A Contribution to the Knowledge of Polypores Occurring in City Parks: A Case Study of Five Parks in Wrocław (Lower Silesia, Poland)

Abstract

We surveyed five urban parks in Wrocław, Lower Silesia (Poland) to document the diversity of wood-inhabiting fungi and assess their potential impact on trees and public safety. Field observations were conducted in 2021, yielding 53 fungal occurrences representing nine species of eight genera. The most frequently recorded taxa were Fomes fomentarius (accounting for 43.4% of all fungal observations), Fomitiporia robusta (15.0%), and Laetiporus sulphureus (13.2%). The highest number of fungal findings (35.8%) occurred in Zachodni Park, which is also the largest of the surveyed parks, while Grabiszyński Park—the second largest—had the lowest share (9.4%). Fungi were found on trees of six genera and eight species, most commonly on Quercus robur (35.5% of colonized trees) and Betula pendula (26.7%). In eight cases, host trees could not be identified due to severe damage or removal. Most fungal fruiting bodies appeared on upper trunks or branches of aging, weakened, or decaying trees. As the surveyed parks are highly frequented recreational areas, regular monitoring of wood-inhabiting fungi is recommended to manage tree health and minimize safety risks for park visitors.

1. Introduction

Wood-inhabiting fungi are an important element of forest ecosystems due to their role in decomposing coarse woody debris, such as fallen trunks, branches, and stumps [1]. Polypores (bracket/shelf fungi; Polyporaceae s.l., Agaricomycetes) are a common name for the major group of wood-rotting Basidiomycota [2]. They can be commonly seen growing on trees in city parks or forests due to their noticeable large basidiomes, poroid configuration of the hymenophore, and diverse morphology [3,4]. Polypores are able to inhabit either living trees (often weakened individuals) or damaged ones and wood. On the one hand, polypores and other wood-inhabiting fungi might pose a threat to certain tree collections. On the other hand, they play a key role in the dynamics and health of any type of forest worldwide [5]. Thus, the dual role of wood-inhabiting fungi underscores the need for a comprehensive understanding of these organisms within urban settings.

Trees in city areas are prone to weakening due to pollution, smog, and poor ventilation resulting from dense buildings. The aforementioned damage is influenced, i.e., by diseases caused by polypores, which affect the durability, stability, and health of the stands. Consequently, it might lead to tree dieback. Additionally, diseases caused by tree-dwelling and woody fungi limit the production of planting material [6]. Thus, wood-inhabiting fungi are discussed in terms of economic losses in the industry such as horticulture, forestry, park management, wood processing, transportation, construction, and telecommunications [7].

Historically, Wrocław stands as one of Poland’s most extensively studied cities mycologically as reported by Adamczyk and Ławrynowicz [8], who summarized investigations in Poland between 1860 and 1990. Interestingly, the most prominent works are dating back as far as the 19th and 20th century [9,10,11,12,13,14]. Despite this, the fungal diversity in Wrocław urban green spaces might have changed drastically since the last comprehensive surveys. More recent studies by Halama [15,16] have laid the groundwork for understanding the fungal biodiversity within the present state of the city. Halama [16] also reported that over the past 150 years, nearly 950 species of macroscopic fungi have been recorded; among them, approximately 15% are endangered species in Poland. Yet, despite this rich body of research, certain urban green spaces in Wrocław remain underrepresented in the literature, notably excluding locations outside of the previously well-studied Południowy Park.

Therefore, our research was undertaken to enlist species of macroscopic basidiomycetes by identifying observable basidiocarps in five selected city parks in Wrocław (namely, Wschodni, Zachodni, Grabiszyński, Południowy, and Brochowski), and to discuss the distribution of the reported wood-inhabiting fungi.

2. Materials and Methods

2.1. Study Sites

In the present study, wood-inhabiting fungi were recorded in five parks located in the city of Wrocław, Lower Silesia, Poland. The city has a total of 44 parks covering approximately 781 ha [17]. To narrow down the study area, the following selection criteria were applied: (I) convenient access to the park area; (II) estimated age and condition of the park and its tree stands; (III) a low proportion of visibly dead or dying trees—defined as less than 10% of the total tree population. This threshold was adopted based on visual assessments and aligned with the damage classification proposed by Bujoczek [18], where >20% dead trees indicates stand damage. The intention was to include sites where fungal presence could be associated with natural ecological processes rather than advanced decay or anthropogenic disturbance. Based on these criteria, five parks were selected: Wschodni, Zachodni, Grabiszyński, Południowy, and Brochowski. Importantly, the selected parks are spatially distributed across the entire city area, ensuring broad geographic coverage. The exact locations of the studied areas are included in Figure 1, whereas detailed descriptions are provided in the next paragraphs.

2.1.1. Site Characteristics–Wschodni Park

Wschodni Park (prev. Ostpark) is classified as a landscape park with an area of 32.5 ha (including 0.15 ha of water areas) established in the 1920s. During the events of World War II and the flood of 1997, Wschodni Park was heavily damaged. As a result of the flood event, many trees suffered mechanical damage, including crown loss, root stress, and increased susceptibility to decay [20]. The current presence of deadwood and weakened trees in this park may contribute to increased fungal colonization opportunities and the later development of fruiting bodies. The park had been constantly renovated up until 2002 [20].

The park complex has the characteristics of an alluvial and oak-hornbeam forest. Two rivers (Oława Dolna and Oława Górna) mark the boundaries of the park. Additionally, the canal connecting both rivers marks the northwestern areas of the park. Due to the presence of wetlands, predominant tree species are distinguishable for such a habitat. According to the 2002 census, there are 68 different tree species, 89% of which are native to this area [20]. The predominant tree species include Alnus glutinosa (L.) Gaertn., Quercus robur L., Tilia cordata Mill., and Betula pendula Roth. Additionally, the following can be found: Acer campestre L., Carpinus betulus L., Fraxinus excelsior L., Prunus padus L., Salix alba L., Betula papyrifera Marsh., Pterocarya fraxinifolia (Lamb.) Spach, Quercus palustris Münchh., and Phellodendron amurense Rupr. The population of bushes is less diverse and comprises Corylus avellana L., Cornus mas L., Crataegus monogyna Jacq., Frangula alnus Mill., and Rhamnus catharticus L. [20].

