Ephemeral Wetlands Research Articles

Mapping ephemeral wetlands: manual digitisation and logistic regression modelling in Nelson Mandela Bay Municipality, South Africa

Until recently, little research has been conducted on the distribution and structure of ephemeral systems in semi-arid areas. This information is critical for appropriate wetland management and conservation. The Nelson Mandela Bay Municipality is a semi-arid area along the south-eastern coastline of the Eastern Cape Province of South Africa. The Municipality encapsulates a wide range of geological and geomorphological features as well as vegetation types within an area of some 1950 km2, providing an ideal area for such research. The distribution and abundance of wetlands were defined, and a logistic regression (LR) model was used to establish whether this modelling technique is viable in semi-arid areas with highly variable rainfall patterns. Wetlands were delineated manually using geographical information systems, high-resolution aerial photographs and environmental data. More than 1700 wetland polygons were identified, with 80% of the systems being categorised as depressions, seeps and wetland flats. Unchannelled (8%) and channelled (7%) valley bottom wetlands and floodplain wetlands (5%) were also identified. The wetland database was then used to create a wetland occurrence probability model. There were 19 environmental variables used to develop the LR model, with eight variables used in the final model output. The predictive capacity of the model was good, with an area under curve value of 0.68 and an overall accuracy of 66%. This indicates that probabilistic wetland models are useful in highly variable environments with high numbers of small (<1 ha) wetlands. Such predictive models provide a tool to assist in improving the accuracy of land cover datasets in semi-arid areas, and can be used to inform management decisions on flood risk areas and key conservation zones. In addition, abiotic variables that are significant in the model output provide an indication of the factors influencing wetland functioning in the region.

Evolutionary conservatism explains increasing relatedness of plant communities along a flooding gradient.

Abiotic filters have been found either to increase or reduce evolutionary relatedness in plant communities, making it difficult to generalize responses of this major feature of biodiversity to future environmental change. Here, we hypothesized that the responses of phylogenetic structure to environmental change ultimately depend on how species have evolved traits for tolerating the resulting abiotic changes. Working within ephemeral wetlands, we tested whether species were increasingly related as flooding duration intensified. We also identified the mechanisms underlying increased relatedness by measuring root aerenchyma volume (RAV), a trait which promotes waterlogging tolerance. We found that species-specific responses to flooding explained most of the variation in occurrence for 63 vascular plant species across 5170 plots. For a subset of 22 species, we attributed these responses to variation in RAV. Large RAV specifically increased occurrence when flooding lasted for longer time periods, because large RAV reduced above-ground biomass loss. As large RAV was evolutionarily conserved within obligate wetland species, communities were more phylogenetically related as flooding increased. Our study shows how reconstructing the evolutionary history of traits that influence the responses of species to environmental change can help to predict future patterns in phylogenetic structure.

Restored Wetlands in Mid-Atlantic Agricultural Landscapes Enhance Species Richness of Amphibian Assemblages

AbstractI measured amphibian occurrence in wetlands restored under programs implemented by the U.S. Department of Agriculture's Natural Resources Conservation Service during 2010–2011 in two regions of sites in the Mid-Atlantic region of the United States. One cluster was in Delaware and Maryland on the Delmarva Peninsula and the other was in southeastern Virginia and northeastern North Carolina. I compared larval species richness and relative abundance among 17 restored wetlands, 12 natural wetlands, and 8 wetlands (ditches) in active agricultural fields. Based on larval occurrence, I documented 56 and 60% of the expected number of anurans and salamander species, respectively, known to use ponds and ephemeral wetlands in this region. Of the total number of species encountered, 71% used restored wetlands, 76% used natural wetlands, and 35% used the ditches in agricultural fields. Mean number of species did not differ significantly among the three habitat types due to wide confidence intervals. Total species richness in restored wetlands was not correlated with age (years since restoration), percentage of canopy cover, or percentage of emergent aquatic vegetation. Wetlands restored through Natural Resources Conservation Service and private landowner partnerships, such as those included in this study, support amphibian populations that help mitigate natural habitat loss in these two regions.

