Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems

Solomou, Alexandra D.; Athanasiou, Miltiadis; Korakaki, Evangelia; Michopoulos, Panagiotis; Karetsos, Georgios

doi:10.3390/d17110768

Open AccessArticle

Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems

by

Alexandra D. Solomou

^*

,

Miltiadis Athanasiou

,

Evangelia Korakaki

,

Panagiotis Michopoulos

and

Georgios Karetsos

Institute of Mediterranean Forest Ecosystems (IMFE), ELGO-DIMITRA, Terma Alkmanos, Ilisia, 11528 Athens, Greece

^*

Author to whom correspondence should be addressed.

Diversity 2025, 17(11), 768; https://doi.org/10.3390/d17110768

Submission received: 19 September 2025 / Revised: 10 October 2025 / Accepted: 20 October 2025 / Published: 3 November 2025

(This article belongs to the Special Issue Restoring and Conserving Biodiversity: A Global Perspective)

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Abstract

Mediterranean ecosystems are highly susceptible to wildfires, and shifts in fire patterns pose a threat to biodiversity, soil stability, and overall ecosystem health resilience. Implementing prescribed burning as a management strategy to lower wildfire risk has been proposed, but its ecological impacts in Greece are not well understood. This study examines the relationship between fireline intensity during prescribed burning and plant water potential, as well as its effects on soil properties and plant biodiversity on Chios Island, Greece. Field experiments were carried out in representative ecosystems, where we measured flame length to determine fireline intensity. In addition, we gathered soil samples before and after the prescribed burning and evaluated plant diversity. Measuring leaf water potential gave us a better understanding of how plants respond physiologically to different seasonal and site conditions. Our findings revealed that prescribed burning typically boosted plant diversity after the fire, with Fabaceae and Asteraceae playing a key role in regeneration. However, the soil responses differed from one site to another. Some sites saw a decline in organic carbon and nitrogen, while others showed an increase in exchangeable cations like calcium and magnesium, highlighting the importance of site-specific results. Studies on plant water potential revealed seasonal fluctuations in stress, underscoring the importance of accounting for seasonality in prescribed burn planning. Overall, prescribed burning has the potential to enhance biodiversity and ecosystem recovery, while also reducing fuel loads. These results highlight the importance of ongoing, site-specific monitoring for developing sustainable fire management strategies in Mediterranean ecosystems.

Keywords:

prescribed burning; plant water potential; fireline intensity; soil properties; biodiversity; wildfire; Mediterranean

1. Introduction

Mediterranean ecosystems are globally recognized for their high biodiversity and the long-standing role of fire as a natural ecological factor shaping their structure and function [1,2]. Fire regimes, however, have been dramatically altered in recent decades due to land use changes, fire suppression policies, and climate change, resulting in more frequent, intense, and extensive wildfires [3].

Prescribed Burning (PB) is a fuel management method that offers multiple benefits [4], including wildfire hazard and risk reduction, enhanced forest ecosystem resilience, and biodiversity conservation [5,6]. The spatial and temporal scales of its implementation depend on fire management objectives, forest type, location, fire regime [7,8], and potential restrictions. Progress in adopting PB across Europe remains limited. In many regions, it is absent [9] while its use is mostly confined to fuel reduction in Portugal, Spain, and southern France, and to enhancing biodiversity in Sweden.

The need for an evidence-based and flexible approach to PB, emphasizing biology and habitat ecology, has been highlighted [10] along with a call to shift toward knowledge [11] that supports future research syntheses and fosters actionable science [12].

Unfortunately, planned PB experiments have been rare in Mediterranean ecosystems, despite their potential to provide valuable insights into fire impacts on soil properties and effects on trees. Eales et al. [13] noted that many studies on PB lack detailed reporting of fire behaviour metrics, such as fireline intensity (I, kW·m⁻¹) [14,15,16] and flame length (F_L, m). In subsequent years, however, researchers have attempted to correlate fire behaviour characteristics with biodiversity outcomes. Davies et al. [17] modelled fire behaviour during prescribed burns in Calluna heathlands, rather than measuring long-term biodiversity outcomes, while Zylstra [18] attempted to integrate detailed fire behaviour metrics, such as F_L and I, with ecological outcomes and fire effects related to plant traits. Ramberg et al. [19] conducted a 16-year study on PB and fungal (polypore) diversity in boreal forests. They compared burned and unburned stands, assessing coarse woody debris, fungal species richness, and the presence of red-listed species, but did not report detailed metrics of F_L or I.

Plant water potential serves as a key metric for assessing ecosystem health, particularly for evaluating plant responses to wildfire stress and tracking post-fire recovery [20]. Meanwhile, tracking biodiversity after prescribed burns offers valuable insights into whether ecosystems can preserve species diversity and ecological functions after disturbance [21]. It is worth noting that the severity of wildfires can affect both plant physiology and biodiversity patterns, but the link between these factors is not well understood in the Mediterranean region [22]. Furthermore, soil characteristics play a key role in determining how ecosystems respond to wildfires. Changes in soil characteristics caused by wildfires such as the amount of organic matter, nutrient availability, water infiltration, and microbial activity can significantly impact how plants recover after wildfires and biodiversity dynamics [23]. The intensity and severity of wildfires [24] directly affect how much soil is altered, with intense wildfires often causing soil to become water-repelling, nutrient loss, and damage to soil structure [25,26]. In Mediterranean environments, where soils are typically shallow and low in nutrients, understanding how prescribed burns impact soil properties is essential for predicting ecosystem resilience and developing sustainable fire management practices [27].

The first efforts to introduce and utilize the PB in Greece began in the 1970s [28], when members of the Greek forest scientific community and the Hellenic Forest Service applied PB experimentally, analyzed data and drew some preliminary conclusions [29]. They made some steps to document the use of fire and study its impacts, discussing also ecological and managerial issues as well as its potential combination with grazing and mechanical treatments [30].

Unfortunately, without sustained funding, legal support, logistics, ongoing scientific guidance, and clear objectives, the endeavour was soon abandoned. Almost half a century later, in 2021, a core team of researchers and practitioners started a pilot project on the implementation of the PB on the island of Chios aiming to introduce PB as a tool for forest fuel management, increase social–ecological resilience to wildfire and contribute to a climate-resilient future [31].

This study aims to address significant research gaps in the relationships among plant water potential, calculated Ι, post-burn vascular plant biodiversity and soil properties, to better understand fire effects associated with PB and, potentially, low-intensity wildfires. We utilized field recordings and F_L measurements collected during PB on Chios island, Greece [31], to calculate and examine its correlation with post-burn vascular plant biodiversity. For the first time in Greece, PB are being used to simultaneously examine these factors, thereby bridging the gaps between ecological theory and fire management practice. The findings provide actionable knowledge for sustainable fire management and biodiversity conservation in a changing environment and fire regime.

2. Materials and Methods

2.1. Study Area

Chios, the fifth largest island in Greece (842 km², coastline 229 km), is located in the central Aegean Sea and belongs to the North Aegean Region (Figure 1). Its relief is mainly mountainous-semi-mountainous, with steep slopes in the northern part and gentler ones in the southern part. The highest peak is Mount Pelinaio (1297 m), followed by other mountain peaks such as Mount (1126 m), Provatas (807 m) and Koklias (770 m), which create differentiated microclimatic conditions (Municipality of Chios, 2020).

The climate is typically Mediterranean (Csa, Köppen–Geiger), with hot and dry summers, mild and wet winters, a limited thermometric range and high summer drought [32].

