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SOIL SCIENCE
Content of available forms of nitrogen, potassium and phosphorus in ornithogenic and other soils of the Fildes Peninsula (King George Island, Western Antarctica)
Evgeny Abakumov
Department of Applied Ecology, Faculty of Biology, Saint Petersburg State University, 16th Liniya V. O., 29, Saint Petersburg, 199178, Russian Federation
Address correspondence and requests for materials to Evgeny Abakumov, e_abakumov@mail.ru
Abstract
Citation: Abakumov, E. 2018. Content of available forms of nitrogen, potassium and phosphorus in ornithogenic and other soils of the Fields Peninsula (King George Island, Western Antarctica). Bio. Comm. 63(2): 109-116. https://doi.org/10.21638/ spbu03.2018.203
Author's information: Evgeny Abakumov, Dr. Sci., Professor, orcid.org/0000-0002-5248-9018
Manuscript Editor: Prof. Cezary Kabala, Institute of Soil Science and Environmental Protection, Wroclaw University of Environmental and Life Sciences, Wroclaw, Poland
Received: February 19, 2018;
Revised: June 11, 2018;
Accepted: June 16, 2018;
Copyright: © 2018 Abakumov. This is an open-access article distributed under the terms of the License Agreement with Saint Petersburg State University, which permits to the authors an unrestricted distribution and self-archiving free of charge.
Funding: This work was supported by the Russian Foundation of the Basic Research (projects No 16-34-60010 and No 18-04-00900).
Competing interests: The author has declared that no competing interests exist.
Maritime Antarctica is an interesting object for soil scientists because most of them nowadays or recently were exposed to ornitogenic effect. Soils of the Fildes Peninsula have been investigated in terms of chemical composition and available nutrients concentration. Four groups of soils with various ornitogenic effect were selected for chemical analyses: current ornitogenic soils, soils of former birds habitats — organogenic mates, natural soils without current evident bird effect — Lithosols and Technosols. Ornitogenic effect is evident in soil formation in three types of soils investigated. The maximum effect of organic matter transportation and accumulation is pronounced in Ornitogenic soils and Organogenic mat. The last one are considered as recently been colonized by birds and this fact was the reason for initiation of formation of organogenic mats due to accumulation of nutrients. Some residual effect of birds can be revealed in Lithosols, where increased content of ammonium ions and available phosphorus was fixed. Thechnosols as soils constructed from local mineral grounds have no any evidences of ornitogenic accumulation. We suggest that, majority of soils, situated on Fildes peninsula recently were exposed to ornitogenic effect. Ornitogenic effect resulted in formation of modern soil cover of the Fildes Peninsula.
Keywords: Antarctica, ornithogenic soils, nutrients, nitrogen, phosphorus, potassium.
Introduction
Soils of the Antarctic region are very diverse and represent numerous orders and types. The extreme conditions of soil formation in this region result in the formation of weakly developed profiles in conditions of organic remnants deficit. Normally pedogenic processes are occur mainly by transformation of organic remnants within the mineral matrix with essential fine-earth content. At the same time, there are many soils and soil-like bodies in extreme environments that form from the accumulation of zoogenic organic matter on relatively unweathered parent rocks with a low fine earth portion. Antarctic soils have been investigated by many researchers (Kubiena, 1970; Campbell and Claridge, 1987; Bockheim and Ugolini, 1990; Zhao, 2000; Parnikoza et al., 2007, 2016; Korsun et al., 2008; Mer-gelov et al., 2012; Lupachev and Abakumov, 2013; Abakumov, Gagarina, Sapega, and Vlasov, 2013; Abakumov, Parnikoza, Vlasov, and Lupachev, 2016; Abakumov, 2017). It was shown that areas occupied by soils are concentrated in ice- and snow-free areas (Bockheim, 2015), which are estimated to make up 0.35% of Antarctica's total area, 44 000 sq km.
