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Impact of targeted sheep grazing on herbage and holm oak saplings in a silvopastoral wildfire system in south-eastern Spain

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Several wildfire prevention programs in southern Europe are currently using livestock grazing for the maintenance of fuelbreaks. This silvopastoral management is valued for being sustainable and effective in reducing fuel loads, but few studies have analyzed other impacts linked to fuelbreak grazing. This paper reports on an experiment performed within the wildfire prevention program in Andalusia (southern Spain) with the aim of clarifying and quantifying the effect of fuelbreak grazing on herbage biomass, ground cover, herbage species composition, and growth of holm oak saplings. The study site, located in a semiarid Mediterranean environment, was grazed by a shepherded sheep flock from February to June in three consecutive years at a similar stocking rate. Livestock consumed between 33 and 68 % of herbage production in the different years, and the greatest fuel reduction (remaining dry matter of 200 kg ha−1) was registered in Year 2, when rainfall and herbage production was lowest. Ground cover was significantly affected by grazing: on average, the percentage of bare soil increased three-fold, while herbage cover was reduced by a quarter. The botanical composition of herbage varied remarkably between years, but very little between Grazed and Non-Grazed areas within each year. Non-browsed holm oak saplings became progressively larger than browsed ones, differences only reaching clear statistical significance at the end of the three experimental years. At this time, the volume of browsed saplings was 47–56 % smaller than that of non-browsed holm oaks, even though the former had also grown significantly in the course of the experiment.
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Impact of targeted sheep grazing on herbage and holm oak
saplings in a silvopastoral wildfire prevention system
in south-eastern Spain
Jabier Ruiz-Mirazo Ana Bele
´n Robles
Received: 29 July 2011 / Accepted: 10 March 2012 / Published online: 28 March 2012
ÓSpringer Science+Business Media B.V. 2012
Abstract Several wildfire prevention programs in
southern Europe are currently using livestock grazing
for the maintenance of fuelbreaks. This silvopastoral
management is valued for being sustainable and
effective in reducing fuel loads, but few studies have
analyzed other impacts linked to fuelbreak grazing.
This paper reports on an experiment performed within
the wildfire prevention program in Andalusia (south-
ern Spain) with the aim of clarifying and quantifying
the effect of fuelbreak grazing on herbage biomass,
ground cover, herbage species composition, and
growth of holm oak saplings. The study site, located
in a semiarid Mediterranean environment, was grazed
by a shepherded sheep flock from February to June in
three consecutive years at a similar stocking rate.
Livestock consumed between 33 and 68 % of herbage
production in the different years, and the greatest fuel
reduction (remaining dry matter of 200 kg ha
-1
) was
registered in Year 2, when rainfall and herbage
production was lowest. Ground cover was signifi-
cantly affected by grazing: on average, the percentage
of bare soil increased three-fold, while herbage cover
was reduced by a quarter. The botanical composition
of herbage varied remarkably between years, but very
little between Grazed and Non-Grazed areas within
each year. Non-browsed holm oak saplings became
progressively larger than browsed ones, differences
only reaching clear statistical significance at the end of
the three experimental years. At this time, the volume
of browsed saplings was 47–56 % smaller than that of
non-browsed holm oaks, even though the former had
also grown significantly in the course of the
experiment.
Keywords Biomass Ground cover Diversity
Grazed fuelbreak Mediterranean Semiarid
Introduction
In the Mediterranean region, the climatic conditions
(particularly the prolonged dry and hot summer
season) are naturally favorable for wildfires (FAO
2007). The occurrence and impact of wildfires have
increased over the last few decades in southern
European countries (Ve
´lez 2004), and this is mainly
attributed to land-use changes associated with socio-
economic development (FAO 2007). Indeed, many
traditional rural activities (e.g., firewood collection
and grazing-based livestock production systems) have
been generally abandoned in favor of other alterna-
tives (e.g., fossil fuels and factory farming). These
changes have led to more homogeneous landscapes
and the accumulation of fuel loads in forests and
rangelands (Moreira et al. 2001; Lasanta et al. 2006),
J. Ruiz-Mirazo (&)A. B. Robles
Consejo Superior de Investigaciones Cientı
´ficas (CSIC),
Estacio
´n Experimental del Zaidı
´n, C/Profesor Albareda 1,
18008 Granada, Spain
e-mail: jruizmirazo@gmail.com
123
Agroforest Syst (2012) 86:477–491
DOI 10.1007/s10457-012-9510-z
producing an increase in fire hazard. The situation is
further aggravated by current climate trends (Pausas
2004) and the persistent high numbers of human-
caused wildfire ignitions (Martı
´nez et al. 2009). Under
such conditions, the likelihood of severe wildfire
events happening is currently very high in the northern
rim of the Mediterranean.
Accordingly, wildfires have become a major issue
for forest services in southern European countries and
so specific wildfire prevention programs have been
established (Ve
´lez 2009). In these programs, the
increased forest vulnerability to wildfires is seldom
dealt with at the landscape level. Instead, preventive
actions usually concentrate on a network of firebreaks
and fuelbreaks designed to contain the spread of
wildfires and improve the chances of fire suppression
brigades successfully attacking fires (Agee et al.
2000). Firebreaks are narrow, tree-less strips with
scarce vegetation (if any), whereas fuelbreaks are
wider strips (or blocks) of vegetation that have been
altered to reduce the amount and continuity of
biomass, thus minimizing fire hazard. Many fuel-
breaks keep a sparse tree cover and are therefore
named shaded fuelbreaks (Agee et al. 2000). In this
text, the term ‘‘fuelbreak’’ is frequently used sensu
lato, to refer jointly to both firebreaks and fuelbreaks.
Fuelbreaks require regular maintenance (e.g., brush
cutting) to offset vegetation growth, and livestock
grazing could well serve this purpose. Indeed, live-
stock-grazed fuelbreaks are common in several wild-
fire prevention programs in the Mediterranean, and
particularly in south-eastern France (Thavaud 2006)
and in Andalusia, southern Spain (Ruiz-Mirazo et al.
2011). The capacity of livestock to effectively control
grass and shrub growth in Mediterranean areas is also
supported by scientific evidence (Torrano and Valder-
rabano 2005; Casasu
´s et al. 2007; Jauregui et al. 2007;
Dopazo et al. 2009) and, therefore, targeted grazing
could be expected to successfully reduce fuel loads in
fuelbreaks. However, grazed fuelbreaks represent a
singular silvopastoral system that demands specific
management to reduce fuel loads and fire hazard
effectively. For instance, Thavaud (2009) advised that
the herbage should be completely consumed at least
once per year in these systems. Also, the provision of
some concentrate feed is recommended to stimulate
livestock to browse shrubs (Thavaud 2009).
As fuelbreaks represent a relatively small propor-
tion of the total forest area, some of their undesired
side effects (e.g., visual impact and timber production
loss) may be deemed to be of minor importance in
view of their wildfire preventive function; neverthe-
less, increasing efforts are being made to mitigate
these effects. Fuelbreak maintenance itself also has
certain types of impact that managers must evaluate
together with the cost-effectiveness of each mainte-
nance technique. Livestock grazing is usually consid-
ered a particularly sustainable option for maintaining
fuelbreaks, as it transforms fuel into forage and can
have positive effects on biodiversity (E
´tienne 2001),
as well as contributing to rural development (Gon-
za
´lez-Rebollar et al. 1999). In contrast, heavy regular
grazing could also be expected to increase bare soil
and facilitate erosion (Papanastasis et al. 2003;
Thornes 2007), affect species composition (Noy-Meir
et al. 1989; Ferna
´ndez Ale
´s et al. 1993), and cause
damage to trees, especially saplings (McPherson
1993; Hester et al. 1996).
The aforementioned effects of grazing are likely to
occur in grazed fuelbreaks, but the data available in the
literature have seldom been obtained under such
management conditions. Therefore, the severity and
importance of such impacts in grazed fuelbreaks have
remained uncertain and specific experiments and
analyses seemed necessary to clarify and quantify
these effects. Accordingly, a 3-year experiment was
performed within the wildfire prevention program in
Andalusia, in a grazed fuelbreak managed by a
professional livestock farmer, with the following
objectives: (1) to quantify the impact of grazing on
herbage biomass and ground cover; (2) to detect
grazing-related changes in herbage species composi-
tion and diversity; and (3) to measure the effect of
grazing on the growth of saplings.
Materials and methods
Study site
This study was conducted on the ‘‘Cortijo Conejo y
Albarra
´n’’ estate (Guadix, province of Granada), in
south-eastern Spain (37°230N and 3°030W, at 1,100 m
a.s.l.). The mean annual rainfall for the area is 300 mm;
in a weather station located 6 km from the study site,
331, 297 and 346 mm of precipitation were collected in
the years 2007, 2008 and 2009, respectively. In this
Mediterranean region, herbage is mostly composed of
478 Agroforest Syst (2012) 86:477–491
123
therophytes, annual species that survive the hot dry
summer as seeds and germinate with the first autumn
rains. Accordingly, herbage production was most
closely related to rainfall received between September
and April, which was 227 mm in 2006–2007, 171 mm
in 2007–2008, and 294 mm in 2008–2009.
Temperatures recorded in the study period ranged
from –9 to 38 °C. According to Rivas-Martı
´nez and
Loidi (1999), the area is in the Mesomediterranean
semiarid bioclimatic belt. The estate extends across
near-flat terrain (2–3 % slopes) and the soil is a petric
calcisol (Ripoll 2004; IUSS Working Group WRB
2006), poor in organic matter (1.6 % in the top
horizon). The climax vegetation for this land is holm
oak (Quercus rotundifolia Lam.) forest (Valle 2003),
while the Aleppo pine (Pinus halepensis Mill.) is also
naturally present in the surroundings, particularly on
steeper slopes and where there are poorer soil
conditions.
