Riparian Hardwood Research Articles

Invasive neophytes alter ecological functions and services of riparian hardwood forests

Riparian hardwood forests, now rare in Europe, occur in small patches within agricultural landscapes and are important biodiversity hotspots protected by the EU Habitats Directive and monitored. They play a vital ecological role and provide essential ecosystem services (ES). Recent studies indicate their unfavourable conservation status with a negative trend reported by EU Member States. One of the most visible symptoms of the degradation of riparian hardwood forest is the invasion of alien plant species which can radically change ecosystem functions. In this work, we use plant functional trait analysis to develop proxies and quantify an impact of invasive alien species, specifically invasive neophytes, on specific functions of riparian hardwood forests and their potential to provide five relevant regulating services. Data from 249 phytosociological relevés across 83 Natura 2000 habitat monitoring sites in Poland were analyzed.Our findings indicate that invasive neophytes negatively affect the potential for maintaining nursery populations and habitats, as well as regulation of the chemical condition of freshwaters by these forests. On the other hand, they do not significantly influence the local climate conditions and the forests’ potential to produce antimicrobial compounds. We recommend integrating an ES assessment based on plant functional traits into habitat monitoring. This approach is cost-effective, leveraging existing data, and its results could be used in some cases as a premise for initiating additional environmental monitoring based on direct field measurements.

Habitat preferences and phytocoenotic range of Reynoutria japonica Houtt. in Ukraine

Based on vegetation plots extracted from phytosociological databases and literature sources, the current distribution of Reynoutria japonica in Ukraine was assessed in terms of habitat preferences and phytocoenotic affiliation. It has been found that R. japonica in Ukraine is spread across four habitat types: anthropogenic areas, floodplain forests, shrublands, and gravel bars. The most frequent occurrences of the studied species were found in anthropogenic habitats covered by mesophilous nitrophilous tall herbs. Within the floodplain habitats, R. japonica was most frequently found in temperate riparian willow-poplar forests and temperate riparian hardwood forests. R. japonica is much less frequently related to shrub habitats and gravel bars. It occurs with different covers, reaching its maximum values on anthropogenic sites. The analysis of the phytocoenotic range of species showed that it is a component of the vegetation belonging to the classes Epilobietea angustifolii, Salicetea purpurea, Alno glutinosae-Populetea albae, and Thlaspietea rotundifolii. The analysis of habitat types and plant communities with the participation of R. japonica in Ukraine showed that the species occurs in ecological environments closely related to those that are characteristic of the species in its native range – mesophylous soils, rich in nutrients, which is a favorable factor in the process of species accelerated adaptation to new territories.

Habitat and climatic associations of climate-sensitive species along a southern range boundary.

Climate change and habitat loss are recognized as important drivers of shifts in wildlife species' geographic distributions. While often considered independently, there is considerable overlap between these drivers, and understanding how they contribute to range shifts can predict future species assemblages and inform effective management. Our objective was to evaluate the impacts of habitat, climatic, and anthropogenic effects on the distributions of climate-sensitive vertebrates along a southern range boundary in Northern Michigan, USA. We combined multiple sources of occurrence data, including harvest and citizen-science data, then used hierarchical Bayesian spatial models to determine habitat and climatic associations for four climate-sensitive vertebrate species (American marten [Martes americana], snowshoe hare [Lepus americanus], ruffed grouse [Bonasa umbellus] and moose [Alces alces]). We used total basal area of at-risk forest types to represent habitat, and temperature and winter habitat indices to represent climate. Marten associated with upland spruce-fir and lowland riparian forest types, hares with lowland conifer and aspen-birch, grouse with lowland riparian hardwoods, and moose with upland spruce-fir. Species differed in climatic drivers with hares positively associated with cooler annual temperatures, moose with cooler summer temperatures and grouse with colder winter temperatures. Contrary to expectations, temperature variables outperformed winter habitat indices. Model performance varied greatly among species, as did predicted distributions along the southern edge of the Northwoods region. As multiple species were associated with lowland riparian and upland spruce-fir habitats, these results provide potential for efficient prioritization of habitat management. Both direct and indirect effects from climate change are likely to impact the distribution of climate-sensitive species in the future and the use of multiple data types and sources in the modelling of species distributions can result in more accurate predictions resulting in improved management at policy-relevant scales.