2.1.2. Site Characteristics–Zachodni Park

Zachodni Park (prev. Bebelpark or Westpark) was established either in the 1890s or between 1905 and 1910 (according to various sources) and covers an area of 75 ha. The park holds a recreational and sports function due to the facilities located in this area. Historically, the area consisted of cemeteries, the last of which was removed in 1967. In the western part, there is a loose tree stand aged from 100 to 120 years. The predominant tree species include Betula pendula, Picea abies (L.) H. Karst, Robinia pseudoacacja L., Aesculus hippocastanum L., and Tilia cordata. Additionally, the mature species Acer platanoides L., Quercus rubra L., Q. robur, and Carpinus betulus can be found. However, these species have mostly been damaged by the flood of 1997 or other natural disasters. In the northern part, the following bushes are present: Viburnum opulus L., Rosa canina L., and Sambucus nigra L. [21].

2.1.3. Site Characteristics–Grabiszyński Park

Grabiszyński Park covers an area of 48 ha with the Ślęża River marking its southern boundary. The park was established in the area of former cemeteries (ca. 1867-81), one of which still forms the main part of the park. Most of the plant species were destroyed due to the 2005 severe storm. Currently, the following plant species can be found: Crataegus spp., Symphoricarpos albus Duhamel, Prunus spinose L., Acer spp., Quercus spp., Rosa spp., Sambucus nigra, Carpinus betulus, Tilia spp., Betula verrucosa (Rothm.), as well as Thuja spp. [22].

2.1.4. Site Characteristics–Południowy Park

Południowy Park was established from scratch between 1892 and 1897 on the land of agricultural fields near the Borek colony and originally covered approximately 30 ha [23]. Nowadays, the park is classified as a landscape park with an area of 25 ha. Since 1995, the park has been listed in the national register of monuments. In contrast to other parks in Wrocław created by adapting forest areas, Południowy Park was created artificially between 1877 and 1892. In general, the park contains 109 plant species dominated by Tilia and Quercus spp. Additionally, representatives of Acer, Aesculus, Thuja, Fagus, Carpinus, and Taxus spp. can be found [23,24]. The unique dendrological specimens are Platanus hispanica Münchh., Carya ovata (Mill.) K. Koch, Taxodium distichum, Liriodendron tulipifera L., Ginkgo biloba L., and Aesculus hippocastanum Digitata [23,24].

2.1.5. Site Characteristics–Brochowski Park

Brochowski Park is the oldest park in the city of Wrocław (established between 1727 and 33) with an area of 8 ha. Since 1951, the park has been listed in the national register of monuments [25]. However, most of the angiosperm trees were heavily damaged due to the severe storm in 2005, whereas conifers were damaged during the severe storm in 2007. Currently, there are 200 plant species, including 18 individual trees classified as natural monuments (i.e., Tilia maximowiczaiana Shiras, Ulmus leavis L., and Tilia platyphyllos L.). Additionally, the following species can be found: Aesculus hippocastanum, Fraxinus excelsior, Carpinus betulus, Acer platanoides, A. pseudoplatanus L., Fagus sylvatica L., Quercus robur, Tilia cordata, and Taxus baccata L. [25].

2.2. Study Design and Sampling

The field research was conducted between 10 January and 8 July 2021—this study period was selected to document early-stage and overwintered fruiting bodies, and due to logistical constraints related to park maintenance cycles. We used an exploratory walk-through method, aiming to visually scan the entire accessible area of each park and capture the greatest possible habitat and host diversity. The essential characteristics of the occurring wood-inhabiting fungi, including the host tree species and habitats in which they occurred, were recorded. The study was limited to macroscopic basidiomycetes; hence, only easily observable basidiocarps were recorded. The exact patterns in the documentation were as follows: the successive sample site number and collection date; the species of the fungus (visible basidiocarps); the estimated age, condition and additional characteristics (e.g., discoloration due to algae growth) of the basidiocarps; the species and estimated age of the host tree; the condition of the host tree (trunk, tree cut from above, intact tree); additional characteristics of the host tree (presence of cavities, rots, crown-dying and other visible damage); the number and place (base of the trunk/medium height/high; in the case of higher parts of trees, a folding field ladder and binoculars were used) of the basidiocarps on the host tree; and the GPS coordinates of the finding, measured using Trimble JUNO 5D (Trimble Navigation, Westminster, USA), accuracy 2–4 m (lower accuracy under the tree canopy). These spatial data ensured full geographic traceability across the entire park area. Depending on park size and accessibility, one or two visits were carried out to ensure near-complete coverage.

Photographic documentation of each fungal basidiocarp was made. The assignation to species of the individual wood-decaying fungi was recorded according to the available monographs and keys provided [26,27,28]. The Latin names of fungi were adopted from the Index Fungorum database, and the Latin names of plants according to Mirek et al. [29]. To enhance the accuracy of identifications, each observed basidiocarp was carefully examined for a set of macroscopic characteristics, such as color, shape, size, and texture. Additionally, for retrospective verification, photographs of each specimen were assessed. The age of fungal fruiting bodies and host trees was estimated based on field observations and general knowledge of their growth patterns and developmental stages. For trees, age estimation was conducted by assessing the circumference of trunks and applying general growth rates for the species observed, which, although approximate, is a commonly accepted method in preliminary ecological studies. As for fungi, the estimation was grounded on the size and developmental phase of the fruiting bodies, in comparison with documented lifecycles of similar species in mentioned keys. The evaluation of the results was necessary for creating the comprehensive database containing all collected data during the field research.

2.3. Statistical Analyses

To evaluate the diversity and distribution patterns of wood-inhabiting fungi among the studied urban parks, a series of statistical analyses was conducted. First, as a basic index of relative frequency, fungal occurrence density (expressed as the number of findings per ha) was calculated for each park by dividing the total number of fungal observations by the park area.

