Start at the point zero - biocrusts in initial ecosystems 

In 2007 the German–Swiss Transregional Collaborative Research Centre (SFB/TRR 38) ‘‘Structures and processes of the initial ecosystem development phase in an artificial water catchment’’ was launched as a collaboration of the Brandenburg University of Technology, Cottbus (BTU), the Technische Universität München (TUM) and the Swiss Federal Institute of Technology Zurich (ETH). The overall objective of this interdisciplinary project is to elucidate the role of structures and processes during the initial establishment of an ecosystem. The central hypothesis of the project assumes that initial patterns substantially define and shape the development and later stages of an ecosystem. In this context, we studied the importances of biocrusts in early successional stages of ecosystem developments.

  • Carbon cycling of biological soil crusts mirrors ecological maturity along a Central European inland dune catena
crust (8)

Photosynthesis and respiration of biological soil crusts (BSCs) sampled along a mobile inland dune catena were determined to evaluate the applicability of Odum’s P/R ratio, determined under controlled conditions, for estimation of ecosystem maturity. The theory is that in the early stages of ecological succession, the total photosynthesis (P) exceeds the rate of community respiration (R), so that the P/R ratio is greater than 1, and that P/R approaches 1 as succession occurs. In the special case of organic pollution, the P/R ratio is typically less than 1. Samples were collected in the deflation zone of the dune near the crest (BSC1, thickness 2-3 mm), at the lee side of grass tussocks at the slope (BSC2, thickness 2-4 mm) and near the base (BSC3, thickness 4-6 mm). Non crusted sand was used as control (BSC0). Photosynthesis, respiration, crust biomass, as well as fossil and inherited pedogenic carbon entering the system with mineral substrate were determined. The respiration of the BSC1 was dominated by the degradation of inherited organic matter, leading to a diminished P/R ratio. The better developed BSC2 and BSC3 were less influenced by inherited organic matter, where BSC maturity increased downslope with biomass increase. Crust carbon pools increased and flows intensified, but mineralization constants decreased with system maturation. It was concluded that Odum’s P/R ratio and accumulation of recalcitrant to biodegradation organic matter are indicative for biocrust maturity.

Fischer, T., Veste, M. (2017) Carbon cycling of biological soil crusts mirrors ecologgical maturity along a Central European inland dune catena. Catena. 

  • Photosynthetic characteristics and their spatial variance on biological soil crusts covering initial soils of post-mining sites in Lower Lusatia, NE Germany

Following surface disturbance, quaternary sands are the basic substrate for soil development in the Lusatian reclamation area. These substrates mostly contain low organic matter and, hence, are nutrient poor. Accumulation of soil carbon is an important factor for ecosystem development, where biological soil crusts initially influence soil processes and promote ecosystem succession. The compositional structures of biological soil crusts at various developmental stages and their photosynthetic properties were investigated on two former open-cast lignite sites, currently under reclamation, an artificial sand dune in Welzow Süd, and a forest plantation in Schlabendorf Süd (Brandenburg, Germany). As development of biological soil crusts progressed, their contents of organic carbon and total chlorophyll increased. The ratio of these parameters, however, varied with the relative contribution of lichens and mosses in particular. Also maximum photochemical efficiency, net photosynthesis and respiration increased with crustal development. An additional evaluation of NDVI and chlorophyll fluorescence images showed that especially moss-dominated biocrusts had higher photosynthetic capacity compared to green algae-dominated biocrusts or soil lichens, so the photosynthetic capacity showed to be highly species-specific. The ratio of gross photosynthesis to respiration indicated a higher ecological efficiency of biocrusts dominated by green algae than of biocrusts. The occurrence of soil lichens reduced net CO2 fixation and increased CO2 release due to the enhanced mycobiontic respiration. During crustal succession, the rise of photosynthesis-related parameters is not necessarily linear as a result of the highly heterogenic distribution of the different crustal organisms between biocrusts of similar developmental stages as well as between those growing at the two study sites. Therefore, the evaluation of relevant ecophysiological parameters highlighted that not all biocrust-forming organisms similarly contribute to the ecophysiological behavior of biological soil crusts. Nevertheless, the occurrence of the biological soil crusts promoted soil formation and accumulation of soil carbon in initial soils.

