Effects of flooding and artificial burning disturbances on plant species composition in a downstream riverside floodplain

Our objective was to detect environmental and disturbance factors that determine plant species composition in a downstream riverside floodplain of the Shinano River, where both natural flooding and artificial fire disturbances predominate. We classified the natural vegetation into five types by physiognomy, i.e., burnt field, intact (unburnt) field, early-successional forest, later-successional forest, and margin of channel. We deployed 14 transect belts containing 713 plots of 1 m × 1 m at these sites. In the plots, we determined plant occurrences and values of five environmental (soil moisture, soil texture, relative elevation above the river, horizontal distance from the river, and light conditions) and two disturbance factors (scouring of plants by flooding and fire). Plant species compositions and environmental and disturbance factors were different among the sites. Logistic regression analysis showed that burning stimulated the occurrences of herbaceous annuals and conversely constrained those of woody and fern species, suggesting that fire disturbance resets the succession. Scouring of plants by flooding also affected the occurrences of many species, and had a positive influence on that of herbaceous winter annuals in particular. Canonical correspondence analysis indicated that the distributional characteristics of the plant species in the riverside floodplain were influenced primarily by distance from the river, reflecting the magnitude of flood disturbance. We conclude that (1) magnitude of flood disturbance is the primary factor determining plant species composition, and (2) burning maintains early successional vegetation and simultaneously creates a unique plant species composition by stimulating the germination of buried viable seeds transported by flood.     

Our current understanding of the Upper Mississippi River System floodplain forest

The silver maple-American elm floodplain forest spans throughout the floodplains of the Upper Mississippi River System (UMRS). These forests of the UMRS today are less diverse than those of pre-European expansion (ca. early 1800s). Scientists and land managers are concerned about loss of species diversity including mast species such as pin oak (Quercus palustris Muenchh.), swamp white oak (Quercus bicolor Willd.), bur oak (Quercus macrocarpa Michx. Q), pecan (Carya illinoinensis (Wangenh.) K. Koch), and other hickories. The Great Midwest Flood of 1993 maintained species diversity in the lower, unimpounded region of the Upper Mississippi River, providing an opportunity for eastern cottonwood and black willow to regenerate in this portion of the Mississippi River. However, throughout the entire region, floodplain forests of the Upper Mississippi River have become less diverse, and have become dominated by the flood-tolerant and shade-tolerant silver maple (Acer saccharinum L.). The imminent loss of green ash (Fraxinus pennsylvanica Marsh.) to the Emerald Ash Borer (Agrilus planipennis Fairmaire) follows an already changing forest structure due to a disease-related shift of American elm (Ulmus americana L.) from the overstory to the midstory strata. Another invasive, reed canary grass (Phalaris arundinaceae L.), interferes with evolved mechanisms for establishment as it outcompetes trees of the early successional floodplain forest. Further research is needed to create and maintain diverse floodplain forest communities that have been lost under current conditions. Returning flood-prone agricultural lands within the floodplain to the floodplain forest will improve the health and connectivity of the river system, increase the diversity of habitats, and provide flood relief for communities of the Upper Mississippi River.     

Bird communities in habitats along a successional gradient: Divergent patterns of species richness,specialization and threat

The long history of human influence on northern temperate landscapes has created a mosaic of successional stages, from closed forest to open grassland. Various species thus adapted to different habitats and it is interesting to explore how these differences in species composition among particular successional stages translate into differences at the community level. For this purpose, we surveyed breeding birds in 233 patches of five different habitats covering a gradient from bare ground to forest in 29 abandoned military training sites scattered throughout the Czech Republic. Linear mixed effects modelling revealed that late-successional habitats (dense scrubland and forest) were the most species-rich, whereas early-successional stages hosted bird communities with the highest habitat specialization and threat level. These results suggest that the habitats of late-successional stages are important for the maintenance of high bird species richness, but that early-successional habitats are essential for highly specialized and threatened bird species. Given the highly adverse impacts of agricultural intensification and land abandonment on open habitats, it is necessary to promote factors creating initial successional stages suitable for specialized and threatened species.     