Herpetofaunal Communities in Ephemeral Wetlands Embedded within Longleaf Pine Flatwoods of the Gulf Coastal Plain

Abstract Ephemeral wetlands surrounded by Pinus palustris (Longleaf Pine) flatwoods support diverse herpetofaunal communities and provide important breeding habitat for many species. We sampled herpetofauna in 3 pine flatwoods wetlands on Eglin Air Force Base, Okaloosa County, FL, over 2 time periods (1 wetland [1] from 1993 to1995 and 2 wetlands [2 and 3] from 2010 to 2015) using drift fences that completely encircled each wetland. We documented 37, 46, and 43 species of amphibians and reptiles at wetlands 1, 2, and 3, respectively. Herpetofaunal communities were remarkably similar across all 3 wetlands (Sorenson Index values > 0.97) despite sampling that occurred 15–20 years apart on wetlands located approximately 10 km apart. Ambystoma bishopi (Reticulated Flatwoods Salamander), Pseudacris ornata (Ornate Chorus Frog), and Eurycea quadridigitata (Dwarf Salamander), all species of conservation concern, were captured at all 3 wetlands, indicating that these wetlands provide habitat for specialist species....

Assessing the Value of Novel Habitats to Snail Kites through Foraging Behavior and Nest Survival

Abstract Novel ecosystems arise for a variety of reasons, most notably from the introduction of nonnative species. Understanding the interactions between traditional habitats, novel habitats, and species of conservation interest is important when planning successful conservation strategies. In the United States, the snail kite Rostrhamus sociabilis plumbeus is a federally endangered species whose population in Florida has undergone declines within the past decade. While studying the foraging behavior of breeding snail kites on Lake Tohopekaliga (Lake Toho), we discovered the unexpected use of disturbed ephemeral wetlands adjacent to the lake. These wetlands represent a novel habitat for snail kites; they would not have been viable foraging areas prior to the introduction of the exotic island apple snail Pomacea maculata. By examining the differences between snail kite behavior in traditional and novel habitats, we were able to identify some characteristics of novel habitats that may be important in determining their value to snail kites. The novel wetland areas were highly attractive to snail kites, likely because of the high snail capture rates. The survival of snail kite nests occurring within the novel areas appeared to be similar to that of nests occurring in more traditional, nearby areas on Lake Toho. However, whether or not snail kites used novel habitats as nesting areas appeared to be dependent upon water depth and availability of nesting substrate within these areas. The snail kites' dynamic use of the novel habitat demonstrates both the value of a novel ecosystem and the importance of traditional habitats to a species of conservation concern.

Characterization of the cyanobacteria and associated bacterial community from an ephemeral wetland in New Zealand.

New Zealand ephemeral wetlands are ecologically important, containing up to 12% of threatened native plant species and frequently exhibiting conspicuous cyanobacterial growth. In such environments, cyanobacteria and associated heterotrophs can influence primary production and nutrient cycling. Wetland communities, including bacteria, can be altered by increased nitrate and phosphate due to agricultural practices. We have characterized cyanobacteria from the Wairepo Kettleholes Conservation Area and their associated bacteria. Use of 16S rRNA amplicon sequencing identified several operational taxonomic units (OTUs) representing filamentous heterocystous and non-heterocystous cyanobacterial taxa. One Nostoc OTU that formed macroscopic colonies dominated the cyanobacterial community. A diverse bacterial community was associated with the Nostoc colonies, including a core microbiome of 39 OTUs. Identity of the core microbiome associated with macroscopic Nostoc colonies was not changed by the addition of nutrients. One OTU was highly represented in all Nostoc colonies (27.6%-42.6% of reads) and phylogenetic analyses identified this OTU as belonging to the genus Sphingomonas. Scanning electron microscopy showed the absence of heterotrophic bacteria within the Nostoc colony but revealed a diverse community associated with the colonies on the external surface.