This 900-ha estate was cultivated for decades
before it was bought by the regional government of
Andalusia in 1993, when it ceased to be ploughed. In
1994–1996, a 500 ha area of this degraded agricultural
land was afforested at a density of 1,500–2,000
trees ha
-1
with Aleppo pines and a small proportion
(5 %) of holm oaks. The plantation is traversed by a
linear treeless firebreak, which is 35 m wide and
1.4 km long. Alongside this firebreak, a 38-ha shaded
fuelbreak (Agee et al. 2000) was created in 2005 by
thinning the plantation and pruning all pine branches
less than 1 m from the ground. Until 2003, the
firebreak was regularly bulldozed to leave it devoid
of vegetation for the summer. Since 2005, however,
vegetation on both the firebreak and the fuelbreak has
been managed through livestock grazing to reduce fuel
loads.
The study site comprised both the firebreak and the
fuelbreak. Experimental plots for evaluating grazing
impact on herbage were located in the firebreak, and
included six exclosures that were set up in 2004. The
saplings monitored were a sample of the holm oaks
located in the fuelbreak area closest to the firebreak,
where pine density had been reduced to 250 trees ha
-1
.
Grazing management
Grazing on the study site for fuel load control and fire
prevention purposes was commissioned from the same
professional farmer in three consecutive years: 2007
(Year 1), 2008 (Year 2) and 2009 (Year 3). The farmer,
who shepherded livestock personally, was offered a
yearly remuneration of 1,600 in exchange for this
service (Varela-Redondo et al. 2008). The flock was
initially composed of 500 sheep (Seguren
˜abreed, live
weight: 45–50 kg) and 30 goats (mixed breed, live
weight: 40–55 kg), but it had grown to 900 sheep and
30 goats by the end of the study period. The study site
was grazed yearly between February and early June,
the period of the year when the largest quantity of fresh
pasture is available in this location. During this period,
livestock did not receive any supplementary feed, but
the flock could also graze on the approximately 400 ha
of pastures available in the ‘‘Cortijo Conejo y Alba-
rra
´n’’ estate. Therefore, the stocking rate applied on
the 40-ha study site could not be specifically con-
trolled, but rather depended on the management of the
livestock farmer.
At the end of each grazing season (June), fire
prevention personnel performed a technical assess-
ment to determine the extent to which the grazing
objective (i.e., a drastic reduction of the annual
biomass production) had been accomplished. A five
level classification (0–4) was used, corresponding to
negligible (0), light (1), moderate (2), heavy (3) and
very heavy (4) grazing intensities. The assessments
resulted in the following mean values for Year 1, Year
2, and Year 3, respectively: 2.67, 3.67 and 2, in the
firebreak; 1.33, 3.67 and 1.67, in the fuelbreak. Further
details on the methodology applied in this assessment
can be found in Ruiz-Mirazo et al. (2011).
Firebreak grazing: effect on herbage
The impact of grazing on herbage was monitored in six
plots located along the treeless firebreak. Each plot
comprised two subplots: (1) a 6 m 96 m exclosure,
constructed with a 1.2-m-high mesh wire fence (Non-
Grazed subplot); and (2) an unfenced area of a similar
size (Grazed subplot). Grazed subplots were located
approximately 3 m away from the exclosures, to
ensure a sufficient proximity and so minimize spatial
variation in pastures, while livestock distribution was
not disturbed by the presence of the fences.
The vegetation was characterized in the 12 exper-
imental units (subplots) at the end of the livestock
grazing and vegetation growth season (June) in Year 1,
Year 2 and Year 3, using both destructive and non-
destructive procedures. Herbage biomass was
Agroforest Syst (2012) 86:477–491 479
123
determined destructively by cutting and collecting all
above-ground biomass in eight 50 cm 950 cm quad-
rats per subplot. These quadrats were randomly
located, with two spatial restrictions: they had to be
25 cm away from the fixed transects (see below) and
the same quadrat could not be sampled twice in the
3-year study period. The material from each quadrat
was oven-dried to constant weight at 60 °C and the dry
matter (DM) weighed to the nearest 0.1 g. Data from
the eight quadrats was averaged and units transformed
into kg DM ha
-1
.
The point-intercept (non-destructive) method was
also applied to all subplots, following a modification
proposed by Daget and Poissonet (1971) of the point-
quadrat method originally described by Levy and
Madden (1933). More specifically, three 5-m-long
point-intercept transects were established in fixed
parallel lines that were 1.25 m apart. A long, 2-mm-
diameter pin was lowered vertically into the sward
every 5 cm along each transect, resulting in a total of
300 sample points per subplot. At each point, ‘‘herb-
age’’ was recorded if the pin touched any part of a live
or recently dead plant. When no contact was made
with any plants, either ‘‘bare soil’’ or ‘‘litter’’ was
registered, reflecting the absence/presence of dead
plant material on the ground in contact with the pin.
These data were summarized in each subplot to
describe ground cover distribution; i.e., the percent-
ages occupied by each of the three ground-cover types:
bare soil, litter and herbage.
Sample points where herbage was contacted were
further characterized by identifying all vascular plant
species touched by the pin. A recent Flora of Eastern
Andalusia was the reference used for plant species
names (Blanca et al. 2009). The species richness (S)
found in each subplot was obtained by a direct count of
the number of species recorded. The Jaccard index (J)
was used for pair-wise comparisons of the botanical
composition, both within each plot in a given year
(Grazed vs. Non-Grazed subplots), and between years
in the same subplot. This index quantifies the similar-
ity between pairs of plant communities from 0 (no
species in common) to 1 (identical composition),
according to the formula:
J¼a
aþbþc
where ais the number of species present in both
communities, bis the number of species present only
in the first community, and cis the number of species
present only in the second community (Magurran
2004).
The specific contribution (SC) of a plant species in
a subplot was calculated as the ratio between the
number of pins that made contact with that species and
the sum of the number of pins that made contact with
each of the species recorded (Daget and Poissonet
1971; Glatzle et al. 1993). By definition, this param-
eter measures abundance of a species in relative terms
and the sum of the SCs of all species in a community
will equal 100 %. SC values of species belonging to
the same botanical family were added together to
obtain family contribution (FC) values. SC was also
used to calculate the Shannon diversity index (H’),
according to the formula:
H0¼X
i¼S
i¼1
pilog2pi
where p
i
is the relative abundance of the ith species,
which was estimated with SC, and Sthe species
richness (i.e., number of species) found in a subplot.
Finally, percentage cover (PC) of a plant species in
a subplot was calculated as the percentage of pin
sample points at which that plant species was found
(Levy and Madden 1933; Glatzle et al. 1993). This
parameter measures abundance of a species in abso-
lute terms, and the sum of PCs of all species in a
community will equal (or exceed, if species overlap)
the percentage of the ground covered by herbage. PC
and SC were used jointly to assess the overall effect of
grazing on the most common species in the herbage. A
lower PC value in Grazed subplots indicates that a
plant species has been consumed by livestock, while a
lower SC value indicates that livestock prefer that
plant species over other species in the community.
Fuelbreak grazing: effect on holm oak saplings
The impact of grazing on holm oak saplings was
assessed by monitoring 240 individuals located in the
shaded fuelbreak; each of the saplings constituted an
experimental unit. The size of holm oaks was first
measured in February 2007, before the beginning of
the grazing season, and constituted the ‘‘Year 0’
reference. A tape measure was used to determine, to
the nearest centimeter, plant height (H, to their highest
living leaf) and two cross widths. Plant diameter
480 Agroforest Syst (2012) 86:477–491
123
(D) was calculated as the geometric mean of the
widths. These parameters were used to estimate the
volume of holm oaks (V), which was assumed to
approximate to an elliptical cylinder (V=pD
2
H/4).
The size of saplings was expected to have a direct
relationship with the capacity of holm oaks to
withstand grazing. To test this hypothesis, holm oaks
were divided into three size classes (n=80) accord-
ing to their initial volume: Small (\3dm
3
), Medium
(3–15 dm
3
) and Large ([15 dm
3
). As their volume
suggests, even saplings in the Large size class were
relatively small and easily reachable by sheep. Next,
half of the holm oaks in each class (n=40) were
individually protected from livestock using a 1.2-m-
high mesh wire fence. These Non-Browsed individu-
als were selected in such a way that their mean initial
volume was equal to that of the Browsed saplings in
each size class. In addition, care was taken to ensure
that Browsed and Non-Browsed holm oaks were
interspersed and, thus, avoid any differences between
groups being due to uncontrolled spatial variation in
conditions for growth.
Holm oak measurements were repeated annually in
the winter to regularly monitor their growth and search
for differences between groups. The last measurement
was performed in January 2010, 3 years after the start
of the experiment. In the course of Year 2, one Small
Browsed holm oak died, but it seemed to have
withered naturally rather than having been directly
affected by livestock browsing. In Year 3, two Large
Browsed holm oaks were cut and shredded by accident
during some forest works in an adjacent area.
Statistical analysis
In accordance with the experimental design, the values
of herbage biomass and ground cover were analyzed
using factorial ANOVA. Grazing treatment and Year
were the fixed experimental factors, while Plot was the
blocking factor. Tukey’s HSD post hoc tests were used
for multiple comparisons. The intention had been to
use the same procedure to analyze the botanical
composition of herbage (S,H’, SC, FC and PC), but
these parameters failed to meet the statistical assump-
tions. Therefore, the non-parametric two-sample Wil-
coxon rank-sum test was used to identify any
significant differences between Grazed and Non-
Grazed subplots, both overall over the 3 years and
separately in each year. In the event of ties between
values, an asymptotic approximation of this test was
used (see wilcox_test in R Development Core Team
2009).
Holm oak dimensions (height, diameter and vol-
ume) in the course of the experiment were analyzed
separately for the Small, Medium and Large classes.
Browsed and Non-Browsed groups in each size class
were compared through two-sample Student’s t-tests.
Inter-annual growth within each group was assessed
with paired Student’s t-tests applied to consecutive
measurements of height, diameter and volume. This
process determined whether each holm oak dimension
was significantly larger or smaller than the observation
made the year before. The same test was applied to
compare final and initial dimensions of holm oaks. In
these analyses, normality of the distribution of the
mean was ensured by the large number of samples per
group. When the homoscedasticity assumption was
not met, the Welch t-test was applied instead.
