Typha latifolia and Cladium jamaicense litter decay in response to exogenous nutrient enrichment

The role of nutrient availability in the decay of Typha latifolia and Cladium jamaicense litter and associated microbial responses were studied under controlled experimental conditions. The experimental setup consisted of three 14 m² mesocosms: (i) an experimentally enriched (N&P) mesocosm containing organic soil, (ii) a mesocosm with organic soil but no external enrichment, and (iii) a mesocosm with no external nutrient inputs and a mineral soil, each equally divided into two areas predominated by T. latifolia and C. jamaicense. Air dried senesced material of each plant species from the three units were placed in litterbags and were introduced back into their respective communities on the soil and water interface. Litter from T. latifolia degraded significantly faster than that of C. jamaicense. The half life of T. latifolia litter averaged approximately 274 days, C. jamaicense litter half life was extrapolated to approximately 377 days. Nutrient enrichment significantly increased the decay rates of T. latifolia, the nutrient effect on C. jamaicense decomposition was less apparent. The microbial biomass carbon in T. latifolia and C. jamaicense litter increased significantly as the litter decomposed. No significant differences between the litter types or amongst mesocosms were found. The relative activities of the extracellular enzymes acid phosphatase and β-glucosidase were significantly (P < 0.001 and P = 0.0284, respectively) affected by litter type and mesocosm over time. Litter associated alkaline phosphatase activity was largest in the mineral mesocosm, followed by the organic control and then organic enriched irrespective of litter type, β-glucosidase activity showed an inverse effect, enriched organic > organic control > mineral. The litter CO₂ and CH₄ microbial production rates showed a significant litter type and mesocosm effect (P = 0.0003 and 0.001, respectively). T. latifolia litter had larger associated methanogenic and microbial respiration rates than C. jamaicense litter. Nutrient enrichment enhanced both forms of microbial metabolic activities (CO₂ and CH₄ production). The effect of nutrient enrichment was primarily evident in the initial (3–6 months) period of decay, extracellular enzyme activities and the litter associated microbial metabolic activities showed most response during this decay stage.     

Roots of the wetland plants Typha latifolia and Phragmites australis are inhabited by methanotrophic bacteria in biofilms

Wetland plants create partly aerobic conditions in the rhizosphere by releasing oxygen to the waterlogged substrate. The present study was conducted to characterise the arrangement of rhizobacteria, especially those active in methane oxidation, in root-associated biofilms of wetland plants. Root cross sections sampled from Typha latifolia L. (broadleafed cattail) and Phragmites australis (Cav.) Trin. ex Steud. (common reed) were scanned using light and electron microscopy. Methane-oxidising bacteria were identified and quantified by immunological labelling of the α-subunit of the methanol dehydrogenase (α-MDH; encoded in mxaF). On roots of both species there was a diverse subset of bacteria arranged in a microbial biofilm around the roots’ exodermis. Similar bacterial densities in the root-associated biofilm were detected in more basal regions and closer to the root tip. Many microbes carried notable internal membrane systems that are characteristic of methanotrophic bacteria. This morpho-anatomical characterisation was confirmed by immunogold labelling with α-MDH antibodies. Quantification of labelled bacteria revealed that 34–43% of the biofilm bacteria were potentially capable of methane turnover. These findings confirm the presence of methane-oxidising bacteria in the root-associated biofilms of the two common macrophytes T. latifolia and P. australis. This implies that the methanotrophs participate essentially in the microbial processes related to oxygen-releasing roots of wetland plants.     

Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis

Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD₅) (from an inlet of 420 to 1000 mg L⁻¹) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L⁻¹), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha⁻¹ d⁻¹ and 529 kg BOD₅ ha⁻¹ d⁻¹ were achieved for a loading ranging from 242 to 1925 kg COD ha⁻¹ d⁻¹ and from 126 to 900 kg BOD₅ ha⁻¹ d⁻¹. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.     

