© The Authors, 2024, Published by the Universidad del Zulia*Corresponding author: saidaalgerie3@gmail.com
Keywords:
Asteraceae
Floristic richness
Grazing intensity
Herbaceous phytomass
Total nitrogen
Eect of grazing on the composition and oristic diversity during fallow at El-Tarf, Algeria
Efecto del pastoreo en la composición y la diversidad orística durante el barbecho en El-Tarf,
Argelia
Efeito do pastejo na composição e na diversidade orística durante o pousio em El-Tarf, Argélia
Saida Matallah
1
*
Fouzi Matallah
2
Rev. Fac. Agron. (LUZ). 2024, 41(1): e244110
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v41.n1.10
Crop production
Associate editor: Professor Juan Vergara-López
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela
1
University Chadli Bendjedid –El-Tarf, Faculty of Natural
and Life Sciences, Department of Agronomy, Algeria.
2
University Chadli Bendjedid –El-Tarf, Faculty of Natural
and Life Sciences, Department of Veterinary, Algeria.
Received: 12-12-2023
Accepted: 21-02-2024
Published: 13-03-2024
Abstract
In the El-Tarf region, located in northeastern Algeria, fallow lands are
frequently used as grazing grounds for sheep ocks, where they are left all
day with a signicant grazing load. Limited studies conducted to assess the
eects of grazing have yielded varied and sometimes contradictory results,
thus underscoring the need for reliable local data. The study aims to assess
the impact of grazing on the oristic richness, diversity, production, and
chemical composition of fallow lands in the El-Tarf region (northeast Algeria).
Measurements were taken during the optimal vegetation period from March
to June over a period of 2 years (2019 and 2020). The experimental design
included a single factor: grazing intensity (no grazing, moderate grazing, and
intense grazing).The results indicated that grazing reduced oristic richness
and diversity (Maximum Diversity, Shannon and Weaver Index, Evenness
Index), but it did not have an eect on coverage. The non-grazed fallow land is
richer, hosting 23 herbaceous species distributed among 8 botanical families,
with the most represented being Asteraceae (39 %), followed by Poaceae (26
%). The Fabaceae, on the other hand, display a more modest representation,
accounting for only 13 %.Grazing also decreased signicantly the biomass
and total aboveground herbaceous phytomass, with improvements noted in
non-grazed conditions, recording values of 3.80 t.DM.ha
-1
and 1.77 t.DM.
ha
-1
, respectively. In addition, grazing had a signicant impact on chemical
composition, with the highest values recorded for moderate grazing, reaching
14.7 % for total nitrogen content and 11.66 % for mineral content.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2024, 41(1): e244110 January-March. ISSN 2477-9407.2-7 |
Resumen
En la región de El-Tarf, ubicada en el noreste de Argelia, las tierras
en barbecho son frecuentemente utilizadas como pastizales para
rebaños de ovejas, donde pasan todo el día con una carga signicativa
de pastoreo. Los estudios limitados realizados para evaluar los efectos
del pastoreo han arrojado resultados variados y a veces contradictorios,
destacando así la necesidad de contar con datos locales conables.
El estudio tiene como objetivo evaluar el impacto del pastoreo en
la riqueza orística, diversidad, producción y composición química
de tierras en barbecho en la región de El-Tarf (noreste de Argelia).
Las mediciones se realizaron durante el período óptimo de vegetación
de marzo a junio durante un período de 2 años (2019 y 2020). El
diseño experimental incluyó un solo factor: intensidad de pastoreo
(sin pastoreo, pastoreo moderado y pastoreo intenso). Los resultados
indicaron que el pastoreo redujo la riqueza orística y la diversidad
(Diversidad Máxima, Índice de Shannon y Weaver, Índice de
Equidad), pero no tuvo efecto en la cobertura. La tierra en barbecho
no pastada es más rica, albergando 23 especies herbáceas distribuidas
entre 8 familias botánicas, siendo las más representativas Asteraceae
(39 %), seguidas por Poaceae (26 %). Por otro lado, las Fabaceae
muestran una representación más modesta, representando solo el 13
%.El pastoreo también disminuyó signicativamente la biomasa y
la tomasa herbácea total sobre el suelo, con mejoras observadas en
condiciones no pastadas, registrando valores de 3.80 t.MS.ha
-1
y 1.77
t.MS.ha
-1
, respectivamente. Además, el pastoreo tuvo un impacto
signicativo en la composición química, con los valores más altos
registrados para pastoreo moderado, alcanzando el 14.7 % para el
contenido total de nitrógeno y el 11.66 % para el contenido mineral.
