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1.
Yoshikazu Shimizu 《Ecological Research》1986,1(2):185-194
Species-area relationships of flowering plants were analyzed on the habitat-islands (hummocks on a floating bog) of Mizorogaike
Pond, Japan. Three habitat units (Sphagnum cuspidatum unit,Sphagnum palustre unit, and fallen leaves unit) in which habitat conditions were homogeneous and a group of habitat-specific species occurred
were recognized on the hummocks. Six hummock types were determined according to various combinations of the three habitat
units. The most fundamental species-area relationships in which size itself affects the number of species were shown by hummocks
with only one habitat unit. The species-area relationships for hummocks with two or three habitat units included the effects
of habitat diversity in addition to size. The speciesarea curve for all hummocks was an average of these relationships. It
is concluded that area in species-area relationships affects species numbers in two ways: number of habitat units and size
of each habitat unit. 相似文献
2.
The goal of this study is to examine the suitability of three plants, Typha spp., Phragmites spp. and Iris pseudacorus, in a free-water surface constructed wetland created to treat eutrophic water from Lake Albufera (Valencia, Spain), a wetland of international importance. The growth, coverage and nutrient content of the three plants were studied, and chemical analyses were performed according to standard methods. The maximum standing crops measured for each plant were 1.9, 18.2 and 3.3 kg m?2, respectively, and their average nutrient concentrations were 2.1, 1.2 and 1.7 g P kg?1 and 12.1, 11.7 and 10.1 g N kg?1, respectively. A multiple harvest of Iris pseudacorus revealed that the removal of nutrients could be increased up to 50% for N and 100% for P compared with a single harvest. Biomass decomposition assays showed high values for five-day biochemical oxygen demand (115–207 mg O2 g?1, depending on the plant and its age) and a substantial release of phosphorus, up to 100% of that contained in the biomass, highlighting the need to remove the litter fall. This study provides key aspects for vegetation selection and management (planting and harvesting) in a novel application of constructed wetlands to enhance water quality and biodiversity. 相似文献
3.
Above- and belowground dynamics of plant community succession following abandonment of farmland on the Loess Plateau, China 总被引:3,自引:0,他引:3
Aboveground and belowground changes during vegetation restoration and vegetation successions need to be characterized in relation to their individual responses to changes in soil resources. We examined above- and belowground vegetation characteristics, soil moisture, and nutrient status at the end of the growing season in 2006 in plots with vegetation succession ages of 2, 4, 6, and 8 years (two replicates each) that had been established on abandoned cropland, where potatoes had been grown for 3 years, using hoe and plow cultivation, immediately prior to vegetation clearance and subsequent natural plant colonization. A plant community comprising pioneer species [e.g., Artemisia capillaries, (subshrub)] was characterized by low levels of species richness (7.5?±?1.4 species m?2), plant density (35.7?±?4.2 stems m?2), fine root length density (940.1?±?90.1 m m?2), and root area density (2.3?±?0.3 m2 m?2) that increased rapidly with time. Aboveground and belowground characteristics of both A. capillaries and the later successional species, Stipa bungeana (C3 perennial grass), increased in the first 6 years, but in the following 2 years A. capillaries declined while S. bungeana thrived. Thus, the fine root length density of A. capillaries, 812.4 m m?2 after 2 years, changed by a factor of 1.7, 2.0, and 0.4 in the 4th, 6th, and 8th years, whereas that of S. bungeana changed from 278.4 m m?2, after 4 years, and by 1.7 and 23.3 times in the 6th and 8th years, respectively. Secondary vegetation succession resulted in reduced soil moisture contents. Soil available P and N mainly influenced aboveground characteristics, while soil moisture mainly influenced belowground characteristics. However, soil moisture had no significant affect on S. bungeana belowground characteristics at the population level in this semiarid region. 相似文献
4.
