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46 records · Page 3Linked to original sources
USGS1998

Factors influencing cattail abundance in the northern Everglades

Since the early 1900s, the Everglades have been influenced by anthropogenic actions including altered hydrology and increased nutrient loading. In the northern Everglades an apparent effect of these disturbances has been the development and proliferation of dense cattail ( Typha spp. ) stands in areas previously dominated by sawgrass ( Cladium jamaicense Crantz) and sloughs. Cattail cover, soil nutrient concentrations, topography and fire history were determined for the Holey Land and Rotenberger Wildlife Management Areas, located in the northern Everglades. These data were analyzed using multiple regression to assess the relative influence of fire, hydrology and soil nutrients on cattail abundance. Holey Land and Rotenberger were overdrained over recent decades which resulted in soil compaction and nutrient accumulation, illustrated by increased soil bulk densities and elevated nutrient storage. Average bulk densities were 0.13 g cm −3 for Holey Land and 0.22 g cm −3 for Rotenberger. Average total P (TP) stored in the surface 10 cm of soil in Holey Land and Rotenberger were 7 and 13 g m −2 , respectively. In contrast, Everglades soils uninfluenced by nutrient enrichment and with less severe overdrainage have bulk densities of 0.07 g cm −3 and TP storage of 4 g m −2 . Typically, elevated soil P concentrations have been considered a primary factor influencing cattail growth and distribution in the Everglades. With the apparent absence of P limitation in Holey Land and Rotenberger, cattail abundance was influenced by either fire or hydrology. Forty-six percent of the variation of cattail cover in Holey Land was explained by elevation, indicating that increased water depth and duration of flooding have a significant impact on cattail expansion. In Rotenberger, fire was the most influential factor, explaining 57% of the variation in cattail cover. Hydrology was the second most important factor limiting cattail abundance.

Florida↗
USGS1998

Long-term dynamics of Typha populations

The zonation of Typha populations in an experimental pond in Michigan was re-examined 15 years after the original sampling to gain insight into the long-term dynamics. Current distributions of Typha populations were also examined in additional experimental ponds at the site that have been maintained for 23 years. The zonation between T. latifolia and T. angustifolia in the previously studied pond 15 years after the initial sampling revealed that the density and distribution of shoots had not changed significantly. Thus, it appears that previously reported results (based on 7- year old populations) have remained consistent over time. Additional insight into the interaction between these two taxa was sought by comparing mixed and monoculture stands in five experimental ponds that have remained undisturbed for their 23-year history. The maximum depth of T. latifolia, the shallow- water species, was not significantly reduced when growing in the presence of the more flood tolerant T. angustifolia. In contrast, the minimum depth of T. angustifolia was reduced from 0 to 37 cm when in the presence of T. latifolia. When total populations were compared between monoculture and mixed stands, the average density of T. angustifolia shoots was 59.4 percent lower in mixed stands while the density of T. latifolia was 32 percent lower, with T. angustifolia most affected at shallow depths (reduced by 92 percent) and T. latifolia most affected at the deepest depths (reduced by 60 percent). These long-term observations indicate that competitive displacement between Typha taxa has remained stable over time.

Aquatic Botany↗
USGS1998

Response of shoal grass, Halodule wrightii, to extreme winter conditions in the Lower Laguna Madre, Texas

Effects of a severe freeze on the shoal grass, Halodule wrightii, were documented through analysis of temporal and spatial trends in below-ground biomass. The coincidence of the second lowest temperature (-10.6??C) in 107 years of record, 56 consecutive hours below freezing, high winds and extremely low water levels exposed the Laguna Madre, TX, to the most severe cold stress in over a century. H. wrightii tolerated this extreme freeze event. Annual pre- and post-freeze surveys indicated that below-ground biomass estimated from volume was Unaffected by the freeze event. Nor was there any post-freeze change in biomass among intertidal sites directly exposed to freezing air temperatures relative to subtidal sites which remained submerged during the freezing period.

