Changes in functional traits of the terricolous lichen Peltigera aphthosa across a retrogressive boreal forest chronosequence

2015 ◽  
Vol 47 (3) ◽  
pp. 187-195 ◽  
Author(s):  
Johan Asplund ◽  
David A. Wardle
Keyword(s):  
Functional Traits ◽  
Fire History ◽  
Secondary Compounds ◽  
Cortical Layer ◽  
N Availability ◽  
Epiphytic Lichen ◽  
In Fire ◽  
Water Holding ◽  
Terricolous Lichen ◽  
Soil Ageing

AbstractChanges in the functional traits of the terricolous lichen Peltigera aphthosa with declining soil fertility during ecosystem retrogression were investigated. A well-documented retrogressive chronosequence of 28 forested islands in northern Sweden that differ greatly in fire history and which spans 5000 years was used. The abundance of cephalodia increased, indicative of higher N2-fixation rates resulting from lower N availability. Thallus δ13C values increased with ageing soils, in line with declining δ13C values of the humus substratum along this gradient. However, δ13C values were also driven by variation in factors that were at least partly independent of soil ageing. As such, δ13C values were mostly related to specific thallus mass (STM), possibly because a higher STM gives a thicker cortical layer and thus greater resistance to CO2 diffusion, leading to higher δ13C values. STM and other measured traits (i.e. thallus N, P, secondary compounds and water-holding capacity) were unresponsive to the gradient, despite these traits being very responsive to the same gradient in epiphytic lichen species.

Fire regime shift linked to increased forest density in a piñon–juniper savanna landscape

2014 ◽  
Vol 23 (2) ◽  
pp. 234 ◽  
Author(s):  
Ellis Q. Margolis
Keyword(s):  
Regime Shift ◽  
Fire History ◽  
Fire Regime ◽  
Fire Regimes ◽  
Fire Frequency ◽  
Climatic Conditions ◽  
Tree Density ◽  
High Severity ◽  
Wide Range ◽  
In Fire

Piñon–juniper (PJ) fire regimes are generally characterised as infrequent high-severity. However, PJ ecosystems vary across a large geographic and bio-climatic range and little is known about one of the principal PJ functional types, PJ savannas. It is logical that (1) grass in PJ savannas could support frequent, low-severity fire and (2) exclusion of frequent fire could explain increased tree density in PJ savannas. To assess these hypotheses I used dendroecological methods to reconstruct fire history and forest structure in a PJ-dominated savanna. Evidence of high-severity fire was not observed. From 112 fire-scarred trees I reconstructed 87 fire years (1547–1899). Mean fire interval was 7.8 years for fires recorded at ≥2 sites. Tree establishment was negatively correlated with fire frequency (r=–0.74) and peak PJ establishment was synchronous with dry (unfavourable) conditions and a regime shift (decline) in fire frequency in the late 1800s. The collapse of the grass-fuelled, frequent, surface fire regime in this PJ savanna was likely the primary driver of current high tree density (mean=881treesha–1) that is >600% of the historical estimate. Variability in bio-climatic conditions likely drive variability in fire regimes across the wide range of PJ ecosystems.

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

1996 ◽  
Vol 74 (1) ◽  
pp. 84-90 ◽  
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.

The gastropod Arion fuscus prefers cyanobacterial to green algal parts of the tripartite lichen Nephroma arcticum due to low chemical defence

2009 ◽  
Vol 42 (1) ◽  
pp. 113-117 ◽  
Author(s):  
Johan ASPLUND ◽  
Yngvar GAUSLAA
Keyword(s):  
Usnic Acid ◽  
Chemical Defence ◽  
Secondary Compounds ◽  
Distribution Limit ◽  
Green Algal ◽  
Defensive Role ◽  
N Starvation ◽  
And Control ◽  
Terricolous Lichen ◽  
Acetone Rinsing

