Vegetation, fire, climate and human disturbance history in the southwestern Mediterranean area during the late Holocene

2013 ◽  
Vol 79 (2) ◽  
pp. 110-122 ◽  
Author(s):  
Gonzalo Jiménez-Moreno ◽  
Antonio García-Alix ◽  
María Dolores Hernández-Corbalán ◽  
R. Scott Anderson ◽  
Antonio Delgado-Huertas
Keyword(s):  
Sierra Nevada ◽  
Human Disturbance ◽  
Fire History ◽  
Mediterranean Area ◽  
Fuel Load ◽  
Lake Levels ◽  
Susceptibility Data ◽  
Lake Sediment Core ◽  
Oscillation Modes ◽  
Humid Period

AbstractDetailed pollen, charcoal, isotope and magnetic susceptibility data from an alpine lake sediment core from Sierra Nevada, southern Spain record changes in vegetation, fire history and lake sedimentation since ca. 4100 cal yr BP. The proxies studied record an arid period from ca. 3800 to 3100 cal yr BP characterized by more xerophytic vegetation and lower lake levels. A humid period is recorded between ca. 3100 and 1850 cal yr BP, which occurred in two steps: (1) an increase in evergreen Quercus between 3100 and 2500 cal yr BP, indicating milder conditions than previously and (2) an increase in deciduous Quercus and higher lake levels, between ca. 2500 and 1850 cal yr BP, indicating a further increase in humidity and reduction in seasonal contrast. Humid maxima occurred during the Roman Humid Period, previously identified in other studies in the Mediterranean region. Intensified fire activity at this time could be related to an increase in fuel load and/or in human disturbance. An arid period subsequently occurred between 1850 and 650 cal yr BP, though a decrease in Quercus and an increase in xerophytes. The alternation of persistent North Atlantic Oscillation modes probably played an important role in controlling these humid–arid cycles.

scholarly journals Fire History in California’s Southern Sierra Nevada Blue Oak Woodlands

Fire Ecology ◽  
2012 ◽  
Vol 8 (2) ◽  
pp. 163-167 ◽  
Author(s):  
Richard B. Standiford ◽  
Ralph L. Phillips ◽  
Neil K. McDougald
Keyword(s):  
Sierra Nevada ◽  
Fire History ◽  
Oak Woodlands ◽  
Blue Oak

Bare soil and rill formation following wildfires, fuel reduction treatments, and pine plantations in the southern Sierra Nevada, California, USA

2010 ◽  
Vol 19 (4) ◽  
pp. 478 ◽  
Author(s):  
Neil H. Berg ◽  
David L. Azuma
Keyword(s):  
Sierra Nevada ◽  
Vegetation Type ◽  
Fire Severity ◽  
Reference Conditions ◽  
Bare Soil ◽  
Fuel Load ◽  
Load Reduction ◽  
Fuel Reduction ◽  
Management Options ◽  
Burned Areas

Accelerated erosion commonly occurs after wildfires on forested lands. As burned areas recover, erosion returns towards prefire rates depending on many site-specific characteristics, including fire severity, vegetation type, soil type and climate. In some areas, erosion recovery can be rapid, particularly where revegetation is quick. Erosion recovery is less well understood for many fuel load reduction treatments. The rate of post-disturbance erosion recovery affects management options for forested lands, particularly when considering the combined ramifications of multiple disturbances on resource recovery rates (i.e. cumulative watershed effects). Measurements of percentage bare soil and rilling on over 600 plots in the southern Sierra Nevada with slopes less than 75% and within 1 km of roads were made between 2004 and 2006. Results suggest that after high-, moderate- or low-severity wildfire, rilling was seldom evident more than 4 years after fire. Percentage bare soil generally did not differ significantly between reference plots and wildfire plots greater than 6 years old. Little rilling was evident after treatment with a variety of fuel reduction techniques, including burning of machine- and hand-piled fuel, thinning, mastication, and crushing. Percentage bare soil at the fuel load reduction treatment plots also did not differ significantly from reference conditions. Percentage bare soil at pine plantation plots was noticeably higher than at reference sites.

