Revista Cubana de Ciencias Forestales. 2019, January-April, 7(1): 125-144
Translated from the original in spanish
Characterization of the pine forest on quartz sands of the Ecological Reserve "Los Pretiles", Pinar del Río, Cuba
Caracterización del bosque de pinos sobre arenas cuarcíticas de la Reserva Ecológica «Los Pretiles», Pinar del Río, Cuba
Alisberkys De la Caridad Gallardo Cruz1
Zenia Acosta Ramos1
1Jardín Botánico de Pinar del Río. Centro de Investigaciones y Servicios Ambientales. Pinar del Río, Cuba. E-mail: zeniaacosta2012@gmail.com
Received: May 4th, 2018.
Approved: January 11th, 2019.
ABSTRACT
In Pinar del Rio, «Los Pretiles» is an area that is included within the ecosystems that demand a rapid conservation action. There is a strong degradation of the pine groves, as well as the disappearance of many typical species of these ecosystems. This fact becomes more important when we consider that this area is considered of great scientific-conservationist interest, given the high endemism of its flora and physiognomic features that characterize the vegetation. This paper shows the floristic characterization of the natural pine groves communities of Pinus tropicalis present in the Ecological Reserve «Los Pretiles», Mantua municipality, Pinar del Río. This area presents a great floristic diversity represented by 274 species, of these 97 are endemic to Cuba. In the same way, threatened species were also listed, with a total of 39 threatened species for 14.2 %, with 27 of these endemic species (84.4 %). The chorological study for Cuba shows that the greatest floristic relationships are manifested significantly in a high number of widely distributed species in the national territory. In the case of corology outside Cuba, the existing relationship with the Neotropics is remarkable, which is explained by the migrations of the ancestors of the flora of the Antilles during the Middle Eocene, through marine promontories of the Caribbean Sea. The analysis of the biological spectrum of the pine forest vegetation showed the existence of species of scarce biomass, accusing the extreme conditions of the substratum of the place, which do not allow the development of species of greater biomass, which explains the scarce representation of phanerophytes. The floristic characterization of this plant formation within the area constitutes a step towards the reworking of the management measures with a view to the reconstruction of the natural landscape.
Keywords: pine groves; physiognomy; floristic and ecology.
RESUMEN
En Pinar del Río, «Los Pretiles» es un área que se incluye dentro de los ecosistemas que demandan una rápida acción de conservación. Existe una fuerte degradación de los pinares, así como la desaparición de muchas especies típicas de estos ecosistemas. Este hecho se hace más importante cuando tenemos en cuenta que esta área es considerada de gran interés científico-conservacionista, dado el alto endemismo de su flora y rasgos fisionómicos que caracteriza la vegetación. En este trabajo, se muestra la caracterización florística de las comunidades de pinares naturales de Pinus tropicalis presentes en la Reserva Ecológica «Los Pretiles», municipio Mantua, Pinar del Río. Esta área presenta una gran diversidad florística representada por 274 especies; de estas 97 son endémicas cubanas. De la misma manera, se listaron las especies amenazadas, con un total de 39 especies amenazadas para un 14,2 %, con 27 de estas endémicas (84,4 %). El estudio corológico para Cuba muestra que las mayores relaciones florísticas se manifiestan significativamente en un elevado número de especies de amplia distribución en el territorio nacional. En el caso de la corología fuera de Cuba, es notable la relación existente con el Neotrópico, lo cual se explica por las migraciones de los ancestros de la flora de Las Antillas durante el Eoceno medio, a través de promontorios marinos del mar Caribe. El análisis del espectro biológico de la vegetación del pinar mostró la existencia de especies de escasa biomasa, acusando a las condiciones extremas del sustrato del lugar, que no permiten el desarrollo de especies de mayor biomasa, lo que explica la escasa representación de fanerófitas. La caracterización florística de esta formación vegetal dentro del área constituye un paso hacia la reelaboración de las medidas de manejo con vista a la reconstrucción del paisaje natural.
Palabras clave: pinares; fisionómica; florística y ecológica.