Gypser, S, Herppich, W.B., Fischer, T., Lange, P., Veste, M. (2016): Photosynthetic characteristics and their spatial variance on biological soil crusts covering initial soils of post-mining sites in Lower Lusatia, NE Germany. Flora 220: 103-116.

  • Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany

Investigations were done on two former open-cast lignite mining sites under reclamation, an artificial sand dune in Welzow Süd, and a forest plantation in Schlabendorf Süd (Brandenburg, Germany). The aim was to associate the topsoil hydrological characteristics of green algae dominated as well as moss and soil lichen dominated biological soil crusts during crustal succession with their water retention and the repellency index on sandy soils under temperate climate and different reliefs. The investigation of the repellency index showed on the one hand an increase due to the cross-linking of sand particles by green algae which resulted in clogging of pores. On the other hand, the occurrence of moss plants led to a decrease of the repellency index due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The pore-related van Genuchten parameter indicates a clay-like behaviour of the developed soil crusts. Because of the inhomogeneous distribution of lichens and mosses as well as the varying thickness of green algae layers, the water retention differed between the study sites and between samples of similar developmental stages. However, similar tendencies of water retention and water repellency related to the soil crust formation were observed. Biological soil crusts should be attended after disturbances in the context of reclamation measures, because of their small-scale succession and, hence, the promotion of soil and ecosystem development.

Gypser, S., Veste, M., Fischer, T., Lange, P.  (2016): Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany. Journal of Hydrology and Hydromechanics 64 (1): 1-11.

  • Formation of soil lichen crusts at reclaimed post-mining sites, Lower Lusatia, North-east Germany
crust (7)

Biological soil crusts were investigated at reclaimed post-mining sites near Welzow and Schlabendorf in Lower Lusatia (Brandenburg, Germany). Various development stages from initial biological soil crusts built up by green algae, to more developed soil crusts with mosses, as well as moss-soil lichen crusts, were classified. The spatial-temporal dynamics during the development resulted in a moss-lichens cover with discrete patches of pioneer organisms like green algae in between. At the study sites, 13 species of terricolous lichens were identified. The formation of the biological soil crust is important for the accumulation of soil organic matter in the first millimeters of the topsoil of these pioneer ecosystems. A correlation between cryptogamic biomass and soil carbon content were found.

Gypser, S., Veste, M., Fischer, T., Lange, P. (2015): Formation of soil lichens crusts at reclaimed post-mining sites, Lower Lusatia, North-east Germany.  Graphis Scripta 27 (1–2): 3-14.

  • Synergic hydraulic and nutritional feedback mechanisms control surface patchiness of biological soil crusts on tertiary sands at a post-mining site 
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In a recultivation area located in Brandenburg, Germany, five types of biocrusts (initial BSC1, developed BSC2 and BSC3, mosses, lichens) and non-crusted mineral substrate were sampled on tertiary sand deposited in 1985 – 1986 to investigate hydrologic interactions between crust patches. Crust biomass was lowest in the non-crusted substrate, increased to the initial BSC1 and peaked in the developed BSC2, BSC3, the lichens and the mosses. Water infiltration was highest on the substrate, and decreased to BSC2, BSC1 and BSC3. Non-metric multidimensional scaling revealed that the lichens and BSC3 were associated with water soluble nutrients and with pyrite weathering products, thus representing a high nutrient low hydraulic feedback mode. The mosses and BSC2 represented a low nutrient high hydraulic feedback mode. These feedback mechanisms were considered as synergic, consisting of run-off generating (low hydraulic) and run-on receiving  (high hydraulic) BSC patches. Three scenarios for BSC succession were proposed. (1) Initial BSCs sealed the surface until they reached a successional stage (represented by BSC1) from which the development into either of the feedback modes was triggered, (2) initial heterogeneities of the mineral substrate controlled the development of the feedback mode, and (3) complex interactions between lichens and mosses occurred at later stages of system development. 

