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Saltmarsh boundary modulates dispersal of mangrove propagules: implications for mangrove migration with sea-level rise.

Peterson JM, Bell SS - PLoS ONE (2015)

Bottom Line: Here, using an experimental approach, we record landward and seaward dispersal and subsequent establishment of mangrove propagules that encounter biotic boundaries composed of two types of saltmarsh taxa: succulents and grasses.However, propagules moved seaward less frequently and over shorter distances upon encountering boundaries composed of saltmarsh grasses versus succulents.We uniquely confirmed that the small subset of propagules dispersing landward displayed proportionately higher establishment success than those transported seaward.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Few studies have empirically examined the suite of mechanisms that underlie the distributional shifts displayed by organisms in response to changing climatic condition. Mangrove forests are expected to move inland as sea-level rises, encroaching on saltmarsh plants inhabiting higher elevations. Mangrove propagules are transported by tidal waters and propagule dispersal is likely modified upon encountering the mangrove-saltmarsh ecotone, the implications of which are poorly known. Here, using an experimental approach, we record landward and seaward dispersal and subsequent establishment of mangrove propagules that encounter biotic boundaries composed of two types of saltmarsh taxa: succulents and grasses. Our findings revealed that propagules emplaced within saltmarsh vegetation immediately landward of the extant mangrove fringe boundary frequently dispersed in the seaward direction. However, propagules moved seaward less frequently and over shorter distances upon encountering boundaries composed of saltmarsh grasses versus succulents. We uniquely confirmed that the small subset of propagules dispersing landward displayed proportionately higher establishment success than those transported seaward. Although impacts of ecotones on plant dispersal have rarely been investigated in situ, our experimental results indicate that the interplay between tidal transport and physical attributes of saltmarsh vegetation influence boundary permeability to propagules, thereby directing the initial phase of shifting mangrove distributions. The incorporation of tidal inundation information and detailed data on landscape features, such as the structure of saltmarsh vegetation at mangrove boundaries, should improve the accuracy of models that are being developed to forecast mangrove distributional shifts in response to sea-level rise.

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Distance moved by A. germinans propagules that dispersed seaward.Mean distance ± se (cm) seaward of initial position at which A. germinans propagules were recovered for saltmarsh grass monoculture (SV) or succulent-grass ecotone (SUC) treatments on three dates. Different letters above bars represent significantly different distances (RMANOVA).
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pone.0119128.g003: Distance moved by A. germinans propagules that dispersed seaward.Mean distance ± se (cm) seaward of initial position at which A. germinans propagules were recovered for saltmarsh grass monoculture (SV) or succulent-grass ecotone (SUC) treatments on three dates. Different letters above bars represent significantly different distances (RMANOVA).

Mentions: Propagules from each of the 10 experimental plots in the two saltmarsh treatments dispersed both seaward and landward of their starting position (Fig. 2). But, across all plots, propagules most frequently dispersed in the seaward direction. Furthermore, the mean distance moved seaward was significantly greater for propagules initially emplaced into succulent-grass plots compared to those from grass monoculture plots (RMANOVA, F1,8 = 11.118, p = 0.01, Fig. 3). On the first day after emplacement, propagules originating from the succulent-grass plots and which subsequently moved seaward were recovered 34.8 (±3.4) cm [mean (± se)] away from the starting position. In contrast, propagules moving seaward and originating from grass monoculture plots were recovered 16.5 (±2.8) [mean (± se)] cm from their initial position.


Saltmarsh boundary modulates dispersal of mangrove propagules: implications for mangrove migration with sea-level rise.

Peterson JM, Bell SS - PLoS ONE (2015)

Distance moved by A. germinans propagules that dispersed seaward.Mean distance ± se (cm) seaward of initial position at which A. germinans propagules were recovered for saltmarsh grass monoculture (SV) or succulent-grass ecotone (SUC) treatments on three dates. Different letters above bars represent significantly different distances (RMANOVA).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356570&req=5

pone.0119128.g003: Distance moved by A. germinans propagules that dispersed seaward.Mean distance ± se (cm) seaward of initial position at which A. germinans propagules were recovered for saltmarsh grass monoculture (SV) or succulent-grass ecotone (SUC) treatments on three dates. Different letters above bars represent significantly different distances (RMANOVA).
Mentions: Propagules from each of the 10 experimental plots in the two saltmarsh treatments dispersed both seaward and landward of their starting position (Fig. 2). But, across all plots, propagules most frequently dispersed in the seaward direction. Furthermore, the mean distance moved seaward was significantly greater for propagules initially emplaced into succulent-grass plots compared to those from grass monoculture plots (RMANOVA, F1,8 = 11.118, p = 0.01, Fig. 3). On the first day after emplacement, propagules originating from the succulent-grass plots and which subsequently moved seaward were recovered 34.8 (±3.4) cm [mean (± se)] away from the starting position. In contrast, propagules moving seaward and originating from grass monoculture plots were recovered 16.5 (±2.8) [mean (± se)] cm from their initial position.

Bottom Line: Here, using an experimental approach, we record landward and seaward dispersal and subsequent establishment of mangrove propagules that encounter biotic boundaries composed of two types of saltmarsh taxa: succulents and grasses.However, propagules moved seaward less frequently and over shorter distances upon encountering boundaries composed of saltmarsh grasses versus succulents.We uniquely confirmed that the small subset of propagules dispersing landward displayed proportionately higher establishment success than those transported seaward.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Few studies have empirically examined the suite of mechanisms that underlie the distributional shifts displayed by organisms in response to changing climatic condition. Mangrove forests are expected to move inland as sea-level rises, encroaching on saltmarsh plants inhabiting higher elevations. Mangrove propagules are transported by tidal waters and propagule dispersal is likely modified upon encountering the mangrove-saltmarsh ecotone, the implications of which are poorly known. Here, using an experimental approach, we record landward and seaward dispersal and subsequent establishment of mangrove propagules that encounter biotic boundaries composed of two types of saltmarsh taxa: succulents and grasses. Our findings revealed that propagules emplaced within saltmarsh vegetation immediately landward of the extant mangrove fringe boundary frequently dispersed in the seaward direction. However, propagules moved seaward less frequently and over shorter distances upon encountering boundaries composed of saltmarsh grasses versus succulents. We uniquely confirmed that the small subset of propagules dispersing landward displayed proportionately higher establishment success than those transported seaward. Although impacts of ecotones on plant dispersal have rarely been investigated in situ, our experimental results indicate that the interplay between tidal transport and physical attributes of saltmarsh vegetation influence boundary permeability to propagules, thereby directing the initial phase of shifting mangrove distributions. The incorporation of tidal inundation information and detailed data on landscape features, such as the structure of saltmarsh vegetation at mangrove boundaries, should improve the accuracy of models that are being developed to forecast mangrove distributional shifts in response to sea-level rise.

Show MeSH
Related in: MedlinePlus