Airborne laser scanning reveals uniform responses of forest structure to moose (Alces alces) across the boreal forest biome

1. The moose Alces alces is the largest herbivore in the boreal forest biome, where it can have dramatic impacts on ecosystem structure and dynamics. Despite the importance of the boreal forest biome in global carbon cycling, the impacts of moose have only been studied in disparate regional exclosure experiments, leading to calls for common analyses across a biome-wide network of moose exclosures. 2. In this study, we use airborne laser scanning (ALS) to analyse forest canopy re-sponses to moose across 100 paired exclosure-control experimental plots dis-tributed across the boreal biome, including sites in the United States (Isle Royale), Canada (Quebec, Newfoundland), Norway, Sweden and Finland. 3. We test the hypotheses that canopy height, vertical complexity and above- ground biomass (AGB) are all reduced by moose and that the impacts vary with moose density, productivity, temperature and pulse disturbances such as logging and insect outbreaks. 4. We find a surprising convergence in forest canopy response to moose. Moose had negative impacts on canopy height, complexity and AGB as expected. The responses of canopy complexity and AGB were consistent across regions and did not vary along environmental gradients. The difference in canopy height be-tween exclosures and open plots was on average 6 cm per year since the start of exclosure treatment (±2.1 SD). This rate increased with temperature, but only when moose density was high. 5. The difference in AGB between moose exclosures and open plots was 0.306 Mg ha−1 year−1 (±0.079). In browsed plots, stand AGB was 32% of that in the exclosures, a difference of 2.09 Mg ha−1. The uniform response allows scaling of the estimate to a biome-wide impact of moose of the loss of 448 (±115) Tg per year, or 224 Tg of carbon. 6. Synthesis: Analysis of ALS data from distributed exclosure experiments identified a largely uniform response of forest canopies to moose across regions, facilitat-ing scaling of moose impacts across the whole biome. This is an important step towards incorporating the effect of the largest boreal herbivore on the carbon cycling of one of the world's largest terrestrial biomes.publishedVersio

Fertility-dependent effects of ectomycorrhizal fungal communities on white spruce seedling nutrition

© 2015, Springer-Verlag Berlin Heidelberg (outside the USA). Ectomycorrhizal fungi (EcMF) typically colonize nursery seedlings, but nutritional and growth effects of these communities are only partly understood. To examine these effects, Picea glauca seedlings collected from a tree nursery naturally colonized by three dominant EcMF were divided between fertilized and unfertilized treatments. After one growing season seedlings were harvested, ectomycorrhizas identified using DNA sequencing, and seedlings analyzed for leaf nutrient concentration and content, and biomass parameters. EcMF community structure–nutrient interactions were tested using nonmetric multidimensional scaling (NMDS) combined with vector analysis of foliar nutrients and biomass. We identified three dominant species: Amphinema sp., Atheliaceae sp., and Thelephora terrestris. NMDS + envfit revealed significant community effects on seedling nutrition that differed with fertilization treatment. PERMANOVA and regression analyses uncovered significant species effects on host nutrient concentration, content, and stoichiometry. Amphinema sp. had a significant positive effect on phosphorus (P), calcium and zinc concentration, and P content; in contrast, T. terrestris had a negative effect on P concentration. In the unfertilized treatment, percent abundance of the Amphinema sp. negatively affected foliar nitrogen (N) concentration but not content, and reduced foliar N/P. In fertilized seedlings, Amphinema sp. was positively related to foliar concentrations of N, magnesium, and boron, and both concentration and content of manganese, and Atheliaceae sp. had a negative relationship with P content. Findings shed light on the community and species effects on seedling condition, revealing clear functional differences among dominants. The approach used should be scalable to explore function in more complex communities composed of unculturable EcMF

Association of Pinus banksiana Lamb. and Populus tremuloides Michx. seedling fine roots with Sistotrema brinkmannii (Bres.) J. Erikss. (Basidiomycotina)

Sistotrema brinkmannii (Bres.) J. Erikss. (Basidiomycotina, Hydanaceae), commonly regarded as a wood decay fungus, was consistently isolated from bareroot nursery Pinus banksiana Lamb. seedlings. S. brinkmannii was found in ectomycorrhizae formed by Thelephora terrestris Ehrh., Laccaria laccata (Scop.) Cooke, and Suillus luteus (L.) Roussel. In pure culture combinations with sterile P. banksiana and Populus tremuloides Michx. seedlings, S. brinkmannii colonized root cortical cells while not killing seedlings. Colonization by S. brinkmannii appeared to be intracellular but typical endo- or ectomycorrhizae were not formed. The fungus did not decay roots, although it was shown to produce cellulase in enzyme tests. Results suggest a unique association between S. brinkmannii and seedling roots that is neither mycorrhizal nor detrimental; its exact function remains to be elucidated. © 2012 Springer-Verlag (outside the USA)

