Riparian Forest Management Research Articles

Microbial community structure of decayed trunks of Populus euphratica desert riparian forests in the lower Tarim River, Xinjiang, China

Rich microbial communities are associated with tree decay, and they markedly impact the degradation of tree species and material cycling within ecosystems. The native Populus euphratica forests along the lower Tarim River of China are mostly mature or over-mature, with many tree trunks exhibiting features of extensive cavity decay and slow regeneration. In this study, a growth cone was used to drill a wood core at varying degrees of decay, and 16S and internal transcribed spacer techniques were used to identify the microbial structure (fungi and bacteria) within the wood core. Changes in the trunk microbial community under varying decay conditions were also examined. For healthy, lightly decayed, and heavily decayed trunk, the dominant bacterial and fungal phyla were Firmicutes and Actinobacteria, Ascomycota, and Basidiomycota, respectively. As decay progressed, the alpha diversity index of the microbial community tended to decline. The maximum number of differential species was found in healthy trunks, where leaner discriminant analysis effect size (LEfSe) of fungi and bacteria revealed 1 and 15 different species, respectively. Species network analysis showed that interspecific linkages were more complex within bacterial communities than within fungal communities, with the complexity of fungal interspecific relationship increasing as decay progressed. The microbial communities of P. euphratica trunks differed significantly with the varying degrees of decay. Microbes such as Ralstonia may also play key roles in the decay process. In addition to providing a foundation for the sustainable management of desert riparian forests, investigating the mechanisms through which microbial communities influence the deterioration of P. euphratica trunks provides information about the general health of P. euphratica forests.

Participatory intention and behavior towards riparian peri-urban forests management; an extended theory of planned behavior application.

Peri-urban forests play crucial role in quality of life and environment for citizens. To effectively utilize the services provided by these forests, it is essential to establish an integrated forest management system that aims to achieve a balance of all ecosystem services. This can be accomplished through a participatory approach that involves key citizen stakeholders. Mountaineers shape a specific group which have showed high pro-environmental behaviors to protect natural resources. This research aimed to examine the influencing factors on mountaineers' intention to participate and their actual behavior in the management of riparian peri-urban forests in this field using extended theory of planned behavior. Environmental values and perceived barriers were added to original model as additional components to enhance its explanatory power. A sample size of 416 individuals was surveyed using a questionnaire. Data was analyzed using Smart-PLS. The findings of the analysis revealed that the developed model accounted for 75.2% of the variance in mountaineers' intention and 67.8% of behavior. The results demonstrated that three main components of model including attitudes, subjective norms and perceived behavioral control significantly influenced individuals' intentions to participate in peri-urban forests management. Furthermore, intentions were cleared to have a positive influence on actual behavior in this context. Additionally, environmental values were found to be positively correlated with individuals' intentions but not statistically significant behavior toward participate in urban forest management. Perceived barriers were found to have a negative impact on individuals' intentions toward participate in urban forest management. The perceived barriers and behavior had not statistically significant relationship. The results of study provide valuable insights for the development of effective management strategies to promote mountaineers' participation in riparian PUFs management. The study emphasizes the importance of environmental education and awareness campaigns targeted at mountaineers.

Pool Formation and The Role Of Instream Wood In Small Streams In Predominantly Second-growth Forests.

