Federico P.O. Mollard

Monitoring and Assessment of Wetland Condition Using Plant Morphologic and Physiologic Indicators

We created and evaluated indices of plant performance using plant morphological and physiological attributes and assessed their potential as wetland condition indicators by studying their consistency along a stress gradient. Based on Spearman coefficients, we selected promising morphological and physiological metrics that showed consistent responses along a physico-chemical stress gradient. Metrics consistently associated with wetland condition were ranked and combined into morphological (mPPI) or physiological Plant Performance Indices (phPPI). Six morphological metrics were able to discern between good and poor wetland conditions along the impact gradient and were thereafter combined into the mPPI. The resulting mPPI was found to be a strong indicator of stress and accurately identified degraded wetlands (rs = −0.52; P = 0.030). In contrast, most of the physiologic metrics showed lower correlations to the stress gradient. Consequently, the resulted phPPI had a lack of association with the stress gradient and failed to identify even heavily-impacted wetlands (rs = −0.30; P = 0.194). We conclude that the morphological characteristics of plants, the reliability of the mPPI, and its ability to simply and easily convey habitat information makes it worthy of further refinement and validation as a tool for evaluating mitigation and restoration efforts in wetlands.

Geographic variation in the flood-induced fluctuating temperature requirement for germination in Setaria parviflora seeds.

Our aim was to search for specific seed germinative strategies related to flooding escape in Setaria parviflora, a common species across the Americas. For this purpose, we investigated induction after floods, in relation to fluctuating temperature requirements for germination in seeds from mountain, floodplain and successional grasslands. A laboratory experiment was conducted in which seeds were imbibed or immersed in water at 5°C. Seeds were also buried in flood-prone and upland grasslands and exhumed during the flooding season. Additionally, seeds were buried in flooded or drained grassland mesocosms. Germination of exhumed seeds was assayed at 25°C or at 20°C/30°C in the dark or in the presence of red light pulses. After submergence or soil flooding, a high fraction (>32%) of seeds from the floodplain required fluctuating temperatures to germinate. In contrast, seeds from the mountains showed maximum differences in germination between fluctuating and constant temperature treatment only after imbibition (35%) or in non-flooded soil conditions (40%). The fluctuating temperature requirement was not clearly related to the foregoing conditions in the successional grassland seeds. Maximum germination could also be attained with red light pulses to seeds from mountain and successional grasslands. Results show that the fluctuating temperature requirement might help floodplain seeds to germinate after floods, indicating a unique feature of the dormancy of S. parviflora seeds from floodplains, which suggests an adaptive advantage aimed at postponing emergence during inundation periods. In contrast, the fluctuating temperature required for germination among seeds from mountain and successional grasslands show its importance for gap detection.

Enriched Topographic Microsites for Improved Native Grass and Forb Establishment in Reclamation

ABSTRACT Low seed germination and seedling establishment are the greatest challenges for revegetation success. Topographic microsites are known to enhance seed germination and seedling establishment due to their unique soil properties and provision of shelter from elements and herbivores; soil amendments can supply organic matter and nutrients for plant establishment and growth when limited. We investigated the effect of three topographic microsites and six soil amendments and their additive effects on three disturbed grasslands in central and southern Alberta, Canada. Treatments were topographic microsites of mounds, pits, and flats, with and without amendments (erosion control blanket, hay, straw, manure, hydrogel, control) and were seeded with four native grasses and three native forb species. Seedling emergence and survival and soil temperature and water content were assessed over two seasons and plant cover over three seasons. The effect of microsites and amendments was not additive. The addition of erosion control blanket, hay, and straw to flat sites was just as productive as on topographic microsites. These amendments increased grass and forb emergence and buffered soil temperature. Mounds increased first year forb emergence and reduced over winter survival rates for grasses and forbs. Pits were not beneficial for revegetation. The effect of topographic microsites and amendments was influenced by site conditions.