Cladium

Abstract: The recent expansion of Typha domingensis (Typha) into areas of the Ev- erglades previously dominated by Cladium jamaicense (Cladium) communities has led to competing hypotheses about the importance of nutrient concentration vs. hydroperiod in controlling the distribution of these species. In this study, experimental mixtures of Typha domingensis, Cladium jamaicense, and Eleocharis interstincta (Eleocharis), a member of the Cladium community, were subjected to two levels of nutrient concentration and three contrasting hydroperiods to determine how these variables might affect Typha's ability to displace the Cladium community. Mixtures of the three species were established in outdoor tanks containing soil from the northern Everglades region where the experiment was con- ducted. Nutrient treatments consisted of nutrient additions to adjust ambient water con- centrations to either 50 ,ug/L phosphorus (P) or 100 pug/L P plus nitrogen (N). The three hydroperiods were achieved by maintaining water depths within ranges observed in the northern Everglades. Maximum water depths of 15, 30, and 60 cm were established through- out the wet season (May-November) followed by lowering to 5 cm during the dry season. Over a 2-yr period, biomass was monitored nondestructively and aboveground material was harvested at the end of the experiment. Analysis of the biomass changes over time showed that differences between the species developed by the end of the first growing season. Typha and Eleocharis had initial growth rates substantially higher than those observed for Cladium. Typha's growth in mixtures responded positively to both elevated nutrients (by as much as 45%) as well as to increased water depth (by as much as 60%), while Cladium and Eleocharis did not increase in response to these variables. Tissue P concentrations were found to be higher for Typha and Eleocharis than for Cladium under nearly all conditions. Net accu- mulation of P in Typha shoots was 2-3 times greater than in the other species. The en- hancement of Typha by elevated nutrients and increased flooding is associated with a syndrome of life history characteristics that includes rapid growth rates, high tissue con- centrations of P, tall leaves, and a greater response to contrasting environmental conditions. Cladium, in contrast, showed a slow growth rate, low tissue concentrations of P, a greater capacity to resist invasion by Typha in shallow waters, and less of a growth response to contrasting environmental conditions, traits that would seem to be well suited to the nutrient- poor, hydrologically unstable conditions natural to the Everglades. Results from this study suggest that attempts to limit the spread of Typha should consider hydrologic restoration as well as reduction in surface water nutrients.

Abstract: The Florida Everglades developed as a nutrient-poor, rain-fed ecosystem. However, for the past 30 yr, the Everglades have received nutrient-enriched surface water runoff from the adjacent Everglades Agricultural Area (EAA). This study examines the response of a pristine wetland, Water Conservation Area 1 (WCA 1), part of the northern Florida Everglades, to nutrient loading as documented by soil nutrient concentrations. During 1979 to 1988, WCA 1 received 138 t total P (TP) and 4919 t total N (TN), retaining 53% of the TP load and 58% of the TN load. Analyses of the spatial distribution of soil N and P showed steep gradients of TP along the western canal boundary, adjacent to inflow points importing EAA runoff. Surficial soils (0-10 cm depth) at interior marsh sites had a mean TP concentration of 368 mg kg -1 , compared with 1028 mg kg -1 measured at sites adjacent to the western canal. Similar trends were observed for soil Ca and Mg, while C and N did not show the same boundary effects on spatial enrichment. Nutrient-enriched sites also had higher porewater soluble reactive P (SRP; 0.15 mg L -1 ) and NH 4 -N (1.65 mg L -1 ) than unenriched sites (SRP = 0.02 mg L -1 , NH 4 -N = 0.85 mg L -1 ). Of the 90 sites sampled, 66 sites consisted of sloughs and sawgrass (Cladium jamaicense Crantz); the remaining 24 sites were either cattail (Typha spp.) dominated or had a significant cattail presence. These 24 cattail sites were closest to the nutrient inflow areas and had the highest soil nutrient concentrations.

Abstract: Biomass and nutrient allocation in sawgrass (Cladium jamaicense Crantz) and cattail (Typha domingensis Pers.) were examined along a nutrient gradient in the Florida Everglades in 1994. This north to south nutrient gradient, created by discharging nutrient-rich agricultural runoff into the northern region of Water Conservatio ea 2A, was represented by three areas (impacted, transitional and reference). Contrasting changes of plant density and size along the gradient were found for communities of both species. For the sawgrass community, more small plants were found in ref ce areas, whereas few large plants were found in impacted areas. In contrast, for the cattail community, bigger plants were found in reference areas, and smaller plants were found in impacted areas. Both species allocated approximately 60% of their total biomass to leaves and 40% to belowground tissues. However, sawgrass biomass allocation to leaves, roots, shoot bases and rhizomes (65%, 19%, 11%, and 5%, respectively) was similar among the three areas. In contrast, cattail plants growing in referen reas showed higher root allocation (27.3%), but lower leaf allocation (51.1%) than those growing in impacted areas (14.6% and 65.8% for root and leaf allocation, respectively). Cattail had higher phosphorus concentrations than sawgrass in tissues associated with growth functions (leaves, roots, and rhizomes). In contrast, sawgrass had higher phosphorus and nitrogen concentrations than cattail in tissues primarily associated with resource storage (shoot bases). From impacted to reference areas, for sawgrass, there was a decrease of leaf TP from 605 to 248 (mg/kg), root TP from 698 to 181 (mg/kg), rhizome TP from 1,139 to 142 (mg/kg), and shoot base TP from 5,412 to 400 to (mg/kg). For cattail, leaf TP decreased from 1,175 to 556 (mg/kg), root TP de sed from 1,100 to 798 (mg/kg), rhizome TP decreased from 1390 to 380 (mg/kg), and shoot base TP decreased from 2,990 to 433 (mg/kg). N/P ratios of sawgrass in reference areas were 27, 63, 38, and 50 for leaves, roots, rhizomes, and shoot bases, respectively, whereas in impacted areas they were 11, 21, 6, and 2, respectively. The greatest TP storage was found in impacted areas. Differences in seed output, seed number, and mean seed weight were found for both species as well. Each cattail flower stalk duced approximately 105 tiny seeds (0.048 ± 0.001 mg) while each sawgrass flower stalk produced about 103 large seeds (3.13 ± 0.005 mg). These results suggest that phosphorus is a limiting resource in the Everglades and that the two species have different life history strategies. These data provide an ecological basis for making informed management and planning decisions to protect and restore the Everglades.