Floodplain conservation in the Mississippi River Valley: combining spatial analysis,landowner outreach,and market assessment to enhance land protection for the Atchafalaya River Basin,Louisiana, U.S.A.

Threats to riverine landscapes are often the result of system‐wide river management policy, located far from where the threats appear, or both. As a result, the rationale for land protection to achieve floodplain conservation and restoration has shifted to require that lands must also have multiple and systemic threat abatement benefits. The Mississippi River Flood of 2011 highlighted the need for increased floodplain complexes along the Mississippi River to provide both systemic threat abatement and conservation benefits. We used spatial analysis, landowner outreach, and market assessment to examine ways to enhance land protection in the Atchafalaya River Basin Floodway, the largest river basin swamp North America and the site of two employed floodway locations during the 2011 flood. We identified six Priority Conservation Areas (77,084 ha) in the floodway that are largely privately owned (mean 78.2 ± 6.4%), with forest dominated by Taxodium distichum (baldcypress) and hydrologic and water quality characteristics considered most suitable for baldcypress regeneration (31.2 ± 2.4% and 10.2 ± 3.0% of area, respectively). Landowners expressed high (80%) interest in land protection programs and found the range of property values derived from market analyzes (minimal protection—$346 USD/ha; additional protections—up to $2,223 USD/ha) to be reasonable. We seek to: (1) enhance current land protection in the Atchafalaya River Basin and (2) provide a model for using land protection to increase the number of floodplains for both systemic threat abatement and conservation benefits.     

Environmental causes and consequences of forest clearance and agricultural abandonment in central New York, USA

Aim Climate, topography and soils drive many patterns of plant distribution and abundance across landscapes, but current plant communities may also reflect a legacy of past disturbance such as agricultural land use. To assess the relative influences of environmental conditions and disturbance history on vegetation, it is important to understand how these forces interact. This study relates the geographical distribution of land uses to variation in topography and soils; evaluates the consequences of land‐use decisions for current forests; and examines the effects of agricultural land use on the chemical properties of forest soils. Location Tompkins County occupies 1250 km² in central New York's Finger Lakes region. Like much of eastern North America, this area underwent forest clearance for agriculture during the 1800s and widespread field abandonment and forest recovery during the 1900s. The current landscape consists of a patchwork of forests that were never cleared, forests that developed on old fields and active agricultural lands. Methods We investigated relationships among topography, soils and land‐use decisions by gathering information about land‐use history, slope, aspect, elevation, soil lime content, soil drainage and accessibility in a geographic information system (GIS). To assess the effects of agriculture on forest soil chemistry, we measured pH, organic matter content and extractable nutrient concentrations in field‐collected soil samples from 47 post‐agricultural and uncleared forests. Results Steeper slopes, less accessible lands and lower‐lime soils tended to remain forested, and farmers were more likely to abandon fields that were steeper, farther from roads, lower in lime and more poorly drained. Slope had by far the greatest impact on patterns of clearance and abandonment, and accessibility had a surprisingly strong influence on the distribution of land uses. The effects of other factors varied more, depending for example on location within the county. Current forest types differed accordingly in topography and soil attributes, particularly slope, but they also showed much overlap. Post‐agricultural and uncleared forest soils had similar chemical properties. Forests on lands abandoned from agriculture 80–100 years before had slightly higher pH and nutrient concentrations than adjacent, uncleared forests, but these changes were small compared to environmental variation across the county. Main conclusions Despite differential use of lands according to their topography and soils, the substantial influence of accessibility and the relatively small scale of land‐use decisions allowed for broad similarity among forest types. Thus, the topography and soil differences created by land‐use decisions probably contribute little to landscape‐level patterns of diversity. Subtle changes in forest soil chemistry left from past agriculture may nevertheless affect plant distribution and abundance at finer scales.     

