Presence Of Biological Soil Crusts Research Articles

Biological Soil Crusts as Ecosystem Engineers in Antarctic Ecosystem.

Biological soil crusts (BSC) are considered as pivotal ecological elements among different ecosystems of the world. The effects of these BSC at the micro-site scale have been related to the development of diverse plant species that, otherwise, might be strongly limited by the harsh abiotic conditions found in environments with low water availability. Here, we describe for the first time the bacterial composition of BSCs found in the proximities of Admiralty Bay (Maritime Antarctica) through 16S metabarcoding. In addition, we evaluated their effect on soils (nutrient levels, enzymatic activity, and water retention), and on the fitness and performance of Colobanthus quitensis, one of the two native Antarctic vascular plants. This was achieved by comparing the photochemical performance, foliar nutrient, biomass, and reproductive investment between C. quitensis plants growing with or without the influence of BSC. Our results revealed a high diversity of prokaryotes present in these soil communities, although we found differences in terms of their abundances. We also found that the presence of BSCs is linked to a significant increase in soils’ water retention, nutrient levels, and enzymatic activity when comparing with control soils (without BSCs). In the case of C. quitensis, we found that measured ecophysiological performance parameters were significantly higher on plants growing in association with BSCs. Taken together, our results suggest that BSCs in Antarctic soils are playing a key role in various biochemical processes involved in soil development, while also having a positive effect on the accompanying vascular flora. Therefore, BSCs would be effectively acting as ecosystem engineers for the terrestrial Antarctic ecosystem.

Soil nitrogen and climate drive the positive effect of biological soil crusts on soil organic carbon sequestration in drylands: A Meta-analysis

Biological soil crusts (BSCs), known as ecological engineers, play an important role in soil organic carbon (SOC) sequestration in dryland ecosystems. Although numerous individual studies had been conducted, the global patterns of the changes in SOC concentration following BSCs establishment remain unclear. In this study, we performed a comprehensive meta-analysis of 184 independent observations at 47 sites to quantify the responses of SOC and other soil variables to BSCs establishment and identify the underlying mechanisms. Our results showed that BSCs generally increased SOC by 70.9% compared to the controls (uncrusted soil), and the positive effects of BSCs on SOC in deserts (120.3%) were stronger than those in grasslands (32.7%). Mosses and lichens had a stronger positive effect on SOC than algae crusts (67.5%, 82.8%, and 58.2% respectively). Mixed crusts accumulated more SOC (181.6%) than single (moss, lichen and algae) crusts. The presence of BSCs considerably increased total nitrogen (TN) (+80.7%), total phosphorus (TP) (+20.3%), available N (+62.7%), and available P (+14.3%). Significant relationships were observed among the effect size of SOC and climate and soil N and P in both desert and grassland. The random forest analysis showed that TN could be considered as a determinant of the concentration of SOC, followed by climate (P < 0.01). Our study shows that the capacity of the BSCs to fix and store C could be regulated by soil N and P dynamics, indicating a major finding opening new ways to promote soil recovery and formation. Our findings highlight the remarkable contribution of mixed crusts to soil C pools; this contribution needs to be incorporated into regional and global models to predict the effects of human disturbance on drylands worldwide and for assessing the soil C budget.

Contrasting surface soil hydrology regulated by biological and physical soil crusts for patchy grass in the high-altitude alpine steppe ecosystem

How the presence of biological soil crusts (BSCs) and physical soil crusts (PSCs) regulates surface soil hydrological processes in the high-altitude alpine ecosystems is still a pressing scientific issue owing to a lack of convincing field observation data. This study highlights the interesting phenomenon whereby BSCs and PSCs are jointly distributed in opposite orientations under a canopy of patchy Achnatherum splendens grass on the alpine steppe of the Qinghai Lake watershed (Qinghai-Tibet Plateau, northwestern China). The vegetation characteristics (plant species, cover, and biomass) and soil properties (volumetric soil water content, hydraulic conductivity, temperature, salinity, and macroporosity) were investigated for BSCs zones, PSCs zones, and interpatch zones (IPZs) in the A. splendens patches (ASPs) system. The experimental results show that BSCs increased infiltration during wet periods by increasing significantly greater hydraulic conductivity and macroporosity (p < 0.01), and reduced soil evaporation by maintaining a lower soil temperature than PSCs and IPZs during dry periods. BSCs had an important role in improving water retention in ASPs and thereby provided highly favorable conditions for plant recruitment and survival. However, PSCs reduced the infiltration capacity of surface soils and were suspected of generating runoff after intense rainfall events, which might promote connectivity of the horizontal water flux for ASPs. PSCs had a negative effect on the vegetation community by creating a saline environment (e.g. 28-fold higher salinity than for BSC zones and IPZs at 5 cm depth) for other herbaceous plants. The predominant wind direction, canopy effects of A. splendens on local microclimate, and salt accumulation were identified as the main factors determining the opposite distribution of BSCs and PSCs. The results suggest that BSCs and PSCs play contrasting roles in soil hydrology in ASPs, and provide valuable insights for understanding the spatial distribution of soil crusts and vascular plants as well as their interactions in high-altitude alpine steppe ecosystems.