Interactive plant functional group and water table effects on decomposition and extracellular enzyme activity in Sphagnum peatlands

a b s t r a c t Peatland decomposition may be altered by hydrology and plant functional groups (PFGs), but exactly how the latter influences decomposition is unclear, as are potential interactions of these factors. We used a factorial mesocosm experiment with intact 1 m 3 peat monoliths to explore how PFGs (sedges vs Ericaceae) and water table level individually and interactively affect decomposition processes. Decomposition was measured using litter bags at three depths filled with cellulose strips to mimic decomposition of a simple plant-derived structure, and Sphagnum tissue to simulate decomposition of the most abundant recalcitrant material in peatlands. We also analyzed the potential activity of five hydrolytic extracellular enzymes at an intermediate depth. We found lowered water table reduced activity of several enzymes and increased cellulose and Sphagnum decomposition. Presence of Ericaceae reduced decomposition of the recalcitrant Sphagnum tissue, whereas higher activity of chitinase was found in the combined presence of sedges and Ericaceae. We found no relationship between any potential enzyme activity and Sphagnum decomposition rate. Overall our results showed a dominating role of water table controlling decomposition processes, as well as support for the hypothesis that the presence of mycorrhizal Ericaceae can slow decomposition processes of complex plant tissues in peatlands

Interactive plant functional group and water table effects on decomposition and extracellular enzyme activity in Sphagnum peatlands

© 2017 Elsevier Ltd Peatland decomposition may be altered by hydrology and plant functional groups (PFGs), but exactly how the latter influences decomposition is unclear, as are potential interactions of these factors. We used a factorial mesocosm experiment with intact 1 m3 peat monoliths to explore how PFGs (sedges vs Ericaceae) and water table level individually and interactively affect decomposition processes. Decomposition was measured using litter bags at three depths filled with cellulose strips to mimic decomposition of a simple plant-derived structure, and Sphagnum tissue to simulate decomposition of the most abundant recalcitrant material in peatlands. We also analyzed the potential activity of five hydrolytic extracellular enzymes at an intermediate depth. We found lowered water table reduced activity of several enzymes and increased cellulose and Sphagnum decomposition. Presence of Ericaceae reduced decomposition of the recalcitrant Sphagnum tissue, whereas higher activity of chitinase was found in the combined presence of sedges and Ericaceae. We found no relationship between any potential enzyme activity and Sphagnum decomposition rate. Overall our results showed a dominating role of water table controlling decomposition processes, as well as support for the hypothesis that the presence of mycorrhizal Ericaceae can slow decomposition processes of complex plant tissues in peatlands

Mosaic stunting in bareroot Pinus banksiana seedlings is unrelated to colonization by mycorrhizal fungi

Mosaic stunting, the occurrence of random patches of chlorotic seedlings with reduced shoot and diameter growth amidst more robust cohorts within bareroot nurseries, is classically associated with poor colonization by mycorrhizal fungi. We examined possible relationships among soil fertility, mycorrhizas, and random patches of mosaic stunting in bareroot Pinus banksiana Lamb. and suggest this paradigm is not universal. Stunted seedlings were distributed among healthy seedlings, occupied field space for 2–3 years, and used nursery resources (i.e. irrigation, fertilization); consequently high rates of culling at harvest resulted in an economic stress for the nursery. Thus, an understanding of the cause(s) of stunting was necessary. Stunted 1 + 0 seedlings had significantly lower levels of nitrogen, phosphorus, potassium, and zinc than their healthy cohorts, despite similar soil nutrient levels. The numbers of mycorrhizal root tips on stunted and healthy seedlings were similar, and the taxa of mycorrhizal fungi, determined by isolations and DNA sequencing, were not consistently associated with stunted or healthy seedlings. We conclude that differences in Pinus banksiana mycorrhizas are not responsible for mosaic stunting, but may be caused by localized low soil N availability due to uneven distribution of added organic matter amendments

Biochar and wood ash amendments for forestry in the Lake States: Field report and initial results

