Meadow Zone Research Articles

Soil indicators of agricultural impacts on northern prairie wetlands: Cottonwood lake research area, north Dakota, USA

Potential damage to wetlands by land-use practices has prompted a need for relatively inexpensive, reliable indicators in monitoring ecological conditions. In this study, soil classification and the following soil tests, sodium bicarbonate-extractable P, nitrate (NO3 −), organic matter (OM), pH, clectrical conductivity (EC), and137Cs distribution, were used to compare four wetlands surrounded by cultivated land or grassland. Cumulic A horizons greater than 60-cm thick were found covering the wet meadow zone of the wetland surrounded by cultivated land. No cumulic A horizons were observed in wet meadow zones adjacent to grassland. Laboratory analyses of surface (0–15 cm) soil showed that the wetland surrounded by cultivated land had P cencentrations 2.5 to 6 times higher in the wet meadow and shallow marsh zones than did the other wetlands. In the wetland surrounded by cultivated land, the dominant soil separate in the wet meadow was silt, while sand was the dominant soil separate in the wet meadow zone in the other three wetlands. Phosphorus, OM, and NO3 − concentrations in wet meadow subsoils (15–60 cm) were higher in the wetland surrounded by cultivated land than in the wetlands surrounded by grasslands. Cesium-137 activities were about 3 to 6 times greater in surface (0–15 cm) soils collected from upland grassy slopes compared to cultivated slopes. Soil morphology,137Cs, P, and OM data indicate higher sedimentation and fertilization rates in wetlands next to cultivated fields.

Nature and cause of zonation discreteness around glacial prairie marshes

Species boundary clustering in zoned vegetation was examined along six wetland–upland coenoclines from four prairie marshes in eastern South Dakota that differed in size, permanence, water quality (salinity), topography, and exposure to waves. Vegetation structure and composition were measured from small, contiguous quadrats running through concentric vegetation zones. Rates of vegetation change along coenoclines were estimated using direct gradient analysis, detrended correspondence analysis, and a statistical technique that detects clustering of species' borders. All wetlands exhibited visually distinct zones, but quantitative analysis revealed that vegetation fomed a virtual continuum along the gradient in small wetlands, while near the shorelines of large wetlands both vegetation composition and structure were sharply discontinuous between marsh and meadow zones. This lower border of the meadow zone apparently was sharpened by exposure to waves and ice scour. The upper meadow zone border with prairie vegetation was less distinct but coincided with a sharp change in topography and in subsoil texture. Interspecific competition appeared less important than physical environmental factors in affecting zonation discreteness. The meadow–prairie zone contact approximates the upper limit of influence from wetland processes and is proposed as the wetland–upland border.

Methane flux from coastal salt marshes

The seasonal flux of methane to the atmosphere from salt marsh soils was examined in three different vegetation zones within a single marsh near Yorktown, Virginia. A total of 100 measurements were made over a 2‐year period, with maximum rates occurring during summer and fall. Spatial and temporal variability in fluxes was high; rates ranged from −2.4 to 21.3×10−3 g CH4/m2/d. Estimates of annual methane losses to the atmosphere were 0.43 g CH4/m2 for a salt meadow zone, 1.3 g CH4/m2 for short Spartina alterniflora, and 1.2 g CH4/m2 for tall creek‐bank S. alterniflora. A total of 63 flux measurements, made in a variety of other coastal salt marshes along the east coast of the United States, suggest that the Virginia site may be fairly typical for this region. In addition to diffusional losses across the air‐soil interface, methane can be lost from the marsh system to the atmosphere through the lateral movement of pore waters supersaturated with methane into tidal creeks, with subsequent degassing across the water‐air interface. Estimates of the magnitude of methane input to the atmosphere by this mechanism indicate it may be as important as diffusional losses across the air‐soil interface. These data suggest that salt marshes of this type make only a minor contribution to global atmospheric methane.

Phenology, Distribution and Survival of Atriplex triangularis Willd. in an Ohio Salt Pan

In an Athens Co., Ohio, salt pan, there were four vegetation zones: the Meadow, H or deum, Atriplex and Pan zones. These constituted a salinity gradient from the nonsaline Meadow to the highly saline Pan. The phenology, survival and distribution of the halophyte, Atriplex triangularis Willd., within this salt pan were investigated. The life cycle of A. triangularis spanned 9 months from February to October. The germination period extended from February to May. Flowers appeared in mid-July; seed development began in September. Senescence and death followed in late October. The population dynamics of A. triangularis were related to three main factors: soil temperature, soil moisture and soil salinity. Soil temperatures of 15 C appeared to trigger germination. High soil moisture values with consequent low soil salinity were prevalent during the winter-early spring germination period. Seedling establishment was particularly sensitive to salinity with severe mortality occurring in late spring and early summer when soil moisture values started to decline and salinity began to climb. The highest concentration of soil salts coincided with the flowering stage in July and August when soil moisture values dropped severely due to low rainfall and high evaporation. By the seed development and maturation stage in September, soil moisture levels had begun to rise due to heavy autumn rains and decreased evaporation which led to a decrease in total soil salts. The germination and survival of Atriplex triangularis were restricted in the main to the Atriplex zone. The relative absence of A. triangularis in the Meadow zone stemmed from the interference from the existing meadow vegetation. The rapid growth of Hordeum jubatum hindered the establishment of A. triangularis in the H or deum zone. High soil salinity within the Pan zone prevented the germination of A. triangularis.

Changes in the composition, structure, and production of plant communities along a perturbed wetland coenocline

Comparisons of a wetland coenocline before and after a drought-caused drawdown and the refilling of the basin to a higher-than-normal water level revealed that there was little difference in the above ground standing crop or in the floristic composition of the submersed, emergent or meadow zones along the coenocline. However, the position of many species along the coenocline shifted in response to these perturbations.Sagittaria latifolia, Carex spp.,Patamogeton sp. aff.pusillus all were found 2 to 4 m closer to shore.Glyceria grandis is normally found only in the meadow zone; but after the drawdown, it was found along the whole lenght of the coenocline. The drawdown also nearly eliminatedCeratophyllum demersum from the coenocline. Species richness as a result of these perturbations increased in the submersed (3.3 to 5.9) and emergent (3.6 to 4.3) zones, but decreased in the meadow zone (7.6 to 6.0). The Simpson's index in all three zones was not appreciably influenced by the perturbations. The average Simpson's indices for the meadow, emergent and submersed zones were 0.4, 0.7 and 0.5 respectively.