Australis Litter Research Articles

Functional composition of initial soil fungi explains the difference in mass loss of Phragmites australis litter in different habitat conditions across multiple coastal wetlands

The differences in mass loss of leaf litter are primarily thought to be driven by microbial activity, especially by fungi. However, the existence of such differences across large spatial scales has not been well explored in field studies and the underlying mechanisms of difference are still unclear, especially for the role of different fungal guilds in driving different mass losses. We conducted a 1-year decomposition study within each of four coastal wetlands in China to test the difference in mass loss across a large spatial scale (ranging from 26° N to 41° N in latitude). In each wetland, six sites including three composed of P. australis and three composed of another dominant plant species typically in coastal ecosystems were selected. We used P. australis leaf litter as the standard decomposition material, placing it into litter bags with mesh sizes 1 mm and 4 mm, respectively. Final litter mass loss was examined approximately after 3, 9 and 12 months. The different mass loss was quantified using additional mass loss at P. australis sites compared to that at another species sites. We found that the mass loss of leaf litter of P. australis showed a clear difference across multiple coastal wetlands only at later stages of decomposition, which was independent of mesofauna (mesh size) contribution to decomposition. Furthermore, the observed difference in mass loss was primarily attributed to the dissimilarities in initial soil fungal community, particularly the symbiotrophic fungi, rather than the soil bacterial community. Our results provide empirical evidence of a large-scale difference in mass loss in litter decomposition and have linked the observed difference to different soil fungal guilds. These results indicate that symbiotrophic fungi might play a direct or indirect role in driving difference in mass loss, which contributes to a better understanding and invites in-depth further investigation on the underlying microbe-driven mechanisms of the difference.

Decomposition of lignin and carbohydrates in a rewetted peatland: a comparative analysis of surface water and anaerobic soil layers

The rewetting of long-term drained peatlands leads to the development of eutrophic shallow lakes, gradually inhabited by reed communities. These shallow lakes are characterized by significant nutrient and methane emissions. To comprehend the fate of organic compounds from decaying Phragmites australis litter in water and anaerobic soil layers, we conducted a 1.6-year decomposition experiment. The experiment employed bulk and lignin-derived phenol analysis, as well as Fourier-transform infrared spectroscopy. As anticipated, the highest level of decomposition was observed in the surface water body of the shallow lake, while the non-rooted degraded peat exhibited the lowest decay. The bulk mass loss of plant litter decreased with depth from 55 to 27% across the four decomposition environments. Analysis using infrared spectroscopy indicated that the decrease in mass loss was primarily driven by the breakdown of carbohydrates, which constitute a significant portion of plant litter. Interestingly, litter in the rooted degraded peat layer exhibited the highest degree of lignin decay. Furthermore, the study revealed a preferential loss of vanillin phenols and an accumulation of p-hydroxyl phenols. These findings suggest that the increased methane emissions in rewetted fens may be partially attributed to the demethoxylation of vanillin phenols and the subsequent formation of p-hydroxyl phenols. In conclusion, this study provides valuable insights into anaerobic lignin decomposition of plant litter and sheds light on potential mechanisms underlying elevated methane emissions in rewetted peatlands. Furthermore, the study’s findings hold significant implications for both carbon cycling and sequestration within these ecosystems, thereby stimulating further research into the microbial community and its extended effects.

Metagenomics reveals effects of fluctuating water conditions on functional pathways in plant litter microbial community

Climate change modifies environmental conditions, resulting in altered precipitation patterns, moisture availability and nutrient distribution for microbial communities. Changes in water availability are projected to affect a range of ecological processes, including the decomposition of plant litter and carbon cycling. However, a detailed understanding of microbial stress response to drought/flooding is missing. In this study, an intermittent lake is taken up as a model for changes in water availability and how they affect the functional pathways in microbial communities of the decomposing Phragmites australis litter. The results show that most enriched functions in both habitats belonged to the classes of Carbohydrates and Clustering-based subsystems (terms with unknown function) from SEED subsystems classification. We confirmed that changes in water availability resulted in altered functional makeup of microbial communities. Our results indicate that microbial communities under more frequent water stress (due to fluctuating conditions) could sustain an additional metabolic cost due to the production or uptake of compatible solutes to maintain cellular osmotic balance. Nevertheless, although prolonged submergence seemed to have a negative impact on several functional traits in the fungal community, the decomposition rate was not affected.