Effects of aquatic vegetation type on denitrification 总被引:1,自引:0,他引:1
Annelies J. Veraart Wilco J. J. de Bruijne Jeroen J. M. de Klein Edwin T. H. M. Peeters Marten Scheffer 《Biogeochemistry》2011,104(1-3):267-274
In a microcosm 15N enrichment experiment we tested the effect of floating vegetation (Lemna sp.) and submerged vegetation (Elodea nuttallii) on denitrification rates, and compared it to systems without macrophytes. Oxygen concentration, and thus photosynthesis, plays an important role in regulating denitrification rates and therefore the experiments were performed under dark as well as under light conditions. Denitrification rates differed widely between treatments, ranging from 2.8 to 20.9 ??mol N m?2 h?1, and were strongly affected by the type of macrophytes present. These differences may be explained by the effects of macrophytes on oxygen conditions. Highest denitrification rates were observed under a closed mat of floating macrophytes where oxygen concentrations were low. In the light, denitrification was inhibited by oxygen from photosynthesis by submerged macrophytes, and by benthic algae in the systems without macrophytes. However, in microcosms with floating vegetation there was no effect of light, as the closed mat of floating plants caused permanently dark conditions in the water column. Nitrate removal was dominated by plant uptake rather than denitrification, and did not differ between systems with submerged or floating plants. 相似文献
5.
Kerry J. Dinsmore Ute M. Skiba Michael F. Billett Robert M. Rees 《Plant and Soil》2009,318(1-2):229-242
Peatland landscapes typically exhibit large variations in greenhouse gas (GHG) emissions due to microtopographic and vegetation heterogeneity. As many peatland budgets are extrapolated from small-scale chamber measurements it is important to both quantify and understand the processes underlying this spatial variability. Here we carried out a mesocosm study which allowed a comparison to be made between different microtopographic features and vegetation communities, in response to conditions of both static and changing water table. Three mesocosm types (hummocks?+?Juncus effusus, hummocks?+?Eriophorum vaginatum, and hollows dominated by moss) were subjected to two water table treatments (0–5 cm and 30–35 cm depth). Measurements were made of soil-atmosphere GHG exchange, GHG concentration within the peat profile and soil water solute concentrations. After 14 weeks the high water table group was drained and the low water table group flooded. Measurement intensity was then increased to examine the immediate response to change in water table position. Mean CO2, CH4 and N2O exchange across all chambers was 39.8 μg m?2 s?1, 54.7 μg m?2 h?1 and ?2.9 μg m?2 h?1, respectively. Hence the GHG budget was dominated in this case by CO2 exchange. CO2 and N2O emissions were highest in the low water table treatment group; CH4 emissions were highest in the saturated mesocosms. We observed a strong interaction between mesocosm type and water table for CH4 emissions. In contrast to many previous studies, we found that the presence of aerenchyma-containing vegetation reduced CH4 emissions. A significant pulse in both CH4 and N2O emissions occurred within 1–2 days of switching the water table treatments. This pulsing could potentially lead to significant underestimation of landscape annual GHG budgets when widely spaced chamber measurements are upscaled. 相似文献
6.
J. Greet 《Wetlands Ecology and Management》2016,24(5):565-577
Soil seed banks can play an important role in the regeneration of wetland vegetation. However, their potential role in the restoration of degraded wetland forests is less certain. I surveyed the soil seed bank and extant floras of four sites across a eucalypt wetland forest of variable vegetation condition. At each site, the extant vegetation was surveyed within two 5 × 5 m2 quadrats, each from which five composite soil seed bank samples were collected. Across the four sites, 57 (including 18 exotic) species were identified in the extant vegetation, while from the seed bank samples 6379 seedlings emerged from 80 taxa, 33 of which were exotic species. The soil seed bank was dominated by native and exotic monocots, and contained very few seeds of wetland tree or shrub species. Overall, the similarity between the extant and seed bank floras was very low (~24 %). Soil seed banks are likely to be of limited use in the restoration of degraded wetland forests, because the dominant species in such systems—woody and clonal plants—are typically absent from the soil seed bank. Wetland soil seed banks may contribute to the maintenance and diversity of understorey vegetation, however, they may also act as a source of exotic plant invasions, particularly when a wetland is degraded. 相似文献
7.