Distribution and abundance of trees in floodplain forests of the Wisconsin River: Environmental influences at different scales

Questions: 1. How do physiography, flooding regime, landscape pattern, land‐cover history, and local soil conditions influence the presence, community structure and abundance of overstorey trees? 2. Can broad‐scale factors explain variation in the floodplain forest community, or are locally measured soil conditions necessary? Location: Floodplain of the lower 370 km of the Wisconsin River, Wisconsin, USA. Methods: Floodplain forest was sampled in 10 m × 20 m plots [n= 405) during summers of 1999 and 2000 in six 12‐ to 15‐km reaches. Results: Species observed most frequently were Fraxinus pennsylvanica, Acer saccharinum and Ulmus americana. Physiography (e.g. geographic province) and indicators of flooding regime (e.g. relative elevation and distance from main channel) were consistently important in predicting occurrence, community composition, and abundance of trees. Correspondence analysis revealed that flood‐tolerant and intolerant species segregated along the primary axis, and late‐successional species segregated from flood‐tolerant species along the secondary axis. Current landscape configuration only influenced species presence or abundance in forests that developed during recent decades. Land‐cover history was important for tree species presence and for the abundance of late‐successional species. Comparison of statistical models developed with and without soils data suggested that broad‐scale factors such as geographic province generally performed well. Conclusions: Physiography and indicators of flood regime are particularly useful for explaining floodplain forest structure and composition in floodplains with a relatively high proportion of natural cover types.     

Predictability of flood pulse driven assembly rules for restoration of a floodplain plant community

Community assembly rules were formulated to evaluate the restoration of wet prairie along the periphery of the floodplain of the Kissimmee River in central Florida. Restoration of this plant community is expected to be driven by the reestablishment of flood pulse hydrology following the ongoing dechannelization of the river. Assembly rules were assessed with plant species composition and cover data from 15 permanent plots on the restored floodplain and 6 control plots on the channelized floodplain. These sites were sampled biannually from 1998 to 2010. Mean annual hydroperiods and depths confirmed that the frequency, duration and amplitude of post-restoration flood pulses at study sites were similar to historic reference locations. Elimination of pasture grasses (primarily Paspalum notatum Flüggé) following restoration of the flood pulse validated the hypothesized deletion rule for initial transformation of the wet prairie zone. Predicted increased dominance of obligate and facultative wetland species, a “community addition rule”, also was confirmed. An index of weighted averages of wetland indicator taxa showed significant short-term responses to antecedent hydroperiods and depths, and a restoration trajectory for wetland plant species. As predicted, recruitment of wet prairie indicator species from the extant seed bank correlated with reestablishment of the flood pulse, but was greatest when inundation extended from the wet season into the dry season. Restoration of a wetland plant community did not result in the predicted increase in species richness and diversity. Colonization and expansion of the exotic grass, Hemarthria altissima (Poir.) Stapf & C.E. Hubb., disrupted community reassembly processes. By summer 2007, mean cover of this species and several other exotic grasses increased to 24%, and necessitated herbicide treatments. Assembly rules provided useful predictions for the initial restoration of wet prairie vegetation, but were eventually confounded by the spread of an exotic species that was new to the regional flora.     

Recovery of soil productivity with forest succession on abandoned agricultural land

Much of the primary forest in the eastern United States that was converted to farmland between 1600 and 1900 has reverted back to second growth forest as a result of agriculture abandonment. This reversion back to forest gives soil productivity a chance to recover, though the rates of recovery are not well understood. Understanding the legacy effects of past disturbances like agriculture can provide important insights to support ecological restoration efforts on disturbed soils. Our goal with this study was to further understand the effects of forest development on soil productivity after agriculture abandonment. We used a chronosequence approach to examine soil properties over a 60‐year temporal scale of forest development on abandoned agricultural lands in Saratoga and Rensselaer Counties in New York, U.S.A. We measured soil properties within this chronosequence to test the hypothesis that there would be measurable recoveries of soil physical properties and fertility over time. We observed rapid recovery of physical properties (lower bulk density and higher macroporosity) of surface soils within 5–10 years after agricultural abandonment. However, we found a legacy effect of agricultural compaction still evident in subsoils, with soil strength measurements indicating that past agricultural practices still limited root growth 55–60 years after abandonment. Soil percent organic matter and mineralizable nitrogen (N) both increased with forest development, but biomass accumulation may be slowed by limited root growth in the subsoil due to high strength. We recommend assessing subsoil physical properties when developing ecological restoration plans for agricultural lands.     

