**3. Results**

#### *3.1. Coenosystematic Results*

Based on the coenosystematic results (the role of each species within the association), association group *Festucon vaginatae* di ffered the most from the others (based on mostly *Stipa borysthenica, Alkanna tinctoria, Centaurea arenaria, Dinathus serotinus* and *Koleria glauca* (Figure 2). In *F. vaginata* grasslands the proportion of these open sandy grassland species was particularly high and varied between 40 and 70% in every sample area. In *F. pseudovaginata* grasslands these taxa covered only 10–20%. In *F. wagneri* grasslands these ratios were similar to those found in the central region, although in the northern (III.1.Fw, Csallóköz) and southern (III.4.Fw, Deliblato) areas they dropped under 10%.

The proportion of *Festuco-Brometea* Br.-Bl. et R. Tx. ex Klika et Hadaˇc 1944 was higher on the outer edges of the examined region (I.1.Fv, III.4.Fw). Based on the common taxa of *Festucetalia valesiacae* and *vaginatae* it was clear that *F. pseudovaginata* grasslands showed a transition, especially in the area described as shrub-forest mosaic (II.2.Fp). There were substantial di fferences among the elements of subcontinental arid grasslands (*Festucetalia valesiacae* Br.-Bl. and R. Tx. ex Br.-Bl. 1949) with regard to their relative proportions, too. These elements, as key taxa of sandy steppes, occurred primarily in the northernmost *F. vaginata* grasslands in the Little Hungarian Plain. In *F. pseudovaginata* grasslands their proportions were higher in the shrub-forest area (II.2.Fp). In *F. wagneri* grasslands, their cover values were found to be the highest in the northern part of Danube-Tisza Interfluve and at Deliblato (III.2.Fw and III.4.Fw). In the Deliblato area the following species were found in large numbers: *Adonis vernalis*, *Carex humilis* and *Jurinea mollis. F. tomanii* was rated in *Festucetalia valesiacae* based on its occurrences. Elements of *Festucetum rupicolae* were found only in two sample areas: in the forest parts of *F. pseudovaginata* grasslands and in the Northern Kiskunság patches of *F. wagneri*.

**Figure 2.** Coenosystematic composition of the grassland types under investigation. (*Festuca vaginata* vegetation types: I.1.Fv: Little Hungarian Plain, I.2.Fv: northern part of Kiskunság, I.3.Fv: southern part of Kiskunság, I.4.Fv southernmost part. *Festuca pseudovaginata* II.1.Fp: degraded type dominated by weeds, II.2.Fp: woody patches, II.3.Fp: natural patches; *Festuca wagneri* III.1.Fw: Csallóköz, III.2.Fw: Northern part of Kiskunság, III.3.Fw: Southern part of Kiskunság, III.4.Fw: in the southernmost part, Fes vag.: *Festucion vaginatae*, Fes. vag. and *Festucetalia vaginatae* and *valesiacae,* F-B.: *Festuco–Brometea*, Fes.val.: *Festucetalia valesiacae*, Fes.rup.: *Festucion rupicolae*, Qu.pub.p.: *Quercetea pubescentis-petreae*, P.: Prunion, Ar.: Arrhenatheretea, Ch. and Sec: Chenopodietea and Secaalietea, Onopordietea. A.-P.: Alno-Padion).

Weed vegetation elements (Chenopodietea and Secalietea Onopordietea) occurred mainly in weedy patches of *F. pseudovaginata* grasslands (II.1.Fp.) (i.e., *Anchusa o*ffi*cinalis, Aslepias syriaca, Carduus nutans, Portulaca oleracea, Setaria viridis* and *Tragus racemosus*). Taxa of European sub-Mediterranean and subcontinental forests occurred in the forest-steppe patches of *F. pseudovaginata* (*Quercetea pubescentis-petreae* (Oberd., 1948) Jakucs, 1960) (i.e., *Berberis viulgaris, Echinops schaerocephalon, Hierochloë repens* and *Veronica chamaedrys*). These elements were also found in *F. vaginata* grasslands, although with lower cover values, in the northernmost and southernmost areas. Forest taxa occur also in *F. wagneri* grasslands, mainly in the northern part of the Sand Ridge (III.2.Fw).

