Wetland Productivity Research Articles

Effect of forest management practices on southern forested wetland productivity

In the interest of increasing productivity of forested wetlands for timber production and/or wildlife value, management schemes that deal mainly with water-level control have been developed. The three forest types in the southeastern U.S. most commonly affected are cypress/tupelo forests, bottomland hardwood forests, and wet pine sites (including pocosins). In forested wetlands, hydrology is the most important factor influencing productivity. In bottomland and cypress/tupelo forests, water-level control can have mixed results. Alterations in natural hydrologic patterns leading to increased flooding or drainage can cause decreased growth rates or even death of the forest. Bottomland hardwoods respond favorably in the short term to water-level management, but the long-term response is currently under study. In wet pine sites, timber volume can be increased significantly by water-level management, but the impact upon other ecological functions is less understood. It is difficult to adequately describe productivity relations in wetland forests because of the great diversity in habitat types and the lack of data on how structure and function might be affected by forestry operations. There is a definite need for more long-term, regional studies involving multidisciplinary efforts.

Production and emission of methane in a brackish and a freshwater wetland

There is no clear consensus on how environmental and biotic factors control microbiallymediated methane production in wetlands, as well as emission of this important ‘greenhouse gas’ from wetlands into the atmosphere. To provide insight, I studied rates of methane production and emission into the atmosphere, as well as factors controlling those rates, along a toposequence from non-flooded to seasonally flooded in a coastal meadow and in a fen in Denmark. Methane production was estimated from anaerobic soil slurries while emission was estimated from static flux chambers. Methane emission into the atmosphere averaged 0.04 μg C-CH 4 dm −2 h- −1 in the coastal meadow and 1.9 μg C-CH 4 dm −2 h −1 in the fen. A comparison of potential CH 4 production and CH 4 emission into the atmosphere showed that in the coastal meadow, but not in the fen, emission increased when production increased during summer. Relationships between potential CN 4 production and soil water content as well as soil temperature are discussed. Arrhenius plots indicated strikingly similar temperature responses of CH 4 production in the two wetlands. Also, both wetlands showed different temperature responses in saturated soils ( Q 10 = 3.1 and 3.6; E h=79 and 84 kJ mol −1) compared to unsaturated soils ( Q 10 = 8.1 and 8.7; e h = 138 and 142 kJ mol −1). My results suggest that different types of methanogens inhabit saturated and unsaturated soils in both a coastal meadow and a fen. Overall, the study indicates that CH 4 production in wetlands and CH 4 emission into the atmosphere from wetlands are controlled by a complex set of environmental and biotic factors which differ between wetlands.

Aquatic invertebrate production in southeastern USA wetlands during winter and spring

We measured aquatic invertebrate abundance, standing stock biomass, and community production in three types of wetlands on Noxubee National Wildlife Refuge from December 1987 through April 1988. Together,Orthocyclops modestus andDaphnia pulex were the most abundant organisms collected in all habitats during both winter and spring, but each contributed little to total standing stock biomass or production.Caecidotea communis andPristina osborni made up ≥47% of the total standing stock biomass at each site during both winter (December–February) and spring (March–May).Crangonyx gracilis, Chironomus spp.,Chaoborus punctipennis, andEclipidrilus spp. each contributed ≥5% of the total biomass at one or more wetland habitats. Estimates of aquatic invertebrate community production ranged from 930 to 1,578 mg dry weight/m2 among wetland types during winter and from 3,306 to 5,421 mg dry weight/m2 among wetland types during spring.Caecidotea communis andPristina osborni contributed most to community production during both seasons, but particularly in beaver ponds during spring. Other taxa made up substantial portions of the community production in one or two wetland habitats.

Primary production control of methane emission from wetlands

WETLANDS, both natural and agricultural, contribute an estimated 40 to 50% of the total methane emitted to the atmosphere each year. Recent efforts in atmospheric modelling1 and attempts to constrain CH4 source strengths2 have indicated the need to delineate the processes responsible for the large variations in emission rates found within and across wetland types. Numerous biogeochemical factors are known to affect the activity of methanogenic bacteria3,4 and although there has been some success in relating water level5–7 and temperature8,9 to CH4 emissions within particular systems, these variables are insufficient for predicting emissions across a variety of wetlands2,10. From simultaneous measurements of CO2 and CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, we report here a positive correlation between CH4 emission and net ecosystem production and suggest that net ecosystem production is a master variable, integrating many factors which control CH4 emission in vegetated wetlands. We find that about 3 per cent of the daily net ecosystem production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial activity in wetlands associated with elevated atmospheric CO2 concentrations11, we envisage the potential for increasing CH4 emissions from inundated wetlands, further enhancing the greenhouse effect.