Extensive and intensive forest harvesting during the 20th century often had, and continues to have, negative impacts on stream structure and ultimately fish. Loss of instream wood and pools has been identified as a pathway by which riparian forest management can negatively impacts salmonids. Passive riparian restoration (allowing forests and streams to recover through natural processes) through the use of riparian buffers when conducting forest harvests has often been employed to promote stream habitat recovery. In this study, we evaluate the effects of 25 years of passive restoration on instream wood and pool recovery in 74 reaches in small streams (1st through 3rd order) across three channel types (pool-riffle, step-pool, and cascade) in a predominantly second-growth forest. Gradient and stream size were the most important variables for determining pool density, while stream size was the most important variable for determining pool depth. Instream wood formed 39% of pools in pool-riffle, 30% of pools in step-pool and 25% of pools in cascade channels types. Instream wood volume had a significant (R2 = 0.261, P ≤ 0.001) positive relationship with pool volume in wood-formed pools. Dimensions of individual wood pieces were associated with their likelihood of pool formation: for each additional 1 meter length within the bankfull channel the odds of forming a pool increased by 25.6%, and for each additional centimeter in diameter the odds of pool formation increased by 2.0%. When compared with studies conducted in both second- and old-growth forests, we concluded that streams associated with second-growth forests hadve both reduced densities and sizes of instream wood and pools. Young forests are likely continuing to negatively impact stream habitat and fish populations. Because riparian zones in many forests are now dominated by relatively young forest stands, and given the timeline for recovery using passive restoration alone (e.g., 100 s of years in Pacific Coastal forests), active restoration could be explored to accelerate instream wood and pool recovery.

Social Perception of Riparian Forests

Riparian forests are ecotones that differ from the surrounding landscapes, delineating the transition from terrestrial ecosystems into aquatic ones. Riparian forest management has been recognized as a possible method for promoting several ecological functions. In order to develop a sustainable and resilient relationship between river riparian forests and society, it is necessary to analyze the sociocultural dimension of riparian zones. The aim of this study was to assess the social perceptions of riparian forests. A total of 734 respondents (61% woman), inhabitants from the region of Latvia, where there is a rather dense network of streams, were surveyed. Respondents represented various education levels, ages, and economic backgrounds. Riverine forests tend to be a less popular option for recreation compared with other types of forests. The most popular activities were walking and swimming. “Forest and water bodies” was not among the main topics that respondents were concerned about. Regarding rivers and riparian forests, the obstructed movement of fish to spawning grounds was recognized as the most important problem, but the least concerning was the reduction of water tourism and fishing opportunities. Dynamic river basin and river bank management could be a possible solution to restoring eligible locations for recreational activities, at least along some parts of rivers, and for improving the state of riparian ecosystems simultaneously.

Vegetation Affecting Water Quality in Small Streams: Case Study in Hemiboreal Forests, Latvia

Riparian forests are important ecosystems located along the margins of freshwaters. Riparian zones provide many ecosystem services, such as nutrient modification, erosion and temperature control, leading to improvements in water quality in adjacent water ecosystems. In many areas, riparian forest management is restricted to improve adjacent water quality. The potential influence of forest management on water quality of small streams was assessed by analysing species composition and structural diversity in riparian forests. We collected data in riparian forests along 15 streams in the eastern Baltics (Latvia) with different water quality classes. We used detrended correspondence analysis and indicator species’ analysis to determine relationships between woody plants and understory vegetation. We also used ADONIS and ANOSIM analysis to determine possible factors that affect species composition. Our results suggested that water quality is affected by ground vegetation, which in turn was altered by stand density and total yield. Site-specific decision making in management is required in riparian forests to ensure the required conditions in the streams, because species composition differs between sites, dominant tree species and stand parameters (density, total yield, stand age). Introduction of Betula pubescens Ehrh. in coniferous stands is favourable to ensure litter fall quality and provide shade for streams during summer.

Riparian reforestation on the landscape scale: Navigating trade‐offs among agricultural production, ecosystem functioning and biodiversity