Macrozoobenthic communities within and outside of the drift algal mats were compared in Kõiguste Bay, NE Baltic Sea. The patches of the drift algae were on average 0.5–1 km wide in diameter covering about 25% of the total bottom area of the bay. Thickness of the mat did not exceed 6 cm. The biomass of the mat varied between 35 and 1391 g dw m?2. The drift algal mats had no clear negative effect on macrozoobenthos except for a few infaunal species. The drift algae favoured several detrivorous, herbivorous and carnivorous species. Among the studied variables, the thickness of algal mat and oxygen concentration at near-bottom layer explained the best the structure of macrozoobenthos. Total number of invertebrate species increased curvilinearly with the thickness of algal mat having the peak value at 3–5 cm thick algal mat. To conclude, moderate drift algal mats increased habitat complexity and, thus, the diversity of benthic faunal assemblages in otherwise poorly vegetated coastal areas. 相似文献
8.
The Ria Formosa is a meso-tidal coastal lagoon experiencing enhanced nutrient concentrations. Assessment of sediment–seawater interaction is essential if nutrient dynamics and the risk of eutrophication are to be fully understood. Pore water concentrations of dissolved inorganic and organic phosphorus, ammonium, nitrate and nitrite were determined in cores from six sites. Changes in nutrients concentrations were measured in intertidal pools on sand and mud between tides. Dissolved inorganic phosphorus (DIP) concentrations (~200 μmol l−1) and effluxes (123 ± 14 μmol m−2 h−1) were greater from sand than mud (37 ± 10 μmol m−2 h−1), possibly due to the binding of P with the <63 μm fraction. NH4+ effluxes were high outside the Anc?o Basin (821 ± 106 μmol m−2 h−1) and were associated with Enteromorpha sp. mats. The greatest NO3− efflux was from sediments near a salt marsh (170 ± 67 μmol m−2 h−1). These sediment fluxes of P were not sufficient to account for elevated P concentrations seen by other workers on the ebb tide from the Anc?o Basin. Intertidal pools were sinks for Dissolved Inorganic Nitrogen (DIN) and DIP over the 6 h exposure period. Thus, tidepools may be an important route of nutrients into sediments that enhances the effects of sediments on seawater nutrient concentrations. 相似文献
9.
Stephen C. Nold Michael J. Bellecourt Scott T. Kendall Steven A. Ruberg T. Garrison Sanders J. Val Klump Bopaiah A. Biddanda 《Biogeochemistry》2013,115(1-3):235-250
Lake Huron’s submerged sinkhole habitats are impacted by high-conductivity groundwater that allows photosynthetic cyanobacterial mats to form over thick, carbon-rich sediments. To better understand nutrient cycling in these habitats, we measured the stable isotopic content of carbon and nitrogen in organic and inorganic carbon pools in Middle Island sinkhole, a ~23 m deep feature influenced by both groundwater and overlying lake water. Two distinct sources of dissolved CO2 (DIC) were available to primary producers. Lake water DIC (δ 13C = ?0.1 ‰) differed by +5.9 ‰ from groundwater DIC (δ 13C = ?6.0 ‰). Organic carbon fixed by primary producers reflected the two DIC sources. Phytoplankton utilizing lake water DIC were more enriched in 13C (δ 13C = ?22.2 to ?23.2 ‰) than mat cyanobacteria utilizing groundwater DIC (δ 13C = ?26.3 to ?30.0 ‰). Sinkhole sediments displayed an isotopic signature (δ 13C = ?23.1 ‰) more similar to sedimenting phytoplankton than the cyanobacterial mat. Corroborated by sediment C/N ratios, these data suggest that the carbon deposited in sinkhole sediments originates primarily from planktonic rather than benthic sources. 210Pb/137Cs radiodating suggests rapid sediment accumulation and sub-bottom imaging indicated a massive deposit of organic carbon beneath the sediment surface. We conclude that submerged sinkholes may therefore act as nutrient sinks within the larger lake ecosystem. 相似文献
10.
Sohair I. Abou-Elela Mohamed A. Elekhnawy Magdy T. Khalil Mohamed S. Hellal 《International journal of phytoremediation》2017,19(11):1023-1028
The effect of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a pilot scale subsurface horizontal flow constructed treatment wetland (HFCTW) vegetated with Cyprus papyrus was investigated. Different HLRs were applied to the treatment system namely 0.18, 0.10, and 0.07 m3/m2. d with corresponding HRTs of 1.8, 3.2, and 4.7 days, respectively. The flow rate was 8 m3/d, and the average organic loading rate (OLR) was 0.037 kg BOD/m3/d. Results showed that the performance of the HFCTW was linearly affected by decreasing the HLR and increasing the HRT. The highest treatment efficiency was achieved at HRT (4.7 days) and HLR (0.07 m3/m2. d). The percentage reductions of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) were 86%, 87%, and 80%, respectively. Satisfactory nutrient removal was obtained. Also, removal of 2–3 logs of bacterial indicators of pollution was achieved. The dry biomass of Cyperus was 7.7 kg/m2 and proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area. 相似文献
11.
