Assessing ecohydrological separation in a northern mixed forest biome using stable isotopes

In recent years, much attention has been paid to the issue of ecohydrological separation during water uptake by vegetation. This has been spurred in part by the two water worlds hypothesis, whereby mobile blue water contributes to groundwater recharge and streamflow generation whereas less mobile green water held in the soil is taken up and transpired by vegetation. This study examines the potential for ecohydrological separation in a northern mixed forest in Ontario, Canada. Stable isotopic compositions of gross precipitation, bulk soil water and xylem water were measured throughout the 2016 growing season for four species: eastern white cedar, eastern hemlock, red oak and eastern white pine. Near-bole soil water contents and mobile soil water isotopic compositions were measured for the last three species. Mobile soil water did not deviate significantly from the local meteoric water line (LMWL); in contrast, both bulk soil water and xylem water deviated significantly from the LMWL, with xylem water significantly depleted in 18O and particularly 2H relative to bulk soil water. Near-surface bulk soil water experienced evaporative enrichment from pre-leaf out to peak leaf out under all tree canopies. There were inter-species differences in displacement of xylem water isotopic compositions from the LMWL and their temporal changes during the growing season, with those of coniferous species becoming isotopically enriched while those of red oak became more depleted in 2H and 18O. These divergences occurred despite thin soil cover (generally

Harpalejeunea molleri subsp. integra (R.M. Schuster) Damsholt new to Atlantic Canada

Harpalejeunea molleri subsp. integra (R.M. Schuster) Damsholt is reported for the first time in Atlantic Canada. It was found on the base of a large Eastern White Cedar (Thuja occidentalis) in a swamp in Nova Scotia. The specimen was examined using light microscopy, diagnosed using standard keys, and compared with reference specimens, including two European collections from the New Brunswick Museum, two North American collections annotated by R.M. Schuster, and the only material that may have been previously collected in Canada, by T. Drummond. We speculate on the original location of Drummond’s collection, and the implications of this finding for conservation.

Increasing amounts of coir dust in substrates do not improve physical properties or growth of tree seedlings in a novel air-pruning propagation tray1

Air-pruning can improve tree seedling root quality in propagation by subjecting root tips to desiccation, thereby avoiding deflections, but also increases substrate dry-out rates. Several studies have indicated that coconut (Cocos nucifera L.) coir dust can enhance water holding properties, possibly benefiting trees grown in air-pruning trays. However, water availability characteristics are influenced by particle size. In this experiment, coir dust was added into a sphagnum peat-perlite substrate mix at rates of 10, 15 and 20%. An industry standard peat-perlite mix was tested as a fourth substrate type. Red oak (Quercus rubra L.), red maple (Acer rubrum L.), quaking aspen (Populus tremuloides Michx.) and eastern white cedar (Thuja occidentalis L.) were grown from seed in these four substrate types. Physical and chemical properties of all substrate types were analyzed pre-experiment. The particle size distribution was finer and more even in the peat-perlite mix compared to the three coir mixes. The higher proportion of coarse particles in the 20% coir mix may have reduced water availability. Seedlings grown in the 15 and 20% coir mixes had lower above and below-ground growth compared to the 10% coir and peat-perlite mixes in all species except red oak. Index words: soilless media, water holding capacity, air space, particle size distribution, chlorophyll content, tree growth. Species used in the study: red oak (Quercus rubra L.); red maple (Acer rubrum L.); quaking aspen (Populus tremuloides Michx.); eastern white cedar (Thuja occidentalis L.).

Are marginal balsam fir and eastern white cedar stands relics from once more extensive populations in north-eastern North America?

Marginal stands of balsam fir ( Abies balsamea [L.] Mill.) and eastern white cedar ( Thuja occidentalis L.) are found north of their limits of continuous distribution in eastern North America. Regional-scale paleoecological studies have suggested that fir and cedar populations could have had larger extents in the past. This study aimed at verifying this hypothesis at the local scale. Wood charcoal fragments were collected from the soils of two marginal fir and cedar stands as well as from 15 sites in the surrounding forest matrix where the species are absent currently. Anatomical identification and radiocarbon-dating showed that fir was more extensive in the study area until about 680 cal. BP, representing up to 31% of the charcoal assemblages at sites where it is currently absent. The evidence is less conclusive for cedar, however, although some of the charcoal fragments from the matrix sites could have been either fir or cedar (undistinguishable). Most of the dated fir/cedar charcoal in the matrix were from the ‘Medieval Warm Period’ (ca. 1000 cal. BP), suggesting contraction may have occurred at that time. Marginal fir – and possibly cedar – stands are thus relics of once more extensive populations. Fire is likely the main factor having contributed to the contraction of the species’ distributions. Fir and cedar are now relegated to areas where fires are less frequent and severe, such as the shores of lakes and rivers.

