Seed Bank Viability in Disturbed Longleaf Pine Sites

Abstract

Some of the most species-rich areas and highest concentrations of threatened and endangered species in the southeastern United States are found in wet savanna and flatwood longleaf pine (Pinus palustris Mill.) communities. Where intensive forestry practices have eliminated much of the natural understory of the longleaf ecosystem, the potential for reestablishment through a seed bank may present a valuable restoration opportunity. Longleaf pine sites converted to loblolly pine plantations and non-disturbed longleaf sites on the Coastal Plain of North Carolina were examined for seed bank presence and diversity. Conducting vegetation surveys and examining the seed bank using the seedling emergence technique allowed for verification of the seed bank presence, as well as evaluation of the quality of the seed bank on disturbed longleaf pine sites. Forty-three species and over 1,000 individuals germinated, and the seed banks of both the disturbed and non-disturbed stand types contained species not noted in the vegetation survey. Although many of these species were considered weedy and typical of disturbance, numerous taxa were indicative of stable longleaf pine communities. This study confirms both the presence and quality of seed banks in highly disturbed former longleaf pine sites, suggesting that the seed bank may be an important tool in restoration efforts.

Seed longevity of 12 native herbaceous species in a fire-maintained pine savanna after 8years of burial

“…A. stricta is of particular interest when restoring longleaf pine communities because of its former dominance in the understory and pyrogenic properties. Our finding that A. stricta seed is transient in the seed bank is inconsistent with earlier observations in which A. stricta was shown to be short-term persistent (Mulligan and Kirkman, 2002;Cox et al, 2004), but consistent with findings from several other field studies conducted in pine-dominated communities (Cohen et al, 2004;Maliakal et al, 2000;Andreau et al, 2009). These contradictory results suggest that A. stricta seed may be intolerant of buried conditions.…”

“…Restoring disturbed or degraded sites is challenging and costly because it has often required re-introduction of desirable vegetation by direct seeding or planting seedlings. However, reliance on the presence of desirable native ground cover species in the seed bank may be a cost-effective alternative to re-introducing native vegetation that has been eliminated through disturbance (Cohen et al, 2004). A greater understanding of the role of persistent seed banks and seed longevity is necessary for developing successful restoration strategies that may rely more heavily on the seed bank for natural recruitment of native species (Coffey and Kirkman, 2006).…”

“…Seed bank studies conducted in southeastern pinedominated communities to date have focused on species composition and quality of seed banks and report that seed banks typically show a lack of correspondence between aboveground and belowground community composition, the absence of A. stricta Michx. (wiregrass), and often an abundance of native but weedy herbaceous ground cover species (Maliakal et al, 2000;Cohen et al, 2004;Andreau et al, 2009). Additionally, legumes appear to be absent in the seed bank (Maliakal et al, 2000;Cohen et al, 2004) or were found very infrequently (Andreau et al, 2009).…”

“…(wiregrass), and often an abundance of native but weedy herbaceous ground cover species (Maliakal et al, 2000;Cohen et al, 2004;Andreau et al, 2009). Additionally, legumes appear to be absent in the seed bank (Maliakal et al, 2000;Cohen et al, 2004) or were found very infrequently (Andreau et al, 2009). These studies lack information pertaining to seed longevity of native species in seed banks and face problems relating to spatial and temporal variability.…”

“…seeds that germinate within the year of initial dispersal) or persistent (seeds that remain in the soil for more than 1 year) (Simpson et al, 1989). Additionally, spatial variability of persistent seed banks can be affected by seed predation, seed pathogenesis, senescence, and dispersal mechanisms and strategies, thereby influencing the spatial distribution of seeds (Hyatt and Casper, 2000;Cohen et al, 2004). The use of buried seed bags to answer questions relating to seed longevity in seed banks allows for the control of most spatial and temporal variables associated with seedling emergence studies.…”