The flora of Chios is of particular interest, as it is part of the thermo-Mediterranean vegetation zone (Oleo–Carpinetum). In the northern and mountainous parts, forests of Holm oak (Quercus ilex) and Calabrian pine (Pinus brutia) are found, while in the lower areas, maquis and phrygian vegetation dominate. Of particular importance is the endemic Fritillaria pelinaea, which was scientifically described from Mount Pelinae [33]. Furthermore, wild tulips (Tulipa agenensis, T. praecox, T. undulatifolia, T. clusiana) have been recorded on the island, which are typical elements of agro-pastoral ecosystems [34,35]. In particular, the cultivation of mastic (Pistacia lentiscus var. chia), unique worldwide, has been recognized as a Protected Designation of Origin (PDO) product and is a cultural and ecological landmark [36,37]. The fauna includes representative species of the Aegean. The presence of the otter (Lutra lutra) has been recorded in Chios, mainly in streams and coastal areas [38], while in the marine zones the habitat of the Mediterranean monk seal (Monachus monachus) is observed, although in limited numbers [39]. The bird fauna is rich, with the characteristic presence of the black-footed kestrel (Falco eleonorae) on microislets, such as the Venetian Islet (GR4130004) [40]. Significant parts of Chios and the surrounding islands are included in the Natura 2000 Network, which underlines their ecological value. Specifically, they include: GR4130001 “North Chios and Oinousses Islands and Coastal Marine Zone” (SAC), GR4130003 “North Chios” (SPA), GR4130004 “Venetiko Island (Chios)” (SPA), GR4130005 “Kalogeroi Rock Islands and Marine Zone” (SAC) [41]. These areas host habitats of community interest, such as Posidonia oceanica meadows (1120), reefs (1170), Sarcopoterium spinosum bryophytes (5420), riparian plane trees (92C0) and aloes (1410).

The main environmental threats include forest fires, which have caused significant ecological and economic losses (e.g., 2012, 2016, 2023, 2025) [42], uncontrolled construction, overgrazing, illegal fishing and hunting, as well as pressure from tourism development. Wildfires in particular pose a serious risk to the structure and functioning of ecosystems, as well as to mastic plantations.

2.2. Samplings

2.2.1. Vascular Plant Diversity

In the present study, vascular plant species were sampled at three designated sites: Resta, Aipos and Agios Stefanos (Figure 2). At each sampling site, plant species were recorded using four 1 m² quadrats within each selected experimental area, of the research site, both before and after the application of PB, as well as in controls [43] (Figure 3). To determine the plant samples, the “Flora Europaea” [44,45], the “Flora Hellenica” [46], and the vascular plants of Greece: an annotated checklist [47] were used. The surface areas of the sites are as follows: 1727 m² (I1, I2, I3 and I4), 1157 m² (I5, I6, I7 and I8), 7396 m² (I9, I10, I11 and I12), 1494 m² (I13, I14, I15 and I16). Sampling events were conducted at annual intervals over a two-year period to capture post-fire vegetation dynamics. PB was implemented on the following dates for each site: Aipos (14 April 2022), Resta (17 April 2022 and 5 December 2022) and Agios Stefanos (6 December 2022).

Also, the coding used is as follows:

REAFTPBINS2: Resta-After prescribed burning_Inside Site_2023;

REBPBCONS2: Resta-Before prescribed burning_Control Site_2022;

REAFTPBCONS2: Resta-After prescribed burning_Control Site_2022;

REBPBINS2: Resta-Before prescribed burning_Inside Site_2022;

AIAFTPBINS1: Aipos-After prescribed burning_Inside site_2023;

AIBPBCONS1: Aipos-Before prescribed burning_Control Site_2022;

AIAFTPBCONS1: Aipos-After prescribed burning_Control site_2023;

AGBPBINS3: Agios Stefanos-Before prescribed burning_Inside Site_2022;

AGAFPBINS3: Agios Stefanos-After prescribed burning_Inside Site_2023;

AIBPBINS1: Aipos-Before prescribed burning_Inside site_2022;

AGAFPBCONS3: Agios Stefanos-After prescribed burning_Control Site_2023;

AGBPBCONS3: Agios Stefanos-Before prescribed burning_Control Site_2022.

2.2.2. Soil Sample Processing

In December 2022 and April 2023, soil samples were collected from three areas of Chios, Resta, Agios Stefanos and Aipos, before and after the application of PB. Three samplings were carried out in the Resta area and one in the other two. Three replicates were collected in each sampling. to a depth of 20 cm after the dry needles and dry leaves were removed from the soil surface. The areas and sampling dates are shown in Table A17, Table A18, Table A19, Table A20 and Table A21 (Appendix B).

The soils in the Resta and Agios Stefanos areas are classified as sandy loam, while those of the Aipos area are clayey to clayey loam. The parent material in the Aipos area is hard limestone, while in the Resta area it is likely to be shale. Calcium carbonate was detectable, with a maximum value of 3.5%, in the Aipos area and that of Agios Stefanos with a maximum value of 0.3%. The forest surface in the Resta area was phrygana which are low xeric and mostly spiny shrubs (Table A17 and Table A18 in Appendix B) as well as phrygana with Calabrian pine (Pinus brutia) litter with many gaps (Table A19 in Appendix B). The Agios Stefanos area was covered by pine litter, while the Aipos area was also covered by pine litter with gaps from rocky outcrops. Sampling was repeated in late autumn 2023 after the burning that took place immediately after sampling.

The soil samples were air-dried and passed through a 2 mm sieve. Some of them were ground in a ball mill to determine the concentrations of organic carbon, nitrogen and calcium carbonate. The pH of these soil samples was measured electrometrically in a soil-water suspension of 1:2.5 (w/v) and the mechanical composition was estimated by the hydrometer method [48]. Conductivity was measured in a soil-water suspension of 1:5 (w/v) [49]. Organic carbon was determined by wet oxidation with potassium dichromate (K₂Cr₂O₇). Exchangeable cations Ca²⁺, Mg²⁺, Na⁺ and K⁺ were extracted with a 1 M ammonium acetate solution (NH₄C₂H₃O₂), pH 7 and their concentration was determined in an atomic absorption spectrophotometer. The concentration of organic + ammonium nitrogen (N) was determined by the Kjeldahl method. Free calcium carbonate (CaCO₃) was determined with a Bernard calcimeter. Ammonium and nitrate ions were extracted with 1 M KCl solution [50]. Ammonium concentrations were measured with a Kjeldahl apparatus and nitrate with a visible–ultraviolet spectrophotometer (at 210 nm). The concentrations of all soil parameters in Table A17 and Table A18 (Appendix B) are expressed on an air-dried soil basis.

2.2.3. Fireline Intensity (Ι)

F_L was recorded by following specific procedures [51,52,53,54,55,56,57,58,59] during PB on Chios Island, Greece. According to Gould et al. [60] (Table 1), the reliability of the methods and measurement techniques used to assess meteorological conditions describe forest fuels, and document fire rate of spread and behaviour was rated as 1. This rating was assigned because weather data were obtained from a nearby meteorological station and through direct field measurements, fuel characteristics were inferred using functions developed specifically for the fuel types, and fire spread was measured directly by the authors.