Influence of landscape attributes on Virginia opossum density

AbstractThe Virginia opossum (Didelphis virginiana), North America's only marsupial, has a range extending from southern Ontario, Canada, to the Yucatan Peninsula, Mexico, and from the Atlantic seaboard to the Pacific. Despite the Virginia opossum's taxonomic uniqueness in relation to other mammals in North America and rapidly expanding distribution, its ecology remains relatively understudied. Our poor understanding of the ecology of this important mesopredator is especially pronounced in the rural southeastern United States. Our goal was to estimate effects of habitat on opossum density within an extensive multi‐year spatial capture‐recapture study. Additionally, we compared the results of this spatial capture‐recapture analysis with a simple relative abundance index. Opossum densities in the relatively underdeveloped regions of the southeastern United States were lower compared to the more human‐dominated landscapes of the Northeast and Midwest. In the southeastern United States, Virginia opossums occurred at a higher density in bottomland swamp and riparian hardwood forest compared to upland pine (Pinus spp.) plantations and isolated wetlands. These results reinforce the notion that the Virginia opossum is commonly associated with land cover types adjacent to permanent water (bottomland swamps, riparian hardwood). The relatively low density of opossums at isolated wetland sites suggests that the large spatial scale of selection demonstrated by opossums gives the species access to preferable cover types within the same landscape.

Diversity and Seasonal Occurrence of Native and Nonnative Ants (Hymenoptera: Formicidae) in Long-Term Experimental Chinese Privet (Lamiales: Oleaceae) Plots in Georgia, USA

Diversity and Seasonal Occurrence of Native and Nonnative Ants (Hymenoptera: Formicidae) in Long-Term Experimental Chinese Privet (Lamiales: Oleaceae) Plots in Georgia, USA

Pollination Potential of Riparian Hardwood Forests—A Multifaceted Field-Based Assessment in the Vistula Valley, Poland

Riparian forests with oaks, ashes and elms, now highly fragmented and rare in Europe, are considered hotspots for ecosystem services. However, their capacity to provide pollination seems to be quite low, although reports from in-situ research supporting this view are scarce. Our goal was therefore to thoroughly assess their pollination potential based on multifaceted field measurements. For this, we selected six test sites with well-developed riparian hardwood forests, located in the agricultural landscape along the middle Vistula River in Poland. We used seven indicators relating to habitat suitability (nesting sites and floral resources) and pollinator abundance (bumblebees and other Apoidea) and propose a threshold value (AdjMax) based on value distribution and Hampel’s test to indicate the level of pollination potential for this type of riparian forest. The obtained AdjMax for bumblebee density was 500 ind. ha−1, for Apoidea abundance—0.42 ind. day−1, while for nectar resources—200 kg ha−1. We demonstrate that the investigated small patches of the riparian hardwood forest have a higher pollination potential than reported earlier for riparian and other broadleaved temperate forests, but the indicators were inconsistent. As forest islands in the agricultural landscape, riparian hardwood forests play an important role in maintaining the diversity and abundance of wild pollinators, especially in early spring when there is still no food base available elsewhere.

First report of Armillaria cepistipes causing root disease on Populus trichocarpa (black cottonwood) in Oregon, USA.