To compare species richness and community structure, the Shannon diversity index (H’) and Simpson’s diversity index (D) were calculated for each park [30,31]. The calculations were performed using the following formulas: H’ = −Σ P_i(lnP_i) and D = 1−Σ P_i², where P_i stands for the proportion of each species in the sample.

Furthermore, a chi-square (χ²) test of independence was applied to examine the statistical significance between fungal species distribution and the studied park site, by using the following formula: χ² = Σ[(O_i − E_i)²/E_i], where O_i represents observed frequencies, while E_i expected frequencies.

Additionally, the non-parametric Kruskal–Wallis H test was also used to evaluate whether the total number of fungal occurrences differed significantly between parks, by using the following formula: H = [12/(N(N + 1))] × Σ(R_i² n_i) − 3(N + 1), where N is the total number of observations, R_i is the sum of ranks for group i, and n_i is the number of observations in group i.

Fungal species similarity between parks was also assessed using Jaccard coefficients and visualized with UPGMA-based hierarchical clustering [31]. The Jaccard index was calculated as J = a/(a + b + c), where a is the number of species shared between two sites, and b and c are the numbers of species unique to each site.

All calculations were performed in Microsoft Excel, while the Jaccard dendrogram was generated in Python 3.10 and graphically refined in Microsoft PowerPoint.

3. Results

During the field research, samples were collected from five selected parks in the city of Wrocław (Lower Silesia, Poland): Wschodni, Zachodni, Grabiszyński, Południowy, and Brochowski (Figure 2A). Among all the investigated areas, Zachodni Park displayed the highest number (19 specimens) of wood-inhabiting fungi, whereas Wschodni (12 specimens) and Południowy (10 specimens) Parks were the second and third most abundant, respectively. In the case of Brochowski and Grabiszyński Parks, seven and five wood-inhabiting fungi sites were recorded, respectively.

When adjusted for park size, fungal occurrence density revealed additional insights. The highest density was recorded in Brochowski Park (0.88 findings/ha), despite its small area (8 ha), followed by Południowy (0.40/ha), Wschodni (0.37/ha), and Zachodni (0.25/ha) Parks. The lowest density was found in Grabiszyński Park (0.10/ha), which represents the second largest park in the present study.

However, the overall abundance of wood-inhabiting fungi did not differ significantly between the studied parks, as indicated by the Kruskal–Wallis test (H = 3.46, p = 0.484). However, a marginally non-significant result from the chi-square test (χ² = 45.75, df = 32, p = 0.055) suggests a potential trend toward variation in fungal species composition across sites. These observations were further supported by diversity indices. The highest species diversity, as measured by both the Shannon (H’ = 1.62) and Simpson (D = 0.78) indices, was recorded in Zachodni Park. In contrast, the lowest diversity values were observed in Brochowski Park (H’ = 0.96; D = 0.57), indicating a community dominated by fewer taxa. Intermediate values were found in the remaining sites, with moderate diversity in Południowy (H’ = 1.19; D = 0.66) and Wschodni (H’ = 1.10; D = 0.53), and relatively low but more balanced diversity in Grabiszyński Park (H’ = 1.05; D = 0.64).

In total, 53 findings (eight genera, nine spp.) of wood-inhabiting fungi were recorded in the selected parks (Figure 2B). Most (73.5%) of the recorded fungal specimens were inhabiting higher parts of the trees (growth on medium height and above), whereas only 26.5% were recorded at the base of the trunks or in lower parts of the trees (Figure 2C). The similarity in fungal species composition among parks was further analyzed using Jaccard coefficients and visualized with hierarchical clustering (Figure 2D). The greatest similarity was observed between Wschodni and Zachodni Parks, followed by a secondary cluster formed by Grabiszyński and Południowy Parks. Brochowski Park appeared the most distinct in terms of fungal community composition.

The most commonly occurring fungal taxa belong to the polypore group and consist of Fomes fomentarius (23 specimens), Fomitiporia robusta (P. Karst.) Fiasson and Niemelä (eight specimens), and Laetiporus sulphureus (seven specimens) (Figure 2B and Figure A1). F. fomentarius was recorded mostly on damaged, old tree specimens.

The less common fungal taxa were as follows: unassigned species of the genera Inocutis Fiasson and Niemelä and Fomitopsis betulina (each occurring at five different sites), Ganoderma adspersum (Schulzer) Donk (occurring at two different sites), and individual findings for the following: Fomitopsis pinicola (Sw.) P. Karst., G. adspersum (Schulzer) Donk, H. annosum, Stereum rugosum Pers., Trametes gibbosa (Pers.) Fr. (Figure A2).

In general, the wood-inhabiting fungi colonized eight spp. of the host trees, which belong to six genera—Acer, Betula, Carpinus, Fagus, Quercus, and Salix (

Table 1. The number of tree spp. identified in the study that were infected by different wood-inhabiting fungal spp. U/I—unidentified.

Fungal spp.	Tree spp. or Type
	Acer pseudoplatanus	Betula pendula	Carpinus betulus	Fagus sylvatica	Quercus petraea	Quercus robur	Quercus rubra	Salix babylonica	U/I
Inocutis sp.						5
Fomitopsis betulina		5
Fomes fomentarius	2	7	1	1		3	1	1	7
Fomitopsis pinicola					1
Fomitiporia robusta						5	3
Ganoderma adspersum						1			1
Laetiporus sulphureus			4	1		1	1
Bjerkandera fumosa	1
Trametes gibbosa						1

). The most affected spp. were Q. robur (16 specimens) and B. pendula (12 specimens). However, out of the 53 study sites, eight tree spp. were cut or heavily damaged and thus unidentifiable (U/I). Interestingly, the presence of specific fungal spp. was generally noticeable only on certain tree spp.—Inocutis sp. occurred on Q. robur, F. betulina on B. pendula, F. pinicola on Q. petraea, Ganoderma adspersum on Q. robur, and an U/I cut gymnosperm tree, Bjerkandera fumosa on A. pseudoplatanus, and Trametes gibbosa on Q. robur. Only the most abundant fungi recorded in this study—the polypore species Fomes fomentarius, Fomitiporia robusta, and Laetiporus sulphureus—were observed on more than one tree species.