Contribution of neutral processes to the assembly of microbial communities on Phragmites australis leaf litter


 Phragmites australis is a remarkable aquatic plant known for its adaptability, wide ecological range and extensive presence in natural wetlands. When combined with its microbiome, it holds unique potential to enhance the overall functionality of wetland ecosystems. To fully harness this potential in both natural and constructed wetlands, it becomes crucial to understand the dynamics of decomposition regarding the substantial biomass generated by P. australis. However, our understanding of the selective and neutral processes that shape the microbial communities responsible for decomposing P. australis litter remains somewhat limited. In this context, our research reveals that the majority of microbial taxa inhabiting P. australis leaves and litter follow neutral distribution patterns, indicating they are less likely to be specifically adapted to the host plant or habitat. Their presence in the community primarily results from their prevalence in the broader metacommunity and source pool. Nonetheless, this should not be interpreted as these taxa being functionally unimportant or lacking close interactions with their host. Instead, the host environment does not differentially select them, and as a consequence, their distributions are shaped predominantly by neutral processes of dispersal and drift.

The decomposition processes and return of carbon, nitrogen, and phosphorus of Phragmites australis litter with different detritus amount

The decomposition processes and return of carbon, nitrogen, and phosphorus of Phragmites australis litter with different detritus amount

Dodder parasitism limited the effect of arbuscular mycorrhizal fungi on litter decomposition

Effects from parasitism and parasitic litter input can affect the decomposition of litter, but the mechanism is unclear. We hypothesized that the decomposition of litter produced by the holoparasite Cuscuta australis is promoted more strongly by arbuscular mycorrhizal fungi (AMF) than the litter of its host Bidens pilosa and that parasitism by C. australis can indirectly suppress the ability of AMF to promote the decomposition of host B. pilosa litter. We conducted two container experiments to compare the effect of AMF on the decomposition of 15N-labelled C. australis and B. pilosa litter filled in litter bags and to test the effect of C. australis parasitism on the decomposition of B. pilosa litter by AMF. The percentage of 15N remaining, AMF hyphal density, and enzyme activity in the litter bags were measured, and the bacterial communities in the litter bags were also tested using 16S amplicon sequencing. We found that the amount of 15N that remained in the bags with C. australis litter was significantly higher than that in the bags with B. pilosa litter. AMF significantly decreased the remaining 15N and changed the bacterial community in bags with B. pilosa litter but did not significantly affect these factors in the bags with C. australis litter. The bacterial diversity, AMF hyphal density and the abundance of several genes related to the N cycle, including assimilatory nitrate reduction and anaerobic ammonium oxidation, in the bags with C. australis litter were significantly lower than those in the bags with host litter. Parasitism significantly reduced the hyphal density of AMF, increased the 15N that remained in litter bags, and decreased the abundance of several genes related to the N cycle, such as those involved in anaerobic ammonium oxidation. Our results indicate that AMF plays a key role in the parasitism and litter effects of parasitic plants on soil nutrient cycling.

Arbuscular mycorrhizal fungi promote litter decomposition and alleviate nutrient limitations of soil microbes under warming and nitrogen application

