The community composition of Californian coastal sage scrub

Summary Coastal sage scrub is a community found extensively throughout cismontane California south of San Francisco, but has been surprisingly little studied. In the study area, which extends from Santa Barbara to the San Gorgonio Pass, two major floristic groupings can be found. In the basin bounded coastwards by a line drawn along the axis of the Santa Ana Mountains a large number of native and introduced annual herbs and a few shrubs (e.g.Encelia farinosa), rare or absent in the remainder of the study area, characterize one floristic group. In the coastal region the variety of shrub species increases, and the herbs are predominantly native and more restricted in number. Eleven groups defined by physiognomy, structure and species dominance, and arbitrarily called associations, are recognized. These associations can be grouped into four physiognomic-structural types which transgress the boundaries of the floristic groups. The results of this study and the limited previous literature suggest that Californian coastal sage scrub could be divided, mainly on floristic criteria, into Venturan, San Diegan and Riversidian sage.Plant nomenclature follows Munz & Keek (1968).We gratefully acknowledge the financial help provided by the Department of Earth Sciences, University of California, Riverside, and the aid in plant identification provided by Mr. Oscar Clarke, Museum Scientist, Department of Biology, University of California, Riverside.     

Phylogenetic diversity and investigation of plant growth-promoting traits of actinobacteria in coastal salt marsh plant rhizospheres from Jiangsu,China

Actinobacteria from special habitats are of interest due to their producing of bioactive compounds and diverse ecological functions. However, little is known of the diversity and functional traits of actinobacteria inhabiting coastal salt marsh soils. We assessed actinobacterial diversity from eight coastal salt marsh rhizosphere soils from Jiangsu Province, China, using culture-based and 16S rRNA gene high throughput sequencing (HTS) methods, in addition to evaluating their plant growth-promoting (PGP) traits of isolates. Actinobacterial sequences represented 2.8%–43.0% of rhizosphere bacterial communities, as determined by HTS technique. The actinobacteria community comprised 34 families and 79 genera. In addition, 196 actinobacterial isolates were obtained, of which 92 representative isolates were selected for further 16S rRNA gene sequencing and phylogenetic analysis. The 92 strains comprised seven suborders, 12 families, and 20 genera that included several potential novel species. All representative strains were tested for their ability of producing indole acetic acid (IAA), siderophores, 1-aminocyclopropane-1-carboxylate deaminase (ACCD), hydrolytic enzymes, and phosphate solubilization. Based on the presence of multiple PGP traits, two strains, Streptomyces sp. KLBMP S0051 and Micromonospora sp. KLBMP S0019 were selected for inoculation of wheat seeds grown under salt stress. Both strains promoted seed germination, and KLBMP S0019 significantly enhanced seedling growth under NaCl stress. Our study demonstrates that coastal salt marsh rhizosphere soils harbor a diverse reservoir of actinobacteria that are potential resources for the discovery of novel species and functions. Moreover, several of the isolates identified here are good candidates as PGP bacteria that may contribute to plant adaptions to saline soils.     

三江平原典型沼泽湿地螺类组成生态指示

螺类作为湿地的重要生物类群,对环境变化响应敏感,这使得螺类成为潜在的环境指示物种。为了研究中国东北沼泽湿地不同类型湿地螺类群落结构的差异以及螺类作为不同类型湿地指示物种的可能,在2014年9月和2015年5月对小叶章沼泽化草甸湿地、臌囊苔草湿地、毛苔草湿地、漂筏苔草湿地共17个采样点进行螺类样品采集。共采集到了螺类8科13属17种4452个。研究表明,螺类以扁卷螺科Planorbidae、椎实螺科Lymnaeidae、膀胱螺科Physidae为主;4种不同类型湿地螺的种类组成不同,这些螺类的种类组成与不同类型湿地的水深、植物类型组成等湿地特征是相对应。螺类的生物多样性指数(ShannonWiener指数和Marglef指数)在不同类型湿地之间也存在一定差异,筛选了指示螺类6种,无褶螺是小叶章沼泽化草甸的指示物种,小土蜗、半球多脉扁螺和虹蛹螺是臌囊苔草湿地的指示物种,琥珀螺是毛苔草湿地的指示物种,平盘螺是漂筏苔草湿地的指示物种,这表明了螺类是沼泽湿地类型的重要指示生物。也为螺类生物多样性资源的保护、恢复和生态评价提供科学依据和资料积累。     

Enhanced invertebrate prey production following estuarine restoration supports foraging for multiple species of juvenile salmonids (Oncorhynchus spp.)