#### *3.2. Diversity Results*

Based on the <sup>R</sup>ény<sup>i</sup> diversity profile (Figure 3), it was clear that the most diverse vegetation type was *F. pseudovaginata*.

#### *3.3. Ecological Values*

We also analyzed the distribution of the relative ecological indices in the vegetation units, i.e., relative temperature, water requirements and continentality values.

*F. vaginata* grasslands were inhabited by species with the highest temperature requirement (value 8), although taxa with a value of 9 were to be found in secondary, weedy *F. pseudovaginata* grasslands (II.1.Fp). In *F. wagneri* grasslands, value 7 was the most common. On the two edges of the survey area, the coverages of half-shadow (value 5) and half-shadow–half-light (value 6) species were the highest. (Figure 4a).

**Figure 3.** <sup>R</sup>ény<sup>i</sup> diversity of the grasslands (*Festuca vaginata* vegetation types: I.1-4.Fv, *Festuca pseudovaginata* II.1-3.Fp and *Festuca wagneri* III.1-4.Fw).

(**a**) 

(**b**)

**Figure 4.** *Cont*.

**Figure 4.** Proportions of the species based on relative ecological indices. (**a**) TB (relative temperature), (**b**) WB (relative water requirements) and (**c**) NB (nitrogen requirements). *Festuca vaginata* vegetation types: I.1.Fv: Little Hungarian Plain, I.2.Fv: northern part of Kiskunság, I.3.Fv: southern part of Kiskunság, I.4.Fv southernmost part. *Festuca pseudovaginata:* II.1.Fp: degraded type dominated by weeds, II.2.Fp: woody patches, II.3.Fp: natural patches. *Festuca wagneri:* III.1.Fw: Csallóköz, III.2.Fw: Northern part of Kiskunság, III.3.Fw: Southern part of Kiskunság, III.4.Fw: in the southernmost part. 1–9: see Materials and Methods.

Based on relative soil moisture requirements, *F. vaginata* differed from the others the most (Figure 4b). In the shrub-forest patches of *F. pseudovaginata* several species occurred, which indicated the borders of a wetter environment. Drought-tolerant species, which also occur in fresh habitats occasionally (value 3), were typical of *F. wagneri* grasslands.

Based on relative nitrogen requirements, *F. vaginata* differs again (Figure 4c). They contained the highest number of nutrient-poor patches. The shrub-forest patches of *F. pseudovaginata* were inhabited by species, which indicated larger amounts of nitrogen, which was also true for *F. wagneri* grasslands.

Species with continentality value of 9 (eucontinental), which occur very rarely in the Carpathian Basin, were to be found in the weedy grassland of *F. pseudovaginata* (II.1.Fp). Taxa with a value of 8, which are continental species marginally appearing in Central Europe, were also found. Value 7 (continental–subcontinental taxa with an Eastern European centre) had the largest proportion. Value 6 is a subcontinental category with a Central European centre; it also appeared along with value 5 (transitional types, with slight suboceanic and subcontinental features) (Figure 5).

**Figure 5.** Proportion of the taxa based on their ability to tolerate extreme climatic effects. KB: continentality. *Festuca vaginata* vegetation types: I.1.Fv: Little Hungarian Plain, I.2.Fv: northern part of Kiskunság, I.3.Fv: southern part of Kiskunság, I.4.Fv southernmost part. *Festuca pseudovaginata* II.1.Fp: degraded type dominated by weeds, II.2.Fp: woody area, II.3.Fp: natural area. *Festuca wagneri* III.1.Fw: Csallóköz, III.2.Fw: Northern part of Kiskunság, III.3.Fw: Southern part of Kiskunság, III.4.Fw: in the southernmost part. 1–9: see Material and Methods.

#### *3.4. Pedological Results*

The soil conditions were quite homogenous in the studied areas but small scale differences in the rate of development, SOM (soil organic matter) and carbonate content were detected in the different *Festuca* spp habitats.