Estimation of size and number of individual plants within populations of Typha latifolia L. using isoelectrofocusing (IEF)

The number and size of individual plants of Typha latifolia L. was determined on the basis of pollen proteins separated by the technique of isoelectric focusing. In a mature stand the individuals of T. latifolia were large and each had many flowering shoots (fertile shoots to pollen protein ratio of 3.5), while in pioneer (ratio of 2.5) and degenerating stands (ratio of 2.5) there were relatively more individuals, but each was smaller than those in mature stands.     

Role of plant aeration in zonation of Zizania latifolia and Phragmites australis

The emergent plants Phragmites australis (Cav.) Trin. ex Steud and Zizania latifolia (Griseb.) Stapf. are distributed along a gradient of increasing water depth, with P. australis restricted to shallow water and Z. latifolia to deeper water. The lower limits of the two vegetational zones were discussed from the view-point of oxygen supply from aerial shoots. The oxygen influx to the underground organs from aerial shoots is proportional to the gradient between oxygen concentrations in atmosphere and inside the basal stem (C). The proportional constant (Q), called here the ventilation coefficient, expresses the efficiency of the diffusion of oxygen. An attempt was made to measure Q and C. The values of Q for the two species in their dominant niches are higher in Z. latifolia than in P. australis, corresponding to the natural distribution with increasing depths of water. Q in Z. latifolia and P. australis first increased and then decreased. Corresponding to such changes of Q, the oxygen concentration inside the basal stem (C) fell to low values for Z. latifolia at the greatest water-depth. Since in Z. latifolia a low value of C in deeper waters was accompanied by a decline in standing crop of aerial shoots, it was concluded that oxygen is the limiting factor for the distribution of Z. latifolia in the deeper waters.     

Mechanisms of cadmium detoxification in cattail (Typha angustifolia L.)

Cadmium (Cd) is a widespread heavy metal pollutant and environmental and human health hazard, which may be partially resolved using green and cost-effective phytoremediation techniques. However, the efficiency of phytoremediation is often limited by the small biomass of Cd-hyperaccumulator plants. Although cattail (Typha angustifolia L.) is tolerant of heavy metals and has a high biomass, there is little information available on its detoxification mechanisms for heavy metals, especially Cd. In the present study we investigated the tolerance of cattail to Cd and mechanisms involved in its Cd detoxification. Our results show that: (a) cattail is tolerant of Cd; (b) the root Casparian band, cell wall, vacuole, glutathione (GSH), and glutathione peroxidase (GPX) play important roles in Cd detoxification; and (c) mechanisms of Cd detoxification differ in leaf cell cytoplasm (mainly a GSH-related antioxidant defense system) and root cell cytoplasm (mainly a GSH-related chelation system). In summary, cattail possesses multiple detoxification mechanisms for Cd and is a promising species for phytoremediation of Cd-polluted environments.     

Multiple elements in Typha angustifolia rhizosphere and plants: Wetland versus dryland

In a recent study, researchers found that multiple elements accumulated near the roots of Rumex crispus more under wetland conditions and element uptake was significantly greater in the plants grown under wetland compared to dryland conditions. The study reported here also found that elements accumulated in the root zone (up to 3 mm beyond the rhizoplane) of Typha angustifolia grown under wetland conditions. In comparison to the bulk zone, Be, Cu, Fe, Li, Sr and Zn accumulated more in the root zone of the flooded treatment whereas Ni and Sr accumulated more in the root zone of the non-flooded treatment. On average, T. angustifolia produced 4 times more biomass and element uptake was 2-27 times greater under wetland compared to dryland conditions.     

Crustose lichens as indicators of forest continuity in boreal coniferous forests

The crustose lichen flora of fifteen areas in boreal coniferous forests from southern Sweden to Lapland was surveyed. Many of these areas are included in a national programme for monitoring long-term environmental change, the PMK programme. In all 190 species were recorded, 129 of them occurring on bark of conifers and lignum. Some species were found exclusively in forests with a long continuity. By using ordination and hierarchical classifications further species with similar habitat requirements were identified. An Indicator Species Index of Forest Continuity (ISIFC) was designed. Only two of the twenty index species occur on deciduous trees. The ISIFC was highly correlated with forest continuity and also with occurrence of species listed as threatened. Correlations with macroclimatic variables are considered sampling artifacts, and microclimatic factors are suggested to be of primary importance for species occurring in forests with a long continuity.     