A detailed analysis of the wood-inhabiting fungi and tree spp. distribution in different city parks, geographic coordinates, site descriptions, and additional data is included in the next sections (Section 3.1, Section 3.2, Section 3.3, Section 3.4 and Section 3.5,

Table 2. The number, coordinates, age, and condition of fungal spp. occurring in the area of Wschodni Park in Wrocław (Lower Silesia, Poland). Additional descriptive (descr.) data (host tree spp., condition, and presence of visible damage) are also given. U/I—unidentified. bcs—basidiocarps.

Site No.	Latitude (N)	Longitude (E)	Fungal spp.	Age and Condition of Basidiocarps
1	51°05′04.5″	17°04′34.4″	Fomes fomentarius	young bcs
descr.	growing high on a damaged, mature “weeping” willow (Salix babylonica’ Babylon’)
2	51°05′03.2″	17°04′37.1″	Ganoderma adspersum	mostly old bcs (greenish from above due to algae growth), also single young fb
descr.	growing on a tree cut from the top, at the base of the trunk and at medium height (U/I sp.)
3	51°05′02.9″	17°04′38.2″	F. fomentarius	old bcs, turning light to very dark green from above due to algae growth
descr.	growing on a decaying trunk (outside and inside the trunk) (U/I sp.)
4	51°05′03.9″	17°04′38.5″	F. fomentarius	young single bcs, the edge of which was light green in color
descr.	growing on a damaged, broken tree (U/I sp.)
5	51°05′03.9″	17°04′40.0″	F. fomentarius	young bcs
descr.	growing on trunks (U/I tree sp.)
6	51°05′04.0″	17°04′46.2″	F. fomentarius	young bcs
descr.	growing on a very damaged, long-term pedunculate oak (Quercus robur)
7	51°05′00.8″	17°04′53.6″	F. fomentarius	middle-aged bcs
descr.	growing high on a tree cut from above (U/I tree sp.)
8	51°05′04.9″	17°05′05.7″	F. fomentarius	young bcs
descr.	growing high on a tree cut from above (U/I tree sp.)
9	51°05′04.9″	17°05′03.6″	Fomitiporia robusta	middle-aged single bcs
descr.	growing on a mature pedunculate oak, at medium height (Q. robur)
10	51°05′11.3″	17°05′05.6″	Trametes gibbosa	young bcs
descr.	numerous specimens growing on a young pedunculate oak (Q. robur)
11	51°05′10.9″	17°05′05.6″	Inocutis sp.	old bcs
descr.	growing high on a middle-aged pedunculate oak (Q. robur)
12	51°05′09.4″	17°05′18.1″	F. fomentarius	young single bcs
descr.	growing high on a mature pedunculate oak (Q. robur)

,

Table 3. The number, coordinates, age, and condition of fungal spp. occurring in the area of Zachodni Park in Wrocław (Lower Silesia, Poland). Additional descriptive (descr.) data (host tree spp., condition, and presence of visible damage) are also given. bcs—basidiocarps.

Site No.	Latitude (N)	Longitude (E)	Fungal spp.	Age and Condition of Basidiocarps
1	51°07′48.7″	16°58′20.4″	Fomitopsis betulina	middle-aged bcs
descr.	growing high on a Betula pendula cut from above
2	51°07′50.9″	16°58′19.1″	F. betulina	young bcs
descr.	growing high on a mature B. pendula
3	51°07′51.2″	16°58′17.8″	Ganoderma adspersum	old bcs
descr.	growing on a mature pedunculate oak, at medium height (Quercus robur)
4	51°07′49.6″	16°58′24.3″	Fomes fomentarius	young single bcs
descr.	growing high on a mature B. pendula
5	51°07′44.2″	16°58′32.7″	F. fomentarius	young bcs (top) and single older one (bottom)
descr.	numerous specimens growing on a middle-aged B. pendula
6	51°07′43.9″	16°58′32.9″	F. fomentarius	young bcs
descr.	numerous specimens growing on a middle-aged B. pendula
7	51°07′44.3″	16°58′34.9″	Laetiporus sulphureus	young bcs
descr.	growing at the base of the trunk of a mature Carpinus betulus
8	51°07′43.9″	16°58′35.0″	L. sulphureus	young single bcs
descr.	growing high on a mature C. betulus
9	51°07′43.7″	16°58′37.3″	Inocutis sp.	old bcs
descr.	growing on a mature Q. robur at medium height
10	51°07′46.6″	16°58′40.9″	L. sulphureus	young bcs
descr.	growing on a mature Quercus rubra at medium height
11	51°07′46.0″	16°58′42.5″	Inocutis sp.	old bcs
descr.	growing high on a mature Q. robur
12	51°07′46.1″	16°58′42.8″	L. sulphureus	young bcs
descr.	growing low on a mature Q. robur
13	51°07′48.0″	16°58′37.1″	F. fomentarius	damaged, young bcs
descr.	growing low and high on a tree cut from the top B. pendula
14	51°07′47.1″	16°58′33.6″	F. betulina	young single bcs
descr.	growing high on a mature B. pendula
15	51°07′51.8″	16°58′25.9″	Inocutis sp.	old bcs, taking on a greenish color over the entire surface due to algae growth
descr.	growing high on a mature Q. robur
16	51°07′52.2″	16°58′25.9″	Fomitiporia robusta	old bcs, turning green from above due to algae growth
descr.	growing at an average height on mature Q. robur
17	51°07′52.4″	16°58′25.2″	Inocutis sp.	old bcs
descr.	growing at an average height on mature Q. robur
18	51°07′53.4″	16°58′08.3″	F. fomentarius	young bcs, one taking on a greenish color over the entire surface due to algae growth
descr.	growing at an average to high height on a mature B. pendula
19	51°07′52.5″	16°58′08.2″	F. fomentarius	young bcs
descr.	growing at an average height on a mature B. pendula

,

Table 4. The number, coordinates, age, and condition of fungal spp. occurring in the area of Grabiszyński Park in Wrocław (Lower Silesia, Poland). Additional descriptive (descr.) data (host tree spp., condition, and presence of visible damage) are also given. bcs—basidiocarps.

