Glauca Godr Research Articles

Invasive Species Change Plant Community Composition of Preserved Prairie Pothole Wetlands

Plant communities in North American prairie pothole wetlands vary depending on hydrology, salinity, and anthropogenic disturbance in and around the wetland. We assessed prairie pothole conditions on United States Fish and Wildlife Service fee-title lands in North Dakota and South Dakota to improve our understanding of current conditions and plant community composition. Species-level data were collected at 200 randomly chosen temporary and seasonal wetland sites located on native prairie remnants (n = 48) and previously cultivated lands that were reseeded into perennial grassland (n = 152). The majority of species surveyed appeared infrequently and were low in relative cover. The four most frequently observed species were introduced invasive species common to the Prairie Pothole Region of North America. Our results suggested relative cover of a few invasive species (i.e., Bromus inermis Leyss., Phalaris arundinacea L., and Typha ×glauca Godr. (pro sp.) [angustifolia or domingensis × latifolia]) affect patterns of plant community composition. Wetlands in native and reseeded grasslands possessed distinct plant community composition related to invasive species' relative cover. Invasive species continue to be prevalent throughout the region and pose a major threat to biological diversity, even in protected native prairie remnants. Despite efforts to convert past agricultural land into biologically diverse, productive ecosystems, invasive species continue to dominate these landscapes and are becoming prominent in prairie potholes located in native areas.

Long-term environmental change and shifts in the aquatic plant community of Jones Creek, Thousand Islands National Park, Ontario, Canada based on plant macrofossil analysis

Plant macrofossils and pollen were analyzed from sediment cores to identify long-term changes in the aquatic plant community of Jones Creek, Thousand Islands National Park, Ontario, Canada. Six sediment cores were recovered from Jones Creek in February 2014. One complete core and five top/bottom samples were analyzed for plant macrofossil abundance and diversity. Sediment analysis and 210Pb dating confirmed a productive wetland throughout the core, dating back beyond 1883 AD. Jones Creek is currently dominated by thick stands of cattails, particularly the hybrid white cattail (Typha x glauca Godr). The relative abundance of Typha pollen began to increase in the late nineteenth and early twentieth century, reaching a relative abundance of nearly 40% in the modern day surface sediment. Common macrofossils recovered from the sediment record included seeds of Carex, Schoenoplectus, Najas, and Eleocharis. There is evidence that community composition, as recorded by the macrofossil record, has shifted in Jones Creek in response to human activities. In particular there has been a reduction in sedge species between historical and present day conditions as the wetland shifted from a sedge dominated wet-meadow wetland to a cattail dominated system. The results of our study indicate that future restoration efforts should be directed towards reintroducing native sedge species that were present prior to major changes in land-use that occurred in the St. Lawrence region throughout the nineteenth and twentieth centuries.

Variation in fiber cables in the lacunae of leaves in hybrid swarms of Typha × glauca

The presence or absence of fiber cables in the lacunae of the last formed leaf blades of flowering Typha plants is a diagnostic character. The fiber cables are present in all leaves of Typha angustifolia L., but are absent in the last formed leaves of Typha latifolia L. We find great variation in the presence of fiber cables in the last formed leaves of individuals in stands of Typha×glauca Godr. (pro sp.). We find that individuals that comprise the hybrid swarms that are closer to T. angustifolia in terms of standard characters have fiber cables in most or all of the last formed leaf blades before the inflorescence. By contrast, those individuals closer to T. latifolia in terms of standard characters do not have fiber cables in the last formed leaves before the inflorescence. The lengths of the longest fiber cables are correlated with the lengths of the leaves in T. angustifolia and the “angustifolioid” T.×glauca, but not in T. latifolia and the “latifolioid” T.×glauca. The variability in the taxonomically, morphologically and biomechanically-significant fiber cables in the lacunae in reproductive plants may be useful in characterizing and understanding the composition of a Typha stand.

