Wetlands Ecology and Management最新文献

Phragmites australis is one of the most invasive wetland plants on the planet with both native and invasive haplotypes occurring in the United States. Three Phragmites haplotypes (Delta-, EU- and Gulf-types) co-occur in marshes of the Mississippi River Delta (MRD), where a recent dieback of Phragmites has prompted investigations about the potential for recolonization by seed. In other areas of the US, the invasive EU-type has been shown to spread by seed, yet little is known about reproduction modes of the Delta- and Gulf-types. We conducted a survey at 35 sites along the Mississippi River Delta region in southeast Louisiana to examine the potential for sexual reproduction across haplotypes as well as the potential for hybridization. Seed and pollen samples were collected from Phragmites populations to examine flowering phenology and determine pollen viability of the three lineages. We also conducted a seedbank assay in stands of three haplotypes to test the potential for recruitment by seed. Despite the observed potential for sexual reproduction in Delta- and EU- types, no Phragmites seedlings germinated from the seedbank. EU was the only haplotype to exhibit germination from seeds collected from seed heads. Both spatial separation and temporal isolation in flowering times indicate that hybridization between Phragmites haplotypes in the lower MRD is unlikely. High pollen production, increased pollen production following dieback, and viable seeds in the EU-type suggest that this invasive haplotype has a greater potential to invade new areas and adapt to stressors through sexual reproduction compared to than Delta-or Gulf haplotypes.

Wetland habitats experienced a dramatic reduction and fragmentation of biodiversity, because of human activities such as urbanization and agriculture. Now birds, as indicator of this biodiversity, have to breed, winter or stopover in wetlands embedded in a complex and highly altered human matrix. They may concentrate their activities in the wet remnant (wet reedbed) or suboptimal habitats (dry reedbed) and surroundings such as agricultural fields (maize). In a wide wetland area situated south-west of France in a main migration route, we tested if the abundance of passerine species differs among habitats according to their specialization and ecology (wet reedbed vs dry habitats; aquatics vs generalists; migrant vs local), We attempt to identify the underlying mechanisms of observed variation, looking at: arthropod availability in each habitat, bird diet of five insectivorous species and refuelling capacity of birds. Maize crops hosted more invertebrates and biomass than reedbeds for Coleoptera, Diptera, Araneida and Cicadellidae. This may explain why crops were used by aquatic passerines (Bluethroat, Sedge warblers, Reed warblers), migrant or local generalists (Robin, Blue tit, Great tit, Willow Warblers and Nightingale). Bluethroat’s diet was more focused on Formicidae and used the both habitats. In spite of the available food in maize, specialist birds preferred reedbed: Cetti warbler feeding in mainly Araneida and Cicadellidae; Sedge warbler Aphid and Coleoptera. Dry reedbed were better used by Grasshopper Warblers foraging Formicidae. Sedge and Reed warblers were more abundant in wet reedbed. We also noted for this last species youngs refuelling in maize crop. Therefore, the strategy to use maize crop may be different if resident or migrant. Generalist resident may disperse searching for food or transit area in continuity of vegetation; migrant need refuelling, particularly the aquatic trans-saharans more specialist on reedbed than the others. Finally, maize crop provided food resources and suitable shelter for a large group of species. It may be a supplement habitat of the wet and dry reedbeds, but not a substitute. Our study reaffirms to conserve and extend wet reedbed habitats threatened by clogging bush encroachment and drying.

This study aims to help coastal wetland managers understand the differences and trade-offs associated with alternative inventories in the United States (US) through a quantitative comparison of wetland land use land cover (LULC) maps available from the National Wetlands Inventory (NWI), Coastal Change Analysis Program (C-CAP), and Detection and Characterization of Coastal Tidal Wetland (DECODE). NWI and C-CAP were compared in five study sites spread across the Atlantic and Gulf coasts and align well under a four-class system, but discrepancies arise under a nine-class system, with C-CAP generally estimating smaller net wetland areas, larger emergent vegetation areas, and smaller scrub vegetation areas. The average overall accuracy for the C-CAP and NWI comparison is 89.4% and 82.4% for the coarser and finer scale classification systems, respectively. DECODE is available for two of the representative sites and uses a three-class system that differs from that of C-CAP and NWI, causing significant errors and an average overall accuracy of 59.5%. LULC change was quantified during the 1996 to 2016 period using the multi-temporal C-CAP and DECODE maps, showing that DECODE estimates significantly more change, by a factor of fifteen at one study site.. A spatial analysis of the classification differences shows that they often occur near the boundary of two wetland classes and within agricultural and built-up areas. The discrepancies in class definitions, net areas, and change estimates reported in this study should be referenced by managers who are developing wetland policies or management activities, such as carbon flux assessments and resilience plans.