Site No.	Latitude (N)	Longitude (E)	Fungal spp.	Age and Condition of Basidiocarps
1	51°05′26.8″	16°58′49.5″	Fomitopsis betulina	young bcs
descr.	growing on a mature Betula pendula, at medium height
2	51°05′25.7″	16°58′47.8″	F. betulina	young bcs
descr.	growing on a mature B. pendula cut from the top, at medium height
3	51°05′29.3″	16°58′51.6″	Laetiporus sulphureus	old bcs
descr.	growing at the base of the trunk of a mature Carpnius betulus
4	51°05′28.7″	16°58′51.3″	L. sulphureus	young bcs
descr.	growing at the base of the trunk of a mature C. betulus
5	51°05′23.7″	16°58′56.8″	Fomes fomentarius	young bcs
descr.	growing on a mature B. pendula, at medium height and a little below

,

Table 5. The number, coordinates, age, and condition of fungal spp. occurring in the area of Południowy Park in Wrocław (Lower Silesia, Poland). Additional descriptive (descr.) data (host tree spp., condition, and presence of visible damage) are also given. U/I—unidentified. bcs—basidiocarps.

Site No.	Latitude (N)	Longitude (E)	Fungal spp.	Age and Condition of Basidiocarps
1	51°04′28.7″	17°00′44.7″	Fomitopsis pinicola	old single bcs
descr.	growing at the base of the trunk of Quercus petraea
2	51°04′26.1″	17°00′43.5″	Laetiporus sulphureus	old single dried up bcs
descr.	growing high on Fagus sylvatica
3	51°04′25.8″	17°00′41.7″	Fomitiporia robusta	middle-aged single bcs
descr.	growing high on Quercus rubra
4	51°04′26.2″	17°00′40.7″	F. robusta	old single bcs, greenish from above due to algae growth
descr.	growing high on Q. rubra
5	51°04′25.7″	17°00′40.3″	F. robusta	old single bcs
descr.	growing high on Quercus robur
6	51°04′24.7″	17°00′40.0″	Fomes fomentarius	middle-aged single bcs
descr.	growing high on a tree cut from above (U/I tree sp.)
7	51°04′36.0″	17°00′43.4″	F. fomentarius	old bcs
descr.	growing on F. sylvatica, on medium height
8	51°04′36.1″	17°00′40.5″	F. fomentarius	middle-aged and old bcs
descr.	numerous specimens on Q. robur
9	51°04′33.1″	17°00′36.7″	F. fomentarius	young bcs
descr.	growing high on Q. rubra
10	51°04′29.8″	17°00′38.9″	F. robusta	old bcs, greenish from above due to algae growth
descr.	growing high on Q. rubra

and

Table 6. The number, coordinates, age, and condition of fungal spp. occurring in the area of Brochowski Park in Wrocław (Lower Silesia, Poland). Additional descriptive (descr.) data (host tree spp., condition, and presence of visible damage) are also given. U/I—unidentified. bcs—basidiocarps.

Site No.	Latitude (N)	Longitude (E)	Fungal spp.	Age and Condition of Basidiocarps
1	51°03′37.6″	17°04′22.0″	Fomitoporia robusta	old bcs, turning green from above due to algae growth
descr.	growing high on a mature Quercus robur
2	51°03′36.9″	17°04′21.9″	Fomes fomentarius	young single bcs
descr.	growing high on a mature Acer pseudoplatanus
3	51°03′36.2″	17°04′20.8″	F. robusta	old bcs, turning green from above due to algae growth
descr.	growing at an average height on a mature Q. robur
4	51°03′35.6″	17°04′15.4″	F. fomentarius	young bcs
descr.	growing high on a mature A. pseudoplatanus
5	51°03′37.5″	17°04′15.1″	F. fomentarius	three young bcs and single old fb
descr.	growing high on a tree cut from above a mature Carpnius betulus
6	51°03′40.6″	17°04′17.6″	Bjerkandera fumosa	middle-aged bcs
descr.	growing from the bottom to a medium height on a damaged, mature A. pseudoplatanus
7	51°03′44.8″	17°04′18.2″	F. fomentarius	young bcs
descr.	growing on a mature tree cut from the top, at the base of the trunk (U/I tree sp.)

).

3.1. Species Records–Wschodni Park

A total of 12 wood-inhabiting fungi sites were recorded in the Wschodni Park area, with the dominant species being Fomes fomentarius (eight sites throughout the area). The fewest sites (three) were observed in the northeastern part of the park, including single sites for F. fomentarius, Inocutis sp., and Trametes gibbosa. The most sites were situated in the southern and western parts, with seven sites of F. fomentarius, as well as single sites for Fomitiporia robusta (in the southern part of the park) and Ganoderma adspersum (in the western part of the park). The identified sites were mostly located far from walking paths, with only the sites in the northeastern part of the park being located near paths. No fungal occurrence sites were recorded in the central, northern, and eastern parts of the park. Most of the fungal specimens were found inhabiting trunks or trees that had been cut from above or damaged, with only six sites allowing for tree species identification (five sites of Quercus robur and a single site of Salix babylonica ‘Babylon’). The collective data are included in Table 2.