Populus trichocarpa Torr. and Gray (black cottonwood) is an economically and ecologically important tree species native to western North America. It serves as a model tree species in biology and genetics due to its relatively small genome size, rapid growth, and early reproductive maturity (Jansson and Douglas 2007). Black cottonwood is susceptible to root rot caused by at least one species of Armillaria (Raabe 1962), a globally distributed genus that exhibits diverse ecological behaviors (Klopfenstein et al. 2017) and infects numerous woody plant species (Raabe 1962). However, several Armillaria spp. have been isolated from Populus spp. in North America (Mallet 1990), and the most recent report of Armillaria on P. trichocarpa used the now ambiguated name A. mellea (Vahl.) Quel. (see Raabe 1962). In April 2016, mycelial fans and rhizomorphs of an unknown Armillaria species (isolate WV-ARR-3) were collected from P. trichocarpa in a riparian hardwood stand ca. 5.5 km east of Springfield, Oregon, USA (44°3'21.133"N, 122°49'39.935"W). The host was dominant in the canopy, large in diameter (ca. 90-cm dbh) relative to neighboring trees, and exhibited minimal crown dieback (ca. < 5%). A mycelial fan was observed destroying living cambium beneath the inner bark, indicating pathogenicity. The isolate was cultured on malt extract medium (3% malt extract, 3% dextrose, 1% peptone, and 1.5 % agar) and identified as A.cepistipes on the basis of somatic pairing tests and translation elongation factor 1α (tef1) sequences (GenBank Accession No. MK172784). DNA extraction, PCR, and tef1 sequencing followed protocols of Elías-Román et al. (2018). From nine replications of somatic incompatibility tests (18 tester isolates representing six North American Armillaria spp.), the isolate showed high intraspecific compatibility (colorless antagonism) with three A. cepistipes tester isolates (78%), but low compatibility with the other Armillaria spp. (0 - 33%) that occur in the region. Isolate WV-ARR-3 yielded tef1 sequences with a 99% identity to A. cepistipes (GenBank Accession Nos. JF313115 and JF313121). A second isolate (WV-ARR-1; GenBank Accession No. MK172783) with a nearly identical sequence was collected from a maturing P. trichocarpa in a riparian stand ca. 8 km northeast of Monroe, Oregon (44°21'47.57"N, 123°13'14.415"W) along the Willamette River, downstream from the McKenzie river tributary where WV-ARR-3 was collected. Armillaria cepistipes has been reported on Alnus rubra (red alder) in Washington, USA (Banik et al. 1996) and on broad-leaved trees in British Columbia, Canada (Allen et al. 1996). It is generally considered to be a weak pathogen on broad-leaved trees in the Pacific Northwest, but it is also associated with pathogenicity on both coniferous and deciduous trees in Europe (e.g., Lygis et al. 2005). However, a recent phylogenetic study suggested that North American A. cepistipes is phylogenetically distinct from Eurasian A. cepistipes (Klopfenstein et al. 2017), butadditional studies are needed to determine the formal taxonomic status of North American A. cepistipes. To our knowledge, A. cepistipes has not been previously confirmed on P. trichocarpa in the U.S.A. or formally reported as a pathogen of any Populus species in North America. Continued studies are needed to determine the distribution, host range, and ecological role of A. cepistipes in riparian forests of the Pacific Northwest, while monitoring its populations under changing climates.

Walnut twig beetle landing rates differ between host and nonhost hardwood trees under the influence of aggregation pheromone in a northern California riparian forest

Abstract Host selection behaviour of the walnut twig beetle (WTB) among hardwood trees was investigated in a riparian forest in northern California by monitoring the landing rate of the beetle with sticky traps on branches baited with 3‐methyl‐2‐buten‐1‐ol, the male‐produced aggregation pheromone. The assay was conducted over 7 days (22 May to 29 May 2017) and compared landing rates on branches of six nonhost species paired with northern California black walnut, Juglans hindsii (the host). A total of 2242/1192 WTB were collected on branches of host/nonhost pairs, and more WTB landed on J. hindsii than on nonhosts in 42 of 58 instances. Female landing rate generally exceeded male landing rate, which underscores the influence of the male‐produced synthetic pheromone in this system. Landing rates of WTB males, females, and the combined sexes on boxelder, Acer negundo, and valley oak, Quercus lobata, did not differ significantly from the landing rates on J. hindsii, suggesting that these two nonhost riparian hardwoods do not repel WTB (in the context of the aggregation pheromone). Significantly fewer WTB landed on Oregon ash, Fraxinus latifolia, river red gum, Eucalyptus camaldulensis, Fremont cottonwood, Populus fremontii, and red willow, Salix laevigata, than on J. hindsii, which suggests that these four nonhosts may repel one or both sexes of WTB in the context of the aggregation pheromone. Future analysis of the volatiles from these four hardwood species may lead to the discovery of semiochemical repellents for WTB.