Use of forest corridors by boreal Xestia moths

Abstract We studied movements of the noctuid moths Xestia speciosa and X. fennica in a fragmented forest landscape including old-growth spruce forest corridors in eastern Finland. We individually marked and released 1,796 adults of the habitat generalist X. speciosa and 683 individuals of X. fennica, which prefers old-growth spruce forests. Moths were recaptured with 60 sugar-bait traps that were placed within habitat corridors, in the non-habitat matrix and in surrounding old-growth forest patches. Both species favoured the corridors during their movements and tended to avoid entering the matrix. We analysed recapture rates and movements of the recaptured moths. Results suggest that X. speciosa moves longer distances than X. fennica. Though corridors clearly canalized movements by both species, the impact of old-growth forest corridors at the larger landscape scale was less clear in X. fennica. Movement behaviour of the two sexes differed more than that of the two species.     

Microbial transformations of C and N in a boreal forest floor as affected by temperature

The effects of temperature on N mineralization were studied in two organic surface horizons (LF and H) of soil from a boreal forest. The soil was incubated at 5 °C and 15 °C after adding ¹⁵ N and gross N fluxes were calculated using a numerical simulation model. The model was calibrated on microbial C and N, basal respiration, and KCl-extractable NH₄ ⁺, NO₃ ⁻, ¹⁵NH₄ ⁺ and ¹⁵ NO₃ ⁻. In the LF layer, increased temperature resulted in a faster turnover of all N pools. In both layers net N mineralization did not increase at elevated temperature because both gross NH₄ ⁺ mineralization and NH₄ ⁺ immobilization increased. In the H layer, however, both gross NH₄ ⁺ mineralization and NH₄ ⁺ immobilization were lower at 15 °C than at 5 °C and the model predicted a decrease in microbial turnover rate at higher temperature although measured microbial activity was higher. The decrease in gross N fluxes in spite of increased microbial activity in the H layer at elevated temperature may have been caused by uptake of organic N. The model predicted a decrease in pool size of labile organic matter and microbial biomass at elevated temperature whereas the amount of refractory organic matter increased. Temperature averaged microbial C/N ratio was 14.7 in the LF layer suggesting a fungi-dominated decomposer community whereas it was 7.3 in the H layer, probably due to predominance of bacteria. Respiration and microbial C were difficult to fit using the model if the microbial C/N ratio was kept constant with time. A separate ¹⁵N-enrichment study with the addition of glucose showed that glucose was metabolized faster in the LF than in the H layer. In both layers, decomposition of organic matter appeared to be limited by C availability. This revised version was published online in June 2006 with corrections to the Cover Date.     

The role of deer as vehicles to move ticks, Ixodes ricinus, between contrasting habitats

In Europe the most important hosts maintaining Ixodes ricinus tick populations are deer. Therefore, excluding deer by fencing or culling are potential tick management tools. Here we test the hypothesis that deer act as vehicles for moving ticks between two distinct habitats: forest and open heather moorland. We utilised an ideal “natural experiment” whereby forests were either fenced or unfenced to prevent or allow deer to move between habitats. We aimed to test the hypothesis that deer cause a net movement of ticks from high tick density areas, i.e. forests, to low tick density areas, i.e. open moorland. We recorded I. ricinus and host abundance in 10 unfenced and seven fenced forests and their respective surrounding heather moorland. We found that fenced forests had fewer deer and fewer I. ricinus nymphs than unfenced forests. However, we found no evidence that fencing forests reduced I. ricinus abundance on adjacent heather moorland. Thus there was insufficient evidence for our hypothesis that deer cause a net movement of ticks from forest onto adjacent moorland. However, we found that deer abundance generally correlates with I. ricinus abundance. We conclude that fencing can be used as a tool to reduce ticks and disease risk in forests, but that fencing forests is unlikely to reduce ticks or disease risk on adjacent moorland. Instead, reducing deer numbers could be a potential tool to reduce tick abundance with implications for disease mitigation.     