Estuaries provide crucial foraging resources and nursery habitat for threatened populations of anadromous salmon. As such, there has been a global undertaking to restore habitat and tidal processes in modified estuaries. The foraging capacity of these ecosystems to support various species of out‐migrating juvenile salmon can be quantified by monitoring benthic, terrestrial, and pelagic invertebrate prey communities. Here, we present notable trends in the availability of invertebrate prey at several sites within a restoring large river delta in Puget Sound, Washington, U.S.A. Three years after the system was returned to tidal influence, we observed substantial additions to amphipod, copepod, and cumacean abundances in newly accessible marsh channels (from 0 to roughly 5,000–75,000 individuals/m²). In the restoration area, terrestrial invertebrate colonization was dependent upon vegetative cover, with dipteran and hymenopteran biomass increasing 3‐fold between 1 and 3 years post‐restoration. While the overall biodiversity within the restoration area was lower than in the reference marsh, estimated biomass was comparable to or greater than that found within the other study sites. This additional prey biomass likely provided foraging benefits for juvenile Chinook, chum, and coho salmon. Primary physical drivers differed for benthic, terrestrial, and pelagic invertebrates, and these invertebrate communities are expected to respond differentially depending on organic matter exchange and vegetative colonization. Restoring estuaries may take decades to meet certain success criteria, but our study demonstrates rapid enhancements in foraging resources understood to be used for estuary‐dependent wildlife.     

Holocene vegetation and climate evolution of Corpus Christi and Trinity bays: Implications on coastal Texas source-to-sink deposition

The Texas coastline stretches 595 km across almost 4° of latitude and is home to diverse coastal vegetation assemblages, yet only a handful of studies have documented the climate and vegetative change of this region through the Holocene. We provide a detailed palynological record of Holocene climate for coastal Texas, based upon three subaqueous sediment cores from Corpus Christi Bay and Trinity Bay. Cluster analysis and correspondence analysis were used to investigate changes in palynological assemblages through time within each core. Common to both bays are nonarboreal taxa including Asteraceae (mainly Ambrosia and Helianthus), Chenopodium, Poaceae, and arboreal taxa such as Carya, Pinus, and Quercus. Our record shows that the coastal environments of central Texas began a transition from herbaceous (nonarboreal) dominated vegetation to arboreal vegetation as early as 8.4 ka within Corpus Christi Bay, and 3.8 ka within Trinity Bay. We note flooding events at 8.2, 5.4, and 3.6 ka in Corpus Christi Bay, and at 1.7, 1.2, and 0.8 ka in Trinity Bay. These events were caused by storms, sea level changes including flooding of relict river terraces, and changes in sediment delivery to the bays. The pollen record also shows evidence for changes in fluvial discharge to Corpus Christi Bay at 4.1 and 2.2 ka, and at 1.8 ka in Trinity Bay. We also see Zea mays in Trinity Bay, indicating local Native American agriculture. We observe no significant changes during the middle Holocene Climatic Optimum, and subtle but not statistically significant evidence of more variable climate oscillations than other records from more interior sites in Texas available for the late Holocene. This indicates that coastal Texas’ climate has operated semi-independently from central Texas regions, and was primarily driven by a coast-wise gradient of precipitation and evapotranspiration.     

Livestock grazing affects vernal pool specialists more than habitat generalists in montane vernal pools

Questions

Do livestock grazing and seasonal precipitation structure species composition in montane vernal pools? Which grazing and precipitation variables best predict cover of vernal pool specialists and species with broader habitat requirements? Is vernal pool species diversity correlated with livestock exclosure, and at what spatial scales?

Location

Montane vernal pools, northeast California, USA.

Methods

Vegetation was sampled in 20 vernal pools, including pools where livestock had been excluded for up to 20 years We compared plant species composition, functional group composition and species diversity among sites that varied in grazing history and seasonal precipitation using CCA and LMM.

Results

Although vernal pool specialists were dominant in montane vernal pools, over a third of plant cover was comprised of species that occur over a broad range of wetland or upland environments. The species composition of vernal pool plant communities was influenced by both livestock grazing and precipitation patterns, however the relative effects of these environmental variables differed by functional group. Livestock exclosures favoured perennial vernal pool specialists over annual vernal pool specialists. In contrast, the cover of habitat generalists was more strongly influenced by seasonal precipitation than livestock grazing. At small spatial scales, species richness and diversity decreased as the number of years a pool had been fenced increased, but this relationship was not significant at a larger spatial scale.