3.2. Species Records–Zachodni Park

The largest amount of wood-inhabiting fungi sites (19) was recorded in the Zachodni Park area, with Fomes fomentarius (six sites) being the dominant species in the area. In the southwestern part of the park, three sites of F. fomentarius, two sites of Fomitopsis betulina, and a single site of G. adspersum were observed. In the southern part, the predominant species were Laetiporus sulphureus (four sites) and Inocutis sp. (four sites). Additionally, in the southern part, sites of F. fomentarius (three), F. betulina (one), and Fomitiporia robusta (one) were recorded. The identified sites were located near walking paths. No sites were recorded in the northwestern, northeastern, and southeastern parts of the park. In the case of inhabited tree species, the most abundant were Betula pendula (nine sites) and Quercus robur (seven sites). Additionally, two sites of Carpinus betulus and a single Quercus rubra site were recorded. The collective data are included in Table 3.

3.3. Species Records–Grabiszyński Park

Despite its large area, only five wood-inhabiting fungi sites were recorded in Grabiszyński Park. The observed specimens were Fomitopsis betulina (two sites), Laetiporia sulphureus (two sites), and Fomes fomentarius. These identified sites were located near walking paths in the northern part of the park. No sites inhabited by fungi were observed in the remaining study area. In terms of host tree species, three sites of Betula pendula and two sites of Carpinus betulus were recorded. The collective data are included in Table 4.

3.4. Species Records–Południowy Park

A total of 10 fungal occurrence sites were identified in the Południowy Park. The dominant species were Fomes fomentarius (four sites) observed in the northern (three sites) and southern (one site) parts of the park, as well as Fomitiporia robusta (four sites) in the southern part. A single site was recorded for Laetiporus sulphureus and Fomitopsis pinicola close to the southeastern border of the park. These sites were located both near and far from walking paths. No fungi sites near the border of the northern and western sides of the park were recorded. Most of the specimens were recorded to inhabit Quercus rubra (four sites). Additionally, two sites were recorded for Quercus robur and Fagus sylvatica, as well as a single site for Quercus petraea (Matt.) Liebl. and U/I cut tree sp. The collective data are included in Table 5.

3.5. Species Records–Brochowski Park

Despite being the smallest park in the study, a total of seven fungal occurrence sites were recorded in Brochowski Park. The dominant species was Fomes fomentarius, which occurred in the northern, southeastern, and southwestern parts of the park. Two sites of Fomitiporia robusta were identified in the southeastern part of the park, and a single site of Bjerkandera fumosa was found in the western part of the park. Two F. fomentarius sites were located near walking paths, while the others were far from the paths. No fungal occurrence sites were recorded in the southern part of the park. Most of the specimens were found to inhabit Acer pseudoplatanus (three sites). Additionally, two sites of Quercus robur, as well as single sites for Carpinus betulus and an U/I trunk species, were recorded. The collective data are included in Table 6.

4. Discussion

The occurrence and the species diversity of the wood-inhabiting fungi are affected by environmental pollution and natural habitats [32,33]. In this study, we surveyed five selected parks in Wrocław to detect common wood-decay fungi. However, it should be emphasized that only easily visible basidiocarps were recorded, excluding small basidiocarps of polyporoid, corticioid, cyphelloid, tremelloid, or small-sized representatives of agaricoid fungi. We believe that a more thorough exploration of various wood elements (e.g., small tree branches) should result to find a range of ubiquitous/common fungal species, such as Peniophora cinerea (on various tree species), Peniophora quercina (mostly on Quercus spp.), Vuilleminia comedens (e.g., on Quercus spp.), and many others as stated by Sunhede [34]. Nevertheless, in terms of abundance, the major fungi found in this study belong to the polypore group and were Fomes fomentarius, Fomitiporia robusta, and Laetiporus sulphureus. Interestingly, at the same time, only these three species were detected to inhabit more than one tree species.

In Poland, Fomes fomentarius is very common throughout the country [35]. Indeed, F. fomentarius was the most common species identified in the present study, but also the least selective in terms of substrate—the infected tree individuals belong to six genera: Acer, Betula, Carpinus, Fagus, Quercus, and Salix. F. fomentarius was already reported to be commonly found on different species of the hardwoods [36]. The common polypore is a perennial species, occurring throughout the year on weakened deciduous trees (especially Fagus spp. or Betula spp.). In addition, it is found in most types of forests, including riverside riparian forests, where it grows on Populus spp. The polyphagous nature of F. fomentarius is constantly being reported even in the case of uncommon tree species such as Salix × sepulcralis ‘Tristis’ [32]. Additionally, F. fomentarius might infect the following tree genera: Quercus, Acer, Prunus, Carya, Tilia, Alnus, Carpinus, and Coniferae spp. [28]. Hagara et al. [36] also reported that F. fomentarius is very abundant on dead wood. It should be noted, however, that recent studies suggest that Fomes fomentarius may represent a complex species, with F. fomentarius sensu stricto typically associated with Betula in Europe, and other cryptic lineages potentially inhabiting different host species [37,38].

Here, F. fomentarius was the most prevalent polypore species found on U/I tree spp. (seven out of eight occurrences), mostly dead due to heavy damage, cutting, or as a cause of fungal saproparasitic activities. Additionally, its occurrence represented 43.4% of all collected wood-inhabiting fungal species. In terms of the Central Europe region studied, recently, it was also observed that F. fomentarius was one of the most common causes of infection in urban areas of the Czech Republic [39]. Additionally, Kobza et al. [40] reported that F. fomentarius was the most occurring taxon in urban areas (including city parks) in different cities in Slovakia. Both studies mention broad tree failure due to F. fomentarius infection, including wood decay and high degree of damaged area on tree trunks.

Fomitiporia robusta was the second most abundant polypore species observed in the study. In Poland, this fungus is not considered a common species and most often occurs in parks, deciduous, and mixed forests, usually on Quercus robur [35,41]. However, F. robusta has been documented to infect Fagus spp., Crataegus spp., and Robinia spp. [26]. Here, out of eight tree individuals infected by F. robusta, five were identified as Q. robur, and the others were identified as Quercus rubra. Similarly to Fomes fomentarius, F. robusta is both a parasite and a saprotroph, causing intense white wood rot. The metabolic products and enzymes of the pathogen have negative effects on the cambial tissues and sapwood. This results in the formation of spindle-shaped, strongly elongated, irregular cankers on the trunks of living trees [42].