Water quality dynamics of ephemeral wetlands in the Piedmont ecoregion, South Carolina, USA

Small ephemeral wetlands are commonly found in the Piedmont ecoregion of the southeastern USA. Ephemeral wetlands have important ecological functions but information about their water quality over its flooding periods is relatively limited. In this study, the water chemistry and physical parameters of three ephemeral wetlands and their nearby water bodies, including first order and second order streams and groundwater in the Piedmont ecoregion of South Carolina, were closely monitored during their flooding periods from January to June 2012. Nutrient and water quality analyses demonstrated the chemistries of wetlands, stream, and groundwater were different from each other in spite of their proximity. Greater concentrations of dissolved organic carbon (DOC) and dissolved organic nitrogen with a major portion in humic-acid-like and fulvic-acid-like fractions were generally found in wetland waters. In contrast, significantly lower DOC concentrations with a greater portion of inorganic nitrogen were observed in stream and groundwater. Electrical conductivity at 25°C (EC25) and temperature measurements showed a greater fluctuation in wetlands, indicating their poor buffering capacity against environmental changes. Results of this field study suggested that these small ephemeral wetlands in the Piedmont Ecoregion have relatively unique biogeochemistry in comparing their adjacent water bodies.

Identification of Woodland Vernal Pools with Seasonal Change PALSAR Data for Habitat Conservation

Woodland vernal pools are important, small, cryptic, ephemeral wetland ecosystems that are vulnerable to a changing climate and anthropogenic influences. To conserve woodland vernal pools for the state of Michigan USA, vernal pool detection and mapping methods were sought that would be efficient, cost-effective, repeatable and accurate. Satellite-based L-band radar data from the high (10 m) resolution Japanese ALOS PALSAR sensor were evaluated for suitability in vernal pool detection beneath forest canopies. In a two phase study, potential vernal pool (PVP) detection was first assessed with unsupervised PALSAR (LHH) two season change detection (spring when flooded—summer when dry) and validated with 268, 1 ha field-sampled test cells. This resulted in low false negatives (14%–22%), overall map accuracy of 48% to 62% and high commission error (66%). These results make this blind two-season PALSAR approach for cryptic PVP detection of use for locating areas of high vernal pool likelihood. In a second phase of the research, PALSAR was integrated with 10 m USGS DEM derivatives in a machine learning classifier, which greatly improved overall PVP map accuracies (91% to 93%). This supervised approach with PALSAR was found to produce better mapping results than using LiDAR intensity or C-band SAR data in a fusion with the USGS DEM-derivatives.

Ephemeral wetland communities of Isoëto-Nano-Juncetea class – new data from south-eastern Poland

Abstract Vegetation data (70 relevés) of ephemeral wetlands collected in both permanent and temporal water basins were analyzed. Numerical classification of the data revealed two distinct subsets, the first comprised communities of Eleocharition ovatae Philippi 1968 alliance, the second combined communities dominated by Alisma lanceolatum, Isolepis supina or Elatine alsinastrum (Alisma lanceolatum group). Phytocoenoses of Eleocharition ovatae were widely distributed in the study area and developed, most frequently, on exposed bottoms of fishponds. This group could be divided into four types of communities. Patches representing Alisma lanceolatum group were found only in mid-field depressions periodically filled with water and concentrated in Volhynian Upland. In this group, two lower vegetation units were distinguished.

