Salt marsh harvest mouse demography and habitat use in the Suisun Marsh,California

We undertook a 2-year (2002–2004) mark–recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. © 2011 The Wildlife Society.     

Waterfowl management and diet of the salt marsh harvest mouse

The salt marsh harvest mouse (Reithrodontomys raviventris) is an endangered species, endemic to the marshes of the San Francisco Bay, California, USA. This species is thought to feed primarily on pickleweed (Salicornia pacifica), although its diet is poorly understood, and a large proportion of remaining habitat for salt marsh harvest mice is managed for non-pickleweed vegetation to provide habitat for waterfowl. Using 2 sets of cafeteria trials, we tested food preferences of the salt marsh harvest mouse when offered a variety of plants and invertebrates from the Suisun Marsh, Solano County, California. In a set repeated menu, and unique seasonal menus, salt marsh harvest mice showed strong preferences for food types commonly grown for waterfowl, and also for non-native plants; in contrast, pickleweed was the most preferred during only some of the set and some of the seasonal trials. These results suggest that salt marsh harvest mice have a more flexible diet than previously thought, and will allow land managers in areas such as the Suisun Marsh to promote the growth of plants that provide foods that are preferred by both waterfowl and salt marsh harvest mice. © 2019 The Authors. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.     

Dietary characterization of the endangered salt marsh harvest mouse and sympatric rodents using DNA metabarcoding

The salt marsh harvest mouse (Reithrodontomys raviventris; RERA) is an endangered species endemic to the coastal wetlands of the San Francisco Estuary, California. RERA are specialized to saline coastal wetlands, and their historical range has been severely impacted by landscape conversion and the introduction of non‐native plant and rodent species. A better understanding of their diet is needed to assess habitat quality, particularly in relation to potential competitors. We investigated three questions using DNA metabarcoding with ITS2 and trnL markers: (1) Do RERA specialize on the native plant, pickleweed (Salicornia pacifica), (2) Do RERA consume non‐native plants, and (3) What is the dietary niche breadth and overlap with three sympatric native and non‐native rodents? RERA diet was dominated by two plants, native Salicornia and non‐native salt bush (Atriplex spp.), but included 48 plant genera. RERA diet breadth was narrowest in fall, when they consumed the highest frequencies of Salicornia and Atriplex, and broadest in spring, when the frequencies of these two plants were lowest. Diet breadth was slightly lower for RERA than for co‐occurring species in pairwise comparisons. All four species consumed similarly high frequencies of wetland plants, but RERA consumed fewer grasses and upland plants, suggesting that it may be less suited to fragmented habitat than sympatric rodents. Diet overlap was lowest between RERA and the native California vole (Microtis californicus). In contrast, RERA diet overlapped substantially with the native western harvest mouse (R. megalotis) and non‐native house mouse (Mus musculus), suggesting potential for competition if these species become sufficiently abundant.     

Coastal vegetation on the Western, Southern, and Eastern coasts of South Korea

We used the Braun-Blanquet method to study the vegetation of coastal wetlands in South Korea. Three habitat types were found, i.e., salt marshes, salt swamps, and sand dunes. These plant communities were classified as: 1) two groups (five associations each) in the salt marshes that comprised either annual herbaceous halophytes (ClassThero-Salicornietea), or biennial/perennial herbaceous species (ClassAsteretea tripolii); 2) one group in the salt swamps consisting of five hydrophilous halo-tolerant associations (ClassPhragmitetea); and 3) three groups in the sand dunes, including one association of annual herbaceous halophytes (ClassSalsoletea komarovii), seven associations of herbaceous perennial halophytes (ClassGlehnietea littoralis), and one association of shrub perennial halophytes (ClassVrticetea rotundifoliae). These three habitat types accounted for the majority of the six main classifications of coastal vegetation distributed in South Korea.     

Halophyte crop cultivation: The case for Salicornia and Sarcocornia

Increasing soil salinization and the growing scarcity of fresh water dictate the need for a creative solution to attain sustainable crop production. To accomplish this aim, the domestication of inherently salt tolerant plant species with economic value is proposed as a straightforward methodology. Most studies investigating salt tolerance mechanisms are linked to small, experimental systems that cannot be generalized to the real agricultural context. The crops Salicornia and Sarcocornia, however, with their extreme salt tolerance and long history of consumption by humans, make the ideal model plants on which to base a halophyte growth strategy. New applied technologies were developed for leafy vegetable production using small-scale greenhouse and in-field studies. Several cultivation systems adapted to the irrigation water salinity and the available soil conditions are described. Daylength manipulation and a repetitive harvest regime partially elucidated the flowering patterns of Salicornia and Sarcocornia and showed that flowering should be prevented for maximal vegetable production. Additionally, the beneficial effect of saline irrigation on quality parameters via the enhancement of stress-induced secondary metabolites with antioxidant capacity should be considered during cultivation. This review summarizes the recent developments in growing halophytes for food production with saline irrigation, using Salicornia and Sarcocornia as a case study.     