The statistical analysis was performed using the R
2.9.1 software package (R Development Core Team
2009). The Shapiro–Wilk and Bartlett tests were used
to test for normality and homoscedasticity, respec-
tively. In all cases, a 95 % confidence level was used to
establish statistically significant differences. Mean
values are followed by ±the standard error of the
mean.
Results
Firebreak grazing: effect on herbage
The comparison between Grazed and Non-Grazed
treatments (Fig. 1) indicated that livestock consumed
very similar amounts of herbage in the three exper-
imental years (range: 419–446 kg DM ha
-1
). How-
ever, production of herbage varied from year to year,
being roughly proportional to the total rainfall regis-
tered in the previous September–April period. Indeed,
mean herbage biomass measured at the end of the
growth season in Non-Grazed subplots was lowest in
the dry Year 2 (625 kg DM ha
-1
, after 171 mm of
rainfall) and highest in the much wetter Year 3
(1,250 kg DM ha
-1
, 294 mm). Consequently, the
percentage of herbage consumed by livestock also
varied between years: 50 % in Year 1, 68 % in Year 2,
and 33 % in Year 3. In agreement with these
observations, the ANOVA indicated that both Grazing
Agroforest Syst (2012) 86:477–491 481
123
(F
1,25
=71.84, P\0.001) and Year (F
2,25
=51.91,
P\0.001) were very significant factors for herbage
biomass, whereas the interaction between Grazing and
Year was not (F
2,25
=0.02, P=0.976).
Regarding ground cover (Fig. 2), Grazing increased
bare soil (F
1,25
=131.96, P\0.001) and reduced
herbage cover (F
1,25
=45.82, P\0.001). On average,
with Grazing the percentage of bare soil increased by a
factor of three (from 10.2 to31.4 %), and herbage cover
was reduced by a quarter (from 63.4 to 47.4 %). Grazing
also tended to reduce litter (on average, from 26.4 to
21.3 %), but this effect was unclear (F
1,25
=3.46,
P=0.075) due to the increase in litter observed in Year
1 with Grazing. When only datafrom Year 2 and Year 3
were analyzed, the effect of Grazing on litter reached
statistical significance (F
1,15
=8.30, P=0.011). Year
had a very significant effect onthe three types of ground
cover (P\0.001 in all cases) and its interaction with
Grazing was also found to be statistically significant for
bare soil (F
2,25
=6.58, P=0.005) and litter cover
(F
2,25
=28.38, P=0.009).
A total of 57 plant species were identified in the
firebreak during the study period (the full catalogue is
provided in the Appendix Table 3). Forty-seven of
them are therophytes, nine hemicryptophytes and one
chamaephyte. Overall FC values showed that herbage
was dominated by grasses (59 %), followed by
legumes (18 %). The Asteraceae family was also
fairly abundant (12 %), while Caryophyllaceae ranked
fourth (7 %). The FC of all other families was small (4
% in total), but they contributed 19 species to the
catalogue, a third of the total. The ten most common
plant species are listed in Table 1.
Remarkable variations were registered in the
botanical composition of herbage in the course of the
experiment (Fig. 3). Indeed, values of all botanical
parameters differed notably between years. On the
other hand, there were hardly any differences between
Grazed (G) and Non-Grazed (NG) subplots within
each year. Considering the three experimental years
together, Grazed subplots tended to have somewhat
lower species richness (G: 12.8 ±1.22 vs. NG:
14.5 ±1.33), but the Shannon diversity index
remained unaltered (G: 2.5 ±0.18 vs. NG:
2.5 ±0.15). The statistical analysis of these two
parameters showed that neither overall nor in any of
the years considered separately were the slight differ-
ences caused by Grazing significant.
Family contribution (FC) values were also largely
unaffected by Grazing. The trend observed was only
the same in the three experimental years for Astera-
ceae, which tended to be less abundant with Grazing
(G: 8.9 % ±2.09 vs. NG: 14.6 % ±3.09), and
Caryophyllaceae, which tended to be more abundant
with Grazing (G: 8.3 % ±1.64 vs. NG: 4.5
%±0.98). Nonetheless, these overall differences
were not statistically significant. In fact, the non-
parametric tests only detected significant differences
between Grazed and Non-Grazed plots for Fabaceae
in Year 1 and Caryophyllaceae in Year 3 (Fig. 3).
Specific contribution (SC) and percentage cover
(PC) also fluctuated strongly between years, and the
Fig. 1 Mean values of herbage biomass (kg DM ha
-1
)in
Grazed and Non-Grazed areas through the course of the
experiment. Whiskers on the top of the bars represent the
standard error of the mean. Different letters indicate significant
differences (P\0.05) between the 6 years 9treatment com-
binations, according to Tukey’s HSD test
Fig. 2 Mean distribution of ground cover (%) corresponding to
herbage, litter and bare soil in Grazed (G) and Non-Grazed (NG)
areas through the course of the experiment. Different letters
within each of the three types indicate significant differences
(P\0.05) between the 6 years 9treatment combinations,
according to Tukey’s HSD test
482 Agroforest Syst (2012) 86:477–491
123
Table 1 Overall mean
values (±the standard error
of the mean) of percentage
cover (PC) and specific
contribution (SC) of the ten
most common plant species,
in Grazed and Non-Grazed
areas
Only for the species
V. peregrina were
differences in PC and SC
statistically significant
FAMILY/Species Percentage cover (%) Specific contribution (%)
Non-Grazed Grazed Non-Grazed Grazed
POACEAE
Bromus matritensis L. 21.5 ±4.97 18.2 ±3.92 26.7 ±5.44 32.0 ±5.27
Aegilops triuncialis L. 11.1 ±3.82 4.1 ±1.51 15.8 ±5.04 7.4 ±2.36
Cynodon dactylon (L.) Pers. 3.9 ±0.68 4.4 ±1.11 5.7 ±1.05 8.0 ±1.87
Bromus tectorum L. 2.4 ±1.11 2.7 ±0.66 2.6 ±1.12 4.4 ±1.08
FABACEAE
Trigonella polyceratia L. 5.9 ±1.36 5.5 ±1.17 10.8 ±2.73 16.2 ±4.38
Medicago minima (L.) L. 4.5 ±2.11 2.5 ±1.17 7.1 ±3.62 5.9 ±2.97
Vicia peregrina L. 3.9 ±0.89 0.1 ±0.05 4.6 ±0.94 0.2 ±0.07
ASTERACEAE
Andryala ragusina L. 7.9 ±2.09 3.2 ±0.95 11.6 ±3.07 6.3 ±1.72
CARYOPHYLLACEAE
Bufonia tenuifolia L. 1.4 ±0.49 2.1 ±0.68 1.5 ±0.47 3.4 ±0.96
PLANTAGINACEAE
Plantago albicans L. 1.5 ±1.04 1.2 ±0.56 1.6 ±1.02 2.9 ±1.33
Fig. 3 Mean species richness (S), Shannon diversity index (H’), and family contribution (%) in Grazed and Non-Grazed areas through
the course of the experiment
Agroforest Syst (2012) 86:477–491 483
123
impact of grazing on the most common plant species
was unclear in most cases (Table 1). The only
consistent and significant effect of grazing was a
diminution in the abundance of V. peregrina,a
climbing and very palatable legume. Indeed, PC and
SC for this species were significantly lower in Grazed
subplots, over the whole experiment (Z=4.22,
P\0.001), in Year 1 (Z=2.93, P=0.003) and in
Year 3 (Z=2.90, P=0.004). In Year 2 the differ-
ence did not quite reach the threshold for significance
(Z=1.89, P=0.059), as in this year V. peregrina
was scarce even in Non-Grazed subplots.
Regarding the three most frequent species, it is
worth noting that the absolute and relative abundance
of both A. ragusina and A. triuncialis tended to be
reduced by grazing, whereas B. matritensis was not
particularly affected and even tended to increase its
specific contribution. However, these tendencies and
other differences reflected in Table 1never reached
statistical significance.
The Jaccard index also suggested a relatively weak
influence of Grazing on botanical composition
(Fig. 4). The mean value of this index between Grazed
and Non-Grazed subplots in the same year (range:
0.518–0.551) was greater than between years in the
same subplots (range: 0.362–0.486). Year 1 and Year
3 showed greater similarity between them than with
Year 2. Overall, Non-Grazed Year 2 subplots were the
most dissimilar (i.e., lowest Jvalues) across all pair-
wise comparisons.
Fuelbreak grazing: effect on holm oak saplings
In this experiment, it was found that Grazing did
restrict holm oak growth, and to a similar extent in the
three size classes. Despite being the same size at the
beginning of the experiment (Year 0), Non-Browsed
holm oaks were significantly larger in all dimensions
than Browsed ones at the end of Year 3 in all size
classes (Table 2). The difference was more acute in
height (mean height in Browsed groups was 26–33 %
smaller than in Non-Browsed groups across size
classes) than in diameter (15–22 %), and both
combined produced a notable difference in holm oak
volume (47–56 %).
However, the comparison between the initial (Year
0) and final (Year 3) dimensions (height, diameter and
volume) showed that Browsed holm oaks had also
grown significantly (P\0.05) in most cases. The only
exception to this was holm oak height in the Large
Browsed group (t
37
=1.72, P=0.094), which even
decreased inter-annually between Year 1 and Year 2.
Indeed, height was the holm oak dimension that was
most quickly affected by grazing: only height was
significantly different between groups in all size
classes at the end of Year 2 (Table 2).
Inter-annual growth was always positive in Non-
Browsed groups, as well as in Browsed holm oaks at
the end of Year 1, and in most cases also in Year 3
(Table 2). In contrast, Browsed holm oak height and
volume did not significantly increase in the course of
Year 2. However, this was also the year when Non-
Browsed holm oaks grew least: their inter-annual
growth in height (8 %) and diameter (9 %) in Year 2
was smaller than growth recorded in Years 1 and 3
(23–26 % in height, 35–37 % in diameter). As a result,
differences in holm oak dimensions between the
Browsed and Non-Browsed groups did not reach clear
statistical significance until Year 3.
