Northern peatlands are an important carbon store, with carbon dynamics and hydrology intrinsically linked. The riparian zone is the interface between the terrestrial and aquatic systems, situated adjacent to the stream and characterised by periodic flooding, near surface water tables and unique soil and plant species composition. Due to its unique biogeochemical environment, the riparian zone has the potential to modify significantly the production, mobilisation and transport of carbon via the land-atmosphere and aquatic pathways. Two contrasting headwater catchments, an ombrotrophic peatland (Auchencorth Moss, SE Scotland) and a forested, till dominated catchment (Västrabäcken, N Sweden), were investigated. In each carbon concentrations in soil and stream water and hydrological parameters were measured in transects connecting the wider catchment, riparian zone and stream. The overarching aim was to investigate the role of the riparian zone on the hydrological and bio-geochemical functioning of peatland and forested catchments, focusing on carbon export via the aquatic pathway. Specific objectives were to: a) examine the importance of soils, water table and vegetation composition on riparian biogeochemical cycling, b) investigate riparian-stream hydrological connectivity and the transport of carbon across the soil-water interface and c) assess riparian processes in relation to the net ecosystem carbon balance (NECB) across northern latitude ecosystems. Porewater total carbon (TC) concentrations (sum of dissolved organic and inorganic carbon (DOC, DIC), CO2 and CH4) were on average higher in Auchencorth Moss (78.8-140 mg C L-1) than the Västrabäcken (27.7-63.2 mg C L-1) catchment. In both catchments, higher TC concentrations were observed in the riparian zone compared to the wider catchment. The dominant control for differentiating between catchment and riparian biogeochemical processes was the higher average riparian water table with each carbon species displaying a positive relationship with water table height. A range of other factors, including soil temperature and the carbon content of catchment and riparian soils, also contributed to the complexity of riparian carbon biogeochemical cycles. Catchment specific phenomena, including the presence of aerenchymous vegetation and stream sediment deposition onto the riparian zone, modified riparian carbon dynamics in the Auchencorth Moss catchment. Isotopically, porewater DOC, CO2 and CH4 had a 14C content >100 %modern, indicating that the modern plant derived DOC is being transported down the soil profile, providing the source for CO2 and CH4 production at depth. In both catchments the riparian zone represented an important and dynamic source of carbon to stream waters. Total annual CO2 export from the riparian zone of the Västrabäcken catchment to the stream channel over the hydrological year was 2.7 g CO2-C m2 yr-1 with export predominantly from between 40 and 55 cm depth within the soil. Two monthly peaks in CO2 export occurred over the hydrological year related to either storm events or the spring snow melt period which accounted for 19 % of annual export, highlighting the temporal variability in soil-stream linkages, especially during high flow periods. In the generally wetter peatland catchment, riparian-stream linkages were driven by antecedent conditions and variation in riparian water table, with changes in water input, rather than changes in CO2 source concentrations, controlling stream water composition. The negative CO2 concentration-discharge relationship in the stream suggested that event water dominated, with small but important inputs from high concentration soil water during individual events. The importance of event water in transporting carbon was confirmed through the isotope result. CO2, CH4 and DOC exported via the aquatic pathway predominantly contained modern, plant derived carbon from the near surface soil horizons but with a small contribution (5-28 %) from deeper geological sources leading to aged evasion CH4 (310-537 years BP) and CO2 (36 years BP to modern). In both catchments the riparian zone was more important, relative to the wider catchment, in controlling the export of carbon via the aquatic pathway. At Auchencorth Moss, the riparian zone, plus an area of the catchment extending ~20 m from the stream, were hotspots for land-atmosphere fluxes of CH4, with mean flux of 1.08-7.70 mg m2 hr-1 in comparison to the catchment overall (0.05 mg m2 hr-1). In both catchments, combining detailed catchment hydrological models with high temporal resolution carbon concentration measurements, especially in riparian zone soils, has the potential to improve estimates of downstream and evaded carbon export in headwater catchments. Riparian zones should therefore be included more in studies investigating hydrological and biogeochemical processes in northern latitude headwater catchments. The processes within riparian zones suggest that despite the relatively small area that riparian zones represent, in relation to the wider catchment, they may play an important role in the NECB of peatland and forested catchments under future management and climate change scenarios.

