Climatic Aridity Shapes Post-Fire Interactions between Ceanothus spp. and Douglas-Fir (Pseudotsuga menziesii) across the Klamath Mountains

Climate change is leading to increased drought intensity and fire frequency, creating early-successional landscapes with novel disturbance–recovery dynamics. In the Klamath Mountains of northwestern California and southwestern Oregon, early-successional interactions between nitrogen (N)-fixing shrubs (Ceanothus spp.) and long-lived conifers (Douglas-fir) are especially important determinants of forest development. We sampled post-fire vegetation and soil biogeochemistry in 57 plots along gradients of time since fire (7–28 years) and climatic water deficit (aridity). We found that Ceanothus biomass increased, and Douglas-fir biomass decreased with increasing aridity. High aridity and Ceanothus biomass interacted with lower soil C:N more than either factor alone. Ceanothus biomass was initially high after fire and declined with time, suggesting a large initial pulse of N-fixation that could enhance N availability for establishing Douglas-fir. We conclude that future increases in aridity and wildfire frequency will likely limit post-fire Douglas-fir establishment, though Ceanothus may ameliorate some of these impacts through benefits to microclimate and soils. Results from this study contribute to our understanding of the effects of climate change and wildfires on interspecific interactions and forest dynamics. Management seeking to accelerate forest recovery after high-severity fire should emphasize early-successional conifer establishment while maintaining N-fixing shrubs to enhance soil fertility.

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Persistence of the Swiss Needle Cast Outbreak in Oregon Coastal Douglas-Fir and New Insights from Research and Monitoring

Journal of Forestry ◽

10.1093/jofore/fvab011 ◽

2021 ◽

Author(s):

David C Shaw ◽

Gabriela Ritóková ◽

Yung-Hsiang Lan ◽

Doug B Mainwaring ◽

Andrew Russo ◽

...

Keyword(s):

Climate Change ◽

Regional Scale ◽

Emerging Diseases ◽

Douglas Fir ◽

Landscape Patterns ◽

Needle Cast ◽

Plantation Management ◽

Environmental Controls ◽

Swiss Needle Cast ◽

Improvement Programs

Abstract Swiss needle cast (SNC), caused by Nothophaeocryptopus gaeumannii, is a foliage disease of Douglas-fir (Pseudotsuga menziesii), that reduces growth in native stands and exotic plantations worldwide. An outbreak of SNC began in coastal Oregon in the mid-1990s and has persisted since that time. Here we review the current state of knowledge after 24 years of research and monitoring, with a focus on Oregon, although the disease is significant in coastal Washington and has recently emerged in southwestern British Columbia. We present new insights into SNC distribution, landscape patterns, disease epidemiology and ecology, host-pathogen interactions, trophic and hydrologic influences, and the challenges of Douglas-fir plantation management in the presence of the disease. In Oregon, the SNC outbreak has remained geographically contained but has intensified. Finally, we consider the implications of climate change and other recently emerged foliage diseases on the future of Douglas-fir plantation management. Study Implications: Douglas-fir tree growers need to consider Swiss needle cast (SNC) and other emerging foliage diseases as SNC has not abated over the past 24 years, and along with other emerging diseases, it continues to pose a threat to Douglas-fir plantation productivity. Douglas-fir management in western Oregon remains important, such that a knowledge of disease impacts and effective silvicultural responses is key. Managers should carefully consider whether alternative species may be ecologically or economically beneficial in some situations while tree improvement programs must continue to breed for tolerance to SNC. Research shows that regional scale foliage disease outbreaks can result in trophic cascades and hydrologic changes that affects more than just the trees. The environmental controls on the SNC epidemic imply that climate change could strongly influence future directions of the outbreak, with the greatest threats to trees at higher elevations.