The Effects of Crayfish Predation and Vegetation Cover on Tadpole Growth, Survival, and Nonlethal Injury

Abstract Predator–prey interactions play an important role in structuring larval anuran communities in ephemeral wetlands. The type of interaction often depends on the predator species and the complexity of the aquatic habitat. We experimentally evaluated the effects of Panhandle Crayfish (Procambarus evermanni) predation on larval Southern Leopard Frogs (Lithobates sphenocephalus) and larval Ornate Chorus Frogs (Pseudacris ornata). We performed separate experiments for each anuran species and used multiple vegetation treatments to examine whether vegetation could provide refugia from crayfish predation. Our results indicate that crayfish are effective predators of anuran larvae regardless of the amount of vegetation present. Encounters between tadpoles and crayfish often resulted in nonlethal tail injury for tadpoles, suggesting that crayfish predation is prominent in ephemeral wetland communities. Leopard frog tadpoles in predator treatments also grew larger than their counterparts in nonpredator treatm...

What value for pastoral livelihoods? An economic valuation of development alternatives for ephemeral wetlands in eastern Mauritania

Pastoralism in Africa faces new challenges in an era of climate change, despite some improvements in policy and legislative frameworks as well as sporadic investment in pastoral development. There are concerns that pastoralism will not be sustainable in a climate-affected world, and this is seeing the return of policies to settle pastoralists and introduce modern cropping. Pastoralism is not yet understood as a specialisation to take advantage of instability and variability, and as a result, the trend has continued towards replacing pastoralism as a livelihood strategy rather than investing in it. It is in this context that a study conducted in eastern Mauritania between 1999 and 2001 is presented here to demonstrate the economic value of ephemeral wetlands as multi-use resources for pastoralism, agriculture and biodiversity. At the time the study was conducted, governments and aid agencies across the Sahel were targeting wetlands as areas of high development potential to combat poverty and increase food security, converting them from multi-use resources to single-use, arable resources. The study assesses the benefits of multiple-use systems compared to such single-use systems through economic valuation of production from the respective systems. Arable agriculture, livestock rearing and botanical and other natural resources are valued in the case of multiple-use systems and compared to arable production from single-use systems. Multiple-use systems are found to out-perform single-use systems based on annual production values, when opportunity costs and the replacement costs of wetland resources are taken into account. The results also show that the multi-use systems are better adapted to a highly variable climate than single-use arable systems that are highly vulnerable to rainfall fluctuations. This has implications for production in a climate-constrained world where diversification and investment in pastoralism as a strategy for managing variability in drylands will be increasingly important. The methodology used to value the wetlands remains relevant 15 years later, as governments, aid agencies and international organisations develop policies to guide pastoralism in dryland systems that are becoming increasingly variable and unpredictable in the face of climate change.

Specialist and generalist amphibians respond to wetland restoration treatments

ABSTRACTAvailable habitat within a landscape is often more limited for specialist species than for generalists. Therefore, specialists are potentially more vulnerable to extinction. The goal of our study was to better understand the ephemeral wetland habitat associations of specialist and generalist amphibians within a longleaf pine landscape in the southeastern United States. We also sought to determine specialist (e.g., oak toad [Anaxyrus quercicus], Maybee's salamander [Ambystoma maybeei], pine woods treefrog [Hyla femoralis], carpenter frog [Lithobates virgatipes]) and generalist (e.g., spotted salamander [Ambystoma maculatum], Cope's gray treefrog [Hyla chrysoscelis], southern leopard frog [Lithobates sphenocephalus]) species’ responses to specific habitat restoration treatments. From 2005–2010, we examined the relationship between aquatic specialist and generalist amphibian species occupancy and wetland vegetation structure. We measured vegetation and amphibian responses to prescribed fire and vegetation mulching (a fire surrogate), plus a combination of mulching and burning. Untreated controls were wetlands that had not burned for 4–15 years. We combined data from this study and a previous study to elucidate patterns in amphibian assemblages in relation to fire history. Specialist relative species richness was highest when canopy openness was high and leaf litter depth was low, conditions best achieved by mulching plus burning. Some specialist species were not detected in wetlands with &gt;8 years since fire, and some generalist species were not detected in wetlands with &lt;2 years since fire, indicating that as vegetation structure changes with time since fire, there is a corresponding shift in the amphibian assemblage. Important patterns in species distributions can be overlooked if relationships to environment and responses to habitat change are too generalized and do not account for shifts in community composition. For conservation of longleaf pine specialist species, we recommend that uplands continue to be prescribed‐burned on a 1–3‐year return interval. Burning should occur during the early growing season when possible to maximize the probability that wetland basins burn. In cases where species of high conservation value are at imminent risk of extinction, we recommend a combination of mulching and burning to most quickly restore suitable habitat structure. © 2016 The Wildlife Society.

