ROLE OF THE BRYOPHYTE COVER IN ACCUMULATION OF THE BIOGENIC ELEMENTS IN TECHNOGENIC SUBSTRATE ON THE TERRITORY OF SULFUR EXTRACTION

N.Ya. Kyyak, O.L. Baik

Institute of Ecology of the Carpathians, NAS of Ukraine

11, Stefanyk St., Lviv 79000, Ukraine

e-mail: kyyak_n@i.ua

INTRODUCTION

The new approach connected with the maximum utilization of regenerating possibilities of natural ecosystems for restoring resources and ecological functions of devastated territories – their “ecological restoration” has been formed in the world practice of technogenic geosystems rehabilitation. The use of potential of plants communities, adapted to antropogenically changed substrates gives a chance to decrease denudation processes intensity of technical earth to great extent and initiate the soil forming processes in them. The conception of technogenic geosystems renaturalization is not ecologically grounded, but economically justifies [9].

As the result of open-cast mine exploitation of native sulphur extraction on the territory of Novoyavorivsk state mining-chemical enterprise “Sirka” (L’viv region, Ukraine) a number of various age dumps formed both from the rocks which take part in zone soil formation and from bedding rocks which do not form soils (e.g. tertiary clays, sulphur containing limestones etc.) have been formed. The main problem in cultivating dump rocks is its alienation for biota and sometimes its toxicity. Population of rock substrates by microorganisms and pioneer plants promotes structuring of such substrates qualitative and quantitative changes of properties which identify the formation of young technogenic soils.

Bryophytes were among the first to settle on the dump substrates and formed thick, multispecific overgrowth [14]. Gradually dying off, the pioneer bryophyte species create the substrate for populating other mosses and vascular plants. The way in which bryophytes change technogenic substrate has not been investigated enough. It is known from literature that moss cover essentially influences both the soil formation processes and the ecological conditions inside ecosystem: hydrometric conditions in rhizosphere, soil acidity, mineral regime, deposition and carbon cycle [3; 12; 15].

However, the question of the mosses role in renaturalization of technical earth and on the territories of sulphur extraction remains not enough investigated. So, the aim of this work was to investigate the influence of bryophyte cover on accumulation of biogenic elements in the dump No1 substrate of Yazivsky sulphur deposit of state mining-chemical enterprise “Sirka.

MATERIALS AND METHODS

The object of investigation was bryophytes from the dump No 1 (near the village of Lis) of Yazivsky sulphur deposit (L’viv region, Yavoriv district), subordinated to Novoyavorivsk sulphur deposit of state mining-chemical enterprise „Sirka”. For investigations 3 moss species was chosen: Barbula unguiculata Hedw., Bryum argenteum L. and Bryum caespiticium Hedw. For investigation of bryophytes influence on accumulation of biogenic elements in the dump substrate, the substrate samples under moss cover have been chosen for the experiments and the surface substrate layer of 2-3 cm wide, where the bryophyte cover is of the greatest influence, has been analysed [18]. The samples of the base substrate (without plant cover) have been used as control. The investigations have been carried out on 3 investigated dump transects (the dump crest and 2 transects on the north and south slopes) in summer and autumn 2010-2012. The substrate has been chosen in 3 places within experimental plot; the average sample has been mixed and formed.

The content of total nitrogen in the substrate was determined by K’endal’ method [1], the phosphorus content was determined photocolourimetrically having the coloring intensity of phosphorus-molibdenum blue color, the potassium content was determined on the photometer PFM-BP-3ОМ3 [2].

All experiments were carried out three times. The obtained results were processed by the methods of statistical analysis [13].

RESULTS

Most scientists who investigated the processes of young grounds formation on the territories devastated by extraction of natural deposits point to the rapid accumulation rates of organic substance in posttechnogenic grounds [8]. The process is closely connected with the constant over-growth of plant cover productivity, that is, with the increase of plant fall quantity. On the basis of substrates analysis, on which moss turfs overgrow, it has been found out, that under moss cover formed by dense turf species Bryum caespiticium a clear interlayer of dark color – embryonic organic accumulative horizon made by the products of dying off turf has been formed. This interlayer is smaller under loose turfs Barbula unguiculata or Bryum argenteum especially on the slopes as turfs of these species are destroyed easily as the result of displacement of unstable substrate and hold the occupied area uneffectively compared to Bryum caespiticium. It has been noted that the thickness of bedding under moss turfs depends to great extent both on the specific properties and on the growth locality of plants on the dump slopes with rather complex climatic conditions. For example, in summer months substrate humidity amounted to 26.3-27.5 %, the light intensity was 6.5-8.5 thousand lux, the temperature on the substrate surface was +18.4 - +25.2⁰ C on the crest and the north dump slope. The top and the south dump slope are characterized by the least favorable conditions (substrate humidity 4.5-14.8%, light intensity was 10.0-11.0 thousand lux, the temperature on the substrate surface has increased to +32.2 - +37.5⁰C).

It has been found out that the highest percentage of the dead part (69.2-74.5% in a moss turf) was in the moss samples Bryum caespiticium from the north slope and on the dump crest and in Bryum argenteum from the crest and the south dump slope (66.3-68.9%), where these species have rather high indices of projective covering (fig. 1).

For Barbula unguiculata the thickness of the dead layer amounted to 52.2-58.4% in moss turfs and was also the highest on the north dump slope. It is necessary to note that species Bryum argenteum and Barbula unguiculata, which form short loose turfs, are typical of dry, open plots on the dump territory while dense turf species Bryum caespiticium has the maximum productivity in more humid localities.