Arbuscular mycorrhizal fungi (AMF) are vital for nutrient cycling and aboveground ecosystem stability. To understand soil microbe resource limitations and AMF feedback regulation of the soil microbial biomass and litter stoichiometry under warming and nitrogen (N) application conditions, a 3-year experiment involving AMF suppression by benomyl under warming and N application conditions was conducted in the Songnen meadow, in which soil microbial nutrient limitation was measured by ecoenzymatic stoichiometry. We assessed the soil microbes and stoichiometric variables of Leymus chinensis and Phragmites australis litter under various treatment conditions. Carbon (C) and phosphorus (P) are commonly limited nutrients in soil microbial communities in the Songnen meadow ecosystem. AMF alleviated soil microbe C and P limitations by decreasing the microbial C:P ratio under warming and N application conditions and by accelerating litter decomposition, which occurred independently of warming and N application. AMF play a critical role in balancing nutrient stoichiometry and are key to maintaining microbial metabolism and nutrient cycle homeostasis. AMF can shorten the litter nutrient cycle, which is of great significance for the absorption, utilization and storage of plant nutrients in the Songnen grassland ecosystem.

Allelopathy and resource competition: the effects of Phragmites australis invasion in plant communities

BackgroundPhragmites australis, a ubiquitous wetland plant, has been considered one of the most invasive species in the world. Allelopathy appears to be one of the invasion mechanisms, however, the effects could be masked by resource competition among target plants. The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. This has been addressed via experiments conducted in both the greenhouse and laboratory by growing associated plants, Melaleuca ericifolia, Rumex conglomeratus, and model plant, Lactuca sativa at varying densities with the allelopathic plant, P. australis, its litter and leachate of P. australis litter. This study investigated the potential interacting influences of allelopathy and resource competition on plant growth–density relationships.ResultsIn greenhouse, the root exudates mediated effects showed the strongest growth inhibition of M. ericifolia at high density whereas litter mediated results revealed increased growth at medium density treatments compared to low and high density. Again, laboratory experiments related to seed germination and seedling growth of L. sativa and R. conglomeratus exhibited phytotoxicity decreased showing positive growth as plant density increased and vice versa. Overall, the differential effects were observed among experiments but maximum individual plant biomass and some other positive effects on plant traits such as root and shoot length, chlorophyll content occurred at an intermediate density. This was attributed to the sharing of the available phytotoxin among plants at high densities which is compatible to density-dependent phytotoxicity model.ConclusionsThe results demonstrated that plant–plant interference is the combined effect of allelopathy and resource competition with many other factors but this experimental design, target-neighbor mixed-culture in combination of plant grown at varying densities with varying level of phytotoxins, mono-culture, can successfully separate allelopathic effects from competition.

Is initial Si concentration determining the influence of warming and N-supply on stoichiometric changes during litter decomposition?

Global changes in temperature and nitrogen supply can influence key aspects of the global nutrient cycles, such as leaf litter decomposition and associated nutrient release. The effect of temperature and nitrogen supply on nutrient release during decomposition may be influenced by initial nutrient concentrations of the litter, which for grasses depends partly on silicon availability during plant growth. We conducted a five-month field experiment to test whether Phragmites australis litter silicon concentration alters the effect of climate warming and excess nitrogen supply on nutrient concentrations and litter mass loss during decomposition. Warming enhanced concentration of Ca, Mn and Fe in decomposed leaf litter, whereas excess N-supply increased the concentration of Fe and Ca in leaves. Initial Si concentrations of leaf litter influenced the stoichiometric ratios of the elements (in relation to P), and element:P ratios mostly increased for litter with intermediate and high Si concentrations, but patterns were less clear when initial litter Si concentrations were low. We show that grass litter decomposition was most strongly associated with litter Si:P, whereas C:N and N:P ratios were less important. Our results provide first evidence that global warming, enhanced N supply and changes in Si availability affect element cycling during litter decomposition.

Decomposition and Carbon and Nitrogen Dynamics of Phragmites australis Litter as Affected by Flooding Periods in Coastal Wetlands

To investigate the effects of flooding periods on decomposition and carbon and nitrogen return of Phragmites australis litter, we examined the dynamic of P. australis litter decomposition in short‐, medium‐, and long‐flooding coastal wetlands (HN, HS, and LL wetlands, respectively) in the Yellow River Delta, China. Our results showed that the percentage of dry weight loss of P. australis litter increased gradually as the decomposition proceeded and the percentage of dry weight loss was highest in LL wetland, followed by HS wetland, while the percentage of dry weight loss was lowest in HN wetland. Similar to the percentage of dry weight loss, the relative return indices (RRIs) of carbon of P. australis litter also increased with the increasing days of decomposition, following the order LL wetland > HS wetland > HN wetland. With the exception of little accumulation in both HS and HN wetlands in a certain period, the RRIs of nitrogen increased generally with increasing days of decomposition. However, the C/N ratios decreased rapidly in the first 40 days and retained steady after 40 days.

