'Mediterranean temporary ponds' (habitat 3170*) and 'Alluvial forests with Alnus glutinosa and Fraxinus excelsior' (habitat 91E0*)
a) Expansion of shrubs, mostly Rubus
The uncontrolled expansion of shrubs is a major threat for both 3170* and 91E0*. In 3170* shrubs cover the ponds and depose the less competitive typical temporary pond flora. Additionally, leaf deposition and decomposition cause the built up of a deep layer of soil and litter which becomes an inhospitable substrate. In 91E0* the more aggressive shrubs, such as Amorpha fruticosa, take up space that otherwise would be available for Alnus and other saplings, and also create shade that inhibits growth of Alnus, Salix,Populus, and other saplings and reduces natural regeneration. It is obvious that conservation of biodiversity at species and habitat level requires control of shrub expansion by sbrub removal (Action C2).
b) Illegal logging
Forest management in the Nestos SCI is targeting preservation of the riparian vegetation and there is no commercial logging in habitat 91E0*. However, the forest structure is significantly affected by illegal logging, which has noticeably increased in recent years because of the economic crisis and lack of awareness of local people about its importance. This threat is faced by installation of information boards and awareness raising campaign (Action Ε4). The staff of the National Park have recorded increasing cases of illegal logging but there is no quantification (cut trees, area affected, etc.)
c) Modifications in and/or lack of appropriate water diet
The characteristic flora and fauna of 3170* and 91E0* are very sensitive to modifications of the hydrological cycle since their life cycle depends on regular alternation of wet and dry phases. In the winter of 2016-2017, the ponds held water for only about 2 months, as compared to the average (c.6 months), and their specialised vegetation did not have the opportunity to complete its life cycle. Lack of flooding in 91E0* also means no transport of nutrient-rich sediments which enrich the soils. At the moment it is unclear if this is due to changes in the hydrological functions of the river (channel movement and silting, etc.) or to reduced flow because of retention in the artificial reservoirs upstream (inadequate minimal environmental flow). The project will investigate soil structure and hydrology (Actions Α2, Α3, Α4) and recommend appropriate solutions. The construction of the underground tank (Action C3) will ensure water availability. If an increase in the minimal environmental flow of the upstream dams is deemed necessary, the project team will involve the appropriate water managing authorities which already support the project.
d) Small area of 3170*
The small total area of 3170*, and its fragmented distribution in 2 separate areas, make it vulnerable to natural (reduced precipitation, extreme drought because of climate change, etc.) or anthropogenic (expansion of agriculture, unsustainable water abstraction, etc.) pressures. According to the preparatory actions which will determine the underlying geologic, hydrologic and soil conditions in the area (Actions A2, A3), the project will implement a method of establishing new sites of 3170* (Actions C2) at appropriate localities. This method will be used by the National Park to further increase the surface area of 3170* in future. The establishment of the new temporary pond will be also accompanied by biotic community restoration interventions to facilitate the appearance of the typical flora communities (Action C6).
e) Degradation of 3170* through overgrazing, trampling, etc
As access to the temporary ponds is not restricted, grazing animals degrade their vegetation, especially when grazing takes place during the short flowering period of the characteristic plants. Also, the presence of cattle may affect water quality and damage vegetation by excess trampling and by the possible increase in nitrates which may promote the propagation of competing species. There is frequent evidence of trampling by vehicles (of farmers, hunters, off-road enthusiasts, etc.) at the temporary ponds. Trampling by heavy vehicles causes structural damage to the plants as well as compaction of the soil, making it unsuitable for growth of the characteristic temporary pond species. The project will address this threat by limiting access to the ponds (i.e. fencing, Action C2), and through the installation of information boards and awareness raising campaign (Action Ε4).
f) Alien invasive species
Three alien invasive species (A. fruticosa, P. dioica, A. negundo) are outcompeting indigenous species, mainly in 91E0*, but also encroaching on 3170*. During habitat mapping (Action A6), the location of individuals of the three species will be recorded and, where possible, they will be removed, especially if in shrub form, during shrub clearing (Action C2).