Organic matter stocks increase with degree of invasion in temperate inland wetlands

Aims Wetlands provide a variety of ecosystem services, including nitrogen retention and carbon sequestration, and these services are linked through the storage and transformation of organic matter that can be altered by invasive plant species. We hypothesized that within inland temperate wetlands, the degree of invasion by Phragmites australis (Cav) Trin. Ex Steud, Phalaris arundinacea L. and Typha x glauca Godr. X would be positively correlated with soil and ecosystem C and N stocks because these invasive plants produce large amounts of recalcitrant litter.

Typha glauca Godron and its parental plants in Poland: taxonomic characteristics

Natural interspecific hybridization between Typha latifolia L. and Typha angustifolia L. was analyzed by morpho-anatomical and molecular methods to determine whether the hybrid Typha glauca Godr. is present in Poland and to identify the best diagnostic traits for its identification. Eighty-three samples of the Typha species were collected. Nine random amplified polymorphic DNA (RAPD) primers provided 12 fragments specific for T. angustifolia and eight fragments specific for T. latifolia. DNA of all sampled individuals was analyzed with 20 diagnostic RAPD markers. The morpho-anatomical variability of T. glauca F1 was found to be quite similar to that observed in parental plants. All of the 41 traits examined in the hybrids overlapped with those observed in the parents, however, the hybrids were visibly closer to T. angustifolia than to T. latifolia. The most discriminate characteristics were the length and pedicel width, as well as the epidermal cell thickness located above vascular bundles in leaf blades. Moreover, preliminary observations of seed sculpture showed that the length of testa cells could also be used to identify T. glauca. Clusters and the hybrid index (for molecular and morphological data) were highly coincident and support the hybridization hypothesis.

Appropriation of nitrogen by the invasive cattail Typha × glauca

A 15N-addition mesocosm experiment was used to study competition for nitrogen (N) between the aggressive cattail species Typha×glauca (T. latifolia×T. angustifolia) Godr. (hybrid cattail) and a suite of native plant species often found in marshes Typha invades. Plant uptake of 15N released from labeled Typha and native-species litter was then measured in a pot experiment with new cohorts of two native plant species (Juncus balticus Willd. and Schoenoplectus acutus Muhlenberg ex Bigelow) grown with and without Typha. In both experiments, species differed in their above- and belowground uptake of 15N, with Typha outperforming the other species (1.7–5.0-times greater mean uptake, P=<0.0001–0.007). Typha then held on more strongly to the N it acquired: newly grown native plants in the pot experiment acquired more 15N from native litter than from Typha litter (1.4–12.0-times greater mean uptake, P=0.0006–0.017). In contrast, Typha showed no differences in N uptake by litter type (P=0.16–0.54). There were no main effects of live Typha on native-plant N uptake (P=0.64–0.86), but there were modest interactions between Typha presence and litter type (P=0.030–0.091). Where native plants and Typha co-occurred, native species matched Typha in recovering 15N from native litter (P=0.17–0.33) but recovered 90–96% less 15N from Typha litter (P=0.020–0.021). Typha's higher overall N recovery was due to both greater biomass production and uptake efficiency (15N per unit dry weight). Typha's greater N uptake and retention, repeated over multiple cycles of senescence and new growth, should lead to an increasing appropriation of N away from native species and into living and dead Typha biomass.

