Process domain study
Process domain study in two sub-catchments of the Vindel River: data about geology and channel slope with the influence of the former highest coastline of Sweden for streams in the Hjuksån and Bjurbäcken sub-catchment.
Process domains are spatially distinct areas along streams with characteristic geomorphological history and processes. Using the process domain concept (PDC), the spatial variability of geomorphic processes can be described. These processes govern temporal patterns of disturbances, which affects the morphology of a river system and the formation of the physical habitat to which organisms adapt. In this way, geomorphic processes form the base for the biodiversity and functioning of the river ecosystem, and the PDC can be useful for the management of river systems. In northern Sweden, it is expected that channel slope, types of glacial landforms, including the former highest coastline (based on post-glacial rebound) and the type of sediments present play an important role in structuring the ecosystem.
In my project, I will apply the PDC in two sub-catchments of the Vindel river catchment: Hjuksån (below the former highest coastline) and Bjurbäcken (above the former highest coastline). I have assembled data about geology (surficial and glacial sediments) and elevation (DEM). With the DEM, it is possible to calculate the channel slope of streams. Based on a classification for channel slope and sediment type, I identified 9 process domains (see table below). Although ecological data is not studied, the data about process domains, geology and channel slope can provide, together with data about the effects of colonist pools, an integrated and catchment-scale view of geomorphic and ecological processes in order to improve the restoration of streams in northern Sweden.
Figure: The Vindel River (blue line) with its catchment (orange) and the two sub-catchments of the tributaries Hjuksån and Bjurbäcken with their locations related to the former highest coastline (red line). Rectangle on inset map shows the location of the detailed map.
Table: proposed process domains (A-I) tributaries to the Vindel River, based on channel slope and sediment type.
Species’ river journeys
Understanding species’ journeys through rivers
My aim is to better understand factors and processes shaping rivers. Current knowledge varies a lot depending on the perspective researchers take. Characteristics of local plant and animals communities within river sections of up to a few 100 meters are already well understood. River scientists are able to identify and explain important details of abiotic and biotic components for these segments. Naturally, most rivers do not flow for only a few meters but last several kilometers before draining into the ocean. Trying to understand how different influences add up and interact on this long journey is a challenge not many scientists have taken up yet. I want to change this by studying how species spread throughout the entire length of rivers.
I am specifically interested in how plants end up in the riparian zone (=next to a river) at a certain part of a river, where they come from and the dispersal pathways their seeds take. This can be done by comparing plant communities from different locations along the river with each other. Assessing where common species are found allows us to understand how and where seeds have spread. For the portion of seeds with hydrochoric dispersion, which is the transport via water, the presence of lakes, meandering parts of a river, rapid flowing sections, and other physical characteristics can influence the final destination of the seeds. Therefore, I will analyze biotic features and also integrate abiotic factors in my research.
The findings of my research will improve the basic understanding of rivers and can also be used to design and optimize concepts for river restoration and management, which can only be as successful as the scientific knowledge which they are based on.
Riparian vegetation recovery
Where do plant seeds come from after stream restoration?
Since the 1980s, stream restoration of boreal rivers in northern Sweden after over a century of timber-floating has occurred in distinct waves. After restoration, bare soil or exposed rocks were common in many riparian areas. In many places, timber-floating may have led to a reduction or even extinction of species in the channelized reaches. Plants need to establish in these areas by spreading their seeds from adjacent areas, namely upstream and upland colonist sources. The relative contribution of these sources will affect the recovery process of the plants living along the restored streams in what is called the riparian zone. From a larger-scale point of view, dispersal by water flow from upstream colonist sources and dispersal by wind, surface run-off or animals from upland sources to a particular habitat are essentially determined by the physical characteristics of a stream and the landscape, known as geomorphic characteristics. This means that the geomorphic characteristics of the upstream and upland areas will affect the relative contribution of them as colonist sources for the recovery of the restored sites.
The objective of this project is to clarify the effects of geomorphology on the relative contribution of adjacent plant colonist sources for the recovery of riparian vegetation after restoration. Twenty sites representing two types of restoration (basic and enhanced restoration) in tributaries of the Vindel River in northern Sweden will be investigated. All plant species in the riparian zone of the restored sites, upstream riparian zone and upland areas will be recorded. Geomorphic parameters will be measured and stream types will be identified using remote mapping (GIS) techniques along the entire upstream segment. Hillslope geometry of the upland area, presence of lakes and the distance of lakes from the restored area will also be measured.
Aquatic macroinvertebrate recovery
Responses of aquatic macroinvertebrates to stream restoration
Aquatic macroinvertebrates include many species of insects, worms, molluscs and crustaceans that live in waterbodies. Each of those species has specific requirements and tolerance levels regarding water quality, type of substrate, water temperature and flow velocity. They feed on the large variety of organic material in the river channel, such as leaves, detritus, biofilm and algae and are themselves prey for fish. These characteristics make macroinvertebrates key elements of the aquatic food web and excellent bioindicators of the health of the ecosystem.