Effect of biological soil crusts on seed germination and growth of an exotic and two native plant species in an arid ecosystem.

Biological soil crusts (BSCs) can improve the stability and health of native plant communities in arid ecosystems. However, it is unknown whether BSCs can also inhibit invasions of exotic vascular plants on stabilized reclaimed sand dunes. To answer this question, we conducted a greenhouse experiment to test the effects of cyanobacteria-dominated BSCs on 1) seed germination and biomass of an exotic grass (Stipa glareosa P. Smirn.), and 2) individual biomass of the exotic S. glareosa growing with two native plants, Eragrostis poaeoides Beauv. and Artemisia capillaris Thunb. Our experiment included three BSC treatments (intact crust, disturbed crust, and bare soil) and five species trials (native E. poaeoides alone, E. poaeoides mixed with exotic S. glareosa, native A. capillaris alone, A. capillaris mixed with exotic S. glareosa, and S. glareosa alone). The results showed that cyanobacteria-dominated crusts can significantly reduce the cumulative percent germination of the exotic grass (P<0.001) and native plants (P<0.001). Maximum cumulative percent germinations of the exotic grass and two native plants were found in bare soil, and minimum in intact crusts. The interaction of crust treatment × species trials on shoot biomass of the two native plants was significant (P<0.05). These results indicate that the presence of BSCs on stabilized sand dunes may reduce the germination of the exotic and two native plants. The effect of reducing exotic and native plant seeds germination would maintain more diverse plant communities and contribute to the formation of clumped vegetation patterns. We conclude that BSCs act as a natural regulator for vegetation patterns and thus promote ecosystem stability and sustainability.

Biological soil crust in Peru: first record and description

The presence of biological soil crusts in the Andean and coastal regions is reported for the first time in Peru. Crusts dominated by cyanobacteria, lichens and/or mosses are described from localities in the coastal desert (Lomas) and in the high Andean region (Puna).

Monitoring and behavior of unsaturated volcanic pyroclastic in the Metropolitan Area of San Salvador, El Salvador.

Field monitoring and laboratory results are presented for an unsaturated volcanic pyroclastic. The pyroclastic belongs to the latest plinian eruption of the Ilopango Caldera in the Metropolitan Area of San Salvador, and is constantly affected by intense erosion, collapse, slab failure, sand/silt/debris flowslide and debris avalanche during the rainy season or earthquakes. Being the flowslides more common but with smaller volume. During the research, preliminary results of rain threshold were obtained of flowslides, this was recorded with the TMS3 (a moisture sensor device using time domain transmission) installed in some slopes. TMS3 has been used before in biology, ecology and soil sciences, and for the first time was used for engineering geology in this research. This device uses electromagnetic waves to obtain moisture content of the soil and a calibration curve is necessary. With the behavior observed during this project is possible to conclude that not only climatic factors as rain quantity, temperature and evaporation are important into landslide susceptibility but also information of suction–moisture content, seepage, topography, weathering, ground deformation, vibrations, cracks, vegetation/roots and the presence of crust covering the surface are necessary to research in each site. Results of the field monitoring indicates that the presence of biological soil crusts a complex mosaic of soil, green algae, lichens, mosses, micro-fungi, cyanobacteria and other bacteria covering the slopes surface can protect somehow the steep slopes reducing the runoff process and mass wasting processes. The results obtained during the assessment will help explaining the mass wasting problems occurring in some pyroclastic soils and its possible use in mitigation works and early warning system.