Soils are mainly formed under monospecies populations of fungi, lichens, mosses and vascular plants. Mul-tispecies ecosystems are also described as a significant source of soil organic matter. Meanwhile, the low intensity of photosynthesis and low productivity of ecosystems result in relatively low accumulation of humus and raw organic matter (Campbell and Claridge, 1987; Abakumov, 2010). In these conditions, organic matter of ornithogenic origin became a key factor in initialization of soil formation. Classical soils, formed under plants, are represented by Leptosols, Gleysols, Histosols, Cryosols and others (WRB, 2014). Besides them, the major representative of soil in Antarctica are ornithogenic soils. There is verifi-cator "Ornithic" in the WRB classification system (WRB, 2014), but there is no special type of ornithogenic soils in this classification. Ornithogenic material is material with a strong morphological and chemical influence of birds on soils. The term "ornithogenic soils" has become more and more usable for those soils which have morphological and chemical features related to ornithic definition. Thus, it is possible to classify soil as Ornithic Leptosols, Ornithic Cryosols, Ornithic Gleysols, etc.
Ornithogenic soils have previously been revealed in all coastal parts of Antarctica (Bockheim et al., 2015). These territories have been studied as habitats of soil fungal communities, which can be indicators of soil biological activity (Vlasov et al., 2012). In general, penguins play the most important role in organic matter accumulation, rock transformation, chemical weathering and or-nithogenic soil formation (Simas et al., 2007; Shaefer et al., 2008). Penguin guano is enriched by organic carbon, nitrogen and phosphorus. Locations of stable guano accumulation in Antarctica are known as penguin (or other bird) rookeries and single nest places. They occupy different levels of landforms, and therefore redistribution of organic matter in the landscape becomes possible (movement of guano leachates from hills to valleys). The guano accumulations affect soils not only in vertical scale, but also play an important role in initial accumulation of bio-genic elements in geochemically subordinated positions. As a result, the soils of the coastal zone of Antarctica have been subjected to a direct or indirect guano impact during their history. This is the most characteristic feature of soils formed in the maritime Antarctic and in rookeries in the coastal zone of Eastern Antarctica. The phenomenon of postornithogenic succession has been described by many scientists (Ramsay, 1983; Simas, 2007; Abakumov and Mukhametova, 2014). On exposed rocks with severe conditions for plant growth, an accumulation of ornithogenic organic matter leads to development of so-called "ornithogenic" lichens (e.g. Caloplaca) and ni-trophilous algae Prasiola crispa (Lightfoot) Kutzing.
In areas with more favorable conditions for the development of the various formations of Antarctic terrestrial vegetation, fairly simple ecosystems can form, with
the participation of mosses, lichens, and in particularly favorable conditions — vascular plants, such as De-shampsia antarctica Desv (Kozeretska et al., 2010). So, the bird's biogeochemical activity is known as the reason for intensive soil development in the Antarctic environment (Simas et al., 2007). The second aspect is the direct transportation of the vegetative parts and diasporas of plants from new places or from the coastal part to the central parts of oases, previously unaffected by these species. This is an outstanding example of the effect of birds on local biodiversity, plant expansion in territories following glacial retreat, and soil processes intensification in Antarctica (Parnikoza et al., 2016).
So, the ornithogenic effect on soils can be very different: direct effect of guano on soils; indirect effect, expressed in redistribution of guano leachate in spatial scale and redistribution of seedlings in ecosystems due to ornitohoria. A geochemical effect can by evident or may be postponed for a long time in soils which are not currently occupied by birds. That is why this work was intended to compare nutrient content in soils with differently pronounced ornithogenic effect.
Materials and methods
STUDY SITES
King George Island is the largest in the South Shetlands archipelago at about 1400 km2 (Fig. 1). Only about 5% of its area is free of ice (Rakusa-Suszczewski, 2002). The Fildes Peninsula and Ardley Island together (around 33 km2) comprise the second largest ice-free area of the South Shetland Islands and the largest on King George Island. Gentle topography dominates the Fildes Peninsula, with a wide central plain and several others at different altitudes. It is a tableland made up of old coastal landforms with numerous rocky outcrops and an average height of 30 m a.s.l. (Michel et al., 2014).