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.

scholarly journals Socioecological transitions trigger fire regime shifts and modulate fire–climate interactions in the Sierra Nevada, USA, 1600–2015 CE

2016 ◽  
Vol 113 (48) ◽  
pp. 13684-13689 ◽  
Author(s):  
Alan H. Taylor ◽  
Valerie Trouet ◽  
Carl N. Skinner ◽  
Scott Stephens
Keyword(s):  
Climate Change ◽  
Native American ◽  
Sierra Nevada ◽  
Fire History ◽  
Climate Models ◽  
Fire Regime ◽  
Fire Suppression ◽  
Gold Rush ◽  
Climatic Effects ◽  
Fire Activity

Large wildfires in California cause significant socioecological impacts, and half of the federal funds for fire suppression are spent each year in California. Future fire activity is projected to increase with climate change, but predictions are uncertain because humans can modulate or even override climatic effects on fire activity. Here we test the hypothesis that changes in socioecological systems from the Native American to the current period drove shifts in fire activity and modulated fire–climate relationships in the Sierra Nevada. We developed a 415-y record (1600–2015 CE) of fire activity by merging a tree-ring–based record of Sierra Nevada fire history with a 20th-century record based on annual area burned. Large shifts in the fire record corresponded with socioecological change, and not climate change, and socioecological conditions amplified and buffered fire response to climate. Fire activity was highest and fire–climate relationships were strongest after Native American depopulation—following mission establishment (ca. 1775 CE)—reduced the self-limiting effect of Native American burns on fire spread. With the Gold Rush and Euro-American settlement (ca. 1865 CE), fire activity declined, and the strong multidecadal relationship between temperature and fire decayed and then disappeared after implementation of fire suppression (ca. 1904 CE). The amplification and buffering of fire–climate relationships by humans underscores the need for parameterizing thresholds of human- vs. climate-driven fire activity to improve the skill and value of fire–climate models for addressing the increasing fire risk in California.

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.

Late Quaternary Climate and Vegetation of the Sudanian Zone of Northeast Nigeria

2002 ◽  
Vol 58 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Ulrich Salzmann ◽  
Philipp Hoelzmann ◽  
Irena Morczinek
Keyword(s):  
Environmental History ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Lake Levels ◽  
The Holocene ◽  
Quaternary Climate ◽  
History Of ◽  
Sudanian Zone ◽  
Humid Period

AbstractThe Lake Tilla crater lake in northeastern Nigeria (10°23′N, 12°08′E) provides a ca. 17,000 14C yr multiproxy record of the environmental history of a Sudanian savanna in West Africa. Evaluation of pollen, diatoms, and sedimentary geochemistry from cores suggests that dry climatic conditions prevailed throughout the late Pleistocene. Before the onset of the Holocene, the slow rise in lake levels was interrupted by a distinct dry event between ca. 10,900 and 10,500 14C yr B.P., which may coincide with the Younger Dryas episode. The onset of the Holocene is marked by an abrupt increase in lake levels and a subsequent spread of Guinean and Sudanian tree taxa into the open grass savanna that predominated throughout the Late Pleistocene. The dominance of the mountain olive Olea hochstetteri suggests cool climatic conditions prior to ca. 8600 14C yr B.P. The early to mid-Holocene humid period culminated between ca. 8500 and 7000 14C yr B.P. with the establishment of a dense Guinean savanna during high lake levels. Frequent fires were important in promoting the open character of the vegetation. The palynological and palaeolimnological data demonstrate that the humid period terminated after ca. 7000 14C yr B.P. in a gradual decline of the precipitation/evaporation ratio and was not interrupted by abrupt climatic events. The aridification trend intensified after ca. 3800 14C yr B.P. and continued until the present.

A 740,000-yr-long Mohawk Lake record, Mohawk Valley, northeastern California, USA

2019 ◽  
Author(s):  
Joanna R. Redwine ◽  
Kenneth D. Adams
Keyword(s):  
Sierra Nevada ◽  
Lake Levels ◽  
Valley Bottom ◽  
Closed Basin ◽  
Mohawk Valley ◽  
Ice Cap ◽  
Lake History ◽  
Middle And Late Pleistocene ◽  
Tephra Beds ◽  
Lake Record

ABSTRACT Mohawk Valley lies in northeastern California on the margin of the northernmost Sierra Nevada and was occupied by Mohawk Lake during much of the middle and late Pleistocene. Throughout that time, the Sierra Nevada ice cap repeatedly extended northward into Mohawk Lake, and ice-contact deltaic sediments were deposited along the valley margins and in the valley bottom. Nearly 200 m of lacustrine and deltaic sediments are now well exposed along streams draining the Sierra Nevada. Tephra beds deposited within the deltaic sediments allow correlation of stratigraphic sections around the valley margin and, together with geomorphic evidence of former lake levels, permit interpretation of a Mohawk Lake history as far back as 740 ka. Mohawk Valley changed from a through-flowing fluvial setting to an intermittent closed basin sometime before 740 ka. After this change occurred, relatively small lakes intermittently formed in Mohawk Valley until ca. 600 ka, when the lake dramatically deepened. Mohawk Lake fluctuated in size over the next ~400,000 yr and increased in size to its highest levels after ca. 200 ka, possibly due to drainage integration with the upstream Lake Beckwourth. After this time, Mohawk Lake spilled over its westward sill, incrementally eroding and lowering lake levels until Mohawk Lake was emptied by ca. 7 ka.