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Insights into mechanisms governing forest carbon response to nitrogen deposition: a model–data comparison using observed responses to nitrogen addition

Biogeosciences ◽

10.5194/bg-10-3869-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 3869-3887 ◽

Cited By ~ 46

Author(s):

R. Q. Thomas ◽

G. B. Bonan ◽

C. L. Goodale

Keyword(s):

Plant Uptake ◽

Temperate Forest ◽

Growth Response ◽

N Fertilization ◽

N Deposition ◽

Forest Carbon ◽

Biogeochemical Model ◽

N Fixation ◽

N Availability ◽

Fertilization Experiments

Abstract. In many forest ecosystems, nitrogen (N) deposition enhances plant uptake of carbon dioxide, thus reducing climate warming from fossil fuel emissions. Therefore, accurately modeling how forest carbon (C) sequestration responds to N deposition is critical for understanding how future changes in N availability will influence climate. Here, we use observations of forest C response to N inputs along N deposition gradients and at five temperate forest sites with fertilization experiments to test and improve a global biogeochemical model (CLM-CN 4.0). We show that the CLM-CN plant C growth response to N deposition was smaller than observed and the modeled response to N fertilization was larger than observed. A set of modifications to the CLM-CN improved the correspondence between model predictions and observational data (1) by increasing the aboveground C storage in response to historical N deposition (1850–2004) from 14 to 34 kg C per additional kg N added through deposition and (2) by decreasing the aboveground net primary productivity response to N fertilization experiments from 91 to 57 g C m−2 yr−1. Modeled growth response to N deposition was most sensitive to altering the processes that control plant N uptake and the pathways of N loss. The response to N deposition also increased with a more closed N cycle (reduced N fixation and N gas loss) and decreased when prioritizing microbial over plant uptake of soil inorganic N. The net effect of all the modifications to the CLM-CN resulted in greater retention of N deposition and a greater role of synergy between N deposition and rising atmospheric CO2 as a mechanism governing increases in temperate forest primary production over the 20th century. Overall, testing models with both the response to gradual increases in N inputs over decades (N deposition) and N pulse additions of N over multiple years (N fertilization) allows for greater understanding of the mechanisms governing C–N coupling.

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Effects of climate change on labile and structural carbon in Douglas-fir needles as estimated by δ13 C and Carea measurements

Global Change Biology ◽

10.1046/j.1365-2486.2002.00541.x ◽

2002 ◽

Vol 8 (11) ◽

pp. 1072-1084 ◽

Cited By ~ 18

Author(s):

ERIC A. HOBBIE ◽

JILLIAN GREGG ◽

DAVID M. OLSZYK ◽

PAUL T. RYGIEWICZ ◽

DAVID T. TINGEY

Keyword(s):

Climate Change ◽

Douglas Fir ◽

Structural Carbon

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Using a climatic niche model to predict the direct and indirect impacts of climate change on the distribution of Douglas-fir in New Zealand

Global Change Biology ◽

10.1111/j.1365-2486.2011.02486.x ◽

2011 ◽

Vol 17 (12) ◽

pp. 3608-3619 ◽

Cited By ~ 12

Author(s):

Michael S. Watt ◽

Jeffrey K. Stone ◽

Ian A. Hood ◽

Lucy K. Manning

Keyword(s):

Climate Change ◽

New Zealand ◽

Douglas Fir ◽

Climatic Niche ◽

Niche Model ◽

Direct And Indirect Impacts ◽

Indirect Impacts ◽

Impacts Of Climate Change

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Climate change exacerbates interspecific interactions in sympatric coastal fishes

Journal of Animal Ecology ◽

10.1111/j.1365-2656.2012.02034.x ◽

2012 ◽

Vol 82 (2) ◽

pp. 468-477 ◽

Cited By ~ 58

Author(s):

Marco Milazzo ◽

Simone Mirto ◽

Paolo Domenici ◽

Michele Gristina

Keyword(s):

Climate Change ◽

Interspecific Interactions

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Ant-mediated seed dispersal in a warmed world

10.7287/peerj.preprints.137v2 ◽

2013 ◽

Author(s):

Katharine L. Stuble ◽

Courtney M. Patterson ◽

Mariano A. Rodriguez-Cabal ◽

Relena R. Ribbons ◽

Robert R. Dunn ◽

...

Keyword(s):