The effects of water availability on root growth and morphology in an Amazon rainforest 总被引:2,自引:0,他引:2
Daniel B. Metcalfe Patrick Meir Luiz Eduardo O. C. Aragão Antonio C. L. da Costa Alan P. Braga Paulo H. L. Gonçalves Joao de Athaydes Silva Junior Samuel S. de Almeida Lorna A. Dawson Yadvinder Malhi Mathew Williams 《Plant and Soil》2008,311(1-2):189-199
This study examined how root growth and morphology were affected by variation in soil moisture at four Amazon rainforest sites with contrasting vegetation and soil types. Mean annual site root mass, length and surface area growth ranged between 3–7 t ha?1, 2–4 km m?2 and 8–12 m2 m?2 respectively. Mean site specific root length and surface area varied between 8–10 km kg?1 and 24–34 m2 kg?1. Growth of root mass, length and surface area was lower when soil water was depleted (P?<?0.001) while specific root length and surface area showed the opposite pattern (P?<?0.001). These results indicate that changes in root length and surface area per unit mass, and pulses in root growth to exploit transient periods of high soil water availability may be important means for trees in this ecosystem to increase nutrient and water uptake under seasonal and longer-term drought conditions. 相似文献
12.
P. W. Inglett E. M. D’Angelo K. R. Reddy P. V. McCormick S. E. Hagerthey 《Wetlands Ecology and Management》2009,17(2):131-144
The use of periphyton nitrogenase activity (biological N2 fixation) as an indicator of wetland P impact was assessed using patterns of nutrient content (C, N, P, Ca, Mg, K, Fe, and
Mn) and acetylene reduction (AR) in floating cyanobacterial periphyton mat (metaphyton) communities of a P-enriched portion
of the Florida Everglades, USA (Water Conservation Area-2A, WCA-2A). Spatial patterns of nutrients indicate the enrichment
of floating mat periphyton N, P, Fe, and K, and the reduction of Mn and TN:TP in enriched marsh areas. In highly enriched
areas, floating mat periphyton AR was approximately threefold greater than that in less enriched, interior marsh zones. Multiple
regression models indicated AR dependence on P in eutrophic WCA-2A areas while the AR of more interior marsh periphyton mats
was more closely related to tissue levels of Ca and Fe. Nitrogenase activity of floating mat periphyton from P-loaded mesocosms
revealed a significant enhancement of N2 fixation in samples receiving approximately 2–3 mg P m−2 of cumulative P dosing or with biomass TP content of 100–300 mg kg−1. At P contents above the optimum, mat periphyton AR was suppressed possibly as a result of changes in species composition
or increased levels of NH4+. After 3 years of dosing, consistently high AR occurred only at low rates of P enrichment (0.4–0.8 g P m−2 yr−1), and the patterns appeared to be seasonal. These findings agree with the hypothesis that P availability is a key determinant
of nitrogenase activity in aquatic systems, and thus, may support the use of periphyton nitrogenase to indicate P impacts
in P-limited systems. These results also demonstrate the potential existence of a P threshhold for biogeochemical alteration
of periphyton mat function in the Everglades, and that cumulative loading of limiting nutrients (i.e., P), rather than instantaneous
concentrations, should be considered when evaluating nutrient criteria. 相似文献
13.