Effect of biological soil crusts on the germination of three plant species under laboratory conditions

Semiarid grasslands in northeastern Mexico contain many endemic plants and animals and are an important refuge for resident and migratory animals. Here, as in many other semiarid areas, biological soil crusts are a key component of the ecosystem. However, findings about their effect on the germination of vascular plants are in contrast. We asked whether germination of some native plant species would be inhibited by the presence of biological soil crusts as it has been found in other studies and evaluated the effect of seven dominant biological soil crusts: Psora cerebriforme (W.A.Weber), Psora decipiens (Hedwig) Hoffm., Placidium sp., Endocarpom pussillum (Hedwig), Xanthoparmelia chlorochroa (Tuck.) Hale, Nostoc commune (Vauch), and Oxymitra sp. from the area, on the germination percentage and germination rate of three native plant species: Frankenia gypsophila (I.M.Johnst.), Muhlenbergia arenicola (Buckl.), and Sartwellia mexicana (A.Gray). Germination tests were carried out in an environmental chamber at 26 °C and at a constant humidity of 60% with 12 hours by 12 hours light and darkness. Biological soil crusts did not affect germination percentage of the three evaluated plant species when compared to bare soil. Germination rate ranged between 3.5 and 5 days and there were no differences between substrates.

生物土壤结皮对荒漠土壤线虫群落的影响

Biological soil crusts(BSCs) play an important role in dune fixation and maintaining soil biota in arid desert ecosystems.Soil nematodes can be used as significant bio-indicators to reflect soil recovery regimes and important biological properties in studies of the restoration and health of sandy ecological areas.However,the relationship between BSCs and nematodes is currently poorly understood.To understand how BSCs affect soil nematodes,sand dune soils under algal and moss crusts were investigated in an artificially revegetated desert area at the southeastern edge of the Tengger Desert,China.Sample plots were selected in four areas that had undergone different periods of sand-fixing(the sand dunes were stabilized in 1956,1964,1981 and 1991,respectively).Mobile sand dunes were used as the control.Soil samples from different soil layers(0—10,10—20 and 20—30 cm,respectively) under algal and moss crusts were collected in different months(4,7,9 and 12,respectively) to analyze the temporal and spatial variation of soil nematodes in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.Natural vegetation areas at Hongwei in the Shapotou area were used as the control.Soil nematodes were separated using the improved Baermann funnel method and were identified and counted by an optical microscope.Our results showed that algal and moss crusts could significantly enhance nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index in the sand dunes,artificially stabilized in 1956,1964,1981 and 1991,respectively(P0.05).This can be attributed to the presence of BSCs providing an essential food source and the creation of suitable habitats for soil nematodes.The time of sand dune fixation was positively correlated with soil nematode abundances,generic richness,Shannon-Weaver index,enrichment index and structure index under crusts(P0.05).This result suggested that long periods of sand dune fixation were more beneficial to the survival and reproduction of soil nematodes than short periods of sand dune fixation.Crust type significantly affected soil nematode communities,with moss crusts having higher nematode abundances and generic richness than those of algal crusts.This result suggested that the late-successional moss crusts were more beneficial to the survival and reproduction of soil nematodes than the early-successional algal crusts.In addition,algal and moss crusts significantly increased soil nematode abundances and generic richness in the 0—10,10—20 and 20—30 cm soil layers.However,the effect gradually decreased with increasing soil depth,which demonstrated that BSCs were more beneficial to the survival of soil nematodes in topsoil than in subsoil.There were also seasonal changes of nematode abundances under algal and moss crusts,in the following order: autumn summer spring winter.Seasonal changes could reflect changes in the biomass,cover and species composition of BSCs with season changes.Therefore,the presence and succession of BSCs were beneficial to the survival and reproduction of soil nematodes,which increased their amount,species and diversity.The results indicate that BSCs could improve the recovery of soil and corresponding ecological systems in the artificially revegetated desert areas at the southeastern edge of the Tengger Desert.