Laetiporus sulphureus usually infects deciduous trees (Quercus, Salix, Populus, and Robinia spp.) and rarely grows on conifers [27]. Here, we noticed L. sulphureus only on deciduous trees from the genera Carpinus, Fagus, and Quercus. Interestingly, L. sulphureus is also commonly found on wooden structures, such as ships, boats, and fence posts [43]. This fungus leads to the formation of intense brown wood rot (first in the heartwood, then in the sapwood) and to the formation of the so-called ‘hollow’. The resulting rotting of the wood occurs in the base and trunk of the infected tree and in the roots. Additionally, tyrosinase produced by L. sulphureus has a neutralizing effect on the phenolic compounds contained in the wood. Within a few years, a tree attacked by this fungus dies [43].

The less common polypore specimens in the study were Inocutis sp. and Fomitopsis betulina (five instances of each). Both fungi are characterized by a narrow range of infected tree species—Inocutis sp., including Inocutis dryophila, is typically found on Quercus species and considered a specialist saprotroph inhabiting dead or decaying oak wood [44]. F. betulina, in turn, inhabits only Betula pendula [45]. In terms of rotting, both polypores lead to the formation of intense brown wood rot [46]. In the present case, both polypores were recorded on their corresponding tree species. Additionally, F. betulina is considered common in the region of Poland [35]. However, the growth period of F. betulina is reported to vary, with some sources indicating its active growth phase only from August to October, while others from June to September [47]. Although, dead specimens may be encountered year-round [47]. Despite the fact that the present study lasted from January to July, four out of five F. betulina sites were characterized by young basidiocarps. It is noteworthy that some specimens of F. betulina were described to survive the winter and produce a new layer of tubes in spring [11]. This suggests that, rather than solely attributing such occurrences to the potential effects of progressive climate change—a decade apart from the conclusions made by Giminder [47]—the unique urban climate and the presence of urban heat islands might play a significant role in shaping the specific phenology of fungi in urban ecosystems [48]. The aforementioned conclusion leads to the continuation of studies aimed at comparing the species diversity of wood-inhabiting fungi throughout different seasons of the year in the studied areas of urban parks. We believe that such study might lead to novel conclusions on the current state of the biology of wood-inhabiting fungi, including polypores.

In the present study, we also recorded two sites for Ganoderma adspersum, as well as single sites per Fomitopsis pinicola, Trametes gibbosa, and Bjerkandera fumosa. All wood-inhabiting fungal species are common in Europe and Poland and display polyphagous nature [35,47,49]. However, only infection with F. pinicola results in brown rotting of the wood, whereas the other fungal species are a cause of white rotting. Interestingly, here F. pinicola, G. adspersum, and T. gibbosa were all identified as inhabiting Quercus spp., while B. fumosa infected Acer pseudoplatanus. On the other hand, another G. adspersum site was detected on U/I damaged cut tree trunk, which was the only incidence despite Fomes fomentarius. This may be explained by the opportunistic nature of G. adspersum, which is known to colonize weakened or mechanically damaged trees, especially through wounds in the lower stem or root collar, where it can act as a vigorous pathogen causing white rot [50,51].

In studies focused on polypores and other macroscopic lignicolous fungi, species identification is still based on morphological characteristics and ecological context, including substrate and host specificity [52,53,54,55,56,57,58,59]. However, there is a growing trend toward integrating molecular techniques, such as ITS barcoding, to resolve cryptic species and refine taxonomic resolution. In our study, identifications were based solely on macroscopic features and field keys, which introduce limitations—particularly for morphologically similar taxa such as Inocutis sp. We acknowledge this shortcoming and note that molecular tools would have improved taxonomic accuracy in future research. In terms of the study sites, we observed some interesting occurrences. The most abundant wood-inhabiting fungi sites in Zachodni Park are most likely a result of significantly weakened tree stand due to old age and damage caused by former natural phenomena, such as the flood of 1997 and the storm of 2006. An even more significant deterioration in the health of the stand in the southern and southwestern parts of the park is expected. Similarly, progressive deterioration is expected in Wschodni, Brochowski, and Południowy Parks. In the case of Południowy Park, all identified fungal species must have occurred in the last century, as none of them is listed by the Dittrich [12] list of macrofungi within this area. Examples of enlisted wood-inhabiting fungi are as follows: Polystictus hirsutus (Wulf.) Fr. (cur. Trametes hirsuta (Wulfen) Lloyd); Polystictus zonatus (Nees) Bres. (cur. Trametes ochracea (Pers.) Gilb. and Ryvarden); and Hypholoma fasciculare (Huds.) Fr., out of which none was present in the current studies. However, in all cases, the occurrence of fungi in the identified sites is caused by the old age of the trees. The exception was the case of Trametes gibbosa infecting a young specimen of Quercus robur in Wschodni Park. However, the tree was characterized by serious injuries through which spores might have penetrated. In the case of Grabiszyński Park, the lowest number of sites were recorded due to the well-kept tree stand despite their age. The occurrence of polypores was recorded only in the northern part, most likely due to the maintenance work, which could have injured the trees and opened the gateway for infection.

Differences in fungal species richness and composition among the surveyed parks may be attributed to a combination of ecological and structural factors. For example, Zachodni Park, which showed the highest number of occurrences, is one of the largest and most structurally diverse green areas in the city, with mature tree stands and lower levels of human interference in certain sections. In contrast, Grabiszyński Park, which had the fewest observations, is more intensively managed and includes large open areas with fewer decaying trees. Wschodni Park, while moderately rich in species, contains sections affected by past flooding events, which may have contributed to tree damage and subsequent fungal colonization. Additionally, variation in host tree species composition and availability likely influenced the observed patterns, particularly for species with known host preferences such as Fomes fomentarius or Laetiporus sulphureus. These local habitat and disturbance conditions should be considered when interpreting fungal distribution in urban environments. Notably, when fungal occurrence was normalized for the park area, a different pattern emerged. Brochowski Park, although the smallest among the surveyed sites, exhibited the highest density of fungal findings per hectare. Similarly, Południowy and Wschodni Parks showed relatively high densities despite moderate absolute counts. This suggests that small or historically modified parks may still support rich fungal communities when habitat conditions such as deadwood availability or tree age are favorable. Therefore, both absolute abundance and relative density metrics should be considered when assessing fungal presence in heterogeneous urban landscapes.