Stream channelization creates homogenous environments, which causes a loss in biodiversity. Restoration projects aim to reverse this process, and thus to enhance biodiversity by increasing the heterogeneity of stream habitats. However, many projects fails to reach this goal. The aim of my project is to identify the factors that underpin the recovery of macroinvertebrates after stream restoration. For this, I am studying a set of forest streams in northern Sweden that were restored during the past few decades after being channelized for timber floating. The results of this study will allow for a better understanding of the linkages between habitat heterogeneity and biodiversity and for making recommendations for more effective planning of future stream restoration projects.
Sampling for macroinvertebrates
Survey of aquatic microhabitats
Field work at a channelized stream
Geomorphic complexity and sediment
Geomorphic complexity and ecological processes and interactions in stream restoration
I am interested in understanding the natural form and processes of streams, which can be used to restore degraded streams to a more ‘natural’, self-sustaining form. The regional focus of most of my recent research is northern Sweden, where most streams, large and small, were severely altered to facilitate timber floating and are now undergoing different types of restoration to increase habitat quality and quantity.
There are several aspects of natural stream processes that my research focuses on. First, geomorphologists know a lot about how alluvial streams form and change, which are those that are self-formed in sediment (sand, gravel, boulders) that has been transported and deposited by the stream itself. But in northern Sweden most streams are semi-alluvial, meaning that some of the sediment that makes up the stream’s bed and banks came from somewhere else than the stream itself, namely glacial deposits of coarse cobbles and boulders. Therefore, the classical equations and processes used to predict channel form do not apply in northern Sweden. In the MorphoRest project, I am analyzing how sediment moves and how we can predict natural channel form in semi-alluvial streams. Second, I am interested in how complexity of streams can be quantified and how this impacts ecological characteristics and processes— how is overall geomorphic complexity best quantified? Does geomorphic complexity automatically translate into increased biodiversity of instream organisms or riparian vegetation, or possibly higher quality of ecosystem processes?
Finally, in the BioRest project, which I am co-leading together with Christer Nilsson, we are taking a look at how larger landscape-scale processes and features impact the biotic recovery of restored site. Streams are unique in the landscape in that they are not separate, discrete features, but they connect the entire landscape from the mountains to the sea. Water, sediment, animals, and seeds move downstream (and animals such as fish even move upstream) at different speeds and are caught or deposited in different sections of the stream system, which influences how a specific section of a stream looks like, in terms of the ecology and geomorphology. In northern Sweden, we have different types of stream segments that alternate throughout the stream system, including turbulent rapids with coarse sediment, slow-flowing meandering sections, and lakes. In the BioRest project, we are working to figure out how restored stream sections recover based on how the stream section fits into the larger landscape and stream system.
Most of my past research has focused on the connection between physical processes in streams (how water flows and sediment shape how the stream looks like) and ecological characteristics and processes. For example, in Colorado, USA, I have examined the role of geomorphology in determining the width of the riparian zone, and the role of beaver and plants in forming how the stream behaves and looks like. I believe that in order to best manage the amazing natural resource that streams are we need to understand how streams work from both a geomorphic and ecological point of view, as well as interactions between them.
Surveying the channel with a total station to quantify complexity
A restored stream in northern Sweden with coarse boulders, instream wood, and opened side channels
A restored stream in northern Sweden with coarse boulders
Stream restoration and vegetation
I am fascinated by flowing waters and their riparian zones. My research areas revolve around effects of climate change on hydrology and wetland vegetation – especially in arctic and subarctic regions, environmental effects of ecological restoration – not least the importance of location and scale, and impacts of hydrological changes on biological diversity. I was trained as a plant ecologist but now publish also on fish, mammals, birds and invertebrates. A common feature of my research is that I like to look at nature from a large-scale – in many cases global – perspective, and try to understand how different parts of landscapes are connected ecologically.
I have a passion for writing which is manifested in many publications and in that I serve the journals BioScience, Ecological Applications; Journal of Ecology; Ecosystems; Ecology & Society; and Perspectives in Plant Ecology, Evolution and Systematics as an associate editor.
When it comes to specific projects, I am currently leading the BioRest project together with Lina Polvi Sjöberg. I am especially interested in unravelling the factors limiting ecological recovery and quantifying how the potential for ecosystem recovery varies within catchments. I am also involved in a Nordic collaboration (Ermond) where we look for examples of how ecological restoration has been used as a means for mitigating natural hazards. In a sub-project I am specifically studying ecological restoration vs. severe flooding in rivers. In an Australian project we try to find ways to reduce erosion in rivers and streams. In yet another collaborative project (RiPeak) we study the relationships between plant traits and hydrological factors.
Erosive creek near Brisbane, Australia.
People are warned about getting too close to the creek, especially during floods.
Flooding is a natural phenomenon and is vitalizing the river ecosystem. Heavy impact in the catchment, however, can cause severe floods because of reduced retention capacity. Ecological restoration in the catchment can be a means for increasing retention capacity and reducing risks for large floods.
The regulated water-level regimes caused by the management of hydropower stations (hydropeaking) are challenging for many plants.