Swedish forests are mostly used for timber harvesting and 96 % of this harvesting is made by clear cutting while only 4 % is effected through other methods such as single tree harvesting. All species are not affected by forestry to same magnitude. Some specifically generalists are not affected at all. Hence, this study, had its aim to find out vascular plant species that persist, disappear or colonize other species as a result of anthropogenic disturbances in different production forests, so as to determine not only if canopy openness affects the species distribution but also the magnitude of the effects. I examined 10 different forest localities during May and June 2008. Three of these localities were made up of clear cut forest plots, 3 with partially cut down forest plots and 4 with undisturbed production forest plots. Species composition and diversity were then compared between these plots. A total of 34 different species were found. Statistical Analysis was made on how well the species in the partially cut down forest plots fitted into the undisturbed forest group as well as comparing this results with results of how counterpart species in the clear cut forest plots fitted into the undisturbed forest groups. These results showed that there was no significant difference, ANOVA values of P = 0.839, 0.602 and 0.564 respectively among the species composition between the forest, partially cut down and clear cut forest groups between the forest, partially cut down and clear cut forest plots. However, among the 54 species found in all study plots, 11 were common between the forest and partially logged sites whereas only Carex sp in the clear cut forest was common to those in the forest plots implying that canopy openness did not affect the total species number but had an effect in species composition. Clear cutting seems to kill off everything but trees and generalists. Hence, resiliency of vegetation should be increased by management practices that ensure the maintenance of prior species.

The global carbon cycle is intimately linked with the earth’s climate system. Knowledge about carbon cycling in the biosphere is therefore crucial for predictions of climate change. This thesis investigates the carbon dioxide balance of Swedish boreal lakes, its regulation, significance to the carbon budget of the boreal landscape, and sensitivity to climate change. Swedish boreal lakes were almost exclusively supersaturated in CO2 with respect to the atmosphere, resulting in an emission of CO2 from lakes to the atmosphere. Lake pCO2 was closely related to the concentration of terrigenous dissolved organic carbon (DOC), indicating that the utilization of terrigenous DOC by lake bacteria is a major source of CO2. This conclusion is supported by independent field studies, showing that net plankton respiration accounts for most of the CO2 emitted from Swedish boreal lakes, while photochemical mineralization and sediment respiration were less important. Mineralization of terrigenous DOC and subsequent emission of CO2 from lakes to the atmosphere was a major carbon loss factor in 21 major Swedish boreal catchments, removing 30-80% of the organic carbon exported from terrestrial soils to surface waters. Lake CO2 emission is in the same order of magnitude as organic carbon accumulation in boreal forest soils, and should therefore be included in the carbon budget of the boreal landscape. In a set of nearly 5000 global lakes, DOC concentration was a much more important regulator of lake pCO2 than temperature. Climate change will therefore affect the carbon balance of lakes primarily via alterations in terrestrial DOC export, rather than via changes in temperature per se. Both current observations and models of future climate suggest an increasing export of terrigenous DOC from many Scandinavian catchments. Hence, there probably is a current trend towards higher CO2 emission from Swedish boreal lakes, which is likely to continue in the future.