Fischer, T., Gypser, S., Subbotina, M., Veste, M., Journal of Hydrology and Hydromechanics, 2014

  • Organic matter from biological soil crusts induces the initial formation of sandy temperate soils

Different development stages of algae-dominated and moss-dominated biological soil crusts (BSCs) were sampled on a natural sand dune (< 17 years old) and on an experimental sand dune (< 8 years old) along a catena, including gradients of vegetation cover, location on the slope, as well as composition and thickness of BSC organisms in northeastern Germany. The accumulation of BSC-derived organic carbon (OC) was determined for bulk materials and fractions less than 63 μm. The OC composition was characterized by solid-state 13C NMR spectroscopy and the carbohydrate-C signature. 14C contents were determined to assess the origin and dynamics of OC. From the radiocarbon contents, two OC pools were differentiated: recent BSC-derived and lignite-derived “old” OC. Downward movement of OC into the underlying substrate was found only under moss-dominated BSCs at the old sand dune. BSC-derived OC was mainly composed of carbohydrate-C and, to a lesser extent, alkyl C and N-alkyl C, with considerably higher contributions of alkyl C in the young dune, indicating differences in the composition of extracellular polymeric substances produced by the BSCs with age. This is consistent with higher proportions of water-soluble OC of moss-dominated BSCs at the old dune, which is leached in the underlying substrate and initiates soil formation. Because of the channeling effect of mosses, OC depth translocation along with suspended colloidal substances may contribute to OC accumulation in substrates.

Dümig, A., Veste, M., Hagedorn, F., Fischer, T., Lange, P., Spröte, R., Kögel-Knabner, I., Catena 122, 196–208, 2014 (more..)

  • Succession of N cycling processes in biological soil crusts on a central European inland dune. 
crust (1)

Biological soil crusts (BSCs) are microbial assemblages that occur worldwide and facilitate ecosystem development by nitrogen (N) and carbon accumulation. N turnover within BSC ecosystems has been intensively studied in the past; however, shifts in the N cycle during BSC development have not been previously investigated. Our aim was to characterise N cycle development first by the abundance of the corresponding functional genes (in brackets) and second by potential enzyme activities; we focussed on the four processes: N fixation (nifH), mineralisation as proteolysis and chitinolysis (chiA), nitrification (amoA) and denitrification (nosZ). We sampled from four phases of BSC development and from a reference located in the rooting zone of Corynephorus canescens, on an inland dune in Germany. BSC development was associated with increasing amounts of chlorophyll, organic carbon and N. Potential activities increased and were highest in developed BSCs. Similarly, the abundance of functional genes increased. We propose and discuss three stages of N process succession. First, the heterotrophic stage (mobile sand without BSCs) is dominated by mineralisation activity. Second, during the transition stage (initial BSCs), N accumulates, and potential nitrification and denitrification activity increases. Third, the developed stage (established BSCs and reference) is characterised by the dominance of nitrification.

Brankatschk, R., Fischer, T., Veste, M., Zeyer, J. FEMS Microbiology Ecology 83 (1),149-160, 2013. (more…)

  • Hydraulic properties of biological soil crusts on sand dunes studied by 13C-CP/MAS-NMR: A comparison between an arid and a temperate site
crust (9)