INTRODUCTION
The situation of the vegetation in the white sands of Pinar del Río, according to Urquiola, (1987) is really critical; he reports that the fundamental cause of the high extinction registered in the typical species of this district is mainly due to its high vulnerability, which is manifested because the narrow ecology of the species does not allow it to react satisfactorily to the ecological impacts, nor to take advantage in the competition with other species of greater adaptive possibilities. This phenomenon is accentuated if we add the impact of anthropogenic origin in a community as fragile as this one, where there is also a high level of endemism.
Within the district of Arenas Blancas, the area of "Los Pretiles" includes ecosystems that demand rapid conservation action. There is a strong degradation of the pine forests, as well as the disappearance of many species typical of these ecosystems.
This fact becomes even more important when we consider that this area is considered of great scientific conservation interest, given the high endemism of its flora and physiognomic features that characterize the vegetation. In this sense, anthropic action has had a negative influence on the degree of deterioration of the natural pine forests of Pinus tropicalis in "Los Pretiles" Urquiola Ecological Reserve and others, (1999a). This study aims to characterize the flora of this plant formation in order to support adequate management of the area.
MATERIALS AND METHODS
Research area
The pine forest of sector 1 "Los Pretiles", whose coordinates are N22°25'47.8", W084°18'32.5", has an extension of 93 ha, it limits to the SW with a swamp area that is part of the mangrove associated with the "Camarones" River, to the SE with a swamp vegetation with mangrove, to the NE with another swamp area associated with the Marín River and to the NW with the sea. The southwestern plain of Pinar del Río, floristically speaking, includes the phytogeographic district known as "Sabana de Arena Blanca" according to Samek (1973) or the "Sabaloense" district according to Borhidi (1991). The study area, Los Pretiles Ecological Reserve, is located in this district.
Study of Flora
It was done based on the data of the species registered for the area and updated by Urquiola and others. (1999b). It was complemented with the species listed in the Ecological Reserve's management plan, in addition to four explorations of the area in the period from 2014-2017. To characterize the species not registered in the management plan or those that are doubtful, the work Spermatophytes of Cuba was used. Greuter and Rankin, (2017).
Chorological spectrum
A chorological study was carried out, using Borhidi's geoelements (1991), both for the distribution inside and outside Cuba, where only one type or geoelement was assigned in each case. In this way, a chorological spectrum was prepared for the analysis of endemism in Cuba and outside of Cuba.
Endemism
This was done by calculating the percentages of endemism, taking into account the following ranges: local or district endemics (X), endemics exclusive to Pinar del Río province (PR), endemics of Western Cuba (OC), endemics of Western and Central Cuba (OC-CC), species split between Western and Eastern Cuba (OC-OC) and Pancuban endemics (P).
Endangered flora
The threatened species were listed; for this purpose, the categories and criteria of threat published in the Red List of Cuban Flora by González-Torres (2016) were considered (See Table 1).
Vegetation study
Physiognomic study
The physiognomic study of the vegetation took into account the criteria of Borhidi and Herrera, (1977) and Capote and Berazaín, (1984). The structure of the vegetation was described by pointing out the representative species for each of the strata: arboreal, shrub and herbaceous, as well as lianas and epiphytes. The terms closed and open applied here refer respectively to whether or not the canopies come into contact in each of the strata.
Morphological characteristics
All the species listed for the pine forest were determined by the biological type of Raunkiaer sensu Ellenberg and Mueller-Dombois, (1967), as well as the size of the leaves according to Raunkiaer, in the year 1934, modified by Borhidi, (1977); the texture of the leaves was made according to Berazaín (1979). All this information is recorded in Table 1.
Wealth and abundance indices
To calculate the biodiversity indices of Shanon Weaver and Simpson, Margalef, R. (1998), five plots were drawn, taking into account the minimum area criterion. This area was adequate to 16 m2 for each plot. In each of the plots, all the species in each stratum were listed and counted. Subsequently the above-mentioned biodiversity indices were calculated with the help of the EcoSim Professional software published by Entsminger in 2014.
RESULTS AND DISCUSSION
Floristic composition
274 species were listed, which are distributed in 68 families, of which 63 spermatophytes, four pteridophyte families and one bryophyte, grouped into 155 genera, of which 149 spermatophytes, five pteridophyte genera and one bryophyte (see Table 1).