Den här avhandlingen belyser hur avverkning och markberedning påverkar markfloran i den svenska barrskogen. Dessutom utvärderas två inventeringsmetoder som används inom växtekologin. Vid arbetet har både rikstäckande inventeringsdata och fältförsök använts och de likartade resultaten tyder på att rikstäckande inventeringar är en underutnyttjad resurs i forskningen. Ju större andel av träden som avverkas desto större blir förändringen av markflorans sammansättning. Vissa arter, som lingon, ljung, etc., verkar dock inte påverkas i nämnvärd omfattning, medan andra, som blåbär, minskar i relation till hur mycket som avverkats. Gräs och mjölkört ökar efter avverkning, dock visar sig vissa gräs och mjölkört inte reagera om inte avverkningen överskrider ett tröskelvärde på ca 80 %. Avverkning har en liten, men signifikant, effekt på antalet arter, medan artomsättning, d.v.s. arters etablering på och/eller försvinnande från provytorna, framförallt påverkas av andel gran innan avverkning, markens produktionsförmåga och först därefter av hur stor andel av träden som avverkas. Det var också uppenbart att markberedning har en stark effekt som skiljer sig från avverkning. Framförallt gynnas björnmossor av markberedning men även vårfryle, kruståtel och mjölkört. Arter som missgynnas av markberedning var bl.a., en levermossa, lingon, väggmossa och kråkbär. I växtekologi är visuell täckningsbedömning, d.v.s. hur stor del av en provyta som täcks av en växtart, och registrering av förekomst/icke förekomst, d.v.s. finns en växtart på en provyta eller inte, de två vanligaste metoderna vid vegetationsinventering. Vid registrering av förekomst/icke förekomst missas upp till en tredjedel av förekomsterna, vanligaste orsaken till missade registreringar verkar vara att man inte upptäcker arten snarare än att den inte kan identifieras. Det var stora variationer mellan arter, där arter med få exemplar på provytan missas oftare. Både den visuella täckningsbedömningen och förekomst/icke förekomst visar sig ha personberoende fel, d.v.s. att olika personer genomgående ger högre eller lägre värden än andra. Trots det personberoende felet visar sig täckningsbedömningar ha ett större informationsvärde än registrering av förekomst/icke förekomst när det gäller att särskilja olika typer av vegetation. Erfarenhet har en förvånansvärt liten effekt på kvaliteten av täckningsbedömningar. / This thesis has two main focuses; first, the response of forest ground layer flora on forestry, mainly harvesting and secondly, the quality of the vegetation assessment methods, cover estimates by eye and presence/absence data. The effect of harvesting intensity was evaluated with survey data from permanent plots as well as vegetation data from a field trial fourteen years after harvesting. Both data sets confirmed that response of ground layer flora increased with increasing logging intensity. Thereby, indicating that survey data is possible to use in research. From the survey data set, existence of a time lag was evident for several species and also a threshold level was evident in cutting intensity needed to affect a number of species. Logging had a modest, but significant positive effect on the change in species number per plot. Species turnover was influenced by the proportion of Picea abies in the tree canopy; site productivity; and logging intensity. In the field trial scarification had a strong effect that was different from the one created by cutting. In plant ecology cover estimate by eye and presence/absence recording are the two most frequent methods used. The methods were evaluated with survey data and a field trial. In the first data set vegetation was recorded independently by two observers in 342 permanent 100-m2 plots. Overall, one third of each occurrence was missed by one of the two observers, but with large differences among species. Species occurring at low abundance tended to be frequently overlooked. Observer-explained variance in cover estimates was <10% in 15 of 17 species. In the second data set, 10 observers independently estimated cover in sixteen 100-m2 plots in two different vegetation types. The bias connected to observer varied substantially between species. The estimates of missing field and bottom layer had the highest bias, indicating that missing layers are problematic to use in analysis of change. Experience had a surprisingly small impact on the bias connected to observer. Analyses revealed that for the statistical power, cover estimates by eye carries a higher information value than do presence/absence data when distinguishing between vegetation types, differences between observers is negligible, and using more than one observer had little effect.