A study of seed dispersal by flood flow in an artificially restored floodplain

Riverine floodplains play many important roles in river ecosystems. However, many floodplains have suffered degradation or loss of ecological function due to excessive river improvements or through changes in agricultural systems. As a result, many floodplain restoration projects are being conducted worldwide. One of the many methods being implemented to restore floodplain vegetation is flood water seed dispersal. In this technique, precisely estimating the effect of seed dispersal by flood water is important in order to achieve successful floodplain revegetation. Here, we focus our attention on sediment transport by flood water into the Azamenose Swamp, a restored floodplain. We attempt to estimate the function of seed deposition in the restored floodplain and explain how the seeds are deposited in the floodplain by flood water. The result suggests that the restored floodplain functions as a more appropriate deposition site for seeds than the riverbanks of the main river. It was also found that the distance from the inflow site and the weight of the sediment were related to seed deposition.     

Understory vegetation as an indicator for floodplain forest restoration in the Mississippi River Alluvial Valley,U.S.A.

In the Mississippi River Alluvial Valley (MAV), complete alteration of river‐floodplain hydrology allowed for widespread conversion of forested bottomlands to intensive agriculture, resulting in nearly 80% forest loss. Governmental programs have attempted to restore forest habitat and functions within this altered landscape by the methods of tree planting (afforestation) and local hydrologic enhancement on reclaimed croplands. Early assessments identified factors that influenced whether planting plus tree colonization could establish an overstory community similar to natural bottomland forests. The extent to which afforested sites develop typical understory vegetation has not been evaluated, yet understory composition may be indicative of restored site conditions. As part of a broad study quantifying the ecosystem services gained from restoration efforts, understory vegetation was compared between 37 afforested sites and 26 mature forest sites. Differences in vegetation attributes for species growth forms, wetland indicator classes, and native status were tested with univariate analyses; floristic composition data were analyzed by multivariate techniques. Understory vegetation of restoration sites was generally hydrophytic, but species composition differed from that of mature bottomland forest because of young successional age and differing responses of plant growth forms. Attribute and floristic variation among restoration sites was related to variation in canopy development and local wetness conditions, which in turn reflected both intrinsic site features and outcomes of restoration practices. Thus, understory vegetation is a useful indicator of functional progress in floodplain forest restoration.     

Strategies to restore floodplain vegetation after abandonment of human activities

Restoring the flooding‐related disturbance regime by removing and setting back flood defenses (channel widening) is the most efficient strategy for recovering riparian plant communities in floodplains formerly impacted by human activities such as agriculture, mining, and forestry. Removing flood defenses is generally not socially accepted, and alternative recovery strategies must be explored. We assessed vegetation establishment on 33 sites in the floodplains of the Middle Ebro River and three of its tributaries (NE Spain) where restoration approaches applied in the last 20 years include channel widening, floodplain excavation, and abandonment of agriculture, gravel extraction, and hybrid poplar plantations, with and without plantation of native species. Using analysis of similarity and ordinations, we found that channel widening led to plant communities closely resembling those found on natural gravel bars, including new recruits of keystone tree species. Excavation of the floodplain as the restoration approach resulted in pioneer, non‐strictly riparian communities. Abandonment of agricultural land or clearing of poplar plantations resulted in alternative stable states predominating, regardless of time elapsed since restoration and whether poles of native species were planted. However, forest‐like communities relatively similar to mature, natural riparian references were attainable when hybrid poplars were allowed to resprout after clear‐cutting, or after the human activities were abandoned and trees were not cut. Combining channel widening and assisted revegetation where flood defenses cannot be altered may partially reproduce a mosaic of habitats typical of natural floodplains.     

