Lichens in the agricultural land of Poland – diversity , threats , and protection : a literature review

Agricultural landscapes provide interesting habitats and substrates occupied by lichens. Nevertheless, there are still gaps in knowledge about diversity of lichenized fungi in rural areas and factors that determine their occurrence, including anthropogenic impact. The review includes recognition of this topic in the regional context in Poland and presents literature data about species diversity and habitat groups. Human influences in terms of their significance for lichens disappearance as well as preservation of the lichen biota are analyzed. A list of threatened lichens found in rural areas as well as a proposal for protection of the lichen biota are given.

In this paper, the current knowledge about the lichenized fungi in the agricultural land and its importance for lichen diversity conservation in Poland is presented based on the literature survey.The article also revises threats to lichens and their protection in a man-transformed rural landscape.

Species diversity
Available data suggest a moderate level of species diversity of lichenized fungi in the agricultural land.In almost completely deforested areas in rural landscape of the Choszczno Lake District, 184 taxa were found [1,2], while 154 taxa were recorded in the agricultural landscape of the Sandr Nowotomyski [3].In the Polanowska Upland 146 species were collected in open areas covered by meadows, pastures, bounds, fallow lands, and psamophilous grasslands, while in villages, settlements and gravel pits 116 species were observed [5].The biota of particular villages and their surroundings is mainly represented by several dozen lichen species [23,24,26,[29][30][31][32][33][34]44], rarely exceeding 100 taxa [27].Species diversity is related to, among others, ecological factors of the sampling localities, including their climatic conditions, the availability of suitable habitats and substrates, but also to the land use.Adopted sampling strategies depending on research objectives also affect lichen diversity assessment.
Terricolous lichens seem to play only a minor role among lichenized fungi growing in rural areas.There is a limited amount of information about their diversity or their occurrence in these places, and therefore it is difficult to find out species associated with the agricultural landscape.Available data suggest that the lichen biota occurring on soil is less diverse and interesting species are rarely found.It can be partially explained by the fact that a large part of rural areas is covered by fields and other agroecosystems which do not allow many species to survive.For example, land use activities can prevent terricolous lichens from a successful establishment due to ploughing, fertilization, etc.In the agricultural landscape more terricolous lichens grow in psamophilous grasslands, developed on the slopes of deforested dunes and fallow lands.Surveys in rural areas confirmed the presence of species mainly from the genera Cetraria, Cladonia, Peltigera, and Trapeliopsis; they were observed near roadsides, balks and fallow lands [3,11,14,19,27,70,78,81,85,93,94].Some records of lichens are known from pastures [3,65,73,95] and mid-field peat bogs commonly referred as agricultural wasteland [67].However, both trampling, grazing, as well as fertilization induce negative influence on habitat conditions and growth of terricolous lichens, especially on pastures [3].Species from genus Peltigera were sampled in meadows [95], nevertheless high humidity of soil here is indicated as the factor that limits the abundance of terricolous lichens [85].