F_L was measured using the following steps: Observer’s positions were recorded using a GPS device to obtain the geographic coordinates. Regarding ground-based photography, images of sequential locations of the fire perimeter were captured using a Canon EOS 70D DSLR camera manufactured by Canon Inc. (Tokyo, Japan). The horizontal azimuth for each photograph was recorded with a compass. The time each photo was captured was retrieved from the metadata automatically embedded in the digital image files by the camera. F_L was then measured using basic geometric methods. Knowing the exact time of each F_L observation allowed matching it with the corresponding fine live and/or dead fuel moisture content, which had been measured separately. Fire behaviour recording also included aerial photographs captured using a DJI Phantom 4 Pro unmanned aerial vehicle (UAV) manufactured by DJI Technology Co., Ltd. (Shenzhen, China) [29]. It carries a 1″ CMOS, 20 Mp sensor, with FOV 84 8.8 mm/24 mm (35 mm format equivalent) f/2.8–f/11 auto focus at 1 m-lens and a mechanical/electronic shutter speed of 8–1/2000 s. Images were created in JPEG format of 5472 × 3648 pixels.

Ι was then calculated from F_L using the appropriate method, depending on fuel type, observed F_L, and whether the fire spread was heading or backing. Specifically, we used the following equations: (a) Fernandes et al. [61] for litter in Mediterranean pine forests, (b) Fernandes et al. [62] for shrublands, namely Cistus spp. and Sarcopoterium spinosum, (c) Clark [63] for heading fire spread in grasslands; and (d) Nelson and Adkins [64] for heading fire spread in Mediterranean pine forest litter. Also, we used linear regression to assess the relationship between the difference in Shannon diversity and Fireline Intensity (I) values (kW·m⁻¹).

2.2.4. Needle Water Potential

Predawn water potential (Ψleaf_pd) and pre-burn leaf water potential (Ψleaf_PB, measured near midday) were recorded for eight Pinus brutia trees at the Aipos site in spring 2022, 20 shrub and maquis species at the Resta site during winter 2022, 13 shrub and maquis species at the Resta site during spring 2022 and six Pinus brutia trees at the Agios Stefanos site during winter 2022. Measurements of Ψleaf_PB were taken between 11:00 and 14:00 using a portable pressure chamber (model PMS 1003, PMS Instruments, Corvallis, OR, USA). Ψleaf_pd served as an indicator of plant water stress, under the assumption of negligible night-time transpiration [65].

2.3. Statistical Analyses

The Kolmogorov–Smirnov and Shapiro–Wilk tests were used for the confirmation of the normal distribution of data. Plant diversity was assessed using the following biodiversity index [66,67]:

The Shannon diversity index (H): The index considers the number of species present in the sample and the relative number of individuals present for each species. It is used to quantify specific biodiversity. Values less than 1.5 are interpreted as sites with relatively low species diversity, while those greater than 2.0 are high. Mathematically, the Shannon index is calculated by the following expression:

H^{'} = - \sum_{i = 1}^{s} P_{i} \ln P_{i}

where

H^{'}

is the species diversity index, s is the number of species, and

P_{i}

is the proportion of individuals of each species belonging to the ith species of the total number of individuals.

For the statistical comparison of the soil parameters, due to the high variability of the parameters, all values were transformed to logarithms, with the exception of pH, for a better distribution of the values (in relation to a normal distribution). The statistical comparison for each experimental surface was made with the analysis of variance (ANOVA). The comparison of the means was carried out with the Tukey test.

3. Results

3.1. Plant Composition and Diversity

In the studied area, 69 plant species belonging to 30 families were identified. The most numerous families were Fabaceae (16%), Asteraceae (101%), and Poaceae (8%) (Figure 4). The treatments with the greatest number of plant species were REAFTPBINS2 (38 species), REAFPBINS4 (31), REBPBINS2 (27), and REBPBCONS2 (26), while the treatment with the fewest plant species was AIAFTPBINS1 (8). Appendix A presents the plant species recorded at each site.

The Shannon diversity index was significantly different among treatments. Therandomization test indicated that the difference between sampling sites was statistically significant (p < 0.05). The highest diversity was reported in the treatment REAFTPBINS2 (2.14d) followed by REBPBCONS2 (1.97d), whereas intermediate values were observed for REAFTPBCONS2 and REBPBINS2 (1.78c and 1.61c, respectively) (Table 2).

3.2. Soil Parameters

Table A17, Table A18, Table A19, Table A20 and Table A21 (Appendix B) present the results of the soil analyses along with the statistical comparison of the parameters after and before the application of the PB. A characteristic feature is the variability of the chemical properties of the soils which is shown by the high values of the coefficient of variation in the tables. The elements most affected by the PB implementation were organic carbon and nitrogen. Regarding carbon, statistically significant differences (decrease in concentration after burning) were observed in Table A17 (Resta) and Table A20 (Agios Stefanos). In the area of Resta (Table A17) the C/N ratio also increased statistically significantly, which contributes to soil fertility. Total, organic and available nitrogen in the area of Agios s Stefanos (Table A20) followed organic carbon, i.e., it decreased significantly after burning. It should be noted in general that the percentage (%) of available N in relation to total N is very small (close to unity), but its importance is great given that it is the only form of N that plants can take up. A follow-up prescribed burn in the Agios Stefanos area should be conducted after a minimum of three years to assess whether available nitrogen levels return to pre-burn levels. Total and organic nitrogen in the Aipos area (Table A21) increased after burning. This finding is probably due to the variability of sampling. In Table A18 and Table A21 it appears that the concentrations of exchangeable Ca increased significantly. The same applies to Mg in the Aipos area (Table A21). It is known that burning increases the concentrations of exchangeable cations in the soil. However, the same did not happen with exchangeable K and Na in Table A20. Also, in all cases, the conductivity of the soil solution did not differ significantly.

The area of Resta and Agios Stefanos did not have any CaCO₃ concentration. The Aipos had low concentrations of CaCO₃ which ranged 0.79–1.64%.

3.3. Fire Behaviour and Plant Diversity

F_L ranged from 0.5 to 1.8 m and I varied from 84 to 2695 kW·m⁻¹, respectively. Measured F_L, calculated I, and Shannon index values, are presented in Table 3.

We used linear regression to assess the relationship between the difference in Shannon diversity and I (Figure 5). The analysis revealed no statistically significant relationship (p = 0.856) and a poor model fit (adjusted R² = −0.069), indicating that I does not linearly explain variation in Shannon diversity. This is consistent with the small unstandardized coefficient of I (0.00002921), suggesting a negligible effect size.

3.4. Needle Water Potential

Ψleaf measurements across four Mediterranean sites, Aipos, Resta (Winter and Spring), and Agios Stefanos, show clear differences between Ψleaf_pd and Ψleaf_PB values. At all sites, Ψleaf_pd values were consistently higher (less negative), indicating better plant hydration during early morning. For example, at Aipos, the mean Ψleaf_pd was −1.00 MPa, which decreased to −1.94 MPa before the PB. Similarly, at Resta Winter, Ψleaf_pd averaged −1.54 MPa, dropping to −2.02 MPa pre-burn. Agios Stefanos showed a mean Ψleaf_pd of −1.45 MPa, which decreased substantially to −2.32 MPa before burning. At Resta Spring, however, the mean Ψleaf remained relatively stable between predawn and pre-burn measurements, around −1.11 MPa (Figure 6).

Regarding the range of mean Ψleaf_pd across the four sites, they spanned from −1.00 to −1.54 MPa. Specifically, the sites Resta Winter and Agios Stefanos exhibited the lowest mean Ψleaf_pd at −1.54 and −1.45 MPa, respectively, reflecting the most negative (i.e., highest water stress) predawn leaf water potential among the locations measured. Resta Spring had intermediate values of −1.11 MPa, while Aipos recorded the highest mean Ψleaf_pd at −1.00, indicating comparatively better soil moisture conditions.