Relative contributions of sexual and asexual regeneration strategies in Populus nigra and Salix alba during the first years of establishment on a braided gravel bed river

Populus nigra L. var betulifolia and Salix alba L. var alba are early successional riparian tree species threatened throughout Continental Europe by significant changes to the natural physical processes governing their natural habitat – geomorphologically active floodplains. River management activities have dramatically altered natural patterns of river flow and rates of sediment delivery along rivers, with possible consequences for the balance between sexual and asexual regeneration strategies in these species. Conservation strategies will benefit from a greater understanding of the ways in which dynamic physical processes on the floodplain influence sexual and asexual recruitment. This paper describes a field survey investigating the relative abundance and spatial distributions of P. nigra and S. alba sexual and asexual recruits during the first years of establishment along a braided gravel bed river. Sexual and asexual recruits were identified by excavation along transects in a wet and a dry field season and distributional differences were described in terms of elevation on the floodplain, local sediment type and exposure to floodwaters. Regeneration was overwhelmingly from seed in the first 2–3 years following recruitment, but poor survival rates among sexual recruits saw a shift in the relative abundance of regeneration strategies over time. In relating hydrological data to recruitment, unseasonal flood disturbances had a negative effect on recruitment from seed and a positive effect on vegetative regeneration. Seedlings were associated with fine sediment deposits and were restricted primarily to low elevations on the flood plain, while asexual recruits had a wider spatial distribution. Certain microsite types were unique to either regeneration strategy.     

Spatial patterns of mycorrhizal infectiveness of soils long a successional chronosequence

 This study quantified intersite variation and spatial pattern in arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) infectivity of soils among six sites constituting a successional chronosequence in southwestern Ohio, USA. The study sites included an active agricultural field (chronic disturbance), a site which had been stripped of its surface soil (pseudo-stripmine, acute disturbance), 5- and 10-year-old fields, a 25- to 30-year-old prairie restoration, and an undisturbed, mature forest. AM infectivity was lower in the agricultural field, successional fields, and prairie than in the mature forest, but there was no clear correlation between time since disturbance and the overall level of AM infectivity. Spatial structure in AM infectivity decreased with time since disturbance. In the pseudo-stripmine site and active soybean field, semivariance analysis attributed 44–50% of the total variance in AM infectivity among samples to spatial structure, whereas spatial dependancy accounted for only 18% of total variance in the mature forest. Kriging of AM infectiveness demonstrated small, isolated areas in the disturbed plots that were devoid of AM infectiveness, whereas the kriged AM maps of the other four sites showed AM infectiveness to become progressively more homogeneous. ECM infectiveness was lacking from 35–50% of the samples from the disturbed sites, and both overall ECM infectiveness and ECM diversity increased with time since disturbance. Approximately 44% of the variance in ECM infectiveness was related to spatial structure in the two disturbed sites, and large areas entirely devoid of ECM infectivity were present on the kriged ECM maps for these sites. There was less spatial structure in ECM in the old fields and prairie and very little in the mature forest. The results of this study emphasize the need to explicitly evaluate spatial heterogeneity in mycorrhizal infectivity in studies of the role of mycorrhizae in succession. Accepted: 4 August 1995     

Prairie Dogs: An Ecological Review and Current Biopolitics

ABSTRACT In recent years, people have interpreted scientific information about the black-tailed prairie dog (Cynomys ludovicianus) in various, and sometimes conflicting, ways. Political complexity around the relationship among black-tailed prairie dogs, agricultural interests, and wildlife has increased in recent years, particularly when prairie dogs occur on publicly owned lands leased to private entities for livestock grazing. Some have proposed that estimates of prairie dog (Cynomys spp.) numbers from 1900 are inflated, that prairie dog grazing is not unique (other grazers have similar affects on vegetation), and that prairie dogs significantly reduce carrying capacity for livestock and wildlife. We address all these issues but concentrate on the degree of competition between prairie dogs and ungulates because this motivates most prairie dog control actions. We conclude that the available information does not justify holding distribution and numbers of prairie dogs at a level that is too low to perform their keystone ecological function. We further conclude that it is especially important that prairie dogs be sufficiently abundant on public lands to perform this function.     

