that limited ponderosa pine regeneration, probably because of surviving tree refugia within high-severity burn patches. Furthermore, our findings emphasize that ponderosa pine regeneration in our study area was significantly impacted by xeric topographic environments and vegetation competition. Continued warm and dry conditions and increased wildfire activity may delay the natural recovery of ponderosa pine forests, underscoring the importance of restoration efforts in large, high-severity burn patches.

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Double whammy: high-severity fire and drought in ponderosa pine forests of the Southwest

Canadian Journal of Forest Research ◽

10.1139/cjfr-2012-0404 ◽

2013 ◽

Vol 43 (6) ◽

pp. 570-583 ◽

Cited By ~ 76

Author(s):

Melissa Savage ◽

Joy Nystrom Mast ◽

Johannes J. Feddema

Keyword(s):

Pinus Ponderosa ◽

Ponderosa Pine ◽

Fire Regime ◽

American Southwest ◽

Forest Recovery ◽

Type Model ◽

Ponderosa Pine Forests ◽

High Severity ◽

Pine Regeneration ◽

Drought Conditions

We examine regeneration dynamics across landscapes under extreme climate conditions and a human-altered fire regime in ponderosa pine (Pinus ponderosa Douglas ex Lawson & C. Lawson) forests of the American Southwest. Our research asks how well these forests recover when unprecedented conditions of a high-severity fire regime combine with historical drought conditions. Tree recruitment is documented at five sites in New Mexico after high-severity fires that burned forests in the drought that prevailed from ∼1945 to 1958. We develop a water-balance type model to evaluate how altered microclimate conditions in the years after a fire and during a drought may inhibit ponderosa pine regeneration in comparison with drought conditions alone. We empirically identify two pathways of forest recovery following high-severity fires during drought: recovery to nonforest types, either dense shrubfields or shrubs in grasslands (four sites) or recovery to hyperdense forest (one site). Model simulations predict fewer favorable opportunities for germination, fewer periods favorable for seedling establishment, shortening of favorable establishment periods, and more adverse conditions because of later spring and earlier fall hard freezes. Our research suggests that a specific climate window critical to the capacity of southwestern ponderosa pine trees to regenerate is narrowed by a synchronous occurrence of high-severity fire and drought.

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Environmental Influences on Density and Height Growth of Natural Ponderosa Pine Regeneration following Wildfires

Fire ◽

10.3390/fire4040080 ◽

2021 ◽

Vol 4 (4) ◽

pp. 80

Author(s):

Darcy H. Hammond ◽

Eva K. Strand ◽

Penelope Morgan ◽

Andrew T. Hudak ◽

Beth A. Newingham

Keyword(s):

Ponderosa Pine ◽

Seedling Establishment ◽

Height Growth ◽

Tree Regeneration ◽

Forest Recovery ◽

Productivity Index ◽

Burn Severity ◽

Seedling Density ◽

Pine Regeneration ◽

Precipitation Seasonality

Over the past century the size and severity of wildfires, as well as post-fire recovery processes (e.g., seedling establishment), have been altered from historical levels due to management policies and changing climate. Tree seedling establishment and growth drive future overstory tree dynamics after wildfire. Post-fire tree regeneration can be highly variable depending on burn severity, pre-fire forest condition, tree regeneration strategies, and climate; however, few studies have examined how different abiotic and biotic factors impact seedling density and growth and the interactions among those factors. We measured seedling density and height growth in the period 2015–2016 on three wildfires that burned in ponderosa pine (Pinus ponderosa) forests in the period 2000–2007 across broad environmental and burn severity gradients. Using a non-parametric multiplicative regression model, we found that downed woody fuel load, duff depth, and fall precipitation best explained variation in seedling density, while the distance to nearest seed tree, a soil productivity index, duff depth, and spring precipitation as snow best explained seedling height growth. Overall, results highlight the importance of burn severity and post-fire climate in tree regeneration, although the primary factors influencing seedling density and height growth vary. Drier conditions and changes to precipitation seasonality have the potential to influence tree establishment, survival, and growth in post-fire environments, which could lead to significant impacts for long-term forest recovery.