4. Discussion

4.1. Plant Composition and Diversity

The plant species of Mediterranean ecosystems, having been subjected to the action of fire for thousands of years, have developed mechanisms that ensure their survival as well as rapid regeneration and recovery [68]. The main mechanism is the vegetative regeneration (Resprouting) of burned individuals and the establishment of new individuals through the process of seed germination [69].

In the present study, it was observed that the most numerous families were Asteraceae, Poaceae and Fabaceae, a fact that reflects the prevailing situation in the Greek area, as these families are among the three most numerous families in Greece and the Mediterranean. The plant species belonging to the Asteraceae, Poaceae and Fabaceae families, in their majority, occur in ecosystems such as the research area and include plants with high ecological value [34,70,71].

Our results namely the dominance of Asteraceae, Fabaceae, Poaceae and the post-burn increase in α-diversity fit well within established Mediterranean post-fire patterns. At the community level, early post-fire assemblages in Mediterranean shrublands and open woodlands typically show a short-term surge in species richness and evenness driven by a pulse of annual forbs and graminoids together with the persistence of resprouting shrubs. This “early peak” has been documented across vegetation types and moisture settings in the Basin (e.g., maquis, garrigue/phrygana, and pine stands understoreys) and is especially evident after low to moderate intensity wildfires or prescribed burns that leave belowground organs and patches of live vegetation intact [72,73,74].

The family-level signal we observe is also expected for early post-fire stages in the eastern Mediterranean: Asteraceae and Poaceae contribute to many fast-cycling annuals, while Fabaceae are disproportionately represented among obligate seeders with physically dormant seeds. Heat pulses from fire and, in some taxa, smoke-derived compounds are well-known cues that break dormancy and synchronize emergence in Cistaceae and Fabaceae, thereby boosting short-term richness and altering composition [75,76,77]. Importantly, upper heat thresholds for breaking physical dormancy match fire-related temperatures, whereas lower thresholds are shaped by background summer temperatures together releasing Fabaceae-Cistaceae seed dormancy and synchronizing emergence after burns [75,76,77].

Plant diversity before the implementation of the PΒ was observed at satisfactory levels. The diversity of the topography of Chios, the altitudinal gradient from sea level to the highest peak, the variety of climatic conditions likely created a multitude of different habitats (stations), which support the above plant diversity. The geological substrate with the different types of soils creates another important parameter for plants. Specifically, the different rocks of Chios likely create various types of soils which affect the chemical composition, cohesion, pH and nutrients of the substrate, on which the plant species grow. Also, the existing neighbouring vegetation as well as the paleogeography, the colonization of the area by humans and the phylogeny that developed in the area over time are closely related to the significant number and diversity of plant species recorded in the research areas before the implementation of the PΒ.

From the analysis of the data, it emerged that the PΒ has a significant effect on the plant diversity (number of plant species, Shannon–Wiener and Simpson index) of the burned forest formations of Chios. This conclusion stems from the differentiation that the burned areas present compared to the unburned areas. In particular, high plant diversity values were observed after the implementation of the PΒ compared to those recorded before the implementation of the PΒ.

The increased diversity in the burned areas could be explained in various ways, such as, for example, by the entry of some precursor species, which disappear in the following period under conditions of competition. Furthermore, the increased plant diversity could be attributed to the many species of the Fabaceae family found in the samples, which show high abundance and coverage during the first post-fire years, as their germination is favoured by the action of fire [34]. A large part of the plant species of the Fabaceae family are therophytes, mainly annual herbs whose regeneration occurs by seed germination [78]. Also, another possible explanation of this result could be attributed to the fact that plants that die off from fire and regenerate by seed germination depend on this germination mechanism in order to exist in the specific area. For these plants, young shoots mature and produce seeds that feed the seed bank, thus ensuring the recovery of the plant species population [79].

From a functional perspective, our floristic shift reflects the coexistence of resprouting and seeding strategies under a mild fire regime. Low-intensity PB reduces above-ground competition and litter while preserving many resprouter rootstocks, creating establishment windows for obligate seeders; this mixture tends to elevate α-diversity and, at fine scales, β-diversity as well [80,81]. Trait syntheses for Mediterranean floras (BROT 2.0) show that the very species pools dominating our plots carry fire-linked traits (resprouting organs, serotiny in conifers where present, heat/smoke-cued germination), providing a mechanistic basis for the compositional patterns we report [82].

Patchiness also matters. Prescribed burns commonly generate a fine-grained mosaic of lightly charred, unburned, and more strongly heated microsites. Such pyrodiversity promotes niche complementarity resprouters reoccupy lightly affected patches while obligate seeders capitalize on hotter, more open microsites thereby maintaining higher local diversity in the short term [74,81]. In this context, our within-site heterogeneity in life forms and families is consistent with the notion that diversity benefits from a mixed-severity, patchy fire imprint.

In our sites, several species illustrate the typical Mediterranean fire-response spectrum. After a fire, the dwarf shrub Sarcopoterium spinosum grows quickly and can even grow from seed [83]. Smoke compounds can also help seeds germinate [84]. The obligate-seeding shrubs Cistus creticus and the Lavandula stoechas exhibit fire-induced germination through heat and/or smoke, and they also respond to post-fire light and temperature conditions [74,82,83,84,85,86]. Brachypodium retusum, a rhizomatous grass, usually grows back quickly after a fire, and fire can help it reproduce sexually in Mediterranean grasslands [87,88]. Annual legumes (Trifolium campestre, T. scabrum, T. stellatum) preserve physically latent, soil-stored seed banks and frequently germinate following disturbances such as fire [89,90]. The prickly legume Calicotome villosa establishes a lasting seed bank that facilitates post-fire recruitment and is also known to resprout, so integrating seeder and resprouter tactics [91]. Conversely, Pinus brutia is a non-resprouting obligate seeder that regenerates post-fire from canopy and soil seed storage [92]. Within the CSR framework [93,94], resprouting shrubs and perennial grasses in our plots tend to be CS-leaning, whereas obligate-seeding shrubs and annuals are more R-oriented; consequently, low-intensity burns at our sites were followed by short-term increases in annuals and other R-strategists, while CS-types recovered via resprouting consistent with the higher diversity observed in REAFTPBINS2 (H = 2.14) compared with unburned controls (Table 2). According to the research of Kazanis and Arianoutsou [95], the evolution of vegetation after fire follows the model of “auto-succession”, where the community that has burned, no matter how different it may seem from the unburned one, maintains its floristic identity. Thus, the geophytes, which pre-existed in the area and survived, benefit from the post-fire conditions of abundant nutrients, abundant sunlight and moisture, but also from the absence of competitors.

In addition to the application of PB, the systematic recording of environmental parameters and other factors (e.g., grazing) would enhance our understanding of how these variables interact with fire to influence biodiversity in the study areas.

