Long-term population trends of endangered Hawaiian waterbirds

We analyzed long-term winter survey data (1956–2007) for three endangered waterbirds endemic to the Hawaiian Islands, the Hawaiian moorhen (Gallinula chloropus sandvicensis), Hawaiian coot (Fulica alai), and Hawaiian stilt (Himantopus mexicanus knudseni). Time series were analyzed by species–island combinations using generalized additive models, with alternative models compared using Akaike information criterion (AIC). The best model included three smoothers, one for each species. Our analyses show that all three of the endangered Hawaiian waterbirds have increased in population size over the past three decades. The Hawaiian moorhen increase has been slower in more recent years than earlier in the survey period, but Hawaiian coot and stilt numbers still exhibit steep increases. The patterns of population size increase also varied by island, although this effect was less influential than that between species. In contrast to earlier studies, we found no evidence that rainfall affects counts of the target species. Significant population increases were found on islands where most wetland protection has occurred (Oahu, Kauai), while weak or no increases were found on islands with few wetlands or less protection (Hawaii, Maui). Increased protection and management, especially on Maui where potential is greatest, would likely result in continued population gains, increasing the potential for meeting population recovery goals.     

Mitigation under Section 404 of the Clean Water Act: where it comes from, what it means

The requirement to mitigate impacts to wetlands and streams is a frequently misunderstood policy with a long and complicated history. We narrate the history of mitigation since the inception of the Clean Water Act Section 404 permit program in 1972, through struggles between the US Environmental Protection Agency and the US Army Corps of Engineers, through the emerging importance of wetland conservation on the American political landscape, and through the rise of market-based approaches to environmental policy. Mitigation, as it is understood today, was not initially foreseen as a component of the Section 404 permitting program, but was adapted from 1978 regulations issued by the Council on Environmental Quality as a way of replacing the functions of filled wetlands where permit denials were unlikely. EPA and the Corps agreed in 1990 to define mitigation as the three steps of avoidance, minimization, and compensation, principles which must be applied to permit decisions in the form of the environmental criteria in EPA’s 404(b)(1) Guidelines. Through the 1980s and 1990s, the compensation component of mitigation has become nearly the sole focus of mitigation policy development, and has been the subject of numerous guidance documents and memoranda since 1990. Avoidance and minimization have received far less policy attention, and this lack of policy development may represent a missed opportunity to implement effective wetland conservation.

Analysis of fungal community structure in the soil of Zoige Alpine Wetland

To understand the soil fungal community diversity in different zones of the Zoige Alpine Wetland, BIOLOG analysis and traditional culture method were employed in our research. Three sample sites namely the Conservatory Station up-hill slope (CSUS), the Flower Lake side (FLS) and the Conservatory Station down slope (CSDS) with increasing by water content were investigated. The results of BIOLOG showed that fungal catabolic richness index (S) and Shannon diversity index (H) increasingly rose with water content augmented from CSUS to CSDS, while different from the former tendency, the fungal catabolic activity was highest at CSDS and lowest at FLS. Principal component analysis (PCA) results demonstrated the functional diversity of fungal community varied among the three sample sites, showing us more similarity between CSDS and FLS, and considerable difference between CSUS and the former two sites. The outcome of traditional culture method illustrated the number of soil fungi increased from CSUS to CSDS, while the sort of fungal species that could be cultured did not show much difference among the three sample sites.     

N:P ratios, δN fractionation and nutrient resorption along a nitrogen to phosphorus limitation gradient in an oligotrophic wetland complex