Abstract Stream–riparian networks are subject to multiple human pressures that threaten key functions of aquatic and terrestrial ecosystems, drive habitat and diversity losses, affect riparian connectivity and cause stakeholder conflicts. Designing riparian landscapes in a way that they can simultaneously meet multiple competing demands requires a clear understanding of existing trade‐offs, and a landscape‐scale perspective on the planning of reforestation measures. This study applied a landscape optimization algorithm for allocating riparian forest management measures in the intensively used agricultural catchment of the Zwalm River (Belgium). We optimized forest allocation to improve stream ecological quality (EPT index), functional diversity (diatoms) and riparian carbon processing (cotton‐strip assay), while minimizing losses in agricultural production potential. Regression models were developed to predict the target indicators for 489 segments of the Zwalm riparian corridor, using spatial variables on three different scales. For each riparian segment, we developed spatially explicit management measures, representing different intensities of riparian reforestation. The allocation and combination of these measures in the riparian corridor were optimized to identify (a) trade‐offs among the target indicators, (b) priority regions for reforestation actions and (c) the required reforestation intensity. The results showed that all target indicators were affected by the area share of riparian forests and its landscape‐scale configuration. Reforestation of the Zwalm riparian corridor could significantly improve indicators for biodiversity and ecosystem functioning (e.g. up to +96% for EPT index), but would lead to a strong trade‐off with agricultural production. By optimizing the placement of management measures, we showed how these trade‐offs could be best balanced. The headwater regions of the Zwalm were identified as priority regions for reforestation actions. Facilitating connectivity among and further expansion of existing forest patches in the Zwalm headwaters showed to improve ecosystems with minimized trade‐offs. Synthesis and applications. This study demonstrates, for the first time, the potential of landscape optimization algorithms to support the management and design of multifunctional stream–riparian networks. We identified riparian reforestation solutions that minimized trade‐offs between specific natural values and societal needs. Our spatially explicit approach allows for an integration into spatial planning and can inform policy design and implementation.

Evaluation of sunlight penetration through riparian forest and its effects on stream biota

Riparian streams contain various types of terrestrial organic and inorganic matter that are continuously transported from hillsides. Riparian forest forms alongside streams and blocks direct sunlight. It also supports the formation of various in-stream habitats, leading to the diversification of in-stream benthic invertebrates. In this study, sunlight passing through riparian forest canopy was measured and its relationship with the biota in the stream was analysed. Then, the light conditions favourable to stream biota were clarified for the purpose of riparian forest management. Differences in light conditions, chlorophyll a levels, and the richness of benthic invertebrates were observed, even in areas with stream widths of less than 5 m. As the canopy was closed in the upper stream area, intense sunlight was required to increase the solar radiation and chlorophyll a levels. Family richness was related to amounts of chlorophyll a. In contrast, in lower stream areas, because of the many gaps in the forest canopy, intense light was not necessary to increase the solar radiation, amounts of chlorophyll a, or family richness. Afternoon sunlight led to greater illuminance and higher chlorophyll a levels than did morning sunlight. The riparian forest on the west side of the stream was essential, as it blocked strong direct afternoon sunlight in summer. In riparian forest management, sunlight direction should be considered while paying attention to the composition of riparian forest. • Chlorophyll a levels differed even in areas with stream widths of less than 5 m. • Benthic invertebrates also differed even in areas with stream widths of less than 5 m. • Intense sunlight was required to increase solar radiation and chlorophyll a levels. • Afternoon sunlight led to greater illuminance and higher chlorophyll a levels. • For the riparian forest management, sunlight direction should be considered.

A riverscape approach reveals downstream propagation of stream thermal responses to riparian thinning at multiple scales