The families with the largest number of species in Cuba are the best represented in this area; they are Poaceae with 62 species, Cyperaceae with 29, Fabaceae with 16, Rubiaceae with 12, Asteraceae with 10, Orchidaceae with 9, Xyridacea with 7 and Melastomataceae with 6. They also have two of the three genera of insectivorous plants reported for Cuba: Pinguicula and Utricularia. Other families present all their species reported in this area: Pinaceae and Asclepiadaceae.
One family, represented by only one species in Cuba, is located in the area: Cistaceae with Lechea cubensis, exclusive to this biotope, which grows only in these quartzite sandy soils.
Of the total number of species reported, there are 156 present in the Alturas de Pizarras del Norte, in Mantua Urquiola and others, (1999b), which represents 55.8 % of common species between both districts, evidencing the role played by the Alturas de Pizarras del Norte as a paleo-center; therefore, the origin of more than half of the flora of the white sands of "Los Pretiles" is the neighboring district. Of the 103 endemic to this area, 52 are common with the Alturas de Pizarras del Norte (50.5 %), which reinforces the point of view.
There are a total of 97 endemic species in the area, which represents 35.4 % of endemism. In addition, there are two monotypic genera endemic to Cuba, whose species are Lachnorrhiza piloselloides and Nodocarpea radicans.
Ferns, mosses, lichens and fungi are not well represented in this area, due to the soil conditions and humidity of the area.
Chorological spectrum and floristic relationships
In the analysis of the chorological spectrum in Cuba, it was obtained as a result that from the pineal plant formation, the high number of Pancuban species is significant (125 species, 45 %). This behavior must find its explanation in the existence of similar plant formations in other regions of the country, such as the forests of Pinus sp. div. Following, the relationship with the region of Pinar del Río-Isla de la Juventud with 44 species (16 %) is presented. This affinity is due to the recent separation in the Holocene between both territories.
Following this, the geoelement Occideto Cubanicum, with 35 species (13 %) and Occidento Cubanicum-Centro Cubanicum with 29 species (10,5 %). This trend should be explained by the geographical proximity of both territories, as well as the existence of common soil conditions with certain areas of Central Cuba, where there are sandy deposits, although they are currently highly degraded. In the case of Occidento Cubanicum, the existing relationship is evident, not only because of its proximity, but also because of the union during the last glaciation with the Isle of Youth. Following are very low values given for the Occidento Cubanicum-Oriento Cubanicum, represented by three species, which represents 1 % (See Table 1).
Regarding the district endemics present in the area, a total of 15 are registered, for a 14.6%; these three species are considered local endemics, representing 3% of the total endemics in the pine forest. This figure is explained by the edaphic characteristics, given by the sandy condition, seasonality, acidity, deficit of nutrients and organic matter, as well as the low capacity of cationic exchange; all this determines the existence of a highly specialized flora to the very unfavorable physical and chemical conditions in the substrate. On the other hand, it must be taken into account what Samek (1973) and Borhidi (1991) have proposed, regarding the possible conservative character of the endemism of the white sands. That is, the possible development of numerous endemics in the Alturas de Pizarras del Norte, because these species took refuge in white sand biotopes where they were able to adapt and evolve practically without competition. Despite this, many species, especially those adapted to humid places, must have originated in the white sands themselves.
In terms of the distribution outside Cuba (see table 1), the greatest floristic relationships are established with the Neotropics, with 42 species, for 15.3 %. Next, there are the Macroantillana with 24 species, for 9 %; the Antillana, with 23 species that represent 8.3 %; the United States with 17 species (6 %); Norcaribe with 18 (6.5 %); the Pantropical are 13 species (4.7 %) and the Florida-Antilles-Bahamas with 11 species for 4 % respectively; finally, there are other geographical zones whose values are below those mentioned above.
Endemism
From the 274 species reported for the area, 97 are endemic (see Table 1), which represents 35.4% of the total flora reported for the pine forest. These are distributed as follows: local endemics 3 (3 %), district 12 (12 %), Pinar del Río 12 (12 %), Pinar del Río-Isla de la Juventud 35 (34 %), Occidento-Cubanicum 13 (12 %), Occidento-Cubanicum-Centro-Cubanicum 11 (11 %), Oriento-Cubanicum-Occidento-Cubanicum with 1 (1 %) and Pancubanas 16 (15,0 %). The representative families of the Cuban endemics present in the area are Poaceae, Asteraceae, Euphorbiaceae, Rubiaceae and Eriocaulaceae.