Data from Mediterranean forests and grasslands indicate that diversification responses vary depending on post-fire management practices. A five-year study in southern Italy revealed that PB and mowing reduced the prevalence of tall perennial grasses due to abandonment, significantly improving plant diversity compared to unmanaged controls, which indicated a post-burn composition marked by an increase in short-lived forbs and legumes [96]. The initial regeneration of vegetation in Mediterranean forests after a fire was similarly affected by management approaches, showing increased species richness immediately post-fire before progressively returning to pre-fire composition [73]. Greek example studies confirm this timing pattern: in the Pinus halepensis forests of Attica, herbaceous plant species dominate during the first four years after a wildfire, with plant diversity peaking in the second year. Thereafter, their abundance declines as woody species gradually become more dominant [97,98]. Similarly, in Northern Achaia (Peloponnese), the first 1–2 years after wildfire were dominated by annual herbaceous species, primarily from the Leguminosae (Fabaceae) and Compositae (Asteraceae) families, whereas mature stands were characterized by a dense woody understory [99]. Ultimately, our observed species composition and functional strategies align with long-term successional patterns described in the literature. When fire-free intervals are prolonged or management practices promote the accumulation of dense litter and tall grasses, plant diversity may decline due to competitive exclusion. In contrast, regular low-intensity wildfires or targeted interventions can maintain a functional balance between resprouters and seeders, thereby supporting greater understory diversity [74,96]. These similarities reinforce the broader applicability of our findings and highlight a specific ecological mechanism linking the observed compositional shifts to well-established Mediterranean fire-response strategies.

4.2. Soil Parameters

The application of PB in the sites under study of Chios (Resta, Agios Stefanos, Aipos) revealed differentiated effects on the basic physicochemical parameters of the soil. The results demonstrate that organic matter and nitrogen are the most sensitive elements to fire, as has been documented in previous studies [95].

In the Resta area, a statistically significant decrease in organic carbon was observed after burning, which is attributed to the reduction in combustible material. At the same time, an increase in the C/N ratio is considered favourable for soil fertility, as it can enhance the long-term stability of organic matter [100]. On the contrary, in the Agios Stefanos area, burning led to a significant decrease in both organic carbon and available nitrogen. This finding is particularly important, as available nitrogen is the form readily available to plants and its reduction may have consequences for vegetation [50]. According to international literature, it takes approximately three to four years for available nitrogen levels to recover after burning [95], which confirms the need for long-term monitoring.

In the Aipos area, unlike the previous two ecosystems, an increase in total and organic nitrogen was recorded, probably due to spatial heterogeneity in sampling. At the same time, the concentrations of exchangeable Ca and Mg increased significantly after burning, a finding that is consistent with the observation that ash enriches the soil with base cations. The concentration of exchangeable Ca²⁺ also increased significantly in the Resta area which was covered by phrygana. Although exchangeable cations such as Ca²⁺, Mg²⁺, K⁺ have been reported in numerous studies to increase after forest fires [101,102], there can be variability. The existence of such variability was stressed by Arocena and Orio [103]. According to these authors, the main cause is the intensity of flame temperature. However, no statistically significant changes in electrical conductivity were observed, indicating that salt availability was not strongly affected by fire. The surface ash can cause problems in the selection of soil samples. When there are strong winds with different directions, the deposition and settlement of ash can be affected. This variability can be reduced by selecting similar topography for soil collection before and after the application of prescribed burning.

Overall, the results suggest that PB did not produce significant changes in most basic soil properties, at least in the short term. However, the variations recorded in carbon and nitrogen highlight the importance of burning as a management tool that can have both positive and negative impacts, depending on the ecosystem and the time frame. The continuation of experiments on a longer time scale is considered necessary to determine the long-term effects of this practice [49].

4.3. Fire Behaviour and Plant Diversity

The relationship between the plant diversity after the implementation of the PB method and the I during the prescribed burns is not linear (Figure 5). Since higher Shannon diversity values indicate more diverse and evenly distributed plant communities, a nonlinear pattern may better describe the relationship, where low-intensity wildfires promote diversity by reducing dominant species, while high-intensity wildfires reduce diversity by eliminating sensitive species [104]. The above-mentioned hypothesis aligns with the findings of Richter et al. [105] who reported that plant diversity peaks at intermediate wildfire severities, rather than under low or high severity conditions. It also supports the conclusions of Abedi et al. [106] who found that fire regimes, including I, significantly influence taxonomic diversity and that these effects can be mediated by landscape factors such as slope and aspect.

Future research may employ polynomial regression to capture potential nonlinear patterns and reveal ecological thresholds, bandwidths (e.g., peak diversity at intermediate fire intensity), or tipping points (e.g., a collapse in diversity beyond a certain intensity level).

4.4. Needle Water Potential

Measurements at the Resta Winter and Agios Stefanos sites showed the most negative Ψleaf_pd, both recorded during the winter period. This suggests that plants were still experiencing moderate water stress at that time, in contrast to the spring measurements from Aipos and Resta Spring, which indicated comparatively better soil moisture conditions. Such seasonal differences are consistent with precipitation patterns: between September 2021 and April 2022, when measurements at Aipos and Resta Spring were taken, cumulative rainfall was approximately 340 mm, whereas from May to December 2022, preceding the winter measurements, total rainfall was less than half that amount (around 150 mm) In both seasons, however, the vapour pressure deficit (VPD) remained very low (<0.3 kPa), suggesting minimal transpiration. Changes in plant water potential occur seasonally, in response to soil moisture (rainfall) and atmospheric demand (VPD). Several studies (e.g., [107,108,109]) have shown that following early autumn or spring rains, trees typically recover from drought stress. Similarly, in our study, spring rainfall led to higher (less negative) Ψleafpd, values, whereas during the drier winter period, slightly more negative Ψleafpd, values were recorded.

5. Conclusions

This study highlights the ecological effects of PB in Mediterranean vegetation on Chios island, Greece. The results showed that PB treatment influenced plant diversity, soil properties and plant water potential in ways that may support both ecosystem resilience and fire management measures. Overall, PB tended to increase plant diversity, indicating that fire promotes the regeneration and recruitment of post-fire specialist species. This finding supports the idea that PB can be an effective tool for maintaining biodiversity.

Soil analyses yielded disparate site responses, with organic carbon and nitrogen being the most sensitive to fire. While some cases showed a decrease in available nitrogen, the rise in exchangeable base cations (such as calcium and magnesium) suggests that burning can also temporarily enrich the soil. The differences between sites underscore the importance of local monitoring and long-term studies to determine if these changes are sustained.

Leaf water potential measurements were in line with the seasonal difference in plant water status, with higher stress conditions in winter compared to spring. This implies that prescribed burning interacts with weather conditions; thus, the seasonality should be taken into account when planning fire use.

These results demonstrate that well-planned PB can help mitigate fire danger while supporting biodiversity conservation and ecosystem functioning in Mediterranean ecosystems. Nevertheless, further long-term monitoring is needed to fully understand the cumulative fire effects and to establish suitable guidelines for sustainable fire regimes in Greece.

Author Contributions

Conceptualization, A.D.S., M.A., E.K. and P.M.; methodology, A.D.S., M.A., E.K. and P.M.; software, A.D.S., M.A. and E.K.; validation, A.D.S., M.A., E.K., P.M. and G.K.; formal analysis, A.D.S., M.A. and E.K.; investigation, A.D.S., M.A., E.K., P.M. and G.K.; resources, A.D.S., M.A. and E.K.; data curation, A.D.S., M.A. and E.K.; writing—original draft preparation, A.D.S., M.A., E.K. and P.M.; writing—review and editing, A.D.S. and M.A.; visualization, A.D.S. and M.A.; supervision, A.D.S. and M.A.; project administration, M.A.; funding acquisition, M.A. All authors have read and agreed to the published version of the manuscript.

Funding

This project was funded by WWF Greece through a private sponsorship from Procter & Gamble Corporation.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

We thank the Municipality of Chios for providing water trucks and personnel during the burns. We also thank Georgios Rodakis and Nikolaos Vagianos, volunteer firefighters of Chios Voluntary Action Team—OMIKRON, for their valuable support during soil samplings. We thank all IMFE personnel for their support in the field and laboratory work.