The vegetation N:P ratio is thought to be a diagnostic indicator of the nature of nutrient limitation in wetland vegetation. It should therefore be closely linked to other indicators of nutrient acquisition and conservation, such as nitrogen stable isotope fractionation (δ¹⁵N), nutrient resorption efficiency (RE) and resorption proficiency (RP). However, the interrelationships among these traits and the N:P ratio remain unclear. We compared tissue nutrient concentrations, N:P ratios, δ¹⁵N fractionation, RE, and RP along an N to P limitation gradient in an oligotrophic wetland valley in the South Island of New Zealand. Within the valley, the soil TN:TP ratio increased from 1.3 to 18.0 in three discrete wetlands along the gradient. In pooled data from all vegetation communities within each site, the mass-based vegetation N:P ratio correlated significantly (r² = 0.35, P < 0.01) to soil TN:TP ratios and increased from 10.2 ± 2.7 to 13.5 ± 3.6 along the N to P limitation gradient. This was accompanied by an increase in tissue δ¹⁵N enrichment from 2.05 ± 1.12‰ to 6.27 ± 1.70‰, consistent with more open N cycling and lower N demand. These trends held within all vegetation types, but were particularly strong in a Typha orientalis (C-strategist) community (soil TN:TP vs vegetation N:P correlation r² = 0.78, P < 0.001; δ¹⁵N increase from 1.81 ± 0.44‰ to 7.73 ± 1.79‰). The individual N and P concentrations and retention patterns were more species-specific and less responsive to the nutrient limitation gradient. T. orientalis maximised N resorption as N limitation increased (increasing NRE from 50.8 ± 3.3% to 71.7 ± 7.4%; reducing NRP from 0.70 ± 0.12% to 0.36 ± 0.13%) but did not alter PRE or PRP, whereas the S-strategist Schoenus pauciflorus maximised P resorption as P limitation increased (increasing PRE from 48.0 ± 5.6% to 73.5 ± 10.1%; reducing PRP from 0.053 ± 0.008% to 0.015 ± 0.004%) but did not alter NRE or NRP. These results show that the tissue N:P ratio and its associated δ¹⁵N enrichment are highly responsive indicators of the relative availability of N and P at the site and community level. However, they are not indicators of species-specific physiological requirements for N and P, or of likely responses of individual species to N or P enrichment, which are better interpreted from indicators such as RE and RP that describe nutrient retention behaviour.     

Temperature and salinity tolerance of Mesopodopsis africana O. Tattersall in the freshwater-deprived St. Lucia Estuary, South Africa

Mesopodopsis africana is a key species in the St. Lucia Estuary, Africa's largest estuarine lake. This system is currently undergoing an unprecedented crisis due to freshwater deprivation. A reversed salinity gradient has persisted with hypersaline conditions (> 300) occurring in the upper regions of the estuarine lake. In the context of climate change, rising temperatures will not only push the thermal tolerance limits of estuarine organisms, but increased evaporation from this lake's large surface area will lead to further salinity increases. The present study aims to determine the temperature and salinity tolerance of M. africana, both through in situ studies and the use of laboratory experiments. Results indicate that M. africana is a broad euryhaline species. Mysids were recorded at salinity levels ranging from 2.55 to 64.5 in situ. While experiments revealed a narrower salinity tolerance, acclimation resulted in a significant increase in the tolerance range of this species. It is probable, however, that slower acclimation times may increase survival rates even further, particularly in the higher salinity treatments. M. africana was especially tolerant of the lower salinity levels. In the 20 °C acclimation experiment, LS₅₀ at 1 and 2.5 was only reached after 8 and > 168 h, respectively. Survival at 10 and 40 °C was negligible at all salinity levels. This concurs with field results which documented mysids at temperatures ranging from 16.2 to 30.9 °C. Salinity and temperature increases associated with global climate change may, therefore, have significant implications for these mysid populations, with cascading effects on the higher trophic levels which they support.     

Spartina alterniflora invasions and effects on crab communities in a western Pacific estuary

We investigated Spartina alterniflora invasions, their relationship with shoreline dynamics and effects on crab communities in the Yellow River estuary, China, where shoreline dynamics have been accelerated due to human-mediated estuarine sediment deposition and sea-level rise. We determined the distribution of Spartina with extensive ground surveys, and quantified shoreline dynamics between 2001 and 2009 by interpreting satellite images. We used pitfall traps to sample crab populations in Spartina-invaded habitats and non-invaded mudflats in 2009 and 2010. Large areas (>0.5 km²) of Spartina plants were found at three locations in the estuary. The seaward limit of Spartina at each location generally coincided with the present shoreline, regardless of historical shoreline advance or retreat. Crab communities in Spartina-invaded habitats significantly differed from those in non-invaded habitats. The total number and biomass of crabs caught per trap were much higher in Spartina-invaded habitats than in non-invaded habitats, however, species richness and Shannon diversity were much lower. These results suggest that Spartina invasions are likely to keep pace with shoreline dynamics accelerated by global change and have significant ecological consequences for crab communities. These issues should be taken into account to improve the use and management of Spartina, especially in rapidly accreting estuaries with large-area mudflats that are important habitats but prone to Spartina invasions.     

