Umeå universitets logga

Forests are essential to the global green transition, but intensified management may undermine environmental goals. Continuous cover forestry (CCF) offers an alternative, balancing timber production and ecosystem conservation. We investigated the legislative and technical feasibility of CCF in riparian buffers along freshwaters, where it could potentially restore simplified stands and better protect water. We analyzed EU, national, and global policies identifying barriers and enablers and used GIS data from 11 Swedish sites estimating the share of productive forest converted to CCF under varying buffer widths. Results show CCF in riparian buffers is feasible, with few legislative barriers and several soft enablers. The EU Nature Restoration Regulation is a key enabler, as CCF-managed buffers can contribute to restoration targets, providing opportunities for different property sizes to meet multiple management objectives. Future feasibility depends on EU member states’ implementation of the regulation and alignment of ecological goals with political and economic conditions.

Riparian buffers are the primary tool in forest management for protecting the habitat structure and function of streams. They help protect against biogeochemical perturbation, filter sediments and nutrients, prevent erosion, contribute food to aquatic organisms, regulate light and hence water temperature, contribute deadwood, and preserve biodiversity. However, in production forests of Sweden and Finland, many headwater streams have been straightened, ditched, and/or channelized, resulting in altered hydrology and reduced natural disturbance by floods, which in turn affects important riparian functions. Furthermore, in even-aged management systems as practiced in much of Fennoscandia, understory trees have usually been cleared right up to the stream’s edge during thinning operations, especially around small, headwater streams. Fire suppression has further favored succession towards shade tolerant species. In the regions within Fennoscandia that have experienced this combination of intensive management and lack of natural disturbance, riparian zones are now dominated by single-storied, native Norway spruce. When the adjacent forest is cut, thin (5 - 15m) conifer-dominated riparian buffers are typically left. These buffers do not provide the protection and subsidies, in terms of leaf litter quality, needed to maintain water quality or support riparian or aquatic biodiversity. Based on a literature review, we found compelling evidence that the ecological benefits of multi-layered, mixed-species riparian forest with a large component of broadleaved species are higher than what is now commonly found in the managed stands of Fennoscandia. To improve the functionality of riparian zones, and hence the protection of streams in managed forest landscapes, we present some basic principles that could be used to enhance the ecological function of these interfaces. These management actions should be prioritized on streams and streamside stands that have been affected by simplification either through forest management or hydrological modification. Key to these principles is the planning and managing of buffer zones as early as possible in the rotation to ensure improved function throughout the rotation cycle and not only at final felling. This is well in line with EU and national legislation which can be interpreted as requiring landscape planning at all forest ages to meet biodiversity and other environmental goals. However, it is still rare that planning for conservation is done other than at the final felling stage. Implementing this new strategy is likely to have long-term positive effects and improve the protection of surface waters from negative forestry effects and a history of fire suppression. By following these suggested management principles, there will be a longer time period with high function and greater future management flexibility in addition to the benefits provided by leaving riparian buffers at the final felling stage.

Many stream restoration projects aim to increase geomorphic complexity, assuming that this increases habitat heterogeneity and, thus, biodiversity. However, empirical data supporting these linkages remain scant. Previous assessments of stream restoration suffer from incomplete quantification of habitat complexity, or a narrow focus on only one organism group and/or one restoration measure, limiting learning. Based on a comprehensive quantification of geomorphic complexity in 20 stream reaches in northern Sweden, ranging from streams channelized for timber floating to restored and reference reaches, we investigated responses of macroinvertebrates, diatoms, and macrophytes to multiple geomorphic metrics. Sediment size heterogeneity, which was generally improved in restored sites, favored macroinvertebrate and diatom diversity and macroinvertebrate abundance. In contrast, macrophyte diversity responded to increased variation along the longitudinal stream profile (e.g., step-pools), which was not consistently improved by the restoration. Our analyses highlight the value of learning across multiple restoration projects, both in identifying which aspects of restoration have succeeded, and pinpointing other measures that might be targeted during adaptive management or future restoration. Given our results, a combination of restoration measures targeting not only sediment size heterogeneity, but also features such as step-pools and instream wood, is most likely to benefit benthic biota in streams.