Decomposition of Phragmites australis litter retarded by invasive Solidago canadensis in mixtures: an antagonistic non-additive effect.

Solidago canadensis is an aggressive invader in China. Solidago invasion success is partially attributed to allelopathic compounds release and more benefits from AM fungi, which potentially makes the properties of Solidago litter different from co-occurring natives. These properties may comprehensively affect litter decomposition of co-occurring natives. We conducted a field experiment to examine litter mixing effects in a Phragmites australis dominated community invaded by Solidago in southeast China. Solidago had more rapid mass and N loss rate than Phragmites when they decomposed separately. Litter mixing decreased N loss rate in Phragmites litter and increased that of Solidago. Large decreases in Phragmites mass loss and smaller increases in Solidago mass loss caused negative non-additive effect. Solidago litter extracts reduced soil C decomposition and N processes, suggested an inhibitory effect of Solidago secondary compounds. These results are consistent with the idea that nutrient transfer and secondary compounds both affected litter mixtures decomposition.

Decomposition dynamics of Phragmites australis litter in Lake Burullus, Egypt

AbstractThis study estimated the decomposition rate and nutrient dynamics of Phragmites australis litter in Lake Burullus (Egypt) and investigated the amount of nutrients released back into the water after the decomposition of the dead tissues. Phragmites australis detritus decomposition was studied from April to September 2003 utilizing the leaf, stem, and rhizome litterbags technique with coarse mesh (5 mm) bags on five sampling dates and with nine replicate packs per sample. All samples were dried, weighed and analyzed for N, P, Ca, Mg, Na, and K concentrations. The exponential breakdown rate of leaves (−0.0117/day) was significantly higher than that of rhizomes (−0.0040/day) and stems (−0.0036/day). N, Na and K mineralization were the highest from leaf litter, followed by rhizomes and stems, while P, Ca and Mg mineralization were the highest from rhizomes, followed by leaves and stems. The dead shoot biomass at the end of 2003 amounted to 4550 g DM/m2 which enters the decomposition process. By using the decay rate of 0.0117 and 0.0036/day for the leaves and stems, 3487 g DM/m2 is decomposed in a year, leaving only 1063 g DM/m2 after 1 year. This is mainly equivalent to releasing the following nutrients into surrounding water (in g/m2): 24.4 N, 1.1 P, 15.5 Ca, 3.5 Mg, 11.3 Na and 16.7 K. In conclusion, the present study indicates a significant difference in relation to the type of litter; these breakdown rates were generally greater than most rates reported in previous studies that used the same technique and mesh size.