Threats and protection
The intensive agricultural activity is indicated as one of the major threats to lichens in Poland [96].Farmlands are sometimes described as "lichen desert", where lichenized fungi disappear due to application of mineral fertilizers and agrochemicals [2,6,84].Destruction of habitats and substrates through, e.g., removal of old trees growing in orchards, roadsides or mid-field afforestations, timber constructions, isolated blocks, and smaller stones can also have negative effect on lichens and eliminate sensitive species [2,3,18,24,41,88,97]. Special attention should be paid to lichens that colonize bark of free-standing and old phorophytes.Nowadays, their well-preserved lichen biota with rare taxa persists in northern and northeastern part of Poland [4,7,20,97].
In the other part of the country epiphytes of free-standing trees are declining due to gradual removal of phorophytes [97].Lichen diversity in orchards is related, among others, to type and intensity of human activities [41,42].At present there is a trend toward denser and more intensive orchards and it poses growing threats for survival of the lichen biota in farmlands.Bleaching trunks of fruit trees and rubbing of tree bark by farm animals can result in a significant loss of epiphytes in the affected agroecosystem [41].Studies conducted in the Bieszczady Mts revealed that localization of investigated orchards at less frequently visited areas and far away from main routes positively influences lichen diversity [39].Similar observations in the same mountain range have been made in vanished villages; investigated anthropogenic habitats were indicated as important refuges of rare lichen species [44].According to Zielińska [87], agricultural activities impoverish epilithic lichens communities on isolated blocks.Disappearance of some species that inhabit boulders in open areas is associated with, e.g., their dust impregnation, which enables for colonization by nitrophilous and coniophilous species such as Acarospora fuscata (Nyl.)Th.Fr., Candelariella vitellina (Hoffm.)Müll.Arg., Lecanora alpigena (Ach.)Cl.Roux., Physcia adscendens (Fr.) H. Olivier, and P. dubia (Hoffm.)Lettau [6,7].Epilythes are negatively affected by cleaning and renovation of gravestones as well as other cemetery elements [35].Air pollution, also generated by household fuel combustion is other important threat for the lichen biota [3,17,41,43].
The presence of many valuable and interesting taxa in the Polish countryside increases the conservation value of many areas.Studies devoted to protected and threatened lichens in the agricultural land of Podlasie were conducted by Matwiejuk [35], and among them epiphytes and terricolous species were more frequent.Their diversity was similar in forest and mid-field afforestations and near rivers.Also Kapek [44] paid special attention to threatened lichens during lichenological surveys in vanished villages in the Bieszczady Mts.Among 97 recognized taxa of epiphytes, 37% represented species that had been included into the red-listed categories in Poland [96].Information about threatened lichens in rural areas can be also found in papers by, e.g., Lipnicki and Tobolewski [2], Zarabska [3], Kolanko and Matwiejuk [23], Szymczyk and Zalewska [24], Matwiejuk [26][27][28], Matwiejuk and Korobkiewicz [29], Kiercul [30,33], Łubek and Biskup [43], Kowalewska et al. [51], Kukwa [53][54][55], Kubiak et al. [68], and Popiel and Szczepańska [92].Their records after publication of the current red list of lichens in Poland in 2006 are presented in Tab. 1.Most of them have been put on the red list of extinct and vulnerable lichens of Poland [96] in the endangered categories EN, NT, and VU.
Numerous studies conducted in the agricultural land revealed also protected species (e.g., [3,24,[26][27][28][29][30][31]35,41,43,44,49,80]).Lichen conservation extends beyond species protection and it includes efforts to preserve ecosystems and landscapes at least in unimpaired conditions.Considering the presence of some rare species that required better protection in Jabłonka Stara, lichenologist postulated to include the village into the Pszczewski Landscape Park (W Poland) [48].Records of interesting lichen species in the agricultural land in the central part of the Sandr Nowotomyski, especially in psamophilous grasslands in Nowy Tomyśl surroundings and the rich lichen biota on alders (Alnus sp.) and willows (Salix sp.), i.e., phorophytes that grow frequently in mid-field afforestations characteristic for the region, should support the establishment of the Sandr Nowotomyski Landscape Park [3].
Tab. 1 Bibliography of threatened lichens in Poland noted in the agricultural landscape after 2006 r.
In the rural landscape old orchards must be conserved because they provide unique habitats for survival of many rare, protected, and threatened species [3,[39][40][41]44].Their role as local regulators of microclimatic conditions in deforested rural areas is also known [41].Establishment of young plantations in environs of old ones could allow for expansions of epiphytic lichens growing on old fruit trees [3].The lichen biota of old orchards could be a source of vegetative, symbiotic diaspores, or sexual ascospores that could develop into adults on bark of younger phorophytes; ■ preservation of the cultural heritage which can be related, among others, with promotion of regional architecture.The significant use of wood for several purposes in the countryside could also provide potential habitats occupied by lichens.Every effort or task undertaken to maintaining timber constructions in the rural vicinity will allow for establishment and conservation of numerous epixylous lichens; ■ the legal protection in the form of recognizing isolated blocks and old trees, also alleys of trees that host the rich lichen biota as natural monuments; ■ education of local communities by, e.g., popular science articles, brochures, and easily accessible educational boards that promote the current state of knowledge about the lichen biota, its occurrence in the agricultural landscape and proposals of its protection; ■ country parks and mid-field afforestations in nearly deforested rural areas enable for the presence of lichen associated with forest communities.Kubiak et al. [68] indicated the importance of older trees, the limited occurrence of acclimated tree species, diversification of habitat conditions and lack of larger industrial plants in the vicinity of study area for preservation of the lichen biota in the investigated manor park in Opiniogóra Górna (N Mazovia).They also suggested that introduction of new plantings into park tree stand should include phorophytes, e.g,.maple and ash that create favorable substrate conditions for lichens.
It should be underlined that strategies of protection in order to prevent biodiversity loss in rural areas are mainly adjusted to needs of particular groups of organisms, e.g., birds.In fact, these recommendations should be confronted with proposals of activities undertaken to preserve other groups of organisms, e.g., lichens.It will enable to develop a consistent and effective approach to solve the problems of protection, conservation, and restoration of the natural heritage.Regional differences in Poland are related, among others, to land history and use, as well as the intensity of Xanthoria ulophyllodes Räsänen VU [44,49,55] Category of threatens according to Cieśliński et al. [96]: CR -critically endangered; EN -endangered; VUvulnerable; NT -near threatened; LC -least concern; DD -data deficient.Nomenclature was checked according to Index Fungorum [99].
agricultural practices.The role of these factors on the lichen biota could be recognized through gathering data from different parts of the country.Improving the knowledge on lichens growing in agricultural landscapes should be pivotal for the establishment of conservation strategies.