AbstractHydrological connectivity in river networks influences their response to environmental changes as local effects may extend downstream via flowing water. For example, localized changes in riparian forest conditions can affect stream temperatures, and these effects may propagate downstream. However, studies evaluating stream temperature responses to riparian forest management have not considered cumulative effects across entire watersheds. Improved understanding at these scales is needed because land managers are increasingly required to consider broad‐scale consequences of their actions. To address this question, we deployed a high‐density network of sensors across watersheds to examine stream temperature responses to experimental thinning of riparian forests. A riverscape approach that combined high‐resolution data throughout the study watersheds made it possible to examine local and downstream patterns of stream temperature at multiple spatial and temporal scales. We found that local responses of temperature to thinning varied widely depending on the intensity of thinning treatments. Downstream propagation of local responses extended from 100 m to over 1000 m and depended on the magnitude of the local response. We characterized these responses as a series of waveforms. In the watersheds with more intensive thinning, thermal responses occurred most often as an extended pulse where downstream increases in temperature attenuated gradually at variable distances. Although we observed no evidence of cumulative effects associated with thinning at the downstream extent of stream networks, effects emerged where thinning treatments were closely spaced (<400 m apart) and local warming did not dissipate with downstream distance. In a watershed with less intensive thinning, there was either no response or a localized pulse with no downstream propagation. Collectively, these patterns suggest that riparian forest thinning influenced downstream thermal conditions to varying extents depending on the intensity, scale, and spatial proximity of treatments. We found that a multiscale riverscape approach and conceptual framework based on contrasting waveforms provided a foundation for understanding the cumulative watershed effects of riparian thinning. The approach developed here can be adapted more broadly when evaluating downstream propagation of local changes in river networks and has direct implications for guiding restoration in riparian ecosystems.

Western Yellow‐Billed Cuckoo Nest‐Site Selection and Success in Restored and Natural Riparian Forests

ABSTRACTThe western distinct population segment of yellow‐billed cuckoo (Coccyzus americanus; western cuckoo) has been extirpated from most of its former breeding range in the United States because of widespread loss and degradation of riparian cottonwood (Populus spp.)‐willow (Salix spp.) forests. Restoration and management of breeding habitat is important to the recovery of this federally threatened species, and identification of high‐quality breeding habitat can help improve the success of recovery. In 2005, the Lower Colorado River Multi‐Species Conservation Program, a long‐term, multi‐agency effort, was initiated to maintain and create wildlife habitat within the historical floodplain of the lower Colorado River (LCR) for federally endangered and threatened species, including western cuckoos. We conducted an empirical, multi‐scale field investigation from 2008–2012 to identify habitat characteristics selected by nesting western cuckoos along the LCR. Multiple logistic regression models revealed that western cuckoos selected nest sites characterized by increased densities of small, native, early successional trees measuring 8–23 cm diameter at breast height, and lower diurnal temperature compared to available habitat in restoration and natural forests. Nesting cuckoos selected sites with increased percent canopy closure, which was also important for nest success in restoration sites along the LCR. Our results show habitat components selected by nesting western cuckoos in restoration and natural riparian forests and can help guide the creation, enhancement, and management of riparian forests with habitat conditions necessary to promote nesting of western cuckoos. © 2021 The Wildlife Society.

Using LiDAR to assess transitions in riparian vegetation structure along a rural‐to‐urban land use gradient in western North America

AbstractRiparian forests are essential for stream ecological processes in arid and semiarid regions, however, they are often highly altered by the rapid expansion of urban areas. To maintain riparian ecosystems services, it is important to better understand the effects of urbanization on riparian forests. We quantified the three‐dimensional (3D) structure and woody species composition of a riparian corridor in Utah, USA, to evaluate patterns of vegetation along stream reaches that flow through distinct hydrologic domains (with gaining and losing reaches) and through a rapid rural‐to‐urban gradient. By using LiDAR imaging and field observations, we explore the extent to which the riparian vegetation structure follows patterns of topography linked to energy and water subsidies and patterns of human influence along the stream. Whereas natural reaches of Red Butte Creek were characterized by native vegetation and typical riparian species (e.g., Betula occidentalis), urbanized reaches had higher numbers of introduced plants (e.g., Acer platanoides) and more upland species (e.g., Quercus gambelii). Urban reaches were also characterized by exceptionally high trees (>18 m) in older residential neighbourhoods. In the natural area, canopy height was negatively correlated with height above the river (HAR). Additionally, we found higher cover and taller canopies on north‐facing aspects. These results show that LiDAR data, in combination with ground observations, can reveal strong influences of hydrology as well as land use in different canopy layers of riparian forests. We suggest that the decision making of individual landowners shapes vegetation beyond natural hydrological patterns, with implications for riparian forest management and restoration.