Carbon (C) pools and fluxes in northern hemisphere forest ecosystems are attracting increasing attention concerning predicted climate change. This thesis studied C fluxes, particularly soil C dynamics, in spruce forest ecosystems in relation to interactions between physical/biological processes using a process-based ecosystem model (CoupModel) with data for Swedish conditions. The model successfully described general patterns of C and N dynamics in managed spruce forest ecosystems with both tree and field layers. Using regional soil and plant data, the change in current soil C pools was -3 g C m-2 yr-1 in northern Sweden and +24 g C m-2 yr-1 in southern Sweden. Simulated climate change scenarios resulted in increased inflows of 16-38 g C m-2 yr-1 to forest ecosystems throughout Sweden, with the highest increase in the south and the lowest in the north. Along a north-south transect, this increased C sequestration mainly related to increased tree growth, as there were only minor decreases in soil C pools. Measurements at one northern site during 2001-2002 indicated large soil C losses (-96 g C m-2 yr-1), which the model successfully described. However, the discrepancy between these large losses and substantially smaller losses obtained in regional simulations was not explained. A simulation based on Bayesian calibration successfully reproduced measured C, water and energy fluxes, with estimated uncertainties for major components of the simulated C budget. Site-specific measurements indicated a large contribution from field layer fine roots to total litter production, particularly in northern Sweden. Mean annual tree litter production was 66% higher at the most southerly site (240 g C m-2 yr-1 compared with 145 g C m-2 yr-1 in the north), but when field and bottom layers were included the difference decreased to 16% (total litter production 276 g C m-2 yr-1 and 239 g C m-2 yr-1 respectively). Regional simulations showed that decomposition rate for the stable soil C fraction was three times higher in northern regions compared with southern, providing a possible explanation why soil C pools in southern Sweden are roughly twice as large as those in the north. / QC 20100922

Two small bordering catchments in Bispgården, Central Sweden, wereinvestigated in regard to soil solution and stream water chemistry during the frostfree seasons of 2003-2007. Both catchments were drained by first order streams,Fanbergsbäcken and Gråbergsbäcken, and in Fanbergsbäckens catchment anextensive investigation of the soil and soil solution chemistry was conducted bylysimeter and centrifugation sampling. The area of intensive soil solutioninvestigation was situated in a slope towards a stream incorporating a rechargearea, with podzolic soil, and a discharge area close to the stream with an arenosolsoil. Samples were continuously taken in both the recharge- and the discharge areaof the slope, and stream water was sampled in the streams of both catchments. Themain variables of interest of the study were the interactions, the influence ofdissolved organic carbon and the effects of wood ash application to soil solutionand stream water.The natural variations and the interactions between soil solution and streamwater were monitored during 2003-2004. In soil solution, most of the investigatedsubstances tended to increase during the growing season, due to weathering andmicrobial degradation of biota. Ca, Mg, Al and Fe were highly associated todissolved organic carbon (DOC) throughout the catchment. The low molecularfraction of DOC seemed to have a higher impact on the soil processes in therecharge area, while high molecular DOC was more important for transport ofcations in the discharge area and the stream water.The concentration of different substances in the two streams differedsignificantly, even though the catchments were similar in size, shape andforestation. The seasonal patterns of most of the substances measured weresignificantly correlated between the streams, however. Cations and pH correlatedwell with DOC and flow. The flow pattern driven by precipitation seems to be thedriver of the stream water chemistry.Wood ash was applied at a dosage of 3 ton/ha to one of the catchments in theautumn of 2004, to investigate the initial effects on the soil solution- and streamwater chemistry. WAA is recommended by the Swedish Forest Agency tocounteract acidification in soil and runoff that may be caused by an intensivebiomass harvesting. The impact of the WAA was studied during 2005-2006.Compared to the control temporarily higher concentrations of K, Ca and SO4 wereobserved in the soil solution of the ashed area. In the stream water the effects of theWAA were easier to distinguish due to higher sampling frequency. The strongesteffect was seen for K, but increases in the stream water were also noted for DOC,Ca, Mg, Si, Cl and malonate. No increase in pH could be statistically verifiedhowever, and overall the initial effects of the WAA seem mild. / Två angränsande avrinningsområden i Bispgården i centrala Sverigeundersöktes under den snöfria säsongen 2003-2006. Båda avrinningsområdenadränerades av första ordningens bäckar och i det ena, Fanbergsbäckensavrinningsområde, gjordes en omfattande undersökning av mark och