Microbiotic Crusts Research Articles

Response of Antelope Bitterbrush Shrubsteppe to Variation in Livestock Grazing

Abstract Shrubsteppe ecosystems in the Intermountain West have suffered extreme alteration from a variety of factors. Using a retrospective approach, I studied the effects of horse and cattle grazing at the northern edge of the range in southern British Columbia, Canada, where the shrubsteppe is not as heavily altered and ungrazed sites remain in areas dominated by antelope bitterbrush (Purshia tridentata). I measured shrub and understory cover at 10 sites that were either ungrazed, lightly grazed, or heavily grazed. Cover of antelope bitterbrush decreased with grazing, and cover of big sagebrush (Artemisia tridentata) increased with grazing intensity. I sampled 72 species of vascular plants in the understory. Livestock grazing resulted in more bare soil, especially at sandy rather than rocky sites, and in quadrats located in the interspaces between shrubs. More bare soil was associated with less spikemoss (Selaginella spp.) and less microbiotic crust cover. Of the 3 most common bunchgrasses, sand dropsee...

Factors affecting distribution of microbiotic crusts in the grain-for-green land of the loess region, northern Shaanxi, China

A field survey was conducted in the grain-forgreen land of the loess region, northern Shaanxi, China, from July to August of 2005 to provide a scientific evaluation of the grain-for-green project, including its soil and water conservation and other ecological benefits for the region. The distribution of microbiotic crusts were studied, while human disturbance, aspect, topography, vegetation structure and other factors affecting it were obtained from the analysis of survey data from 78 sample plots. Results show that crust coverage is larger on less-disturbed plots than on highly-disturbed ones, on north-facing plots than on south-facing ones and on gully-slopes than on ridge-slopes. Coverage increases with herbal coverage and trees can provide better conditions for distribution of crusts than shrubs. Therefore, crust coverage is larger in herb-dominated plots than in tree-dominated ones and crusts in shrub-dominated plots are smaller. However, we made no progress in our study on deciding how slope degrees and herb species affect the distribution of crusts. We believe that more studies are necessary for a further exploration of the relationship between them.

Recovery rates of microbiotic crusts within a dune ecosystem in the Negev Desert

Despite the important role played by microbiotic crusts in desert ecosystems, data concerning their recovery rates are scarce and are mainly based on estimates that fluctuate between several years to a few hundred years. In order to study the recovery rates of microbiotic crusts inhabiting sand dunes in the western Negev Desert, Israel, annual measurements of chlorophyll, protein, carbohydrates and moss counts were carried out during 1990–1995. Measurements were taken in two pairs of plots (1.5–6.3 m 2 ) established in each north- and south-facing aspect from which the upper 10 cm surface from one plot of each pair was removed. Recovery of the crusts was fast with surface-removed plots showing a complete recovery of chlorophyll a within 6–7 years, of protein within 6–8 years and of carbohydrates within 8–9 years. Recovery of the mosses was slightly longer at 17–22 years. The data are higher than the lower estimates of recovery but much lower than the higher estimates proposed in the literature. The data also suggest that upon prohibition of goat and sheep grazing (and consequently trampling) a relatively rapid stabilization process may take place in the north-eastern Sinai dune field.

The Green Algal Underground: Evolutionary Secrets of Desert Cells

Microscopic, unicellular, free-living green algae are found in desert microbiotic crusts worldwide. Although morphologically simple, green algae in desert crusts have recently been found to be extraordinarily diverse, with membership spanning five green algal classes and encompassing many taxa new to science. This overview explores this remarkable diversity and its potential to lead to new perspectives on the diversity and evolution of green plants. Molecular systematic and physiological data gathered from desert taxa demonstrate that these algae are long-term members of desert communities, not transient visitors from aquatic habitats. Variations in desiccation tolerance and photophysiology among these algae include diverse evolutionary innovations that developed under selective pressures in the desert. Combined with the single embryophyte lineage to which more familiar terrestrial green plants belong, multiple desert green algal lineages provide independent evolutionary units that may enhance understanding of the evolution and ecology of eukaryotic photosynthetic life on land.

