Upland Species Research Articles

The legacy of pipeline installation on the soil and vegetation of southeast Wisconsin wetlands

Installation of large-scale infrastructure, including pipelines, has the potential to damage soil and vegetation in wetlands within the path of construction by compacting soil, altering hydrology, decreasing plant diversity, and facilitating invasions of unwanted species. We sampled soil and vegetation in seven southeast Wisconsin wetlands eight years after they were crossed by a natural gas pipeline to compare areas inside and outside the pipeline corridor (land within 12 m of the pipe, where construction was permitted). Soils consistently showed evidence of compaction and hydrologic alteration. Across sites the pipeline corridor soil had 63% higher bulk density, 13% lower depth to refusal and 19% lower soil moisture ( P < 0.0001 for all). In contrast, the diversity and quality of vegetation (species richness, Simpson's dominance, and mean coefficient of conservatism) inside and outside the pipeline corridor varied among sites. A site with relatively high native plant diversity outside the pipeline corridor showed lower richness and higher dominance inside the corridor ( P < 0.05 for both); whereas, in sites that were strongly dominated by invasive grasses, Phalaris arundinacea and Glyceria maxima, vegetation either showed no change or positive changes in diversity and quality in the pipeline corridor. We suspect the net positive effects of pipeline installation on vegetation in some sites owes to (1) the presence of monotype-forming invasive species outside the pipeline corridor in those sites, (2) post-construction planting and subsequent maintenance-mowing of the pipeline corridor, and (3) colonization within the corridor by additional species (mostly upland species). However, our vegetation results do not undercut the overall negative impacts of pipeline installation on wetland soils, which were still observable eight years after construction. While soil might be the more consistent indicator of pipeline impacts in wetlands, the site-specific and sometimes-positive response of vegetation highlights (1) the need for better pre-construction surveys, so that impacts can be minimized at high-quality sites and (2) the potentially high return on post-construction planting and maintenance.

Effects of River Restoration on Riparian Biodiversity in Secondary Channels of the Pite River, Sweden

Between 1850 and 1970, rivers throughout Sweden were channelized to facilitate timber floating. Floatway structures were installed to streamline banks and disconnect flow to secondary channels, resulting in simplified channel morphologies and more homogenous flow regimes. In recent years, local authorities have begun to restore channelized rivers. In this study, we examined the effects of restoration on riparian plant communities at previously disconnected secondary channels of the Pite River. We detected no increase in riparian diversity at restored sites relative to unrestored (i.e., disconnected) sites, but we did observe significant differences in species composition of both vascular plant and bryophyte communities. Disconnected sites featured greater zonation, with mesic-hydric floodplain species represented in plots closest to the stream and mesic-xeric upland species represented in plots farthest from the stream. In contrast, restored sites were most strongly represented by upland species at all distances relative to the stream. These patterns likely result from the increased water levels in reconnected channels where, prior to restoration, upland plants had expanded toward the stream. Nonetheless, the restored fluvial regime has not brought about the development of characteristic flood-adapted plant communities, probably due to the short time interval (ca. 5 years) since restoration. Previous studies have demonstrated relatively quick responses to similar restoration in single-channel tributaries, but secondary channels may respond differently due to the more buffered hydrologic regimes typically seen in anabranching systems. These findings illustrate how restoration outcomes can vary according to hydrologic, climatic and ecological factors, reinforcing the need for site-specific restoration strategies.

