Floristic and phytoecological diversity of Holm Oak Quercus ilex forests in the Belezma Massif Biosphere Reserve, North-East Algeria

The holm oak is a species that forms interesting stands in the Belezma National Park (PNB). Studying it has allowed us to understand it’s ecological and phytoecological characteristics. Despite the importance of this species, individual trees remain exposed to multiple threats. Surveys were carried out at the level of the massifs of Kassrou and Om rkhaa which enabled us to carry out the floristic groups of the Holm oak. The study area is characterized by high floristic diversity, with 120 plant species belonging to 106 genera and 34 families, 46 of which are not included in the list of flora of the Belezma National Park. The most dominant families are Asteraceae (32 species; i.e., 27%) and Fabaceae (13 species; i.e., 11%), which are also families that are frequently found in Algeria, particularly in the Mediterranean region. The study of the phytogeographical spectrum shows that the field stations studied are dominated by the Mediterranean element (75%, 58%). Analysis of the biological types revealed the predominance of hemicryptophytes (30.33%). Therophytes were present with a high percentage at the two study sites (21%, 32%); the disturbance indices were respectively 46%, and 50%, showing high anthropogenic pressure. It is important to take the necessary measures for the preservation and conservation of this precious heritage.


Introduction
Although the great floristic richness and high biogeographical interest of the Mediterranean basin are now highlighted on a global scale (MYERS MÉDAIL & MYERS, 2004), the plant biodiversity of many territories still remains poorly known. In Algeria, the holm oak Quercus ilex has been eliminated and replaced by heliophilous vegetation, champhytes adapted to fire, or by ephemeral therophytes, which dont preserve the soils from erosion (DAHMANI, 1997). Although, the oak groves ecosystem in the Belezma forest is an area of great ecological and socio-economic value, the classification of the Belezma National Park as a Biosphere Reserve does not protect it from threats due mainly to overexploitation (overgrazing, fires, etc.) and climate change. According to SMAIHI ET AL. (2017), the diachronic analysis showed that the regression of the holm oak, linked to fires, favoured the progression of the Pinus halepensis and the Juniperus phoenicea. In connection with the degradation of this forest ecosystem, it is worth mentioning that the pressure exerted on the oak forest of the Belezma National Park for domestic needs and livestock grazing is causing it to transition into a lighter formation with a tendency towards a steppe-like environment. This generally regressive dynamic is reflected in phenomena such as overgrowth (matorralisation), invasion by steppe species (steppisation), and invasion by annual species (therophytisation) as defined by BARBERO . On the other hand, BOUKERKER (2016) states that the cedar forest presents a regressive dynamic towards lawns with thorny xerophytes and that the whole vegetation of the park is degrading due to the effect of anthropic actions and that the stands of Atlas cedar of Belezma are becoming degraded with a rise of holm oak.
Despite the diversity and richness of this ecosystem, only a few studies have been undertaken in this area. Among these scientific works, phytosociological studies are the most predominant (ABDESSEMED, 1981;YAHI ET AL., 2008). The main aim of this study, was to develop a conservation starategy for the oak forest ecosystems in the Belezma National Park, by establishing the state of the surfaces occupied by Quercus ilex and the floristic composition which accompanies it in order to enhance the phytoecology data. It was also necessary to understand the dynamics, and the plant taxonomy by analyzing its biological diversity and the pressures which are exerted on this ecosystem. The study of holm oak stands from a phytoecological point of view using a statistical treatment of the floristic data by a hierarchical ascending classification (HAC) allows us to determine the different plant groups existing in the Massif. Given the extent of the degradation in this ecosystem, which is of human and climatic origin, it is necessary to set up a policy for the conservation of this heritage and to draw up suggestions for the safeguarding, improving and conservation of this type of ecosystem.

Materials and methods
We carried out 20 floristic surveys, 10 surveys for each field station, during the spring of both years (2018 and 2019). The floristic inventories were carried out on square plots of 20 x 20 m (400 m²). This size of surface is commonly used in forest ecology, and this measurement resolution aligns well with the perception of ecological phenomena related to the vascular flora in this type of Mediterranean ecosystem (DAGET & GORDON, 1982;LEPART & ESCARRE, 1993;BRAKMAN, 1989;DECONCHAT, 1999;AUSTIN, 1999 in CHEIKH AL BASSATNEH . To compare the floristic diversity of the surveys, we used the Shannon-Weaver H' and Pielou E's equitability indices (LEGENDRE & LEGENDRE, 1979;DAJOZ, 2003;FRONTIER ET AL., 2008;MARCON, 2013).
The Shannon-Weaver diversity index was calculated using the following formula: H' = -∑ pi log2 pi where pi = ni / N Pi: the relative frequency of the category of individuals compared to 1. ni: total number of individuals of species i. N: total number of all individuals.
For the Pielou equitability index E, it was calcualted using the following formula: To compare the degree of similarity between the two field stations studied from a population standpoint, we used the Sorensen index (K), which was calculated according to the following formula (BOULWEYDOU, 2008): K%=2C/(A+B)*100 K = Sorensen's coefficient, A = number of species in list 1, B = number of species in list 2, C = number of common species in both lists.
Statistical analyses: We used the hierarchical ascending classification (HAC) to define the different vegetation groups existing in the Massif.