Climate Change ◽

Seed Dispersal ◽

Interspecific Interactions ◽

Forest Site ◽

Activity Levels ◽

Seed Removal ◽

Experimental Warming ◽

Climatic Warming ◽

Plant Seed ◽

Species Specific

Climate change affects communities both directly and indirectly via changes in interspecific interactions. One such interaction that may be altered under climate change is the ant-plant seed dispersal mutualism common in deciduous forests of the eastern US. As climatic warming alters the abundance and activity levels of ants, the potential exists for shifts in rates of ant-mediated seed removal. We used an experimental temperature manipulation at two sites in the eastern US (Harvard Forest in Massachusetts and Duke Forest in North Carolina) to examine the potential impacts of climatic warming on overall rates of seed dispersal (using Asarum canadense seeds) as well as species-specific rates of seed dispersal at the Duke Forest site. We also examined the relationship between ant critical thermal maxima (CTmax) and the mean seed removal temperature for each ant species. We found that seed removal rates did not change as a result of experimental warming at either study site, nor were there any changes in species-specific rates of seed dispersal. There was, however, a positive relationship between CTmax and mean seed removal temperature, whereby species with higher CTmax removed more seeds at hotter temperatures. The temperature at which seeds were removed was influenced by experimental warming as well as diurnal and day-to-day fluctuations in temperature. Taken together, our results suggest that while temperature may play a role in regulating seed removal by ants, ant plant seed-dispersal mutualisms may be more robust to climate change than currently assumed.

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Biotechnological approaches to develop nitrogen-fixing cereals: A review

Spanish Journal of Agricultural Research ◽

10.5424/sjar/2021194-18346 ◽

2021 ◽

Vol 19 (4) ◽

pp. e08R01-e08R01

Author(s):

Asma Boujenna ◽

Keyword(s):

Cereal Crops ◽

N Fixation ◽

N Availability ◽

Environmental Consequences ◽

Industrialized Nations ◽

Oxygen Sensitive ◽

Legume Symbiosis ◽

Living Organisms ◽

Agricultural Yields ◽

Biological Nitrogen

Agricultural yields are often limited by nitrogen (N) availability, especially in countries of the developing world, whereas in industrialized nations the application of chemical N fertilizers has reached unsustainable levels that have resulted in severe environmental consequences. Finding alternatives to inorganic fertilizers is critical for sustainable and secure food production. Although gaseous nitrogen (N2) is abundant in the atmosphere, it cannot be assimilated by most living organisms. Only a selected group of microorganisms termed diazotrophs, have evolved the ability to reduce N2 to generate NH3 in a process known as biological nitrogen fixation (BNF) catalysed by nitrogenase, an oxygen-sensitive enzyme complex. This ability presents an opportunity to improve the nutrition of crop plants, through the introduction into cereal crops of either the N fixing bacteria or the nitrogenase enzyme responsible for N fixation. This review explores three potential approaches to obtain N-fixing cereals: (a) engineering the nitrogenase enzyme to function in plant cells; (b) engineering the legume symbiosis into cereals; and (c) engineering cereals with the capability to associate with N-fixing bacteria.

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Effects of balsam poplar (Populus balsamifera) tannins and low molecular weight phenolics on microbial activity in taiga floodplain soil: implications for changes in N cycling during succession

Canadian Journal of Botany ◽

10.1139/b96-012 ◽

1996 ◽

Vol 74 (1) ◽

pp. 84-90 ◽

Cited By ~ 129

Author(s):

Joshua P. Schimel ◽

Keith Van Cleve ◽

Rex G. Cates ◽

Thomas P. Clausen ◽

Paul B. Reichardt

Keyword(s):

Molecular Weight ◽

Secondary Compounds ◽

N Cycling ◽

Low Molecular Weight ◽

N Fixation ◽

N Availability ◽

Populus Balsamifera ◽

Floodplain Soil ◽

Balsam Poplar ◽

River Floodplains

The transition from alder (Alnus tenuifolia) to balsam poplar (Populus balsamifera) is a critical turning point in primary succession on river floodplains in interior Alaska. Associated with the change in plant species are large changes in N cycling. N-fixation and nitrification decrease and the system becomes N-limited, with NH4+ dominating the inorganic N pool. Balsam poplar leaves contain large quantities of tannins and low molecular weight phenolic compounds. We evaluated the effect of these compounds on microbial respiration and N cycling in laboratory assays on soils from an alder-dominated site. Plant compounds were purified and applied to silica gel as an inert carrier. Both tannins and phenolics caused net N-immobilization over a 30-day assay. However, tannins inhibited respiration while phenolics stimulated it. There were no specific effects on nitrification. Thus, tannins acted as a general microbial inhibitor, while phenolics acted as a growth substrate. By inhibiting mineralization while stimulating immobilization, poplar secondary compounds may reduce soil N-availability during the transition betwen alder and poplar stages in succession. Keywords: respiration, mineralization, tannins, secondary chemicals, succession, plant–microbe interactions.

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