Aquatic Botany↗
USGS1999

The effects of global climate change on seagrasses

The increasing rate of global climate change seen in this century, and predicted to accelerate into the next, will significantly impact the Earth's oceans. In this review, we examine previously published seagrass research through a lens of global climate change in order to consider the potential effects on the world's seagrasses. A primary effect of increased global temperature on seagrasses will be the alteration of growth rates and other physiological functions of the plants themselves. The distribution of seagrasses will shift as a result of increased temperature stress and changes in the patterns of sexual reproduction. Indirect temperature effects may include plant community changes as a result of increased eutrophication and changes in the frequency and intensity of extreme weather events. The direct effects of sea level rise on the coastal oceans will be to increase water depths, change tidal variation (both mean tide level and tidal prism), alter water movement, and increase seawater intrusion into estuaries and rivers. A major impact of all these changes on seagrasses and tidal freshwater plants will be a redistribution of existing habitats. The intrusion of ocean water into formerly fresh or brackish water areas will directly affect estuarine plant distribution by changing conditions at specific locations, causing some plants to relocate in order to stay within their tolerance zones and allowing others to expand their distribution inland. Distribution changes will result from the effects of salinity change on seed germination, propagule formation, photosynthesis, growth and biomass. Also, some plant communities may decline or be eliminated as a result of increased disease activity under more highly saline conditions. Increased water depth, which reduces the amount of light reaching existing seagrass beds, will directly reduce plant productivity where plants are light limited. Likewise, increases in water motion and tidal circulation will decrease the amount of light reaching the plants by increasing turbidity or by stimulating the growth of epiphytes. Increasing atmospheric carbon dioxide will directly elevate the amount of CO 2 in coastal waters. In areas where seagrasses are carbon limited, this may increase primary production, although whether this increase will be sustained with long-term CO 2 enrichment is uncertain. The impact of increases in CO 2 will vary with species and environmental circumstances, but will likely include species distribution by altering the competition between seagrass species as well as between seagrass and algal populations. The reaction of seagrasses to UV-B radiation may range from inhibition of photosynthetic activity, as seen for terrestrial plants and marine algae, to the increased metabolic cost of producing UV-B blocking compounds within plant tissue. The effects of UV-B radiation will likely be greatest in the tropics and in southern oceans. There is every reason to believe that, as with the predicted terrestrial effects of global climate change, impacts to seagrasses will be great. The changes that will occur in seagrass communities are difficult to predict; our assessment clearly points out the need for research directed toward the impact of global climate change on seagrasses.

Aquatic Botany↗
USGS2000

Seed germination of two Everglades species, Cladium jamaicense and Typha domingensis

The germination requirements of Cladium jamaicense Crantz and Typha domingensis Pers. were studied under controlled conditions in the laboratory. Treatments included six temperature regimes, (constant temperatures of 15 20, 25, 30°C, and two fluctuating day : night temperature regimes of 25 : 10°C and 30 : 20°C), two light levels (14 : 10 h light : dark photoperiod and 24 h dark environment), two substrates (peat and water) and two O 2 levels (atmospheric and low (4.34%) O 2 concentration) using a complete randomized block design. The average incubation period needed for seeds to germinate was shorter for T. domingensis (1.1–19.5 days) than for C. jamaicense (26–46 days) and the final germination percentage was higher for T. domingensis than for C. jamaicense (85 vs. 42 %). Cladium jamaicense only germinated with fluctuating temperatures whereas T. domingensis germinated at all temperature regimes. Light was required for T. domingensis seeds to germinate, whereas C. jamaicense could germinate at a reduced rate in the dark. Peat substrate had a positive effect on germination in both species. Peat substrate shortened the incubation period for seeds of both species, enhanced germination of T. domingensis , especially at low temperatures, and enhanced germination of C. jamaicense in the dark. Low oxygen availability did not influence the germination of C. jamaicense but enhanced germination of T. domingensis at low temperatures. Although the two species differ significantly in their germination requirements and responses to specific environmental conditions, germination of both these species was enhanced by environmental conditions typical of exposed water saturated mudflats or sediment surfaces. Typha domingensis produces a large number of small seeds, which do not germinate when covered by sediment. In contrast, C. jamaicense produces fewer and larger seeds, with resources able to support growth through a thin layer of sediment or detritus.

Florida↗
USGS2002

The flora of Oktibbeha County, Mississippi

We surveyed the flora of Oktibbeha County, Mississippi, U.S.A., from February 1994 to 1996. Occupying 118 square kilometers in east-central Mississippi, Oktibbeha County lies among 3 physiographic regions that include, from west to east, Interior Flatwoods, Pontotoc Ridge, and Black Prairie. Accordingly, the county harbors a diverse flora. Based on field work, as well as an extensive review of published literature and herbarium records at IBE and MISSA, we recorded a total of 1,148 taxa (1,125 species, 7 hybrids, 16 infraspecific taxa) belonging to 514 genera in 160 families, over 85% of all taxa documented were native. Compared to 3 other counties in east-central Mississippi, Oktibbeha County has the second largest recorded flora. The number of state-listed (endangered, threatened, or of special concern) taxa (67) documented in this survey far exceeds that reported from any other county in the region. Three introduced species, Ilex cornuta Lindl. & Paxton, Mahonia bealei (Fortune) Carrie??re, and Nandina domestica Thunb., are reported in a naturalized state for the first time from Mississippi. We also describe 16 different plant communities belonging to 5 broad habitat categories: bottomland forests, upland forests and prairies, aquatic habitats, seepage areas, and human-influenced habitats. A detailed description of the vegetation associated with each of these communities is provided.

