Can differences in phosphorus uptake kinetics explain the distribution of cattail and sawgrass in the Florida Everglades?

<p>Abstract</p> <p>Background</p> <p>Cattail (<it>Typha domingensis</it>) has been spreading in phosphorus (P) enriched areas of the oligotrophic Florida Everglades at the expense of sawgrass (<it>Cladium mariscus </it>spp. <it>jamaicense</it>). Abundant evidence in the literature explains how the opportunistic features of <it>Typha </it>might lead to a complete dominance in P-enriched areas. Less clear is how <it>Typha </it>can grow and acquire P at extremely low P levels, which prevail in the unimpacted areas of the Everglades.</p> <p>Results</p> <p>Apparent P uptake kinetics were measured for intact plants of <it>Cladium </it>and <it>Typha </it>acclimated to low and high P at two levels of oxygen in hydroponic culture. The saturated rate of P uptake was higher in <it>Typha </it>than in <it>Cladium </it>and higher in low-P acclimated plants than in high-P acclimated plants. The affinity for P uptake was two-fold higher in <it>Typha </it>than in <it>Cladium</it>, and two- to three-fold higher for low-P acclimated plants compared to high-P acclimated plants. As <it>Cladium </it>had a greater proportion of its biomass allocated to roots, the overall uptake capacity of the two species at high P did not differ. At low P availability, <it>Typha </it>increased biomass allocation to roots more than <it>Cladium</it>. Both species also adjusted their P uptake kinetics, but <it>Typha </it>more so than <it>Cladium</it>. The adjustment of the P uptake system and increased biomass allocation to roots resulted in a five-fold higher uptake per plant for <it>Cladium </it>and a ten-fold higher uptake for <it>Typha</it>.</p> <p>Conclusions</p> <p>Both <it>Cladium </it>and <it>Typha </it>adjust P uptake kinetics in relation to plant demand when P availability is high. When P concentrations are low, however, <it>Typha </it>adjusts P uptake kinetics and also increases allocation to roots more so than <it>Cladium</it>, thereby improving both efficiency and capacity of P uptake. <it>Cladium </it>has less need to adjust P uptake kinetics because it is already efficient at acquiring P from peat soils (e.g., through secretion of phosphatases, symbiosis with arbuscular mycorrhizal fungi, nutrient conservation growth traits). Thus, although <it>Cladium </it>and <it>Typha </it>have qualitatively similar strategies to improve P-uptake efficiency and capacity under low P-conditions, <it>Typha </it>shows a quantitatively greater response, possibly due to a lesser expression of these mechanisms than <it>Cladium</it>. This difference between the two species helps to explain why an opportunistic species such as <it>Typha </it>is able to grow side by side with <it>Cladium </it>in the P-deficient Everglades.</p

Supporting Spartina: Interdisciplinary perspective shows Spartina as a distinct solid genus

In 2014 a DNA-based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 years. We do not agree with the arguments underlying the proposal to change Spartina to Sporobolus. We understand the importance of taxonomy and of formalized nomenclature and hope that by opening this debate we will encourage positive feedback that will strengthen taxonomic decisions with an interdisciplinary perspective. We consider the strongly distinct, monophyletic clade Spartina should simply and efficiently be treated as the genus Spartina

Development of Bioremediation for Oil Spill Cleanup in Coastal Wetlands

A report describing the effectiveness of bioremediation as an oil spill cleanup technique in wetlands

Relationship Between Anatomical and Metabolic Responses to Soil Waterlogging in the Coastal Grass Spartina patens

Flooding responses in Spartina patens propagated from plants collected in dune, swale, and marsh habitats were examined in a 63 d time-course experiment. Leaf growth rates and anatomical and metabolic responses did not depend upon plant population, suggesting that there were no physiologically significant differences in soil waterlogging responses among source populations. Flooding resulted in significant declines in soil redox potential and root specific gravity (indicating increased root aeration). Root alcohol dehydrogenase activity (ADH, a measure of the capacity to ferment ethanol) increased within 3 d of flooding, then exhibited a significant decline as root aeration increased (i.e. as root specific gravity decreased). However, maximal aerenchyma development (50% of the root volume after 29 d) reduced but did not eliminate hypoxic stress in the roots. When plants that were flooded for 63 d were drained, ADH activity fell to levels equivalent to drained controls. These results support the following inferences: (1) Soil waterlogging dramatically increases root ADH activity. (2) Impact of soil waterlogging on root metabolism diminishes once internal root aeration increases. (3) Under severe chemically-reducing soil conditions, root aerenchyma formation, which adjusts to the prevalent degree of soil waterlogging, cannot provide roots with sufficient oxygen to support aerobic respiration completely

The Relationship of Soil Parameters and Root Metabolism to Primary Production in Periodically Inundated Soils