Understanding the relative roles of disturbance and species interactions in shaping Mississippi River island plant communities

In order to better understand the factors governing community assembly on riverine islands, we conducted a greenhouse experiment that examined the effects of species interactions in combination with flooding that mimicked hydrologic gradients found on Mississippi River islands. Specifically, we examined the effects of inter and intra-specific competition and three disturbance treatments (drained, drought, and flood) on the growth performance of three island-ubiquitous herbaceous plant species (Amaranthus palmeri, Cyperus strigosus. and Xanthium strumarium). We predicted a decrease in interspecific competitive effects in disturbance treatments. Specifically, we expected A palmeri to be most affected by flooding treatment based on its facultative upland status suggesting that it should be a poor tolerator of flooded conditions. X. strumarium and C. strigosus both facultative wetland species in their status, should tolerate flooding, but we predict that C. strigosus should have greater stress tolerance due to its perennial life history. Because we find these species coexisting at the same elevation zones on riverine islands, we also predicted stronger intraspecific competition effects. Our results indicate that disturbance indeed affected competitive interactions, but the effects were species-specific. X. strumarium showed stronger competitive effects when grown with conspecifics while C. strigosus experienced greater competition with heterospecifics under drought treatments. Based on its wetland indicator status and life history characteristics, we expected A palmeri to exhibit a facilitative effect, as it is typically an upland species, but instead it was impacted most by interspecific competition. Our study indicates that factors other than competition, facilitation, and flood tolerance (e.g., priority effects) may be controlling island plant community dynamics, further studies are required.

Analysis of Plant Species Community within Upland Wetlands at Mt. Ilgwang

This study characterized the full range of vegetation in a upland wetland (marshland) in Korea. Classified community types were used to describe vegetation at the marshland and adjacent areas. The communities contained 44 species of vascular plants and all species were identified into four plant community types. The Rhododendron yedoense f. poukhanense type and Lespedeza cyrtobotrya type had a high representation infacultative upland species (FU) and obligate upland species (OU), respectively. The monocot type was dominant in marshland by Miscanthuns saccharifloruc and contained 14 species. Together the three areas contained four species, with the strongest indicator species being Ranunculus acris var. nipponicus, Rhododendron yedoense f. poukhanense, Hemerocallis fulva, and Miscanthuns sinensis var. purpurascens. Shannon-Weaver index of diversity also varied among the community types (F = 18.9, df = 2), with the types FU having significantly higher value (3.467) than the others (1.125 for type FW and 1.239 for type OU).

Bat-species richness in the Pantanal floodplain and its surrounding uplands

We studied the bat fauna of the Pantanal floodplain and its surrounding plateaus in Mato Grosso do Sul, Brazil, based on the scientific collection at Universidade Anhanguera-Uniderp and on the Projeto Morcegos do Pantanal data bank at UFMS, comprising 9,037 captures of 56 species recorded from 1994 to 2007. The Pantanal surveys were carried out in the Nhecolândia, Aquidauana, Miranda, and Paraguai sub-regions; the uplands surveys took place in the Maracaju, Bodoquena, and Urucum formations. Bat specimens were mist-netted over 376 nights in 35 sites, predominantly near fruiting trees, bat shelters, and forest patches. In the floodplain 46 species were recorded (n = 6,292 individuals), and 44 species were found in the uplands (n = 2,745 individuals). Six families were recorded: Phyllostomidae (30 species), Molossidae (12 species), Verpertilionidae (nine species) Noctilionidae (two species), Emballorunidae (two species) and Mormoopidae (one species). The bat fauna was predominantly composed of insectivore (32) and frugivore (15) species. The frugivorous Artibeus planirostris (n = 3,101 individuals) was the commonest species in floodplain and uplands. Other common species were Myotis nigricans (n = 762), Molossus molossus (n = 692), Noctilio albiventris (n = 681), Platyrrhinus lineatus (n = 633), Sturnira lilium (n = 461), Carollia perspicillata (n = 451), Glossophaga soricina (n = 436), Artibeus lituratus (n = 320), and Desmodus rotundus (n = 281). In the floodplain there were three insectivores among the most common species, contrasting with the uplands dominated by the frugivores. The diversity for the 35 sites assembled (H' = 2.5) is comparable to that recorded for tropical forests. The bat fauna presented here represents 34% of the Brazilian bat species, and 62% of species reported for the Upper Paraguay River Basin. Additionally, five species are reported for the first time in Mato Grosso do Sul.