Mechanisms of dominance by the invasive hybrid cattail Typha × glauca

The mechanisms by which invasive plants displace native species are often not well elucidated, limiting knowledge of invasion dynamics and the scientific basis for management responses. Typha × glauca Godr. invades wetlands throughout much of North America. Like other problematic wetland invaders, Typha is large, grows densely, and leaves behind copious litter. It thus has the potential to impact wetlands both in life and after death. We assessed patterns in field settings and used simulated wetland-plant communities to experimentally test abiotic and community responses to live Typha, Typha litter, and water-level differences (confounded in the field) using a full-factorial design. In general, litter was a stronger driver of change than live Typha. The greatest impacts were seen where, as in nature, live and dead Typha co-occurred. Live-Typha treatments did not differ from controls in light or temperature conditions but did reduce community biomass and alter community composition. Litter strongly affected light, temperature and its variability, community and species-level plant biomass, and community composition. Interactions between live Typha and litter affected aspects of plant-community composition. Advantageously for Typha, interspecific litter effects were not mirrored by intraspecific suppression of live Typha. These findings clarify how Typha is such an effective invader. Similar mechanisms are likely involved in invasions by other plant species, particularly in wetlands. Managers should respond quickly to new Typha invasions and, when dealing with established stands, remove litter in addition to eradicating live plants.

Holocene Vegetation Dynamics of an Upper St. Lawrence River Wetland: Paleoecological Evidence for a Recent Increase in Cattail (Typha)

Cattails (Typha latifolia L., Typha angustifolia L., and Typha x glauca Godr.) are the predominant emergent vegetation of upper St. Lawrence River coastal wetlands. We sought to describe Holocene vegetation in a St. Lawrence River wetland to assess patterns of succession and examine the timing and potential causes of a historic cattail invasion. Paleoecological analysis indicated presence of four distinct wetland vegetation stages, including a shallow water marsh (8240 YBP to 5160 YBP), a variable-depth aquatic plant community with adjacent alder (5160 YBP to 1610 YBP), a shallow sedge community (1610 YBP to 100 YBP), and a robust emergent marsh (100 YBP to present). The record of pollen tetrads demonstrated cattail presence throughout the history of the marsh, but a rapid increase in relative abundance of Typha cf. angustifolia/Sparganium monads indicated major expansion of robust emergent plants beginning near the peak of agricultural activity (ca. 1880 AD) and reaching modern levels around 1940 AD. Increase in the abundance of robust emergents in this wetland occurred decades before regulation of St. Lawrence River water levels and were contemporary with increased sedimentation and changes associated with the early agricultural period.

Do seed banks confer resilience to coastal wetlands invaded by Typha ×glauca?

Historically, seed banks conferred resilience to Laurentian Great Lakes coastal wetlands by providing propagules of many species to replace invasive plants, such as Typha ×glauca Godr. After flooding, the seed bank could allow recovery of wetland composition and structure as the water levels fall. Using the seedling emergence method to estimate seed density, species and guild richness, and floristic quality, we evaluated the resilience of five wetlands along the western coast of Green Bay, Lake Michigan by comparing seed bank attributes in areas invaded by Typha to those of neighboring uninvaded areas and to attributes of the extant vegetation. Resilience decreased from north to south among the five wetlands, mirroring a gradient of decreasing water quality. The invasive Lythrum salicaria L. dominated the seed bank of all five wetlands despite low relative abundance in the extant vegetation. The resilience of Green Bay coastal wetlands is threatened by the overwhelming presence of L. salicaria in the seed bank. Because the seed bank holds a wetland’s potential to be renewed by the natural hydrological cycle, seed bank assessment should be a routine measure of wetland resilience.

Differences in wetland plant community establishment with additions of nitrate-N and invasive species (Phalaris arundinacea and Typha ×glauca)