Hydrology is the dominant forcing function in wetland ecosystems (Gosselink and Turner 1978). Through its direct effect on soil waterlogging, the dynamic hydrologic environment controls soil physicochemical status, sedimentation rates, salinity, nutrient cycling, decomposition, and faunal and microfloral activities. Thus soil waterlogging controls the interaction of soil and root processes which, in turn, influence growth (Figure 34.1). Although wetland vegetation is highly productive, the roots of these plants often experience severely reduced soil conditions, lack of oxygen, and toxic compounds as a result of soil waterlogging. This chapter emphasizes the linkage between growth responses and waterlogging-induced changes in root processes of wetland vegetation. While not exhaustive, the examples in Tables 34.1-34.5 illustrate the major soil-root interactions which influence growth. In addition, we present a case study describing how hydrologically induced changes in soil parameters affect root processes and ultimately growth and productivity of Spartina alterniflora the dominant intertidal salt marsh angiosperm of the Atlantic and Gulf Coasts of the United States

Waterlogging responses in dune, swale and marsh populations of Spartina patens under field conditions

Soil waterlogging responses were examined in three Spartina patens populations along a steep flooding gradient in coastal Louisiana. Root anatomy and physiological indicators of anaerobic metabolism were examined to identify and compare flooding responses in dune, swale and marsh populations, while soil physicochemical factors were measured to characterize the three habitats. Soil waterlogging increased along the gradient from dune to marsh habitats and was accompanied by increases in root porosity (aerenchyma). Aerenchyma in marsh roots was apparently insufficient to provide enough oxygen for aerobic respiratory demand, as indicated by high root alcohol dehydrogenase activities and low energy charge ratios. Patterns of root metabolic indicators suggest that dune and swale roots generally respired aerobically, while anaerobic metabolism was important in marsh roots. However, in each population, relatively greater soil waterloging was accompanied by differences in enzyme activities leading to malate accumulation. In dune and swale roots under these circumstances, depressed adenylate energy charge ratios may have been the result of an absence of increased ethanol fermentation. These trends suggest that: 1) Aerenchyma formation was an important, albeit incomplete, long-term adaptation to the prevalent degree of soil waterlogging. 2) All populations adjusted root metabolism in response to a relative (short-term) increase in soil waterlogging

Coastal Wetland Belowground Biomass

These data were collected in the field in 2008 from a Sagittaria lancifolia L. dominated, oligohaline marsh located along the west bank of the Tchefuncte River, approximately 1 km north of Lake Pontchartrain, LA, USA (30° 23.205’N, 90° 09.551’ W). Two methods were used to estimate belowground biomass: the ingrowth method and the standing crop method. Abbreviated headings are as follows: "Block" = statistical block; "N" = nitrogen enrichment treatment (kg/ha/yr); "P" = phosphorus enrichment treatment (kg/ha/yr); "LRoot IG" = live root biomass in ingrowth cores (g/m2); "LRhiz IG" = live rhizome biomass in ingrowth cores (g/m2); "Live IG" = live root+rhizome biomass in ingrowth cores (g/m2); "Dead IG" = dead root+rhizome biomass in ingrowth cores (g/m2); "Total IG" = total live+dead biomass in ingrowth cores (g/m2); "LRoot SC" = live root biomass in standing crop cores (g/m2); "LRhiz SC" = live rhizome biomass in standing crop cores (g/m2); "Live SC" = live root+rhizome biomass in standing crop cores (g/m2); "Dead SC" = dead root+rhizome biomass in standing crop cores (g/m2); "Total SC" = total live+dead biomass in standing crop cores (g/m2)

Effect of long-term flooding on root metabolic response in five freshwater marsh plant species

Five freshwater marsh plant species exhibited different root metabolic responses when flooded to three water depths in field macrocosms. The capacity for alcoholic fermentation (as indicated by alcohol dehydrogenase activity) increased and remained at a relatively high level in the roots of the least flood-tolerant species, Scolochloa festucacea, but was not stimulated significantly or only temporarily in the more tolerant species, Scirpus acutus, Scirpus validus, Typha glauca, and Phragmites australis. During the first month of flooding, alcohol dehydrogenase activity showed a positive relationship with flooding depth and a negative relationship with soil redox potential. Malate accumulated in the roots of S. acutus, S. validus, and to a lesser extent in P. australis in response to flooding; concentrations showed a significant positive relationship with water depth and a significant negative relationship with soil redox potential during the first month of flooding. Differences in root metabolism among the five species were still evident after 1 year of continual flooding. Root specific gravities and air space cross-sectional volumes demonstrated potential species differences in root resistance to oxygen movement and root oxygen volume, respectively. The results suggest that the observed metabolic response reflected differential aeration of the roots resulting from differences in root structure and soil oxygen demand (reducing power)