闽江河口湿地植物枯落物立枯和倒伏分解主要元素动态

PDF HTML阅读 XML下载 导出引用 引用提醒 闽江河口湿地植物枯落物立枯和倒伏分解主要元素动态 DOI: 10.5846/stxb201105200662 作者: 作者单位: 福建师范大学地理研究所，福建师范大学地理科学学院,福建师范大学地理科学学院,福州 湿润亚热带生态地理过程省部共建教育部重点实验室,福建师范大学地理科学学院,福建师范大学地理科学学院,福建师范大学地理科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31000262, 41071148); 福建省科技厅重点项目(2010Y0019); 国家海洋局海洋公益性行业科研专项(200905009-2) Nutrient dynamics of the litters during standing and sediment surface decay in the Min River estuarine marsh Author: Affiliation: Fujian Province and Education of Ministry’s Key Laboratory of Humid Sub-tropical Eco-geographical Process,Fujian Key Laboratory of Subtropical Resources and Environment,Institute of Geography,School of Geographical Sciences,Fujian Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用分解袋法,对闽江河口湿地2种挺水植物——芦苇(Phragmites australis)和互花米草(Spartina alterniflora)花和叶枯落物的立枯和倒伏分解过程及C、N、P元素动态进行研究。结果表明:(1)立枯分解是2种湿地盐沼植物重要的分解阶段,干物质损失率在13.26%-31.89%之间。多项式模型能较好描述2种植物花和叶的枯落物分解残留率动态。(2)立枯分解阶段,芦苇花和叶的C含量主要为波动下降,互花米草较为稳定;倒伏阶段后期,2种植物都以升高为主。立枯分解阶段2种植物枯落物N含量略有下降,而倒伏阶段逐渐上升。分解过程中枯落物P含量的波动较大。(3)2种植物花和叶C、N的NAI值在分解过程中<100%。芦苇的花和叶中P的NAI值在立枯和倒伏分解阶段都经历了明显下降和升高的过程,而互花米草在立枯阶段变化不大,倒伏阶段下降较为明显。(4)与芦苇相比,互花米草的花和叶枯落物C库较高,N库较低,P库差异不大。 Abstract:The above-ground litter component in wetland ecosystems is an important carbon and nutrient store, and the rate of its decomposition influences both wetland productivity and those processes that contribute to biogeochemical cycling. This paper examined the decomposition and nutrient dynamics of the leaf and flower litter produced by two contrasting emergent macrophytes in the Min River estuary of southeast China; Spartina alterniflora is an invasive species and Phragmites australis a native one. The results demonstrated that: (1) Decomposition of standing litter within the vegetation was an important stage in the decomposition process with a loss of dry mass between 13%-15% in P. australis and 21%-32% in S. alterniflora. At day 210, the loss rate of dry mass in P. australis and S. alterniflora was accounting about 64%-67% and 59%-66%, respectively. There was no significant difference in litter mass loss between S. alterniflora and P. australis. (2) In the first 90 days of decomposition, carbon (C) concentration of P. australis litter reduced in a fluctuating pattern whereas S. alterniflora was relatively stable. However, in the later decay at the sediment surface (after 180 days), the C concentration in both species increased. At day 210, the C concentration of the flower litter in S. alterniflora and P. australis had regained their initial values and leaf litter concentrations were 107% and 106% respectively. The variation in litter nitrogen (N) concentrations of the two species showed the same pattern with a slow decrease during the standing stage, and an increase during the days of decay at the sediment surface. At day 210, the N concentration of the flower litter in S. alterniflora and P. australis was 125% and 254% of their initial values and leaf litter was 191% and 185%, respectively. However, average phosphorus (P) concentration varied distinctly between the two species: there was a quick decrease in P concentration for P. australis in the first 15 days of decomposition to 14% and 12% for flowers and leaves, whereas S. alterniflora was relatively stable in the first 90 days of decomposition. The P concentration in the two plants declined first and then rose in the sediment surface decay. The P concentration of leaf litter in S. alterniflora was significantly greater than that of P. australis during decomposition, on the contrary, the flower litter of S. alterniflora was significantly lower than that of P. australis. (3) The element accumulation index (NAI) values of C and N of the two plants were less than 100%, which indicated a release of C and N in both species. NAI values of P in P. australis decreased first, and then increased both in standing and sediment surface decay. There was no distinct fluctuation of S. alterniflora during standing decomposition, whereas there was a drop in the days of decay at the sediment surface. (4) The litter C concentration of S. alterniflora was significantly greater than that of P. australis, but the N concentration of flower litter in S. alterniflora was significantly lower than that of P. australis. Where the invasive S. alterniflora was present in the Min River estuary the carbon pool of leaf and flower litter was greater compared to where P. australis was present but the nitrogen pool was lower, and the phosphorus pool showed no obvious difference. 参考文献 相似文献 引证文献

Relationship between water regime and hummock-building by Melaleuca ericifolia and Phragmites australis in a brackish wetland