Restored prairie pothole wetlands in North America are often enriched by nitrate-N (NO3-N) that has been lost from surrounding agricultural systems. In addition, these wetlands are increasingly colonized by invasive taxa including Phalaris arundinacea L. and Typha ×glauca Godr. To explore the impacts of NO3-N enrichment, suppression by invasive species, and the interaction of these factors on restored communities, we grew native sedge meadow communities from seed in greenhouse mesocosms and subjected them to NO3-N and invasive species for 4 months. Typha ×glauca did not reduce overall native community biomass and actually enhanced Aster spp. biomass. Phalaris arundinacea suppressed growth of the native community to an equal relative extent across all NO3-N levels. The shoot biomass of the entire native community in untreated plots was similar to the P. arundinacea fraction of the treated plots. Phalaris arundinacea demonstrated greater plasticity in root-shoot allocation than the native community over the range of NO3-N inputs. Proportional allocation to root biomass was greater for P. arundinacea than for the native community at all but the highest NO3-N level. Both factors may be important in explaining dominance of P. arundinacea over the native community in a range of fertility conditions. Regardless of NO3-N inputs, the restoration of diverse native wetlands requires strict control of P. arundinacea during community establishment, as evidenced by the relatively rapid rate of suppression of native community biomass by P. arundinacea compared with T. ×glauca.Key words: restoration, agricultural impacts, prairie pothole, root/shoot ratio.

Morphological analysis of genetically identified cattails Typha latifolia, Typha angustifolia, and Typha ×glauca

Hybridization between the cattail species Typha latifolia L. and Typha angustifolia L. is frequent throughout northeastern and central North America. While studies are required to elucidate the ecological role of interspecific hybrids, morphological intergradation of the hybrids and parental species limits accurate identification. Although species-specific molecular markers have been developed, some researchers do not have the resources necessary for molecular analysis. Consequently, this study used genetically identified specimens of T. latifolia,T. angustifolia, and their hybrid Typha ×glauca Godr. to discriminate sound taxonomic characters for morphological identification. Leaf width, spike gap, spike width, and spike length were measured for 153 specimens of cattails from Massachusetts, Ontario, Quebec, and Manitoba. In addition, stigma width was measured using a compound microscope. Morphological data were used in discriminant analysis; approximately 90% of the classifications derived by discriminant analysis corresponded to the genetic identity. Discriminant analysis using stigma width, spike length, spike interval and leaf width provided accurate identification for 28 of 31 T. angustifolia specimens, 38 of 41 T. ×glauca specimens, and 20 of 25 T. latifolia specimens. Thus, discriminant analysis of morphological characters can be used to distinguish the hybrid cattail from the parental species with reasonable confidence when molecular resources are not available.Key words: Typha, cattails, discriminant analysis, DNA markers.

Development of the endodermis and hypodermis of Typha glauca Godr. and Typha angustifolia L. roots

The development of the endodermis and hypodermis in adventitious roots of Typha angustifolia L. and Typha glauca Godr. was followed from the apical meristem to full maturity. The endodermis was typical, developing a thin Casparian band near the root tip, followed by suberin lamellae and asymmetric, secondary, lignified walls (C-type at maturity). Passage cells were present at an intermediate stage but eventually disappeared when all cells developed lamellae and secondary walls. The hypodermis was multiple (four to six layers at maturity) and began differentiating near the root tip. Here, the radial and transverse walls of the outermost layer did not dissolve in strong acid and the former were wavy in the longitudinal direction, both features characteristic of a Casparian band, but these walls were permeable to berberine. No other indication of a wall modification was seen for 3 weeks, at which time the root had become determinate and aerenchyma was beginning to form in the midcortex. Casparian bands, which were impermeable to berberine, matured in the hypodermis; thus, it proved to be an exodermis. Different forms of Casparian band were detected: one was typical and occupied the radial and transverse walls of the outermost layer, but others were novel and included tangential walls, often forming an H-shaped structure (as seen in cross section of the root). We propose calling the latter type an H-type Casparian band. It functioned as an apoplastic barrier to berberine applied either externally or internally by injection into the cortical aerenchyma. Following maturation of the Casparian band, the outer two layers of the exodermis soon produced suberin lamellae. These continued to be deposited in a centripetal pattern until they were found in all layers of the multiple exodermis. Development of the suberin wall modifications correlates with the development of the aerenchyma and may play a role in preventing gas exchange between the root and the rhizosphere. Later, all exodermal cells produced lignified, secondary walls. These were asymmetric in the outermost and innermost layers of the hypodermis (like the C-type endodermis); eventually, all layers had Casparian wall materials. Thus, the mature hypodermis consisted of two to six layers of exodermis, except at the tips of determinate roots where the exodermis was uniseriate with typical Casparian bands.Key words: cattail, endodermis, exodermis, hypodermis, roots, Typha.