Surrogate descriptors of C-storage processes on crusted semiarid ecosystems

Arid and semiarid crusted ecosystems occupy a large extent of the Earth's surface. In these ecosystems there is a delicate balance between C sequestration and biodegradation that could easily be altered due to human disturbance or global warming. These environments are characterized by the presence of biological soil crusts (BSCs) coexisting with shrubs in the interspaces. BSCs play an important role in the C-cycle in arid and semiarid areas, but there has been little research regarding C-storage in crusted soils. In this research, representative BSCs were studied in three different crusted semiarid ecosystems in Southern Spain. Chemical fractionation and characterization of the organic matter in BSCs and underlying soils were undertaken to compare the total amount and quality of humic substances and find surrogate indicators of the soil organic matter quality. After isolating the major organic fractions (particulate fraction, humic acid-like (HA) and fulvic acid (FA)), the macromolecular, HA fraction was studied by derivative visible spectroscopy and resolution-enhanced infrared (IR) spectroscopy. Our results show quantitative differences in organic matter fractions, in agreement with the structural characteristics of the HA-type substances. The more stable crusted ecosystem with more evolved vegetation cover tend to be associated with HAs with broadband IR profiles, high optical density and macromolecular condensation and presence of polycyclic fungal biomarker compounds. In contrast, in the crusted ecosystem with very low or almost absent vascular vegetation cover, the C sequestration depends almost exclusively on the activity of crust-inhabiting organisms. It is suggested that the organic matter in BSCs shares characteristics with aquatic humic matter derived from non-lignified plants, including structurally complex HA-type substances which may have been originated by abiotic condensation of unsaturated lipids and/or diagenetic alteration of aliphatic biomacromolecules. Although these humification mechanisms have not been extensively studied in terrestrial soils they may be very active mechanisms for C sequestration in some types of crusted ecosystems. In particular, the spectroscopic characteristics in the visible and IR ranges of the crust-isolated HA-type substances provide the above-indicated biogeochemical proxies informing on the organic matter stability and quality and their bearing on the potential of crusted ecosystems for maintaining their properties after external disturbance.

Dew formation characteristics in a revegetation-stabilized desert ecosystem in Shapotou area, Northern China

Soil moisture in the upper layer plays an important role in arid desert ecosystems. Dew as an additional source of fresh water, may have a positive impact upon the ecosystems in arid and semi-arid zones. Measurements on dew formation amount and duration were carried out in the whole October of 2008 at different condensing surface types (bare dune sands, physical soil crusts and biological soil crusts) associated with different inter-space positions between plants, and at the area under plant canopy in a revegetation-stabilized arid desert ecosystem in Shapotou area, China. The results indicated that there was a positive linear correlation between dew amounts and relative humidity, while mean temperature was negatively linearly related to dew amounts and no significant relationship was found between dew amounts and wind speed. Clear and foggy mornings were characterized by higher dew amounts and longer dew duration, whereas less dew was recorded during cloudy and especially windy mornings. Crusts, especially the biological soil crusts, obtained significantly higher amounts of dew than that of bare moving sand dunes. It was more difficult for dew to condense under the canopy of the plants than on the bare sand dunes. At the first stage of ecological engineering projects, dew can renew the moisture losing through the evaporation of soil and transpiration of leaves, and thus can supply important source of water for xerophytic shrubs. The higher dew amount at the inter-space of re-vegetated plants is an important driving factor for the growth of microorganisms and spore plants, which further accelerate the formation of biological soil crusts and stabilization of moving sand dunes. The presence of biological soil crusts, in turn, helps to facilitate the formation of dew. Therefore, a mutual enhanced effect exists between dew and artificially revegetation ecosystems.

Characteristics and numeric simulation of soil evaporation in biological soil crusts

It is commonly believed that biological soil crusts may affect soil evaporation rates and consequently relieve or aggravate the shortage of soil water in arid and semiarid regions. However, the effects and mechanisms are largely unclear. In the “wind–water erosion crisscross” region on the Loess Plateau of China (so called because suffering serious water erosion in summer and serious wind erosion in winter) biologically crusted and uncrusted sandy and sand loam soils were sampled and then evaporation processes were measured in sunlight using micro-lysimeters. The results indicated: (1) The evaporation rate of biologically crusted soils was significantly ( P < 0.01) decreasing at the beginning of evaporation process and thereafter it was constantly high for a long time. (2) The evaporation process of sandy soil was significantly ( P < 0.03) affected by biological soil crusts, while that of sand loam soil was not significantly ( P > 0.06) affected. This implied that the effects of biological soil crusts on evaporation were dependent on soil properties (mainly soil texture). (3) The evaporation rates of biologically crusted and uncrusted soil can be described by numeric functions ( R > 0.88). As a whole, the amount of evaporation was slightly higher on sandy soils and lower on sand loam soils when biological soil crusts were present. It can be concluded that the presence of biological soil crusts would not greatly change soil evaporation in arid and semiarid environments due to the initially decreasing action, balanced by a final increasing effect.