Conflicts of Interest

The authors declare no conflicts of interest. This research was funded by Procter and Gamble, and all potential conflicts have been disclosed and managed according to standard ethical practices.

Appendix A

Table A1. Vascular plant species at the AGAFPBCONS3 site.

Plant Species	Family
Aetheorhiza bulbosa	Asparagaceae
Anthyllis hermanniae	Fabaceae
Asparagus acutifolius	Fabaceae
Brachypodium retusum	Lamiaceae
Briza media	Poaceae
Galium aparine	Rubiaceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Oxalis pes-caprae	Oxalidaceae

Table A2. Vascular plant species at the AGAFPBINS3 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Anthyllis hermanniae	Fabaceae
Asparagus acutifolius	Asparagaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Himantoglossum robertianum	Orchidaceae
Lavandula stoechas	Lamiaceae
Urospermum picroides	Asteraceae

Table A3. Vascular plant species at the AGBPBCONS3 site.

Plant Species	Family
Aetheorhiza bulbosa	Asparagaceae
Anthyllis hermanniae	Fabaceae
Asparagus acutifolius	Fabaceae
Brachypodium retusum	Lamiaceae
Briza media	Poaceae
Galium aparine	Rubiaceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Oxalis pes-caprae	Oxalidaceae

Table A4. Vascular plant species at the AGBPBINS3 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Anthyllis hermanniae	Fabaceae
Asparagus acutifolius	Asparagaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Himantoglossum robertianum	Orchidaceae
Lavandula stoechas	Lamiaceae
Urospermum picroides	Asteraceae

Table A5. Vascular plant species at the AIAFTPBCONS1 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Brachypodium retusum	Poaceae
Galium murale	Rubiaceae
Geranium robertianum	Geraniaceae
Lamium amplexicaule	Lamiaceae
Muscari neglectum	Hyacinthaceae
Silene sedoides	Caryophyllaceae
Taraxacum officinale	Asteraceae
Theligonum cynocrambe	Rubiaceae

Table A6. Vascular plant species at the AIAFTPBINS1 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Brachypodium retusum	Poaceae
Drimia maritima	Hyacinthaceae
Geranium robertianum	Geraniaceae
Lamium amplexicaule	Lamiaceae
Muscari comosum	Hyacinthaceae
Muscari neglectum	Hyacinthaceae
Theligonum cynocrambe	Rubiaceae

Table A7. Vascular plant species at the AIBPBCONS1site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Allium nigrum	Alliaceae
Anemone coronaria	Ranunculaceae
Brachypodium retusum	Poaceae
Cynodon dactylon	Poaceae
Galium murale	Rubiaceae
Muscari neglectum	Hyacinthaceae
Ranunculus paludosus	Ranunculaceae
Urospermum picroides	Asteraceae

Table A8. Vascular plant species at the AIBPBINS1 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Brachypodium retusum	Poaceae
Euphorbia peplus	Euphorbiaceae
Galium murale	Rubiaceae
Geranium robertianum	Geraniaceae
Lamium amplexicaule	Lamiaceae
Muscari neglectum	Hyacinthaceae
Sherardia arvensis	Rubiaceae
Theligonum cynocrambe	Rubiaceae
Urospermum picroides	Asteraceae

Table A9. Vascular plant species at the REAFPBCONS4 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Asparagus acutifolius	Asparagaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Erica manipuliflora	Ericaceae
Fumana arabica	Cistaceae
Galium divaricatum	Rubiaceae
Hypochaeris achyrophorus	Asteraceae
Leontodon tuberosus	Asteraceae
Pinus brutia	Pinaceae
Psoralea bituminosa	Cistaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae

Table A10. Vascular plant species at the REAFPBINS4 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium distachyon	Poaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Calicotome villosa	Fabaceae
Cistus creticus	Cistaceae
Fumana arabica	Cistaceae
Gagea graeca	Liliaceae
Hypochaeris achyrophorus	Asteraceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Ornithopus compressus	Fabaceae
Phagnalon rupestre	Asteraceae
Pinus brutia	Pinaceae
Plantago bellardii	Plantaginaceae
Ranunculus paludosus	Ranunculaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Sherardia arvensis	Rubiaceae
Teucrium capitatum	Lamiaceae
Tordylium apulum	Apiaceae
Trifolium campestre	Fabaceae
Trifolium lappaceum	Fabaceae
Trifolium scabrum	Fabaceae
Trifolium stellatum	Fabaceae
Tuberaria guttata	Cistaceae
Vicia pubescens	Fabaceae

Table A11. Vascular plant species at the REAFTPBCONS2 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Asparagus acutifolius	Asparagaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Erica manipuliflora	Ericaceae
Fumana arabica	Cistaceae
Galium divaricatum	Rubiaceae
Hypochaeris achyrophorus	Asteraceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Osyris alba L.	Sasntalaceae
Pinus brutia	Pinaceae
Psoralea bituminosa	Cistaceae
Pyrus spinosa	Rosaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae

Table A12. Vascular plant species at the REAFTPBINS2 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium distachyon	Poaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Bromus rubens	Poaceae
Calicotome villosa	Fabaceae
Cistus creticus	Cistaceae
Euphorbia peplus	Euphorbiaceae
Fumana arabica	Cistaceae
Gagea graeca	Liliaceae
Galium divaricatum	Rubiaceae
Hypochaeris achyrophorus	Asteraceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Linaria pelisseriana	Veronicaceae
Ornithopus compressus	Fabaceae
Phagnalon rupestre	Asteraceae
Pinus brutia	Pinaceae
Plantago bellardii	Plantaginaceae
Plantago lagopus	Plantaginaceae
Ranunculus paludosus	Ranunculaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Sherardia arvensis	Rubiaceae
Teucrium capitatum	Lamiaceae
Tolpis barbata	Asteraceae
Tordylium apulum	Apiaceae
Torilis nodosa	Apiaceae
Trifolium campestre	Fabaceae
Trifolium lappaceum	Fabaceae
Trifolium scabrum	Fabaceae
Trifolium stellatum	Fabaceae
Tuberaria guttata	Cistaceae
Vicia pubescens	Fabaceae

Table A13. Vascular plant species at the REBPBCONS2 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Anthyllis hermanniae	Fabaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Bromus rubens	Poaceae
Cistus parviflorus	Cistaceae
Euphorbia peplus	Euphorbiaceae
Fumana arabica	Cistaceae
Galium murale	Rubiaceae
Helianthemum apenninum	Cistaceae
Hypochaeris achyrophorus	Asteraceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Linum strictum	Linaceae
Osyris alba	Santalaceae
Phagnalon rupestre	Asteraceae
Pinus brutia	Pinaceae
Ranunculus paludosus	Ranunculaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Sherardia arvensis	Rubiaceae
Trifolium campestre	Fabaceae

Table A14. Vascular plant species at the REBPBCONS4 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Aira elegans	Poaceae
Anagallis arvensis	Primulaceae
Anthyllis hermanniae	Fabaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Bromus rubens	Poaceae
Cistus parviflorus	Cistaceae
Euphorbia peplus	Euphorbiaceae
Fumana arabica	Cistaceae
Galium murale	Rubiaceae
Hypochaeris achyrophorus	Asteraceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Osyris alba	Santalaceae
Phagnalon rupestre	Asteraceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Sherardia arvensis	Rubiaceae
Trifolium campestre	Fabaceae

Table A15. Vascular plant species at the REBPBINS2 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Anagallis arvensis	Primulaceae
Anthyllis hermanniae	Fabaceae
Anthyllis vulneraria	Fabaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium distachyon	Poaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Calicotome villosa	Fabaceae
Cistus parviflorus	Cistaceae
Dorycnium hirsutum	Fabaceae
Euphorbia peplus	Euphorbiaceae
Fumana arabica	Cistaceae
Gagea graeca	Liliaceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Ophrys lutea	Orchidaceae
Phagnalon rupestre	Asteraceae
Pinus brutia	Pinaceae
Plantago lagopus	Plantaginaceae
Ranunculus paludosus	Ranunculaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Sherardia arvensis	Rubiaceae
Trifolium angustifolium	Fabaceae
Trifolium campestre	Fabaceae

Table A16. Vascular plant species at the REBPBINS4 site.