According to Smellie, Pankhurst, Thomson, and Davies (1984), this area mainly consists of lavas with small outcrops of tuffs, volcanic sandstones and agglomerates. The climate here is cold, moist and maritime with a mean annual air temperature of -2.2°C and mean summer air temperatures above 0°C for up to four months (Wen, Xie, Han, and Lluberas, 1994). The mean annual precipitation is 350-500 mm/yr. Fildes Peninsula and Ardley Island are among the first areas in Maritime Antarctica to become ice-free after the last glacial maximum (Birkenmajer, 1990). The Fildes Peninsula was covered by glaciers from 8000 to 5000 years BP (Mausbacher, 1989; Michel et al., 2014). The basins of most lakes are over-deepened glacial basins, and the valleys of the largest streams are glacial troughs — both are located along fractures. After the glacial erosive phase, glacial retraction led to the Holocene glacioisostatic and tectonic up-
2°15's I • Ecq Nelson (CZEJ Fig. 1. Location of King George Island
lift and favored the occurrence of paraglacial and peri-glacial processes such as frost weathering, gelifluction, cryoturbation and nivation (Simonov, 1977; Jeong, 2006; Navas et al., 2008; Lopez-Martinez et al., 2012).
The patterned ground in this region dates from 720 to 2640 years BP. In the South Shetland Islands, permafrost is sporadic or non-existent at altitudes below 20 m a.s.l., and occurs more or less discontinuously in altitudes from 30 to 150 m a.s.l. (Bockheim et al., 2013). Mosses, lichens, and algae are common here, along with two vascular plants (Deschampsia antarctica and Colo-banthus quitensis). Penguins, seals, and seabirds are common in coastal areas and have significant effects on soil development. Major cryogenic surface-forming processes here are frost creep, cryoturbation, frost heaving and sorting, gravity and gelifluction (Michel et al., 2014). Eight separate sites on the Fildes peninsula have
been collectively designated an Antarctic Specially Protected Area (ASPA 125), largely because of their paleon-tological values (Management plan..., 2009).
SAMPLING STRATEGY
Soils were sampled from 20x20 cm soil pits at depths of 0-10 cm. The Edelman drill (modification for soils) with stainless nozzle (prewashed with acetone) was used for sampling. The samples were stored in double sterile plastic bags, labeled and transported to the laboratory. The samples were air-dried at room temperature, separated from roots and debris, and passed through a 2-mm plastic sieve prior to chemical analysis. All soil samples were divided into 4 groups: 1) ornithogenic soils; 2) organogenic mats; 3) Leptosols without evident direct effect of bird activity, and 4) soils affected directly or indirectly by
Table 1. Sample list
Sample code Coordinates Landform Soil
1 62.11 33,9 ,058.55483 Marine terrace close to Neftebasa Leptosol, Ornitic, A
2 62 12 36,2, 058 55 43,3 Marine terrace, Ardley peninsula Lithosol, Ornitic, A
3
4 62.13077, 058.45550 Marine terrace Leptosol, Ornitic, A
5 62.10583 , 058. 58498 Ridge, covered by nest of Skua Leptosol, Ornitic, A
6 62.11080, 058.58300 Valley on the way to Drake passage, proluvial sediments, covered by mats Histic Fluvisols, A
7 62.10518, 058.55.053 Hills close to Artigas station, covered by mat Regosol, C
8 62.12 400, 058 56166 Flat upland covered by mat, Ardley Island Cryosol, A
9 62.12 400, 058.56471 Flat upland covered by mat, Ardley Island Cryosol, A
10 62.09147, 058.55167 Moraine hills close to Collins glacier Regosol, A and C horizons
11
12 62.14480, 058.58454 Ridge, Nelson Island, covered by algae and lichens, possible former presence of birds Leptosol, A
13 62.10 450, 058.58525 Marine terrace in Tylenya bay, moss cover Leptosol A
14
15 62.11024, 058.5134.0 Ridge covered by Deshampsia antrarctica, possible former presence of birds Leptosol A and C horizons
16 62.11 519, 058. 57199 Former waste disposal close to Bellinshausen station Technic Cryosol, topsoil, 2 samples
17
18 62.11483 , 058. 57476 Bellinshausen station, close to old diesel station Technic Cryosol, topsoil
19 62.09146, 058 55 15,9 Territory of Bellinshausen station Technic Cryosol, topsoil
20 62.09146, 058.55159 Territory of Bellinshausen station Technic Cryosol, topsoil
humans (waste disposal, station activity and mechanical disturbance). In total, 20 samples were analyzed. Soil types were identified on the basis of morphological field description of whole profiles (IUSS Working Group WRB, 2015), in spite of the fact that samples were collected only from the superficial layers. Soils from Elephant Island were mostly Turbic Cryosols and Leptosols under sparse mosses and lichen vegetation cover. The average thickness of the soil profiles was about 15-25 cm. Soils of King George Island were represented by six soil groups (IUSS Working Group WRB, 2015): Leptosols, Cryosols, Fluvisols, Regosols, Histosols and Technosols. This corresponds well with previously published data (Navas et al., 2008). Soil was sampled from the non-living part of organogenic or organo-mineral layers.