Palabras clave: Asteraceae, riqueza orística, intensidad de pastoreo,
tomasa herbácea, nitrógeno total.
Resumo
Na região de El-Tarf, localizada no nordeste da Argélia, as terras em
pousio são frequentemente utilizadas como pastagens para rebanhos
de ovelhas, onde cam o dia todo com uma carga signicativa de
pastoreio. Estudos limitados conduzidos para avaliar os efeitos do
pastoreio têm produzido resultados variados e às vezes contraditórios,
destacando assim a necessidade de dados locais conáveis. O
estudo tem como objetivo avaliar o impacto do pastoreio na riqueza
orística, diversidade, produção e composição química das terras
em pousio na região de El-Tarf (nordeste da Argélia). As medições
foram realizadas durante o período de vegetação ótimo de março a
junho ao longo de um período de 2 anos (2019 e 2020). O desenho
experimental incluiu um único fator: intensidade de pastoreio (sem
pastoreio, pastoreio moderado e pastoreio intenso). Os resultados
indicaram que o pastoreio reduziu a riqueza orística e a diversidade
(Diversidade Máxima, Índice de Shannon e Weaver, Índice de
Equidade), mas não teve efeito na cobertura. A terra em pousio não
pastada é mais rica, hospedando 23 espécies herbáceas distribuídas
entre 8 famílias botânicas, sendo as mais representadas as Asteraceae
(39 %), seguidas pelas Poaceae (26 %). As Fabaceae, por outro lado,
exibem uma representação mais modesta, representando apenas 13
%. O pastoreio também diminuiu signicativamente a biomassa e a
tomassa herbácea total acima do solo, com melhorias observadas
em condições não pastadas, registrando valores de 3,80 t.MS.ha
-1
e 1,77 t.MS.ha
-1
, respectivamente. Além disso, o pastoreio teve um
impacto signicativo na composição química, com os valores mais
altos registrados para pastoreio moderado, alcançando 14,7 % para o
conteúdo total de nitrogênio e 11,6 % para o conteúdo mineral.
Palavras chave: Asteraceae, tomassa herbácea, intensidade de
pastejo, nitrogênio total, riqueza orística.
Introduction
At the global scale, several authors have examined the repercussions
of grazing on pastoral resources. They have also been the subject
of numerous controversies due to contradictory results. Frequent
and intensive grazing signicantly inuences ecosystem dynamics
and, consequently, has a substantial impact on species richness and
diversity (Herrero-Jáuregui and Oesterheld, 2018). In Marocco,
Chebli, et al., (2021) emphasized in their study that overgrazing by
sheep explains, the disappearance of pastoral species. Dan Gomma et
al. (2019) have shown that the increase in the number of animals in
grazing areas exerts considerable pressure on forage resources. This
results in a decrease in productivity, biodiversity, the disappearance
of quality forage species, and the proliferation of invasive species that
are little or not appreciated. In contrast to previous results, Davies
(2022) show that the eect of grazing is characterized over time by an
increase in oral richness. According to analyses, controlled livestock
grazing, at light to moderate intensities, can have positive eects on
prairie vegetation compared to the total absence of grazing (Zhang et
al., 2023). In Algeria, various studies have been published regarding
the impact of grazing on vegetation evolution, mainly focusing on
steppe areas. These research eorts have assessed the extent of the
consequences of overgrazing on vegetation dynamics (Boukerker et
al., 2021). In the extreme northeast of Algeria, specically in the El-
Tarf region with a humid climate, grazing on fallow land remains
a vibrant tradition, constituting an integral part of local production
systems. The practice of grazed fallow is particularly widespread,
especially when the production system is linked to extensive sheep
farming (Matallah and Abbas, 2015), with a signicant stocking rate.