Morphological analysis of genetically identified cattails &lt;i&gt;Typha latifolia&lt;/i&gt;, &lt;i&gt;Typha angustifolia&lt;/i&gt;, and &lt;i&gt;Typha קlauca&lt;/i&gt;

Hybridization between the cattail species Typha latifolia L. and Typha angustifolia L. is frequent throughout northeastern and central North America. While studies are required to elucidate the ecological role of interspecific hybrids, morphological intergradation of the hybrids and parental species limits accurate identification. Although species-specific molecular markers have been developed, some researchers do not have the resources necessary for molecular analysis. Consequently, this study used genetically identified specimens of T. latifolia, T. angustifolia, and their hybrid Typha ×glauca Godr. to discriminate sound taxonomic characters for morphological identification. Leaf width, spike gap, spike width, and spike length were measured for 153 specimens of cattails from Massachusetts, Ontario, Quebec, and Manitoba. In addition, stigma width was measured using a compound microscope. Morphological data were used in discriminant analysis; approximately 90% of the classifications derived by discriminant analysis corresponded to the genetic identity. Discriminant analysis using stigma width, spike length, spike interval and leaf width provided accurate identification for 28 of 31 T. angustifolia specimens, 38 of 41 T.× glauca specimens, and 20 of 25 T. latifolia specimens. Thus, discriminant analysis of morphological characters can be used to distinguish the hybrid cattail from the parental species with reasonable confidence when molecular resources are not available.

Vesicular-Arbuscular Endomycorrhizal Colonization of Wetland Plants.

Mycorrhizal fungi colonize many terrestrial plants and often result in an increased uptake of P and several micronutrients. Little information is available on the relationships among vesicular-arbuscular endomycorrhizae (VAM), aquatic plants, and plant P concentrations. The major objectives of this study were to measure the degree of VAM colonization of wetland plants, and to determine the relationship between colonization and plant P concentrations when sampled from two contrasting water regimes (hydric soil with no surface water and hydric soil with a minimum of 10 cm of surface water). Two semipermanent wetlands in Lake County, South Dakota, were chosen for the study. Water regime did not have a significant effect on total or organic soil P concentration. Vesicular-arbuscular endomycorrhizal spore samples collected from wet soils averaged 5000 spores kg-1 compared with 2740 spores kg-1 in dry soils. The eight plant species evaluated to determine VAM colonization were reed canarygrass (Phalaris arundinacea L.), slough sedge (Carex atherodes Spreng.), river bulrush [Scirpus fluviatilis (Torr.) Gray], slender rush (Juncus tenuis Willd.), dogbane (Apocynum cannabinum L.), water smartweed (Polygonum amphibium L.), cattail (Typha X glauca Godr.), and wild licorice (Glycyrrhiza lepidota (Nutt.) Pursh). Vescular-arbuscular endomycorrhizal colonization ranged from 78% (wild licorice) to none (slough sedge and slender rush). Roots from dry areas averaged 27% colonization compared with less than 1% in wet areas. Colonization levels of dogbane and reed canarygrass in dry zones were highly correlated to plant P concentrations. The results of this study indicate that several wetland plant species develop substantial mycorrhizal associations, particularly in relatively dry environments.