The relationship between variable hydroperiod, production allocation, and belowground organic turnover in forested wetlands

Belowground processes in forested wetland ecosystems are exceptionally important, yet most attention seems to focus on surface flooding regimes and other aboveground features of these systems. Field studies in the Dismal Swamp and several manipulative experiments examined belowground dynamics in relation to a flood intensity gradient. Generally, more extensive flooding results in less production allocation belowground. Erroneous conclusions regarding wetland production are reached if aboveground parameters alone are considered. Root decomposition rates are slowest where the duration of soil saturation is the longest. Organic accumulation rates in wetlands are determined by the amount of production of particular biomass types (eg., leaves vs. roots) and the rate at which they decompose. Biomass allocation patterns seem to change in response to a flooding gradient. This represents a major implication for wetland ecosystem functions, as carbon allocation patterns determine the array of litter types that affect decomposition rates and thus nutrient availability. The hydroperiod data from the Dismal Swamp demonstrate the highly variable nature of flooding in forested wetlands, especially during the growing season. The data suggest that it is unwise to rely on hydroperiod as a direct criterion for identifying a jurisdictional wetland.

Geographical patterns of persistence in duck guilds.

Geographical gradients of persistence in community structure have been suggested to be causally related to underlying gradients of species diversity, environmental variability and/or productivity. In order to test whether the persistence of breeding duck communities was dependent on any one of these three factors, thirty-three years of census data from the Canadian prairie and boreal forest regions was examined along geographical gradients of wetland habitat variability and productivity. For breeding ducks, locally derived patterns of persistence were generally independent of local habitat conditions. Persistence appeared to be related more to patterns of emigration and immigration in response to climatic conditions (i.e., drought) in the southern prairies than to local species richness, wetland habitat variability or productivity. It is suggested, therefore, that analyses of community persistence derived at small spatial scales may be of limited value if the structure of communities is not regulated by local conditions.

Restoring Coastal Wetlands: The Californian Experience

ABSTRACTCoastal wetlands are an important natural resource, providing habitat for fish and wildlife, particularly many rare or endangered species. These wetlands also serve important functions for the treatment of urban runoff and effluent discharges, the dissipation of wave energy, and shore protection. The US Fish and Wildlife Service estimates that approximately 45 000 km2 of US wetlands have been destroyed in the past two centuries.The importance of wetlands in the ecosystem has only begun to be understood during the past two decades, and there has been a major legislative effort to preserve, protect, and enhance existing coastal wetlands. The productivity of tidal wetlands is related directly to the hydrologic characteristics of the system, and some considerations for the hydrologic design for the enhancement or construction of tidal wetlands are outlined. Recent attention has focused on the use of dredged spoil materials from harbours or shippping channels to restore historic tidal wetlands. The hydrologic design criteria are illustrated through a series of case studies in California.

Water Level Variability and Litterfall Productivity of Forested Freshwater Wetlands in Louisiana

-Litterfall was measured in an impounded swamp and a managed wooded crayfish pond swamp in S central Louisiana from mid-December 1976 through mid-December 1981 and in a natural swamp and a restored swamp from mid-December 1977 through mid-December 1981. Hydrological patterns were different from area to area and water depths (measured from May 1977 to May 1981) varied considerably in three of the areas depending upon rainfall. In the crayfish pond, the water regime was maintained by pumping. Average leaf litterfall was greatest in the crayfish pond swamp (579 g/m2/yr) and least (293 g/m2/yr) in the impounded area. Average litterfall values were intermediate and similar in the natural swamp and the restored swamp areas (405 and 401 g/m2/yr, respectively). Yearly litterfall declined throughout the study in the impounded swamp until 1981. The progressive decline is likely related to permanent flooding conditions which have caused tree mortality. The increase in litterfall in 1981 in all areas was probably related to drought conditions that year which for the first time in many years allowed the sites to dry out, thus improving growing conditions. These results suggest that productivity of Louisiana coastal forested wetlands will decrease in the future due to waterlogging related to regional subsidence.

Wetland Production and Smallholder Persistence: Agricultural Change in a Highland Peruvian Region

Abstract This study integrates regional political ecology concepts via the ideas of structuration, a politics of place, and production ecology in order to examine the ecological and social relations embodied in wetland agriculture. Montane bogs were converted into fields roughly twenty years ago when peasant cultivators in Colquepata District (southern Peru) responded to a convergence of production and demand incentives. Environmental conditions, regional social and economic structures, and government policy most shaped the temporal and spatial realization of these stimuli. Both the expansion of local commerce and the capture of state agricultural subsidies depended on social relations that formed historically through ethnic and peasant resistance against landlord domination in a “region of resistance.” Flexible labor allocation required by the biological ecology of wetland fields has contributed to the persistence of production by peasant smallholders. The social practices and struggles of dominated peas...