The impact of disturbance factors, especially sheep grazing, on the
oristic and structural characteristics of the herbaceous layer remains
unexplored in this region. This activity is increasingly threatened due
to the degradation of climatic conditions, which exert an unfavorable
inuence on the productive capacities of natural pastures (Djohy et
al., 2022). Therefore, the objective of this study was to evaluate how
grazing specically aects the composition and oristic diversity,
production, and chemical composition of fallow lands. As an
integral part of grazing lands in the context of feeding a sheep herd
exceeding 120.000 heads, it is expected that the quantity of grass
decreases, but the quality of the grass proves to be higher compared
to non-grazed areas. To test this hypothesis, our study focuses on
evaluating the impact of grazing on the composition and oristic
diversity, production, and chemical composition of fallow lands.
The impact of disturbance factors, especially sheep grazing, on the
oristic and structural characteristics of the herbaceous layer remains
unexplored in this region. This activity is increasingly threatened due
to the degradation of climatic conditions, which exert an unfavorable
inuence on the productive capacities of natural pastures (Djohy et
al., 2022). The analysis of temperature trends in Algeria reveals an
upward trend for both minimum and maximum temperatures across
all stations in the northern part of the country, and this trend continues
to the present day. Over the past two decades, there has been a
more pronounced increase in maximum temperatures compared to
minimum temperatures. As for precipitation, a decrease is observed
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Matallah and Matallah. Rev. Fac. Agron. (LUZ). 2024 40(1): e2441103-7 |
in autumn and winter in the North, as well as in spring in the East of
Algeria.
Materials and methods
Study area
Our study focuses on the El-Tarf region, located in the extreme
northeast of Algeria. In this region, the livestock farming system is
primarily extensive to semi-intensive, and the majority of the feed
comes essentially from natural forages derived from fallow lands,
pastures, and meadows (Arbouche et al., 2016). According to the
Emberger climatogram, it falls within the sub-humid Mediterranean
bioclimatic zone with a warm winter. Before embarking on our
eldwork, we conducted surveys with the agricultural services
department of El-Tarf to gather information on animal production,
forage resources, and grazing intensity in the region. In total, we
interviewed 92 sheep farmers, all of whom own fallow lands intended
for grazing, selected randomly from the list provided by agricultural
services. We observed that fallow land management primarily
depends on farmers’ practices, who follow two management models:
-Crop - fallow without grazing - crop.
-Crop - fallow grazing period - crop.
In our study, we selected three fallow grazing treatments as
described in table 1:
Table 1. Annual grazing balance on grazed fallows (2 years).
Grazing Intensity Average Stocking Rate per Hectare
G0 (no grazing) 0
G1 (moderate grazing) 1.5
SLU.ha
-1
(ovine)
G2 (intensive grazing) 4.5
SLU.ha
-1
(ovine)
SLU: Standard Livestock Units
The selected fallow lands share the same general ecological
conditions (geographical coordinates, altitude, slope, exposure, and
soil texture).
Measurements on vegetation
The measured parameters were conducted during the optimal
vegetation period from March to June, and over a period of 2 years
(2019 and 2020).
Floristic composition (Number of families and species)
Floristic surveys are conducted in a minimum area of 100 m
2
(10
m x 10 m) per fallow (G0, G1, G2) with 5 repetitions. Quantitative
measurements were carried out using the “point quadrats” aligned
technique (Daget and Poissonet, 1971). This method involves
extending a graduated tape 10 cm above the herbaceous vegetation with
equidistant points at 10 cm intervals. Using a needle, the frequency of
dierent elements (species, bare ground, etc.) was recorded. In each
survey, two lines of 10 points are positioned along the diagonals of
the study area. This survey was complemented by a comprehensive
inventory of plant species across each pasture. Phytosociological
surveys were carried out randomly employing the Braun-Blanquet
method (1951) with one-square-meter quadrats positioned at the
center of each plot. The quantity of surveys conducted was contingent
upon the visually ascertained diversity of the vegetative cover; the
more heterogeneous the cover, the greater the number of surveys, and
conversely. The herbaceous species present were identied on-site
with the assistance of an expert from El-Kala National Park (El-Tarf).
The nomenclature we adopted is that of the synonymic index of North
Africa by Dobignard and Chatelain (2010–2013).