Plant Species	Family
Aetheorhiza bulbosa	Asteraceae
Anthyllis vulneraria	Fabaceae
Asterolinon linum-stellatum	Primulaceae
Brachypodium retusum	Poaceae
Briza media	Poaceae
Calicotome villosa	Fabaceae
Cistus parviflorus	Cistaceae
Dorycnium hirsutum	Fabaceae
Fumana arabica	Cistaceae
Gagea graeca	Liliaceae
Lavandula stoechas	Lamiaceae
Leontodon tuberosus	Asteraceae
Phagnalon rupestre	Asteraceae
Pinus brutia	Pinaceae
Sarcopoterium spinosum	Rosaceae
Selaginella denticulata	Selaginellaceae
Serapias bergonii	Orchidaceae
Trifolium angustifolium	Fabaceae
Trifolium campestre	Fabaceae

Appendix B

Table A17. Soil properties of the Resta area after (8 April 2023) and before (13 April 2022) the use of prescribed burning (PB). Organic carbon (Org. C) and clay are expressed in percentages (%), total and organic nitrogen are expressed in g/kg, ammonium (Am. N) and nitrate nitrogen (Nit. N) in mg/kg. Conductivity (Cond.) is expressed in μS/cm and exchangeable Ca, Mg, K and Na in meq/100 g of soil. Variability was calculated in percentages (%) of the standard deviation of the mean. Different letters in the same column mean a statistical difference for at least the 0.05 probability level. Absence of letters means non-statistical significance.

	pH	Org. C	Tot. N	Org. Ν	Am. Ν	Νit. Ν	C/N	Cond.	Clay	Ca	Mg	K	Na
After
Average	7.5	1.27 a	2.06	2.05	5.92	10.5	6.2 a	443	14.4	9.42	1.44	0.38	0.10
Variability	(6)	(24)	(24)	(12)	(42)	(60)	(24)	(25)	(8)	(35)	(14)	(12)	(7)
Before
Average	8.0	3.31 b	1.75	1.72	6.99	21.7	20 b	529	12.1	11.4	1.31	(0.26)	0.10
Variability	(3)	(20)	(19)	(10)	(10)	(47)	(35)	(50)	(21)	(57)	(13)	(38)	(18)

Table A18. Soil properties of the Resta area (with Phrygana) after (8 April 2023) and before (5 December 2022) the use of PB. Organic carbon (Org. C) and clay are expressed in percentages (%), total and organic nitrogen are expressed in g/kg, ammonium (Am. N) and nitrate nitrogen (Nit. N) in mg/kg. Conductivity (Cond.) is expressed in μS/cm and exchangeable Ca, Mg, K and Na in meq/100 g of soil. Variability was calculated in percentages (%) of the standard deviation of the mean. Different letters in the same column mean a statistical difference for at least the 0.05 probability level. Absence of letters means non-statistical significance.

	pH	Org.C	Tot. N	Org. Ν	Am. Ν	Νit. Ν	C/N	Cond.	Clay	Ca	Mg	K	Na
After
Average	7.32 a	1.95	1.60	1.58	4.42	9.07	11	452	15.1	8.40 a	1.72	0.32	0.10
Variability	(5)	(50)	(20)	(20)	(40)	(52)	(30)	(37)	(0)	(29)	(31)	(12)	(28)
Before
Average	6.45 b	1.19	8.87	8.64	14.2	8.87	22	368	12.7	4.51 b	1.67	0.39	0.18
Variability	(4)	(32)	(58)	(59)	(65)	(28)	(103)	(11)	(15)	(17)	(11)	(11)	(46)

Table A19. Soil properties of the Resta area (with Trachea) after (8 April 2023) and before (7 December 2022) the use of PB. Organic carbon (Org. C) and clay are expressed in percentages (%), total and organic nitrogen are expressed in g/kg, ammonium (Am. N) and nitrate nitrogen (Nit. N) in mg/kg. Conductivity (Cond.) is expressed in μS/cm and exchangeable Ca, Mg, K and Na in meq/100 g of soil. Variability was calculated in percentages (%) of the standard deviation of the mean. Absence of letters means non-statistical significance.

	pH	Org.C	Tot. N	Org. Ν	Am. Ν	Νit. Ν	C/N	Cond.	Clay	Ca	Mg	K	Na
After
Average	7.16	2.87	2.16	2.14	1.97	9.03	14	422	14.4	7.62	1.75	0.36	0.14
Variability	(4)	(4)	(28)	(28)	(30)	(59)	(27)	(14)	(29)	(32)	(30)	(13)	26
Before
Average	7.19	2.80	1.97	1.96	2.80	11.0	(12)	456	13.1	6.50	1.75	0.36	0.17
Variability	(5)	(13)	(30)	(35)	(10)	(21)	(32)	(11)	(24)	(24)	(14)	(22)	(18)

Table A20. Soil properties of the Agios Stefanos area after (8 April 2024) and before (6 December 2023) the use of PB. Organic carbon (Org. C) and clay are expressed in percentages (%), total and organic nitrogen are expressed in g/kg, ammonium (Am. N) and nitrate nitrogen (Nit. N) in mg/kg. Conductivity (Cond.) is expressed in μS/cm and exchangeable Ca, Mg, K and Na in meq/100 g of soil. Variability was calculated in percentages (%) of the standard deviation of the mean. Different letters in the same column mean a statistical difference for at least the 0.05 probability level. Absence of letters means non-statistical significance.

	pH	Org.C	Tot. N	Org. Ν	Am. Ν	Νit. Ν	C/N	Cond.	Clay	Ca	Mg	K	Na
After
Average	7.54	1.20 a	1.23 a	1.22 a	3.76 a	11.9 a	11 a	625	13.1	13.5	1.14	0.27 a	0.21 a
Variability	(6)	(58)	(18)	(18)	(62)	(10)	(25)	(11)	(0)	(33)	(60)	(19)	(86)
Before
Average	7.32	6.0 b	2.78 b	2.73 b	15.1 b	27.9 b	22 b	785	10.1	17.0	2.38	0.44 b	0.35 b
Variability	(3)	(43)	(31)	(31)	(56)	(16)	(56)	(18)	(11)	(9)	(33)	(22)	(4)

Table A21. Soil properties of the Aipou area after (8 April 2023) and before (13 December 2022) the use of PB. Organic carbon (Org. C) and clay are expressed in percentages (%), total and organic nitrogen are expressed in g/kg, ammonium (Am. N) and nitrate nitrogen (Nit. N) in mg/kg. Conductivity (Cond.) is expressed in μS/cm and exchangeable Ca, Mg, K and Na in meq/100 g of soil. Variability was calculated in percentages (%) of the standard deviation of the mean. Different letters in the same column mean statistical difference for at least the 0.05 probability level. Absence of letters means non-statistical significance.

	pH	Org.C	Tot. N	Org. Ν	Am. Ν	Νit. Ν	C/N	Cond.	Clay	Ca	Mg	K	Na
After
Average	7.66	7.00	3.87 a	3.84 a	5.72	22.2	18	1076	31.1	34.0 a	4.30 a	1.25	0.29
Variability	(4)	(43)	(28)	(27)	(82)	(67)	(22)	(27)	(34)	(20)	(4)	(11)	(27)
Before
Average	7.53	4.65	1.76 b	1.74 b	10.2	10.3	26	705	43.1	23.0 b	3.04 b	1.83	0.34
Variability	(4)	(41)	(22)	(22)	(20)	(34)	(29)	(28)	(20)	(13)	(6)	(44)	(12)

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Figure 1. The study area on the island of Chios, Greece, was projected using the Greek Grid system (EGSA87). The red point and red square in the two locator maps indicate the location and extent of the study area. The map was created using ArcGIS version 9.3 geographic information system software developed by ESRI.

