New paper: Guidelines for the use and interpretation of palaeofire reconstructions based on various archives and proxies

I am pleased to share this recent article by Cecile Remy and colleagues on the comparison of charcoal records using various archives:

Remy C. C., Fouquemberg C., Asselin H., Andrieux B., Magnan G., Brossier B., Grondin P., Bergeron Y., Talon B., Girardin M. P., Blarquez O., Bajolle L., Ali A. A. (2018). Guidelines for the use and interpretation of palaeofire reconstructions based on various archives and proxies. Quaternary Science Reviews, 193, 312-322.  https://doi.org/10.1016/j.quascirev.2018.06.010 

Abstract

We present a comparative analysis of fire reconstructions from tree rings and from wood charcoal preserved in forest soils, peat and lake sediments. Our objective is to highlight the benefits and limits of different archives and proxies to reconstruct fire histories. We propose guidelines to optimize proxy and archive choice in terms of spatial and temporal scales of interest. Comparisons were performed for two sites in the boreal forest of northeastern North America. Compared to others archives, tree-ring analysis remains the best choice to reconstruct recent fires (<1000 years). For longer periods (from several centuries to millennia), lake charcoal can be used to reconstruct regional or local fire histories depending on the method used, but the focus should be on historical trends rather than on the identification of individual fire events. Charcoal preserved in peat and soils can be used to identify individual fire, but sometimes cover shorter time periods than lake archives.

 

 

GCD 4.0.2 and paleofire 1.2.2

We are please to announce that the GCD and paleofire R packages have been updated to their 4.0.2 and 1.2.2 versions, respectively. GCD major update from 3.X.X to 4.X.X version number is associated to extensive changes in the way data is added into the package. GCD 4.X.X is now mirroring the online GCD SQL database on a monthly basis or whenever a significant number of new charcoal sites are added to the database.

Three new fields in the paleofiresites table (see ?paleofiresites for details) enable to perform analyses with specific database versions or enable to select sites according to the date at which they have been added into the database. See the quick example below for explanations:

par(mfrow=c(2,2))
plot( pfSiteSel(num_version &amp;lt; 400 ) ) # All sites in GCD version before 4.0.0
plot( pfSiteSel(gcd_version == "GCD1" ) ) # All sites in GCDv1
plot( pfSiteSel(update_date &amp;lt; "2016-01-01" ) ) # Sites included before 2016-01-01
plot( pfSiteSel(update_date &amp;gt; "2018-01-01" ) ) # Sites included since 2018-01-01&lt;/code&gt;

The map above that is used to display all GCD charcoal sites has been produced by adapting the code available at https://seethedatablog.wordpress.com/2016/12/23/r-simple-world-map-robinson-ggplot/ please follow that link for additional references and explanations. The modified code is copied below:

# ======================================================================================
# Create a simple world map in Robinson projection with labeled graticules using ggplot
# ======================================================================================

# Set a working directory with setwd() or work with an RStudio project

# __________ Set libraries
library(rgdal) # for spTransform() &amp;amp; project()
library(ggplot2) # for ggplot()
library(paleofire) #

setwd("somewhere...")

# __________ Load ready to use data from GitHub
load(url("https://github.com/valentinitnelav/RandomScripts/blob/master/NaturalEarth.RData?raw=true"))
# This will load 6 objects:
# xbl.X &amp;amp; lbl.Y are two data.frames that contain labels for graticule lines
# They can be created with the code at this link:
# https://gist.github.com/valentinitnelav/8992f09b4c7e206d39d00e813d2bddb1
# NE_box is a SpatialPolygonsDataFrame object and represents a bounding box for Earth
# NE_countries is a SpatialPolygonsDataFrame object representing countries
# NE_graticules is a SpatialLinesDataFrame object that represents 10 dg latitude lines and 20 dg longitude lines
# (for creating graticules check also the graticule package or gridlines fun. from sp package)
# (or check this gist: https://gist.github.com/valentinitnelav/a7871128d58097e9d227f7a04e00134f)
# NE_places - SpatialPointsDataFrame with city and town points
# NOTE: data downloaded from http://www.naturalearthdata.com/
# here is a sample script how to download, unzip and read such shapefiles:
# https://gist.github.com/valentinitnelav/a415f3fbfd90f72ea06b5411fb16df16

# __________ Project from long-lat (unprojected data) to Robinson projection
# spTransform() is used for shapefiles and project() in the case of data frames
# for more PROJ.4 strings check the followings
# http://proj4.org/projections/index.html
# https://epsg.io/

PROJ &amp;lt;- "+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
# or use the short form "+proj=robin"
NE_countries_rob &amp;lt;- spTransform(NE_countries, CRSobj = PROJ)
NE_graticules_rob &amp;lt;- spTransform(NE_graticules, CRSobj = PROJ)
NE_box_rob &amp;lt;- spTransform(NE_box, CRSobj = PROJ)