Invasive plants have wide-ranging impacts on native systems including reducing native plant richness and altering soil chemistry, microbes, and nutrient cycling. Increasingly, these effects are found to linger long after removal of the invader. We examined how soil chemistry, bacterial communities, and litter decomposition varied with cover of Euonymus fortunei, an invasive evergreen liana, in two central Kentucky deciduous forests. In one forest, E. fortunei invaded in the late 1990s but invasion remained patchy and we paired invaded and uninvaded plots to examine the associations between E. fortunei cover and our response variables. In the second forest, E. fortunei had completely invaded the forest by 2005; areas where it had been selectively removed by 2010 were paired with an adjacent invaded plot. Where E. fortunei had patchily invaded, E. fortunei patches had up to 3.5× nitrogen, 2.7× carbon, and 1.9× more labile glomalin in soils than uninvaded plots, whereas there were no differences in soil characteristics between invaded and removal plots. In the patchily invaded forest, bacterial community composition varied among invaded and non-invaded plots, whereas bacterial communities did not vary among invaded and removal plots. Finally, E. fortunei leaf litter decomposed faster (k = 4.91 year?1) than the native liana (k = 3.77 year?1), Vitis vulpina; decomposition of both E. fortunei and V. vulpina was faster in invaded (k = 7.10 year?1) than removal plots (k = 4.77 year?1). Our findings suggest that E. fortunei invasion increases the rate of leaf litter decomposition via high-quality litter, alters the decomposition environment, and shifts in the soil biotic communities associated with a dense mat of wintercreeper. Land managers with limited resources should target the densest mats for the greatest restoration potential and remove wintercreeper patches before they establish dense mats. 相似文献
14.
Soil carbon stocks and quality across intact and degraded alpine wetlands in Zoige,east Qinghai-Tibet Plateau 总被引:3,自引:0,他引:3
Junwei Luan Lijuan Cui Chenghua Xiang Jianghua Wu Hongtao Song Qiongfang Ma 《Wetlands Ecology and Management》2014,22(4):427-438
The wetlands on the Qinghai-Tibet Plateau are experiencing serious degradation, with more than 90,000 hectares of marshland converted to wet meadow or meadow after 40 years of drainage. However, little is known about the effects of wetland conversion on soil C stocks and the quality of soil organic carbon (SOC) (defined by the proportion of labile versus more resistant organic carbon compounds). SOC, microbial biomass carbon, light fraction organic carbon (LFOC), dissolved organic carbon, and the chemical composition of SOC in the soil surface layer (0–10 cm), were investigated along a wetland degradation gradient (marsh, wet meadow, and meadow). Wetland degradation caused a 16 % reduction in the carbon stocks from marsh (178.7 ± 15.2 kg C m?2) to wet meadow (150.6 ± 21.5 kg C m?2), and a 32 % reduction in C stocks of the 0–10 cm soil layer from marsh to meadow (122.2 ± 2.6 kg C m?2). Wetland degradation also led to a significant reduction in SOC quality, represented by the lability of the carbon pool as determined by a density fractionation method (L LFOC), and a significant increase in the stability of the carbon pool as reflected by the alkyl-C:O-alkyl-C ratio. 13C NMR spectroscopy showed that the labile form of C (O-alkyl-C) declined significantly after wetland degradation. These results assist in explaining the transformation of organic C in these plateau wetland soils and suggest that wetland degradation not only caused SOC loss, but also decreased the quality of the SOC of the surface soil. 相似文献
15.
滇西北高原纳帕海湿地湖滨带优势植物生物量及其凋落物分解 总被引:6,自引:0,他引:6
选取滇西北高原湿地纳帕海湖滨带优势植物茭草(Zizania caducifolia)、水葱(Scirpus tabernaemontani)和刘氏荸荠(Heleocharis liouana),研究其生物量及其凋落物分解特征,结果表明:水葱、茭草、刘氏荸荠为纳帕海湿地湖滨带单优植物群落,均具有较高的地上生物量,不同植物群落地上生物量不同,其中,茭草地上生物量(853.6±58.2)g·m-2·a-1显著高于水葱(730.7±7.8)g·m-2·a-1与刘氏荸荠(338.9±32.6) g·m-2·a-1的地上生物量.3种植物群落凋落物分解速率不同、并随月平均气温升高均呈增加的趋势,其中,刘氏荸荠分解速率k值最大(0.067±0.0026)、茭草(0.062±0.0072)其次、水葱最小(0.039±0.0062).凋落物经过1年的分解,水葱、茭草和刘氏荸荠凋落物存留率分别为(62.0±8.8)%、(47.5±9.0)%和(44.5±7.9)%.综合3种湖滨带植物地上生物量与凋落物年分解,水葱地上生物量年存留量(453.1±4.9)g·m-2·a-1显著高于茭草(405.4±27.7)g·m-2·a-1和刘氏荸荠(150.9±14.5) g·m-2·a-1.研究进一步表明滇西北高原湿地湖滨带植物具有极高的生物量存留率,成为该类型湿地生态系统碳汇功能的基础,其碳汇过程及其贡献率需要进一步深入研究. 相似文献
16.