SIDA, Contributions to Botany↗
USGS1989

The geology, botany and chemistry of selected peat-forming environments from temperate and tropical latitudes

Peat has been studied in several geologic settings: (1) glaciated terrain in cold temperate Maine and Minnesota, U.S.A.; (2) an island in the Atlantic Ocean off the coast of Maine, where sea level is rising; (3) the warm temperate U.S. Atlantic and Gulf Coastal Plains, where sea level has changed often; and (4) the tropical coast of Sarawak, Malaysia, and the tropical delta of the Batang Hari River, Sumatra, Indonesia. Most of these deposits are domed (ombrotrophic or partly ombrotrophic) bogs in which peat accumulation continued above the surface of the surrounding soil. However, the bogs of the U.S. Atlantic and Gulf Coastal Plains are comparatively not as domed, and many have almost level surfaces. In some bogs, aquatic or semi-aquatic plant materials accumulated, replaced water in the depressions, and formed a surface on which marsh or swamp vegetation could subsequently live, die, and accumulate. In others, the plant materials accumulated initially on level silt or sand surfaces supporting marshes or swamps. As the peat dome formed, plants growing on it changed from luxuriant ones near the base of the dome, where nutrients were brought into the bog by surface and ground water, to stunted ones at the top of the dome, where the raised bogs are fed by nutrient-poor precipitation. The physical and chemical changes that take place in the sequence of environments from the pond stage of deposit development, through the grassy marsh stage, through the forested swamp stage, and finally through the heath dome stage can be measured in terms of acidity and ash, volatile matter, carbon, hydrogen, nitrogen, sulfur and oxygen contents, as well as in the kind and distribution of trace elements. The organic and inorganic contents of the deposits relate to geomorphology, and geomorphology relates to their settings. As models of coal formation, some domed peat deposits may help in solving problems of distribution and character of ancient coal beds. But clearly not all peat deposits are precursors of coal. Most Holocene peat deposits are subject to destruction by erosion, fire and decomposition through microbial and chemical oxidation before burial. The best environments for coal precursors have biomass accumulation, a continuously rising water table within the mass, and minimum influx of clay and silt until preservation by burial. The most suitable settings for future economic coal deposits are domed bogs that accumulate thick, widespread peat having low ash and low sulfur contents. The ombrotrophic peat deposits of tropical Sarawak and Sumatra are thick and extensive, contain low-ash and low-sulfur peat, and have high heating values. They are considered to be the best tropical coal analogs because of their extent and chances of preservation; the base of the peat is below adjacent river levels, and chemical and structural conditions are favorable for accumulation.

International Journal of Coal Geology↗
USGS1988

Seasonal growth of the exotic submersed macrophyte Nitellopsis obtusa in the Detroit River of the Great Lakes

Seasonal growth and occurrence of an exotic submersed aquatic macrophyte, Nitellopsis obtusa , was monitored at the head of the Detroit River of the Great Lakes from June 1984 to April 1985. Nitellopsis obtusa first appeared in early July, increased in biomass from July to September, remained at relatively high biomass from September to late January, and decreased substantially as ice breakup began in mid-February. By March it had become senescent, lacking chlorophyll and disintegrating easily. Nitellopsis obtusa was therefore available as a source of food and shelter for benthic and juvenile fish populations in late fall and winter, when other macrophytes were absent.

Canadian Journal of Botany↗
USGS1985

Growth of submersed macrophyte communities in the St. Clair - Detroit River system between Lake Huron and Lake Erie

Growth of submersed aquatic macrophytes was determined from observation and on the basis of biomass of samples collected from April to November 1978 at seven study sites in a major river system of the Great Lakes, the St. Clair – Detroit river system between Lake Huron and Lake Erie. Growth usually began between April and June, peaked between July and October, and decreased by late November. Maximum biomass at six of the seven sites (118–427 g dry weight m −2 ) was similar or greater than that reported in other rivers at similar latitudes. Seasonal growth of the abundant taxa followed one of three seasonal patterns at each study site: one dominant taxon grew alone; codominant taxa grew sympatrically without species succession; and codominant taxa grew sympatrically with species succession. Differences in growth and seasonal succession of some taxa were apparently caused by the presence or absence of overwintering plant material, competition, and life-cycle differences.

Canadian Journal of Botany↗