Swedish boreal streams were modified to transport timber by pushing boulders to stream sides, creating levees that disconnected streams from riparian areas. Many streams have since been restored and our goal was to understand how this affects riparian nitrogen (N) cycling. We compared the natural abundance of delta N-15 isotopes in foliage and roots of Filipendula ulmaria plus soils and litter along streams restored 2-25 years ago. We measured sources of N, potential immobilization of N, namely plant diversity and biomass, and the amount and sources of carbon (C) to determine if these were important for describing riparian N cycling. The delta N-15 of F. ulmaria foliage changed dramatically just after restoration compared to the channelized, disconnected state and then converged over the next 25 years with the steady-state reference. The disturbance and reconnection of the stream with the riparian zone during restoration created a short-term pulse of N availability and gaseous losses of N as a result of enhanced microbial processing of N. With increasing time since restoration, N availability appears to have decreased, and N sources changed to those derived from mycorrhizae, amino acids, or the humus layer, or there was enhanced N-use efficiency by older, more diverse plant communities.

Why evaluations of the ecological outcomes of stream and river restoration have largely reported inconclusive or negative results has been the subject of much debate over the last decade or more. Understanding the reasons behind the lack of positive results is important for bettering future restoration efforts and setting realistic expectations for restoration outcomes. This thesis explores possible explanations for why researchers have failed to find clear and predictable biotic responses to stream restoration: recovery time has been too short, that restoration of habitat complexity is not clearly linked to instream biodiversity, that one monitored organism group is not representative of the entire community, that restoration effort was not intense enough to restore the potential habitat complexity of a system, and that reach-scale restoration done in the presence of catchment-scale degradation obscures restoration results. The overarching goal of this thesis is to study the holistic effect of reach-scale restoration of historic reach-scale simplification, due to timber floating in northern Swedish streams, thus avoiding the added pressure of catchment-scale degradation typically found at most restoration sites (e.g., non-point-source pollution and impervious cover). Using this model system, I was able to show that it took 25 years for riparian plant species richness at restored sites to increase above that of channelized sites. Furthermore, it was clear that restoration of these streams caused a large and rapid change in N-processing in the riparian zone and this alteration persists for at least 25 years. Additionally, multiple metrics of geomorphic complexity were needed to explain some of the more subtle responses of organism groups. Macroinvertebrates, diatoms, and macrophytes did not respond concordantly and cannot serve as surrogates or indicators for each other. I found that older best practice methods of restoration rarely restored the large-scale features needed to bring the sites up to their potential complexity because these elements were destroyed or removed from the system. Advanced restoration techniques used in more recent restorations added big boulders and instream wood and increased complexity to a level that elicited a biological response. By combining surveys of multiple metrics of structure, diversity of multiple organism groups, and process in this thesis I was able to get a holistic view of the effects of restoration of streams after timber floating. We now know that it takes at least 25 years for riparian plants and N-cycling to recover, we understand that multiple metrics of geomorphic complexity should be measured to be able to explain biotic responses, and that restored complexity should better match the potential complexity of the site in order to elicit a biological response. Finally, we know that multiple organism groups need to be assessed when evaluating the response of biodiversity to restoration.

We reviewed follow-up studies from Finnish and Swedish streams that have been restored after timber floating to assess the abiotic and biotic responses to restoration. More specifically, from a review of 18 case studies (16 published and 2 unpublished), we determined whether different taxonomic groups react differently or require different periods of time to respond to the same type of restoration. Restoration entailed returning coarse sediment (cobbles and boulders) and sometimes large wood to previously channelized turbulent reaches, primarily with the objective of meeting habitat requirements of naturally reproducing salmonid fish. The restored streams showed a consistent increase in channel complexity and retention capacity, but the biotic responses were weak or absent in most species groups. Aquatic mosses growing on boulders were drastically reduced shortly after restoration, but in most studies, they recovered after a few years. Riparian plants, macroinvertebrates and fish did not show any consistent trends in response. We discuss seven alternative explanations to these inconsistent results and conclude that two decades is probably too short a time for most organisms to recover. We recommend long-term monitoring using standardized methods, a landscape-scale perspective and a wider range of organisms to improve the basis for judging to what extent restoration in boreal streams has achieved its goal of reducing the impacts from timber floating.

A lack of ecological responses in stream restoration projects has been prevalent throughout recent literature with many studies reporting insufficient time for recovery. We assessed the relative importance of time, site variables, and landscape setting for understanding how plant species richness and understory productivity recover over time in riparian zones of northern Swedish streams. We used a space-for-time substitution consisting of 13 stream reaches restored 5-25 years ago, as well as five unrestored channelized reference reaches. We inventoried the riparian zone for all vascular plant species along 60-m study reaches and quantified cover and biomass in plots. We found that while species richness increased with time, understory biomass decreased. Forbs made up the majority of the species added, while the biomass of graminoids decreased the most over time, suggesting that the reduced dominance of graminoids favored less productive forbs. Species richness and density patterns could be attributed to dispersal limitation, with anemochorous species being more associated with time after restoration than hydrochorous, zoochorous, or vegetatively reproducing species. Using multiple linear regression, we found that time along with riparian slope and riparian buffer width (e.g., distance to logging activities) explained the most variability in species richness, but that variability in total understory biomass was explained primarily by time. The plant community composition of restored reaches differed from that of channelized references, but the difference did not increase over time. Rather, different time categories had different successional trajectories that seemed to converge on a unique climax community for that time period. Given our results, timelines for achieving species richness objectives should be extended to 25 years or longer if recovery is defined as a saturation of the accumulation of species over time. Other recommendations include making riparian slopes as gentle as possible given the landscape context and expanding riparian buffer width for restoration to have as much impact as possible.