The soil type under *F. vaginata* was described as Calcaric Arenosol [59] with ACk Ck profile development [57], which represents a very weakly developed calcareous soil with sandy texture (Figure 6). Based on our results, *F. vaginata* usually occurs in areas with the least developed, strongly calcareous sandy soil patterns, where we measured the lowest organic carbon (0.2%), and the highest carbonate content (11.3%) (Table 1).

**Figure 6.** Soil profiles with genetic horizons [54] and classification according to the World Reference Base for Soil Resources [55]. (**a**) Calcaric Arenosol under *F. vaginata;* (**b**) Calcaric Arenosol under *F. pseudovaginata* and (**c**) Calcaric Brunic Arenosol under *F. wagneri.*


**Table 1.** Basic soil chemical parameters of the genetic horizons of the soils profiles sampled under *F. vaginata*, *F. pseudovaginata* and *F. wagneri* sites.

The soil under *F. pseudovaginata* was more developed with Ak Bwk 2Ck profile development [54] showing moderate accumulation of humified organic matter in the surface horizon with higher organic carbon content (1.1%) and lower carbonate content (6.9%) than in the topsoil of the *F. vaginata* habitat (Table 1).

The soil profile showed lithic discontinuity under the Ak Bwk horizons at 18 cm depth, indicated by the presence of common (5–10%) fine and medium (2–10 mm) rounded gravel content of the surface horizons compared to the underlying gravel free sand layer. The thin appearance of this surface layer can be explained by deforestation or other human impacts, which caused deflation and thus the loss of the former surface and surface close horizons. The recent, weakly developed and humus rich A horizon may have developed on the top of the remnant B horizon of the truncated soil, which was eroded to the surface.

As a result of this thin, weakly developed appearance of the described horizons, the soil under *F. pseudovaginata* was also classified as Calcaric Arenosol [55] but the morphology of the Bw horizon (at a

depth of 5–18 cm) still supported our hypothesis of the presence of a former forest vegetation cover in the area. The olive brown (Munsell 2.5 YR 4/3 moist) color, and the weak granular structure are typical features of pedogenic alteration, which is characteristic for the weakly developed forest soils of the Carpathian Basin. These soils are called "Brown earths" in the genetic based Hungarian soil classification system [42], and "Cambisols" (or "Brunic Arenosols" in case of coarse sandy texture) according to the World Reference Base for Soil Resources [55].

The most developed soil profile of the studied area was described under *F. wagneri*. The solum was 125 cm thick with A AB Bw BC 2Ckl profile development and the soil was classified as Calcaric Brunic Arenosol [55] indicating obvious signs of soil formation with horizon di fferentiation in the sandy subsoil. Both the morphology and the chemical properties of the genetic horizons were found typical for soils developed under (former) forest vegetation. The soil showed relatively deep humus rich A horizon (0–20 cm), transitional character (AB horizon between 20–60 cm) and had a Bw horizon (at 60–95 cm depth) with brownish discoloration (Munsell 10 YR 4/4 moist), soil structure development (weak to moderate, medium subangular blocky) and leached, carbonate free characteristics. The presence of deep, transitional A and AB horizon indicated stabile surface with closed vegetation cover, which saved the humus rich soil material from deflation and degradation.

## **4. Discussion**

Due to significant changes in the vegetation taking place in the last few hundred years, the central sandy grassland, forest-steppe areas of the Carpathian Basin became mosaic-like [6,66] but the present survey confirmed that several patches of the original vegetation was still preserved. At the same time, new opportunities opened up for new species and associations to settle, or even new taxa to form. For the same reason, invasive species could also invade more easily [31,67].

Based on the results we could confirm that *Festuca vaginata* was to be found all along the Danube in sandy soils in the Carpathian Basin but it is still uncertain whether its habitat spreads all the way to the Black Sea [5]. Based on our concurrent surveys it spreads only to Romania [6,68]. Basically, this species inhabits the open sandy grasslands, in the association of *Festucetum vaginatae* Rapaics ex Soó 1929 em. Borhidi 1996.