Ecosystem response to removal of exotic riparian shrubs and a transition to upland vegetation

Understanding plant community change over time is essential for managing important ecosystems such as riparian areas. This study analyzed historic vegetation using soil seed banks and the effects of riparian shrub removal treatments and channel incision on ecosystem and plant community dynamics in Canyon de Chelly National Monument, Arizona. We focused on how seeds, nutrients, and ground water influence the floristic composition of post-treatment vegetation and addressed three questions: (1) How does pre-treatment soil seed bank composition reflect post-treatment vegetation composition? (2) How does shrub removal affect post-treatment riparian vegetation composition, seed rain inputs, and ground water dynamics? and (3) Is available soil nitrogen increased near dead Russian olive plants following removal and does this influence post-treatment vegetation? We analyzed seed bank composition across the study area, analyzed differences in vegetation, ground water levels, and seed rain between control, cut-stump and whole-plant removal areas, and compared soil nitrogen and vegetation near removed Russian olive to areas lacking Russian olive. The soil seed bank contained more riparian plants, more native and fewer exotic plants than the extant vegetation. Both shrub removal methods decreased exotic plant cover, decreased tamarisk and Russian olive seed inputs, and increased native plant cover after 2 years. Neither method increased ground water levels. Soil near dead Russian olive trees indicated a short-term increase in soil nitrogen following plant removal but did not influence vegetation composition compared to areas without Russian olive. Following tamarisk and Russian olive removal, our study sites were colonized by upland plant species. Many western North American rivers have tamarisk and Russian olive on floodplains abandoned by channel incision, river regulation or both. Our results are widely applicable to sites where drying has occurred and vegetation establishment following shrub removal is likely to be by upland species.

Seasonal variation in the apparent abundance of breeding birds in arctic‐alpine habitats in Scotland: implications for their survey and monitoring

Capsule Low and variable encounter rates of birds in fragmented arctic‐alpine habitats add difficulty to monitoring their breeding populations. Aims To quantify seasonal variation in the encounter rates (apparent abundance) of breeding birds in arctic‐alpine habitats in Scotland. Methods Birds were sampled from 15 repeated linear transects between April and August in 2005 and 2006. glmms (and for scarcer species glms) were used to investigate how the apparent abundance of different species varied between months and years. Results Three arctic‐alpine specialists (Rock Ptarmigan, Eurasian Dotterel and Snow Bunting) were recorded. The 24 other species recorded included more widely distributed upland species, generalists that also used arctic‐alpine habitats and also some transient species from lower altitude. Overall encounter rates were low (only exceeding 1 bird km−1 in any month for one species; Meadow Pipits) with marked variation between months. The pattern of seasonal variation in encounter rates varied markedly between species. Conclusions Low encounter rates and marked variation in apparent abundance will render more difficult efforts to monitor birds in marginal and fragmented areas of arctic‐alpine habitats. Particularly relevant is the potential for changes in the timing of breeding and seasonal movements to influence encounter rates and be falsely interpreted as changes in actual abundance. Monitoring in arctic‐alpine habitats should include both specialist and non‐specialist birds of that habitat, as the latter may be more numerous and, therefore, provide supplementary evidence of temporal or seasonal change.

Developing site scale projections of climate change in the Scottish Highlands

With recent warming trends projected to amplify over the coming century, there are concerns surrounding the impacts on mountain regions. Despite these concerns, global (GCMs) and regional climate models (RCMs) fail to capture local scale-dependent controls on upland climates. A modelling framework combining climate model outputs and station data is presented and used to explore possible future changes to temperature with altitude in the Scottish Highlands. The approach was extended by modelling shifts in seasonal isotherm values associated with existing vegetation zones. To achieve this, temperature lapse rate models (LRMs) were applied to 1961–1990 baseline (BL) observed station data for selected stations in the eastern Highlands using seasonally representative lapse rate values (LRVs) derived from paired station values. Tests against 3 upland station records ranging from 663 to 1245 m indicated a credible model performance for the mean seasonal maximum (Tmax) and minimum (Tmin) BL values evaluated. Following derivation of seasonal isotherm values for the present upper limit of vegetation zones via the LRMs, selected scenario data outputs from the corresponding Hadley Centre RCM (HadRM3H) 50 × 50 km grid cells were used to project future changes to BL values via the LRMs. The findings suggest substantial shifts in the isotherm associated with each zone for the scenarios selected, with shifts in Tmin more marked than those for Tmax, although substantial uncertainties remain. Following an exploration of the results for the region, we suggest that a refinement to the approach linked to a wider modelling effort incorporating other important controlling variables for upland species could inform future management initiatives for mountain areas more generally.