Post-wildfire riparian forest recovery processes along a regulated river corridor

Riparian forest recovery was monitored over a 23 km study site that encountered a mixed low to moderate severity wildfire on the floodplain that was followed by a sequence of flows ranging from below bankfull to a 50-year flood on the regulated South Fork Boise River, Idaho, USA. The goals of the study were to examine the dominant mechanisms of post-wildfire riparian forest regeneration along the river corridor in relation to upstream dam operations. Results are put in context with trends occurring in the regulated river system over the past 70 years that exemplify post-impoundment floodplain dynamics. Aerial imagery and field surveys were used to examine trends in geomorphic and forest response related to flow regulation, riparian wildfire, and a 50-year flood. Additionally, a one-dimensional sediment transport model was employed to assess seedling recruitment related to local and reach-scale erosional and depositional processes over a five-year period following the wildfire. A conceptual model is presented to illustrate riparian forest response to the interacting influences of fire severity and flood disturbance to help guide post-wildfire riparian forest management activities.Aerial imagery between 1957 and 2011 shows that flow regulation after dam closure led to channel narrowing of 62% of historic active channel width and an associated increase in floodplain tree density of 59%. This expansion of forest cover on the floodplain was at the expense of seedling recruitment habitat for pioneer species in the Salicaceae family that require bare sediment, light exposure, and access to the shallow groundwater. A 2013 riparian wildfire led to substantial top kill on the floodplain that provided a disturbance for potential seedling recruitment. However, dam releases during average and wet hydrologic conditions led to only 5% of the total observed seedling recruitment in the system occurring on the floodplain due to the limited magnitude of flood disturbances following the burn, highlighting the importance of the sequence of environmental flows immediately following riparian wildfire. Alternatively, 95% of seedling recruitment occurred within the active channel and was directly related to sediment transport processes. Post-wildfire related debris flows were responsible for providing the requisite sediment supply to the channel in an otherwise sediment supply-limited, regulated river system. Resultant sediment deposition was responsible for providing 100% of seedling recruitment habitat in the active channel during dam releases in average hydrologic conditions, whereas deposition accounted for 84% and erosion accounted for 16% of observed recruitment habitat during wet hydrologic conditions.

How much boreal lake shoreline is burned by wildfire? Implications for emulating natural disturbance in riparian forest management

Understanding of post-fire residual vegetation patterns is important when shoreline vegetation management aims to emulate natural disturbance (END) patterns. To assess the impacts of fire, lake and lakeshed sizes on the burning pattern of shorelines and lakesheds, we quantified the burned shorelines and post-fire residual vegetation patterns in the lakesheds of 123 lakes of Ontario affected by 26 wildfires between 2005 and 2007. We used ArcGIS and Ontario’s Enhanced Forest Resources Inventory (eFRI) GIS data to digitize burn patterns. The lake catchments for all lakes were delineated using ArcGIS via lake, river, and elevation data from the Integrated Hydrology geodatabase (MNRF, 2016). The shorelines of fire impacted lakes were generated from the eFRI polygon feature classes, and the polylines were then split according to the digitized burn pattern polygons by running a geometric intersection with these data. The results of this study show that the percentages of burned shorelines and lakesheds are positively correlated with the size of fire and negatively correlated with the sizes of lake and lakeshed. However, irrespective of the size of fire, lake or lakeshed, shorelines are not left completely unburned, which is contrary to existing practice of retaining fixed-width shoreline buffers. It may imply that under END based management, forest harvesting can be possible up to the shorelines in some areas of the landscapes that are left unharvested under a fixed-width riparian buffer management system. However, areas of strong hydrological connectivity between land and water serve as biogeochemical control points and require protection from disturbance during forest management planning and operations. We suggest that GIS-based models developed based on the hydrological and topographical features associated with the unburned shorelines and lakesheds might be useful to predict shoreline residual forest pattern and facilitate END based shoreline forest management.