Floristic Diversity
Diversity and evenness indices are dened as follows (Ojoatre,
2024):
*Max diversity: H max=log
2
S
*Shannon-Wiener’s index of species diversity: H′ = -∑((n
i
/N) ×
log
2
(n
i
/N))
*Evennes: E = H′/ Hmax
Where: n
i
is the abundance of species i in the sample, and N is the
total abundance. H’ varies between 0, in the case where the population
consists of only one species. S: number of species
Recovery of the vegetation
Herbaceous covering was assessed using the method of linear
surveys (point-quadrats). Two 10-meter lines, parallel and located in
the center of each plot, were surveyed (Daget and Poissonet, 1971).
On each line, observations were made every 20 centimeters, which
corresponds to a sampling of N = 100 points per plot.
Aboveground herbaceous phytomass
By denition, this is the mass expressed in dry matter of both
living matter (biomass) and standing dead matter (necromass). The
measurement of the total aboveground phytomass was conducted
using the whole-plant harvesting method (Cherednichenko et al.,
2021). This involves cutting the aboveground plant material at ground
level within 1 m² squares with 10 replicates per unit. Samples were
collected species by species by hand, then placed in paper bags and
weighed using an electronic scale in a cool environment. They were
later transported to the laboratory where they were weighed again to
determine the dry matter content. The results in dry weight (dried at
60 °C to constant weight) include total phytomass, necromass, and
biomass.
Chemical composition
Forage samples were ground to determine their chemical
composition (dry matter, mineral matter, total nitrogen content, and
crude cellulose) using AOAC methods (1990).
Statistical analysis
The eect of grazing on the studied parameters was subjected to
analysis of variance. The Newman-Keuls test was used to determine
signicant dierences between group means. Data were assessed
for normality to ensure that the criteria followed ANOVA rules.
Linear mixed models (LMM) were employed for data with a normal
distribution or data that could be transformed to achieve a normal
distribution. The model used is in the following form: Y
ij
=µ + P
i
+ eij.
With: Y
ji
= the measured variable, P
i
= xed eect of the plot (i=1-3),
and e
ij
=the error.
Results and discussion
Eect of grazing on the oristic composition of fallow lands
Our results are in line with the conclusions published in studies
on Algerian arid landscapes (Amrani and Chehma, 2020). Ungrazed
fallow lands are richer, containing 23 herbaceous species (P<0.05)
belonging to 8 botanical families (table 2 and 3), with Asteraceae
being the most represented (39 %), followed by Poaceae (26 %).
The dominance of Asteraceae is attributed to the morphological,
anatomical, and physiological characteristics of the species (Hussain,
2020). In our context, it is plausible to assume that grazing decreases
the percentage contribution of Poaceae due to consumption by
animals (gure 1).
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Rev. Fac. Agron. (LUZ). 2024, 41(1): e244110 January-March. ISSN 2477-9407.4-7 |
Table 2. Impact of grazing intensity on oristic composition.
Number of species Number of families
G0 (3 plots) 23
a
8
a
G1(3 plots) 17
b
6
a
G2(3 plots) 12
ab
7
a
Probability grazing(P) * NS
*
Signicant (P < 0.05);NS : non-signicant (P > 0.05).
a, b
the means followed by the same letter(s) constitute a statistically homogeneous group at a signicance level of
0.05, according to the Newman-Keuls test
Table 3. List of species encountered in the three types of fallow.
Families Species Common names G0 G1 G2
Asteraceae
Filago pygmaea
Pygmy cottonrose + + -
Lamiaceae
Mentha pulegium L
Pennyroyal - + -
Primulaceae
Lysimachia foemina
Loosestrife + + +
Poaceae
Elymus repens
Couch grass + + +
Plantaginaceae
Plantago lanceolata
Ribwort plantain + - -
Malvaceae
Malva sylvestris
Common mallow - + -
Fabaceae
Trifolium tomentosum L
Woolly clover + + +
Asteraceae
Lapsana communis
Nipplewort + - -
Euphorbiaceae
Euphorbia helioscopala L
Sun spurge + - -
Asteraceae Lactuca serriola L Prickly lettuce + - -
Fabaceae
Medicago sativa
Alfalfa + + +
Plantaginaceae
Plantago major
Greater plantain + - +
Asteraceae
Leucanthemum vulgare Lam
Oxeye daisy + - +
Fabaceae
Vicia hirsuta L
Hairy vetch + + -
Ranunculaceae
Ranunculus repens L
Creeping buttercup + - +
Fabaceae
Coronilla varia L
Crownvetch - + -
Boraginaceae
Cerinthe major
Honeywort - - +
Asteraceae Taraxacum ocinale L Dandelion + + -
Asteraceae
Galactites tomentosa
Woolly milk thistle + - +
Poaceae
Anthoxanthum odoratum
Sweet vernal grass + + -
Fabaceae
Melissa ocinalis
Lemon balm - + -
Asteraceae
Sonchus oleraceus L
Common sowthistle + + -
Poaceae
Bromus rubens L.