Fig. 1. Correlation between photosynthetic (green) and dead part of moss shoots. Moss species: 1 – Bryum caespiticium, 2 – Bryum argenteum, 3 – Barbula unguiculata.

One of the main grounds characteristics determining their fertility and ability for plants population is their supply with nutritious elements. Technogenic dump substrate of sulphur extraction is not almost structuralized, it is characterized by insufficient absorbing and water keeping properties being poorly supplied with the main nutrition elements (nitrogen, phosphorus, potassium), that in complex defines its low potential fertility and adaptability to plants life activity. It is known, that bryophytes play an important part in the circulation of nutritious substances in ecosystem, in spite of relatively small part of their biomass compared to vascular plants [5; 6; 16]. Mosses can absorb nutritious substances from atmospheric air, precipitation, dust and keep them during long period of time in undecomposed part of dead shoots [17]. The main reasons of it are the conditions of bryophyte existence (low temperature, humidity, heightened acidity) as well as some of their physical and chemical properties (high cation exchange capacity, availability of essential content of lignin-like compounds and lipids [7].

Bryophyte role in accumulation of nitrogen in soil is estimated in numerous publications [3; 4; 5; 11]. It has been established, that the dead part of moss cover has rather high hydrolytic acidity, thanks to this factor the moss bedding is characterized by essential absorption ability and can contain not only hydrogen ions in great quantities, but also other elements, necessary for plants [18]. In the primary succession on the sands the rate of nitrogen accumulation in moss cover, formed by Polytrichum juniperium and Polytrichum piliferum amounted to 10.1 kg/hectare/year, 58% of accumulative nitrogen has been accumulated in moss bedding. This fact shows, that bryophyte component positively influences the edaphic conditions. To confirm such assumption, the moss cover was fully removed on the essential area of the investigated territory, and it has been found out that nitrogen losses in ecosystem essentially exceeded its entrance [5]. It has been established in arctic ecosystems that some species of Sphagnum genus as well as Hylocomnium splendens and Pleurozium shreberi accumulate three times as much nitrogen and phosphorus, than Picea marina [12].

We have established that mosses also influence accumulation of nitrogen and phosphorus in the substrate on the dump territory of sulphur extraction. The highest indices of their content have been determined in the substrate under mosses Bryum caespiticium and Bryum argenteum. In the substrate under moss cover formed by dense turf species Bryum caespiticium the gross nitrogen content has increased 2.0-3.5 times, phosphorus content has increased 1.2-1.4 times compared to their quantity in bare substrate (table 1). Under moss turfs Bryum argenteum the nitrogen quantity has increased 1.4-2.4 times, phosphorus – 1.2 times (on south slope). Nitrogen content in the substrate has increased 1.2-1.3 times, but the control difference in phosphorus was not authentic.

Microclimatic conditions on the dump territory also influence accumulation of nitrogen and phosphorus in the substrate, as the highest content of these elements was determined in the substrate on the dump crest, but the lowest content was on the south dump slope, that is, the dependence on the conditions of plant localities is observed. Perhaps, the high insolation level on the south dump slope influences these indices as for many moss species negative correlation between nitrogen and phosphorus accumulation and light intensity has been established [17].

Table 1.

Gross nitrogen, phosphorus and potassium content under moss cover

on the dump No 1 territory

Locality of substrate samples collection under moss turfs	Content of nitrogen, %	Content of phosphorus, %	Content of potassium, %
Uncovered substrate (control)
Crest of the dump	0,10±0,01	0,09±0,01	1,76±0,01
North slope	0,09±0,01	0,09±0,01	1,76±0,02
South slope	0,09±0,01	0,08±0,01	1,74±0,03
Bryum caespiticium
Crest of the dump	0,35±0,02*	0,13±0,01*	1,85±0,02*
North slope	0,22±0,01*	0,12±0,01*	1,81±0,01*
South slope	0,16±0,02*	0,10±0,01	1,74±0,02
Bryum argenteum
Crest of the dump	0,20±0,02*	0,11±0,01	1,78±0,01
North slope	0,13±0,01*	0,10±0,01	1,78±0,01
South slope	0,22±0,03*	0,11±0,01*	1,74±0,01
Barbula unguiculata
Crest of the dump	0,12±0,01*	0,11±0,01	1,85±0,02*
North slope	0,12±0,01*	0,11±0,01	1,81±0,01*
South slope	0,10±0,01	0,08±0,01	1,74±0,02

Footnote – * the difference compared to control (base substrate) is statistically reliable at p<0,05.

The mosses role in potassium accumulation in upper mineral ground horizon has been shown in a number of publications [10; 18]. These investigations deal mainly with mosses which get used to the life in the forest cenoses (species of the genus Sphagnum, Pleurozium shreberi, Dicranum polysetum). The analysis of potassium content in the dump substrate has not shown the essential differences between its quantity in bare substrate and in the substrate under bryophyte cover.

Perhaps, the reason of this is in specific properties or specific character of ions in moss shoots, as it has been established that univalent cations (for all K⁺) are most of all concentrated in the shoot apex, but divalent cations are located in the basal old part [6]. In our experiments reliable increase of potassium content in the substrate has been fixed on the crest and the north dump slope only under moss turfs Bryum caespiticium and Barbula unguiculata.

Thus, it has been established that bryophytes promote enrichment of the dump substrate with biogenic elements. Interrelation exists between degree of moss turfs decomposition and accumulation of biogenic elements in substrate under moss cover. The life form of mosses has essential influence on the process since the highest indexes of nitrogen and phosphorus content were fixed in substrate under the moss B. сaespiticium with dense turfs. The important role is also played by concrete ecological conditions on slopes of the dump.

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