'Mediterranean temporary ponds' (habitat 3170*)
The main threats for 3170* derive from its ephemeral nature and the small size. Limited visibility facilitates its destruction or transformation. Furthermore, increasing climate change impact in the Mediterranean Region is likely to alter the hydrological regimes which determine its functions. The restoration and conservation measures on the habitat will be tailored according to the Technical Report 2008 07/24 MANAGEMENT of Natura 2000 habitats “Mediterranean temporary ponds". In the Palo Laziale SCI, the temporary ponds (total surface 0,40 ha) are spatially and ecologically interconnected with the floodplain oak wood (habitat 91M0). The resulting ecosystem is a common feature along the Tyrrhenian coastline and in the Lazio region (in particular in the Circeo NP and in the Castelporziano Estate). At present, the habitat surface is in regression due to shrub invasion. The spread of shrubs was triggered by a forest decline and is now strongly increasing. Shrubs represent a serious threat for the ponds because their burying effect. The shrub invasion damages the ecological balance established with the tree crown coverage causing various impacts: litter buries the pond and leads to eutrophication; the amount of entering light decreases and thus some typical plants may disappear; water temperature decreases due to the lack of sunlight, affecting normal hatching of invertebrate cysts and amphibian eggs; a rise of evapotranspiration can wither the ponds. To avoid the loss of the interconnected habitat types 3170* and 91M0, it is necessary to act on both of them by: removing the shrubs (Action C2), favoring the recovery and the renewal of the wood (Actions C1, C3), restoring the temporary ponds surface (Action C2). Subsequently, implementing proper wood management (Action C4) and support water dispersion through the hydraulic system (Action C3) to ensure long-term conservation of the ecosystem.
N.B. None of the analyses and studies carried out in SCI of Palo Laziale has shown specific evidence of an excessive abstraction of the water (surface and groundwater) for irrigation. Reduced water availability at the site is strictly related to climatic phenomena that also affect the surrounding agricultural activities.
'Arborescent matorral with Laurus nobilis' (habitat 5230*)
The matorral flap of the Palo wood has been less affected by the forest decline since is adjacent to a superficial flow channel. Given its ecological features, its conservation is linked to the restoration of the wooded area and its proper management will be included in the Forest Management Plan.
'Pannonian-Balkanic turkey oak-sessile oak forests' (habitat 91M0)
At present the forest is mainly occupied by thorny shrubs, with only a small area for new saplings to grow. The tree crown cover has been reduced by up to 80% of its original size, and the trees still alive show senescence and low seed production. There is still forest regeneration (plants at least 3 years old) but growing seedlings are suffocated by the shrubs. This condition strongly inhibits forest recovery, and is a serious regression factor of the temporary ponds. For the past 20 years, a rapid decline of the site has seriously affected tree vitality, causing a grave forest dieback. Death of the trees is caused by fungal attacks (e.g. B. mediterranea). The fungus infection was triggered by the stress imposed on the forest through a number of concurrent causes: (a) increase in aridity following the decrease in rainfall and the rise of temperatures, accompanied by drought events over various years (e.g. 2003, 2007) that have led to a forest dieback in at least 40% of the wood; (b) increasing in salinity and sodicity of the soils; (c) lack of forest management since 1975, when the coppice activities were abandoned.
This forest decline is clearly visible and has led to a gradual disappearance of a large part of the wood. This is seriously threatening the survival of this habitat which extends within the wood for about 40 ha. Fungus, such as B. mediterranea, are still present in the affected area. However, their impact on the trees have reduced due to the gradual dieback of the wood which has entered the pathogens in a quiescence phase. The parasites can normally attack trees under severe stress conditions, while do not affect new seedlings. By breaking the stress factors and restoring resilience and ecological balance of the forest, the fungus will no longer consist a threat for the wood. The monitoring of these parasites and pathogens (Action D2) ensures full assessment of the effects of restoration and conservation measures.