Effects of prolonged flooding on the distribution and biomass of emergent species along a freshwater wetland coenocline

Water levels were raised 1 m for two years in 10 cells of an experimental wetland complex located in the Delta Marsh, Manitoba, Canada. The mean area covered by each of the 5 dominant emergent species in these cells declined significantly during the first year of flooding. There was no significant difference in the total acreage of ?mergents between flooding years. Three species were completely {Carex atherodes Spreng, Scolochloa festucacea (Willd.) Link) or almost {Scirpus lacustris L. spp. glaucus (Sm.) Hartm.) eliminated from the cells. Typha glauca Godr. and Phragmites australis (Cav.) Trin. still covered in the second year of flooding about 40 and 25%, respectively, of the area that they had occupied in the cells in the preflooding year. The mean elevation at which the two surviving species were found both increased 0.1 and 0.2 m over preflooding elevations during the first and second year of flooding, respectively. There is no evidence that during the flooding years any species migrated upslope toward more optimal water depths. Aboveground standing crop for all five species declined significantly during the first year of flooding, but was not significantly different between the two flooding years. Total belowground biomass did not differ between spring and fall, but declined significantly (about 20%) during the first year of flooding and remained about at that level during the second year. In the spring following the two years of flooding, mean total belowground biomass was only 40 g m-2, less than 10% of the belowground biomass dur ing the preflooding year.

Loss and assimilation of 15N-nitrate added to a North Dakota cattail marsh

Field 15N balance studies were conducted to determine the fate of K 15NO 3 added during summer to surface water in 0.27 m 2 plots within a North Dakota cattail (a mixture of Typha glauca Godr. and Typha angustifolia L.) marsh. In a 1989 study, 50.4 mmol 15NO 3 −-N (approximately 1.1 mmol NO 3 − 1 −1) disappeared within 8 days after a temporary build-up of NO 2 −-N. Approximately 42% of the applied 15N remained in the marsh. This residual N was found in cattail roots and rhizomes (9.5%), floating plants ( Lemna minor L. and Spirodela polyrhiza (L.) Schleiden) (8.9%), soil (8.3%), litter (6.9%), surface water (4.6%) and cattail shoots (4.1%). The missing 15N (58%) was presumably lost as a result of denitrification. In a 1991 experiment, 50.4 mmol of K 15NO 3 was added to plots which had previously received additions of deionized water or 153 mmol of unlabeled KNO 3. All the labeled NO 3 − again disappeared within 8 days. The unaccounted-for 15N was approximately 56% and 82% of the added K 15NO 3-N in plots without and with the antecedent unlabeled KNO 3 treatment, respectively. The difference in recovery (26%) was highly significant. Stimulation of dissimilatory NO 3 − and NO 2 − reductases and/or suppression of dissimilatory reduction of 15NO 3 − to 15NH 4 + are postulated as likely factors for the higher apparent denitrification loss associated with the antecedent KNO 3 treatment.

Nektonic invertebrate abundance and distribution at the emergent vegetation-open water interface in the Delta Marsh, Manitoba, Canada

The emergent vegetation-open water interface plays an important role in the use of freshwater wetlands by many species of animals. The objective of this study was to monitor the distribution and abundance of free-swimming invertebrates at the cattail (Typha × glauca Godr.)—open water interface in two bays (sheltered and unsheltered) in the Delta Marsh in south-central Manitoba during 1985. Submersed vegetation densities were higher in the open water sites of the sheltered bay during most of the summer. Water temperatures were constant across the interface through much of the year. By mid-summer, hypoxic conditions prevailed within the water column in the cattail stand. Algae levels were similar across the interface throughout much of the year, with peaks occurring just inside the interface in June and July. Early in the season, there was a trend for higher nektonic invertebrate numbers within the cattail stands of both bays. By late August, there were similar total invertebrate numbers across the interface. Cladocera and ostracod numbers were higher within the cattail stands during June and July; during the same periods, corixid levels were higher in the open water sites. The low oxygen levels within the cattail stands during the summar may reduce predation by fish and other predators that cannot tolerate low oxygen levels. This may explain the higher numbers of prey species like cladocerans and ostracods within the cattail stands during mid-summer. The presence of algal or detrital food resources seemed to have little influence on invertebrate abundance across the interface during this study. Peaks in invertebrate abundance did not occur at the emergent vegetation-open water interface during any of the sampling periods in this study. The high invertebrate diversity and abundance in interspersed wetland habitat may be related more to the mixture of habitat types rather than the amount of interface present.