In earlier literature, *Festuca vaginata* was treated as the only dominant grass taxon of the open calcareous sandy grasslands. This was debated by [69] when finding *F. wagneri* in Hungary for the first time, although he treated it as a forest-steppe species. There was no consensus on the coenological affiliation of *F. wagneri,* although its taxonomy was clarified by [70] when describing it as a separate species. Since older specimens lose their epidermal hairs and their sclerenchime becomes annular, a greenish grass taxon was identified as F. wagneri in samples of *F. vaginata* grasslands, until [71] described it as a new species named *F. pseudovaginata,* which also forms an association new to science [72]. Later it was confirmed that the soil parameters of this association differ greatly from the others' [73] in terms of Ca and Mg contents. However, in the present survey soil profile was conducted for the first time, and its analysis confirmed what the environmental backdrop *F. pseudovaginata* indicated. This species evolved on forest soils. The soil profile showed 1.5 m deep forest soil and the amount of organic matter was higher. The relative ecological indices showed [50] that the vegetation type appeared under wetter conditions and based on their nitrogen requirement values, the soil was more nutrient-rich, which was also confirmed by the soil profiles.

*F. pseudovaginata* is endemic in the Pannonian region, it inhabits only the central sandy area of the Carpathian Basin. Ref. [74] provided data from the Romanian border, as its first occurrence in the country. However, there are still some uncertainties about it because *F. pseudovaginata* is tetraploid, while the specimens found were all diploid [75].

Coenosystematic analysis showed *F. pseudovaginata* mainly in forest-shrub areas and the samples also contained elements of *Quercetea pubescentis-petreae* and steppe taxa. In *F. wagneri* grasslands, proportion of taxa of *Festucetalia valesiacae* and *Festuco-Brometea* was higher. In addition, all three vegetation types were less diverse at their northern and southern edges and contained also forest, steppe and closed grassland species in larger proportions.

The present study was not extended to examine the border areas between sandy grasslands and forest vegetation, similarly to numerous invaluable and detailed works [23–25,76,77], although they did not examine the dominant *Festuca* taxa in detail. The present survey is part of a series of investigations, which examine the sandy grasslands along the Danube and the taxonomic conditions of the *Festuca*. As a result of our present study a new species was also discovered. Based on the soil profiles, it was clarified that these *Festuca* taxa can be used as indicators of disturbances in the vegetation or the onetime locations of forest patches.

*F. pseudovaginata* forms an association [72], not only under artificial circumstances as seen in Újpest but also at Kunpeszér-Kunadacs, where the vegetation indicates natural processes. The later is the largest continuous sandy grassland along the Danube in the Hungarian Plain, where the chances for vegetation types to evolve were the highest and its diverse environment gave an opportunity for mosaic-like landscape structure to form.

In conclusion, we answered our questions as follows: (i) According to our results, *F. vaginata* and *F. wagneri* grasslands can be considered as seminatural habitat based on their species composition and ecological indicators. *F. pseudovaginata* grasslands are mainly disturbed but natural patches were also found. (ii) Soils of *F. pseudovaginata* and *F. wagneri* indicate the onetime forest patches. (iii) The composition vegetation indicates its relationship with forest-steppes. Coenosystematic analysis showed *F. pseudovaginata* mainly in forest-shrub areas and the samples also contained elements of *Quercetea pubescentis-petreae* and steppe taxa. In *F. wagneri* grasslands, the proportions of taxa of *Festucetalia valesiacae* and *Festuco-Brometea* were higher. In addition, all three vegetation types were less diverse at their northern and southern edges and contained also forest, steppe and closed grassland species in higher proportions. (iv) The vegetation follows the aridification of the climate fast and changes rapidly into dry sandy grasslands form. The pedological results showed the memories of the changes of the soil. Answering the question in the title, the dominant *Festuca* species and their proportions and cover values will be the memory that indicates the vegetation types of the past in the area.

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

**Funding:** This research was funded by OTKA K-125423.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available because the OTKA project is not completed yet.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