AbstractAlthough the tripartite terricolous lichen Nephroma arcticum is easily accessible to lichen-feeding gastropods, grazing marks are mainly restricted to localized cephalodia with N-fixing Nostoc. We tested if this gastropod preference for cephalodia can be explained by differences in carbon based secondary compounds (CBSCs) in cyanobacterial versus green-algal tissues. CBSCs were non-destructively removed from air-dry thalli by 100% acetone. Compound deficient and control thallus parts were offered to the slug Arion fuscus and grazing preferences were quantified by area measurements in ArcGIS™. The concentrations of CBSCs (phenarctin, usnic acid, nephroarctin and methyl gyrophorate) in thallus parts with and without cephalodia were quantified with HPLC. Compared to purely green-algal parts, cephalodial parts with adjoining fungal tissues contained less defensive compounds, and were preferred by A. fuscus. The cephalodia themselves do not contain any CBSCs. After acetone rinsing, A. fuscus did not discriminate between green-algal and cyanobacterial parts. The results were consistent with the hypothesis that CBSCs in green-algal parts of N. arcticum play a herbivore-defensive role. It is further hypothesized that grazing of cephalodia may lead to N-starvation and reduced growth of N. arcticum thalli in southern portions of its range where lichenivorous gastropods are more abundant. This may play a role in shaping the southern distribution limit of this arctic-boreal lichen species.

scholarly journals The effects of vegetative type, edges, fire history, rainfall, and management in fire-maintained habitat

Ecosphere ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. e02120 ◽  
Author(s):  
David R. Breininger ◽  
Tammy E. Foster ◽  
Geoffrey M. Carter ◽  
Brean W. Duncan ◽  
Eric D. Stolen ◽  
...  
Keyword(s):  
Fire History ◽  
In Fire

Long-term fire history from alluvial fan sediments: the role of drought and climate variability, and implications for management of Rocky Mountain forests

2008 ◽  
Vol 17 (1) ◽  
pp. 84 ◽  
Author(s):  
Jennifer Pierce ◽  
Grant Meyer
Keyword(s):  
Ponderosa Pine ◽  
Fire History ◽  
Fire Regimes ◽  
Alluvial Fan ◽  
Ice Age ◽  
Pine Forests ◽  
Drought Severity ◽  
Ponderosa Pine Forests ◽  
Grass Growth ◽  
In Fire

Alluvial fan deposits are widespread and preserve millennial-length records of fire. We used these records to examine changes in fire regimes over the last 2000 years in Yellowstone National Park mixed-conifer forests and drier central Idaho ponderosa pine forests. In Idaho, frequent, small, fire-related erosional events occurred within the Little Ice Age (~1450–1800 AD), when greater effective moisture probably promoted grass growth and low-severity fires. This regime is consistent with tree-ring records showing generally wetter conditions and frequent fires before European settlement. At higher elevations in Yellowstone, cool conditions limited overall fire activity. Conversely, both Idaho and Yellowstone experienced a peak in fire-related debris flows between ~950 and 1150 AD. During this generally warmer time, severe multidecadal droughts were interspersed with unusually wet intervals that probably increased forest densities, producing stand-replacing fires. Thus, severe fires are clearly within the natural range of variability in Idaho ponderosa pine forests over longer timescales. Historical records indicate that large burn areas in Idaho correspond with drought intervals within the past 100 years and that burn area has increased markedly since ~1985. Recent stand-replacing fires in ponderosa pine forests are likely related to both changes in management and increasing temperatures and drought severity during the 20th century.

scholarly journals Variation in fire scar phenology from mixed conifer trees in the Sierra Nevada

2018 ◽  
Vol 48 (1) ◽  
pp. 101-104 ◽  
Author(s):  
Scott L. Stephens ◽  
Liam Maier ◽  
Lilah Gonen ◽  
Jennifer D. York ◽  
Brandon M. Collins ◽  
...  
Keyword(s):  
Sierra Nevada ◽  
Fire History ◽  
Fire Regimes ◽  
Fire Season ◽  
Mixed Conifer ◽  
Outer Bark ◽  
Individual Tree ◽  
Fire Scar ◽  
The Individual ◽  
In Fire

Fire scar based studies have provided robust reconstructions of past fire regimes. The season in which a fire occurs can have considerable impacts to ecosystems but inference on seasonality from fire scars is relatively uncertain. This study examined patterns in the phenology of cambium formation and wounding responses in the five common mixed conifer tree species of the Sierra Nevada. The outer bark was shaved on 35 trees and individual locations within the shaved portions were wounded systematically by applying direct heat using a handheld torch. Most of the trees had not commenced annual ring development by the first burning treatment in late May. By the second treatment, scars were identified mostly within the early or middle earlywood, although variation was high compared with other treatment periods. By late October, all scars were recorded at the ring boundary. Although intra-ring scar positions generally followed a logical temporal pattern, there was high tree to tree variation such as Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) burned on 26 June induced scars in the early, mid, and late earlywood depending on the individual tree. This high variation makes it somewhat challenging to precisely assign past fire season to published fire history studies.