Glyphosate tolerance of eastern white cedar: Third year results

Little is known about the herbicide tolerance of eastern white cedar (Thuja occidentalis L.). To determine the sensitivity of cedar seedlings to timing and concentration of herbicide applications, glyphosate was applied to 2-year-old seedlings at three concentrations (1.04, 2.07, and 4.14 acid equivalent (ae) kg ha-1) at three times (July 28, August 10 and 31), at a research site in north central Ontario. Seedling survival, growth, and biomass three years after spraying were compared with those of seedlings in manual weeding (competition/weed free via manual weeding) and control (no weeding and therefore always competition/weeds) treatments. Only glyphosate applied at 4.14 ae kg ha-1 significantly reduced, by 27%, third year seedling survival. Pattern of sensitivity of cedar seedling growth to glyphosate was diameter>height. Seedlings treated with 2.07 and 4.14 ae kg ha-1 glyphosate had significantly less root biomass than those in the control plots, whereas only cedar treated with 4.14 ae kg ha-1 glyphosate had lower shoot biomass. Application timing made no difference in survival, growth, or final biomass. All glyphosate and the no weeding control treatments reduced root, shoot, and total biomass of cedar relative to the manually weeded seedlings.

Square-stalked St. John’s-wort, Hypericum tetrapterum, in Peel Region, Ontario: a New Non-native Vascular Plant Species for Eastern North America

The Eurasian Square-stalked St. John’s-wort (Hypericum tetrapterum Fr.: Hypericaceae) was found growing in an open Eastern White Cedar (Thuja occidentalis L.) swamp in Caledon, Regional Municipality of Peel, Ontario. This is the first record for eastern North America; previous North American occurrences have been on the Pacific coast in Vancouver, British Columbia, Canada (1991), and in Wahkiakum County, Washington State, USA (2003).

A new secondary ecotope for talitrids: driftwood in the Bay of Fundy

Platorchestia platensis (Amphipoda, Talitridae) was previously known ecologically as a wrack generalist, but here we describe a secondary driftwood ecotope for this species. The trophic dependence of driftwood-acclimated P. platensis on rotting wood was confirmed by successfully culturing it within driftwood, without further addition of food. The stranded driftwood in which P. platensis was found contained gribble burrows (round and of 0.6 to 5 mm diameter). We hypothesize that P. platensis used the empty gribble burrows for interspecific squatting (to gain initial entry to driftwood and for shelter). We found eleven driftwood depositories in a 230 km length of shoreline in Passamaquoddy Bay. The commonest driftwood was of spruce and eastern white cedar. The small marsh at Hartley Cove contained a driftwood depository, where the new driftwood ecotope was discovered. This site was studied temporally to understand how wind and tidal forces might affect import and export of driftwood.

Determining the glyphosate tolerance of eastern white cedar: First year post-treatment results

Little is known about the silvicultural traits of eastern white cedar (Thuja occidentalis L.), and especially the tolerance of seedlings to herbicides. A study was established to determine the sensitivity of cedar seedlings to timing and concentration of glyphosate applications. Glyphosate was applied to seedlings at three concentrations (1.04, 2.07, and 4.14 acid equivalent (ae) kg ha-1) at three times (July 28, August 10 and August 31) and their survival and growth was compared with that of seedlings in three control treatments (competition free, always competition, and competition free after an August 10 application of 2.07 kg ha-1 glyphosate) for a total of 12 treatments. Damage to foliage increased (r2 = 0.99) and first-year volume growth decreased (r2 = 0.91) with increasing glyphosate concentration. Glyphosate applied at 4.14 kg ha-1 killed 9% of the seedlings; even the lowest concentration of glyphosate (1.04 kg ha-1) reduced first-year volume growth more than continuous herbaceous competition. Application timing did not affect the amount of foliar damage or the growth of seedlings. However, in the winter following the treatments, snow damage was greater in the weed-free control seedlings than in all other treatments.