scholarly journals APIFLAME v1.0: high resolution fire emission model and application to the Euro-Mediterranean region

2013 ◽  
Vol 6 (4) ◽  
pp. 5489-5551
Author(s):  
S. Turquety ◽  
L. Menut ◽  
B. Bessagnet ◽  
A. Anav ◽  
N. Viovy ◽  
...  
Keyword(s):  
High Resolution ◽  
Mediterranean Area ◽  
Emission Factors ◽  
Fuel Load ◽  
Burned Area ◽  
Emission Model ◽  
Fire Emissions ◽  
The Mediterranean ◽  
The Impact ◽  
Horizontal Grid

Abstract. This paper describes a new model for the calculation of daily, high-resolution (up to 1 km) fire emissions, developed in the framework of the APIFLAME project (Analysis and Prediction of the Impact of Fires on Air quality ModEling). The methodology relies on the classical approach, multiplying the burned area by the fuel load and the emission factors specific to the vegetation burned. Emissions can be calculated on any user-specified domain, horizontal grid, and list of trace gases and aerosols, providing input information on the burned area (location, extent) and emission factors of the targeted species are available. The strength of the proposed algorithm is its high resolution and its flexibility in terms of domain and input data (including the vegetation classification). The modification of the default values and databases proposed does not require changes in the core of the model. The code may be used for the calculation of global or regional inventories. However, it has been developed and tested more specifically for Europe and the Mediterranean area. In this region, the burning season extends from June to October in most regions, with generally small but frequent fires in Eastern Europe, Western Russia, Ukraine and Turkey, and large events in the Mediterranean area. The resulting emissions represents a significant fraction of the total yearly emissions (on average amounting to ~30% of anthropogenic emissions for PM2.5, ~20% for CO). The uncertainty on the daily carbon emissions was estimated to ~100% based on an ensemble analysis. Considering the large uncertainties on emission factors, the potential error on the emissions for the various pollutants is even larger. Comparisons to other widely used emission inventories shows good correlations but discrepancies of a factor of 2–4 on the amplitude of the emissions, our results being generally on the higher end.

Relating fuel loads to overstorey structure and composition in a fire-excluded Sierra Nevada mixed conifer forest

2015 ◽  
Vol 24 (4) ◽  
pp. 484 ◽  
Author(s):  
Jamie M. Lydersen ◽  
Brandon M. Collins ◽  
Eric E. Knapp ◽  
Gary B. Roller ◽  
Scott Stephens
Keyword(s):  
Sierra Nevada ◽  
Predictive Models ◽  
Vegetation Type ◽  
Fuel Load ◽  
Small Scale ◽  
Conifer Forest ◽  
Fire Behaviour ◽  
Mixed Conifer ◽  
Fuel Loads ◽  
Mixed Conifer Forest

Although knowledge of surface fuel loads is critical for evaluating potential fire behaviour and effects, their inherent variability makes these difficult to quantify. Several studies relate fuel loads to vegetation type, topography and spectral imaging, but little work has been done examining relationships between forest overstorey variables and surface fuel characteristics on a small scale (<0.05 ha). Within-stand differences in structure and composition would be expected to influence fuel bed characteristics, and thus affect fire behaviour and effects. We used intensive tree and fuel measurements in a fire-excluded Sierra Nevada mixed conifer forest to assess relationships and build predictive models for loads of duff, litter and four size classes of downed woody fuels to overstorey structure and composition. Overstorey variables explained a significant but somewhat small percentage of variation in fuel load, with marginal R2 values for predictive models ranging from 0.16 to 0.29. Canopy cover was a relatively important predictor for all fuel components, although relationships varied with tree species. White fir abundance had a positive relationship with total fine woody fuel load. Greater pine abundance was associated with lower load of fine woody fuels and greater load of litter. Duff load was positively associated with total basal area and negatively associated with oak abundance. Knowledge of relationships contributing to within-stand variation in fuel loads can increase our understanding of fuel accumulation and improve our ability to anticipate fine-scale variability in fire behaviour and effects in heterogeneous mixed species stands.

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