Through droughts and hurricanes: Tree mortality, forest structure, and biomass production in a coastal swamp targeted for restoration in the Mississippi River Deltaic Plain

The Complexity of Catastrophic Wind Impacts on Temperate Forests

“…As an ecological factor, catastrophic wind events not only cause extensive damage to trees, but also affect many aspects of the disturbed forests including community structure, individual tree growth, tree regeneration, species diversity, and ecosystem function (Coutts & Grace, 1993;Ennos, 1997;Martin & Ogden, 2006;Bellingham, 2008;Hoeppner et al, 2008;Zeng et al, 2009). Although catastrophic windstorms are easily seen to have major impacts on forest structure, the longer-term effects on less conspicuous ecosystem attributes such as species composition and diversity are more complex, and at smaller scales of observation are relatively unpredictable (DeCoster, 1996;McMaster, 2005;Oswalt & Oswalt, 2008).…”

Decline of the Maurepas Swamp, Pontchartrain Basin, Louisiana, and Approaches to Restoration

“…Mean tree height, basal area ( Figure 4) and tree net primary production ( Figure 10) were highest at the sites receiving point and nonpoint sources of fresh water (Throughput sites), intermediate at those with stagnant, permanently flooded soils (Relict sites), and lowest at Degraded sites prone to saltwater intrusion. For the relationship between forested basal area and long-term salinity we expected to find a threshold relationship for baldcypress and water tupleo with decreased basal area beginning at about 2 ppt and 1 ppt, respectively [22,[41][42][43]. Instead, all species experienced exponential decline in basal area beginning at a chronic salinity as low as 0.5 ppt ( Figure 14).…”

“…Water tupelo, ash, and swamp red maple cannot tolerate the periodic salinity conditions during drought of 2-4 ppt found at these sites [10,24]. Likewise, the relatively low stem densities observed at the Relict swamp sites are primarily the result of the decreased abundance of ash and swamp red maple in the impounded and stagnant hydrologic regimes characteristic of these sites [22]. To date > 32% of the > 2000 trees monitored during this study have died, with some Degraded sites experiencing complete tree mortality.…”

“…Instead, all species experienced exponential decline in basal area beginning at a chronic salinity as low as 0.5 ppt ( Figure 14). As expected, basal area of baldcypress had the weakest relationship with increased salinity, as it is the most salt tolerant of these swamp tree species [44][45][46][47] These results indicate when baldcypress-water tupelo swamps are stressed by other factors such as permanent flooding, stagnant conditions, and nutrient limitation, they appear to be more sensitive to salinity than indicated by past greenhouse experiments [9,23,[44][45][46][47] and field studies [9,22,[41][42][43].…”

“…As a result of these impacts, tree mortality rates are high and much of the swamp is transitioning to marsh and open water [10]. There is very little closed canopy left and most of the trees in the swamp will not naturally regenerate due to semi-permanent to permanent flooding [9][10][11][19][20][21][22][23][24]. The vegetation under the swamp canopy is mostly weakly rooted marsh and shrub species or open water [10].…”