Red brome + + +
Poaceae
Bromus tectorum
Cheatgrass + - -
Poaceae
Avena sterilis
Wild oat + - -
Asteraceae
Picris echioides L
Bristly oxtongue + + +
Asteraceae
Galactites duriaei
Soft thistle + - +
Poaceae
Phalaris paradoxa
Hooded canarygrass + - -
Fabaceae
Trifolium campestre
Field clover - + -
Poaceae
Festuca paniculata
Slender fescue - + -
+: species observed in the surveys; - : species not observed in the surveys.
The dominance of Asteraceae is attributed to the morphological,
anatomical, and physiological characteristics of the species (Zhang
et al., 2023). Defensive strategies, including spines and secondary
compounds, provide these family members with a signicant
mechanism against grazing, leading to their prevalence. The same
authors further add that Asteraceae exhibit signicant adaptability to
local environmental conditions, the study region undergoes noticeable
climatic changes, marked by a substantial increase in temperature over
the years and a pronounced decrease in precipitation (Bouhraoua et
al., 2019). This climatic evolution accentuates the system’s fragility,
with less frequent precipitation and persistent irregularity. These
variable climatic conditions directly impact the dynamics of Asteraceae
species, compelling these plants to adjust their adaptive strategies to
thrive in a changing environment. Thus, the combination of distinctive
morphological features and defense mechanisms of Asteraceae,
coupled with their remarkable adaptability to local conditions, makes
them key players in the ecological dynamics of the region. These
factors underscore the importance of a thorough understanding of the
physiological responses and rhizospheric interactions of these plants in
the face of contemporary environmental challenges.
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Matallah and Matallah. Rev. Fac. Agron. (LUZ). 2024 40(1): e2441105-7 |
Figure 1. Botanical family composition in response to grazing
intensity on fallow lands. G0: no grazing; G1: moderate
grazing; G2: intensive grazing; %: Contribution of each
family to the total number of species
It also appears that moderate grazing favors legumes (29 %). This
specic enrichment resulting from moderate grazing can be attributed
to several factors. Firstly, the feces of animals in moderate grazing
bring essential nutrients to the soil, thus promoting fertility and
nutrient availability for plants. Additionally, moderate grazing can
lead to the importation of seeds, especially those of legumes, through
the movement of animals from one place to another. This could be
due to the likelihood that grazing areas with higher grazing intensities
may have caused the spread of less palatable species. More palatable
species may disappear due to frequent livestock grazing on highly
palatable grasses and legume species (Zainelabdeen et al., 2020). This
could be attributable to the association ability between grasses and
legumes. Grasses, being taller, strongly compete for solar energy, thus
favoring Fabaceae in areas with moderate grazing. Legumes benet
from reduced competitive pressure and increased light resources or
nutrient input (P and K) through urine and feces. Herbivore grazing
reduces shading caused by grasses, allowing plants to thrive. The
noted variation among the examined pastures underscores the positive
impact of moderate stocking rates on the growth of specic species,
including Mentha pulegium (L.) and Malva sylvestris (L.), aliated
with the Lamiaceae and Malvaceae families, correspondingly. In
heavily grazed pastures, a notable portion of the plant life, comprising
Lysimachia foemina, Plantago major, Ranunculus repens (L.), and
Cerinthe major, is distinctly characterized, with one representative
from each family. This highlights the nuanced dynamics of plant
development inuenced by varying grazing intensities. According
to Davies (2022), protection is expected to enhance the increase in
the number of species due to the diversication of ecological niches.