Assessment of regulating ES potential of lowland riparian hardwood forests in Poland

Lowland riparian hardwood forests are valuable habitats protected by EU Habitat Directive (EU code: 91F0). Today, in most areas across Europe they are extremely rare due to deforestation, drainage and river engineering. The remaining small forest patches are important parts of riparian ecological corridors and biodiversity hotspots, and provide valuable ecosystem services (ES) to humans. However, unlike other forest types, due to their rarity and often low accessibility their ES potential has not been duly recognized and assessed to date. In this work we propose a set of biophysical indicators to assess the regulating potential of riparian hardwood forests. Indicator values were obtained through extensive field work and direct measurements carried out on selected test sites located along the middle Vistula River. The specific objectives of this work were: (i) to estimate the potential of riparian hardwood forests to provide 11 regulating services and to identify interactions among them; (ii) to examine the effects of forest and environmental attributes on individual ES; (iii) to determine ES drivers. Our results clearly show that riparian hardwood forests may be regarded as multiservice hotspots. Their regulating potential has proved to be substantial and in case of many services higher than the potential of other forest ecosystems. However, disruption of the natural water regime due to the absence of flooding and artificial drainage reduces their potential mainly for water-related regulating services (e.g. water treatment). On the other hand, more mesic habitats are beneficial for melliferous plant species and thus for wild pollinators. Most of the strong and significant interactions among the studied regulating services are synergistic. The high ES potential quantified by the biophysical ecosystem-condition-related indicators can be used effectively to promote the maintenance or restoration of this type of forests. The outcomes of our research suggest that protective actions should focus on ensuring adequate soil-moisture conditions which determine the specificity of these ecosystems.

Neofityzacja łęgów jesionowo-wiązowych w dolinach polskich rzek = Neophyte-induced degradation of Poland’s riparian hardwood forests

Riparian hardwood forests have become very rare in most areas across Europe, as their fertile habitats have mostly been transformed into grasslands and arable land. Furthermore, where small patches remain, these are seen to be subject to major changes in soil cover and plant composition, thanks to habitat change induced by drainage, river engineering, the construction of river embankments and forestry. A further, highly visible symptom of the degradation of riparian hardwood forest is invasion by alien species (neophytes). This article therefore draws on work to analyze Poland’s vegetation of riparian hardwood forest, by reference to some 249 phytosociological relevés from 83 sites located along river valleys (Fig. 1). The work came within Natura 2000 habitat monitoring, and specifically a research project entitled Riparian hardwood forest services in the middle Vistula river valley. The main objectives here were to point to any relationships that might pertain between the share of invasive alien species and the structure and composition of riparian hardwood forest vegetation, as well as to determine the former’s habitat requirements. The studied communities were divided into two groups: ZI – with the presence of invasive alien species, and ZN – natural communities lacking such species (as listed by Tokarska-Guzik et al., 2012). Relationships between the share of invasive species and the structure and composition of native vegetation were tested by comparing species richness (number of species: S – general, SA – trees, SB – shrubs, SC – herbs, SD – bryophytes), species diversity (H – the Shannon diversity index (Shannon and Weaver, 1949), J – the Pielou evenness index (Pielou, 1975)), habitat preferences of species by reference to Ellenberg ecological indicators (Ellenberg et al., 1992) and socio-ecological affinity (after Schmidt et al., 2011). Spearman rank correlation coefficients were used to assess relationships between the numbers of invasive alien species and the cover-shares they accounted for on the one hand, and the values of all studied parameters on the other. Mean values were compared across the ZI and ZN groups using the Mann-Whitney U-test. Statistical analyses were performed using PAST 2.17 (Hammer et al., 2001). Invasive alien species were recorded on ca. 70% of the plots studied. Small balsam was species among the 15 observed most frequently and achieving greatest abundance (Table 1, Fig. 2). Lower general richness of species in the communities where invasive alien species are present results mainly from decline in numbers of hygrophilous and shade-tolerant forest species, as well as shrubs and bryophytes (Table 2). This may be related to changes in habitat conditions that diminish competition from the existing composition of the phytocoenosis. The undergrowth of communities featuring invasive species is composed of species preferring habitats with higher light availability, with a higher soil pH and a richer trophic status, but there are few species of more moist habitats. The broad habitat range characteristic for small balsam (as regards light and soil pH) combine with its preference for drier mesophilous sites and a marked capacity to disperse providing for the expansion of the species, which in fact comes to dominate in disturbed forest communities. On a more-positive note, the analysis shows how the degradation of riparian hardwood forests could be limited, if only their natural habitat conditions can be assured.