An unexpected source of invertebrate community recovery in intermittent streams from a humid continental climate

Abstract Intermittent streams are naturally dominant landscape features of Mediterranean and arid regions, but also occur more and more in humid climates, such as in the Czech Republic. Organism abilities to cope with drying (i.e. resistance forms) have been quantified in naturally intermittent streams from Mediterranean and arid regions, in which long‐term flow intermittence patterns have promoted physiological adaptations. In contrast, the capacity of aquatic communities to persist without requiring resistance adaptations under recent intermittent flow regimes in more humid climates is virtually unexplored, along with its contribution to community recovery upon rewetting. Here, we addressed the ability of aquatic invertebrates devoid of specific desiccation‐resistance forms (e.g. cysts or eggs) to cope with climate change‐induced flow intermittence from rivers in continental climate. Owing to the high relative air humidity, the importance of riparian cover and the short duration of drying events, we expected taxonomically and functionally rich communities to persist in the dry streambed during phases with no surface water and to contribute to community recovery upon flow resumption. To explore these ideas, we collected invertebrate communities in the riverbeds before, during and after drying from 10 intermittent rivers in the Czech Republic. We quantified the pool of organisms remaining alive in the dry riverbeds and determined its taxonomic and functional contribution to the recovery of benthic communities upon rewetting. Of the organisms collected, 83%, belonging to 22 taxa, were able to survive during the dry phase without producing desiccation‐resistance forms. This pool of organisms contributed substantially both taxonomically and functionally to the quick recovery of benthic communities. The exponential decrease in taxonomic and functional richness implies an initial quick loss of sensitive taxa, while a pool of less sensitive taxa persisted long in the dry riverbeds, hence contributing to the fast community recovery upon rewetting. Survival rates of active aquatic macroinvertebrates devoid of specific desiccation‐resistance adaptations have rarely been quantified. Probably promoted by benign environmental conditions prevailing on dry riverbeds in this study, their survival demonstrated the need to protect communities in dry riverbed and their adjacent riparian environments so that assemblages can recover rapidly from short periods without river flow. Riparian forest management along intermittent streams from continental climates could help conserve the value of dry streambeds as a source of resilience for riverine communities.

Stream Conditions after 18 Years of Passive Riparian Restoration in Small Fish-bearing Watersheds.

Many of the ecological processes in the riparian forests and streams across the Pacific Northwest have become impaired through production forestry practices common prior to the 1990s. Some of these practices included forest harvest without stream buffers, removal of instream wood, road construction and use, and harvesting large proportions of watersheds. Passive ecological restoration (the use of natural processes of succession and disturbance to alleviate anthropogenic impacts over time) is a common practice used in the management of riparian forests previously subjected to production forestry. Eighteen years after the implementation of passive restoration of riparian forests, we used four common stream indicators (stream temperature, canopy closure, instream wood, and salmonid densities) to assess the effects of restoration in small fish-bearing streams. Summer stream temperatures have decreased below unmanaged reference levels, whereas riparian forest canopy closure has increased beyond that in reference watersheds. Instream wood and age-1 or older salmonids appear to be either stable at reduced levels or declining, compared with production forestry and unmanaged reference watersheds. Overall, second-growth riparian forests need more time to develop allowing more light into streams (increasing primary productivity), while also allowing for the continuous recruitment of larger pieces of instream wood (improving habitat for salmonids). Using only passive restoration, stream conditions in second-growth forests are unlikely to increase salmonid production in the near future.