Constraints of feeding on Salicornia ramosissima by wigeon Anas penelope: an experimental approach

The coastal marshes of the Charente-Maritime (western France) are a major wintering area for wigeon Anas penelope. In these marshes, wigeon feed mainly on grasses, while foraging on Salicornia (a fleshy, succulent halophyte) is uncommon. In order to understand the reason for this under-exploitation, an experimental study was carried out with captive wigeon in autumn 1998 on a Salicornia ramosissima marsh in the Charente-Maritime. Birds were unable to maintain their body weight when feeding on Salicornia. Measurements of food chemical composition and metabolisability, as well as instantaneous intake rate of the birds (g/min) could not explain these weight losses. However, the time budget of wigeon revealed that they spent a maximum of 10–11 h per 24 h consuming Salicornia, whereas 18–19 h would have been needed to meet their daily energy requirements. The daily foraging time on Salicornia may have been limited by physiological constraints due to: (1) a high ash content (mainly salt, about 34% of dry matter), and/or (2) a digestive bottleneck, because of the waxy cuticle covering the leaves, which is likely to have constrained processing rate of Salicornia ears in the gut of birds. In the discussion, we address the question of the potential geographical differences in the use of Salicornia by birds.     

Relationships between syntaxonomy ofThero-Salicornietea and taxonomy of the generaSalicornia andSuaeda in the Iberian Peninsula

This paper deals with the syntaxonomy of the classThero-Salicornietea in the Iberian Peninsula, falling particularly upon the significance that taxonomy of the generaSalicornia andSuaeda has on it. Three alliances were differentiated, two Atlantic and one Mediterranean. The Atlantic ones wereSalicornion dolichostachyo-fragilis, with four associations grouping slikke communities with tetraploid glasswort (Salicornia) species, andSalicornion europaeo-ramosissimae, with three associations of schorre with generally diploid glasswort species. The Mediterranean allianceSalicornion patulae had six associations distributed both in coastal (southern and eastern coasts) and inland salt marshes. A complete syntaxonomy of the class, maps of the distribution of its associations and tables summarizing their floristic composition are also provided.     

Aboveground competition influences density‐dependent effects of cordgrass on sediment biogeochemistry

Interspecific interactions between plants influence plant phenotype, distribution, abundance, and community structure. Each of these can, in turn, impact sediment biogeochemistry. Although the population and community level impacts of these interactions have been extensively studied, less is known about their effect on sediment biogeochemistry. This is surprising given that many plants are categorized as foundation species that exert strong control on community structure. In southern California salt marshes, we used clipping experiments to manipulate aboveground neighbor presence to study interactions between two dominant plants, Pacific cordgrass (Spartina foliosa) and perennial pickleweed (Sarcocornia pacifica). We also measured how changes in cordgrass stem density influenced sediment biogeochemistry. Pickleweed suppressed cordgrass stem density but had no effect on aboveground biomass. For every cordgrass stem lost per square meter, porewater ammonium increased 0.3–1.0 µM. Thus, aboveground competition with pickleweed weakened the effects of cordgrass on sediment biogeochemistry. Predictions about plant–soil feedbacks, especially under future climate scenarios, will be improved when plant–plant interactions are considered, particularly those containing dominant and foundation species.     