Ornithogenic soils studied here were mostly made up of polypedons under transported plant material. Birds use it for nest building, and this activity results in accumulation of essential portions of organic matter in the uppermost layers (up to 25%). We suggest that bird transport
activity can result in the accumulation of additional portions of trace elements. Background mineral soils without evident bird activity were studied in pristine (Turbic Cryosols, Cambisols, Regosols, Leptosols) and human-affected environments (Technic Turbic Cryosols and soil in the area of Bellingshausen station and former waste disposals). Thus, we can compare the levels of trace elements accumulation in four groups of soils — two of these serve as the reference (pristine soils of Elephant and King George); the other two are affected by geochemical activity of ornithogenic or anthropogenic origin. The average thickness of O and A horizons variate in investigated soils was about 3-8 cm. Only in the case of Histic Fluvisol, the thickness of the AO horizon was 12 cm.
LABORATORY METHODS
Soil samples were air-dried, ground and passed through a 2-mm sieve. pH values were determined in soil-water or soil-CaCl2 solution; the ratio of soil and solution was 1:2.5.
Total organic carbon and nitrogen were determined with a C-H-N- analyzer (Euro EA3028-HT). For the extraction of ammonium nitrogen, we used KCl (EPA method 350.1., August 1993). Mobile phosphorus and potassium content was determined using their extraction by 0.5 mol/L HCl (Kuo, 1996). The evaluation of the main agrochemical characteristics was performed by the standard procedures recorded in GOST 54650-2011 (for evaluation of mobile phosphorus and potassium contents) and GOST 2648985 (for evaluation of ammonium nitrogen content).
STATISTICS
Statistical data treatment used STATISTICA 10.0 software (ANOVA, Statistica Base 12.6, Dell, Round Rock,
TX, USA). One-way ANOVA was applied to test the statistical significance of differences between obtained data. This method is based on estimation of the significance of average differences between three or more independent groups of data combined by one feature (factor). A post-hoc test (Fisher LSD) provides a detailed evaluation of the average differences between the analyzed groups of data. A feature of the post-hoc-test is application of intra-group mean squares for the assessment of any pair averages. Differences were significant at the 95% confidence level. Concentrations of nutrients and biogenic elements were analyzed with at least three replicates. The calculated average concentrations were provided with standard deviations (a ± b).
Table 2. The content of available forms of nutrients, bulk content of carbon and nitrogen and pH values of various soil groups.
Sample code P2O5 K2O N-NH4 N-NO3 C N C/N pHwater pHCaCL2
Mg * kg-1 %
Ornithogenic soils
1 772 992 572.3 165.5 8.45 0.94 8.99 5.60 5.60
2 29453 3685 306.2 201.4 27.63 5.18 5.33 6.35 5.30
3 4310 2412,5 390.5 30.1 19.05 2.20 8.66 5.67 4.89
4 1117 1606 480.8 29.2 20.04 1.16 17.13 4.80 4.80
5 710 734 126.3 2.48 7.55 0.62 12.05 4.67 4.60
Organogenic mats
6 703 2384 78 2.66 15.55 184 8.45 5.60 5.60
7 270 424 46.9 2.52 11.52 2.16 5.33 5.89 5.43
8 1902 6688,5 207.5 29.6 29.01 4.25 6.82 5.60 4.90
9 172 1058 221.3 17.3 7.26 0.99 7.30 6.00 5.71
Leptosols
10 1321 536 157.2 15.1 5.32 0.29 18.09 6.23 6.20
11 3542 1582.5 1206.8 497.5 0.31 0.03 10.39 4.89 4.10
12 1594 1669 68.9 4.25 4.89 0.79 6.15 5.76 5.71
13 689 1428 227.2 4.43 15.39 0.72 21.13 5.57 5.20
14 4292 5031 662.6 92.5 10.16 0.84 11.98 4.90 4.21
15 2582 842 448.5 322.2 6.66 0.81 8.20 4.70 4.35
Technic Cryosol
16 198 433 9.69 1.37 0.66 0.11 5.74 6.83 5.28
17 277 325 9.57 1.42 0.67 0.05 13.45 6.11 5.37
18 275 344 33.6 2.39 1.02 0.05 17.75 4.67 3.89
19 707 263 121.4 41.6 1.91 0.17 11.02 5.78 5.15
20 719 962 9.51 2.61 0.38 0.03 9.79 5.54 5.21
Results and discussion