Long‐term impact of changes in sheep Ovis aries densities on the breeding output of the hen harrier Circus cyaneus

Summary1. Livestock grazing is an important form of land use across the globe and changes in grazing pressure can have profound effects on vertebrate populations.2. In Scotland, over the last decade sheep numbers in many areas have declined from historically high levels, providing an opportunity to explore the implications of these declines for biodiversity.3. The hen harrier Circus cyaneus is a bird of high conservation importance in the UK, and a species that may be heavily influenced by the indirect effects of sheep on habitat and prey. The hen harrier population on the Orkney Islands in Scotland has been monitored since 1975 and represents an ideal case study for considering the impact of sheep de‐stocking on a key predator.4. Declines in the harrier population were associated with a doubling in sheep numbers between the early 1980s and the late 1990s. Subsequently, as sheep numbers have fallen the harrier population has recovered. These changes indicate an association but no clear mechanism, so we tested whether reductions in sheep numbers have led to increases in harrier prey or preferred foraging habitat. We then tested whether breeding output over the last 33 years correlates with sheep stocking levels or variation in weather conditions (rainfall and temperature).5. Orkney sheep numbers declined by about 20% between 1998 and 2008. Surveys in 1999/2000 and repeated in 2008 showed increases in rough grassland, the preferred harrier foraging habitat, and increases in a key prey species, the Orkney vole Microtus arvalis orcadensis.6. Overall, hen harrier breeding output over the last 33 years was significantly negatively correlated to both sheep abundance and spring rainfall.7. Synthesis and application. This study provides strong evidence for the consequences of changes in sheep numbers on a top predator. Our results indicate that reductions in sheep numbers are likely to prove beneficial for some upland species, particularly small mammals and their predators.

Modelling the impacts of reservoir operations on the downstream riparian vegetation and fish habitats in the Lijiang River

River flow regulations have great impact on the downstream aquatic ecosystem. It is important to investigate the response of target species to the changes in hydrological regimes so that we can explore possible remediation measures. Ecohydraulics models that integrate hydrodynamics processes and ecological processes have been shown to be efficient in achieving these objectives. This study developed an integrated model which combined a two-dimensional hydrodynamic module with a vegetation evolution module and a fish habitat module. Owing to the ability to represent spatial heterogeneity and local interactions, the vegetation module used an unstructured cellular automata (UCA) approach. To describe the ambiguous relations between the physical conditions and habitat suitability, a fuzzy inference method was applied to the fish habitat module. The developed model was applied to a compound channel of the Lijiang River in southwest China, which has been greatly affected by the flow regulations of the Qingshitan Reservoir for navigation purposes. Through scenario simulations, the effects of flow regulation on riparian vegetation and fish habitat were analyzed. According to the results, water releases in the dry season imposed negative effects on the downstream semi-aquatic plant Rumex maritimus (R. maritimus) and Polygonum hydropiper (P. hydropiper) and favored the upland species Leonurus heterophyllus (L. heterophyllus). Regarding to the effects on fish Spinibarbus hollandi (S. hollandi) the results showed that water releases increased the suitability of the spawning conditions, especially during wet and dry years, but had little impact on the overwintering conditions.