Ecological Status of Juglans cinerea in New Brunswick.

Butternut (Juglans cinerea L.), an early successional riparian hardwood species native to Canada and the United States, is under serious threat from a nonnative fungal pathogen, Ophiognomonia clavigignenti-juglandacearum. Since it was first reported in Canada in 1990, this fungal pathogen has spread rapidly and established in New Brunswick in 1997. Apart from the first report in 1997 and another in 2004, no surveys have been conducted to assess the spread of the pathogen in the province. The purpose of this research was to survey butternut throughout its range in New Brunswick, evaluate disease occurrence as well as tree health, and investigate the impact of different topographic and tree health factors on canker incidence. Results showed that the disease has spread throughout the range of butternut in New Brunswick. The disease likely only recently (2007) spread to the northeastern-most populations, given that lower rates of canker occurrence and higher health ratings are found further away from the point of initial occurrence of the disease. Although canker incidence is high throughout the province, tree dieback is minimal, and trees still producing nuts could support opportunities for ex situ conservation. Because of the rate of pathogen spread in the province, implementing a tree improvement strategy might be the only means for maintaining the butternut genome on the landscape.

Barred Owl Effects on Spotted Owl Resource Selection: A Meta‐Analysis

ABSTRACTWe quantified the effects of barred owls (Strix varia) on fine‐scale (~2 ha), spatially explicit selection of putative foraging habitat by 175 radio‐tagged northern spotted owls (Strix occidentalis caurina) from 1998 to 2012 in western Oregon and northern California, USA. We constructed annual nighttime discrete‐choice resource selection functions (RSFs) for northern spotted owls in 8 study areas. We compared RSFs from pooled data from 4 study areas where barred owls were absent or rare (≤14% of spotted owl territories potentially influenced by barred owls) with RSFs from 4 study areas where barred owls were abundant (≥89% of spotted owl territories potentially influenced by barred owls), and we conducted a meta‐analysis of all 8 study areas. Top‐ranked RSFs for individual study areas indicated that the relative probability a forest patch was selected by northern spotted owls for foraging was most strongly associated with basal area of large coniferous trees (≥66 cm diameter at breast height [dbh]) or quadratic mean diameter (QMD, the diameter of trees of average basal area) of all coniferous trees. The influence of such trees was non‐linear, usually quadratic, in 7 study areas, suggesting that an optimal basal area of large‐diameter trees or QMD may be associated with selection of foraging patches. The relative probability of selection of such trees decreased nonlinearly with increasing distance from nest sites in ≥4 study areas. Basal area of all or specific hardwood tree species was linearly associated with increases in the relative probability of a patch being used for foraging in 7 of 8 study areas. The relative probability of selection was also positively associated with densities of large snags (&gt;50 cm dbh), coarse woody debris, and undergrowth shrubs in most study areas where we estimated those covariates. The relative probability that a patch was selected decreased nonlinearly with increasing distance from streams (7 study areas), increasing elevation (5 study areas), and decreasing slope (5 study areas). Barred owls exerted strong effects on habitat selection by spotted owls, which may have attempted to minimize interference competition via spatial segregation. Spotted owls occupying study areas where barred owls were abundant used foraging patches at greater distances from streams, at greater distances from nest sites, and on steeper and warmer slopes than those occupying areas with few or no barred owls. In addition, northern spotted owls in areas where barred owls were abundant exhibited reduced selection for large‐diameter trees close to nest sites but may have compensated by increasing use of large trees in home‐range locations distant from nest sites. Programs that seek to improve the link between spotted owl demographic performance or occupancy rate and habitat conditions should account for the influences of fine‐scale variation in vegetation composition and structure and physiographic conditions. Forest managers may contribute to spotted owl conservation via silvicultural prescriptions that retain coarse woody debris and large snags, promote undergrowth shrubs, and retain intermediate to high densities of large, old shade‐intolerant early‐seral trees and riparian hardwoods within and beyond core areas surrounding nest sites. © 2019 The Wildlife Society.