Data of total organic carbon and nitrogen content and pH values are provided in Table 2. All soils of the Fildes peninsula investigated in this work are slightly acidic, which corresponds with numerous previous studies (Ta-tur, 2002; Zhu et al., 2009; Pereira et al., 2013). The highest average carbon content was typical for ornithogenic soils. This is caused by the enrichment of terrestrial ecosystems by bird-transported organic matter (Zhu et al., 2009) and intensification of plant growth and production under the influence of increased bulk nitrogen accumulation (Speir and Cowling, 1984). In general, the C/N ratios were higher in Leptosols and Technosols, which indicates lower nitrogen content. In contrast, the C/N ratio was lower in ornithogenic soils and organogenic mats. This il-
lustrates birds' contribution in soil enrichment by mineral forms of nitrogen. The highest content of available nitrogen forms (N-NH4) was typical for Leptosols, but not in ornithogenic soil and organogenic mat. This could be an effect of deeper transformation of nitrogen-containing compounds in case of postornithogenic succession development. The last two soil groups were enriched by bulk nitrogen, but not by available forms of nitrogen ions. Mats are comparable to ornithogenic soils in terms of chemical composition because most mats were previously colonized by birds, mainly by scuas. The content of phosphorus was highest in sample № 2 — ornithogenic soil, situated on marine terrace. Ornithogenic soil, organogenic mats and Leptosols showed increased content of phosphorus in comparison with Technosols. This also could be related to current and previous ornithogenic effect. Previously, pho-
Table 3. Results of post-hoc test (significant values when p<0.05, bolded)
Sample group Р2О5 N-NH4 N-NO3 С N
Ornithogenic soils/Organogenic mats <0.01 <0.06 <0.05 <0.06 <0.04 <0.06
Ornithogenic soils/Leptosols <0.03 <0.07 <0.06 <0.07 <0.05 <0.06
Ornithogenic soils/Technic Cryosol <0.03 <0.07 <0.06 <0.06 <0.01 <0.01
Organogenic mats/Leptosols <0.06 <0.06 <0.05 <0.07 <0.07 <0.06
Organogenic mats/Technic Cryosol <0.01 <0.06 <0.06 <0.09 <0.06 <0.08
Lithosols/Technic Cryosol <0.02 <0.06 <0.02 <0.08 <0.08 <0.09
spatization was considered a key process of ornithogenic soil formation (Tatur and Keck, 1990). This process could be expressed in some cases in the formation of a group of phosphate-containing minerals (Tatur and Barczuk, 1985). Results of the post-hoc test showed (Table 2) that the most pronounced differences between the soil groups were characteristic for phosphorus and total carbon content. Accumulation of these two biogenic elements could occur as a result of ornithogenic accumulation. No evident differences in accumulation of potassium and nitrates were revealed in investigated soils. In contrast, sufficient differences in ammonia ion concentrations were revealed between ornithogenic soils and organogenic mats and pairs of ornithogenic soils and Technosols.
Conclusions
Ornithogenic effect is evident in soil formation in three types of soils investigated. The maximum effect of organic matter transportation and accumulation is pronounced in ornithogenic soils and organogenic mat. Organogenic mats are considered to have been recently colonized by birds; this initiated the formation of organogenic mats due to accumulation of nutrients. Some residual effect of birds can be revealed in Lithosols, where increased content of ammonium ions and available phosphorus was fixed. Technic Cryosol as soils constructed from local mineral grounds show no evidence of ornithogenic accumulation. We suggest that the majority of soils on the Fildes peninsula were recently exposed to ornithogenic effect, which resulted in formation of the modern soil cover of the Fildes peninsula.
Acknowledgements
The author thanks Dr. A. Lupachev for assistance in field research and providing photographs for Fig. 2 (1, 2 and 3).
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