The role of altitude and associated habitat stability in determining patterns of population genetic structure in two species of Atalophlebia (Ephemeroptera: Leptophlebiidae)

Summary 1. Previous studies have identified lowland areas as barriers to gene flow (dispersal) between distinct mountain ranges in montane species of aquatic insects. In this study, we investigated the population genetic structure of two closely related Atalophlebia (mayfly) species inhabiting lowland areas of south-east Queensland, Australia, with the expectation of widespread gene flow throughout the low-altitude environment and associated homogeneous genetic structure. 2. In particular, we asked whether species with lower-altitude distributions demonstrate greater spatial distribution of mtDNA (COI) alleles than the upland species studied previously. This pattern would be expected if good dispersal ability is associated with population persistence in these drought-prone habitats. 3. The two species demonstrated contrasting genetic population structure. Atalophlebia sp. AV13 D revealed strong population structure, with populations on each side of the low-altitude area isolated from each other for a long time (c.350 kya), and the presence of an isolation-by-distance pattern over relatively small geographical distances (<40 km). In contrast, Atalophlebia sp. AV13 A was panmictic at the scale investigated (≤160 km), with no history of past population fragmentation. 4. Examination of sample distribution along the altitudinal gradient reveals that Atalophlebia sp. AV13 D may have a more upland distribution (associated with greater habitat stability) than previously supposed, while Atalophlebia sp. AV13 A inhabits more xeric lowland areas, where freshwater habitats are less stable. We consequently hypothesise that these contrasting genetic population structures result from differences in habitat stability along the altitudinal gradient, only species with good dispersal ability being able to persist in unstable habitats. These findings may be applicable to other regions of the globe where habitat instability is associated with altitudinal gradients.

The role of dispersal in shaping plant community composition of wetlands within an old‐growth forest

Summary 1. Dispersal ability can influence the importance of dispersal relative to other processes organizing metacommunities, such as species sorting among habitats along environmental gradients. 2. We compare plants with different dispersal modes and habitat affinities, evaluating the roles of environmental and spatial controls on plant community composition in 128 wetlands within 10 km2 of old‐growth maple–beech forest in southern Québec, Canada. 3. We address two hypotheses. First, we ask whether species with short‐distance dispersal mechanisms are more dispersal‐limited than species with adaptations for long‐distance dispersal. Second, because wetland habitats are more fragmented than upland habitats in this forested area, we test the hypothesis that wetland species are more dispersal‐limited than upland species growing in the same wetlands (e.g. on hummocks within a swamp). 4. Variation partitioning based on constrained ordinations showed that the distributions of species with short‐distance dispersal mechanisms related more strongly to spatial factors than the distributions of long‐distance dispersers, supporting the interpretation that these species are more dispersal‐limited. The distributions of short‐distance dispersers also showed finer‐scale spatial patterns than the distributions of long‐distance dispersers. 5. Distributions of wetland species related more strongly to environmental conditions than the distributions of upland species growing in the same wetlands, suggesting that wetland species are actually less dispersal‐limited than upland species. Wetland and upland species had similar patterns of spatial variation in community composition. 6. Synthesis. The processes of dispersal limitation and species sorting along environmental gradients have differential importance to plants that grow within the same communities, but differ in dispersal ability and habitat affinity. This result emphasizes the impact of dispersal ability on the organization of metacommunities.

Effects of changing channel morphology on vegetation, groundwater, and soil moisture regimes in groundwater-dependent ecosystems