From the 97 endemic species reported for the area, 33 are present in the locality, Pinar del Río and Pinar del Río-Isla de la Juventud, according to Borhidi's categories, in research carried out in 1996, which represents 34%. As explained before, there is a common geological past between the white sand territories of Pinar del Río and Isla de la Juventud, as well as very similar soil conditions regarding sandy condition, seasonality, acidity, poor nutrients and organic matter and cation exchange capacity, among other characteristics, which determines the strong affinity from the floristic and phytogenic point of view. On the other hand, the endemism of the pine forest is significant, with three local endemic species, which can be explained by the extreme characteristics of the substrate mentioned above, as well as the endemics that emerged in the Northern Shale Heights and took refuge in the young biotope of the white sands, as explained by Samek, (1973) and Urquiola, (1999b).
Endangered flora
From the species referred to for the pine forest, 39 are in different categories of threat, which represents 14 %. It should be noted that 29 of these species (74 %) are endemic (See Table 1).
Regarding the spectrum of the species of the vegetation of the pine forest according to the habit, this formation is currently formed by a forest with widely separated canopy trees (open), of 6-10 m, although there are some specimens that reach 15 m in height. The arboreal stratum is represented by the families Anacardiaceae, Annonaceae, Calophylla, Cyrillaceae,Fabaceae, Myrtaceae, Pinaceae and Arecaceae, being its species: Anacardium occidentale, Xylopia aromatica, Calophyllum pinetorum, Cyrilla microareolata, Brya ebenus, Eugenia maleolens, Pinus caribaea, Pinus tropicalis and Coccothrinax miraguama.
The bush stratum is composed of a greater number of species (31), the most represented genera are Byrsonima (three species), Ouratea (two species), Hipericum (two species), Crossopetalum (two species) and Lyonia (two species). The species corresponding to these genera are: Byrsonima crassifolia, Byrsonima pinetorum, Byrsonima wrightiana, Ouratea elliptica and Ouratea ilicifolia, Hypericum styphelioide, Hypericum nitidum, Crossopetalum aquifolium, Crossopetalum rhacoma, Lyonia ekmanii and Lyonia lucida. Other genera in this stratum have only one representative species: Acoelorraphe wrightii, Baccharis halimifolia, Tabebuia lepidophylla, Kalmia ericoides, Jatropha angustifolia, Malpighia horrida, Chaetolepis cubensis, Henriettea patrisiana, Pachyanthus wrightii, Tetrazygia impressa, Morella cerifera, Eugenia punicifolia, Psidium salutare, Chrysobalanus icaco, Callicarpa americana, Pavonia intermixta, Peltaea speciosa and Stachytarpheta angustifolia.
The herbaceous stratum presents the greatest floristic richness (216 species), with the presence of species typical of pine forests on white sands; in this case we can mention the following species: Eleocharis knutei, Schizachyriumn parvifolium, Xyris mantuesis and Waltheria arenicola.
Biological types
Referring to the biological type and the morphological characteristics of size and texture of the leaves of each one of the species present in the pine forest, the biological spectrum of the vegetation of the pine forest (See table 1) shows that, out of 274 species present in the place, 93 species are hemicryptophytes (34 %), 67 are camephites (24 %), 30 are therophytes (11 %) and the nanophanerophytes are 27 (9.8 %). The remaining biological types are represented below 10 %. The predominance of species with low biomass is remarkable, showing the extreme conditions of the substrate referred to above. As is known, the climate is suitable for the development of forest formations; however, it is the substrate that does not allow the development of species with higher biomass, which explains the low representation of phanerophytes, which is the biological type ecologically adapted to the most appropriate living conditions for plant life.
Size and textures of leaves
Regarding the leaf size spectrum for the pine tree species, there is an evident predominance of microphilic leaves, present in 100 species, for 36.4 %. Following this, nanophiles appear in 69 species, for 25 %; then leptophiles in 57 species, for 20.8 % and notophiles in 31 species, for 11 %. As can be seen, there is a predominance of leaves with a tendency to reduce, i.e. from notophiles to leptophytes, over mesophiles, macrophiles and megaphiles. This is an indicator of the evident adaptation of these plants to the xerophitism imposed by the substrate, as well as to the action of the south wind, the proximity to the sea and the high temperatures existing in these formations that are mostly open.