Floristic diversity
The floristic inventory enabled us to identify 120 species belonging to 106 genera and 34 botanical families, of which 46 species were not included in the flora list of the Belezma National Park (Table 1).

Species distribution by family
The floristic analysis of the surveys showed that the Asteraceae family dominated with 32 species (27%), followed by the Fabaceae with 13 species (11%), the Lamiaceae with 9 species (8%), the Liliaceae with 8 species (7%), and the Brassicaceae with 6 species (5%). These five families are among the richest in terms of genera and species in the taxonomic composition and are well represented in the Mediterranean regions (LE HOUEROU, 1995).
Comparing our results with those of the national flora, the Asteraceae family is the most important botanical family in Algeria, as it contains 408 species distributed across 109 genera (QUEZEL & SANTA, 1963). These results are similar to those reported by HSEINI , who noted that the Asteraceae family still ranks first with 601 species in the spontaneous flora of Morocco (IBN TATTOU, 1987in HSEINI ET AL., 2007 and by DAHMANI-MEGREROUCHE (1996)  The Fabaceae family was recorded in second place, which indicates evidence of anthropogenic activities, especially overgrazing (Fig. 2). The composition of the vegetation spectrum at the Kassrou station shows a predominance of hemicryptophytes over chamaephytes, therophytes, phanerophytes, and geophytes (Table 2).
The stations studied exhibit a predominance of hemicryptophytes (30.33%). According to BARBERO , the abundance of hemicryptophytes in the Maghreb countries is attributed to the presence of organic matter, soil moisture, rainfall, and cold conditions (FLORET ET AL., 1990 in BEGHAMI, 2013) ( Table 2). Our findings are consistent with those of DAHMANI-MEGREROUCHE (1996), who noted that hemicryptophytes dominate in high-altitude forest environments. Hemicriptophytes 33 Therophytes 32 Chamephytes 19 Phanerophytes 9 Geophytes 7 Chamaephytes rank second at the Kassrou station, accounting for 25% of the species, and third at the Om rkhaa station, representing 19% of the species. Chamaephytes play a significant role in the vegetation formations of our study area, particularly in the Matorrals. They are well-adapted to summer drought conditions compared to phanerophytes, as highlighted by DANIN & ORSHAN (1990). Chamaephytes, being photophilic and xerophilic, are generally absent in humid environments (DAHMANI, 1997).
Therophytes rank third at the Kassrou station, comprising 21% of the species with a disturbance index of 45.78%. At the Om rkhaa station, they rank second with 32% of the species and a disturbance index of 50%. FLORET & PONTANIER (1982) point out that the more an ecosystem is influenced by man (overgrazing, cultivation), the more important therophytes become. This preponderance of therophytes is jointly linked to seasonal rainfall and the action of man and the fires that characterise the Mediterranean area. The high abundance of therophytes indicates strong anthropic pressure (BENABDELLAH ET AL., 2010). These species also demonstrate resistance to dry periods and high temperatures. Examples of the therophytes encountered include Pallenis spinosa, Bromus rubens, and Borago officinalis. Additionally, FLORET ET AL.
(1990) highlight that as a system becomes less influenced by human activities such as overgrazing and cultivation, the prominence of therophytes increases. However, there is a relative decrease in the number of therophytes to pre-forest formations despite their overall high presence. In fact, a higher disturbance index signifies a more disturbed environment (BEGHAMI, 2013). The therophytization of forest formations is associated with the widespread invasion by annual species, often subnitrophilous and dispersed primarily by herds of livestock (BARBERO in BEGHAMI, 2013. The value of the disturbance index largely depends on the dominance of therophytes. In the Maghreb region, the expansion of the degree of openness in the vegetation is currently attributed to disturbances of anthropic origin (QUÉZEL & BARBERO, 1990).
In contrast, phanerophytes and geophytes are less represented, accounting for approximately 16% and 8%, respectively, at the Kassrou station. At the Om rkhaa station, the percentages for phanerophytes and geophytes are 9% and 7%, respectively. According to KADI-HANIFI (2003), the number of geophytes decreases with increasing aridity and habitat openness. GILBERT  also note that certain geophytes are highly sensitive to environmental disturbances. DAHMANI-MEGREROUCHE (1996) point out that while geophytes may be less diverse in degraded environments, they can still be represented in some cases in a monospecific manner. In degraded environments, such as those affected by overgrazing, or repeated fires, geophytes can establish themselves and dominate due to their cover abundance (DAHMANI-MEGREROUCHE, 1996). According to KOECHLIN (1961), biological types serve as indicators of a species' life strategy (Table 3).