Conclusions

Both livestock grazing and seasonal precipitation structure the montane vernal pool plant community. We found that livestock grazing promotes the cover of annual vernal pool specialists, but at the expense of perennial vernal pool specialists. Wetter vernal pools, however, support higher cover of wetland generalist species regardless of whether pools are grazed.     

Recovery potential of microwetlands from agricultural land uses

Many ecosystems located within agricultural landscapes are in decline, particularly woodlands, grasslands and wetlands. Surviving remnants are generally fragmented and unrepresentative of pre‐disturbance states. Here, we investigate the potential for recovery of ecosystem function in a grassy woodland–wetland mosaic in south‐eastern Australia. We focus on the Plains Woodland/Herb‐rich Gilgai Wetland Mosaics which have declined in extent by 85%. The gilgai soils form a distinctive microrelief of mounds and depressions which become seasonally waterlogged, providing important habitat for a large range of aquatic and dryland species. We surveyed 10 remnants subject to agricultural intensification and seven remnants subject to passive restoration (four with cessation of cultivation and three with livestock removal). Gilgai microrelief was homogenized by cultivation, showed some recovery after release from cultivation, and was insensitive to grazing pressure. Floristic diversity, assessed through indicator species, was vulnerable to grazing. Indicator species were more prevalent in previously grazed sites, but further study is required to determine whether this reflects recovery or differing overall management history. We conclude that passive restoration is possible for recovery of wetland function and some biodiversity values. These conservation actions should be encouraged given the important role these microwetlands play in landscape connectivity and as drought refugia.     

Historical changes in the conductivity and ionic charateristics of the source water for the Shark River Slough,Everglades National Park,Florida, U.S.A.

Man-made changes in the hydrological regime of South Florida have significantly altered the conductivity and ionic composition of water in the Shark River Slough system of Everglades National Park. The shift in water inputs from unregulated marsh water flow to regulated delivery of canal water has resulted in a 140% increase in conductivity and 149% increase in total ionic concentration since the early 1960s. Associated with this change has been a 300–400% increase in sodium and chloride concentrations in the waters entering the Shark River Slough of Everglades National Park.     

Salt marsh vegetation of the Western Mediterranean desert of Egypt

The extensive salt marshes in the plains and depressions of the western Mediterranean desert of Egypt were classified into three habitat types: A with shallow water table and high salinity, B with relatively deep water table and high salinity, and C transitional habitats in which salinity and water table are no controlling factors. Fourteen vegetation types were distinguished, each dominated by one or two species.The dominating life forms are chamaephytes in sites of high salinity, and therophytes in sites of low salinity. Spatial and temporal variations in the standing crop biomass were pronounced. The accumulation of material started during spring and reached a maximum in autumn, when photosynthetic activity was maintained to account for transpiration losses.There was a general trend of increasing salinity and concentration of different ions from habitat type A to habitat type C through habitat type B. The periodical variation in the water table was insignificant, while a significant drop in salinity and the concentration of different ions was detected in spring, which was attributed to the diluting effect of rain water during that season.Most species exhibited clear distribution patterns and their a bundance varied significantly along gradients of different factors. Simple correlations between the compositional gradients or the distributional behaviour of species and salinity or the concentration of individual ions were generally low, while correlations with combinations of ions in the form of ratios (notably sodium and potassium adsorption ratos) were higher.During the early stages of succession the building up of soil and the decrease in salinity are the most important factors while at more advanced stages, soil texture and calcium carbonate content become more decisive.Nomenclature follows Täckholm (1974)     

Temporal areal changes of wetlands in the lower reaches of the Tarim River and their responses to ecological water conveyance

及时了解和定量分析荒漠区河岸带湿地月度时序变化趋势及对生态输水过程的响应, 对认识湿地生态修复过程, 改进生态输水策略, 维护湿地生态系统稳定具有重要意义。该文基于Landsat ETM+/TM/OLI和Sentinel 2形成的月尺度的密集长时序遥感数据, 分析2000-2018年塔里木河下游英苏-阿拉干之间的湿地时序变化特征, 并评估湿地变化对生态输水过程的响应。结果表明: 近19年来湿地面积持续增加, 其中2011-2013年和2017-2018年是面积快速增加的时段。不同的单、双通道输水方式和输水量大小解释了喀尔达依湿地与博孜库勒湿地在不同时段增长的快慢。对湿地面积与生态输水量、地下水埋深关系的分析表明, 累计生态输水量的持续增加是近20年来塔里木河下游河岸带湿地扩张的重要因素, 每年大于3.5亿m ³的双通道生态输水, 地下水埋深维持在-5.0- -3.5 m是湿地持续稳定增长的关键。