The effect of restored microbiotic crusts on erosion of soil from a desert area in China

Samples of microbiotic crusts were collected along the northern part of the Zhongwei–Gantang section of the Baotou-Lanzhou railway, which lies at the southeastern fringe of China's Tengger Desert. We collected intact crust samples, let them recover for 1 year, then created five levels of disturbance: no disturbance (intact crusts), light disturbance (disturbance of 10% and 20% of the total area), moderate disturbance (40% disturbance), and severe disturbance (80% disturbance). We used these samples to simulate the effect of microbiotic crusts on wind erosion. Wind tunnel experiments let us determine the wind velocity required for the initiation of saltation, the threshold velocity ( u * ), the aerodynamic roughness length ( z 0), and the wind profile above sand surfaces covered by microbiotic crusts. The wind velocity for the initiation of saltation with an intact microbiotic crust was about 19 m s −1, which is greater than the value of 13.08 m s −1 for shifting sands. z 0 was between 0.03 and 0.13 cm, which was larger than the value of 0.0288 for shifting sands, and reached its maximum (0.13 cm) at the 40% disturbance level, and u * was between 0.15 and 1.21 m s −1. The relationships between u *, free-stream wind velocity ( u), and z 0 followed the equations u*= a+ bu and z 0=0.01563(1+ u *) 3.49341. The wind profile above the surface was divided into three sections, with the greatest changes in wind speed occurring below a height of 0.1 m.

Fungal control of nitrous oxide production in semiarid grassland

Fungi are capable of both nitrification and denitrification and dominate the microbial biomass in many soils. Recent work suggests that fungal rather than bacterial pathways dominate N transformation in desert soils. We evaluated this hypothesis by comparing the contributions of bacteria and fungi to N2O production at control and N fertilized sites within a semiarid grassland in central New Mexico (USA). Soil samples were taken from the rhizosphere of blue grama (B. gracilus) and the microbiotic crusts that grow in open areas between the bunch grasses. Soils incubated at 30% or 70% water holding capacity, were exposed to one of three biocide treatments (control, cycloheximide or streptomycin). After 48 h, N2O and CO2 production were quantified along with the activities of several extracellular enzymes. N2O production from N fertilized soils was higher than that of control soils (165 vs. 41 pmol h−1 g−1), was higher for crust soil than for rhizosphere soil (108 vs. 97 pmol h−1 g−1), and increased with soil water content (146 vs. 60 pmol h−1 g−1). On average, fungicide (cycloheximide) addition reduced N2O production by 85% while increasing CO2 production by 69%; bactericide (streptomycin) reduced N2O by 53% with mixed effects on CO2 production. N2O production was significantly correlated with C and N mineralization potential as measured by assays for glycosidic and proteolytic enzymes, and with extractable nitrate and ammonium. Our data indicate that fungal nitrifier denitrification and bacterial autotrophic nitrification dominate N transformation in this ecosystem and that N2O production is highly sensitive to soil cover, N deposition and moisture.

Exclusion effects on vegetation characteristics and their correlation to soil factors in the semi-arid rangeland of Mu Us Sandland, China

Exclusion has been applied as a main measure for re-vegetation all over the world. This paper, by comparing the results of year-round exclusion, seasonal exclusion, and non-exclusion, quantified the vegetation variations under three different exclusion measures and their correlation to soil factors. The analysis results for community species component and plant diversity using multi-response permutation procedures (MRPPs) showed that exclusion did change the species component and increase plant diversity remarkably, while the period of exclusion had no significant influence on these two community features. The indicator species analysis and calculation of similarity indices indicated that community for year-round exclusion were becoming xerophytization and unpalatability, and showed highly spatial heterogeneity of plant species distribution, whereas community for seasonal exclusion was under stable non-equilibrium condition. Detrended correspondence analysis (DCA) and detrend canonical correspondence analysis (DCCA) results of relationship between plant species and soil variables demonstrated that soil moisture was a controlling factor for plant species component, microbiotic soil crust cover, soil organic matter, and soil bulk density had significant effects on soil moisture, among which microbiotic soil crust was a leading factor owing to its limitation to rainfall infiltration on the one hand, and its constraints to entrance of herbaceous seeds into soil or to germination of soil seeds on the other hand. As a result of long-term removal of animal grazing, crust kept intact in year-round exclusion community, which was a main reason of community xerophytization. It was also obvious from ordination results that some important environmental factors, such as tempo-spatial change of rainfall and corresponding tempo-spatial change of soil moisture, were neglected during direct gradient analysis. In addition, biodiversity was close related to soil nutrients as well as to soil moisture condition (soil water content and crust cover), and it had positive relation to available N, and negative relation to available P. Higher soil N had advantage to non-leguminous plants growth on nutrition-poor sand land definitely. The impact of P to community component was unclear and should be studied from plant physiology. Further researches on non-equilibrium theory in semi-arid rangeland will provide a scientific and flexible animal development paradigm for being implementing livestock fen-raising and grazing-forbidden policies in China.