Channel incision, channel widening, and excessive floodplain sedimentation are major causes of riparian ecosystem degradation across the country. Although the causes and consequences of these processes vary significantly, the resulting morphology in all cases results in a lower stream stage relative to the floodplain surface for any given discharge. This change in channel morphology alters surface water–groundwater interactions between the stream and the riparian aquifer and affects the soil moisture and groundwater regimes differentially across the floodplain. The distribution of vegetation is altered as the hydrologic regime shifts between the hydrologic niches of potential species. We simulate the hydroecologic response of a groundwater-dependent ecosystem on the floodplain of an archetypical watershed under three scenarios representing changes in channel morphology: a base case, a widened channel case, and an incised channel case. Stochastically-driven synthetic rainfall records are used to drive a rainfall–runoff model of the archetype watershed. The resulting hydrograph is transformed to stage via Manning's equation for the three channel morphologies considered. This stage record is used as a boundary condition for a finite-element model simulating 2-dimensional, variably-saturated groundwater flow in the riparian aquifer. The model predicts soil moisture and groundwater regimes lateral to the channel. The 7-day moving average high water level is determined for ten growing seasons and used to predict the distribution of three species across the floodplain. Plant frequency is predicted for Carex emoryi (an obligate wetland species), Carex crawei (facultative wetland species), and Carex duriuscula (a facultative upland species) for each of the channel morphologies considered. The frequency is predicted using existing nonlinear parametric species response curves determined empirically for these species using direct gradient analysis. Results show the sensitivity of the distribution of vegetation on floodplains to channel morphologic changes. Our linked hydrologic and ecological model provides a solid framework for considering potential hydroecologic impacts of channel disturbance and/or restoration on vegetation communities which are often affected by channel degradation and targeted in restoration efforts.

Changes in riparian forest composition along a sedimentation rate gradient

Riparian forests are highly valued for maintaining water quality through the retention of sediments and nutrients. They also provide some of the most diverse and species-rich habitats in the world. What is largely unknown, however, is how sediment deposition affects plant community composition in these forests. The objective of this study was to examine changes in plant community composition across a gradient of increasing rates of sedimentation in riparian forests in the southeastern Coastal Plain, USA. Seventeen plots were established within riparian forests receiving between 0 and 5.5 cm year−1 of sediment deposits. Species density and biomass estimates were collected annually from 2002 to 2006 for overstory and mid-story plant species within each plot. Percent cover and nested frequency of understory plant species were determined annually during 2004–2006. Measures of community composition in the understory, mid-story, and overstory layers of forests were compared to changes in environmental factors associated with increased sedimentation. In the understory, annual, exotic, and upland species had higher importance values in plots receiving high sediment deposition. The densities of shade-intolerant and N-fixing species in the mid-story also increased with increasing sedimentation rates. Increased overstory mortality was associated with high sedimentation rates, though increases in understory light levels in these gaps were not the main driver of understory species changes. Edaphic factors, such as soil texture, moisture, and temperature, were significantly correlated to species composition in all three forest layers, suggesting that changes in soil physical structure due to sedimentation may drive community-level changes in these forests.

High resilience of bryophyte assemblages in streamside compared to upland forests

Landscape heterogeneity causes spatial variation in disturbance regimes and resilience. We asked whether the resilience of bryophyte (liverwort and moss) assemblages to clear-cutting differs between streamside and upland boreal forests in northern Sweden. We hypothesized that bryophyte survival and recolonization rates are higher in streamside areas, thus raising resilience. Conversely, disturbance-intolerant but also invading species should be more frequent here, potentially reducing resilience. In each of 18 sites, we compared two 0.1-ha plots (one streamside and one upland) located in old forest that had never been clear-cut with two matching plots in young stands established after clear-cutting of old forests 30-50 years earlier. We used the magnitude of the difference in assemblages between old and young stands as a measure of change and, therefore, resilience (large difference implying low resilience). Species assemblages were more resilient in streamside than in upland forests. Species composition changed significantly in upland but not in streamside forests. Reductions in species richness were more pronounced in upland forests for total richness and for eight subgroups of species. Two results indicated lower survival/recolonization in upland forests: (1) species had a stronger association with old stands in upland areas, and (2) among species present in both the old streamside and old upland plot in a site, fewer appeared in the young upland than in the corresponding streamside plot. Simultaneously, a higher proportion of species invaded streamside areas; 40 of the 262 species encountered in streamside forests increased their occupancy by two or more sites compared to only two of 134 species in uplands. We suggest that in boreal forests spatial variation in resilience of assemblages of forest organisms intolerant of canopy removal is related to factors governed mainly by topography. More generally, we argue that landscape-scale variation in resilience of assemblages is influenced by spatial variation in (1) stress and resource availability, (2) number of disturbance-intolerant species, and (3) magnitude of environmental changes brought about by a disturbance with a specific intensity. We also suggest that rapid recovery in the short term does not necessarily imply higher long-term ability to return to the pre-disturbance state.