Interestingly, various studies conducted in Poland have documented the occurrence of similar wood-inhabiting fungi. In recent research by Kujawa et al. [60], several tree-associated fungal species were identified in the Palace Park in Poznań-Radojewo, including Fomes fomentarius, Fomitopsis betulina (referred to as Piptoporus betulinus), Fomitopsis pinicola, and Laetiporus sulphureus. These species are recognized for their ecological importance within the park’s ecosystem, underscoring their roles and presence in this specific urban green space. This complements our research in identifying similar species in city parks in Wrocław, offering a comparative view of fungal diversity in urban parks throughout Poland. Additionally, Wojewoda [61] examines the macrofungi in Krakow, noting the presence of F. pinicola and F. fomentarius and the trend of decreasing macrofungal diversity due to environmental changes and pollution. This observation underscores significant shifts in fungal populations within urban environments, providing valuable insights for comparison with fungal species found in parks across Poland, including Wrocław. Moreover, Wołkowycki [62] presents detailed information on polypore fungi in Białystok, featuring species such as F. fomentarius, F. pinicola, and L. sulphureus, which are among the tree-associated fungi we identified. Wołkowycki’s work [62] highlights the ecological roles and diversity of these fungi in both urban and forested areas of Białystok, serving as an invaluable reference for comparing the presence and ecological significance of similar species in various Polish locales, including parks in Wrocław.

Despite the limited dataset, several statistical approaches provided valuable ecological insights. Notably, diversity indices revealed clear differences in species richness and evenness among parks, with the highest values of Shannon and Simpson indices recorded in Zachodni Park, suggesting a more complex and balanced fungal community. In contrast, Brochowski Park showed the lowest diversity, indicating a simplified fungal assemblage dominated by fewer species. The Jaccard-based clustering analysis further supported these patterns, revealing a distinct grouping of Wschodni and Zachodni Parks, and a separate cluster comprising Grabiszyński and Południowy Parks, while Brochowski appeared markedly different from the rest. Although the total number of fungal findings did not differ significantly across parks (Kruskal–Wallis test), and the species distribution pattern approached but did not reach statistical significance (χ² test, p = 0.055), these analyses collectively suggest site-specific trends in fungal community composition that merit further investigation with larger datasets. However, given the limited number of fungal occurrences and the uneven distribution of records across parks and taxa, the statistical power is limited. Therefore, the results should not be interpreted as conclusive. Instead, the analyses help visualize emerging patterns and highlight potential differences in species composition among parks, serving as a basis for more comprehensive future studies.

Urban forests are valuable in many ways, and a better understanding of wood-inhabiting fungi diversity in such areas facilitates the protection and management of trees. Jim and Zhang [63] suggested that regular inspections should be conducted for proactive management, as early detection of polypore infection allows for preserving trees due to removing affected tissues. All investigated parks in Wrocław receive a large number of visitors daily; therefore, weakened trees might be hazardous if not identified and removed in time. However, proper identification of the fungal species is also necessary to assess whether root rot occurs, as despite removing a diseased tree, it is imperative to clean up the infected area for replanting new specimen. The methodology employed based on macroscopic characteristics and comparative analysis presents both strengths and inherent limitations. While this approach enabled the broad cataloging of fungal diversity across the studied ecosystems, it also underscores the critical need for precision in ecological research. We recognize that the reliance on macroscopic identification can lead to potential inaccuracies, particularly in differentiating species with subtle morphological differences. Such challenges highlight the importance of integrating more rigorous identification techniques in future studies to enhance the reliability of fungal classifications. Additionally, we believe that a further understanding of the occurrence of specific wood-inhabiting fungal species on specific tree species might result in better planning of urban forests in the future, such as planting tree species that are naturally resistant to hazardous fungal species. However, it should be acknowledged that some of the herein estimations (including tree and fungi age) were preliminary and were utilized to provide an initial understanding of the biodiversity and distribution of fungi in the studied locations. Future research endeavors may benefit from incorporating more precise age determination techniques, such as dendrochronology for trees and advanced microscopic analyses for fungi, to refine these findings. The methodology adopted reflects the exploratory nature of this study and signifies an openness to further investigation and refinement in subsequent research.

5. Conclusions

The occurrence of wood-inhabiting fungi in city parks still receives little attention, despite considerable economic interest. In urban planning, trees are usually treated as architectural elements rather than living organisms. Hence, we are of the opinion that species diversity of tree pathogens in urban areas is of utmost importance. During 2021, we recorded 53 findings of polypores (eight genera, nine species) in five parks in the city of Wrocław, Lower Silesia, Poland. The most abundant taxa belong to polypores and were Fomes fomentarius (43.4%), Fomitiporia robusta (15%), and Laetiporus sulphureus (13.2%). Wood-inhabiting fungi sites were most frequent near walking paths. The greatest number of findings was recorded in the Zachodni Park (19 sites, 35.8%), whereas the least was in Grabiszyński Park (five sites, 9.4%). The fungi colonized six genera and eight species of host trees. Out of the 53 study sites, eight tree sp. were damaged or cut and thus unidentified. The most affected were Quercus robur (35.5%) and Betula pendula (26.7%). The fungi colonized different parts of host trees, with the greatest number of specimen observed in the higher parts. Most polypore fungi were identified on trees with old, damaged, weakened, or decaying stumps, confirming the theory that polypores are pathogens of weakness and proving their destructive effect on inhabiting the tree/wood. Thus, the progressive decomposition of lignin, hemicellulose, and cellulose components of wood at the identified sites should be expected. Additionally, all investigated parks in Wrocław receive a large number of visitors daily; therefore, weakened trees might pose a threat to humans if not removed in time.