However, intensive livestock pressure can lead to soil resource
degradation and a decrease in oral richness, while also promoting the
emergence of unappealing species (Zhang et al., 2023). Furthermore,
this excessive overgrazing pressure can contribute to a desertication
process. Indeed, it results in the loss of the topsoil, which provides
protection and coverage for the soil. This leaves the soil vulnerable to
wind and water erosion, a reduction in water retention capacity, soil
compaction, as well as the loss of mineral content and soil nutrients.
According to Davies (2022), grazing can have a direct impact on
plants by causing tissue loss through defoliation or trampling. In
contrast to our results, in Mediterranean Pastures, Oikonomou et al.,
39%
13%
26%
22%
28%
29%
24%
19%
33%
17% 17%
33%
Asteraceae Fabaceae Poaceae Other Families
G 0 G 1 G 2
(2023) demonstrated that oral richness could increase even with
high grazing intensity if the system is nutrient-rich after grazing to
facilitate the development of certain species. However, it has not
been possible to precisely determine the critical livestock stocking
threshold allowing these benecial eects. With vegetation subjected
to continuous year-after-year grazing, as in our conditions, it can be
assumed that the plant response to defoliation will depend on each
species’ grazing tolerance level. In this case, it is crucial to determine
whether the species favored by grazing are grazing-tolerant or not.
Grazing can also alter the abiotic environment (light, fertility) of the
plant and the biotic environment (competition intensity) (Poorter
et al., 2023). In the long term, appetizing and unappetizing plants
can be consumed by animals, leading to complete disappearance of
vegetative cover.
Eect of grazing on oristic diversity indices
The diversity indices (table 4) have experienced a signicant
decrease as the stocking rate increased. Similar ndings were
observed in Husain et al. (2019) study on alpine meadows.
Table 4. Impact of grazing on diversity indices.
Floristic diversity indices H max H E
G0 4.70 ± 0.46
a
2.82 ± 3.50
a
0.60 ± 3.40
a
G1 4.68 ± 2.40
a
2.67 ± 7.40
a
0.57 ± 2.23
a
G2 3.66 ± 3.34
b
1.72 ± 3.20
b
0.47 ± 2.50
b
P * * *
*
Signicant (P < 0.05).
a,b
the means followed by the same letter(s) constitute a
statistically homogeneous group at a signicance level of 0.05, according to the
Newman-Keuls test
The Shannon-Weaver index (H’) varies signicantly between
moderate and intense grazing (P < 0.05), but no signicant dierence
is observed between moderate and no grazing pressure levels. In
our conditions, this suggests that moderate grazing has preserved
pasture diversity, while overgrazing has led to the deterioration of
this forage resource. Hempson et al. (2022) reported in the Sahel
that intensive grazing leads to the dominance of a small number
of species (low H’). According to the same authors, the decrease
in this index is a consequence of grazing. Overgrazing results in a
clear domination of vegetation by one species or a small number of
species; in contrast, other authors (Yerou et al., 2022) in dierent
agro-ecological zones noted that the Shannon diversity index is
higher in heavily grazed pastures. In our conditions, grazing exerts
selective pressure on vegetation, thus inuencing oral composition
and diversity. Therefore, intensive grazing acts as a lter to favor
or eliminate certain species. Only species adapted to environmental
conditions (ltering process) will form the species community
encountered on fallow lands. The study highlights that the moderately
grazed fallow land (G1) is characterized by the presence of Mentha
pulegium L. Malva sylvestris, Coronilla varia L. Melissa ocinalis
and Trifolium campestre. This observation can be attributed to the
strong adaptability of these species to moderate levels of grazing
and trampling, as emphasized by Sitou et al. (2021). However,
these species also appear to exhibit tolerance to a certain level of
disturbance. This tolerance may be linked to specic life traits, such
as the annual nature, survival capacity, and germinative power. It is
important to note that among these mentioned species, three of them
do not seem to be appreciated by sheep.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2024, 41(1): e244110 January-March. ISSN 2477-9407.6-7 |
Eect of grazing on herbaceous plant cover and total
herbaceous epigeous phytomass
Unlike the studies conducted by Davies (2022), grazing did not
have a signicant eect on herbaceous plant cover (table 5); it remains
below 50 % in all three grazing types. Studies conrm that an increase
in animal stocking rate beyond the pastoral balance threshold leads to
a reduction in cover, phytomass, and hectare productivity (Hachmi et
al., 2018).
