Beavers are a keystone species known to strategically impound streamflow by building dams. Beaver colonization involves upstream ponding; after abandonment, the dams degrade, and the ponds slowly drain. This ponding-draining cycle likely modifies peatland nutrient availability, which is an important control on vegetation distribution and productivity. We compared soil mineral nutrient supply patterns in a beaver-dammed peatland in the Canadian Rocky Mountains over the growing and senescence study seasons during 2020. We used a nested design, comparing nutrient supply with ion-exchange probes among a full beaver pond (FBP with deep and shallow ponding), a drained beaver pond (DBP at its centre and margin) and unimpacted fen (UF at hummock and hollow hydrologic zones). Overall, FBP had lower soil total inorganic nitrogen (TIN) and nitrate (NO3), and higher ammonium (NH4) and phosphorus (PO4) supplies compared to UF. Interestingly, beaver pond drainage tended to restore the nutrient supply to its original status. The patterns we found in nutrient supply were consistent between the growing and senescence seasons. The key drivers of nutrient dynamics were water table level and soil temperature at 5 cm depth (TSoil); however, the controls affected each of the nutrients differently. Deepening of the water table level and higher TSoil non-linearly increased TIN/NO3 but decreased NH4 and PO4. We suggest that the variations in peatland nutrient availabilities in response to the beaver’s ponding-draining cycle may support downstream ecosystem heterogeneity and plant community composition diversity at a longer time scale.

Beaver dam analogues (BDAs) are becoming an increasingly popular stream restoration technique. One ecological function BDAs might help restore is suitable habitat conditions for fish in streams where loss of beaver dams and channel incision has led to their decline. A critical physical characteristic for fish is stream temperature. We examined the thermal regime of a spring-fed Canadian Rocky Mountain stream in relation to different numbers of BDAs installed in series over three study periods (April–October; 2017–2019). While all BDA configurations significantly influenced stream and pond temperatures, single- and double-configuration BDAs incrementally increased stream temperatures. Single and double configuration BDAs warmed the downstream waters of mean maxima of 9.9, 9.3 °C by respective mean maxima of 0.9 and 1.0 °C. Higher pond and stream temperatures occurred when ponding and discharge decreased, and vice versa. In 2019, variation in stream temperature below double-configuration BDAs was lower than the single-configuration BDA. The triple-configuration BDA, in contrast, cooled the stream, although the mean maximum stream temperature was the highest below these structures. Ponding upstream of BDAs increased discharge and resulted in cooling of the stream. Rainfall events sharply and transiently reduced stream temperatures, leading to a three-way interaction between BDA configuration, rainfall and stream discharge as factors co-influencing the stream temperature regime. Our results have implications for optimal growth of regionally important and threatened bull and cutthroat trout fish species.

Beaver dam analogues (BDAs) are intended to simulate natural beaver dam ecohydrological functions including modifying stream hydrology and enhancing stream‐riparian hydrological connectivity. River restoration practitioners are proactively deploying BDAs in thousands of degraded streams. How various BDAs or their configurations impact stream hydrology and the riparian water table remains poorly understood. We investigated three types of BDA configurations (single, double and triple) in a spring‐fed Canadian Rocky Mountain stream over three study seasons (April–October; 2017–2019). All three BDA configurations significantly elevated the upstream stage. The deepest pools occurred upstream of the triple‐configuration BDAs (0.46 m) and the shallowest pools occurred upstream of the single‐configuration (0.36 m). Further, the single‐BDA configuration lowered stream stage and flow peaks below it but raised low flows. The double‐BDA configuration modulated flow peaks but had little influence on low flows. Unexpectedly, higher flow peaks and low flows were recorded below the triple‐BDA configuration, owing to groundwater seep. Similar to the natural beaver dam function, we observed an immediate water table rise in the riparian area after installation of the BDAs. The water table rise was greatest 2 m from the stream (0.14 m) and diminished with increasing lateral distance from the stream. Also noted was a reversal in the direction of flow between the stream and riparian area after BDA installation. Future research should further explore the dynamics of stream‐riparian hydrological connections under various BDA configurations and spacings, with the goal of identifying best practices for simulating the ecohydrological functions of natural beaver dams.

Abstract. Rain-fed peatlands are dominated by peat mosses (Sphagnum sp.), which for their growth depend on elements from the atmosphere. As the isotopic composition of carbon (12,13C) and oxygen (16,18O) of these Sphagnum mosses are affected by environmental conditions, the dead Sphagnum tissue accumulated in peat constitutes a potential long-term archive that can be used for climate reconstruction. However, there is a lack of adequate understanding of how isotope values are influenced by environmental conditions, which restricts their current use as environmental and palaeoenvironmental indicators. Here we tested (i) to what extent C and O isotopic variation in living tissue of Sphagnum is species-specific and associated with local hydrological gradients, climatic gradients (evapotranspiration, temperature, precipitation), and elevation; (ii) if the C isotopic signature can be a proxy for net primary productivity (NPP) of Sphagnum; and (iii) to what extent Sphagnum tissue δ18O tracks the δ18O isotope signature of precipitation. In total, we analysed 337 samples from 93 sites across North America and Eurasia using two important peat-forming Sphagnum species (S. magellanicum, S. fuscum) common to the Holartic realm. There were differences in δ13C values between species. For S. magellanicum δ13C decreased with increasing height above the water table (HWT, R2 = 17 %) and was positively correlated to productivity (R2 = 7 %). Together these two variables explained 46 % of the between-site variation in δ13C values. For S. fuscum, productivity was the only significant predictor of δ13C (total R2 = 6 %). For δ18O values, ca. 90 % of the variation was found between sites. Globally-modelled annual δ18O values in precipitation explained 69% of the between-site variation in tissue δ18O. S. magellanicum showed lower δ18O enrichment than S. fuscum (−0.83 ‰ lower) . Elevation and climatic variables were weak predictors of tissue δ18O values after controlling for δ18O values of the precipitation. To summarise, our study provides evidence for (a) good predictability of tissue δ18O values from modelled annual δ18O values in precipitation, and (b) the possibility to relate tissue δ13C values to HWT and NPP, but this appears to be species-dependent. These results suggest that isotope composition can be used at a large scale for climatic reconstructions but that such models should be species-specific.