Gap dynamics of natural Populus euphratica floodplain forests affected by hydrological alteration along the Tarim River: Implications for restoration of the riparian forests

Due to climate change and excessive human activities, runoff dynamics of the Tarim River in northwest China become more pronounced. Understanding the effects of hydrological alteration on the life strategy and dynamics of the Populus euphratica riparian forests is becoming increasingly important. Forest gaps led by such disturbances change the structure and function of the desert riparian forest ecosystems. However, there is a lack of research on the gap formation and dynamics of this special forest type, for which the main driving force of the gap disturbance has always been unknown. In this study, we investigated several parameters of P. euphratica forest gap, such as gap size, gap age, gap fraction, and gap makers to quantify the gap disturbance regimes in the natural floodplain forests along the Tarim River in arid northwest China. In the middle reaches of the Tarim River, a total number of 263 gap makers and 60 gaps in six 50 m × 50 m plots with a total area of 1.5 hm2 were investigated. The result showed that gap fraction was <5%, and approximately 28.5% of the expanded gaps were from 1.0 to 1.2 in size (ratio of gap diameter to tree height), especially when formed around 1997–2006. The median size of the expanded gap (140.57 m2) in the desert riparian forests was smaller than in tropical forests. P. euphratica was the most abundant gap maker, and its share among gap makers was 12–14 times larger than another species. Furthermore, gap makers contributed to the forest gap size, as shown by a significant correlation between the number of gap makers and the size of expanded gaps, especially those that had been created 50–60 years ago (R2 = 0.455, P < 0.01). The DBH distribution of living trees versus dead trees showed that most P. euphratica mortality occurred in small size classes. However, living trees were equally frequent in large classes, which suggested that large trees were not exclusively injured or died in these P. euphratica stands that were affected by poor habitats, such as water scarcity. We concluded that climate change and anthropogenic activities (increasing water use for irrigation) since the 1970s led to the progressive decrease in water resources at the regional scale and resulted in a higher frequency of forest gaps in the riparian forests along the Tarim River. The results of this study provide useful implications for ecological restoration of P. euphratica to improve sustainable management of desert riparian forests.

Instream large wood loads across bioclimatic regions

Instream large wood in forested rivers creates diverse physical and ecological effects and is a vital component of river process and form. The majority of research on wood in rivers has been conducted within a limited geographic range, raising questions about the applicability of resulting insights. We analyze data from 438 river segments in old-growth or unmanaged forests and 250 river segments in lightly managed forests representing diverse environments. We evaluate whether drainage area, channel width, and channel slope influence instream wood load in unmanaged forests across bioclimatic regions. Here we show that, without accounting for variations across regions, these numeric variables do not correlate significantly with wood loads. When accounting for the influence of all available potential influences on wood load in unmanaged forest rivers, bioclimatic region, drainage area, and channel width are the dominant predictors of wood load, and the relationship between wood load and channel width differs between regions. Combining data across bioclimatic regions, unmanaged rivers have significantly greater wood loads than lightly managed forests. Splitting data by bioclimatic region, unmanaged rivers in the northern dry conifer and northern wet conifer regions have significantly greater wood loads than lightly managed forests, but wood loads in the northern wet deciduous region do not differ between unmanaged and lightly managed forests. Our findings suggest that (i) bioclimatic region is a critical factor in predicting and understanding wood dynamics in rivers, (ii) even historic or relatively light levels of timber harvest and wood removal can create persistent differences in wood loads, and (iii) substantial variation in wood load among river segments within a bioclimatic region suggests that riparian forest and river management should focus on processes that maintain wood loads capable of creating desired physical and ecological effects rather than specified volumes of wood.

Small alteration - big impacts: effects of small-scale riparian forest management on host-parasite dynamics in streams.