markvattenkemin.Markvatten provtogs genom centrifugering och med lysimetrar.Provtagningen gjordes i inströmningsområdet där jordmånen var en typiskpodzol samt närmare bäcken, i utströmningsområdet, där jordmånen var enarenosol. Bäckvatten provtogs i båda avrinningsområdena. Interaktioner mellanmark, markvatten och bäckvatten undersöktes med särskilt fokus på inverkan avorganiskt kol samt påverkan av askåterföring.De naturliga variationerna i markkemin samt interaktionerna mellan mark- ochbäck vatten undersöktes 2003-2004. I markvatten ökade merparten av de studeradeämnena under provtagningssäsongen beroende av ökad vittring och recirkulationav biota och fallförna. Ca, Al och Fe var i stor utsträckning associerade till löstorganiskt kol (DOC). Den lågmolekylära fraktionen av DOC hade en störreinverkan på markprocesserna i inströmningsområdet, medan den högmolekyläradelen var viktigare för transport av katjoner i utströmningsområdet samt ibäckvattnet.Koncentrationsnivåerna av olika substanser i bäckarna uppvisade skillnadertrots avrinningsområdenas yttre likheter med avseende på storlek, form ochbeskogning. Trots de kvantitativa skillnaderna erhölls emellertid liknandesäsongsvariationer i koncentrationerna, vilket indikerade att kemin i huvudsakstyrdes av mängden DOC som i sin tur berodde av avrinningen som drevs avnederbörden. Höga halter av Ca, Mg, Al och Fe återfanns associerade tillhögmolekylärt DOC i bäckvattnet i en utsträckning som inte rapporterats tidigare.På hösten 2004 spreds 3 ton aska/ha till Fanbergsbäckens avrinningsområde föratt undersöka de initiala effekterna på mark- och bäckvatten kemin. Askåterföringbör ske minst en gång per omloppstid vid helträdsavverkning, i enlighet medSkogsstyrelsens rekommendationer, främst för att motverka försurning i mark ochavrinnande vatten som antas uppstå vid intensivt uttag av biomassa. De initialaeffekterna av askåterföringen på mark- och bäckvattnets kemi studerades under2005-2006 och Gråbergsbäcken kunde användas som obehandlad kontroll vidundersökning av vattenkemin i Fanbergsbäcken. I undersökningen av markvattenviåterfanns stora säsongsvariationer, vilket gjorde det svårt att urskilja eventuellaeffekter av askåterföringen. Tillfälligt högre värden av K, Ca och SO4 återfannsdock i det askade området i jämförelse med kontrollområdet. På grund av högreprovtagningsfrekvens i bäckvattnet var det lättare att påvisa förändringar ibäckvatten kemin. Framförallt märktes en signifikant ökning av K jämfört medkontrollbäcken. Sådana ökningar, om än inte lika markanta återfanns också förDOC, Ca, Mg, Si, Cl och malonat. En tendens till ökat pH kunde observeras, mendenna kunde inte verifieras statistiskt. De initiala effekterna av askåterföringen varsåledes till synes milda, och den eftertraktade pH-effekten erhölls ej i dennaundersökning.

How much groundwater flows to boreal streams depends on the relative contributions from each landscape unit (forested uplands, lakes, and peatlands) within a catchment along with its hydrogeologic setting. Although there is an understanding of the hydrologic processes that regulate groundwater outputs from individual landscape units to their underlying aquifers (both coarse- and fine-textured) in the boreal forest, less understood is how the topography, typology, and topology (i.e. hydrologic connectivity) of the landscape units regulates groundwater flow to streams. Improved understanding of groundwater-stream interactions in the Boreal Plain of Alberta and Saskatchewan is critical as this region is undergoing substantial environmental change from land cover disturbances for energy and forestry industries and climate change. This thesis determines groundwater-stream interactions during the autumn low-flow period in a 97 km2 glacial outwash sub-catchment of White Gull Creek Research Basin, Boreal Ecosystem Research and Modelling Site, Saskatchewan. The catchment (Pine Fen Creek) is comprised of a large (30 km2) valley-bottom peatland, two lakes, and jack pine (Pinus banksiana) uplands. The pine uplands are important areas of annual groundwater recharge for the catchment. Vertical hydraulic gradients (VHGs) show frequent flow reversals between the lakes and sand aquifer, and spatially diverse VHGs between the peatland and sand aquifer. Groundwater flow nets and lateral hydraulic gradients indicate the stream receives groundwater along its length. Isotopic samples of end members corroborate the hydrometric data. Catchment streamflow response during the 2011 low flow period was not simply the addition of net groundwater inputs from each landscape unit. Instead, the large size, valley-bottom position, and short water ‘memory’ of the peatland were the critical factors in regulation of catchment streamflow during low flow periods. Peatland hydrologic function alternated between a source and sink of runoff (surface and subsurface) to the stream, dependent on the position of the water table; a value of 0.15 m below peat surface was the critical functional tipping point. Given the high percentage of peatlands (21%) within the Boreal Plain, incorporating their runoff threshold is required in parameterizing runoff generation in hydrological models, and thus predicting impacts of peatland degradation and forest clearing on streamflow.