# Add lakes http://www.naturalearthdata.com/http//www.naturalearthdata.com/download/10m/physical/ne_10m_lakes.zip

download.file("http://www.naturalearthdata.com/http//www.naturalearthdata.com/download/10m/physical/ne_10m_lakes.zip", destfile="ne_10m_lakes.zip")
unzip("ne_10m_lakes.zip")
NE_lakes &amp;lt;- readOGR('ne_10m_lakes.shp',
'ne_10m_lakes')
NE_lakes &amp;lt;- spTransform(NE_lakes, CRSobj = PROJ)
NE_lakes &amp;lt;- NE_lakes[NE_lakes@data$scalerank==0,]

# project long-lat coordinates for graticule label data frames
# (two extra columns with projected XY are created)
prj.coord &amp;lt;- project(cbind(lbl.Y$lon, lbl.Y$lat), proj=PROJ)
lbl.Y.prj &amp;lt;- cbind(prj.coord, lbl.Y)
names(lbl.Y.prj)[1:2] &amp;lt;- c("X.prj","Y.prj")

prj.coord &amp;lt;- project(cbind(lbl.X$lon, lbl.X$lat), proj=PROJ)
lbl.X.prj &amp;lt;- cbind(prj.coord, lbl.X)
names(lbl.X.prj)[1:2] &amp;lt;- c("X.prj","Y.prj")

# Project GCD sites

gcd_rob=project(cbind(paleofiresites$long,paleofiresites$lat),PROJ)
gcd=data.frame(long=gcd_rob[,1],lat=gcd_rob[,2],GCD_version=paleofiresites$gcd_version)

# __________ Plot layers
ggplot() +
# add Natural Earth countries projected to Robinson, give black border and fill with gray
geom_polygon(data=NE_box_rob, aes(x=long, y=lat), colour="black", fill="grey90", size = 0.25) +
geom_polygon(data=NE_countries_rob, aes(long,lat, group=group), colour="black", fill="white", size = 0.25) +
geom_polygon(data=NE_lakes, aes(long,lat, group=group), colour="black", fill="white", size = 0.25) +
# Note: "Regions defined for each Polygons" warning has to do with fortify transformation. Might get deprecated in future!
# alternatively, use use map_data(NE_countries) to transform to data frame and then use project() to change to desired projection.
# add Natural Earth box projected to Robinson
geom_polygon(data=NE_box_rob, aes(x=long, y=lat), colour="black", fill="transparent", size = 0.25) +
# add graticules projected to Robinson
geom_path(data=NE_graticules_rob, aes(long, lat, group=group), linetype="dotted", color="grey50", size = 0.25) +
# add graticule labels - latitude and longitude
geom_text(data = lbl.Y.prj, aes(x = X.prj, y = Y.prj, label = lbl), color="grey50", size=2) +
geom_text(data = lbl.X.prj, aes(x = X.prj, y = Y.prj, label = lbl), color="grey50", size=2) +
# the default, ratio = 1 in coord_fixed ensures that one unit on the x-axis is the same length as one unit on the y-axis
geom_point(data=gcd, aes(long,lat, col= GCD_version),pch=2)+
coord_fixed(ratio = 1) +
# remove the background and default gridlines
theme_void()+
theme(legend.title = element_text(colour="black", size=8, face="bold"), # adjust legend title
legend.position = c(0.1, 0.2), # relative position of legend
plot.margin = unit(c(t=0, r=0, b=0, l=0), unit="cm"),
legend.background = element_rect(fill="white",
size=0.5, linetype="solid",
colour ="black")) # adjust margins

# save to pdf and png file
ggsave("map_draft_1.pdf", width=28, height=13.5, units="cm")
ggsave("map_1.png", width=26, height=13.5, units="cm", dpi=300)

# REFERENCES:
# This link was useful for graticule idea
# http://stackoverflow.com/questions/38532070/how-to-add-lines-of-longitude-and-latitude-on-a-map-using-ggplot2
# Working with shapefiles, projections and world maps in ggplot
# http://rpsychologist.com/working-with-shapefiles-projections-and-world-maps-in-ggplot

WORKSHOP REPORT: Applying paleofire records in ecological management

We are very glad to share the last report from the GPWG2 Montreal Workshop that is now published in Wildfire Magazine.

WORKSHOP REPORT: Applying paleofire records in ecological management, by: Kendrick J. Brown – Natural Resources Canada, Mitchell J. Power – University of Utah, Michal Słowiński – Polish Academy of Sciences, Andri C. Van Aardt – University of the Free State, Olivier Blarquez – Université de Montréal, Pierre Grondin – Ministère de la Forêt, de la Faune et des Parcs.