Several factors can affect the integrity of natural archives such as peat records, e.g., decomposition and nutrient cycling, and it has also been hypothesized that some rapid downward transport of atmospherically derived elements may occur. We test this hypothesis by analyzing the short-lived, natural tracer beryllium-7 (t½ = 53.4 days) in five cores from two peatlands. In triplicate hummock cores from a raised bog in southern Sweden, 7Be could be measured to 20, 18 and 8 cm depth, and in a nutrient-poor mire in northern Sweden to a depth of 16 cm in a Sphagnum lawn core, but only 4 cm in the dominant, more-decomposed fen peat, indicating some spatial variability both within and between sites. Total 7Be inventories were 320–450 Bq m?2 in the bog, and 150 Bq m?2 (lawn) and 240 Bq m?2 (fen peat) in the mire. 25–79 % of the total inventory of 7Be was located in the upper 2-cm layer. To further test downwashing, in the laboratory we applied a CuBr-solution to two cores and a Cu-solution to one core taken from the mire Sphagnum lawn, all with low water table conditions. About 50 % of the added Cu and ~35 % of the added Br were retained in the surface (2 cm) layer; 1–3 % of the Cu was found at 8–12 cm depth and ~1 % of the Br was measured in the lowest level (20–22 cm). Based on our novel approach using 7Be and experimental work we show that short-term downwashing can occur in peatlands and we suggest the depth of this will depend on the properties of the peat, e.g., bulk density and decomposition, as well as hydrology. 相似文献
17.
Sarah Widney Alyce Kanabrocki Klein Jeff Ehman Courtney Hackney Christopher Craft 《Wetlands Ecology and Management》2018,26(3):265-276
Wetlands provide many valuable ecosystem functions such as sediment and nutrient retention, high biological productivity and biodiversity, flood control, and opportunities to recreate. Despite their importance, estimating the value of wetlands is difficult as the worth of these functions and services is not easily quantified. The overall objective of this study was to estimate the value of freshwater wetlands in the Saint Johns River (SJR) watershed, Florida based on their ability to remove nutrients, namely nitrogen (N) and phosphorus (P). We used a combination of literature review, geospatial analysis of land cover, and regression analysis to determine the total wetland area in the SJR watershed and the rates of nitrogen and phosphorus burial in the wetlands. We then estimated the economic value of these wetlands based on the replacement cost of nutrient removal by wastewater treatment plants. Nitrogen burial rates ranged from 27 g/m2/year to a background rate of 6.56 g/m2/year, and phosphorus burial rates range from 1.31 g/m2/year to a background of 0.11 g/m2/year. Using these rates, we calculate wetlands of the SJR catchment remove 79,873 MT of nitrogen annually just from burial in the soil, with a replacement cost of between $240 million to $150 billion per year. The amount of phosphorus buried yearly is more than 2400 MT with an annual replacement cost of $17 to $497 million. Though they are based on limited data and include a variety of watershed-scale research limitations, these findings highlight the significant potential value of conserving functional wetlands based solely on their nutrient retention functions. If we were to consider the benefits associated with other wetland functions such as flood control, biological productivity, and biodiversity in addition to their ability to retain nutrients, the value of the SJR wetlands would be even greater. 相似文献
18.