Using principal component analysis (PCA), we studied the relationships between hydraulic properties and 13C-CP/MAS-NMR shift regions of biological soil crusts (BSCs) on sand dunes under arid and temperate con- ditions. The arid study site was located near Nizzana, in the northwestern Negev, Israel and the temperate site was near Lieberose, Brandenburg, Germany. BSCs were sampled at each site near the dune crest, at the center of the dune slope and at the dune base. The soil texture was finer and water holding capacities (WHCs) were higher in Nizzana, whereas surface wettability was reduced in Lieberose. At both sites, BSCs caused extra WHC compared to the mineral substrate. Infiltration after wetting along both catenas generally reached a maximum after 10 min and decreased after 30 min. Carbohydrates were the dominating components in all of the BSCs studied, where the relative peak areas of carbohydrate-derived structures (60–110 ppm) amounted to 28–46% and to 10–14% of total C-peak areas, respectively. PCA revealed that the WHC of the sub- strate was closely related to the amount of silt and clay, whereas the BSC induced extra WHC was closely related to carbohydrates. It was further found that water repellency was positively related to carbohydrate C, but nega- tively related to alkyl C. Infiltration kinetics was attributed to polysaccharide hydration and swelling. Our find- ings support the hypothesis that hydraulic properties of BSCs are determined by extracellular polymeric substances (EPS) and soil texture. Hydraulic properties in BSCs result from the combination of chemical proper- ties related to C compounds mainly dominated by carbohydrates and physical surface properties related to texture, porosity and water holding capacity.

Fischer, T., Yair, A., Veste, M., Geppert, H. (2013): 13C-CP/MAS-NMR as related to hydraulic properties of biological soil crusts on  sand dunes: a comparision between an arid and a temperate site. Catena 110: 155-160. 

  • Water repellency and pore clogging at early successional stages of microbiotic crusts on inland dunes, Brandenburg, NE Germany
BSS lieb

Biological soil crusts play a key role for hydrological processes in many open landscapes. They seal the topsoil and generate surface run-off. Utilization of the mineral substrate at early stages of microbiotic crusts was investigated using scanning electron microscopy (SEM), water repellency indices were measured using the ethanol/water microinfiltrometer method, and steady state water flow was determined on the dry crusts and after 300, 600, 1200 and 1800 s of wetting, thus allowing to follow pore clogging through swelling of extracellular polymeric substances (EPS). It was found that water repellency increases with initial crust development where filamentous cyanobacteria and filamentous green algae were dominating, but decreases as coccal algae, bryophytes and fungi associated with bryophytes emerged. Swelling of EPS took place immediately after wetting, and its influence on steady state water flow was most pronounced when filamentous cyanobacteria and algae partially filled in the matrix pores and enmeshed sand grains, still leaving micropore channels available for free water infiltration, but prior to appearance of coccal algae, bryophytes and associated fungi which formed a dense cover on the surface. It was concluded that a new phase of crust succession was accompanied by easier wettability but slower infiltration. Transition from hydrophobicity to pore clogging as ruling mechanisms causing water run-off may occur during wetting of individual biological crusts, but also during crust succession over time.

Fischer, Veste, M., Wiehe, W., Lange, P., Catena 80 (1), 47-52, 2010. (more…)

  • Microstructure and hydraulic properties of biological soil crusts on sand dunes: a comparison between arid and temperate climates
crust (5)

We studied the relationships between crust microstructure, infiltration and water holding capacity under arid and temperate conditions (Factor A: Climate) on biological soil crusts (BSCs) sampled along a~catena on mobile sand dunes (Factor B: Catena). The arid study site was located near Nizzana, Israel (precipitation: 86 mm a−1, PET: ~2500 mm a−1) and the temperate site near Lieberose, Germany (precipitation: 569 mm a−1, PET: ~780 mm a−1). BSCs were sampled near the dune crest, at the centre of the dune slope and at the dune base at each site. Scanning electron microscopy (SEM) was used to characterize BSC morphology and microstructure. Infiltration was determined using microinfiltrometry under controlled moisture conditions in the lab. Water holding capacities were determined after water saturation of the dry BSCs. Wettability of the crusts was characterized using a "repellency index", which was calculated from water and ethanol sorptivities. Irrespective of the climate, an accumulation of fine particles in the BSCs was found, increasing along the catena from dune crest to dune base. Texture was finer and water holding capacities of the underlying substrate were higher at the arid site, whereas surface wettability was reduced at the temperate site. At both sites, BSCs caused extra water holding capacity compared to the substrate. Infiltration rates decreased along the catena and were generally lower at the dune slope and base of the arid site. A mechanism of crust stabilization is proposed where BSCs benefit from increased texture and biomass mediated water supply, and where the water supply to higher plants was limited due to alteration of physico-chemical surface properties under temperate conditions.

