New Contributions to the Ericion umbellatae Alliance in the Central Iberian Peninsula

: The study of heathlands dominated by Erica australis , E. umbellata and Cistus populifolius in the centre and west of the Iberian Peninsula allows us to separate the eight shrubland communities. The taxonomic analysis of E. australis distinguishes two subspecies: E. australis subsp. australis and E. australis subsp. aragonensis . The statistical treatment conﬁrms the differences between the suballiances Ericenion aragonensis and Ericenion umbellatae . This ecological, bioclimatic, biogeographical and ﬂoristic study has allowed us to differentiate three new associations from the remaining ﬁve: TCp = Teucrio oxylepis-Cistetum populifolii nova. HEau = Halimio ocymoidis-Ericetum australis nova. DEu = Drosophyllo lusitanicae-Ericetum umbellatae nova. ECp = Erico australis-Cistetum populifolii Rivas Goday 1964. PCp = Polygalo microphyllae-Cistetum populifolii Rivas Goday 1964. HEa = Halimio ocymoidis-Ericetum aragonensis Rivas-Mart í nez 1979. HEu = Halimio ocymoidis-Ericetum umbellatae Rivas Goday 1964. UEu = Ulici eriocladi-Ericetum umbellatae. TCp Teucrio mariani-Cistetum populifolii is located in more peripheral zones with a greater Atlantic inﬂuence. TCp-Cl Teucrio mariani-Cistetum populifolii is a colder and more continental variant with Cistus laurifolius

Heathlands are one of the most extensive and important habitats on the planet [14,15], and are among the most representative plant communities on the European continent with an Atlantic bioclimate and influence [5,16]. These formations are linked to oceanic environments, with abundant rainfall and short periods of summer drought in the case of the southern Iberian Peninsula [14,[17][18][19][20], and in acidic, oligotrophic soils subject to erosion and fire [21].
Our own samplings were taken following the Braun-Blanquet method, modified by Van der Maarel [24].

Data Analyses
Subsequently, and based on the geographic and topographic information contained in these relevés, each sampling was geo-referenced and implemented in a geographic information system (GIS) using the corresponding maps (Appendix A). They were then matched with the place names and the rest of the data from the samplings in the bibliography in order to obtain the different climatic and bioclimatic variables for each sampling. The figures for altitude, orientation and slope were determined by plotting the previously georeferenced points on a digital terrain map (DTM) with a pixel resolution of 30 × 30 metres for the points in Portugal and Morocco, and on a digital terrain model with a resolution of 10 × 10 metres for the points in Spain. The numerical values for altitude, orientation and slope were obtained from the DTM for each sampling point by means of numerical classification methods. An ascending hierarchical classification was applied for the ordination and comparison of the different samples using Ward's distance. For a better understanding of the results, a multivariate ordination analysis was carried out by means of detrended correspondence analysis.

Discussion
The study of heathlands dominated by Erica australis subsp. australis, subsp. aragonensis, E. umbellata and Cistus populifolius contributes eight different vegetation communities. Until now the heathlands in Luso-Extremaduran territories have been included in the known associations [4,5]. However, our recent studies in the province of Ciudad Real reveal floristic differences to the associations described previously. In the taxonomic study, [22,25] do not recognise E. australis L. subsp. aragonensis (Willk.) Cout., although [5,23] recognise the aragonensis variety.
Species in the genus Erica are always found in sub-humid-humid environments and appear in the dynamics of various types of Quercus from temperate and Mediterranean European areas [27][28][29], but always in acid-neutral pH substrates, never in Quercus forests on basic substrates [30]. In the degradation of these scrubs, either by human action or climate change [31][32][33][34]. They are replaced by species of the genus Cistus [24]; Cistus ladanifer is the species that replaces Erica australis and Erica umbellata in the studied territory.
The association TCp is a shrubland dominated by C. populifolius and is a cold vicariant community of PCp described by [4] for the more oceanic Extremaduran territories. The new association occupies the easternmost areas of the Mariánica mountain range, which receives the influence of the climate of the Manchegan plateau and comprises differential species such as C. laurifolius and the endemism Teucrium oxylepis subsp. marianum. These communities cannot therefore be included in the association PCp. [5] Lecto typifies the association HEu described by Rivas Goday in the province of Cáceres. The floristic and ecological differences make it inadvisable to include the communities dominated by E. umbellata from the eastern Maríanica range in this association, HEu, as they grow on extremely nitrogen-poor distric lithosols that allow the presence of Drosophyllum lusitanicum; the new association is therefore a soil vicariant of HEu. This same author describes the association HEa for the provinces of Segovia and Guadalajara, and gives the typus in the locality of Puerto de San Benito (Guadalajara) at an altitude of 1840 m. The floristic, bioclimatic and biogeographical differences lead us to propose the association HEau for the Luso-Extremaduran territories (Table 5).

Conclusions
This study reveals a set of new associations for scrub dominated by species of the genera Erica and Cistus. All these communities act as dynamic states of cork oak forests Quercus suber, Q. broteroi, Q. pyrenaica, Q. marianica and Q. canariensis, of which the forests of Q. pyrenaica and Q. canariensis are the most fragile, both because they are at the edge of the range and are threatened by climate change. It is therefore essential to protect these forest formations and their dynamic stages, constituted firstly by scrub of Arbutus unedo and secondly by heaths of Erica sp. and C. populifolius. Since all these plant communities are located in sub-humid or humid mountain environments, where a high rate of endemic, rare or threatened species thrive, protection measures must be put in place against fire and excessive livestock pressure. The territory dominated by these shrubs contains a high rate of endemisms, which is why their protection is necessary by subjecting these areas to sustainable development, with control of livestock.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest:
The authors declare no conflict of interest.