Description of a new species of Potamonautes MacLeay, 1838, from the iSimangaliso Wetland Park,South Africa

A new species of freshwater crab, Potamonautes isimangaliso sp. n., is described from the western shores of False Bay, Hluhluwe, within the iSimangaliso Wetland Park, South Africa. While bearing a superficial resemblance to Potamonautes lividus, the new species has been found to be genetically distinct, diverging from the former by 7.4–7.8% in mtDNA. Potamonautes isimangaliso most closely resembles Potamonautes lividus, but is distinguished by a unique suite of carapace characters, colouration, and size. The new species also lives in close association with oxygen-poor, fresh ephemeral pans, while the habitat of Potamonautes lividus is well above the surface water line of the closest water body. An updated identification key for the Potamonautes species of South Africa is provided.     

Using the floristic quality concept to assess created and natural wetlands: Ecological and management implications

We applied the floristic quality index (FQI) to vegetation data collected across a chronosequence of created wetland (CW) sites in Virginia ranging in age from one to 15 years post-construction. At each site, we also applied FQI to a nearby forested reference wetland (REF). We tested the performance of the index against a selection of community metrics (species richness, diversity, evenness, percent native species) and site attributes (age, soil physiochemical variables). FQI performed better when non-native species (C-value = 0) were removed from the index, and also when calculated within rather than across vegetation layers. A modified, abundance-weighted FQI showed significant correlation with community and environmental variables in the CW herbaceous layer and REF herbaceous and shrub-sapling layers based on Canonical correspondence analysis (CCA) ordination output. These results suggest that a “natives only”, layer-based version of the index is most appropriate for our region, and an abundance-weighted FQI may be useful for assessing floristic quality in certain layers. The abundance-weighted format has the advantage of preserving the “heritage” aspect of the species conservatism concept while also entraining the “ecology” aspect of site assessment based on relative abundances of the inhabiting species. FQI did not successfully relate CW sites to REF sites, bringing into question the applicability of the FQI concept in comparing created wetlands to reference wetlands, and by analogy, the use of forested reference wetlands in general to assess vegetation development in created sites.     

湖北斧头湖湖滨湿地植物的联结与相关分析

利用２×２列联表法结合Ｘ２检验对湖北武昌斧头湖湖滨湿地植物进行了联结分析,计算了种间的相关系数并检验了种间相关显著性。结果表明这些种组构成了一个连续体。文中还讨论了各种组的生态意义。     

Decomposition of aboveground and belowground organs of wild rice (Zizania latifolia): mass loss and nutrient changes

Decomposition of aboveground and belowground organs of the emergent macrophyte Z.latifolia was investigated using a litterbag technique for a period of 359 days in a freshwater marsh in Japan. Aboveground parts were classified into: leaves, sheaths and stems. Belowground parts were classified into: horizontal rhizomes (new rhizome, hard rhizome, soft rhizome) and vertical rhizome (stembase). The decay rate (k) was 0.0036 day⁻¹, 0.0033 day⁻¹ and 0.0021 day⁻¹ for leaves, sheaths and stems, respectively. For belowground parts, the decay rate varied considerably from 0.0018 day⁻¹ to 0.0079 day⁻¹, according to differences in the initial chemical compositions of rhizomes. After 359 days of decay, new rhizomes lost 94% of their original dry mass, compared with a loss of 48–84% for the other rhizomes. There was a significant positive relationship between litter quality and decay rate for horizontal rhizomes. For the new rhizomes, which had an internal nitrogen content of 24.2 mg N g⁻¹ dry mass, the mass loss was 40% higher than that of soft rhizomes, which had an internal N content of 9.8 mg N g⁻¹ dry mass. Over the period of 359 days, the nitrogen concentration in all rhizome types decreased to levels lower than initial values, but the phosphorus concentration remained constant after an initial leaching loss. Most nitrogen and phosphorus were lost during the first 45 days of decay. Changes in carbon to nitrogen (C:N) and carbon to phosphorus (C:P) ratios basically followed inversed trends of the nitrogen and phosphorus concentrations.