Effects of microbiotic crusts under cropland in temperate environments on soil erodibility during concentrated flow

AbstractSeveral studies illustrate the wind and water erosion‐reducing potential of semi‐permanent microbiotic soil crusts in arid and semi‐arid desert environments. In contrast, little is hitherto known on these biological crusts on cropland soils in temperate environments where they are annually destroyed by tillage and quickly regenerate thereafter. This study attempts to fill the research gap through (a) a field survey assessing the occurrence of biological soil crusts on loess‐derived soils in central Belgium in space and time and (b) laboratory flume (2 m long) experiments simulating concentrated runoff on undisturbed topsoil samples (0.4 × 0.1 m2) quantifying the microbiotic crust effect on soil erosion rates. Three stages of microbiotic crust development on cropland soils are distinguished: (1) development of a non‐biological surface seal by raindrop impact, (2) colonization of the soil by algae and gradual development of a continuous algal mat and (3) establishment of a well‐developed microbiotic crust with moss plants as the dominant life‐form. As the silt loam soils in the study area seal quickly after tillage, microbiotic soil crusts are more or less present during a large part of the year under maize, sugar beet and wheat, representing the main cropland area. On average, the early‐successional algae‐dominated crusts of stage 2 reduce soil detachment rates by 37%, whereas the well‐developed moss mat of stage 3 causes an average reduction of 79%. Relative soil detachment rates of soil surfaces with microbiotic crusts compared with bare sealed soil surfaces are shown to decrease exponentially with increasing microbiotic cover (b = 0·024 for moss‐dominated and b = 0·006 for algae‐dominated crusts). In addition to ground surface cover by vegetation and crop residues, microbiotic crust occurrence can therefore not be neglected when modelling small‐scale spatial and temporal variations in soil loss by concentrated flow erosion on cropland soils in temperate environments. Copyright © 2007 John Wiley & Sons, Ltd.

Runoff and Sediments from Hillslope Soils within a Native American Agroecosystem

Farmers of the Zuni Indian Reservation in New Mexico rely on materials transported from upper watersheds to maintain productivity of some of the oldest agricultural fields in North America. This study determined runoff and sediment production from hillslopes as functions of slope position, soil cover, and rainfall characteristics. Runoff was collected from plots in summit or shoulder [SU], backslope [BS], and footslope [FS] positions and in bare soil, microbiotic crust, oak, juniper, pinyon, and grass cover. In rainfall events that generated runoff, sediment C and N concentrations decreased with total sediment yield, but C/N ratios increased. Carbon/nitrogen ratios were generally lower in sediments from early season events. Backslope plots yielded the most sediment (125 g m−2) and the most organic C (2.2 g m−2), total N (116 mg m−2), and total P (34.2 mg m−2), but those from SU plots had the highest concentrations (e.g., 31 g C kg−1 compared with 23 g C kg−1 at BS and FS). Bare soil and microbiotic crust plots yielded the most sediments (441 g m−2) and grass the least (107 g m−2). Though variable, oak plots yielded more C (32.6 g m−2) and N (1.5 g m−2) than others, but bare soil and microbiotic crust plots yielded the most P (62.7 and 54.4 mg m−2, respectively). Slope position, cover type, and rainfall characteristics interact to influence movement and processing of materials responsible for agriculturally, ecologically, and hydrologically important alluvium‐derived soils in this semiarid agroecosystem.