You can read the workshop report below or directly on Wildfire Magazine Here.

Perspective: Sparking New Opportunities for Charcoal-Based Fire History Reconstructions

Very happy to share our new paper published as a perspective in Fire. This perspective is a product of our last GPWG2 workshop held in Montréal last October. I wish to thank all the workshop participants and PAGES and UdeM for financial support!

Aleman J. C., Hennebelle A., Vannière B., Blarquez O. and the Global Paleofire Working Group. 2018. Sparking New Opportunities for Charcoal-Based Fire History Reconstructions. Fire. 1(1), 7. doi:10.3390/fire1010007 

You can freely access the paper here: http://www.mdpi.com/2571-6255/1/1/7/htm

 

 

New paper: Late Holocene influence of societies on the fire regime in southern Québec temperate forests

I am really happy to share our last paper published in Quaternary Science Reviews with students and colleagues from the Department of Geography and Anthropology of UdeM:

Blarquez O., Talbot J., Paillard J., Lapointe-Elmrabti L., Pelletier N., Gates St-Pierre C. 2018. Late Holocene influence of societies on the fire regime in southern Québec temperate forests. Quaternary Science Reviews 180: 63–74. doi:10.1016/j.quascirev.2017.11.022  

Data will follow soon… 

Abstract: Climatic change that occurred during the Holocene is often recognized as the main factor for explaining fire dynamics, while the influence of human societies is less apparent. In eastern North America, human influence on fire regime before European settlement has been debated, mainly because of a paucity of sites and paleoecological techniques that can distinguish human influences unequivocally from climate. We applied a multiproxy analysis to a 12 000-year-old paleoecological sequence from a site in the vicinity of known settlement areas that were occupied over more than 7000 years. From this analysis, we were able detect the human influence on the fire regime before and after European colonization. Fire occurrence and fire return intervals (FRI) were based on analysis of sedimentary charcoals at a high temporal and spatial resolution. Fire occurrence was then compared to vegetation that was reconstructed from pollen analysis, from population densities deduced from archeological site dating, from demographic and technological models, and from climate reconstructed using general circulation models and ice-core isotopes. Holocene mean FRI was short (164 ± 134 years) and associated with small charcoal peaks that were likely indicative of surface fires affecting small areas. After 1500 BP, large vegetation changes and human demographic growth that was demonstrated through increased settlement evidence likely caused the observed FRI lengthening (301 ± 201 years), which occurred without significant changes in climate. Permanent settlement by Europeans in the area around 1800 AD was followed by a substantial demographic increase, leading to the establishment of Gatineau, Hull and Ottawa. This trend was accompanied by a shift in the charcoal record toward anthropogenic particles that were reflective of fossil fuel burning and an apparent absence of wood charcoal that would be indicative of complete fire suppression. An anthropogenic fire regime that was characterized by severe and large fires and long fire-return intervals occurred more than 1000 years ago, concomitant with the spread of native agriculture, which intensified with European colonization over the past two centuries.

Winter is coming

Notre dernière étude publiée dans New Phytologist fait la couverture du journal!

Le blog du journal nous fait également l’honneur d’un article par Mike Whitfield que vous trouverez ici: https://www.newphytologist.org/blog/behind-the-cover-new-phytologist-2164-december-2017/ 

Et repris ci dessous:

Winter has come to Lake Miroir. Below the surface, deep down in the dark, the lakebed sediments tell a story of ice and fire.

These days, snow covers the landscape from December to April, but this hasn’t always been the case. This lake contains sediments from the last glaciation, which ended about 15,000 years ago in the Alps. Interestingly these sediments contain proof of a glacial refugia of trees: cembra pines and larch. Trees survived the deep glacial winter here in isolation.

The snowy scene on the cover of New Phytologist 216:4 represents a site that contains proof of an extraordinary interplay between fire and vegetation in a periglacial environment. Christopher Carcaillet and Olivier Blarquez studied lake sediments nine metres below the surface. In their New Phytologistpaper, they describe how they discovered evidence of fire amid the ice. This refuge burned, with a very low frequency of about one fire per 1000 years. This is the first evidence of fire at such high altitude during glacial times, which were cold and dry.

Image: Lake Miroir, western Alps, France.
Lake Miroir, western Alps, France. Courtesy of Christopher Carcaillet.

Today, fire is about three times more frequent, with one fire every 300 years or so. The vegetation is naturally dominated by larch with cembra pines. While larch abound today, during glacial times the cembra pines were dominant. Carcaillet and Blarquez observed that when the vegetation switched from pine dominant to larch dominant, fires became more frequent. These results suggest that vegetation and fire interact, fire controlling the abundance of larch over cembra pine.