Temporary connectivity: the relative benefits of large river floodplain inundation in the lower Mississippi River

Studies have demonstrated the importance of the synergistic relationship between large rivers and adjacent floodplain connectivity. The majority of large rivers and their associated floodplain have been isolated through a series of expansive levee systems. Thus, evaluations of the relative importance of floodplain connectivity are limited due to the aforementioned anthropogenic perturbations. However, persistent elevated river levels during spring 2011 at the confluence of the Mississippi River and Ohio River prompted the U.S. Army Corps of Engineers to create large gaps in the levee system producing an expansive floodplain (i.e. the New Madrid Floodway). Specifically, the New Madrid Floodway (approximately 475 km²) in southeast Missouri was created to divert part of the Mississippi River flow during catastrophic floods and thus alleviate flood risk on nearby population centers. Given the historic flooding of 2011, the floodway was opened and provided an unprecedented opportunity to evaluate the influence of floodplain inundation on fish species diversity, relative abundance, and growth. We sampled the floodplain and the adjacent river at three stratified random locations with replication biweekly from the commencement of inundation (late May) through early October. Overall, we found that species diversity, relative abundance, and growth were higher in the floodplain than the main river. Our data support previous examinations, including those outside North America, that suggest floodplain inundation may be important for riverine fishes. Given these apparent advantages of floodplain inundation, restoration efforts should balance benefits of floodplain inundation while safeguarding priority needs of humans.     

The Role of Abandoned Channels as Refugia for Sustaining Pioneer Riparian Forest Ecosystems

In disturbance-prone ecosystems, organisms often persist in spatial refugia during stressful periods. A clear example is the colonization of abandoned river channels by pioneer riparian trees. Here, we examine the prominence of this establishment pathway for a foundation tree species (Fremont cottonwood, Populus fremontii) within the riparian corridor of a large river, the Sacramento River in central California. We quantified the total proportion of forest that initiated as a result of channel abandonment for a 160-km reach, analyzed concurrent patterns of tree establishment with floodplain accretion and sedimentation history, and developed a conceptual model of biogeomorphic evolution of abandoned channels. Historical air photo analysis indicated that stands associated with abandoned channels comprised more than 50% of the total extant cottonwood forest area. Tree-ring evidence showed that cottonwood stands commonly developed immediately following abandonment, and the recruitment window ranged from 4 to 40 years, but was less than 10 years at most sites. Rates of floodplain rise and fine sediment accumulation were high in young sites and decreased logarithmically over time. Together, these results suggest that abandoned channels are an important refuge for cottonwood recruitment, that the greatest opportunity for colonization occurs within a short period after the cutoff event, and that sedimentation processes influence the duration of the colonization window. On rivers where tree recruitment along the active channel is severely limited by hydrologic regulation and/or land management, abandoned channel refugia may play an even more important role in sustaining an ecologically functional riparian corridor. Preserving bank erosion, active meander corridors and forest regeneration zones created by cutoff events are therefore key conservation measures on shifting rivers.     

Floodplain ants show a stronger response to an extensive flood than to variations in fallen‐timber load

Understanding how species respond to differences in resource availability is critical to managing biodiversity under the increasing pressures associated with climate change and growing human populations. Over the last century, the floodplain forests of Australia's largest river system, the Murray‐Darling Basin, have been much affected by intensive harvesting of timber and firewood, and increasingly stressed by river regulation and, recently, an extended drought. Fallen timber – logs and shed branches – is known to play a key role in the ecology of several important species on these floodplains. Here, we monitored the response of the ant assemblages of a floodplain forest along the Murray River to a large‐scale (34 ha) experimental manipulation of fallen‐timber load (0 to 80 t ha^?1) over 4 years. The forest was subjected to an incidental, extensive flood that enabled us to examine how two important stressors (timber removal and river regulation) affect ant assemblages. Ants showed little response to the proximity of fallen timber within plots, prior to the flood, or to different loads among plots, unlike other floodplain biota. After the flood, both ant abundance and species richness increased and species composition changed. However, this increase in species richness after flooding was less pronounced in plots with higher amounts of fallen timber. Managing river red gum forest using a mosaic of flood regimes, more representative of historical conditions, is likely to be the most effective way to maintain and enhance the diversity of ants and other biota on these important floodplains.     