Łęgi jesionowo-wiązowe w dolinie środkowej Wisły – stan ekosystemów pozbawionych zalewów i wytyczne do działań ochronnych = Riparian hardwood forests in the valley of the middle Vistula – ecosystem condition in the absence of flooding, and guidelines for protection

Riparian hardwood forests of Quercus robur, Ulmus spp and Fraxinus spp that are present along major rivers are valuable communities protected by the EU Habitat Directive and recommended for monitoring. Part of the reason for that is relative rarity on the scale of Europe as a whole, and also in Poland. This in turn reflects the way in which fertile habitats were, in their majority, deforested long ago, drained and changed into grasslands or arable land. Additionally, the greater part of these habitats have lost their specific features, as a result of river engineering and – primarily – the construction of the river embankments that have acted to limit flooding and alluvial processes, in that way also initiating change in the composition of both soils and plant communities. Specifically, this article presents selected results of the research project: Riparian hardwood forest services in the middle Vistula river valley. One of the main objectives thereof was to assess the condition of forest ecosystems from which flooding has now been absent for at least 50 years, as well as to prepare guidelines for actions necessary to maintain or restore their diversity, and proper ecological and biological functions. Our research questions therefore revolved around components of riparian hardwood forest ecosystems have been most changed … and why? The research was conducted in six riparian hardwood forests (to date unmonitored) located in the valley of the middle Vistula (in Mazowieckie voivodship). Relevant work was carried out using the standard monitoring guidelines – as primarily based on an assessment of vegetation composition and structure together with water conditions. However, in the work in question, these were augmented by additional analyses allowing for detailed characterisations of soil, the topoclimate, and the species diversity achieved by selected groups of invertebrate (Hymenoptera: Apidae: Bombus and Haplotaxida: Lumbricidae). The communities selected represent multi-functional, species-rich forests. Extensive use of the studied riparian mixed forests ensures that deadwood resources are quite considerable. Moreover, the studied forests exert a strong impact when it comes to mitigation of climate locally. The observed soil types indicate fertile and biologically-active habitats, as well as to soil development largely determined by the height of the groundwater table causing the gleyic process in the lower parts of profiles. However, in some forest patches it is possible to note transformations related to habitat drying, with significant canopy gaps and disturbances of topsoil and the undergrowth. There was a great abundance of invasive alien plant species (mainly Impatiens parviflora) in the undergrowth. Moisture conditions have an impact on the occasional occurrence of Lumbricidae associated with wet and flooded areas. In turn, the domination by Bombus of open-habitat species indicates a transformation of forest structure, and the patchy nature of riparian forests located in a rural landscape. The obtained results demonstrate that protective actions should focus on ensuring adequate soil-moisture conditions, and on restoring the natural structure of vegetation with a view to invasions of alien species being hampered. Another important issue is the proper use of land adjacent to forest patches, as fallows prove to be invaded quickly by the kenophytes preferring abandoned and disturbed places.

Restoration of a Danube floodplain forest: what happens to species richness of terrestrial beetles?