Did Smoke from the Kuwait Oil Well Fires Affect Iranian Archaeological Heritage?

The combustion of crude oil produces a wide range of pollutants, including gases, volatile organic compounds, polycyclic aromatic hydrocarbons, acid compounds (e.g., sulfuric acid), and soot. Several of these pollutants have been linked with the deterioration and blackening of monuments. The paper reports the results of an investigation on the causes of the soiling of cultural remains at important archaeological sites in the provinces of Khuzestan and Fars, in southern Iran, assumed to be an effect of the Persian Gulf oil well fires of 1991. Different analytical techniques were applied to characterize the mineralogical composition of the damage layers, investigate the deposition of atmospheric particles, measure the anion concentrations, and identify and quantify the carbon components. The results showed that the black deposits on the surfaces of the Iranian monuments considered are mainly microbiotic crusts produced by cyanobacterial growth. No evidence was found of the deposition of particulate matter (smoke) produced by the Kuwait oil fires during the Gulf War.

Microbial community phenotypic profiles change markedly with depth within the first centimetre of the arable soil surface

The nature of the first few millimetres of a soil horizon strongly affects water infiltration rates, generation of run-off, and soil detachment. Whilst much is known about the physics and erosion of soil surfaces at this scale, little is known about their microbiology, particularly in temperate arable systems. This investigation aimed to discover whether any early colonisation stages of microbiotic crusts exist within the soil surface of temperate arable systems. The phenotypic structure of the microbial community was measured by means of phospholipid fatty acid analysis (PLFA) in soils sampled from the surface of arable fields that had been either cultivated 4 weeks previously or left undisturbed for 4–6 months. Within the top circa 1 mm of the soil that had been undisturbed for 6 months or more, distinct microbial communities were found to be present, which were statistically significantly different from the communities found in subsequent depths to circa 10 mm, where differences between communities were less pronounced. The PLFA responsible for the majority of the variation seen between depths was 16:0, the proportion of which was shown to decrease with depth. This was not the case in the recently cultivated soils, where communities were more homogeneous with respect to depth.

Effects of microbiotic crusts on evaporation from the revegetated area in a Chinese desert

Conflicting views exist on the evaporative effects of microbiotic crusts. The effects of microbiotic crusts on evaporation were studied using a microlysimeter under different simulated precipitation. The results show that under minor precipitation, the microbiotic crusts generally act as a retarding factor for evaporation, prolonging water retention in the surface layer in comparison with sandy soil, whereas under abundant precipitation, the crusts result in less infiltration and a greater total water loss through evaporation. It is possible that microbiotic crusts act as a major environmental driver in the succession of restored vegetation through their influence on evaporative water loss.

Seed Bank Responses to Grazing History by Invasive and Native Plant Species in a Semi-desert Shrub-steppe Environment

Invasive alien plants frequently possess greater seed banks than native species in disturbed areas, but native disturbance-adapted species may also possess large seed banks. We analyzed seed banks of ten sites with varying grazing histories in a shrub-steppe ecosystem dominated by antelope bitterbrush (Purshia tridentata) in the Okanagan valley in British Columbia, Canada. Overall effects of grazing on seed banks were overshadowed by site-specific differences, but canonical correspondence analysis (CCA) showed that the composition of the seed bank was significantly affected by bare soil which was positively correlated with grazing. Other factors affecting seed bank composition included litter, cover of spikemosses (Selaginella), shrub cover and microbiotic crust cover. The seed bank of the invasive herb diffuse knapweed (Centaurea diffusa) was largest at two of the three most heavily grazed sites. Cheatgrass (Bromus tectorum), another invasive species, exhibited large seed banks at all sites regardless of grazing history. Native species such as sand dropseed (Sporobolus cryptandrus) and Douglas' knotweed (Polygonum douglasii) had substantial seed banks (> 1500 seeds m−2). Planting sand dropseed, Douglas' knotweed, needle-and-thread grass (Hesperostipa comata) or their ecological equivalents could aid in the restoration of arid ecosystems because of their adaptation to disturbance and persistence of seeds in the soil.