The influence of environment and life‐history traits on the distribution of genes and individuals: a comparative study of 11 rainforest trees

This study investigates patterns of genetic connectivity among 11 co-distributed tropical rainforest tree species from the genus Elaeocarpus across a biogeographic barrier, the Black Mountain Corridor (BMC) in the Australian Wet Tropics (AWT). We analysed a combination of allelic and flanking region sequence data from microsatellite markers, and evaluated the relative influence of environmental preferences and functional traits on genetic diversity and gene flow. The results indicate that only in three species geographic structuring of haplotype distribution reflects a north vs. south of the BMC pattern. Environmental factors linked with altitude were recognized as affecting genetic trends, but the selective processes operating on upland species appear to be associated with competitiveness and regeneration opportunities on poor soil types rather than climate variables alone. In contrast to previous observations within southeastern Australian rainforests, genetic differentiation in the AWT appears to be associated with small-fruited rather than large-fruited species, highlighting how external factors can influence the dispersal dimension. Overall, this study emphasizes the importance of considering functional and environmental factors when attempting generalizations on landscape-level patterns of genetic variation. Understanding how plant functional groups respond to environmental and climatic heterogeneity can help us predict responses to future change.

Composition of the seed bank in drawdown areas of Navigation Pool 8 of the Upper Mississippi River

AbstractIn an effort to enhance aquatic plant production and habitat diversity on the Upper Mississippi River (UMR), resource managers considered water level reduction as a management tool to increase the area of emergent and submersed aquatic vegetation by natural seed germination. To quantify the availability of seed, we assessed the potential seed bank of selected areas of Navigation Pool 8 of the UMR from substrate samples collected in spring 2000. We tested these samples for viable seed content under four hydrologic conditions: dry, moist, shallow flooded and submerged. Forty‐seven species were identified in the seed bank, including 27 obligate wetland, 10 facultative wetland and 7 upland species. Dominant taxa within the seed bank included Sagittaria spp., Lindernia dubia, Zosterella dubia, Cyperus spp., Eragrostis spp. and Leersia oryzoides. Of the four hydrologic treatments, moist substrates had the greatest species diversity and were the most productive, yielding an average density of 1420 seedlings m−2. Emergent and submersed aquatic species were widely distributed, each type occurring in more than 90% of the samples. Timing of seedling germination varied among species and has implications for scheduling drawdowns to promote establishment of desired species. Seed bank results were correlated with the vegetation response on substrates exposed during a reduction of water levels of Pool 8 during summer 2001. Experimentally determining the composition and viability of seed banks from drawdown areas provides information useful in predicting the types of vegetation that may develop on exposed substrates. Further, these findings provide resource managers a better understanding of the potential for achieving desired vegetation response through water level reductions. Published in 2008 by John Wiley &amp; Sons, Ltd.

Moving riparian management guidelines towards a natural disturbance model: An example using boreal riparian and shoreline forest bird communities