Discussion
Firebreak grazing: effect on herbage
Despite the similarity in the amount of herbage
consumed by livestock in the 3 years (Fig. 1), the
grazing intensity assessments made visually by wild-
fire prevention personnel on the firebreak were
understandably distinct between years, as herbage
Year 1
Non-Grazed
Year 2
Non-Grazed
Year 2
Grazed
Year 3
Grazed
Year 1
Grazed
Year 3
Non-Grazed
0.551 0.549
0.518
0.486
0.474
0.3620.373
0.422 0.426
Fig. 4 Mean values of the Jaccard index calculated both within
each plot (Grazed vs. Non-Grazed subplots) in each year and
between years in the same subplot
484 Agroforest Syst (2012) 86:477–491
123
Table 2 Mean values (±the standard error of the mean) of holm oak height (cm), diameter (cm) and volume (dm
3
) through the course of the experiment
Small Medium Large
Browsed Non-Browsed t-test Browsed Non-Browsed t-test Browsed Non-Browsed t-test
Year 0
a
Height (cm) 12.1 ±0.49 13.4 ±0.55 t
78
=1.77
P=0.081
20.6 ±0.78 19.7 ±0.74 t
78
=-0.81
P=0.418
35.8 ±1.60 34.5 ±1.45 t
78
=-0.59
P=0.556
Diameter (cm) 11.1 ±0.57 10.7 ±0.53 t
78
=-0.39
P=0.698
20.7 ±0.66 20.8 ±0.57 t
78
=0.10
P=0.921
35.4 ±1.30 36.7 ±0.98 t
78
=0.78
P=0.435
Volume (dm
3
) 1.4 ±0.13 1.4 ±0.14 t
78
=0.03
P=0.979
7.0 ±0.45 7.1 ±0.53 t
78
=0.03
P=0.980
39.1 ±3.95 39.1 ±3.26 t
78
=0.001
P=0.997
Year 1
Height (cm) 14.5 ±0.69 (?) 16.7 ±0.72 (?)t
78
=2.17
P= 0.033
25.1 ±0.84 (?) 25.3 ±0.96 (?)t
78
=0.16
P=0.876
39.5 ±1.58 (?) 40.8 ±1.50 (?)t
78
=0.60
P=0.552
Diameter (cm) 13.9 ±0.76 (?) 14.3 ±0.85 (?)t
78
=0.44
P=0.664
27.3 ±1.06 (?) 29.1 ±1.03 (?)t
78
=1.19
P=0.236
45.9 ±1.95 (?) 49.7 ±1.60 (?)t
78
=1.51
P=0.134
Volume (dm
3
) 2.8 ±0.31 (?) 3.4 ±0.48 (?)t
66
=1.18
b
P=0.240
16.4 ±1.70 (?) 18.6 ±1.71 (?)t
78
=0.93
P=0.357
76.7 ±9.22 (?) 86.5 ±7.80 (?)t
78
=0.81
P=0.418
Year 2
Height (cm) 14.1 ±0.70 (=) 18.4 ±0.82 (?)t
77
=3.93
P< 0.001
24.0 ±1.04 (=) 27.4 ±1.08 (?)t
78
=2.29
P= 0.025
38.4 ±1.59 (-) 44.1 ±1.68 (?)t
78
=2.48
P= 0.015
Diameter (cm) 15.0 ±0.86 (?) 15.7 ±0.94 (?)t
77
=0.57
P=0.573
27.7 ±1.26 (=) 30.8 ±1.20 (?)t
78
=1.82
P=0.072
47.9 ±1.99 (?) 53.0 ±1.66 (?)t
78
=1.97
P=0.053
Volume (dm
3
) 3.2 ±0.38 (=) 4.5 ±0.63 (?)t
64
=1.85
b
P=0.069
17.0 ±2.13 (=) 23.0 ±2.39 (?)t
78
=1.86
P=0.067
81.0 ±9.44 (=) 107.1 ±10.40 (?)t
78
=1.89
P=0.067
Year 3
Height (cm) 15.3 ±0.67 (?) 22.8 ±0.93 (?)t
70
=6.53
b
P< 0.001
24.7 ±0.89 (=) 34.3 ±1.50 (?)t
63
=5.50
b
P< 0.001
38.0 ±1.91 (=) 51.1 ±1.71 (?)t
76
=5.12
P< 0.001
Diameter (cm) 19.1 ±0.94 (?) 22.5 ±1.14 (?)t
77
=2.31
P= 0.023
32.3 ±1.31 (?) 41.5 ±1.55 (?)t
78
=4.50
P< 0.001
51.9 ±2.06 (?) 64.0 ±1.82 (?)t
76
=4.42
P< 0.001
Volume (dm
3
) 5.2 ±0.54 (?) 11.0 ±1.33 (?)t
51
=4.01
b
P< 0.001
23.0 ±2.51 (?) 52.1 ±5.58 (?)t
54
=4.75
b
P< 0.001
94.0 ±12.00 (?) 176.7 ±14.35 (?)t
76
=4.39
P< 0.001
Signs in parenthesis within each column indicate a non-significant (=) or a significant (P\0.05) increase (?) or decrease (-) in height, diameter and volume since the measurement of the previous year.
Statistically significant differences (P\0.05) between Browsed and Non-Browsed holm oaks are highlighted in bold
a
In Year 0, no grazing had yet been applied. Tests only indicate the equivalence of initial dimensions in the two experimental groups of each size class
b
Unequal variance was detected in this parameter and so Welch’s t-test was applied
Agroforest Syst (2012) 86:477–491 485
123
biomass left after grazing (i.e., fuel in the event of fire
during the summer) was very different: from over
800 kg DM ha
-1
in Year 3 (mean technical assess-
ment value [TAV] was 2: moderate grazing on a 0–4
scale) to 200 kg DM ha
-1
in Year 2 (mean TAV was
3.67: very heavy grazing).
Two important lessons for silvopastoral wildfire
prevention systems can be drawn from these results.
Firstly, unlike in our experiment, the stocking rate
applied needs to be adapted to annual herbage
production, so the amount of fine fuel left after
grazing is always minimized. These fine fuels are a
crucial element to reduce flame length and, especially,
rate of spread of wildfires (Agee et al. 2000; Diamond
et al. 2009). Therefore, the simple approach of
establishing a fixed stocking rate for the silvopastoral
management of fuelbreaks, used in some wildfire
prevention programs (e.g., DOCV 2009), seems
inadequate, at least for fuelbreaks dominated by
herbaceous species.
Secondly, the farmer and the wildfire prevention
personnel agreed that the very heavy grazing regis-
tered in Year 2 was very close to a reasonable upper
limit for grazing intensity. Consequently, 200 kg DM
ha
-1
may be considered a good estimation of the
minimum amount of herbage biomass which will be
left after shepherded sheep grazing in firebreaks with
similar characteristics. According to a rangeland
burning experiment conducted by Diamond et al.
(2009) on comparable semiarid herbaceous vegeta-
tion, such an amount of biomass would lead to very
mild wildfires. Indeed, a fuel load of 260 kg DM ha
-1
was found to support fires with a mean flame length of
0.2 m and rates of spread lower than 7 m min
-1
in a
prescribed burn they performed in October, and
somewhat higher values (0.6 and 13 m min
-1
) under
modeled peak fire conditions. In an adjacent area with
150 kg DM ha
-1
, the fire died out in the prescribed
burn and authors obtained the same result when
simulating peak fire conditions.
As regards ground cover, litter tended to be reduced
by Grazing, in agreement with results obtained by
Rigolot and E
´tienne (1995) in the context of the
French wildfire prevention program, but the overall
effect we observed was unclear. This could be
attributed to the fact that grazing has two opposing
effects on the amount of litter: grass trampling
increases litter in the short term (i.e., the same year),
whereas consumption of herbage reduces the amount
of biomass that will become litter in the medium term
(i.e., the following year). This could explain the
somewhat larger litter cover values recorded in Grazed
subplots in Year 1, as hardly any grazing had taken
place the year before (at that time, another farmer
grazed his flock on the study area). Indeed, the analysis
made excluding data from Year 1 suggests that the
reduction in litter becomes significant after more than
1 year of regular grazing management.
The percentage of herbage ground cover was
closely linked to annual meteorological conditions,
with lowest values registered in Year 2 (Fig. 2). In
fact, mean herbage cover in Grazed subplots in Year 2
fell below 30 %, which is considered a critical
threshold for triggering erosion (Francis and Thornes
1990). Grazing reduced herbage cover consistently,
but it is also remarkable that Grazed subplots in Years
1 and 3 had higher percentages of herbage cover than
Non-Grazed subplots in Year 2. This result indicates
that herbage cover was largely determined by mete-
orological conditions and, to a much lesser extent, by
grazing management. A different conclusion was
obtained in mountain rangelands in Crete by Papan-
astasis et al. (2003), who found that very heavy
grazing produced larger reductions in plant cover than
those attributable to inter-annual variations.
In our experiment, bare soil was the parameter
which was most clearly affected by Grazing, as shown
by the threefold greater percentages registered, on
average, in Grazed subplots (Fig. 2). Undoubtedly,
such an increase in the direct exposure of soil to rain
and wind make it somewhat more susceptible to
erosion, at least until new plants germinate from the
seed bank in the following growth season. Neverthe-
less, a parallel study of soil parameters would have
been necessary in the experiment to fully discern the
consequences of this level of grazing-related, short-
term changes in ground cover.
Grazing caused negligible changes in herbage
species composition and diversity in this experiment
(Figs. 3,4). The changes observed did not show any
progressive trend suggesting cumulative effects from
the beginning of the trial. Rather, fluctuations were
apparently linked to other environmental factors; for
instance, species richness seemed to have a direct
relationship with rainfall and the associated annual
herbage production. The preponderance of such eco-
system/environmental variables when assessing graz-
ing effects on vegetation has already been highlighted
486 Agroforest Syst (2012) 86:477–491
123
by Milchunas and Lauenroth (1993), who modeled
data from 236 study sites worldwide. These authors
concluded that the degree of change in species
composition expected with grazing is primarily a
function of site productivity, changes being greater in
productive environments. According to this global
perspective, it is no surprise that only weak trends
towards shifts in species composition were observed in
our semiarid study site, where mean annual rainfall is
only 300 mm.