Naturally occurring populations of Zizania palustris have declined in abundance since the 1800s. Due to its cultural, economic, and ecological importance, it has been the target of restoration. We aimed to inform restoration of Z. palustris in Michigan by performing experiments examining how conditions in restoration sites and future human impacts such as warmed water and elevated salinity affect Z. palustris during early phenophases. In a mesocosm study, we raised pH to levels seen in Wycamp Lake (over 8.5), where Z. palustris restoration success was limited, and found decreased germination by 50% and seedling biomass by 60%. No other responses analyzed were influenced by pH whereas increasing water temperature to 24 °C, simulating warming with climate change and warm spring conditions found in Wycamp Lake, decreased germination by 80%, decreased root and shoot biomass by 30 and 40%, respectively, caused spindly shoot morphology, and accelerated onset of germination by 1.2 days and floating leaf phenophase by 3.6 days. With concerns about road salt impacts on restored Z. palustris populations, we raised salinity to 500 mg NaCl L⁻¹ in a mesocosm experiment with no impact. A growth chamber experiment showed that adding NaCl up to ~ 1000 mgL⁻¹ increased Z. palustris biomass and germination with negative impacts above that threshold. In conclusion, Z. palustris is somewhat tolerant of increased salinity. However, high pH and warm water could impact restoration outcomes in Michigan lakes with warm spring water likely becoming a larger concern for Z. palustris restoration with climate change.

Leaf litter breakdown is a critical process in ecosystems, influencing food webs and biogeochemical cycles, particularly in inorganic soils such as those found in highland grassland systems. Our experiment examined the leaf litter breakdown of two species, Eucalyptus grandis (exotic) and Inga uruguensis (native), in the soil of riparian zones at subtropical highland grasslands. During the spring season, fine and coarse mesh litterbags with exotic and native leaf litter were incubated in riparian zones with (n = 3) and without (n = 3) tree and shrub layers, resulting in a total of 72 litter bags. In each sampling site, the dry weight of the natural litter was measured, and soil samples were collected for basic physical–chemical analysis. After 42 days of incubation, the remaining material in litter bags was weighed. Our study provided partial support for our hypothesis that the presence of trees and shrubs in riparian vegetation and edaphic macrofauna would enhance litter breakdown, particularly for high-quality litter. Surprisingly, the chemical and physical properties of the soil and riparian vegetation presence did not have a significant impact on the decomposition process, indicating efficient nutrient cycling in soil systems. However, the presence of edaphic fauna, especially soil macroinvertebrates, played a critical role in facilitating leaf litter breakdown. Additionally, we observed rapid breakdown rates for high-quality litter, aligning with our expectations, despite its exotic origin. Our findings highlight the importance of considering leaf quality and macro-detritivores in studying and managing leaf litter breakdown in riparian ecosystems.

Mangroves are highly productive ecosystems that supply carbon and nutrients to the coastal food web from autochthonous and allochthonous sources. The fluctuations in the quantity of these sources influence bacterial metabolic activity which is, in turn, directly linked to the trophic food web. Our study, reports the inter-annual variability of nutrients and dissolved organic carbon in addition to their impact on phytoplankton and bacterial biomass, respiration and production in the Mandovi and Zuari estuaries of southwest India. Radio-labeled substrates, NaH¹⁴CO₃, and titrated thymidine (³H-TdR) were employed to quantify primary productivity (PP) and bacterial productivity (BP), respectively. Our findings revealed that community respiration exceeded PP indicating a state of heterotrophy. Similarly, bacterial respiration (BR) exceeded BP suggesting that carbon is predominantly utilized for respiratory rather than assimilatory action. Analysis of BP/PP (Mandovi 0.48 to 4.46; Zuari 1.72 to 3.81) and PP/BR (Mandovi 0.02 to 1.42; Zuari 0.05 to 1.00) ratios showed considerable seasonal variability. Lower bacterial growth efficiency observed in Mandovi (average 30.35%) than Zuari (average 38.38%) suggests greater productivity in Zuari. Uncoupling of phytoplankton and bacteria during the monsoon and post-monsoon seasons implied heterotrophic conditions in both Mandovi and Zuari. Principal component analysis indicated distinct temporal variations in salinity, dissolved inorganic nutrients and dissolved organic carbon which had a significant influence on the trophic status of the mangrove and estuarine waters This study highlights the critical role of allochthonous organic matter in driving coastal heterotrophy and shaping the seasonal trophic dynamics in estuarine ecosystems.

