Presentation on theme: "Fire Regimes and Successional Dynamics of Yellow Pine (Pinus) Stands in the Central Appalachian Mountains Henri D. Grissino-Mayer¹, Charles W. Lafon²,"— Presentation transcript:
Fire Regimes and Successional Dynamics of Yellow Pine (Pinus) Stands in the Central Appalachian Mountains Henri D. Grissino-Mayer¹, Charles W. Lafon², and Georgina DeWeese Wight¹ 1 Department of Geography, University of Tennessee, Knoxville, Tennessee; 2 Department of Geography, Texas A&M University, College Station, Texas Introduction Fire-adapted stands of yellow pine, in particular Table Mountain pine (Pinus pungens Lam.) (TMP) are prevalent on the xeric ridgetops and southwest facing slopes of the central Appalachian Mountains. Such stands historically have a heterogeneous mix of fire tolerant and intolerant species. In the past, fire acted as a natural disturbance process that altered forest composition and successional dynamics, but after several decades of fire suppression, ridgetop pine communities of the central Appalachian Mountains are in decline. The importance of Table Mountain pine lies in its ecological, not economic, value by increasing landscape diversity, by preventing post-fire erosion, and providing food and cover to a number of wildlife species. Table Mountain pine plays an important role in the stabilization and regeneration of mountain forests after major fire occurrences. Purpose Determine the historic and current fire regimes (including fire frequency, seasonality, and spatial scale) of yellow pine stands eight sites in the ridge and valley region and Blue Ridge Mountains of Virginia. Build the longest possible record of fire in the central Appalachians to determine the fire regimes under which pine stands developed, and the fire regime that existed before and during fire suppression. Evaluate the current age structure of the stands to assess the possible historic role of fires in initiating cohort establishment. Future goals of this study include analyzing the relationship between fire and climate, and determining the effect of climate variables on tree growth in the central Appalachians. The spatiotemporal changes and variations in fire regimes will be illustrated using a GIS to map past fires against site characteristics, to gain a better understanding of the spatial characteristics of fire. Site NameNational ForestCounty, VirginiaLat/Long Brush MountainJeffersonMontgomery(37º19’N, 80º20’W) Enterprise RoadJeffersonCraig(37º27’N, 80º6’W) Griffith KnobJeffersonBland(37º1’N, 81º13’W) Kelly MountainGeorge Washington(37º55’N, 79º2’W) Little Walker Mountain JeffersonWythe(37º3’N, 80º57’W) Mill MountainGeorge Washington(37º53’N, 79º38’W) North MountainJeffersonCraig(37º25’N, 80º10’W) Reddish KnobGeorge Washington(38º26’N, 79º9’W) Study Sites Laboratory Methods Tree-ring widths were measured on both increment cores and cross-sections. Increment cores were crossdated using visual and statistical (COFECHA) techniques. Chronologies developed using the cores were used to help crossdate the cross-sections. Each ring-width measurement series were then standardized and used to build master tree-ring chronologies for each sites using the program CRONOL. All fire scars from each cross-section were crossdated and the seasonality of each fire scar determined. All information regarding fire-scarred samples (fire scar date, season of fire, recorder/ non-recorder years, and inner/pith and outer/bark dates of the sample) was input into FHX2 software to create fire charts, generate descriptive statistics, and conduct statistical analyses. SiteYearsSeries Inter- correlation Mean Sensitivity Dated Time Series Brush Mountain1732-20030.590.30101 Enterprise Road1760-20020.530.3417 Griffith Knob1716-20030.560.32113 Kelly Mountain Little Walker Mountain Mill Mountain North Mountain1743-20030.570.34113 Reddish Knob Field Methods Aerial photographs will be used to locate sites for sampling in yellow pine stands at all three study sites. Aerial photos taken during winter months in leaf-off conditions will be studied to distinguish between hardwood-dominated and pine-dominated stands. Fire-scarred cross-sections and partial cross-sections will be taken from yellow pines found on four ridges at each study site. Three 50x20m age-structure plots were established at each site. In each plot, two cores were extracted from all canopy tree species. Non-pine species saplings were inventoried. Yellow pine saplings were node counted. One subplot (10x20m) within the plot was randomly chosen and every overstory species seedling was inventoried. Twenty mountain laurel shrubs were sampled to determine their ages and establishment dates. Results Table 2: Descriptive Statistics of Site Chronologies Figure 1(a) Fire-scarred TMP, North Mt.; 1(b) Yellow pine stands, Brush Mt.; 1(c) TMP cones, Kelly Mt.; 1(d) TMP, Mill Mt. Figure 2 (1-d): Composite Fire Scar Chronologies and Statistics Discussion When comparing the fire scar chronologies with the age-diameter graphs, we see that pulses of regeneration of all species occur after fire events. In some cases that is just one fire event, such as the 1926 fire on Griffith Knob and Brush Mountain. However, in some cases multiple smaller-scale fire are needed, such as the fires of the 1920s on North Mountain. The age-structure graphs illustrate the establishment dates of all species. There is a recent significant increase in other hardwoods at all sites except Griffith Knob, which is still experiencing pine regeneration. This is also shown on the seedling/sapling graphs. The forest on Griffith Knob is younger than those of the other sites, which is why pine regeneration is still occurring. However, our research shows that 70+ years of fire suppression has caused a shift in dominance from fire-tolerant oaks and pines to fire-intolerant hardwoods.