Macroalgal-mediated transfers of water column nitrogen to intertidal sediments and salt marsh plants
In many temperate estuaries, mats of opportunistic macroalgae accumulate on intertidal flats and in lower elevations of salt marshes, perhaps playing a role in linking water column nitrogen (N) supply to these benthic habitats. Using a flow-through seawater system and tidal simulator, we varied densities (equivalent to 0, 1, 2, or 3 kg m−2 wet mass) of 15N-labelled macroalgae (Enteromorpha intestinalis) on estuarine sediments in microcosms with/without pickleweed (Salicornia virginica) to assess N transfers from algae. In the 6-week experiment, macroalgal biomass increased from initial levels in the lower density treatments but all algae lost N mass, probably through both leakage and decomposition. With all densities of algae added, sediments and pickleweed became enriched in 15N. With increasing mat density, losses of algal N mass increased, resulting in stepwise increases in 15N labeling of the deeper sediments and pickleweed. While we did not detect a growth response in pickleweed with macroalgal addition during the experiment, N losses from algal mats that persist over many months and/or recur each year could be important to the mineral nutrition of N-limited marsh plants. We conclude that N dynamics of intertidal sediments and lower salt marsh vegetation are linked to the N pools of co-occurring macroalgae and that further study is needed to assess the magnitude and importance of N transfers. 相似文献
19.
A simulation model for nitrogen retention in a papyrus wetland near Lake Victoria,Uganda (East Africa) 总被引:1,自引:0,他引:1
A. A. van Dam A. Dardona P. Kelderman F. Kansiime 《Wetlands Ecology and Management》2007,15(6):469-480
Papyrus wetlands around Lake Victoria, East Africa play an important role in the nutrient flows from the catchment to the
lake. A dynamic model for nitrogen cycling was constructed to understand the processes contributing to nitrogen retention
in the wetland and to evaluate the effects of papyrus harvesting on the nitrogen absorption capacity of the wetlands. The
model had four layers: papyrus mat, water, sludge and sediment. Papyrus growth was modelled as the difference between nitrogen
uptake and loss. Nitrogen uptake was modelled with a logistic equation combined with a Monod-type nitrogen limitation. Nitrogen
compartments were papyrus plants, organic material in the floating mat; and total ammonia, nitrate and organic nitrogen in
the water, sludge and sediment. Apart from the uptake and decay rates of the papyrus, the model included sloughing and settling
of mat material into the water, mineralization of organic matter, and nitrification and diffusion of dissolved inorganic nitrogen.
Literature data and field measurements were used for parameterization. The model was calibrated with data from Kirinya wetland
in Jinja, Uganda which receives effluent from a municipal wastewater treatment plant. The model simulated realistic concentrations
of dissolved nitrogen with a stable biomass density of papyrus and predicted accumulation of organic sludge in the wetland.
Assuming that this sludge is not washed out of the wetland, the overall nitrogen retention of the wetland over a three-year
period was 21.5 g N m−2 year−1 or about 25% of input. Harvesting 10, 20 and 30% of the papyrus biomass per year increased nitrogen retention capacity of
the wetland to 32.3, 36.8 and 38.1 g m−2 year−1, respectively. Although the nutrient flows estimated by the model are within the ranges found in other papyrus wetlands,
the model could be improved with regard to the dynamics of detrital nitrogen. Actual net retention of nitrogen in the sludge
is likely to be lower than 21.5 g N m−2 year−1 because of flushing out of the sludge to the lake during the rainy season. 相似文献
20.
Chemical properties of waters and their seasonal changes were studied in Mizorogaike Pond, a system of pond and floating mat.
The following six sites including contrasting habitats and water conditions were monitored to assess nutrient dynamics in
the system: 1) a pool on the mat, 2) margin of aSphagnum cuspidatum community, 3) an artificial ‘well’ (water layer beneath the floating mat), 4) aMenyanthes trifoliata community in a hollow, and 5) & 6) two sites in the open water. On the floating mat, the water around theSphagnum community had lower pH values, while that in theM. trifoliata community had higher pH values. This difference was related to the influence of flood water, the extent of which was determined
by the microtopography. Seasonal changes in water chemistry on the mat suggested that pond water flooding the mat in late
autumn and winter is important for the nutrient supply to the mat surface vegetation in this system. Water chemistry of the
‘well’ suggested that the diffusion of inorganic nitrogen occurs from beneath the peat layer. Two types of cluster analysis
based on the mean values for chemical variables and the patterns of fluctuation in these variables were performed. The six
sites were classified into similar groups which were identified by water type (pool, hollow, well and open water) by both
types of analysis. The results showed that a common kind of perturbation should operate in determining the status of nutrient
dynamics in the various water types. 相似文献