Other authors working specifically in Mediterra-
nean (but more humid) environments have agreed that
the clearest consequence of grazing is that it favors
low-growing species (Noy-Meir et al. 1989; Ferna
´n-
dez Ale
´s et al. 1993). This view is also supported by
the results we obtained for V. peregrina, which was the
only species whose presence consistently decreased
with grazing (Table 1). V. peregrina being a climber,
it was certainly more easily grazed than other common
legumes (T. polyceratia and M. minima), which
remained virtually unaffected, possibly due to their
creeping or low-growing form. In fact, such prostrate
growth is considered to be an adaptation to both
defoliation by grazing and drought conditions (Fern-
a
´ndez Ale
´s et al. 1993), which would further support
the aforementioned idea that effects of grazing are
likely to be milder in poorer, less productive areas.
However, it is also interesting that the most notable
effect of grazing was observed in a legume, which
suggests that the high palatability of V. peregrina may
have played a role in this species being preferentially
consumed by sheep. In contrast, Noy-Meir et al.
(1989) found that palatability was not a major factor in
the effects measured in cattle-grazed grasslands, and
the authors attribute this to the poor species selection
abilities of this larger type of livestock when herbage
height is less than 5 cm.
In Grazed areas we observed a non-conclusive trend
for an increased dominance of B. matritensis, which
could well be linked to the fact that this species
develops its armed inflorescence early in the season
and is thereafter rejected by livestock. For more
successful control of a similar species (cheatgrass, B.
tectorum), Mosley and Roselle (2006) indicate that
intense grazing needs to be appropriately timed,
namely, at the early boot stage, and must be repeated
few weeks later to control regrowth. A similar strategy,
with grazing management targeted at the dominant
species (B. matritensis in our experimental firebreak),
may be necessary to attain the greater levels of
vegetation control demanded for wildfire prevention.
To sum up, our results on botanical composition
and diversity indicate that these parameters will be
only slightly modified by grazing for wildfire preven-
tion in situations similar to our experimental condi-
tions. However, it must be noted that very heavy
grazing intensity was only registered in one of the
three experimental years. Even though the effects on
botanical composition were negligible both in that
Year 2 and the following Year 3, longer term effects
under prolonged very heavy grazing cannot be ruled
out. Indeed, it has been suggested that the grazing
intensity required to reduce biomass to levels that
would strongly influence fire behavior could compro-
mise sustained livestock production and ecosystems
goals in semiarid rangelands in the USA (Launchb-
augh et al. 2008). Accordingly, these authors suggest
that such grazing management must be restricted to
areas designated as fuelbreaks.
Fuelbreak grazing: effect on holm oak saplings
Non-Browsed holm oaks became progressively larger
than Browsed ones in the course of the experiment
(Table 2). Differences at the end of Year 1 were still
small, in agreement with the low grazing intensity
estimated in the technical evaluation (mean TAV was
1.33: light grazing). In Year 2, the lower rainfall and
higher grazing intensity registered (mean TAV was
3.67: very heavy grazing) imposed much more
restrictive conditions for growth. Indeed, as also
happened in the firebreak, Year 2 showcased the
outcome that may be expected after a comparatively
less favorable year: the change in size of Non-
Browsed holm oaks was positive but relatively small,
while Browsed saplings grew very little, only slightly
increasing in diameter. In Year 3 the grazing intensity
was not particularly heavy (mean TAV was 1.67:
moderate grazing), but the cumulative effect of
browsing the same holm oaks over three years
eventually produced clear differences in size between
Browsed and Non-Browsed saplings by the end of the
trial.
The results reported here should be considered a
valid reference for sheep grazing, but a greater impact
should be expected if browser-type livestock (e.g.,
goats) were to be used in fuelbreak maintenance
(Cuartas and Garcı
´a-Gonza
´lez 1992; Ruiz-Mirazo
Agroforest Syst (2012) 86:477–491 487
123
et al. 2011). The grazing season is another factor
which can greatly modify impact on saplings (Hester
et al. 1996). The fact that fuelbreak grazing took place
during the period of the year when the greatest
quantity of fresh pasture was available probably
contributed to reducing the impact of grazing we
observed on saplings. In other experiments performed
in the same grazing season but in a reforested holm oak
dehesa in southern Spain, sheep dedicated only 2 % of
their grazing time to browsing holm oak saplings, both
in February (Bla
´zquez et al. 2005) and April (Bla
´z-
quez et al. 2003). These authors concluded that the
abundance of herbage in both periods helped diminish
browsing, and warned of greater impacts under
different conditions. On the other hand, controlled
grazing can also benefit sapling survival and growth
by reducing competition with herbage for soil mois-
ture (McPherson 1993; Bla
´zquez et al. 2005).
Larger holm oakswere expected to withstand grazing
better than those in the Small size class. Indeed, severe
damage seemed likely for some of the smaller saplings,
as they could lose most of their foliage if livestock chose
to browse them. Nevertheless, our results showed that
the difference in size between Browsed holm oaks and
Non-Browsed saplings was approximately the same (in
percentage) across the three size classes at the end of the
trial. Further, statistically significant differences mostly
appeared at the sametime and yearly growth trends were
also similar in all size classes (Table 2). In sum, the
hypothesis that size of saplings had a direct relationship
with their capacity to withstand grazing is rejected, at
least for holm oaks within the size range we studied.
Undoubtedly, larger holm oak saplings can escape
browsing when they grow to a height that crowns are
beyond the reach of livestock. At this stage, damage to
tree bark is the main concern but, otherwise, grazing can
even benefit the development of tree-shaped holm oaks
by pruning low branches (Bla
´zquez et al. 2005).
Overall, our results indicate that sheep grazing for
wildfire prevention in fuelbreaks comparable to our
experimental conditions will restrict, but not impede,
the growth of holm oak saplings. The relative reduc-
tion in size we measured, which reached 47–56 % in
holm oak volume after 3 years of grazing, may be
considered acceptable in view of fuelbreaks’ protec-
tive function in the forest. However, this will
ultimately depend on other concurrent management
goals, namely medium-term restoration of holm oak
forest. If it were considered necessary, individual
protectors such as those used in this experiment could
make targeted grazing compatible with a faster growth
rate of saplings.
Conclusions
This 3-year experiment performed in a semiarid
Mediterranean environment provides data that has
been lacking to date concerning the effects of targeted
sheep grazing on herbage and holm oak saplings in a
grazed fuelbreak. According to the results obtained, it
is very important to adjust the stocking rate yearly to
the annual herbage production, in order to ensure that
herbage biomass is minimized every year. Reducing
this biomass to values below 200 kg DM ha
-1
through grazing could be difficult but also unneces-
sary, as this amount of fine fuel can only sustain mild
wildfires with a slow rate of spread.
In conditions similar to those in our experiment,
grazing for wildfire prevention should be expected to
produce a decrease in herbage cover, as well as a
notable increase in bare soil. After more than 1 year of
grazing, it is also likely that litter cover starts to
diminish. On the other hand, fuelbreak grazing will
hardly produce any changes in the botanical compo-
sition and diversity of herbage, at least during the first
years of grazing management. Finally, targeted graz-
ing will certainly restrict, but not impede, the growth
of holm oak saplings, as long as grazing is applied with
ovine livestock and in seasons when abundant fresh
herbage is available.
These results provide a valuable reference for
wildfire specialists and forest managers, who will
establish the relative importance of the impacts related
to the silvopastoral management of fuelbreaks in view
of their wildfire prevention function and in compar-
ison with alternative approaches to fuelbreak
maintenance.
Acknowledgments The authors would like to acknowledge
Carmen Fallot, Domingo A
´lvarez, Alicia Garcı
´a, Anita Balinga,
Juan Cardoso, Fidel Delgado and Elsa Varela for their help with
field work. A
´lvaro Yeste also collaborated in the experiment by
grazing his sheep flock on the study area. The Ideas Need
Communicating Language Services team improved the use of
English in the manuscript. The first author was supported by an
I3P postgraduate grant from the Spanish National Research
Council (CSIC), co-funded by the European Social Fund. This
study was funded by Egmasa (Regional Government of
Andalucı
´a, Spain) through the project Grazed fuelbreaks as a
488 Agroforest Syst (2012) 86:477–491
123
fire-preventive silvicultural tool in Mediterranean forestlands,
coordinated by Dr. Gonza
´lez-Rebollar.
Appendix: plant catalogue
See Table 3.