Along the upper Danube, between river kilometer 2,472 and 2,464 (Bavaria, Germany), a managed hardwood forest was reconnected to the river via a newly carved floodplain channel. We report the stepwise alteration of the diversity of terrestrial beetles for six successive years from 2007 to 2012. In a 2-year preliminary period (2007–2008), we recorded the baseline stage before the technical measures were implemented (2009–2010) and the onset of restoration occurred (2011–2012) with a continuous water flow in the new channel and seven flooding events. Each sample plot was equipped with a pitfall trap, an emergence photo-eclector, an arboreal photo-eclector, and a flight interception trap in breast height and in the canopy, respectively. The beetle communities act as an indicator to detect possible disturbance events when a riparian hardwood forest is stepwise transformed to become a new floodplain ecosystem. Within the 6-year study period, we trapped 62,107 individual beetles, representing 85 families, 544 genera, and 1,191 species. Compared to the baseline stage, the abundance and the number of species decreased, including rare and red list species. On functional level, the species decline was particularly pronounced for zoophagous and mycetophagous species. Finally, we suppose that the 2-year period since the launch of the new channel is too short for the establishment of a beetle community adjusted to the terrestrial part of the developing new floodplain forest.

Have changing forests conditions contributed to pollinator decline in the southeastern United States?

Two conservation goals of the early 20th century, extensive reforestation and reduced wildfire through fire exclusion, may have contributed to declining pollinator abundance as forests became denser and shrub covered. To examine how forest structure affects bees we selected 5 stands in each of 7 forest types including: cleared forest; dense young pines; thinned young pines; mature open pine with extensive shrub/sapling cover; mature open pine with extensive herbaceous plant cover and little shrub cover; mature upland hardwood forest; and mature riparian hardwood forest. We sampled bees during the 2008 growing season using pan traps and measured overstory tree density, understory herbaceous plant and shrub diversity and cover, light penetration, and leaf area index. Numbers of bees and numbers of species per plot were highest in cleared forest and in mature pine stands with an herbaceous plant understory. Estimates of asymptotic species richness were highest in mature riparian hardwood forests, cleared forests and open pine forests with an herbaceous plant understory. Bee communities in the cleared forests and in the mature pine with an herbaceous plant understory were grouped together in ordination space which was consistent with perMANOVA results. The best predictor variable for bee species density was total tree basal area which was negatively correlated (r2=0.58), while the best model for predicting bee abundance (r2=0.62) included canopy openness, plant species density (both positively correlated) and shrub cover (negatively correlated). Our results combined with many others show that thinning forests combined with shrub control provides good bee habitat, is compatible with habitat restoration and management for other species, and the resulting forests will be healthier and less susceptible to old (e.g., southern pine beetle, Dendroctonus frontalis) and new (European woodwasp, Sirex noctilio) threats.

Stream and shallow groundwater nutrient concentrations in an Ozark forested riparian zone of the central USA

Characterizing spatiotemporal variations in surface water (SW)–shallow groundwater (GW) nutrient concentrations is important to predict stream ecosystem responses to disturbance. Unfortunately, there is a lack of such information from mixed-deciduous semi-karst hydro-geological regions. Nitrate (NO3−), total phosphorous (P), potassium (K) and ammonium (NH4+) concentrations were monitored in a case study between an Ozark stream and riparian hardwood forest GW over the 2011 water year in the central USA. Average SW NO3−, P, K and NH4+ concentrations were 0.53, 0.13, 3.29 and 0.06 mg L−1, respectively. Nine meters from the streambank, average GW NO3− concentration was 0.01 mg L−1, while P, K and NH4+ concentrations were 0.03, 1.7 and 0.04 mg L−1, respectively. Hyperbolic dilution model results indicated that NO3− and K exhibited dilution behavior, while NH4+ had a concentration effect and P was hydrologically constant. Observed seasonal NO3− concentration patterns of winter maxima and summer minima in SW (1.164 and 0.133 mg L−1) and GW (0.019 and 0.011 mg L−1) were supported by previous studies yet exhibited distinct semi-karst characteristics. Results indicate that in addition to relatively low residence time, lower nutrient concentrations in GW (relative to SW) may suggest that shallow GW flow processes are important for vegetation removal and retention of nutrients from streams in semi-karst shallow groundwater systems of the central USA.