Mosquitoes are closely associated with wetlands, as stagnant water in these ecosystems provides an ideal environment for the development of their immature stages. Human activities, such as artificial drainage for mosquito control, impact the ecological integrity of these ecosystems. Therefore, the objective was to compare the species composition of mosquitoes in two types of wetlands (swamp and herbaceous wetland) and a nearby human settlement, and determine the degree of risk, advocating for the conservation of these ecosystems. Collection of mosquito immature stages was conducted throughout on year in the municipality of Jamapa, in Veracruz state, Mexico. The richness and abundance of the collected species were determined, and the species composition of each site was compared through cluster and beta diversity analysis and analysis of similarity. The richness was higher in the two wetlands, and the abundance in human settlements. The species composition was different in all three sites. Mosquito species posing higher health risks were found in human settlements, and those posing lower risks in the swamp. As a result, it was possible to determine a disturbance gradient, with human settlements at the negative end of the gradient, the herbaceous wetland in the middle, and the swamp at the positive end, demonstrating that ecosystems preserving their original flora and fauna do not represent a significant risk for the transmission of mosquito-borne diseases.

Comparisons between vegetated and unvegetated intertidal habitats have led to the paradigm that benthic fauna are more abundant and diverse in the former. Mangroves are the dominant vegetation in estuarine intertidal zones of northern Brazil, however until now; there are no studies that investigated the macrobenthic fauna between vegetated and unvegetated intertidal habitats of estuaries at Amazon region. This study aimed to characterize the community structure of the macrobenthic fauna between an intertidal mudflat (non-vegetated area) and mangrove (vegetated area) of an estuarine gradient of salinity in the Amazon coast. Overall, finer sediments were found at the vegetated area and increased toward lower estuary. Overall, higher density and richness were found in the vegetated area and the values increased toward the lower estuary. The same pattern was found at the non-vegetated area. In general, our results showed the formation of a gradient of organism distribution along the estuary. Also, the results showed that the presence of the vegetation influences macrofaunal patterns.

Water abstraction and subsequent lowering of water table in Sasthamkotta, the largest freshwater lake in South West coast of India raised serious concerns on its management and future implications to terrestrial and aquatic associated fauna. Though a designated Ramsar site, Sasthamkotta Lake has been exposed to various anthropogenic stressors, which in recent years have caused a sudden decrease in its productivity. The study therefore aimed to delineate the present ecological health of the lake in terms of its trophic dynamics and ecosystem efficiency using ecosystem modeling approach. The estimated trophic level (TL) of the lake ranged between 1 (detritus) to 3.76 (fish-eating birds), indicating a skewed structure towards lower carnivorous groups. The ecosystem maturity indices (connectance index, and system omnivory index) revealed the lake to be immature and in the developing stage, though the origin of the lake has been traced back to the quaternary era. The higher value of system overhead (66%) denotes that this ecosystem has been resisting ecological perturbations, in spite of its age is noteworthy. Though the study indicates that the lake’s trophic structure is well-established, a variety of anthropogenic stressors reduce ground water levels and diminish aquifer recharge into the lake. This would significantly reduce the lake’s catchment area, affecting the entire biota. The results presented here is a pioneering attempt to understand the current ecological condition and impact of future possible stressors that need to be monitored for ensuring ecosystem integrity of the lake.

Ecosystem services comprise all the benefits that humanity obtains from ecosystems. Within the regulation services, wetlands soils have an important role in regulating the water cycle through water retention and the climate through carbon storage and sequestration. The objective of this research was to estimate the water retention capacity and the soil organic carbon content in the superficial portion of Ramsar wetlands soils in Quintana Roo, Mexico, to provide elements to the ecologic and economic valuation of regulation ecosystem services. A total of 268 soil samples were collected from the upper 20 cm soil layer, soil samples were processed and analyzed to obtain edaphic properties and organic carbon. We assessed the effect of 1) seasonality, 2) vegetation structure, and 3) soil type in the response variables water retention and organic carbon storage. The results indicate that the volumetric content and saturation degree were different among wetlands. Seasonality was not a significant factor in the assessment of these two regulation ecosystem services. The mean water storage capacity was 0.65 g water/cm³ of soil, representing from 500 to 1000 L water/m³ soil. The greatest carbon storage values were associated with mangroves established on Solonchak, with values between 5 and 8 Mg C/ha. The type of soil is the grouping variable that reported differences in water and carbon content in the soil, with Histosols retaining more water, but Solonchacks storing more carbon.