Seasonal quality of forages used by moose in the aspen-dominated boreal forest, central Alberta

Forages used by moose, Alces alces , in the aspen-dominated boreal forest were studied to determine seasonal changes in digestibility (nylon bag technique) and chemical composition. Digestibility of all forage classes increased to 70% during spring and summer with the presence of new growth and declined to a low of 30% with plant maturation and dormancy. Mean protein contents during these periods were >20% and <7%, respectively. Nutritional quality of herbaceous forages peaked earlier and higher than that of woody plants in spring but quality declined earlier and reached slightly lower levels in late winter. Cell wall composition of grasses, sedge, and foliage varied seasonally and was correlated with forage digestibility. In multiple linear regression models, hemicellulose, cellulose, and lignin content of browse, grass, and sedge provided significant predictions of digestibility.     

The forest of Vorsø, Denmark: Succession towards a natural, decidous boreal forest influenced by breeding cormorants

The forest on the strictly protected island Vorsø in Horsens Fjord has since 1952 been examined every ten years to discover the number, basal area, wood volume and aboveground biomass of the species. This paper describes the results from 1982 and the development up to that. The dominating species are Fraxinus excelsior, Ulmus glabra and Fagus sylvatica. The two forests, "Vesterskov" (6.09 ha) and "Østerskov" (2.48 ha) respectively, were, in 1982, still immature. Their number of stems per ha were: 756 and 509; basal area: 38 m² and 45 m². volume: 544 m³ and 615 m³; biomass 207 t and 268 t. The annual increase 1972–1982 was respectively 8.8 m³/ha and 0.3 m³/ha. The impact of the cormorant ( Phalacrocorax carbo sinensis ) is especially in "Østerskov" increasing, since the colony here was established in 1976. The succession of the forest is discussed in relation to the disturbance by the cormorants.     

Changes in the forest floor of Canadian southern boreal forest after disturbance

Abstract. The concentrations and contents of organic matter and nutrients in organic deposits on the forest floor were estimated along a 231-yr chronosequence following fire at the southern limit of the boreal forest in eastern Canada. The sampling design was stratified to take into account the variability related to the presence of the principal tree species as well as to the presence of large gaps created by a recent spruce budworm (Choristoneura fumiferana) outbreak. The forest floor showed a steady accumulation of organic matter and total nutrients with time-since-fire and a 50 % decrease in the concentrations of available P and K, but not N (as determined by aerobic incubation). The increase in forest-floor weight was accompanied by an increased storage of available N, Ca and Mg. The availability of N and Ca was more strongly affected by tree species and gaps than by time-since-fire. A high N-availability was observed under Betula papyrifera and in gaps, while high a Ca-availability was found near Populus tremuloides and Thuja occidentalis. In old sites, the forest floor of gaps, created by a recent spruce budworm outbreak, had a necromass similar to that of a young forest, but the low concentrations of available P and K of an old forest.     

Role of svp in Drosophila Pericardial Cell Growth

The Drosophila dorsal vessel is a segmentally repeated linear organ, in which seven-up (svp) is expressed in two pairs of cardioblasts and two pairs of pericardial cells in each segment. Under the control of hedgehog (hh) signaling from the dorsal ectoderm, svp participates in diversifying cardioblast identities within each segment. In this experiment, the homozygous embryos of svp mutants exhibited an increase in cell size of Eve positive pericardial cells (EPCs) and a disarranged expression pattern, while the cardioblasts pattern of svp-lacZ expression was normal. In the meantime, the DA1 muscle founders were absent in some segments in svp mutant embryos, and the dorsal somatic muscle patterning was also severely damaged in the late stage mutant embryos, suggesting that svp is required for the differentiation of Eve-positive pericardial cells and DA1 muscle founders and may have a role in EPC cell growth.