Inland waters have long been neglected in the global carbon cycle. They represent only 2,8% of the land area, but it has come clear that inland waters play a key role in the transformation of terrestrial fixed carbon to the atmosphere. Human activities do have an impact on the carbon cycling and it is important to understand how these changes affects natural biogeochemical and climatological processes. The purpose of this report was to investigate how forestry impacts the emission of carbon dioxide from boreal lakes and to evaluate which role lakes play in the global carbon cycle. The study was accomplished as a literature study and the search words that have been used are carbon cycling, carbon dioxide, forestry, boreal lakes, dissolved organic carbon and pCO2. The results show that in many studies does forestry increase the export of dissolved organic carbon from terrestrial environments to boreal lakes. This increase subsidies the net heterotrophy in boreal lakes, making them net sources of carbon dioxide to the atmosphere. The processes behind increased concentrations and emissions are however complex and factors like local topography, hydrology and climate are thought to have impacts on how much carbon dioxide that is produced at a given level of dissolved organic carbon. Forestry seems to have an increasing effect on the carbon dioxide emissions, but the key drivers behind this process are expressed differently between regions and the reasons underlying these differences remain to be explored in order to make precise global carbon models.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

An example of watershed disturbance activity undertaken to gain access to the oil sands is large scale mining in the Athabasca basin, Alberta, Canada. One of the remedial activities of this disturbance is the reclamation of the disturbed lands. In the process of reclamation, the overburden soil is placed back into the mined pits and reformed with soil covers (alternatively called reconstructed watersheds). In the design process of reclamation, a major concern is hydrological sustainability, which includes the soils ability to store enough moisture for the water requirements of vegetation growth and land-atmospheric moisture fluxes. Typically, the goal of the reclamation is to restore the disturbed watersheds, so that they mimic the natural watersheds in terms of the ecological sustainability. Therefore, a comparative evaluation of the hydrological sustainability of the reconstructed watersheds with natural watersheds is required.<p>The considered reconstructed watershed in this study (the flat top of the South Bison Hill, Fort McMurray, Alberta, which is about 6 years old) constitutes a thin layer of a peat-mineral mix (20 cm thick) overlying an 80 cm thick secondary (glacial till) layer on the shale formation, mimicking the natural soil horizons of undisturbed watersheds. As the reconstructed watershed is located in the boreal forest region, a mature boreal forest (Old Aspen site, about 88 years old) located in the Southern Study Area (SSA), BOREAS, Saskatchewan, Canada, is considered as a representative of natural watershed. The A-horizon with 25 cm of sandy loam texture, the B-horizon with 45 cm-thick sandy clay loam, and the C-horizon with 40 cm of a mixture of sandy clay loam and loam are considered in this study.<p>An existing System Dynamics Watershed (SDW) model (lumped and site-specific) is modified and adapted to model the hydrological processes of the reconstructed and natural watersheds, such as soil moisture, evapotranspiration, and runoff. The models are calibrated and validated on daily time scale using two years data (growing season) in each case. The hydrological processes are simulated reasonably well despite the high complexity involved in the processes of soil moisture dynamics and the evapotranspiration, for both study areas. Using the modified and calibrated models, long term simulations (48 years) are carried out on both the reconstructed and natural watersheds. Vegetation properties are switched between the reconstructed and natural watersheds and two scenarios are generated. Consequently, long term simulations are performed. With the help of a probabilistic approach, the daily soil moisture results are used to address the comparative soil moisture storage capability of the watersheds.<p>The results indicate that the selected reconstructed watershed is able to provide its designed store-and-release moisture of 160 mm (a requirement of the land capability classification for forest ecosystems in the oil sands) for the vegetation and meteorological moisture demands at a non-exceedance probability of 93%. The comparative study shows that the reconstructed watershed provides less moisture for evapotranspiration requirements than the natural watershed. The reconstructed watershed is able to provide less moisture than the natural watershed for both small and also mature vegetation scenarios. A possible reason for this may be that the reconstructed site is still in the process of restoration and that it may take a few more years to get closer to natural watersheds in terms of the hydrological sustainability. The study also demonstrates the utility of the system dynamics approach of modeling the case study under consideration. The future addition of a vegetation growth model to the hydrological model, and the development of a generic watershed modeling technique would be helpful in decision making and management practices of watershed reclamation.