Table 5. Eect of grazing on overall cover.
G0 G1 G2
p
Herbaceous plant cover (%) 30.0 ± 8.40 30.2 ± 9,30 30.3 ± 11.20 NS
Total phytomass
(t.DM.ha
-1
)
3.80 ± 7.40
a
3.10 ± 5,30
a
2.58 ± 2.40
b
*
Biomass (t.DM.ha
-1
) 1.77 ± 2.50
a
1.63 ± 7,20
a
1.38 ± 2.30
b
*
*
: signicant (P < 0.05); NS: not signicant (P > 0.05).
a, b
the means followed by the
same letter(s) constitute a statistically homogeneous group at a signicance level
of 0.05, according to the Newman-Keuls test.
They noted that vegetation cover is inuenced not only by animal
consumption but also by the behavior of each plant species after
grazing, as well as the heterogeneity of the environment. Grazing
signicantly reduces biomass and phytomass, which are more
substantial in non-grazed conditions (table 5). This result is consistent
with the ndings of Yerou et al. (2022). By consuming certain
species, animals can decrease or eliminate biomass. They can also
disrupt the development of sexually reproducing species. It can be
assumed that trampling by animals may also signicantly aect plant
tissues, leading to the death of part or the entire plant. Similarly, the
study by Yé et al. (2016) suggests that browsing results in a notable
decrease in aboveground biomass.
Eect of grazing on the chemical composition of fallow elds
Regardless of conditions, grazing increases the nitrogen content
(P < 0.05) (table 6). In the absence of nitrogen fertilization, the TN
content of the grass depends mainly on the nitrogen input from the soil
and, to a lesser extent, on the nitrogen return from animal excrements
(Yerou et al., 2023).
The TN level is higher under moderate grazing (14.7 %) (table
5) and remains above the critical crude protein utilization rate of 7
% (Yerou et al., 2023). This dierence is likely related to its oristic
richness in Fabaceae (29 %), which have a high protein content.
This hypothesis justies a study of the chemical composition of each
herbaceous species. Godinot et al. (2022) showed that nitrogen levels
are always higher in grazed situations at the end of winter. According
to them, animals graze on average younger leaves than those observed
in protected areas since grazing occurs daily. The average value
recorded under moderate grazing is signicantly higher than the
values reported by Chaker Houd et al. (2020), who worked in Algeria
(16,5 %, 17,4 %, 26,7 %), and those of El-Housni et al., (2013), who
found an average of 14.57 % in Morocco.
Grazing also reduced the crude ber content. In non-grazed
environments, species are richer in plant walls to colonize the vertical
environment. However, in intensively grazed environments, the
reduction in size is an avoidance phenomenon of grazing (Bricarello
et al.,2023). The average value recorded under no grazing (26.5 %) is
higher than the values observed by El-Housni et al. (2013) (25.26 %
- 25.47 %). Thus, we reported that grazing had a signicant eect on
the levels of mineral matter (MM) and dry matter (DM), as observed
by Amrani and Chehma (2020). Regardless of the intensity of grazing,
the observed values of MM are lower than those indicated by Chaker
et al. (2020), who conducted a comparison between grazed and
cultivated fallows. It is noteworthy that DM values are the lowest in
non-grazed fallows, but generally do not exceed the results reported
in the meadows of the study area (Arbouche et al., 2016).In the study
area, it is challenging to compare these results with those of other
authors due to the scarcity of literature on this subject.
Conclusion
This study, conducted on the eects of grazing on the herbaceous
layer of fallow lands in the El-Tarf region (northeast Algeria),
revealed several ndings:
The number of species decreases with increasing grazing intensity;
Grazing leads to a reduction in diversity indices, although no
signicant dierence was observed between moderate and no grazing
pressure levels;
Grazing does not have a signicant eect on herbaceous vegetation
cover, but it reduces the biomass and total phytomass.
The highest values in nitrogen and mineral matter are recorded
under moderate grazing.
These ndings could guide more applied research aiming to ensure
the sustainability of pastoral systems in the region. While grazing
does not completely destroy vegetation, excessive grazing could be
detrimental if the system becomes nutrient-poor after grazing, which
could facilitate the development of certain species.
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G0
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