We investigated the relationship between hummock height and depth of inundation in a permanently inundated wetland in south-eastern Australia. Our survey of 318 hummocks, in water ranging from 0 to 70 cm depth, revealed a significant positive linear relationship and strong correlation between hummock height and water depth ( r 2 = 0.53 and 0.79 for Melaleuca ericifolia and Phragmites australis hummocks respectively). We also investigated whether water regime affects the decomposition rate of litter on hummocks; specifically, whether constant inundation slows decomposition to an extent that would promote accumulation of litter and hummock-building. On the contrary, we found that constantly submerged M. ericifolia litter decomposed faster than dry litter, but at a similar rate to litter that experienced intermittent inundation (decay rates ( k) 0.0015 d −1, 0.0010 d −1 and 0.0008 d −1 for submerged, intermittent and dry treatments respectively). Submerged P. australis litter also decomposed faster ( k = 0.0024 d −1) than dry litter ( k = 0.0011 d −1). We discuss the interaction of water regime and decomposition of organic material and implications for the maintenance of hummock and hollow topography.

Environmental factors affecting Phragmites australis litter decomposition in Mediterranean and Black Sea transitional waters

1. Leaf litter decomposition rates in aquatic ecosystems are known to be related to many abiotic and biotic factors. 2. Field experiments were carried out during spring 2005 in 16 ecosystems, each with four sampling sites, using the litter bag technique to investigate the influence of abiotic factors on patterns of reed litter breakdown in different physiographic, hydrological and physico-chemical gradients occurring in transitional water ecosystems in the Eastern Mediterranean and Black Sea. 3. Significant differences in leaf litter decomposition were observed among the studied ecosystems along univariate gradients of tidal range, water temperature, salinity and sinuosity index. 4. Overall, 71% of variance in the litter breakdown rate was explained by the hydrological, physico-chemical and physiographic components. Specifically, tidal range, salinity and sinuosity index are among the key factors in the most commonly used typological schemes for classifying transitional water ecosystems (i.e. Confinement Concept and Venice System), due to their influence on abundance and distribution of benthic macroinvertebrates and other guilds. 5. The patterns observed at the regional scale of the study suggest that certain key abiotic factors are likely to play a major role as drivers of plant detritus decomposition processes, through their influence on the overall metabolism of microorganisms and benthic macroinvertebrates. 6. These observations have implications for the identification of reference conditions for transitional water ecosystems in the studied area, on which all processes of classification and conservation of their ecological status are based.

Exotic plant influences soil nematode communities through litter input

The impact of exotic plant invasions on soil communities and nutrient cycling processes has received an increasing attention in recent years. To test whether the exotic plant invasions affect nematode communities through altering litter quality, we compared mass loss and nematode colonization during the stem litter decomposition of invasive Spartina alterniflora and native Phragmites australis in salt marshes of the Yangtze River estuary, China. Plastic drinking straws were synchronously used as controls. The addition of plant residues was found stimulating the growth of nematodes, particularly bacterial feeders on day 16 after burial. A top–down control of bacterivous nematodes by carnivores existed in nematode succession during the litter decomposition. With higher nitrogen content and lower C:N ratio, stem litter of the invasive S. alterniflora decayed faster and supported more abundant nematodes than the native P. australis. The greater nematode abundance in S. alterniflora was mainly due to two dominant genera of bacterial nematodes, namely Diplolaimelloides and Diplolaimella. Lower values of maturity index and structure index in S. alterniflora than in P. australis litter indicate that a more degraded food web condition resulted from the faster litter decay. A considerable difference in nematode community structures between two litter types only occurred in a certain period of the decomposition (from 8 to 32 days after burial), suggesting that the changes in faunal community structure are time dependent. In summary, this study confirmed the hypothesis that the invasion of S. alterniflora stimulates the growth of bacterial nematodes by producing higher quality of litter than the native P. australis. The results obtained here suggest that the invasion of exotic plant is likely to alter ecosystem functions indirectly through exerting its effect on soil decomposer communities such as nematodes.

