Name of the site: Arxuri
Protection categories: Listed as Protected Non-developable Land due to its Environmental Value, Wetlands, in Navarre’s Land Planning Programme 2 “Atlantic Navarre”.
Coordinate reference: 30TXN1689, 30TXN1689, 30TXN1789, 30TXN1790.
Surface area of the wetland: 18.31 hectares.
Altitude: 475- 540 m.
This site is located in a basin or enclosed valley in which water drainage is hindered. The basin is semi-enclosed, being more open to the East, and is bordered by a stream to the South, towards which it slopes down. There are colluvial areas both to the West, the largest and most active areas descending from the peak of Peña Plata, and to the Northeast, both areas having several points of running spring water.
At its highest points, the site area has a number of points of running spring water, both diffuse and active to varying degrees, from which flowing channels of different lengths emerge, some of which form significant streams lower down. Others, meanwhile, fade out and disappear in the colluvium.
There are two peat deposits in the central area and on the eastern-most bend, the one in the middle being the largest and deepest, and the only one to have been subjected to palynological study (Peñalba 1989).
The water in the channels from springs, runoff water and water flowing under the surface from the peat deposits drains through stream beds to the brook, which flows from West to East. The brook seems to disappear at the western-most edge of the basin, where it suddenly delves down about 1 metre in between blocks of rock and their loamy matrix. It communicates with the brook that flows towards the East of the basin in the gully.
There are no free layers of water except a small pool which collects the water draining from Peña Plata and a few small sections of brook.
- MOST IMPORTANT VALUES
Arxuri is one of the sites with the largest peat deposits in Navarre.
Biological and ecological values
Of the vascular plants, the following three species should be highlighted: Rhynchospora fusca, Drosera intermedia, Pinguicula lusitanica. HCI 7150 is the most noteworthy habitat.
Historical and paleoecological values
There exists a palynological study (Peñalba 1989), which is one of the few historical studies to be found on the north of Spain. It describes a deposit with a maximum depth of 111 cm at the foot of Peña Plata. This deposit, located between two levels of colluvium in the Centre-North of the basin, covers an area of 0.8 ha and has a perimeter measuring 370 m. The area is slightly, but noticeably convex, covered with herbage with a few Ericaceae shrubs and small populations of Sphagnum spp. and Leucobryum glaucum. The low level of waterlogging observed and the presence of these small areas of Sphagnum would seem to indicate the possibility that this part of the peatland is still, to an extent, active. There is another, far smaller deposit at the easternmost point, covering 0.19 ha and with a perimeter of 162 m. This area is much less waterlogged and inactive.
Habitats of Community Interest
Hábitat Nombre 4020* Brezales húmedos atlánticos de zonas templadas de Erica cillaris y Erica tetralix 4030 Brezales secos europeos 6230* Formaciones herbosas con Nardus, con numerosas especies, sobre sustratos silíceos de zonas montañosas (y de zonas submontañosas de la Europa continental) 6410 Prados con molinias sobre sustratos calcáreos, turbosos o arcillo- limónicos (Molinion caerulae) 7140 «Mires» de transición 7150 Depresiones sobre sustratos turbosos del Rhynchosporion
The most striking feature of Arxuri is the abundance of Rhynchospora alba and Drosera intermedia, although the presence of Eriophorum angustifolium, Menyanthes trifoliata, Genista anglica and Dryopteris carthusiana in the basin is also worthy of note, as is the presence of Rhynchospora fusca, Pinguicula lusitanica and Sanguisorba officinalis on the outflows on the slope. Both Pinguicula lusitanica and Drosera intermedia are listed as “sensitive to changes in their habitats” in the Catalogue of Endangered Flora in Navarre.
The wealth of flora is great, 72 species of vascular plant and 20 species of bryophyte, including 6 species of sphagnum, having been recorded.
The threat factors are the destruction or alteration of its larval habitats and, particularly, water channels. The natural structure of the channels should be maintained or restored, with marginal areas waterlogged to varying degrees and small, shallow branches on the sides, where the species can reproduce. Onychogomphus uncatus (Charpentier, 1840). We found the species out of the transect, near the peatland of Arxuri, in an area with very small brooks, on the 12th and the 25th of July 2009. Onychogomphus uncatus ♂ Senorio de Bertiz 19-July-2009. Conservation status: Included in the “Red Book of Invertebrates of Spain” in the IUCN Category “Vulnerable”, criterion B2ab(iii).