Nutrient status of wetlands in the Interlake Region of Manitoba, Canada

Preliminary observations indicated that the productivity of wetlands in the Interlake region of Manitoba, Canada is low, resulting in limited use by waterfowl and other wildlife species. This study compared nutrient availability, algal biomass, and invertebrate abundance and biomass between two Interlake wetlands. The Narcisse site was a typical Interlake wetland with no known source of external nutrient input. The Cruise Marsh site was a wetland similar to the Narcisse site except for the operation of a cattle feedlot on its shore. Total dissolved and suspended N and P levels were higher at the Cruise Marsh site throughout much of the year. Phytoplankton and epiphytic periphyton biomass were also much higher at Cruise Marsh. The water chemistry and biomass of these two algae groups found in the Narcisse site were similar to levels characteristic of oligotrophic lakes. The algae at Narcisse also showed severe N and P deficiency throughout the year, while no similar deficiency was observed at Cruise Marsh. Epipelon biomass in unvegetated Narcisse sites was higher than found in vegetated Narcisse sites or at Cruise Marsh. Invertebrate abundance and biomass were lower at Narcisse. Cruise Marsh invertebrate abundance and biomass approached levels found in the more eutrophic Delta Marsh. The Narcisse wetlands do appear to be nutrient limited, which in turn affects the algae and higher order consumers like invertebrates. These low invertebrate levels likely play a role in the low use by waterfowl and other marsh birds in these wetlands.

Guest Editorial: The James Bay Hydroelectric Project - Issue of the Century

... The James Bay project has become a major issue because it involves a number of factors that represent a critical change in our outlook over the past twenty years. The first of these is the growth in popularity and scientific credibility of the environmental movement. Environmental awareness has flowered since the first phase of the James Bay project was begun. The environmental impact of the project was not a matter of great debate in the early '70s and no formal environmental assessment was ever done prior to construction of the first phase. It has only been since the mid-1970s that environmental impact assessments of major government projects have been performed on a regular basis in Canada. A surge in public concern about the state of the environment in the late 1980s came at the time Hydro-Quebec began preparations for the Great Whale phase of the project. As a result, the environmental impacts of the first phase have come under close scrutiny, and many of the concerns expressed by opponents in the 1970s have been substantiated. It has been shown that environmental impacts of the first phase include: methyl mercury contamination of water in reservoirs and downstream rivers and mercury accumulation in fish; reversal of the natural seasonal flow patterns of rivers; conversion of La Grande estuary from a saltwater environment to a freshwater one because of regulated peak flow in winter; changes in water temperatures in affected rivers; loss of wetland productivity; production of greenhouse gases by the decomposition of vegetation in inundated areas; destruction of shoreline and shoreline habitat (creation of dead zones) around reservoirs due to fluctuating water levels; riverbank erosion downstream from dams; and interference with animal migration routes. This presents a far different picture from the one advanced in the past of hydroelectricity as a clean, environmentally safe energy source. A second factor has been the internationalization of environmental issues. ... A third factor is our growing understanding of, and respect for, native peoples. ... Today, the idea of progress is undergoing a massive shift away from material and economic growth for growth's sake and toward what has come to be known as "sustainable development." The James Bay project might have been considered "the project of the century" in an earlier era. However, in the era of sustainable development, it must be regarded as something quite different.

Primary productivity and particulate organic matter flow in an estuarine mangrove-wetland in Hong Kong

Net primary productivity and organic matter flow of a mangrove-dominated wetland was estimated by following production and detritus dynamics in a tidal pond in north west Hong Kong in 1986–1988 (9.1 ha). Total productivity was 12.47 t dry wt ha−1 yr−1, of which >90% was from emergent macrophytes (the mangroveKandelia candel and the reedPhragmites communis). High turbidity and high summer temperatures probably limited respective production by phytoplankton and benthic macroalgae (dominated byEnteromorpha crinata). Despite the high total productivity, little detritus was exported from the emergent macrophyte stands, due to the low inundation frequency. This created a net water column carbon deficit which was provided for by the high organic matter import (mean = 4.42 g ash free dry wt m−2 d−1) from the incoming water. This same sediment and particulate organic carbon input giving a high accretion rate of 1.7 cm yr−1 was probably also the force behind progressive dis-coupling of emergent macrophyte production from water column consumers. This resulted in a tendency to retain production in the emergent macrophyte stands while the water column community increasingly relied on allochthonous carbon. This shift from a net exporter to a net importer of carbon in landward wetlands is probably characteristic of the transition into nutrient-conservative terrestrial systems.

Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions

A global data set on the geographic distribution and seasonality of freshwater wetlands and rice paddies has been compiled, comprising information at a spatial resolution of 2.5° by latitude and 5° by longitude. Global coverage of these wetlands total 5.7×106 km2 and 1.3×106 km2, respectively. Natural wetlands have been grouped into six categories following common terminology, i.e. bog, fen, swamp, marsh, floodplain, and shallow lake. Net primary productivity (NPP) of natural wetlands is estimated to be in the range of 4–9×1015 g dry matter per year. Rice paddies have an NPP of about 1.4×1015 g y−1. Extrapolation of measured CH4 emissions in individual ecosystems lead to global methane emission estimates of 40–160 Teragram (1 Tg=1012 g) from natural wetlands and 60–140 Tg from rice paddies per year. The mean emission of 170–200 Tg may come in about equal proportions from natural wetlands and paddies. Major source regions are located in the subtropics between 20 and 30° N, the tropics between 0 and 10° S, and the temperate-boreal region between 50 and 70° N. Emissions are highly seasonal, maximizing during summer in both hemispheres. The wide range of possible CH4 emissions shows the large uncertainties associated with the extrapolation of measured flux rates to global scale. More investigations into ecophysiological principals of methane emissions is warranted to arrive at better source estimates.

Growth and physiological condition of black ducks reared on acidified wetlands

Acid deposition has been identified as one of several possible factors contributing to the decline of some waterfowl populations in North America. In an effort to examine the effects of acidification on black duck (Anas rubripes) recruitment, growth and physiological condition were monitored in ducklings foraging for a 10–day trial (days 10–20 of life) on acidified (pH 5.0) and circumneutral (pH 6.8) fish-free emergent wetlands. Acidification of these wetlands suppressed phytoplankton and algal growth, and reduced invertebrate biomass. Ducklings maintained on acidified wetlands grew poorly compared with ducklings reared on circumneutral wetlands, as evidenced by lower final body weight and culmen and tarsus length. Plasma growth hormone concentration was elevated and triiodothyronine levels were lower in stunted ducklings, in part substantiating impairment of growth-regulating processes. Ducklings exhibiting poor growth tended to have lower hematocrit, lower plasma protein, glucose, and cholesterol concentrations, and higher uric acid levels, presumably reflecting alterations in metabolism and development due to inanition. These findings suggest that acid deposition may lower food production in wetlands and ultimately impair duckling growth, condition, and survival.

Studies of wetlands in India with emphasis on structure, primary production and management

This paper briefly reviews the Indian studies on community structure, standing crops and primary production in inland freshwater wetlands. The problem and the state of wetland management in India has also been briefly discussed.

WATERFOWL PRODUCTION AND WATER LEVEL FLUCTUATION

Water level fluctuation is probably the most significant environmental factor influencing waterfowl production. The three basic life processes of waterfowl in Canada, breeding, moulting and staging, are all affected by water level changes in the long and short term. The impact of water level fluctuations on breeding success is the most important way in which waterfowl production is influenced. Habitat suitability for waterfowl tends to reflect long-term water level fluctuations while habitat utilization can be affected in the short term by seasonal and annual changes in water level. The importance of magnitude, direction, rate and timing of water level fluctuations in determining waterfowl breeding success is discussed. Although waterfowl have developed a number of adaptations to cope with water level fluctuations, these responses are normally not completely effective and result in some degree of decreased production. Although having a number of negative impacts on waterfowl production, water level fluctuation is essential for the long-term maintenance of wetland productivity.

Primary Production and Seasonal Aspects of Emergent Plants in a Tidal Freshwater Marsh

Seasonal changes in aboveground plant biomass, cover, and frequency were monitored in Sweet Hall Marsh, a tidal freshwater marsh located on the Pamunkey River, Virginia, during the 1974 growing season.Peltandra virginica accumulated the most biomass, 423.40 g per m2, followed byLeersia oryzoides at 67.75 g per m2. Annual net community production was estimated to be 775.74 g per m2 by using a multiple-harvest technique. Comparisons with other studies revealed that production was somewhat low for tidal freshwater marshes but mostly higher than production in Virginia brackish and saline wetlands. Measurements revealed an annual succession of plant species from spring to fall. The pattern observed was early dominance byPeltandra followed by a rise in importance ofPolygonum spp.,Impatients capensis andLeersia.