The result obtained for the texture of the leaves shows that, out of a total of 274 species, there is a predominance of carthaceous leaves (184 species for 67 %), membranoids (53 species for 19 %), sclerophytes (17 species), for 6 %) and coriaceae (15 species, for 5 %) The behaviour of this indicator shows synergy with those analysed above, highlighting the xerophytic character of the vegetation due to the scarcity of leaves with membranoid texture (Table 1).
Table 1. - General characteristics of the natural pine forest "Los Pretiles"
Legend:
Cor. Cuba (chorology in Cuba), where PR (Endemic exclusively to Pinar del Río province), PR-IJ (Disjunctive species between Pinar Río and Isle of Youth), OC (Occidento-Cubanicum, western Cuba), OC-CC (Occidento-Cubanicum-Centro-Cubanicum), OC-OR (Occidento-Cubanicum-Orientocum), P (Pancubanas), NoCono (Not known).
Cor. Ext (Chorology outside Cuba), where PT(Pantropical), A-B (Antilles-Bahamas), MA (Macroantillas), NC (Norcaribe), SA-C (South America-Cuba), EU (Florida-south-eastern United States), FAB (Florida-Antilles-Bahamas), NT (Neotropical), SC (North of South America), A (Antilles), Amer (Americans), C (Cosmopolitans), PC (Pan Caribbean), SA-A (South America-Antilles), NoTien (No chorology outside Cuba, they are Cuban endemics), NoCono (Not known).
Ca. Ame (Category of threat), where: A (Threatened), CR (Critically Endangered), EN (Endangered), VU (Vulnerable).
Tip. Bio (Biological Type), where: H (Hememicryptophytes), Ch (Camephites), G (Geophytes), Mc-McP (Micro-Mesophanerophytes), LH (Micro-Mesophanerophytes), LP (Woody Lianas), McP (Micro-Phanerophytes), MsP (Mesophanerophytes), Th-H (Hemiterophytes), Th (Therophytes), MgP (Mega-Phanerophytes), NP (Nano-Phanerophytes).
Ta. Leaf (Size of the leaf), where: Mic (Microphilic), Nan (Nanophilic), Mes (Mesophilic), Not (Notophilic), Lep (Leptophilic), Mac (Macrophilic), Meg (Megaphilic).
Tea. Leaf (Texture of the leaves), where: Car (Carthaceae), Cor (Coriaceae), Men (Membranoceae), Esc (Sclerophylls).
Biodiversity indices
The calculated average Shannon-Weaver index was 1.7912, while the average Simpson index was 0.5210. These values take on absolute meaning when we refer to their extreme values; otherwise, their interpretation is relative to the comparison with indices calculated elsewhere. For example, table 2 shows the indices for the natural pine forest of "Los Pretiles".
Table 2. - Shannon-Weaver and Simpson biodiversity indices for the "Los Petriles" pine forest
As it can be seen, both the Shannon-Weaver and Simpson indexes are high in the natural pine forest "Los Pretiles", evidencing that there is a high species richness and abundance in this plant formation. The high biodiversity is due precisely to the conservation character of the endemism in the white sands. That is to say, many endemic species of Alturas de Pizarras del Norte took refuge in white sand biotopes, where they were able to adapt and evolve practically without competitors. In addition to this fact, speciation developed in the area, manifested in the origin of new species for this area, especially those adapted to humid places. The greater abundance is explained by the extreme soil conditions of the area. The plants adapted to these conditions of the substrate present scarce biomass, which makes them small and can manifest themselves with a greater number of individuals. This fact should result in "Los Pretiles" having more abundance than biodiversity in its flora.
There is a great floristic diversity of 274 species and a high endemism in the flora that characterizes the area, where the predominance of species of scarce biomass is notable, accentuating the extreme conditions of the substrate.
The analysis of the chorology in Cuba shows that the greatest floristic relationships are significantly manifested in the high number of species with a wide distribution in the national territory.
Regarding the size of the leaves, there is a predominance of leaves with a tendency to reduce; that is, from notophiles to leptophytes, over mesophiles, macrophiles and megaphiles, while carthaceous and coriaceous leaves predominate.
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Copyright (c) 2019 Alisberkys De la Caridad Gallardo
Cruz, Zenia Acosta Ramos