Calling phenology and detectability of a threatened amphibian (Litoria olongburensis) in ephemeral wetlands varies along a latitudinal cline: Implications for management

AbstractAmphibian reproductive biology and activity are highly sensitive to environmental cues. For amphibian conservation in the face of climate change, a clear priority is to investigate impacts of variable weather on breeding activity and detectability. This study assessed variation in the phenology, intensity and detectability of calling for a threatened temporary wetland breeding species, Litoria olongburensis. Acoustic and visual surveys were conducted monthly from August 2009 to July 2011 over the species latitudinal range in eastern Australia. Calling phenology of L. olongburensis varied spatially and temporally within and among latitudinal clusters. Detectability of frogs also varied among months and transects, and also with the type of survey conducted (visual vs. acoustic). Air temperature was a strong predictor for the onset of the calling season (early spring); however, peaks in calling abundances were primarily driven by monthly accumulated rainfall. The duration of the calling season varied among latitudinal clusters, becoming narrower moving south, reflecting clinal variation in weather patterns. This study presents a framework for amphibian species management using a combination of survey techniques and the climatic conditions influencing detectability. Applied along the latitudinal gradient, it provides data for predicting the likely impacts of climate change on amphibian activity and reproduction.

The use of environmental tracers to determine focused recharge from a saline disposal basin and irrigation channels in a semiarid environment in Southeastern Australia

Summary Lake Tutchewop in southeastern Australia is a former ephemeral wetland that has been used as a saline disposal basin since 1968, forming part of the salinity management of the Murray River. The extent of saline focused recharge from Lake Tutchewop and fresh recharge from nearby unlined irrigation channels was determined using pore water and groundwater stable isotope and major ion chemistry, which were able to separate the influence of lake water, irrigation water and regional groundwater. In ∼45 years, saline water from Lake Tutchewop has infiltrated only up to 165 m from the lake edge in most directions, due to the underlying relatively impermeable clay-rich sediments, and a maximum of 700 m due to preferential groundwater flow along a sandy palaeochannel. The saline leakage has had limited, if any, impact on surrounding agricultural land use. Fresh water leakage from unlined irrigation channels extends up to 10 m deep, validating the current program to replace these channels with pipelines. This study demonstrates that focused recharge from different sources can be positively identified where the recharge waters have distinctive compositions, and that underlying clay-rich sediments restrict the extent of seepage. Therefore, management of focused recharge sources, particularly those that could decrease groundwater quality, requires a detailed knowledge of both the groundwater composition around the site and the underlying geology.

Vernal Pool Inventory and Classification at Pictured Rocks National Lakeshore, Michigan, USA

ABSTRACT: Vernal pools occur in the glaciated forests of northeastern North America and provide critical breeding and foraging habitat for amphibian and mammal species. Protection for these ephemeral wetlands is not federally mandated, placing them at risk for habitat fragmentation and making them more vulnerable to impacts of climate change. Unlike the northeastern United States, limited information about vernal pools exists for the Great Lakes region, and there is a lack of information about techniques to identify and classify vernal pools using remote sensing and field surveys. At Pictured Rocks National Lakeshore, Michigan, USA, our objectives were to locate vernal pools using true-color, spring leaf-off aerial photography at the 1:12,000 scale, classify vernal pools using modified geomorphological classification systems, and determine landscape associations with soil series and cover type GIS datasets. From the 214 water features identified and categorized via aerial photography, two (water with cano...