Fire history and age structure in red fir forests of Sequoia National Park, California

1987 ◽  
Vol 17 (7) ◽  
pp. 582-587 ◽  
Author(s):  
Donald C. Pitcher
Keyword(s):  
Age Structure ◽  
National Park ◽  
Fire History ◽  
Fire Behavior ◽  
White Pine ◽  
Sequoia National Park ◽  
Fire Scar ◽  
Forest Age Structure ◽  
Negative Exponential ◽  
In Fire

The relationship between historical fires and age structure was examined on three plots in red fir (Abiesmagnifica var. shastensis Lemm.) forests within Sequoia National Park, California, U.S.A. All trees greater than 0.1 m in height were mapped and aged. Fire history was determined from 16 fire-scar sections. Red fir trees are more shade tolerant, longer lived, larger, and slower growing than western white pine (Pinusmonticola Dougl.) on the plots. No fires have occurred since 1886, but prior to that time the average fire-free interval was 65 years. Most of the trees on two of the plots originated after fires, but on the third plot red fir regeneration was delayed for at least 60 years following the last fire. Structural differences between the plots were linked to variations in fire behavior. The decrease in fire frequencies in this century may have led to a decrease in red fir establishment. Excluding the most recent period, the forest age structure is in something of a steady state that approximates a negative exponential age-class distribution.

Improving estimates of savanna burning emissions for greenhouse accounting in northern Australia: limitations, challenges, applications

2009 ◽  
Vol 18 (1) ◽  
pp. 1 ◽  
Author(s):  
Jeremy Russell-Smith ◽  
Brett P. Murphy ◽  
C. P. (Mick) Meyer ◽  
Garry D. Cook ◽  
Stefan Maier ◽  
...  
Keyword(s):  
Greenhouse Gas ◽  
Fire History ◽  
Fire Management ◽  
Combustion Efficiency ◽  
Management Program ◽  
Anthropogenic Sources ◽  
Fuel Load ◽  
Northern Australia ◽  
Savanna Burning ◽  
In Fire

Although biomass burning of savannas is recognised as a major global source of greenhouse gas emissions, quantification remains problematic with resulting regional emissions estimates often differing markedly. Here we undertake a critical assessment of Australia’s National Greenhouse Gas Inventory (NGGI) savanna burning emissions methodology. We describe the methodology developed for, and results and associated uncertainties derived from, a landscape-scale emissions abatement project in fire-prone western Arnhem Land, northern Australia. The methodology incorporates (i) detailed fire history and vegetation structure and fuels type mapping derived from satellite imagery; (ii) field-based assessments of fuel load accumulation, burning efficiencies (patchiness, combustion efficiency, ash retention) and N : C composition; and (iii) application of standard, regionally derived emission factors. Importantly, this refined methodology differs from the NGGI by incorporation of fire seasonality and severity components, and substantial improvements in baseline data. We consider how the application of a fire management program aimed at shifting the seasonality of burning (from one currently dominated by extensive late dry season wildfires to one where strategic fire management is undertaken earlier in the year) can provide significant project-based emissions abatement. The approach has wider application to fire-prone savanna systems dominated by anthropogenic sources of ignition.

Refuges for birds in fire-prone landscapes: The influence of fire severity and fire history on the distribution of forest birds

2014 ◽  
Vol 318 ◽  
pp. 110-121 ◽  
Author(s):  
Natasha M. Robinson ◽  
Steven W.J. Leonard ◽  
Andrew F. Bennett ◽  
Michael F. Clarke
Keyword(s):  
Fire History ◽  
Fire Severity ◽  
Forest Birds ◽  
In Fire
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