Distribution by chorological type
The phytogeographical analysis reveals that the studied stations are predominantly influenced by the Mediterranean element (75%). This observation is supported by QUEZEL (2000) for all North African countries. The northern element represents 10% of the flora, followed by endemics (8%) and species with a wide distribution (7%) at the Kassrou station (Table 4). For the Om rkhaa station, the chorological analysis demonstrates the dominance of the Mediterranean element (58%). Species with a wide distribution rank second at 20%, followed by the northern element (13%) and endemic species (9%) ( Table 5).
Our findings are consistent with the results of YAHI ET AL. (2008), who found a similar dominance of the Mediterranean element in the examined cedar forests of the Tellian and Saharan Atlas regions. This pattern is common in most natural ecosystems in Algeria (QUÉZEL, 1964(QUÉZEL, , 2002 and throughout the Mediterranean basin (QUÉZEL & BARBERO, 1990;QUÉZEL & MÉDAIL, 2003).

Diversity indices
The Shannon-Weaver diversity indice (5.99 -5.46), which reveal that the station of Kassrou is richly diverse compared to the station of Om rkhaa, together with Pielou's equitability indice (0.94), is relatively high for both stations, indicating that these ecosystems are very diverse. These two ecosystems are represented by a low value for the similarity index (K = 24.81%), which indicates that the two stations are not similar in terms of floristic composition.

Hierarchical ascending classification (HAC)
The AHC of the species and floristic records for all the ecosystems studied gives a partition into 3 distinct groups for the Kassrou station (Fig. 3). In this group, there are species from arboreal and shrubby formations, such as xerophilous species like Pistacia lentiscus, as well as forest and meadow species that characterize humid climatic environments, such as holm oak, Juniperus phoenicea, Juniperus oxycedrus. The presence of Calycotome spinosa in this floristic group indicates the beginning of degradation of the phytocoenosis (EL HAMROUNI, 2001). This group also exhibits a regressive dynamic, which can be explained by the replacement of forest species by Ampelodesmos mauritanicus and Stipa tenacissima, which are heliophilic species that thrive in degraded formations (DAHMANI, 1997 (DEBAZAC, 1959).
The hierarchical ascending classification (HAC) showed that the floristic records of the Om rkha station are divided into 3 groups (Fig. 4).  The presence of some species shows the degradation of the tree cover such as Ampelodesmos mauritanicus, Astragalus armatus. In this study area, the holm oak is present in the form of scrub, associated with junipers (Juniperus oxycedrus and Juniperus phoenicea). Moreover, the first species, Juniperus oxycedrus, is considered as "the faithful companion of the holm oak" (DAHMANI, 1984).
The degradation of holm oak ecosystems is essentially due to both natural and anthropic pressures (grazing, overexploitation, and fires, etc.) and is explained everywhere by a permanent and continuous regressive evolution. The consequences of this regressive dynamic are a significant change in the floristic composition which varies in the direction of aridity, a modification of the vegetation structure, and a reduction in the plant cover.

Conclusions
This study, carried out on the forest massif of the Belezma National Park, reflects a real image of the very great floristic diversity which should be protected from threats (over-exploitation, over-grazing, fires, etc.). In addition, knowledge of the dynamics of these holm oak groups, which remains complex, has become necessary in order to better conserve and protect these types of massifs.
However, it would be interesting to extend this type of study to other types of forest ecosystems on the one hand, and to certain plant species on the other, with complete and in-depth studies on the phytoecology of these types of massifs. Similarly it is necessary to take all measures to protect this vegetation against fires, which must be reinforced by the construction of lookout posts, to encourage silvicultural work, to clean up and recut burnt holm oaks, to develop water points to prevent water being lost through run-off, to use new reforestation techniques to conserve and enhance the value of holm oak matorrals. It is also necessary to think about a sustainable development programme that will take into account the enhancement and conservation of this heritage and try to maintain the same natural range of flora by setting up defenses, which could ensure the preservation of this biodiversity.