Mapping and Hydrologic Attribution of Temporary Wetlands Using Recurrent Landsat Imagery

In areas with a high density of ephemeral wetlands, traditional mapping protocols may underestimate occurrence of wetlands when single-date base-imagery is utilized. In the Pleistocene Sand Dunes Ecoregion in Oklahoma, National Wetland Inventory (NWI) maps created using base-imagery from a dry year omitted large numbers of ephemeral wetlands. To improve the likelihood of capturing inundated depressions, we classified water pixels from 51 Landsat images (3 images per year: pre/early, peak, and late/post growing season) from 1994 to 2011. Several image classification methods were tested but decision tree analysis with training pixels from multi-season imagery provided the greatest accuracy. Accuracy was determined through manual comparison of two Landsat images with concurrent aerial imagery (Kappa =0.96 and 0.93 for the two images). Wetland polygons were created from water/non-water rasters and given hydroperiod designations based on the number of inundated periods. Landsat-derived wetland maps identified 3156 wetland units, 718 more than the original 1980s NWI, with only 33.9 % agreement between the two maps. Finally, one meter LiDAR data were combined with classified Landsat images to determine the volume of water in wetlands during each image date. These wetland maps can assist with estimating the availability of inundated habitat during wet, dry, and average rainfall periods.

Hindcasting Historical Breeding Conditions for an Endangered Salamander in Ephemeral Wetlands of the Southeastern USA: Implications of Climate Change.

The hydroperiod of ephemeral wetlands is often the most important characteristic determining amphibian breeding success, especially for species with long development times. In mesic and wet pine flatwoods of the southeastern United States, ephemeral wetlands were a common landscape feature. Reticulated flatwoods salamanders (Ambystoma bishopi), a federally endangered species, depend exclusively on ephemeral wetlands and require at least 11 weeks to successfully metamorphose into terrestrial adults. We empirically modeled hydroperiod of 17 A. bishopi breeding wetlands by combining downscaled historical climate-model data with a recent 9-year record (2006–2014) of observed water levels. Empirical models were subsequently used to reconstruct wetland hydrologic conditions from 1896–2014 using the downscaled historical climate datasets. Reconstructed hydroperiods for the 17 wetlands were highly variable through time but were frequently unfavorable for A. bishopi reproduction (e.g., only 61% of years, using a conservative estimate of development time [12 weeks], were conducive to larval development and metamorphosis). Using change-point analysis, we identified significant shifts in average hydroperiod over the last century in all 17 wetlands. Mean hydroperiods were shorter in recent years than at any other point since 1896, and thus less suitable for A. bishopi reproduction. We suggest that climate change will continue to impact the reproductive success of flatwoods salamanders and other ephemeral wetland breeders by reducing the number of years these wetlands have suitable hydroperiods. Consequently, we emphasize the importance of conservation and management for mitigating other forms of habitat degradation, especially maintenance of high quality breeding sites where reproduction can occur during appropriate environmental conditions.

New bird records from the Fortescue Marsh and nearby claypans, Pilbara bioregion, Western Australia

The Fortescue Marsh in the Pilbara bioregion, Western Australia, is an extensive ephemeral wetland that fills episodically. It is considered as a potential Ramsar site and is recognised as a nationally important wetland and an Important Bird Area. We surveyed birds at 21 sites on the Fortescue Marsh and a further 23 sites (44 sites in total), including nearby claypans Coondiner Pool and Mungthannannie Pool, in the Fortescue Valley over 12 days in March–April and July 2012. A total of 100 bird species (34 waterbird and 66 landbird species) was recorded during the survey. A further 86 bird species (including 28 waterbird species and 58 landbird species) were recorded for this area from searches of databases and the literature (total of 187 species; 62 waterbirds). New and significant observations during the survey included the first breeding record of Australian Shelduck Tadorna tadornoides for the Pilbara, the first breeding records on the Marsh of Black-tailed Native-hen Tribonyx ventralis and Caspian Tern Hydroprogne caspia, and the first record of Australian Painted Snipe Rostratula australis for the Fortescue Valley. Despite this area’s importance to breeding and visiting waterbirds, the birds of the Fortescue Marsh remain surprisingly under-studied. We highlight some significant but overlooked literature records of waterbirds on the Marsh. Further ground and aerial surveys, and ongoing monitoring of this region would be valuable.