Effects of Biological Soil Crust on Desert Insect Diversity: Evidence from the Tengger Desert of Northern China

Biological soil crusts are widespread in arid and semiarid regions. They are one of the major components of desert ecosystems, and their importance has been demonstrated by numerous researchers. However, little research has been carried out on the relationship between biological soil crusts and the diversity of desert insects. In this study, psammophilous Caragana korshinskii-Artemisia ordosica communities occurring on semifixed dunes and fixed dunes in the Shapotou region at the southeastern fringe of the Tengger desert are investigated. Observation sample plots and the survey quadrats were arranged in the vegetation areas with different types and coverage of biological soil crusts. The insects were surveyed in 10 m × 10 m quadrats and caught by a sampling frame and net-trap methods. The insect number was recorded and samples were collected for identification. The results show that as compared to the un-crusted vegetation area, the presence of biological soil crusts in the Tengger desert significantly increases the diversity and abundance of insect species. Diversity and abundance in the quadrats mainly covered by moss and lichen crusts are significantly higher than those in the quadrats mainly covered by cyanobacteria and algal crusts. The contribution of biological soil crusts to the diversity of insect species may be attributed to the stabilized soil surface providing suitable habitats and some food sources for the insects.

Effects of Biological Soil Crusts on Seed Bank, Germination and Establishment of Two Annual Plant Species in the Tengger Desert (N China)

The presence of biological soil crusts can affect the germination and survival of vascular plants, but the reasons are not well investigated. We have conducted a field investigation and greenhouse experiments to test the effect of crusts on two desert annual plants, which occur on the stabilized dunes of the Tengger Desert in N China. The results showed that biological soil crusts negatively influenced the seed bank of Eragrostis poaeoides and Bassia dasyphylla. The important effect of biological soil crusts on seed germination and establishment were performed indirectly through reducing the amount of germinating seeds. Field investigation and experimental results with regard to the seed bank indicated that higher seedling density was found in disturbed crust soil and bare soil surface than in intact crust soils. Greenhouse experiments showed that the effects of biological soil crusts on germination and establishment of the two plants are not obvious in moist condition, while disturbed crusts are more favorable to seed germination in dry treatment. Significant differences in biomass were found between disturbed crust soil and bare soil. Survival and growth of the two annual plants were enhanced in both algal and moss crusts during the season of rainfall or in moist environment, but crusts did not affect seedling survival in the dry period. The small seeded E. poaeoides has higher germination than larger-seeded B. dasyphylla in crust soils, but B. dasyphylla has a relatively higher survival rate than E. poaeoides in crust soils.

Soil and Plant Recovery After Historic Military Disturbances in the Sonoran Desert,USA

Military training exercises in desert areas have resulted in various types of disturbance through time. Camp Laguna, located on the U.S. Army Yuma Proving Ground in southwestern Arizona, served as a military base camp during World War II. The camp exhibits a variety of historic disturbances, including vehicle traffic (motor pool) and foot traffic (tent rows, commons, and footpaths). The extent of soil and plant recovery that has occurred at Camp Laguna in the 56 years since abandonment was assessed by comparing sites with historic disturbance to an apparently undisturbed control site. Vegetative recovery was determined by measuring perennial plant foliar cover and density. Soil was characterized by maximum penetration depth measurements and presence of biological soil crusts. Soil samples were collected and analyzed for inorganic and organic carbon and total nitrogen content. The tent city, disturbed primarily by foot traffic, did not show full recovery of vegetation and biological soil crust to predisturbance conditions. The slow recovery may be attributable to grading that removed topsoil and seed sources when the camp was established. In contrast, most plant species at the motor pool exhibited higher density and greater foliar cover than was found at the control site. This may be the result of a compacted soil layer that enhanced soil-water relations of the upper horizon of the sandy soil and provided fine plant roots with a greater amount of moisture.