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Some Lessons Learned on Early Survival and Growth of Containerized, Locally-Sourced Ponderosa Pine Seedlings in the Davis Mountains of Western Texas, US

Forests ◽

10.3390/f10030267 ◽

2019 ◽

Vol 10 (3) ◽

pp. 267

Author(s):

Lance Vickers ◽

James Houser ◽

James Rooni ◽

James Guldin

Keyword(s):

Ponderosa Pine ◽

Monsoon Season ◽

Vegetation Management ◽

Lessons Learned ◽

Artificial Regeneration ◽

Ponderosa Pine Forests ◽

Pine Seedlings ◽

Pine Regeneration ◽

Davis Mountains ◽

Early Survival

The ponderosa pine forests in the Davis Mountains of western Texas recently experienced a major mortality event caused, in part, by an extended regional drought that predisposed trees and stands to mortality from both western pine beetle and wildfires. The loss of many overstory pines and the scarcity of natural ponderosa pine regeneration pose a considerable challenge to restoration. A commissioned study investigated artificial regeneration using containerized ponderosa pine seedlings with multiple planting seasons and vegetation management alternatives. Early survival was statistically greater for dormant season plantings than monsoon season plantings. Vegetation management treatments influenced early growth, survival, and herbivory rates. Physical weed control, which consisted of fibrous weed mats around the base of planted seedlings, showed early advantages over some vegetation management treatments in growth, survival and herbivory deterrence, but all vegetation management treatments had similar survival and herbivory results after 2.5 years. Early survival was poor in all treatments, mainly due to herbivory, which was identified as the principal short-term obstacle to artificial regeneration of ponderosa pine in the Davis Mountains. The larger question regarding feasibility of recovery in this isolated population, particularly if local climatic conditions become increasingly unfavorable, remains.

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Influence of Gambel Oak on Breeding Birds in Ponderosa Pine Forests of Northern Arizona

The Condor ◽

10.2307/1369714 ◽

1998 ◽

Vol 100 (3) ◽

pp. 485-492 ◽

Cited By ~ 18

Author(s):

Steven S. Rosenstock

Keyword(s):

Ponderosa Pine ◽

Breeding Birds ◽

Pine Forests ◽

Ponderosa Pine Forests ◽

Northern Arizona ◽

Gambel Oak

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Phenology Patterns Indicate Recovery Trajectories of Ponderosa Pine Forests After High-Severity Fires

Remote Sensing ◽

10.3390/rs11232782 ◽

2019 ◽

Vol 11 (23) ◽

pp. 2782 ◽

Cited By ~ 2

Author(s):

Jessica J. Walker ◽

Christopher E. Soulard

Keyword(s):

Time Series ◽

Pinus Ponderosa ◽

Ponderosa Pine ◽

Google Earth ◽

Thematic Mapper ◽

Pine Forests ◽

Land Resource ◽

Ponderosa Pine Forests ◽

High Severity ◽

Peak Value

Post-fire recovery trajectories in ponderosa pine (Pinus ponderosa Laws.) forests of the southwestern United States are increasingly shifting away from pre-burn vegetation communities. This study investigated whether phenological metrics derived from a multi-decade remotely sensed imagery time-series could differentiate among grass, evergreen shrub, deciduous, or conifer-dominated replacement pathways. We focused on 10 fires that burned ponderosa pine forests in Arizona and New Mexico, USA before the year 2000. A total of 29 sites with discernable post-fire recovery signals were selected within high-severity burn areas. At each site, we used Google Earth Engine to derive time-series of normalized difference vegetation index (NDVI) signals from Landsat Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager data from 1984 to 2017. We aggregated values to 8- and 16-day intervals, fit Savitzky–Golay filters to each sequence, and extracted annual phenology metrics of amplitude, base value, peak value, and timing of peak value in the TIMESAT analysis package. Results showed that relative to post-fire conditions, pre-burn ponderosa pine forests exhibit significantly lower mean NDVI amplitude (0.14 vs. 0.21), higher mean base NDVI (0.47 vs. 0.22), higher mean peak NDVI (0.60 vs. 0.43), and later mean peak NDVI (day of year 277 vs. 237). Vegetation succession pathways exhibit distinct phenometric characteristics as early as year 5 (amplitude) and as late as year 20 (timing of peak NDVI). This study confirms the feasibility of leveraging phenology metrics derived from long-term imagery time-series to identify and monitor ecological outcomes. This information may be of benefit to land resource managers who seek indicators of future landscape compositions to inform management strategies.

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