Population biology of salt marsh and sand dune annuals

Annuals represent a significant component of the vegetation of coastal salt marshes and sand dunes. From many points of view, the two habitats might appear to have little in common. Yet both are characterized by episodes of low water potential, marked spatial and temporal heterogeneity and a zonation which, within certain limits, reflects successional change.There are also similarities of distribution. Annuals are dominant usually in the pioneer stages; the Salicornia-dominated low marsh areas are perhaps analogues with strandline ephemeral populations (e.g. Cakile maritima) on the fore-dunes. In mature stages, annuals are associated with small gaps in the matrix of perennials, at least some of these arising from drought or disturbance. Nevertheless populations can reach very high densities.The most striking contrast is phenological; only summer annuals are found on marshes, whereas winter annuals predominate on dunes (except for the strandline). Similarly there is a difference in species richness. Rather few species of annual are typical of marshes while a great many are found on dunes.Properties of the seed bank, survival, reproduction and population regulation are compared in marsh and dune annuals, with special reference to Cakile, Salicornia, Rhinanthus and Vulpia. Interpretations are suggested which take account of environmental predictability and heterogeneity. Finally, the general applicability of simple mathematical models of these populations in the different coastal habitats is considered.Nomenclature follows Clapham, Tutin & Warburg (1981) except where otherwise stated.     

Spatial and halophyte-associated microbial communities in intertidal coastal region of India

Microbial communities in intertidal coastal soils respond to a variety of environmental factors related to resources availability, habitat characteristics, and vegetation. These intertidal soils of India are dominated with Salicornia brachiata, Aeluropus lagopoides, and Suaeda maritima halophytes, which play a significant role in carbon sequestration, nutrient cycling, and improving microenvironment. However, the relative contribution of edaphic factors, halophytes, rhizosphere, and bulk sediments on microbial community composition is poorly understood in the intertidal sediments. Here, we sampled rhizosphere and bulk sediments of three dominant halophytes (Salicornia, Aeluropus, and Suaeda) from five geographical locations of intertidal region of Gujarat, India. Sediment microbial community structure was characterized using phospholipid fatty acid (PLFA) profiling. Microbial biomass was significantly influenced by the pH, electrical conductivity, organic carbon, nitrogen, and sodium and potassium concentrations. Multivariate analysis of PLFA profiles had significantly separated the sediment microbial community composition of regional sampling sites, halophytes, rhizosphere, and bulk sediments. Sediments from Suaeda plants were characterized by higher abundance of PLFA biomarkers of Gram-negative, total bacteria, and actinomycetes than other halophytes. Significantly highest abundance of Gram-positive and fungal PLFAs was observed in sediments of Aeluropus and Salicornia, respectively than in those of Suaeda. The rhizospheric sediment had significantly higher abundance of Gram-negative and fungal PLFAs biomarkers compared to bulk sediment. The results of the present study contribute to our understanding of the relative importance of different edaphic and spatial factors and halophyte vegetation on sediment microbial community of intertidal sediments of coastal ecosystem.     

The effect of salinity on the dominance-diversity relations of experimental coastal macrophyte communities

Salinity and water regime have previously been recognised as the main environmental factors controlling the abundance of coastal submerged macrophytes in temporarily-flooded marshes in the Camargue. The effects of these environmental variables, which are considered interrelated, are tested experimentally by subjecting experimental macrophyte communities from six temporarily flooded marshes to different levels of salinity (from 0 to 6 g/1 Cl^?). Communities subjected to high salinity levels (4 and 6 g/1 Cl~) showed a decrease in species richness and in biomass of all species involved. The species that most frequently dominate these communities, Chara áspera and Zannichellia pedunculata, are tolerant of salt and dominate over the entire salinity range. Three species groups can be distinguished based on the distribution of their biomass and centre of gravity of distribution over the salinity range: (1) non-salt-tolerant species, ‘glyco-phytes’, (2) moderately salt-tolerant species and (3) very tolerant species (‘halophytes’). A species ordination based on the experiments appeared to give results close to those previously obtained from field data.     

Phylogeny,biogeography and ecological diversification of Sarcocornia (Salicornioideae,Amaranthaceae)