© 2018 Society of American Foresters. Soil amendments are common in agriculture but are not widely used in Lake States forestry. Our objectives were to test the efficacy of operational-scale application of soil amendments on marginal sites as a management strategy for adaptation to drier conditions. Wood ash and biochar amendments were applied throughout 50 acres of recently harvested scrub oak stands, and red and jack pine seedlings were planted. Short-term results indicate increased water holding capacity and cation exchange capacity in soils amended with biochar and biochar with manure and significant increases in seedling production with wood ash amendment. Here we report on the feasibility of the application methods and their associated financial costs and present initial data on soil properties after amendment with wood ash and biochar

Biochar and Wood Ash Amendments for Forestry in the Lake States: Field Report and Initial Results

© 2018 Society of American Foresters. Soil amendments are common in agriculture but are not widely used in Lake States forestry. Our objectives were to test the efficacy of operational-scale application of soil amendments on marginal sites as a management strategy for adaptation to drier conditions. Wood ash and biochar amendments were applied throughout 50 acres of recently harvested scrub oak stands, and red and jack pine seedlings were planted. Short-term results indicate increased water holding capacity and cation exchange capacity in soils amended with biochar and biochar with manure and significant increases in seedling production with wood ash amendment. Here we report on the feasibility of the application methods and their associated financial costs and present initial data on soil properties after amendment with wood ash and biochar

Impacts of experimental alteration of water table regime and vascular plant community composition on peat mercury profiles and methylmercury production

Climate change is expected to alter the hydrology and vascular plant communities in peatland ecosystems. These changes may have as yet unexplored impacts on peat mercury (Hg) concentrations and net methylmercury (MeHg) production. In this study, peat was collected from PEATcosm, an outdoor, controlled mesocosm experiment where peatland water table regimes and vascular plant functional groups were manipulated over several years to simulate potential climate change effects. Potential Hg(II) methylation and MeHg demethylation rate constants were assessed using enriched stable isotope incubations at the end of the study in 2015, and ambient peat total Hg (THg) and MeHg concentration depth profiles were tracked annually from 2011 to 2014. Peat THg and MeHg concentrations and the proportion of THg methylated (%MeHg) increased significantly within the zone of water table fluctuation when water tables were lowered, but potential Hg(II) methylation rate constants were similar regardless of water table treatment. When sedges dominate over ericaceous shrubs, MeHg concentrations and %MeHg became significantly elevated within the sedge rooting zone. Increased desorption of Hg(II) and MeHg from the solid phase peat into pore water occurred with a lowered water table and predominant sedge cover, likely due to greater aerobic peat decomposition. Deeper, more variable water tables and a transition to sedge-dominated communities coincided with increased MeHg accumulation within the zone of water table fluctuation. Sustained high water tables promoted the net downward migration of Hg(II) and MeHg. The simultaneous decrease in Hg(II) and MeHg concentrations in the near-surface peat and accumulation deeper in the peat profile, combined with the trends in Hg(II) and MeHg partitioning to mobile pore waters, suggest that changes to peatland hydrology and vascular plant functional groups redistribute peat Hg(II) and MeHg via vertical hydrochemical transport mechanisms

Effects of water table position and plant functional group on plant community, aboveground production, and peat properties in a peatland mesocosm experiment (PEATcosm)

© 2014, Springer Science+Business Media B.V. (outside the USA). Aims: Our objective was to assess the impacts of water table position and plant functional type on peat structure, plant community composition and aboveground plant production.Methods: We initiated a full factorial experiment with 2 water table (WT) treatments (high and low) and 3 plant functional groups (PFG: sedge, Ericaceae, sedge and Ericaceae- unmanipulated) in twenty-four 1 m3 intact peatland mesocosms. We measured vegetation cover, aboveground plant production, and peat subsidence to analyze interactive PFG and WT effects.Results: Sphagnum rubellum cover increased under high WT, while Polytrichum cover increased with low WT and in sedge only PFGs. Sphagnum production was greatest with high WT, while vascular plant production was greater in low WT treatments. There was an interactive WT x PFG effect on Ericaceae production. Lowered WT resulted in significant peat surface change and increased subsidence. There were significant PFG and WT effects on net peat accumulation, with the lowest rates of accumulation, high and low WT, in sedge only PFGs.Conclusions: The shift in water balance leading to lowered water table position predicted with changing climate could impact plant community composition and production, and would likely result in the subsidence of peat