Decomposition of Phragmites australis litter in seasonally flooded and exposed areas of a managed reedbed

Most studies on the decomposition of Phragmites australis have concentrated on permanently submerged or standing litter. The present study examines the dynamics of leaf and stem litter breakdown in seasonally flooded and permanently exposed areas in a managed reedbed. Seasonal flooding and summer drawdown are employed as part of the management to prevent litter accumulation. Fine mesh (0.25 mm) and modified design, coarse mesh (5-mm) bags were used. In the permanently exposed area, leaf and stem material lost 42% of their dry weight after 18 months and 47% after 30 months. In the seasonally flooded area, depending on mesh size, leaf material lost 74–79% and stem material 60–79% of its dry weight over the same time periods. Examination of individual breakdown rates demonstrated that fastest weight losses occurred following summer drawdown, with well-oxygenated, warm, damp litter. Drying of the litter and re-flooding of the reedbed led to slowing or complete cessation of breakdown. Maintenance of damp conditions throughout the summer exposure period would maximize breakdown rates.

NET IMPACT OF A PLANT INVASION ON NITROGEN-CYCLING PROCESSES WITHIN A BRACKISH TIDAL MARSH

Using comparative analysis of the rates of key processes, we have documented the net effect of a shift in plant species composition on nitrogen cycles with the example of the rapid expansion of Phragmites australis (common reed) and its replacement of short grasses (e.g., Spartina patens) in coastal marshes of the eastern United States. In this study, we measured nitrogen (N) uptake by marsh plants, N adsorption from the water column by litter, changes in N content of litter, sediment N mineralization, nitrification, and nitrate consumption in adjacent plots dominated either by P. australis or by historically dominant S. patens. Rates of individual processes were generally greater in P. australis than in S. patens, but the magnitude of difference varied greatly among processes. Seasonal measurements of standing stock nitrogen in plant tissue indicate that P. australis took up ∼60% more N than did S. patens, and annual rates of N immobilization were nearly 300% greater in P. australis litter than in S. pat...

The contribution of Phragmites australis litter to methane (CH4) emission in planted and non-planted fen microcosms

The contribution of Phragmites australis (Cav.) Trin. ex Steud. (common reed) litter as an origin of CH4-C was studied in a microcosm experiment. 14C-labelled, dried and ground P. australis root and shoot litter was buried in waterlogged, planted or non-planted fen microcosms. The evolution of 14CO2 and 14CH4 from the pots was monitored during the 35-day experiment. The 14C activity in the shoots and roots of the plants, soil, and inundation water was also analysed at the end of the experiment. Up to 40% of the released CH4-C originated from the added litter, whereas the rest originated from old soil organic matter. The comparison of planted and non-planted pots suggested that the contribution of recent plant-derived C (i.e. root exudates) to CH4 emission was negligible. The proportion of litter-derived CH4-C was significantly higher in the planted pots, suggesting that the presence of plants enhanced the formation of CH4 from litter. The major part of the initial 14C activity was recovered from the soil. About 3% was recovered from the inundation water, about 10% was emitted as CO2, and only <0.01% as CH4. However, these results demonstrated that plant litter and old soil organic matter are the major sources of CH4-C in fens during the early growth stage of P. australis.

Is the invasion of the common reed, Phragmites australis, into tidal marshes of the eastern US an ecological disaster?

Studies of effects of the invasive brackish marsh plant Phragmites australis (common reed) on estuarine biota are reviewed. With few exceptions, most field studies indicate that these P. australis-dominated marshes have diverse and abundant benthic biota, and are utilized by nekton, comparable to Spartina alterniflora marshes. However, larval mummichogs, Fundulus heteroclitus, appear to be reduced in P. australis marshes compared with S. alterniflora marshes. Small epifauna living on plant stems also appear to be denser on S. alterniflora than P. australis stems. Other studies indicate that the detritus produced by decaying P. australis litter provides food value comparable to that of S. alterniflora and that its production enters estuarine food webs. Therefore, the general assumption that these marshes are ecologically “useless” is untrue. This information should be considered by marsh managers when making decisions about restoration projects.