Table 3 Catalogue of plant species in the firebreak, grouped
by botanical families. Families (in bold) are sorted by their
overall family contribution (FC) and, within families, species
are sorted by their overall specific contribution (SC)
FC/SC
(%)
FAMILY/Species
58.85 POACEAE
31.67 Bromus matritensis L.
12.17 Aegilops triuncialis L.
6.63 Cynodon dactylon (L.) Pers.
4.02 Bromus tectorum L.
1.31 Aegilops geniculata Roth
1.21 Lolium rigidum Gaudin
0.66 Avena barbata Link
0.58 Bromus diandrus Roth
0.40 Catapodium rigidum (L.) C. E. Hubb.
0.16 Hordeum murinum L.
0.03 Vulpia ciliata Dumort.
18.10 FABACEAE
9.05 Trigonella polyceratia L.
5.58 Medicago minima (L.) L.
3.22 Vicia peregrina L.
0.22 Astragalus sesameus L.
0.01 Coronilla scorpioides (L.) W. D. J. Koch
0.01 Hippocrepis ciliata Willd.
11.92 ASTERACEAE
8.80 Andryala ragusina L.
1.06 Crupina crupinastrum (Moris) Vis.
0.86 Filago pyramidata L.
0.75 Chondrilla juncea L.
0.18 Helichrysum italicum (Roth) G. Don
0.09 Anacyclus clavatus (Desf.) Pers.
0.07 Xeranthemum inapertum (L.) Mill.
0.03 Onopordum nervosum Boiss.
0.03 Leontodon longirrostris (Finch & P. D. Sell)
Talavera
0.03 Scorzonera angustifolia L.
0.01 Picris hispanica (Willd.) P. D. Sell
Table 3 continued
FC/SC
(%)
FAMILY/Species
6.85 CARYOPHYLLACEAE
2.76 Bufonia tenuifolia L.
1.73 Minuartia campestris L.
0.62 Silene nocturna L.
0.49 Silene conica L.
0.30 Paronichia argentea Lam.
0.28 Silene tridentata Desf.
0.27 Velezia rigida L.
0.25 Petrorhagia dubia (Raf.) G. Lo
´pez & Romo
0.13 Minuartia hybrida (Vill.) Schischk.
0.03 Vaccaria hispanica (Mill.) Rauschert
2.16 PLANTAGINACEAE
2.16 Plantago albicans L.
0.55 EUPHORBIACEAE
0.55 Euphorbia serrata L.
0.41 BRASSICACEAE
0.22 Descurainia sophia (L.) Prantl
0.15 Camelina microcarpa DC.
0.01 Eruca vesicaria (L.) Cav.
0.01 Hirschfeldia incana (L.) Lagr.-Foss.
0.01 Sisymbrium runcinatum DC.
0.38 OROBANCHACEAE
0.38 Bartsia trixago L.
0.32 PAPAVERACEAE
0.25 Hypecoum imberbe Sm.
0.04 Papaver hybridum L.
0.03 Glaucium corniculatum (L.) Rudolph
0.25 DIPSACACEAE
0.25 Lomelosia stellata (L.) Raf.
0.06 VERONICACEAE
0.06 Linaria arvensis (L.) Desf.
0.04 BORAGINACEAE
0.04 Neatostema apulum (L.) I. M. Johnston
0.03 LINACEAE
0.03 Linum strictum L.
0.03 RESEDACEAE
0.03 Reseda undata L.
0.03 RUBIACEAE
0.01 Crucianella angustifolia L.
0.01 Galium parisiense L.
0.01 GERANIACEAE
0.01 Erodium cicutarium (L.) L’He
´r.
100/100 TOTAL: 16 FAMILIES/57 species
Agroforest Syst (2012) 86:477–491 489
123
References
Agee JK, Bahro B, Finney MA, Omi PN, Sapsis DB, Skinner
CN, van Wagtendonk JW, Phillip Weatherspoon C (2000)
The use of shaded fuelbreaks in landscape fire manage-
ment. For Ecol Manag 127(1–3):55–66
Blanca G, Cabezudo B, Cueto M, Ferna
´ndez Lo
´pez C, Morales
Torres C (eds) (2009) Flora vascular de Andalucı
´a Orien-
tal, 4 vols. Consejerı
´a de Medio Ambiente (Junta de
Andalucı
´a), Sevilla
Bla
´zquez A, Ferna
´ndez-Rebollo P, Ferna
´ndez-Rebollo R, Car-
bonero MD (2003) Comportamiento del ovino en pastoreo
en una repoblacio
´n de encinas. Resultados preliminares. In:
Robles AB, Ramos ME, Morales MC, Simon E, Gonzalez
JL, Boza J (eds) Pastos, Desarrollo y Conservacio
´n. Con-
sejerı
´a de Agricultura y Pesca (Junta de Andalucı
´a), Se-
villa, pp 469–474
Bla
´zquez A, Ferna
´ndez-Rebollo P, Carbonero MD, Navarro R
(2005) Comportamiento del ganado ovino en una forestacio
´n.
Consumo de len
˜osas y dan
˜os a pla
´ntulas de encina. Paper
presented at the IV Congreso Forestal Espan
˜ol, Zaragoza
Casasu
´s I, Bernue
´s A, Sanz A, Villalba D, Riedel JL, Revilla R
(2007) Vegetation dynamics in Mediterranean forest pas-
tures as affected by beef cattle grazing. Agric Ecosyst
Environ 121(4):365–370
Cuartas P, Garcı
´a-Gonza
´lez R (1992) Quercus ilex browse uti-
lization by caprini in Sierra de Cazorla and Segura (Spain).
Vegetatio 100:317–330
Daget P, Poissonet J (1971) Une me
´thode d’analyse phytolog-
ique des prairies. Ann Agron 22:5–41
Diamond JM, Call CA, Devoe N (2009) Effects of targeted
cattle grazing on fire behavior of cheatgrass-dominated
rangeland in the northern Great Basin, USA. Int J Wildland
Fire 18:944–950
DOCV (2009) Orden de 11 de mayo de 2009, de la Conselleria
de Medio Ambiente, Agua, Urbanismo y Vivienda, por la
que se convocan y se aprueban las bases reguladoras de las
ayudas gestionadas por la Direccio
´n General de Gestio
´n del
Medio Natural, en materia de prevencio
´n de incendios
forestales, para el ejercicio 2009. Diario Oficial de la Co-
munitat Valenciana, Spain, pp 19585–19625
Dopazo C, Robles AB, Ruiz Garcı
´a R, San Miguel A (2009)
Efecto del pastoreo en el mantenimiento de cortafuegos en
la Comunidad Valenciana. Paper presented at the 58
Congreso Forestal Espan
˜ol, A
´vila
E
´tienne M (2001) Ame
´nagement de la fore
ˆtme
´diterrane
´enne
contre les incendies et biodiversite
´. Revue Forestie
`re
Franc¸aise Nume
´ro spe
´cial, pp 149–155
FAO (2007) Fire management—global assessment 2006. A
thematic study prepared in the framework of the global
forest resources assessment 2005. FAO, Rome
Ferna
´ndez Ale
´s R, Laffarga JM, Ortega F (1993) Strategies in
Mediterranean grassland annuals in relation to stress and
disturbance. J Veg Sci 4(3):313–322
Francis CF, Thornes JB (1990) Runoff hydrographs from three
Mediterranean vegetation covers. In: Thornes JB (ed)
Vegetation and erosion. Wiley, Chichester, pp 363–385
Glatzle A, Mechel A, Lourenco MEV (1993) Botanical com-
ponents of annual Mediterranean grassland as determined
by point-intercept and clipping methods. J Range Manag
46(3):271–274
Gonza
´lez-Rebollar JL, Robles AB, de Simo
´n E (1999) Las a
´reas
pasto-cortafuego: entre las pra
´cticas de gestio
´n y protec-
cio
´n de los espacios forestales mediterra
´neos (Propuestas
de selvicultura preventiva). In: Actas de la XXXIX Re-
unio
´n Cientı
´fica de la Sociedad Espan
˜ola para el Estudio de
los Pastos, Almerı
´a, pp 145–154
Hester AJ, Mitchell FJG, Kirby KJ (1996) Effects of season and
intensity of sheep grazing on tree regeneration in a British
upland woodland. For Ecol Manag 88(1–2):99–106
IUSS Working Group WRB (2006) World reference base for
soil resources 2006. FAO, Rome
Jauregui BM, Celaya R, Garcia U, Osoro K (2007) Vegetation
dynamics in burnt heather-gorse shrublands under different
grazing management with sheep and goats. Agrofor Syst
70(1):103–111
Lasanta T, Gonza
´lez-Hidalgo JC, Vicente-Serrano SM, Sferi E
(2006) Using landscape ecology to evaluate an alternative
management scenario in abandoned Mediterranean
mountain areas. Landsc Urban Plan 78:101–114
Launchbaugh K, Brammer B, Brooks ML, Bunting S, Clark P,
Davison J, Fleming M, Kay R, Pellant M, Pyke DA, Wylie
B (2008) Interactions among livestock grazing, vegetation
type, and fire behavior in the Murphy Wildland Fire
Complex in Idaho and Nevada, July 2007. U.S Geological
Survey, Washington
Levy B, Madden E (1933) The point method of pasture analysis.
N Z J Agr 46:267–279
Magurran AE (2004) Measuring biological diversity. Blackwell
Science, Oxford
Martı
´nez J, Vega-Garcı
´a C, Chuvieco E (2009) Human-caused
wildfire risk rating for prevention planning in Spain.
J Environ Manag 90:1241–1252
McPherson GR (1993) Effects of herbivory and herb interfer-
ence on oak establishment in a semi-arid temperate
savanna. J Veg Sci 4(5):687–692
Milchunas DG, Lauenroth WK (1993) Quantitative effects of
grazing on vegetation and soils over a global range of
environments. Ecol Monogr 63(4):327–366
Moreira F, Rego FC, Ferreira PG (2001) Temporal (1958–1995)
pattern of change in a cultural landscape of northwestern
Portugal: implications for fire occurrence. Landsc Ecol
16:557–567
Mosley JC, Roselle L (2006) Targeted livestock grazing to
suppress invasive annual grasses. In: Launchbaugh K (ed)
Targeted grazing: a natural approach to vegetation man-
agement and landscape enhancement. American Sheep
Industry Association, Denver, pp 68–77
Noy-Meir I, Gutman M, Kaplan Y (1989) Responses of Medi-
terranean grassland plants to grazing and protection. J Ecol
77(1):290–310
Papanastasis VP, Kyriakakis S, Kazakis G, Abid M, Doulis A
(2003) Plant cover as a tool for monitoring desertification
in mountain Mediterranean rangelands. Manag Environ
Qual 14(1):69–81
Pausas JG (2004) Changes in fire and climate in the eastern
Iberian Peninsula (Mediterranean basin). Clim Chang
63(3):337–350
490 Agroforest Syst (2012) 86:477–491
123
R Development Core Team (2009) R: a language and environ-
ment for statistical computing. Version 2.9.1. R Foundation
for Statistical Computing, Vienna
Rigolot E
´,E
´tienne M (1995) Epaisseur de la couverture morte
sur des coupures de combustible arbore
´es entretenues par
le pa
ˆturage. In: Anonymous (ed) Sylvopastoral systems:
Environmental, agricultural and economic sustainability.