Christopher Carcaillet’s research focuses on determining the long-term relative influences of climate and social processes on the pattern of plant communities (e.g. biodiversity) or ecosystem dynamics through changes in disturbance regimes (such as fire, snow avalanche, or insect outbreak). Seeking similar evidence to that found at Lake Miroir, the researchers investigated a similar lake in the same region. While it also contains glacial sediments, it provides no evidence of trees nor of fire. This comparison shows that glacial climate does not prevent the occurrence of fires, but suggests that trees are needed to allow fires to ignite and spread.

Carcaillet and Blarquez’s research suggests that trees may have survived the long glacial winter in Europe in more places than previously thought. Despite finding refuge from the ice, however, they may not have been safe from fire.

Mike Whitfield
Development Coordinator
New Phytologist

Read the paper: Carcaillet, C. and Blarquez, O. (2017) Fire ecology of a tree glacial refugium on a nunatak with a view on Alpine glaciers. New Phytologist. doi: 10.1111/nph.14721

 

Pyrogéographie Vol. 1 !

Je suis heureux d’annoncer la parution du numéro 1 du journal Pyrogéographie qui est réalisé par les étudiants du cours GEO6139 durant la session d’hiver 2017. Vous trouverez trois articles traitant de la géographie des feux que ce soit de dynamiques écologiques en tundra (Dessain et El Ghoneimi) de la place de l’homme au sein de la Pyrosphère (Paillard) ou encore de l’importance des feux dans un contexte de gestion des écosystèmes (Perrault-Hébert et Negash).

Le journal est librement accessible sous licence creative commons ici :

Les articles:

Dessain A. et R. El Ghoneimi. 2017. Réponse écosystémique aux feux dans les écosystèmes de toundra Pyrogéographie 1: 3-8

Paillard J. 2017. L’Homme au sein de la pyrosphère : de la préhistoire à aujourd’hui. Pyrogéographie 1: 9-15

Perrault-Hébert M. et Y. Negash. 2017. Fire behaviours at different scales: Implication for forest management. Pyrogéographie 1: 16-22

Our paper on African land-use change recommended in F1000Prime as being of special significance in its field!

Our paper “Land-use change outweighs projected effects of changing rainfall on tree cover in sub-Saharan Africa”  , has been recommended in F1000Prime as being of special significance in its field by F1000 Faculty Member George Malanson! Pr. Malanson summary:

Aleman et al. identified landscapes at risk in sub-Saharan Africa. A variety of data sources (satellite tree cover, climatic, soils, population density, and land use) are nicely combined in a statistical model (random forest) to identify the relative importance of variables. Future scenarios were developed and the random forest model re-used to predict future tree cover. Land use change was identified as a greater threat than climate change. Risk is assessed in terms of loss of tree cover and areas likely to be protected. Depending on scenario, projected loss of tree cover was high in both savanna and forest biomes, but tree cover increases could reduce the area of savanna. The highest risk is in an area south of the Sahel and with a connection to much of the Congo Basin. Given the role of land use, the conversion of savanna to biofuels to mitigate climate change is questioned. The paper could be used as an example for complementary analyses in other places. The focus on biome transitions (forest-savanna-grassland) in the context of land use highlights the importance of landscape level analyses. The action is at the edges.

New paper: Paleofire Dynamics in Central Spain During the Late Holocene: the Role of Climatic and Anthropogenic Forcing

I am very pleased to share this new article with José Antonio López-Sáez and colleagues: DOI:10.1002/ldr.2751 about the fire history of a mountain range in central Spain.  

Abstract:

The use of fire and, consequently, its severity and incidence on the environment, has grown steadily during the last millennia throughout the Mediterranean. This issue can be assessed in several mountain ranges of central Iberia where changes in the management policy on anthropic activities and exploitation of high-mountain environments have promoted a remarkable increase on fire frequency. Our research focuses on fire dynamics throughout the last three thousand years from three peat bog charcoal records of the Gredos range (central Iberia). Our aim is to reconstruct past fire regimes according to forest vegetation typology (Castanea sativa, Pinus pinaster, P. sylvestris). Charcoal influx shows low values between 3140 and 1800 cal. yr BP when forests were relatively dense both in high and mid-mountain areas. Fire appeared synchronous between 1800 and 1700 cal. yr BP for Lanzahíta and Serranillos and around 1400-1240 cal. yr BP for the three sites suggesting anthropogenic fire control between the Late Roman and the Visigothic periods that can be related to the cultivation of olive trees in the valleys and a greater human impact in high-mountain areas. By contrast, during the Muslim period (1240-850 cal. yr BP) fire dynamics becomes asynchronous. Later, fires turn again coeval in the Gredos range during the Christian period (850-500 cal. yr BP) and can be also correlated with drought phases during the Late Medieval Warm Episode. In short, our study demonstrates that fire activity has been enormously variable during the late Holocene in response to both short- and long-term regional and global climate, vegetation dynamics and land use changes.