A field study of the effects of water depth, order of emergence and flowering on the growth of Typha glauca shoots using the Richards model

The effects of water depth, order of emergence and flowering on growth curves of hybrid cattail ( Typha glauca Godr.) shoots growing in permanent quadrats were analyzed using Ebert's formulation of the Richards function. Although estimate variability was high and heterogeneous, the model produced a good fit when applied to height measurements of individual shoots. The logistic ( n=1) described the typical growth curve of vegetative shoots, with a grand mean of n=1.15. Although maximal size increased with depth in the 25–65 cm range, the shape parameter ( n) of early emerging vegetative shoots was not substantially altered by position along the water depth gradient. The mean n value for the first vegetative cohort at 25–65 cm was 1.54. There was a substantial increase in estimate variability in the second vegetative cohort, suggesting that delayed emergence imposes a greater stress on T. glauca shoot growth than water depth per se. The mean n value for all depths declined to n=0.55. Floral shoots had a lower mean n value ( n=0.28), coupled with low estimate variability and high weighted relative growth rates. These shoots exercise priority within the clonal mass, diverting resources from vegetative expansion.

Hydraulic Conductivity and Nitrogen Removal in an Artificial Wetland System

AbstractA greenhouse study using aquatic macrophytes rooted in sand was conducted to test if the presence of belowground plant material increases or maintains permeability in horizontal subsurface flow systems constructed for wastewater treatment. Nutrient solutions low in suspended solids (SS) and biochemical oxygen demand (BOD) were substituted for actual wastewater. Three batch applications of NH4‐N and three of NO3‐N were added for 48‐h periods at concentrations of approximately 20, 55, and 80 mg L−1 to assess the ability of these systems to remove N. Saturated hydraulic conductivity, Ks, was monitored over 236 d in boxes of sand planted with two different aquatic macrophytes—Typha glauca Godr. and Scirpus acutus Muhl. The Ks decreased over time in the vegetated and nonvegetated (control) systems. The decrease was significantly greater in the vegetated systems (55%) than in the control (41%). Despite these decreases, Ks at the end of the study was still high (0.62 cm s−1) even in the vegetated systems. The vegetated systems were significantly more effective than the nonvegetated at removal of NH4‐N and NO3‐N. No significant difference was noted in the N removal efficiency of the two plant species. Our results suggest that artificial wetlands using sand can be used to remove N from wastewater, but decreased soil permeability may occur.

A field study of the morphometric response of Typha glauca shoots to a water depth gradient

In the Delta Marsh, Manitoba, the hybrid cattail Typha glauca Godr. forms large monodominant stands over a wide range of water depths (25–100 cm). Despite a considerable body of research concerning the origin and development of this important species, its ecology has received little attention. In field studies conducted in two freshwater wetland sites in the Delta Marsh, mean height and biomass of vegetative shoots of T. glauca increased significantly along a gradient of increasing water depth. Product–moment correlations between height and biomass were [Formula: see text]. Flowering shoots, in contrast, were less flexible in their response to depth. No significant differences associated with depth were found in reproductive biomass, height, spike width, spike length, or gap length of flowering spikes harvested in August. Differences in size of vegetative shoots were interpreted as a plastic response that may play a role in adaptation to a range of water depths. By adjusting the length of underwater shoot tissue, the ramet maintains relatively constant aerial shoot dimensions. Growth of shoots in deep water is enhanced by an intrinsic factor (juvenility) and an environmental factor (edge effect). Key words: Typha glauca, water depth, growth, plasticity, field study, morphometric response.