Environmental changes and ecological disturbances can have large and unpredictable effects on parasite dynamics. Increasing human impacts on freshwater ecosystems through land use may thus modify the distribution and abundance of parasites and have cascading effects on host populations. Here we tested the effects of small-scale riparian forest management on the nematode Cystidicoloides ephemeridarum and its insect intermediate host Ephemera danica in forested streams. We assessed the impacts of harvesting riparian trees on parasite prevalence and abundance concomitantly with host densities. We also looked at upstream and downstream reaches to document potential cascading effects on unaltered stream sections mediated by aerial dispersal of adult mayfly or downstream drift of E. danica larvae. We show that host densities and parasite levels (prevalence and abundance) increased significantly following riparian tree removal. Overall, parasite densities showed a 6- to 66-fold increase in harvested reaches compared to upstream, pristine reaches. Similar effects were also clear downstream of the disturbance. Thus, despite the small extent of riparian forest alteration along the study streams, both parasite and intermediate host were strongly affected. Small-scale riparian forest management may thus have large, unforeseen impacts on some aspects of freshwater ecosystem structure and functioning that are often ignored. Generally, understanding how human perturbations influence parasites is vital when trying to predict overall impacts on ecosystem structure and functioning, and how changes in infection dynamics may further affect host species.

Monitoring Natura 2000 habitats: habitat 92A0 in central Italy as an example

The evaluation and the subsequent monitoring of the conservation status of habitats is one of the key steps in nature protection. While some European countries have tested suitable methodologies, others, including Italy, lack procedures tested at the national level. The aim of this work is to propose a method to assess the conservation status of habitat 92A0 (Salix alba and Populus alba galleries) in central Italy, and to test the method using data from the Molise region. We selected parameters that highlight the conservation status of the flora and vegetation in order to assess habitat structures and functions at the site level. After selecting the parameters, we tested them on a training dataset of 22 unpublished phytosociological relevés taken from the whole dataset, which consists of 119 relevés (49 unpublished relevés for the study area, and 70 published relevés for central Italy). We detected the most serious conservation problems in the middle and lower course of the Biferno river: the past use of river terraces for agriculture and continual human interventions on the river water flow have drastically reduced the riparian forests of Molise. Our results show that in areas in which forest structure and floristic composition have been substantially modified, certain alien plant species, particularly Robinia pseudoacacia, Amorpha fruticosa and Erigeron canadensis, have spread extensively along rivers. In the management of riparian forests, actions aimed at maintaining the stratification of the forest, its uneven-agedness and tree species richness may help to ensure the conservation status, as well as favour the restoration, of habitat 92A0.

Mapping Temporal Dynamics in a Forest Stream Network—Implications for Riparian Forest Management

This study focuses on avoiding negative effects on surface waters using new techniques for identifying wet areas near surface waters. This would aid planning and designing of forest buffer zones and off-road forestry traffic. The temporal variability in the geographical distribution of the stream network renders this type of planning difficult. A field study was performed in the 68 km2 Krycklan Catchment to illustrate the variability of a boreal stream network. The perennial stream length was 140 km while the stream length during high-flow conditions was 630 km. Comparing the field-measured stream network to the network presented on current maps showed that 58% of the perennial and 76% of the fully expanded network was missing on current maps. Similarly, cartographic depth-to-water maps showed that associated wet soils constituted 5% of the productive forest land during baseflow and 25% during high flow. Using a new technique, maps can be generated that indicate full stream networks, as well as seasonally active streams and associated wet soils, thus, forestry planning can be performed more efficiently and impacts on surface waters can be reduced.

Plant-Pollinator Interactions in a Northwest Arum Related to Plant Traits but not Riparian Forest Management

Abstract Studies in Pacific Northwest riparian forests highlight the role of forest management in conserving target species, but rarely consider impacts on interspecies relationships such as pollination. We investigated plant-pollinator interactions among a native species of rove beetle, Pelecomalius testaceum, and a widespread native wetland plant species in the Pacific Northwest, Lysichiton americanus (western skunk cabbage), in an experimental framework comparing three riparian forest management regimes. Our study addressed the central question: what factors best predict pollinating beetle abundance on L. americanus in a managed Northwest landscape? We measured P. testaceum abundance on skunk cabbages in three riparian treatments in a managed forest: (1) an unlogged riparian zone, (2) a logged riparian zone with a limited buffer corridor, and (3) a clear-cut riparian zone with no remaining corridor. Across this diversity of forest treatments, we also measured inflorescence temperature, foliar damage, a...