Background and Aims Sarcocornia comprises about 28 species of perennial succulent halophytes distributed worldwide, mainly in saline environments of warm-temperate and subtropical regions. The genus is characterized by strongly reduced leaves and flowers, which cause taxonomic difficulties; however, species in the genus show high diversity in growth form, with a mat-forming habit found in coastal salt marshes of all continents. Sarcocornia forms a monophyletic lineage with Salicornia whose species are all annual, yet the relationship between the two genera is poorly understood. This study is aimed at clarifying the phylogenetic relationship between Sarcocornia and Salicornia, interpreting biogeographical and ecological patterns in Sarcocornia, and gaining insights into putative parallel evolution of habit as an adaptation to environmental factors.Methods A comprehensively sampled and dated phylogeny of Sarcocornia is presented based on nuclear ribosomal DNA (external transcribed spacer) and chloroplast DNA (atpB-rbcL, rpl32-trnL) sequences; representative samples of Salicornia were also included in the analyses. To infer biogeographical patterns, an ancestral area reconstruction was conducted.Key Results The Sarcocornia/Salicornia lineage arose during the Mid-Miocene from Eurasian ancestors and diversified into four subclades: the Salicornia clade, the American Sarcocornia clade, the Eurasian Sarcocornia clade and the South African/Australian Sarcocornia clade. Sarcocornia is supported as paraphyletic, with Salicornia nested within Sarcocornia being sister to the American/Eurasian Sarcocornia clade. The American and the South African/Australian Sarcocornia clade as well as the Salicornia clade were reconstructed to be of Eurasian origin. The prostrate, mat-forming habit arose multiple times in Sarcocornia.Conclusions Sarcocornia diversified in salt-laden environments worldwide, repeatedly evolving superficially similar prostrate, mat-forming habits that seem advantageous in stressed environments with prolonged flooding, high tidal movement and frost. Some of these prostrate-habit types might be considered as ecotypes (e.g. S. pacifica or S. pillansii) while others represent good ecospecies (e.g. S. perennis, S. decumbens, S. capensis), hence representing different stages of speciation.     

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.     

The influence of rainfall variability on the species composition of a northern California salt marsh plant assemblage

Natural variability in the species composition of salt marsh plant assemblage was studied for 4 years (1986–90) at Bolinas Lagoon, California (USA). The study was conducted during a period in which little or no physical disturbance occurred in the marsh. During the study, Bolinas Lagoon experienced highly variable rainfall, both within and between years. In years with average or below average winter and spring rainfall, the cover of Salicornia virginica increased relative to that of the other species. During the one year with much higher than average spring rainfall, the cover of Salicornia declined and rare species increased in relative abundance. These patterns suggest that under typical marsh conditions, the plant assemblage experiences stress due to low availability of freshwater and high soil salinity. Under such conditions, the stress-tolerant Salicornia dominates the assemblage. If, however, there is abundant rainfall early in the growing season, the other species are released from stress and are able to increase in cover. The marsh of Bolinas Lagoon appears to be resistant to change and able to tolerate stress. Few studies have examined natural variability in species in undisturbed marshes and more of such studies must be made in order to understand whether or not marshes are in general resistant to change caused by rainfall variability.Abbreviations MLLW = mean lower low water     

Habitat selection of wintering passerines in salt marshes of the German Wadden Sea

The salt marshes of the Wadden Sea are important wintering areas for some species of granivorous passerines, which have declined considerably since the 1960s. We investigated the habitat choice of all wintering passerines in eight study areas in German salt marshes with special consideration of human impact on these habitats. Granivorous species that almost exclusively winter in salt marshes, Shorelark (Eremophila alpestris), Snow Bunting (Plectrophenax nivalis) and Twite (Carduelis flavirostris) were concentrated in the lower salt marsh vegetation and in the driftlines, while all other species preferred the high upper salt marsh communities, although Rock Pipits (Anthus petrosus littoralis) fed in muddy areas along ditches. Shorelarks switched habitat in conditions where seeds were scarce to feed instead on arthropods in upper salt marshes. Intensively sheep-grazed upper salt marshes resemble lower salt marshes in their vegetation and were therefore mainly visited by Shorelarks, Snow Buntings and Twites. In winter, the driftline is preferred by the two former species, while in autumn and spring more birds foraged in the salt marshes. Twites prefer to feed mainly on seeds of Salicornia. Areas with S. europaea are visited mainly in late autumn and early winter, while areas with S. stricta are used throughout the winter because of a steady supply of seeds. Several years after embankment, polders are hardly used any more by the lower salt marsh species as the habitat changes into freshwater marshes. Large embankment projects since the early 1960s have included salt marshes and intertidal flats, and the resultant loss of habitat is responsible for the decline of lower salt marsh species. For other passerine species the effects of reclamation are unknown. The effects of intensified grazing on the wintering populations of Shorelark, Snow Bunting and Twite are still unresolved. Although grazing supports lower salt marsh vegetation, the seed production per plant is much lower there and some important seed producers hardly occur. Since grazing was reduced and embankment projects have been stopped, the salt marsh areas (especially lower salt marshes) have increased and so have the wintering populations of Shorelark, Snow Bunting and Twite. For the other species, the consequences of habitat changes are unknown, although it is suggested that reduced grazing will support them. Reducing the human impact on salt marshes will, in the long run, probably lead to a natural salt marsh with much variety in elevation and in its corresponding vegetation and bird communities. Meanwhile, management by grazing might be required in parts of the salt marshes.     