Are forest birds categorised as “edge species” strictly associated with edges?

In recent years, studies of bird-habitat relationships undertaken in the context of habitat fragmentation have led to the widespread use of species categorisation according to their response to edge alongside mature forest patches (edge species, interior species, interior-edge generalist species). In other research contexts, especially in less fragmented landscapes dominated by a forested land base in various age classes, bird-habitat relationships are often described in relation to their use of various successional stages (early-successional species, mature forest species, generalist species). A simple comparison of these two commonly-used classifications schemes in a close geographical range for 60 species in eastern North America as well as for 36 species in north-western Europe clearly reveals that in these two particular biomes the two classifications are not independent. We believe that this association is not only a semantic issue and has important ecological consequences. For example, almost all edge species are associated with early-successional habitats when a wide range of forest age-classes are found in a given area. Accordingly, we suggest that most species considered to prefer edge habitats in agricultural landscapes are in fact only early-successional species that could not find shrubland conditions apart from the exposed edges of mature forest fragments. To be considered a true edge species, a given species should require the simultaneous availability of more than one habitat type and consequently should be classified as a habitat generalist in its use of successional stages. However, 28 out of 30 recognised edge species were considered habitat specialists in terms of successional status. Based on these results, we conclude that "real edge species" are probably quite rare and that we should make a difference between true edge species and species which in some landscapes, happen to find their habitat requirements on edges.     

Factors influencing the seed source and sink functions of a floodplain nature reserve in the Netherlands

Question: How do species traits and abiotic factors influence the extent of hydrochorous dispersal into and out of a small floodplain area along a free‐flowing river in The Netherlands? Location: The Kappersbult nature reserve (53°07′28″N, 6°37′14″E), which is a floodplain along the Dutch River Drentsche Aa. Methods: Seeds transported by the river were collected in fine mesh nets for 24 consecutive hours once or twice a week for 1 year, upstream and downstream of the studied floodplain. Data on the captured seeds were related to species traits and abiotic factors and species composition in the floodplain. Results: The floodplain functioned both as a seed source and sink. High levels of river water seemed to promote seed transport to or from the floodplain. Seeds of riverbank species occurred significantly more often in the river water than expected. Net source species had significantly higher seed production, taller stature and higher seed buoyancy, but lower site elevation than net sink species. Seed weight was significantly higher for sink species than for other species. Conclusion: Our study found that inundation, and therefore more natural river water management, is a prerequisite for seed transport to and from a floodplain. The restoration of target floodplain vegetation may be successful for common species that produce many seeds and grow in proximity to the river. Consequently, it is expected that the probability of restoring vegetation types that occur further from the river, such as wet grasslands, by hydrochorous dispersal is low.     

Hydrologic and geomorphic considerations in restoration of river-floodplain connectivity in a highly altered river system,Lower Missouri River,USA

Planning for restoration of river-floodplain systems requires understanding how often and how much of a floodplain may be inundated, and how likely the floodplain is to retain the water once flooded. These factors depend fundamentally on hydrology and geomorphology of the channel and floodplain. We discuss application of an index of river-floodplain connectivity, the Land Capability Potential Index (LCPI), to regional-scale restoration planning along 600 km of the Lower Missouri River. The LCPI integrates modeled water-surface elevations, floodplain topography, and soils to index relative wetness of floodplain patches. Geomorphic adjustment of the Lower Missouri River to impoundment and channel engineering has altered the natural relations among hydrology, geomorphology, and floodplain soils, and has resulted in a regional upstream to downstream gradient in connectivity potential. As a result, flow-regime management is limited in its capacity to restore floodplain ecosystems. The LCPI provides a tool for identifying and mapping floodplain restoration potential, accounting for the geomorphic adjustment. Using simple criteria, we illustrate the utility of LCPI-like approaches in regional planning for restoration of plains cottonwood (Populus deltoides) communities, hydrologically connected floodplain wetlands, and seasonal floodplain wetlands.