Moving from Generalisations to Specificity about Mangrove –Saltmarsh Dynamics

Abstract

Spatial and temporal variability in factors influencing mangrove establishment and survival affects the distribution of mangrove, particularly near their latitudinal limit, where mangrove expansion into saltmarsh is conspicuous. In this paper the spatial variability in mangrove distribution and variability in factors influencing mangrove establishment and survival during the Quaternary period are reviewed, focussing on research at latitudinal limits in Australia and mainland USA. Despite similarities in the response of mangrove to some drivers, the expression of these drivers is both spatially and temporally variable, demonstrating the need for analyses of mangrove-saltmarsh dynamics to move beyond generalisations and incorporate regional and local-scale specificity. We propose i) that precursory recognition that 'correlation does not mean causation' is inadequate and assumptions, caveats, and limitations should be clearly articulated in correlative studies; ii) experimental design in manipulative experiments must also articulate the spatial and temporal scale to which the analysis is relevant; and iii) analyses that draw from a range of methods will provide greater confidence. Integrated research programs that transect spatial and temporal scales and incorporate a range of techniques are essential to improve projections. Mangrove-saltmarsh distribution research should move beyond simple models that assume equilibrium between realised and fundamental niches.

Is the central‐marginal hypothesis a general rule? Evidence from three distributions of an expanding mangrove species, Avicennia germinans (L.) L

“…Considering ongoing, rapid expansion at all USA range margins (Rogers & Krauss, ) and further expansion forecast with climate change (Cavanaugh et al, ; Osland, Day, et al, ), plus the fact that range margins are probably the primary source of recruits beyond distributional limits (Hampe, ), USA range‐margin A. germinans appear well‐equipped to thrive in their marginal environment, unless directly impacted by anthropogenic changes. This continued proliferation will result in wide‐reaching community‐level effects (Diskin & Smee, ; Guo et al, ; Kelleway et al, ).…”

“…We can also presume that these three coastlines experienced similar historical distributional fluctuations, as the present-day USA mangrove distribution is thought to be the product of complete eradication at the Last Glacial Maximum, with retraction towards the equator, and subsequent Post-Pleistocene recolonization (Sherrod & McMillan, 1985; also see descriptions in Osland et al, 2018;Rogers & Krauss, 2018;Saintilan, Wilson, Rogers, Rajkaran, & Krauss, 2014).…”

“…Considering ongoing, rapid expansion at all USA range margins (Rogers & Krauss, 2018) and further expansion forecast with climate change (Cavanaugh et al, 2015;, plus the fact that range margins are probably the primary source of recruits beyond distributional limits (Hampe, 2011), USA range-margin A.…”

“…Southern range core mangroves are relatively stable in Florida (but see Ross, Ruiz, Sah, & Hanan, ; Zhang, Thapa, Ross, & Gann, ) and Texas (but see Lonard & Judd, ) compared to highly‐mobile range margins (Cavanaugh et al, ). Periodic extreme freeze events lead to declines in mangrove cover at USA range margins and a cyclical pattern of expansion and contraction over time across the region (Giri & Long, ; Osland, Day, et al, ; Rodriguez, Feller, & Cavanaugh, ; Rogers & Krauss, ). An absence of extreme freezes since the late 1980s is linked to ongoing, rapid range expansion of A. germinans into salt marsh habitat at all USA northern limits, in Texas (Armitage, Highfield, Brody, & Louchouarn, ; Everitt, Yang, Judd, & Summy, ), Louisiana (Osland, Day, et al, ), West Florida (Saintilan et al, ; Stevens, Fox, & Montague, ), and East Florida (Cavanaugh et al, ; Rodriguez et al, ), with further proliferation at, and expansion past, these range margins forecast with climate change (Cavanaugh et al, ; Osland, Day, et al, ; Osland, Enwright, Day, & Doyle, ).…”

Carbon sequestration by Australian tidal marshes

“…Information on sediment accretion rates (mm yr −1 ) were obtained from previously published research using marker horizons25305455. Although useful, comparisons of OC accumulation rates (g C m 2 yr −1 ) could not be statistically analysed in this study due to the use of an Australian tidal marsh mean sediment vertical accretion value (obtained from the literature) used universally in the below equation:…”