Relating restoration ecology to policy is one of the aims of the Society for Ecological Restoration and its journal Restoration Ecology. As an interdisciplinary team of researchers in both ecological science and political science, we have struggled with how policy-relevant language is and could be deployed in restoration ecology. Using language in scientific publications that resonates with overarching policy questions may facilitate linkages between researcher investigations and decision-makers' concerns on all levels. Climate change is the most important environmental problem of our time and to provide policymakers with new relevant knowledge on this problem is of outmost importance. To determine whether or not policy-specific language was being included in restoration ecology science, we surveyed the field of restoration ecology from 2008 to 2010, identifying 1,029 articles, which we further examined for the inclusion of climate change as a key element of the research. We found that of the 58 articles with climate change or global warming in the abstract, only 3 identified specific policies relevant to the research results. We believe that restoration ecologists are failing to include themselves in policy formation and implementation of issues such as climate change within journals focused on restoration ecology. We suggest that more explicit reference to policies and terminology recognizable to policymakers might enhance the impact of restoration ecology on decision-making processes.

Stream restoration usually relies on ecological theories presuming that increased habitat heterogeneity leads to higher biodiversity. However, to test this hypothesis a quantitative metric of overall geomorphic complexity is needed. We quantified geomorphic complexity using 29 metrics over five dimensions (sediment distribution, longitudinal profile, cross section, planform, and instream wood) of headwater streams in northern Sweden. We examined reaches with four different restoration statuses after a century of timber floating (channelized, restored, demonstration restored, and unimpacted) to determine (1) whether restoration increases complexity in all dimensions, (2) whether a complexity gradient can be quantified and which metrics can serve as proxies for the gradient, and (3) levels of potential complexity based on large-scale controls (drainage area, glacial legacy sediment, valley slope, valley confinement old-growth forest/buffer zone, and beaver activity). We found a significantly higher complexity in unimpacted and demonstration restoration sites than in channelized sites in all five dimensions except the cross section (based on the two metrics quantifying variability in the cross section). Multivariate analyses were able to elucidate an apparent complexity gradient driven by three complexity metrics: longitudinal roughness, sediment sorting, and cross section chain and tape ratio. The large-scale factors of valley and channel gradient as well as median grain size, along with restoration status, drive differences in complexity composition. Restoring a reach to its potential complexity is beneficial in regions without reference systems or sufficient data to model flow and sediment processes. Unimpacted and demonstration restoration reaches displayed not only more intrareach variability than channelized reaches but also greater interreach heterogeneity in complexity composition, which supports a focus on reach-scale controls on potential complexity and a landscape-scale view on restoration. (C) 2014 Elsevier B.V. All rights reserved.

Invasive non-native plants pose a ubiquitous threat to native plant communities and have been blamed for the decline of many endangered species. Endangered species legislation provides legal instruments for protection, but identifying a general method for protecting endangered species by managing non-natives is confounded by multiple factors. We compared non-native management methods aimed at increasing populations of an endangered forb, Ambrosia pumila, and associated native plants. We compared the effects of a grass-specific herbicide (Fusilade II), hand-pulling, and mowing in two degraded coastal sage scrub sites in southern California, U.S.A. At both sites, hand-pulling had the greatest effect on non-native cover, and correspondingly resulted in the greatest increase in A. pumila stems. Fusilade II application also led to an increase in A. pumila, but was not as effective in controlling non-native plants as hand-pulling and its effect varied with the dominant non-native species. Mowing was not effective at promoting A. pumila, and its effect on non-native cover seemed to be related to rainfall patterns. Although some methods increased A. pumila, none of our treatments simultaneously increased cover of other native plants. Hand-pulling, the most effective treatment, is labor intensive and thus only feasible at small spatial scales. At larger scales, managers should take an experimental approach to identifying the most appropriate method because this can vary depending on the specific management objective (endangered species or whole native community), the dominant non-natives, yearly variation in weather, and the timing of treatment application.