Cahiers Options Mediterrane
´ennes, vol. 12. CIHEAM-
IAMZ, Zaragoza, pp 205–208
Ripoll MA (2004) Aprovechamiento de escorrentı
´as superfici-
ales mediante la construccio
´n de microcuencas: aplicacio
´n
a la forestacio
´n en ambientes mediterra
´neos. PhD Thesis,
Universidad de Granada, Spain
Rivas-Martı
´nez S, Loidi Arregui J (1999) Bioclimatology of the
Iberian Peninsula. Itinera Geobot 13:41–47
Ruiz-Mirazo J, Robles AB, Gonza
´lez-Rebollar JL (2011) Two-
year evaluation of fuelbreaks grazed by livestock in the
wildfire prevention program in Andalusia (Spain). Agric
Ecosyst Environ 141(1–2):13–22
Thavaud P (ed) (2006) Dispositif agroenvironnemental applique
´
a
`la pre
´vention des incendies de fore
ˆtenre
´gion me
´diter-
rane
´enne. Re
´sultats de 20 ans de re
´alisations et proposi-
tions pour l0avenir. Document de synthe
`se. Re
´seau
coupures de combustible, vol 11. E
´ditions La Carde
`re—
l0E
´phe
´me
`re, Laudun
Thavaud P (ed) (2009) Guide pratique pour l’entretien des
coupures de combustible par le pastoralisme. Re
´seau
coupures de combustible, vol 12. E
´ditions La Carde
`re—
l0E
´phe
´me
`re, Laudun
Thornes JB (2007) Modelling soil erosion by grazing: recent
developments and new approaches. Geogr Res 45(1):
13–26
Torrano L, Valderrabano J (2005) Grazing ability of European
black pine understorey vegetation by goats. Small Rumin
Res 58(3):253–263
Valle F (2003) Mapa de series de vegetacio
´n de Andalucı
´a.
Editorial Rueda, Madrid
Varela-Redondo E, Calatrava-Requena J, Ruiz-Mirazo J,
Jime
´nez-Piano R, Gonza
´lez-Rebollar JL (2008) El pasto-
reo en la prevencio
´n de incendios forestales: ana
´lisis
comparado de costes evitados frente a medios meca
´nicos
de desbroce de la vegetacio
´n. Pequen
˜os Rumiantes 9(3):
12–20
Ve
´lez R (2004) Europa: desarrollo y fuego. Paper presented at
the II Simposio sobre Polı
´ticas, Planificacio
´n y Economı
´a
en la Defensa contra Incendios Forestales, Co
´rdoba
Ve
´lez R (ed) (2009) La defensa contra incendios forestales.
Fundamentos y experiencias, 2nd edn. McGraw-Hill,
Aravaca
Agroforest Syst (2012) 86:477–491 491
123
... While economic valuation is considered controversial for the idea of the commodification of nature and the difficulties to assess cultural ES , sociocultural valuation of ES linked to European agroforestry in scientific literature is hoarded by Spanish "dehesas" and Portuguese "montados" . Comparatively, little is known about livestock grazing in forest understory (Ruiz-Mirazo and Robles, 2012), that hinders the development of management guidelines, incentives and practices since empirical studies often involve a large number of contextual factors and are hampered by the long temporal scales involved (Duncker et al., 2012;Rodríguez-Ortega et al., 2014). Furthermore, there is a scarcity of studies focusing on several ES categories and management alternatives that would allow to disentangle trade-offs and synergies across them. ...
... Despite agroforestry can improve erosion control to a higher extent than agriculture Jose, 2009), the contribution of the assessed SMP to this ES was lower compared to other ES evaluated. Erosion control was more influenced by transversal practices, such as extending stand rotation, rotation of livestock resting areas, and fencing tree regeneration areas to avoid soil degradation (Ruiz-Mirazo and Robles, 2012), and also by seeding understorey herbaceous species. In a similar fashion, the contribution of the SMP to the provision of cultural ES was comparatively lower, despite the potential of agroforestry for its enhancement when compared to agricultural or forest land uses (Rolo et al., 2021). ...
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Silvopastoral systems (SPS) emerge with a renewal interest in the Mediterranean for their promotion of multifunctionality through a variety of ecosystem services (ES). However, the understanding of how combined forestry and pastoral practices affect the ES delivery as well as the synergies and trade-off dynamics amongst them is still very limited. We applied the structured expert consultation Delphi method to assess the medium-term effect of relevant silvopastoral management practices (SMP) on the delivery of provision, regulation and maintenance and cultural ES in Mediterranean mid-mountain SPS in Spain. The deliberation process entailed two rounds and the Delphi panel was finally formed by 69 experts covering a broad spectrum of background and expertise. Results show that some practices, such as silvicultural treatments (e.g., thinning or coppice selection), play a multifunctional role contributing to ES delivery in bundles while some trade-offs are also identified between SMP, such as free animal grazing, and the provision of some ES. Synergies are also found between ES, such as livestock production and recreational hunting and between timber production and carbon sequestration, whereas possible trade-offs were particularly relevant between wildfire prevention and carbon sequestration. These findings can support decision-making processes towards sustainable and multifunctional silvopastoral management in the northern Mediterranean basin.
... Our results suggest that livestock can reduce fuel accumulation, contributing to the reduction of fire risk, since the grazing pressure of 3.88 sheep ha À1 day À1 can reduce the accumulated fuel loads in the study area by about 45.29%. In south-eastern Spain, Ruiz-Mirazo and Robles [64] found that livestock consumed between 33 and 68% of vegetation biomass, depending on the weather conditions of the year. ...
... Indeed, this fuel break capacity depends on the ecosystem's productivity, linked to annual rainfall. Ruiz-Mirazo and Robles [64] reported that livestock could reduce biomass by 625 kg DM ha À1 with a rainfall of 171 mm and 1250 kg DM ha À1 with precipitation of 294 mm. In our case, with 520 mm of annual rainfall, the sheep consume 1416.03 ...
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Wildfires have been an important process affecting forests and rangelands worldwide. In the Mediterranean region, wildfires burn about half a million hectares of forest and scrubland every year. Fuel loads are the main factor controlling fire risk and its propagation. The reduction of fuel loads by grazing could help to decrease the spread and intensity of wildfires in this region. This study aims to assess the contribution of sheep grazing on fuel load management and their role to the mitigation of wildfire greenhouse gas (GHG) emissions. The methodological approach is based on a simulation of the grazing pressure required to reduce a given quantity of fuel, under the assumption that if it is not consumed, it becomes fuel. Following, a simulation model was designed to estimate the total GHG emissions prevented through grazing, by reducing the risk of fire. These emissions were estimated based on the Intergovernmental Panel on Climate Change (IPCC) framework. The accumulated fuels were estimated to be 3126.65 kg dry matter (DM) ha-1 and the biomass potentially consumed by sheep was 1416.03 kg DM ha-1 yr -1 , corresponding to 45.29% of accumulated fuel loads. Our findings suggest a value of 3.88 sheep ha-1 day-1 as the ideal to reduce 4833.63 kg CO 2 eq ha-1 yr-1 of emissions, distributed between CO2 (-2221.76 kg CO2eq ha-1 yr-1 ; 45.96%), NOx (-1873.41 kg CO2eq ha-1 yr-1 ; 38.76%), CO (-454.55 kg CO2eq ha-1 yr-1 ; 9.40%), CH 4 (-186.35 kg CO2eq ha-1 yr-1 ; 3.86%) and N2O (-97.56 kg CO2eq ha-1 yr-1 ; 2%). The results of this study also underline that livestock can help to mitigate climate change in areas prone to wildfires.
... Berthet et al., 2012;Andersson et al., 2013), the effects of grazing activity on reducing the risk of wildfires and maintaining landscape heterogeneity (e.g. Ruiz-Mirazo and Robles, 2012), or the effects of farming inputs on soil fertility and carbon sequestration (e.g. Piastrellini et al., 2015;Pathak et al., 2017). ...
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... The limited CAP support to the extensive sheep farming resilience may be explained by the fact that the aids so far have been mainly tailored to support farmers' income instead of strengthening other relevant and specific functions of the FS, i.e. environmental protection and biodiversity contribution through pasture management (Casasús et al., 2007;Ruiz-Mirazo and Robles, 2012) and contribution to keep the rural areas alive (Kristensen et al., 2016). This is in line with Meuwissen et al. (2020), who found that many enhancing resilience strategies focused on the delivery of private goods. ...
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... Instead, extensive beef cattle grazing may have limited impacts on wildfire prevention (Calleja et al., 2019). Secondly, stocking rates applied should also be adapted to annual forage production, since constant grazing pressure can be inadequate during years of higher grass productivity (Ruiz-Mirazo and Robles, 2012). Temporally, grazing should aim at lowering fuel load before the arrival of the fire season (Casals et al., 2009). ...
