Ancient CO2 levels favor nitrogen fixing plants over a broader range of soil N compared to present

Small inreases in CO2 stimulate nitrogen fixation and plant growth. Increasing soil N can inhibit nitrogen fixation. However, no studies to date have tested how nitrogen fixing plants perform under ancient CO2 levels (100 MYA), when nitrogen fixing plants evolved, with different levels of N additions. The aim of this study was to assess if ancient CO2, compared to present, favors nitrogen fixers over a range of soil nitrogen concentrations. Nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) were grown at ancient (1600 ppm) or present (400 ppm) CO2 over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha−1 year−1. The growth of non-N fixing plants increased more than N fixing plants in response to the increasing N levels. When grown at an ancient CO2 level, the N level at which non-nitrogen fixing plant biomass exceeded nitrogen fixing plant biomass was twice as high (61 kg N ha−1 year−1) as the N level when plants were grown at the ambient CO2 level. Specific nodule activity was also reduced with an increasing level of soil N. Our results show there was a greater advantage in being a nitrogen fixer under ancient levels of CO2 compared with the present CO2 level.

Biochar effects on germination and radicle extension in temperate tree seedlings under field conditions

Pyrolyzed organic matter, or biochar, generally increases the growth of established plants; in some cases, biochar also promotes seed germination in agricultural species, but comparable effects on tree species have received little attention. Potential biochar effects on seed germination and early seedling development were examined in a field experiment involving 14 species of temperate forest trees. Replicated sets of seeds with and without biochar (at 5 t·ha–1) were placed in mesh bags beneath leaf litter near the time of autumnal leaf fall and retrieved the following spring. Pooled analyses show a positive but small average effect of biochar on germination. Effects on seedling radicle extension growth were more pronounced, with more than a doubling in growth observed overall and large increases observed in some species, including both conifers (e.g., Picea mariana (Mill.) Britton, Sterns & Poggenb. and Pinus resinosa Sol. ex Aiton) and angiosperms (Betula papyrifera Marsh., Prunus virginiana L., and Ulmus americana L.). Species varied in responses, but differences were not related to fire or shade tolerance. The results indicate that biochar can substantially enhance early seedling development in temperate trees; likely mechanisms involve “priming” effects resulting from increased pH and potassium availability or sorption of germination-inhibiting phenolics in the litter layer.

Ancient CO2 Levels Favor Nitrogen Fixing Plants Over a Broader Range of Soil N Compared to Present

Small inreases in CO2 stimulate nitrogen fixation and plant growth. Increasing soil N can inhibit nitrogen fixation. However, no studies to date have tested how nitrogen fixing plants perform under ancient CO2 levels (100 MYA) when nitrogen fixers evolved, with different levels of N additions. The aim of this study was to assess if ancient CO2, compared to present, favors nitrogen fixers over a range of soil nitrogen concentrations. Nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) were grown at ancient CO2 (1600 ppm) or present CO2 (400 ppm) over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha-1 year-1. The growth of non-N fixing plants increased more than N fixing plants in response to the increasing N levels. When grown at an ancient CO2 level, the N level at which non-nitrogen fixing plant biomass exceeded nitrogen fixing plant biomass was twice as high (61 kg N ha-1 y-1) as the N level when plants were grown at an ambient CO2 level. Specific nodule activity was also reduced with an increasing level of soil N. Our results showed there was a greater advantage in being a nitrogen fixer under ancient levels of CO2 compared with the present CO2 level.

Naturalness Assessment of Forest Management Scenarios in Abies balsamea–Betula papyrifera Forests

Research Highlights: This research provides an application of a model assessing the naturalness of the forest ecosystem to demonstrate its capacity to assess either the deterioration or the rehabilitation of the ecosystem through different forest management scenarios. Background and Objectives: The model allows the assessment of the quality of ecosystems at the landscape level based on the condition of the forest and the proportion of different forest management practices to precisely characterize a given strategy. The present work aims to: (1) verify the capacity of the Naturalness Assessment Model to perform bi-directional assessments, allowing not only the evaluation of the deterioration of naturalness characteristics, but also its improvement related to enhanced ecological management or restoration strategies; (2) identify forest management strategies prone to improving ecosystem quality; (3) analyze the model’s capacity to summarize the effect of different practices along a single alteration gradient. Materials and Methods: The Naturalness Assessment Model was adapted to the Abies balsamea–Betula papyrifera forest of Quebec (Canada), and a naturalness assessment of two sectors with different historical management strategies was performed. Fictive forest management scenarios were evaluated using different mixes of forestry practices. The sensitivity of the reference data set used for the naturalness assessment has been evaluated by comparing the results using data from old management plans with those based on Quebec’s reference state registry. Results: The model makes it possible to identify forest management strategies capable of improving ecosystem quality compared to the current situation. The model’s most sensitive variables are regeneration process, dead wood, closed forest and cover type. Conclusions: In the Abies balsamea–Betula papyrifera forest, scenarios with enhanced protection and inclusion of irregular shelterwood cuttings could play an important role in improving ecosystem quality. Conversely, scenarios with short rotation (50 years) could lead to further degradation of the ecosystem quality.

Semiochemical-mediated aggregation of the ambrosia beetle Trypodendron betulae (Coleoptera: Curculionidae: Scolytinae)

Porapak Q-captured volatiles from both sexes of Trypodendron betulae Swaine (Coleoptera: Curculionidae: Scolytinae) excised from newly attacked logs of paper birch, Betula papyrifera Marshall (Betulaceae), as well as volatiles from unattacked birch logs, were analysed by coupled gas chromatographic electroantennographic detection analysis. Active compounds were identified by gas chromatographic mass spectroscopy. The enantiomeric ratio of 6-ethenyl-2,2,6-trimethyloxan-3-ol (linalool oxide pyranoid) was determined using a Cyclodex B column. Field-trapping experiments disclosed that the female-produced aggregation pheromone of T. betulae is a blend of the (3S,6R)-trans- and (3R,6R)-cis-linalool oxide pyranoid. Trap catches were synergistically increased when the pheromone was combined with both the host volatile ethanol and with conophthorin, which was found in female beetles as well as host volatiles. Use of linalool oxide pyranoid reproductively isolates T. betulae from sympatric Trypodendron Stephens species for which only (+)-lineatin has been identified as an aggregation pheromone.