Fischer, T., Yair, A., Veste, M.,  Biogeosciences Discuss., 9, 12711-12734, 2012. (more…)

  • Biological topsoil crusts at early successional stages on Quaternary substrates dumped by mining in Brandenburg, NE Germany
crust (2)

The influence of biological soil crusts in natural ecosystems on structures and processes is well investigated. However, in South-Brandenburg (Germany), it is possible to study the development of biological soil crusts (BSC) during initial ecosystem genesis on two artificial water catchments with well-known ages and under differing starting conditions. The two experimental sites are located in the recultivation area of the lignite open-cast mining district of southern Brandenburg with a distance of approximately 1 km between them. Two different topographies were constructed at the experimental sites: the experimental plot at the catchment Neuer Lugteich was shaped like a dune, whereas the artificial water catchment Hühnerwasser was modelled as an inclined slope. The catchment Neuer Lugteich is four years older than Hühnerwasser. The original substrate at Neuer Lugteich is more sandy and carbonate-free compared to the original substrate dumped at Hühnerwasser. At both sites geomorphological differentiation and crust development were compared and the importance of substrate-dependent water availability and crust type clarified. Once settled, the crusts influenced the water regime of the soils by delaying infiltration through enhanced water repellency, and by limiting water infiltration. Chlorophyll analysis revealed that all crusts were at early stages of development. At Neuer Lugteich, the establishment of the biological soil crusts was closely associated with the vegetation succession, whereas no clear succession of the crusts could be observed at Hühnerwasser. The mosaic-like pattern of the biological soils crusts is associated with the distribution of fine-grained material here.

Spröte, R.,Fischer, T., Veste, M., Raab, T., Wiehe, W., Lange, P., Bens, O., Hüttl, R.F.,Géomorphologie: relief, processus, environnement 4/2010: 359-370. (more…)

  • Initial pedogenesis in a topsoil crust 3 years after construction of an artificial catchment in Brandenburg, NE Germany
crust (3)

Cyanobacteria and green algae present in biological soil crusts are able to colonize mineral substrates even under extreme environmental conditions. As pioneer organisms, they play a key role during the first phases of habitat colonization. A characteristic crust was sampled 3 years after installation of the artificial water catchment “Chicken creek”, thus representing an early successional stage of ecosystem development. Mean annual rainfall and temperature were 559 mm and 9.3°C, respectively. We combined scanning electron microscopy (SEM/EDX) and infrared (FTIR) microscopy to study the contact zone of algal and cyanobacterial mucilage with soil minerals in an undisturbed biological soil crust and in the subjacent sandy substrate. The crust was characterized by an approximately 50 μm thick surface layer, where microorganisms resided and where mineral deposition was trapped, and by an approximately 2.5 mm thick lower crust where mineral particles were stabilized by organo-mineral structures. SEM/EDX microscopy was used to determine the spatial distribution of elements, organic compounds and minerals were identified using FTIR microscopy and X-ray diffraction (XRD). The concentration of organic carbon in the crust was about twice as much as in the parent material. Depletion of Fe, Al and Mn in the lower crust and in the subjacent 5 mm compared to the geological substrate was observed. This could be interpreted as the initial phase of podzolization. Existence of bridging structures between mineral particles of the lower crust, containing phyllosilicates, Fe compounds and organic matter (OM), may indicate the formation of organo-mineral associations. pH decreased from 8.1 in the original substrate to 5.1 on the crust surface 3 years after construction, pointing to rapid weathering of carbonates. Weathering of silicates could not be detected.

Fischer, T., Veste, M., Schaaf, W., Bens, O., Dümig, A., Kögel-Knabner, I, Wiehe, W.,  Hüttl, R.F., Biogeochemistry 101, 165-176, 2010. (more…)

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