Progressive diebacks of outer canopy branchlets of Ceanothus crassifolius were repeatedly observed after rainless periods up to 9 mo in duration in the Santa Monica Mountains of southern California. Mean xylem pressures of branchlets near the end of drought were as low as 211.2 MPa (N 5 22) with a mean of about 60 dead branchlets per shrub. Inoculation (N 5 15) with three species of fungi previously isolated from the same population of C. crassifolius did not promote dieback, suggesting that the observed decline was not fungal induced, as had been proposed. Further, at least 50% of healthy-appearing twigs, without symptoms of dieback, contained isolatible endophytic fungi. We used a centrifugal force method to determine the range of xylem pressure causing cavitation (vulnerability curves) for branchlets (N 5 12) and roots (N 5 16). We combined vulnerability curves with soil texture data (N 5 6) into a water transport model that estimated the critical values ( PLcrit) of leaf xylem pressure associated with the loss of water from soil to foliage. Maximum PLcrit was between 210 and 211 MPa and within the range of minimum measured xylem pressures of branchlets during drought and dieback. Branchlet dieback correlated with seasonal declines in xylem pressure in concert with declining safety margins from hydraulic failure. Symptoms of dieback were duplicated in the field by partially severing stem xylem that normally supplied branchlets with water. Taken together, these results indicate that loss of hydraulic conductance to foliage was the probable cause of the observed dieback in C. crassifolius. Partial dieback of peripheral branchlets, and its attendant reduction in evaporative surface area, may be a last-resort mechanism for whole-plant water conservation and drought survival in this species.

Shoot dieback during prolonged drought in Ceanothus (Rhamnaceae) chaparral of California: a possible case of hydraulic failure

Large fires in chaparral-dominated shrublands of southern and central California are widely attributed to decades of fire suppression. Prehistoric shrubland landscapes are hypothesized to have exhibited fine-grained age-patch mosaics in which fire spread was limited by the age and spatial pattern of fuels. In contrast, I hypothesize that fires during extreme weather conditions have been capable of burning through all age classes of the vegetation mosaic. Using the mapped fire history (1911–1995) of Los Padres National Forest, I analyzed burning patterns for hundreds of fires using a geographic information system (GIS). To estimate the degree of age dependency exhibited by the fire regime at different spatial scales, I employed methods of fire frequency analysis (i.e., fitting a generalized Weibull function to fire interval distributions). Statistics were also calculated using a temporal breakpoint of 1950 to assess possible effects of suppression. Results indicated that shrubland fires have frequently bur...

Spatiotemporal analysis of controls on shrubland fire regimes: age dependency and fire hazard

Using long time series of Landsat data to monitor fire events and post-fire dynamics and identify driving factors. A case study in the Ayora region (eastern Spain)

Spatial distribution of forest fires in Sierra de Gredos (Central Spain)

In June 2017, wildfires burned 15 000 ha around the town of Knysna in the Western Cape, destroying > 800 buildings, > 5000 ha of forest plantations, and claiming the lives of seven people. We examined the factors that contributed to making this one of the worst fires on record in the region. One third of the area that burned was in natural vegetation (mainly fynbos shrublands), and more than half was in plantations of invasive alien (non-native) pine trees, or in natural vegetation invaded by alien trees. We used satellite imagery to assess burn severity in different land cover types by comparing pre- and post-fire images to estimate biomass consumed. We used daily weather data from two weather stations to calculate fire danger and drought indices over 70 years, and compared the fire weather conditions during the 2017 Knysna fires to the long-term weather record. The amount of biomass consumed was significantly higher in plantations of invasive alien trees, and in fynbos invaded by alien trees, than in uninvaded fynbos, providing support for the contention that invasion by alien trees increases the impact and difficulty of control of wildfires. Fire danger indices on the days of the fires were in the top 0.1 to 0.2% of days in the historic record, indicating that fire weather conditions were extreme but not unprecedented. The fires were preceded by a prolonged drought, and 18-month running means for two drought indices were the highest on record. The severity of the fires was exacerbated by very high fire danger conditions, preceded by an unprecedented drought, and further worsened by the conversion of natural fynbos vegetation to plantations, and invasion of vegetation by alien trees. Historical fire suppression also resulted in fuel buildups, further aggravating the problem of fire control, while residential development within and adjacent to fire-prone areas increased the risks faced by residents. Our results support calls to control invasive alien plants, reduce commercial planting of invasive alien trees, strictly regulate development in areas of high fire risk, and maintain awareness of the need for fire-wise practices.

/pdf/an-assessment-of-climate-weather-and-fuel-factors-33zgkyh1pg.pdf

An assessment of climate, weather, and fuel factors influencing a large, destructive wildfire in the Knysna region, South Africa

San Dimas Canyon seems a wild place beyond the reach of civilization. It is home to black bears, gray foxes, Anna’s hummingbirds, scrub jays, and in early summer, a multitude of biting insects. Along the steep, north-facing hillsides, the chaparral has the appearance of an ancient forest. From within the canyon it is difficult to remember that one is less than 7 km from metropolitan Los Angeles. It is also difficult to conceive of the landscape swept by flames 30- or 40-m high, or to visualize San Dimas Creek afterwards scoured by debris flows. Our difficulty in perceiving these catastrophic events makes it difficult to alter their course and consequences because to do so involves substantial cost and risks.

https://www.fs.fed.us/psw/publications/riggan/psw_1994_riggan002.pdf

Perspectives on Fire Management in Mediterranean Ecosystems of Southern California

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Fred E. Brooks

Author Tools

Chat about Author

Papers

Perspectives on Fire Management in Mediterranean Ecosystems of Southern California