Forest harvesting strategies that approximate natural disturbances have been proposed as a means of maintaining natural species’ diversity and richness in the boreal forests of North America. Natural disturbances impact shoreline forests and upland areas at similar rates. However, shoreline forests are generally protected from harvest through the retention of treed buffer strips. We examined bird community responses to forest management guidelines intended to approximate shoreline forest fires by comparing bird community structure in early (1–4 years) post-burned and harvested boreal riparian habitats and the adjacent shoreline forest. We sampled riparian areas with adjacent: (1) burned merchantable shoreline forest ( n = 21), (2) burned non-merchantable shoreline forest ( n = 29), (3) 10 m treed buffer with 25% retention in the next 30 m ( n = 18), and (4) 30 m treed buffer ( n = 21). Only minor differences were detected in riparian species’ abundance and bird community composition between treatments with greater differences in these parameters occurring between post-fire and post-harvest upland bird communities. Indicators of all merchantable treatments were dominated by upland species with open-habitat species and habitat generalists being typical upland indicator species of burned merchantable habitats and forest specialists typical upland indicators of harvested treatments. Riparian species indicative of burned riparian habitats were Common Yellowthroat ( Geothlypis trichas), Le Conte’s Sparrow ( Ammodramus leconteii) and Eastern Kingbird ( Tyrannus tyrannus) and indicators of 30 m buffers were Alder Flycatcher ( Empidonax alnorum) and Wilson’s Warbler ( Wilsonia pusilla). Multivariate Redundancy Analysis (RDA) of the overall (riparian and upland birds) community showed greater divergence than RDA with only riparian species suggesting less effect of fire and forestry on riparian birds than on upland birds. Higher natural range of variability (NRV) of overall post-fire bird communities compared to post-harvest communities emphasizes that harvesting guidelines currently do not achieve this level of variability. However, lack of a large negative effect on common riparian species in the first 4 years post-disturbance allows for the exploration of alternative shoreline forest management that better incorporates bird community composition of post-fire riparian areas and shoreline forests.

Propagule banks: Potential contribution to restoration of an impounded and dewatered riparian ecosystem

The Agua Fria River in Arizona’s Sonoran Desert was impounded and diverted more than 70 years ago. Immediately below New Waddell dam there are semi-permanent pools, but water has been released into the channel only during rare wet years. To determine whether a propagule bank exists below the dam, and whether it could contribute to the revegetation of the Agua Fria riparian ecosystem should flow be restored to the dewatered reach, we collected 45 soil cores from four plant associations. We examined species in the samples in a growth chamber using the seedling emergence method. A total of 74 species (mostly herbaceous) and an abundance of individuals were present in propagule banks. The propagule banks were similar to those of a free-flowing reference river despite considerable differences in extant vegetation. Riparian species were present in propagule banks of all four associations and were the dominant type in three (Tamarix forests, Tamarix-Salix forests, and Baccharis-Bebbia shrublands). Propagule distribution varied with soil depth in three of the associations (Tamarix forests and the two xerophytic shrublands) with riparian species more prevalent in deep sediment and upland species more prevalent in surface soil and litter. Collectively these patterns suggest that a riparian legacy is present in Agua Fria propagule banks. However, riparian propagule density was low in the Hymenoclea-Bebbia shrublands, reflecting xerification of the riparian corridor. Given the physical barrier of the dam, continued diversion of stream flow, and rare flood releases, local inputs from xerophytes will dominate propagule bank dynamics in the future. Although propagule banks could contribute to redevelopment of the herbaceous component of the vegetation should stream flows be restored to this river reach, the riparian legacy likely will decline over time as riparian propagules reach the end of their lifespan while propagules of xerophytes continue to be replenished.

Variation in species composition and diversity of wetland communities under different disturbance intensity in the Sanjiang plain

In this study, ditch density was chosen as an indicator of disturbance intensity, and four sites with different ditch density were chosen to compare species composition and diversity among them. Four transects and sixty-seven quadrats were sampled along the ditch density gradient. The results showed that there existed a significant negative relationship between disturbance intensity and species parameters, while species diversity did not differ greatly among sites, but species composition varied considerably. With increasing disturbance intensity, the wetlands tended to be reduced in plant species diversity, and an increasing loss of indigenous wetland species was paralleled with an increasing invasion of upland species. The results also show that the rate of species turnover within communities differed among communities under different disturbance intensities. The communities with intermediate ditch density (0.6-1.2 km/km 2) had higher rates than the other communities.