The importance of salt-marsh wetness for seed exploitation by dabbling ducks Anas sp.

The relationship between the inundation of a salt marsh in southeast Denmark not subject to lunar tides and the availability and predation of seeds of the annuals Salicornia spp. and Suaéda maritima by autumn staging dabbling ducks was studied by carrying out exclosure experiments over the course of 2 years. There was a marked difference in the wetness of the salt marsh between the two study years, which resulted in distinct temporal patterns of salt-marsh use by dabbling ducks. In both years, the depletion of seeds of both Salicornia spp. and S. maritima was initiated subsequent to the flooding of the sample transects, which also induced the gradual release of seeds from the plants within the exclosures. Nevertheless, seeds were removed more rapidly in plots visited by dabbling ducks than in the exclosures. The predation of seeds took place as soon as the individual plants had been fully submerged, but before the seeds were released from the plants. The timing of flooding events during early autumn may potentially affect the availability of the salt-marsh seed stock. Therefore, weather conditions may impose critical constraints on the feeding opportunities for dabbling ducks during autumn migration on non-tidal salt marshes.     

滨海盐渍土壤中不同类型盐生植物富集镉的效应

为了利用被镉污染的滨海盐渍土壤,通过实验对比分析3种不同类型盐生植物对盐渍土中镉的富集效应,以期初步探明不同类型盐生植物在镉污染盐渍土壤修复中的效果。选择的3种盐生植物类型是:聚盐盐生植物,泌盐盐生植物和避盐盐生植物。通过温室盆栽实验,将植物在不同镉含量的盐渍土壤中种植培养60 d,测定和分析不同类型盐生植物对镉的生物浓缩因子、转移系数以及植株内地上部分和根部生物量和镉含量的变化。结果表明,不同镉含量的土壤对碱蓬和芦苇的生长影响较小,对二色补血草的生长影响较大。不同镉含量的土壤中,芦苇地上部分镉的生物浓缩因子变化差异不显著,并且其地上部分吸收镉的百分率较高。碱蓬和芦苇的转移系数大于二色补血草的转移系数,并且碱蓬的转移系数在不同镉含量的土壤中变化不显著;二色补血草的转移系数随着土壤中镉含量的增加而显著增大。3种盐生植物中,碱蓬最具修复镉污染盐渍土壤的潜力,这可能和它是聚盐盐生植物的生理类型有关。芦苇整个植株的地上部分富集镉的总量在3种植物中是最高的,因此,芦苇在镉含量较低时也可以做为镉污染盐渍土壤的修复材料。     

盐胁迫下3种滨海盐生植物的根系生长和分布

我国广大滨海地区的盐土上发育着大量的盐生植物,这些植物的根系对维持土壤稳定性,减小风蚀和水蚀具有重要作用。在水培条件下,针对碱蓬、盐角草和盐地碱蓬3种滨海盐生植物,研究它们在不同盐浓度条件下根系分布的差异。结果表明:一定浓度的盐分可以促进3种盐生植物生长,但较高浓度的盐抑制其生长,特别是对根系生长的抑制作用更大。在同样盐浓度下,盐地碱蓬的生长最快,生物量也最大。在盐分浓度较低时,3种盐生植物的主根长和总根长都有所增加,与对照相比,盐角草增加的幅度较大,但高浓度的盐会抑制根系总长度的增加,其中盐角草较碱蓬和盐地碱蓬抑制的程度轻。盐分对3种植物的根系平均直径没有显著的影响,但有减小的趋势。在水培条件下,碱蓬和盐角草的根系上、中、下部分布的较均匀,而盐地碱蓬的根系中部比上部和下部有显著的增加,盐分对每种植物的根系的分布没有显著的影响。从根系的分布特征可以推断:盐角草比碱蓬和盐地碱蓬具有较强的抗盐性和耐瘠薄能力;碱蓬的耐盐能力较其它两种植物差,盐角草的耐盐性最强。根据3种滨海盐生植物的根系生长和分布特征,证明这3种植物的根系分属于2种功能型,碱蓬是浅根系功能型,盐角草和盐地碱蓬是深根系功能型。根系分布的参数表明3种滨海盐生植物中盐地碱蓬是用来加强土壤稳定性最好的植物。