Algal Mat Productivity: Comparisons in a Salt Marsh

This paper documents the role of salt marsh algal mats in the productivity of a southern California tidal wetland. The productivity of the mats, which are composed of filamentous bluegreen and green algae and diatoms, varies both temporally and spatially in relation to tidal inundation and overstory vegetation. The estimates of net primary productivity (NPP) were highest under the canopy ofJaumea carnosa (Less.) Gray (341 g C m−2 yr−1) at low elevation. Elsewhere, NPP appeared to be limited by low light (276 g C m−2 yr−1 underSpartina foliosa Trin.) and desiccation (185 g C m−2 yr−1 underBatis martima L. and 253 g C m−2 yr−1 underMonanthochloe littoralis Engelm).

Waterfowl Use of Uinta Mountain Wetlands in Utah

Waterfowl use was recorded in 1965 and 1966 at different elevations of the Uinta Mountains, Utah, from spring thaw until fall freeze-up. Sixteen species were observed; mallard (Anas platyrhynchos), green-winged teal (A. crecca), pintail (A. acuta), and ring-necked duck (Aythya collaris) were the most abundant. Ninety-eight percent of the observed waterfowl were below 3,000 m. Waterfowl numbers were highest during migratory periods and lowest in the breeding season. Adult waterfowl were seen most often on natural catchment basins and beaver (Castor canadensis) ponds larger than 0.4 ha. Low-elevation wetlands ( 2,900 m) had little waterfowl food. Utilization of high mountain wetlands by spring migrants and breeders was dependent upon ice melt, whereas freeze-up did not seriously affect fall use. J. WILDL. MANAGE. 41(1):172-117 Few intensive studies are available on the ecology of waterfowl in mountainous areas, and early mountain explorers wrote only brief notes on waterfowl observations at high elevations. Frary (1954) conducted a waterfowl production study on the White River Plateau in Colorado, and Rutherford and Hays (Unpublished data) investigated waterfowl breeding in the mountains surrounding the San Luis Valley, Colorado. Mallard, green-winged teal, and shoveler (Anas clypeata) were noted by Pattie and Verbeek (1966) on Beartooth Plateau, Montana. Several studies on waterfowl use and productivity of wetlands below 1,800 m have been conducted in Utah, but none has been made on the extent to which waterfowl use high mountain wetlands in Utah, nor on the contribution they made to the waterfowl resources of that state. Objectives of this study were to investigate species composition and seasonal changes in abundance of waterfowl in a high mountain area; define the types, distribution, and use of different wetlands; and estimate waterfowl production in a high mountain habitat. We thank the personnel of the Utah State Division of Wildlife Resources and the U.S. Fish and Wildlife Service for their financial support of this study, the U.S. Forest Service and Soil Conservation Service personnel for their valuable assistance, and the many recreationists who reported waterfowl observations.

Emerging Needs of Wetlands Protection for the Conservation of Wild Rice Biodiversity in Nepal: A Case Study from Lumbini Area

Nepal's wetlands are recognized critical habitats for several rare and endangered flora and fauna. Wild rice is one of the wetland products. There are 4 species of wild rice, Oryza rufipogon; O. nivara, O. granulata and O. officinalis occurring in Nepal, of which 3 species, Oryza rufipogon; O. nivara and O. officinalis are wetlands dependent. Oryza rufipogon and O. nivara are considered as progenitors of Asian cultivated rice (O. sativa). Attempt is made to assess the status of wetlands and wild rice in Lumbini area, distributed in Rupandehi and Kapilvastu districts. Many wetland sites, the important habitats of wild rice are degrading and getting lost due to encroachment for conversion into rice fields, fishponds, extended settlements, and sedimentation. A number of wild rice locations are observed in private wetlands that are prone to conversion into rice fields and fishponds. Although, local communities use wild rice during religio-cultural ceremonies, they are not well aware about the values of wetlands and often consider wild rice as weeds. The government policy has also not given due importance to the conservation of wild rice. It is expected that many wild rice sites would be lost in a few years time. This paper discusses conservation needs of some of the wetland sites of Lumbini area such as Budhi Tal, Ajingara Tal, RangpurTal and Kale Khan Tal for the preservation of wild rice gene pool. Key words: Wetlands; Conservation; Wild rice; Lumbini area. DOI: 10.3126/sw.v5i5.2664 Scientific World, Vol. 5, No. 5, July 2007 95-99