Multi-scale Roost Site Selection by Rafinesque's Big-eared Bat (Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius) in Mississippi

Abstract Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM) are species of concern whose current population statuses are unknown. Bottomland hardwood forests are important roosting habitat for RBEB and SEM; however, ≥80% of these forests have been cleared or degraded in Mississippi. Limited information on roost site requirements exists across either species ranges; therefore, we conducted roost surveys for RBEB and SEM in bottomland and riparian hardwood forests on Noxubee National Wildlife Refuge, Legion State Park, and Tombigbee National Forest, Mississippi, during winter 2009–2010 and spring 2010. To compare seasonal roost selection for each species we compared tree species, used 95% confidence intervals (CIs) for three tree variables [diameter at breast height (DBH), cavity volume, and opening area] and logistic regression for four landscape variables (elevation, slope, distance to nearest stream, and distance to nearest road). We used Aka...

A 300-year successional sequence in an eastern United States riparian hardwood forest1

Abstract Hardwood-dominated riparian forest was surveyed in 83 quadrats on 3 floodplains, 11 lower terraces, and 8 upper terraces along 11 km of Zoar Valley Canyon, a minimally disturbed segment of 5th–6th order Cattaraugus Creek in western New York State, USA. Increment core-based stand ages from 8 to >300 years constituted the longest middle-order riparian sequence yet studied in the East. Comparisons of aerial images starting in 1929 with present-day increment cores indicated trees have reached breast height and persisted on recent lower terraces within at most 6–27 years after deposition, suggesting landform age and type associated primary succession rather than flood-regime driven secondary succession or maintenance of early seral stages. In 2009, the second largest flood since 1940 caused only modest damage even to floodplain stands, supporting this premise. Regressions of stand characteristics on age across the 300-year sequence revealed logarithmic increases in tree diameter and height, stand basa...

Riparian buffer located in an upland landscape position does not enhance nitrate-nitrogen removal

Relatively narrow (<50m) riparian buffers strategically reestablished in correct landscape positions have been shown to significantly reduce agricultural non-point source pollution to streams. Because of this, conservation programs have been established to encourage landowners to enroll lands near surface waters to improve water quality. Former cropland enrolled in a conservation program was evaluated to determine its effectiveness in reducing nitrate-nitrogen (NO3−-N) in shallow groundwater. This conservation buffer (CB) was up to 80m wide and was planted with loblolly pine (Pinus taeda). It was situated upslope of an existing 30–60m wide riparian hardwood forest buffer (EHB) located within the floodplain of an intermittent stream. Shallow groundwater NO3−-N, groundwater hydrology, total organic carbon, and soil redox potential were measured throughout both the CB and the EHB for 18 months. Groundwater NO3−-N concentrations, often 5–15mgL−1 within the CB, were not significantly reduced from concentrations that entered from the agricultural field edge. However, a decrease in NO3−-N concentration was observed within the EHB (17–83%). The hydrology of the CB coupled with relatively low organic carbon contributed to a low denitrification potential and lack of NO3−-N reduction compared with the EHB. While the CB enrollment likely provided additional habitat benefits it did not appear to provide treatment of groundwater NO3−-N. It is our conclusion that landscape position is a more important defining variable for buffer site selection than buffer width if NO3−-N reduction is a primary goal.

Töredékes tölgy-kőris-szil ligetek a Zákányi-dombokon (Knautio drymeiae-Ulmetum Borhidi et Kevey 1996)

The Zákány Hills are situated along the Dráva River in southwestern Hungary, where I collected 10 vegetation samples and studied the phytosociological characteristics of the riparian hardwood forest (Knautio drymeiae-Ulmetum). Its strongly fragmented stands occur primarily on the riverside foothills, where the thick gravel deposit is covered with a shallow layer of loess. These forest fragments are in contact most often with alder gallery forests (Carici pendulae-Alnetum) and oak hornbeam forests (Anemoni trifoliae-Carpinetum). The stands host some herbaceous species (Anemone trifolia, Lamium orvala) that occur nowhere else in the country and indicate sub-Mediterranean and Illyrian influences.