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In recent years, we have witnessed to wildfires of unprecedented scale and duration in different regions of the world, a phenomenon that is expected to be exacerbated by climate change. Al- though a general decrease in burned areas was experienced in the Mediterranean Basin during the last 50 years, an increase of very large wildfire events was also documented, representing a poten- tial threat to human and natural systems. In this context, scholars have highlighted the potential of Agroforestry (AF) systems to contribute to fire risk reduction in Mediterranean environments. Agroforestry systems can influence the fire regime both at the farm scale, by affecting fuel load and flammability, and landscape scale, by creating a mosaic of heterogeneous land covers that reduces fire propagation. The objectives of this study are, first, to examine whether lower wildfire risk factors can be found in AF areas under simulated climate change conditions. Second, to explore the farmers’ perception of causes of fire ignition and potential adaptation strategies for wildfire management under climate change. Third, to assess whether farmers perceive agroforestry as an adaptation strategy to reduce wildfire risk in central Sardinia. This study was conducted in the Monte Pisanu forest and Campeda Plateau area in central Sardinia (Italy). Sardinia is one of the most fire-prone regions of Italy and, at the same time, the region with the richest concentration of agroforestry systems. A mixed methodology was used to achieve the study’s objectives. First, fire behaviour simulations were performed on FlamMap by using historical and simulated climatic inputs from a state-of-the-art regional climate model (Euro- CORDEX) and two climate change scenarios: a ”stabilization” scenario (RCP4.5) and a ”high emission” scenario (RCP8.5). The meteorologically based Fire Weather Index (FWI) was used to calculate the number of days exceeding the 95th percentile of the FWI to later calculate future changes in Seasonal Burn Probability. The SBP raster outputs were analysed on GIS software to spatially correlate Highest Seasonal Burn Probability (HSBP) areas to different land-use class groups and compared AF areas to other natural or semi-natural areas. Second, farmers perception were collected through a semi-structured survey conducted in central Sardinia during fall 2020. Responses were coded on Nvivo and analysed on Matlab. Qualitative results showed that no specific mention of agroforestry practices was given by farmers in the context of wildfire management. Farmers believed that fire ignitions are mostly due to deliberate causes, strongly emphasising the role of economic interests and local conflicts. The suggested adaptation measures were in line with such belief and stressed the need to improve the socio-economic context, ease local conflicts and design better policies. Results from fire behaviour simulations showed that fire susceptibility in agroforestry areas is generally lower than in shrublands and forests. However, results are highly dependent on stimu- lation parameters, namely wind direction, ignition patterns and climate change scenarios, making it difficult to give a unique assessment of SBP in agroforestry areas. Nevertheless, lower values of SBP were found in agroforestry areas under low-risk climate change scenarios, suggesting that devoting higher efforts to climate mitigation could enhance the wildfire risk reduction efficacy of agroforestry systems at the landscape scale. Although results suggested that farmers of central Sardinia might not consider agroforestry systems as a potential wildfire adaptation strategy, this study confirmed that farmers play a key role in wildfire prevention and management. In the context of climate change, efficient fire reduc- tion through agroforestry will greatly depend on the integration of such agricultural systems into wider wildfire management from the farm to the landscape and regional scale. Thus, agroforestry adoption in wildfire management will only be possible when sufficient recognition of agroforestry potential will be received from farmers, researchers and society as a whole.
... This phenomenon has implied an increase of high and dense shrublands, promoting the accumulation of biomass fuel, which is associated with high fire hazard. Several authors (Almeida and Moura 1992, Mather and Pereira 2006, Ruiz-Mirazo and Robles 2012, Mancilla-Leytón et al. 2013) have shown the existence of larger burned areas in the municipalities with the highest emigration. According to Bengtsson et al. (2000) it is important to understand natural disturbance dynamics and also their relationship with human disturbance. ...
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The mountain landscapes of northern Portugal have been modified through rural depopulation and the absence of rangeland management. As such, increased above-ground biomass and higher fire hazard resulted, as well as decreased ecosystem biodiversity. The objectives of the OpentoPreserve Interreg SUDOE project are to evaluate the effects of the combined use of prescribed fire with grazing horses, and also to develop strategies of socioeconomic valorization of this model. Concerning the evaluation of prescribed fire and grazing effects, the experimental design consisted of three plots in the Natura 2000 Alvão/Marão Site, respectively Control, Fire x Grazing, and Fire. The Fire plots were burned in early spring and vegetation percent cover and height were measured in all plots in late spring. We have implemented four transects in the three different plots, used the line intercept method and subsequently estimated vegetation volume. This methodology is also applied on Forestation of Agricultural Land with More Silviculture, Silvopasture, Innovation and Value project. Concerning socioeconomic valorization, the stakeholders related to the native horse breed, were interviewed and a focus-group was held. The study intends to identify both the benefits resulting from the adoption of a management system that includes the native horse breed, named Garrano, and the main weaknesses related to environmental, economic and social sustainability. Initial results for total vegetation in each plot show a high reduction in vegetation percent cover and its volume in the burned plots (33.5% and 268.3 m 3 ha-1) in comparison to the control plot (183.7% and 12862.5 m 3 ha-1). Furthermore, a fast recovery was observed in July, mainly of the Pterospartum tridentatum shrub species. Interviews and focus-group results shows the important role of these grazing animals in vegetation control as well as in other ecosystems services, involving an environmental and a socioeconomic dimension. A strategy to value contribution to the economy of agricultural holdings has been proposed.
... Grazing helps to maintain and preserve the natural resources contributing to keep soil quality (Peco et al., 2017) and biodiversity by maintaining landscape heterogeneity (Ornai et al., 2020;Rodríguez-Ortega et al., 2014;Silva et al., 2019). Extensive livestock activity is also important to prevent forest fires by keeping the area clean from dry biomass (weeds and scrubs), which act as fuel in Mediterranean areas Ruiz-Mirazo and Robles, 2012). Grazing activities also provide recreational areas demanded by society (Bernués and Olaizola, 2012) and keep the rural areas attractive. ...
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Finding pathways to more sustainability and resilience of farming systems requires the avoidance of exceeding critical thresholds and the timely identification of viable alternative system configurations. To serve this purpose, the objective of this paper is to present a participatory, integrated and indicator-based methodology that leads researchers and farming system actors in six steps to a multi-dimensional understanding of sustainability and resilience of farming systems in the future. The methodology includes an assessment of current performance (Step 1), identification of critical thresholds whose exceedance can lead to large and permanent system change (Step 2), impact assessment when critical thresholds are exceeded (Step 3), identification of desired alternative systems and their expected improved performance of sustainability and resilience (Step 4), identification of strategies to realize those alternative systems (Step 5), and an assessment on the compatibility of alternative systems with the developments of exogenous factors as projected in different future scenarios (Step 6). The method is applied in 11 EU farming systems, and the application to extensive sheep production in Huesca, Spain, is presented here, as its problematic situation provides insights for other farming systems. Participants in the participatory workshop indicated that their farming system is very close to a decline or even a collapse. Approaching and exceeding critical thresholds in the social, economic and environmental domain are currently causing a vicious circle that includes low economic returns, low attractiveness of the farming system and abandonment of pasture lands. More sustainable and resilient alternative systems to counteract the current negative system dynamics were proposed by participants: a semi-intensive system primarily aimed at improving production and a high-tech extensive system primarily aimed at providing public goods. Both alternatives place a strong emphasis on the role of technology, but differ in their approach towards grazing, which is reflected in the different strategies that are foreseen to realize those alternatives. Although the high-tech extensive system seems most compatible with a future in which sustainable food production is very important, the semi-intensive system seems a less risky bet as it has on average the best compatibility with multiple future scenarios. Overall, the methodology can be regarded as relatively quick, interactive and interdisciplinary, providing ample information on critical thresholds, current system dynamics and future possibilities. As such, the method enables stakeholders to think and talk about the future of their system, paving the way for improved sustainability and resilience.
Chapter
Understanding the effects ofClimateclimate changeClimate change and human activities on fragile mountain ecosystems is necessary to successfully managing these environments under future climateClimate scenarios (e.g., global warming, enhanced aridity). This can be done through the study of paleoecological records, which can provide long paleoenvironmental databases containing information on how ecosystems reacted toClimateclimate changeClimate change and human disturbances before the historical record. These studies can be particularly interesting when focusing on especially warm and/or dry past climatic phases. Biotic (pollen, charcoal) and abiotic (physical, geochemistry) analyses from wetland sediment records from the Sierra NevadaSierra Nevada, southern SpainSpainrecordSouthern spain changes in vegetation, fire historyHistory and lake sedimentation since ~11,700 years (cal yr BP). This multiproxy paleoecological study indicates that maxima in temperatureTemperature and humidity occurred in the area in the Early and Middle HoloceneHolocene, with a peak in precipitationPrecipitation between ~10,500 and 7000 cal yr BP. This is deduced by maxima in water runoff, the highest abundance of tree species and algae and high total organic carbon values recorded in the alpine wetland’s sedimentary records of the Sierra NevadaSierra Nevada during that time period. In the last 7000 cal yr BP, and especially after a transition period between ~7000 and 5000 cal yr BP, a progressive aridification process took place, indicated by the decrease in tree species and the increase in xerophytic herbs in this region and a reduction in water runoff evidenced by the decrease in detritic input in the wetland sedimentary records. An increasing trend inSaharan dustSaharan dust depositionSaharan dust deposition in the Sierra NevadaSierra Nevada wetlands is also recorded through inorganic geochemical proxies, probably due to a coetaneous loss of vegetation cover in North Africa. The process of progressive aridification during the Middle and Late HoloceneHolocene was interrupted by millennial-scale climatic oscillations and several periods of relative humid/droughty conditions and warm/cold periods have been identified in different temperatureTemperatureand/or precipitationPrecipitation proxies. Enhanced human impactHuman impact has been observed in the Sierra NevadaSierra Nevada in the last ~3000 cal yr BP through the increase in fires, grazing, cultivation, atmospheric pollution as well as reforestation by Pinus and the massive cultivation of Olea at lower altitudes.
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Local ecological knowledge systems have been the basis of Sierra Nevada’sSierra Nevadasocial-ecological systemSocial-ecological system, which has co-evolved over more than ten centuries until nowadays, based on the knowledge, practices, and innovations deriving from the relationship between people and the ecosystems on which they depend. In Sierra NevadaSierra Nevada, this co-evolution is greatly influenced by the traditional water managementTraditional water management system, generating a “cultural landscapeCultural landscape.” However, during the twentieth-century Sierra NevadaSierra Nevada’s social-ecological systemSocial-ecological system was affected by diverse drivers of changeDrivers of change such as climateClimatechangeClimate change, rural exodus, land-use change, and conservationConservation government policies, which are threatening its stability and the transmission of the related local ecological knowledge. Local ecological knowledge on water management, traditional agricultural systems, and knowledge related to grazing and cattle raising should be included in the co-managementAdaptive co-management of the territory and representatives of this knowledge should be involved and collaborate with administration and researchers developing adaptive plants to reduce negative impacts of global changeGlobal change.
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"Measuring Biological Diversity assumes no specialist mathematical knowledge and includes worked examples and links to web-based software. It will be essential reading for all students, researchers, and managers who need to measure biological diversity."--BOOK JACKET.
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