English

Abstract While ephemeral wetlands contribute significantly to regional freshwater biodiversity, their role in supporting threatened and imperiled species of crayfish is not widely recognized. As the center of global crayfish biodiversity, the southeastern United States (US), and the state of Alabama (AL) in particular, are important focal areas where information is needed to develop understanding of habitat constraints determining the distributions of crayfish species. To this end, we documented crayfish species associated with ephemeral wetlands and associated wetland habitats that have been traditionally under sampled. Fifteen species of crayfish were documented among 96 survey sites. This assemblage included three Alabama state-listed Priority 1 species [Cambarellus diminutus Hobbs, Fallicambarus burrisi Fitzpatrick, Procambarus viaeviridis (Faxon)] and five Priority 2 species [Hobbseus prominens (Hobbs), Orconectes lancifer (Hagan), Procambarus evermanni (Faxon), P. leconti (Hagan), P. marthae Hobbs]. An undescribed species of Cambarellus (“sp. A”) was also documented, and will presumably be eventually designated a Priority 1 species in Alabama due to its restricted distribution and apparent endemism. Ten species of crayfish were documented from ephemeral wetlands, including four Priority 1 and 2 species [Cambarellus sp. A (presumed Priority 1 species), H. prominens, P. marthae, P. viaeviridis]. Most populations of Priority 1 and 2 species we documented are within the 100-year floodplain of the Black Warrior River. Ephemeral wetlands and associated wetland habitats within the floodplains of large rivers thus appear to be vital habitat for threatened and imperiled crayfish in Alabama. Our results suggest that future crayfish surveys should include sampling of these important but often overlooked habitats.

Vascular plant assemblages of ephemeral wetland vegetation along the Mediterranean-temperate gradient in Chile

Actualmente se conoce muy poco sobre la composicion floristica y la distribucion geografica de humedales temporales en Chile mediterraneo. Con el fin de llenar este vacio, se realizaron 73 inventarios floristicos en el gradiente mediterraneo- templado de Chile (31-44°S). Ademas, se llevo a cabo una busqueda bibliografica exhaustiva de inventarios fitosociologicos en publicaciones cientificas, incluyendo algunos inventarios de la parte argentina de la Cordillera de los Andes. Se obtuvo una matriz con 228 observaciones y 269 especies. Se aplico una clasificacion jerarquica para generar ensambles de co- ocurrencia. Dichos ensambles fueron comparados con grupos de especies diagnosticas definidas a priori, con formas de vida y tipos de origen (especies introducidas en Sudamerica vs especies nativas). Para determinar patrones de distribucion geografica y climatica, se extrajeron variables del modelo WorldClim y se aplicaron a un analisis de componentes principales (PCA). Segun la clasificacion jerarquica se determinaron siete ensambles de especies con una alta correspondencia a los grupos definidos a priori (P < 0,01), sin embargo con un nivel relativamente bajo de asociacion (indice V de Cramer = 0,49). En la vegetacion estudiada dominan las especies nativas sobre las introducidas, lo que sugiere un bajo riesgo de extincion por competencia con especies introducidas adaptadas a este tipo de ambientes. La forma de vida anual esta sobrerrepresentada en la mayoria de los ensambles. Pese al enorme gradiente de temperatura y precipitacion incluido en el rango de las muestras, los ensambles se distribuyen a lo largo de todo este gradiente, apoyando la hipotesis de azonalidad (indiferencia al macro-clima). Los ensambles definidos en este trabajo pueden ser potencialmente utilizados para posteriores clasificaciones supervisadas con el fin de definir tipos de comunidades vegetales en lagunas temporales.