Figure 2. The plant biodiversity sampling points (each one the centre of the 1 square metre plot). I: inside the prescribed burned area, C: control, outside the prescribed burned area). The map was created using ArcGIS version 9.3 geographic information system software developed by ESRI.

Figure 3. Sampling of plant biodiversity in the experimental plots of the research area (photos by Dr. Alexandra Solomou and Elias Tziritis 2022).

Figure 4. Percentage distribution of plant species across plant families.

Figure 5. Linear regression between Shannon difference and Fireline Intensity (I) values (kW·m⁻¹).

Figure 6. Predawn and pre-burn Ψleaf measurements across four Mediterranean sites, Aipos, Resta (Winter and Spring), and Agios Stefanos on Chios Island.

Table 1. Reliability rating for weather, fuel and fire spread observations for wildfires in open eucalypt forests.

Rating	Weather	Fuel	Rate of Spread
1	Nearby meteorological station or direct measurements in the field	Fuel characteristics inferred from a fuel age function developed for the particular fuel type	Direct timing of fire spread measurements by the authors
2	Meteorological station within 50 km of the fire	Fuel characteristics inferred from a visual assessment of nearby unburnt forest	Reliable timing of fire spread by a third party
3	Meteorological station > 50 km of the fire, reconstruction of wind speed for fire site	Fuel characteristics inferred from a fuel age curve for a forest type of similar structure	Reconstruction of fire spread with numerous cross references
4	Spot meteorological observation near the fire	Fuel characteristics typical of equilibrium level in a dry sclerophyll forest	Doubtful reconstruction of fire spread
5	Distant meteorological observations at locations very different to fire site		Anecdotal or conflicting reports of fire spread

Table 2. Plant diversity index in sites.

Treatments	Mean Shannon–Wiener (H)
REAFTPBINS2 **	2.14 d
REBPBCONS2	1.97 d
REAFTPBCONS2	1.78 c
REBPBINS2	1.61 c
AIAFTPBINS1	1.53 b
AIBPBCONS1	1.30 a *
AIAFTPBCONS1	1.21 a
AGBPBINS3	1.18 a
AGAFPBINS3	1.15 a
AIBPBINS1	1.08 a
AGAFPBCONS3	1.08 a
AGBPBCONS3	1.05 a

* For all sites with the same letter, the difference between the means is not statistically significant. ** REAFTPBINS2: Resta-After prescribed burning_Inside Site_2023. REBPBCONS2: Resta-Before prescribed burning_Control Site_2022. REAFTPBCONS2: Resta-After prescribed burning_Control Site_2022. REBPBINS2: Resta-Before prescribed burning_Inside Site_2022. AIAFTPBINS1: Aipos-After prescribed burning_Inside site_2023. AIBPBCONS1: Aipos-Before prescribed burning_Control Site_2022. AIAFTPBCONS1: Aipos-After prescribed burning_Control site_2023. AGBPBINS3: Agios Stefanos-Before prescribed burning_Inside Site_2022. AGAFPBINS3: Agios Stefanos-After prescribed burning_Inside Site_2023. AIBPBINS1: Aipos-Before prescribed burning_Inside site_2022. AGAFPBCONS3: Agios Stefanos-After prescribed burning_Control Site_2023. AGBPBCONS3: Agios Stefanos-Before prescribed burning_Control Site_2022.

Table 3. Flame length (F_L, m), fireline intensity (I, kW·m⁻¹), post-burn Shannon diversity index and Shannon difference values.

Sampling Point	Shannon Index (Post-Burn)	Shannon Difference ¹	F_L	I	Method Used
I1	1.50	1.00	1.0	302 *	[61] *
I2	1.23	−0.14	0.7	157
I3	1.78	0.44	0.8	200
I4	1.61	0.49	0.5	84
I5	2.21	0.24	1.3	1241	[62] **
I6	2.54	0.14	0.8	424
I7	2.26	1.09	1.0	695
I8	2.10	0.52	0.5	150
I9	1.91	0.35	1.80	2695
I10	2.01	0.41	1.00	695	[63] ***
I11	1.98	0.81	1.2	1040
I12	2.09	0.61	0.8	424
I13	1.34	−0.08	0.80	307	[64] ****
I14	1.06	−0.02	1.2	700	[64] ****
I15	1.09	0.00	1.0	302	[61] *
I16	1.11	−0.01	1.6	718	[61] *

¹ “Shannon difference” represents the change in plant diversity, calculated as post-burn minus pre-burn values. * Fernandes et al. [61], for litter in Mediterranean pine forests. ** Fernandes et al. [62], for shrublands, namely Cistus sp. and Sarcopoterium spinosum. *** Clark [63], for heading fire spread in grasslands. **** Nelson and Adkins [64], for heading fire spread in Mediterranean pine forest litter.

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Solomou, A.D.; Athanasiou, M.; Korakaki, E.; Michopoulos, P.; Karetsos, G. Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems. Diversity 2025, 17, 768. https://doi.org/10.3390/d17110768

AMA Style

Solomou AD, Athanasiou M, Korakaki E, Michopoulos P, Karetsos G. Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems. Diversity. 2025; 17(11):768. https://doi.org/10.3390/d17110768

Chicago/Turabian Style

Solomou, Alexandra D., Miltiadis Athanasiou, Evangelia Korakaki, Panagiotis Michopoulos, and Georgios Karetsos. 2025. "Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems" Diversity 17, no. 11: 768. https://doi.org/10.3390/d17110768

APA Style

Solomou, A. D., Athanasiou, M., Korakaki, E., Michopoulos, P., & Karetsos, G. (2025). Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems. Diversity, 17(11), 768. https://doi.org/10.3390/d17110768

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Prescribed Burning in Greece: Monitoring of Water Potential, Fireline Intensity, Soil and Plant Biodiversity in Mediterranean Ecosystems

Abstract

1. Introduction

2. Materials and Methods

2.1. Study Area

2.2. Samplings

2.2.1. Vascular Plant Diversity

2.2.2. Soil Sample Processing

2.2.3. Fireline Intensity (Ι)

2.2.4. Needle Water Potential

2.3. Statistical Analyses

3. Results

3.1. Plant Composition and Diversity

3.2. Soil Parameters

3.3. Fire Behaviour and Plant Diversity

3.4. Needle Water Potential

4. Discussion

4.1. Plant Composition and Diversity

4.2. Soil Parameters

4.3. Fire Behaviour and Plant Diversity

4.4. Needle Water Potential

5. Conclusions

Author Contributions

Funding

Institutional Review Board Statement

Data Availability Statement

Acknowledgments

Conflicts of Interest

Appendix A

Appendix B

References

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