Millimeter-scale microrelief affecting runoff yield over microbiotic crust in the Negev Desert

The negative effect of microrelief upon runoff yield, explained by the increase in water storage and the slowdown in flow velocity, is a known phenomenon. However, research concerning surface roughness hitherto focused on decimeter- or centimeter-scale microrelief. Owing to the heterogeneous character of many natural plots, the effect of centimeter-scale microrelief was mainly shown under controlled sprinkling experiments, whereas no data was yet made available concerning the possible effect of a millimeter-scale microrelief upon runoff yield under natural field conditions. When runoff yield was measured over crusted (i.e., surfaces covered by 1–3 mm of cyanobacterial crust) and scalped 2–6 m 2 plots at the Hallamish dune field (Negev Desert, Israel) during 5 winter seasons (1990–1995), no runoff was generated from the scalped plots during the first year following scalping while meagre quantities were received during the second year. Nevertheless, during the third season and onward, runoff yield at the scalped plots was consistently and significantly higher than that of the crusted (control) plots and this was so albeit the fact that the crust chlorophyll content of the scalped plots during the third season was as low as half the amount of the crusted plots. These findings appeared to contradict previous findings that showed the existence of a positive linear relationship between the crust chlorophyll content and runoff yield. The apparent contradiction was explained by the differences in the plot microrelief, indicating that minute differences, even of a millimeter-scale, may greatly affect runoff yield and thus may compensate for lower crust chlorophyll content. Surface smoothness, which characterizes many of the arid zones, may thus explain, at least partially, the high runoff yield obtained in deserts.

Microbiotic crusts and their interrelations with environmental factors in the Gurbantonggut desert, western China

Located in the Junggar Basin in Xinjiang, the Gurbantonggut Desert is the second largest desert in China. Microbiotic crusts consisting of animalcule, lichen, moss, and algae species develop extensively in the region. Their formation, species composition and distribution pattern are closely related to the environmental conditions along the different parts of sand dune. Analysis of microbiotic crust distribution and relationship to environmental factors shows that average microbiotic crust thickness is 0.05-0.1 cm at the tops dunes, 0.2-1.5 cm in the upper part, 1.5-2.5 cm in middle and lower parts of dunes, and 1.5-5.0 cm in interdune areas, while areal coverage is 30.5, 48.5, 55.5, and 75.5%, respectively. Microbiotic crust differentiation along dune slopes is a result of the development stage and converse-succession resistance of the different microbiotic crusts. The numbers of species, thickness and degree of development of microbiotic crusts increase from the upper part to the middle and lower parts of dune slopes. The development and differentiation of microbiotic crusts at various dune slope positions are a reflection of the ecological expression of the comprehensive adaptability and natural selection of different microbiotic crust species to the local environmental conditions, and are closely related to such ecological conditions as the physiochemical properties of soils and topsoil textural stability.

Soil organic carbon and microbial activity: east Antarctica

SummarySchirmacher oasis (SO) (70°46′04′′S to 70°44′24′′S; 11°49′54′′[± 48]E to 11°26′03′′[± 02]E), one of the smallest oases in Antarctica, is situated on Dronning Maud Land, which is about 70 km south of the Princess Astrid Coast of east Antarctica. This oasis is a small rocky moraine, surrounded by the vast polar ice cap and Antarctic ice shelf. It represents cold desert conditions, devoid of any higher plant and animal life, except for a few patches of microbiotic crusts in some suitable niches. Melted water from glaciers, ice and snow produces about 30 fresh water lakes and many streams, which supply essential nutrients to the autotrophs (algae, mosses and lichens). Between 30 December 1999 and 29 January 2000, soil samples were collected from 14 sparsely vegetated sites to study the soils and ecology over this oasis. Bio‐physicochemical parameters, organic carbon and microbial activities (dehydrogenase) of the soils were determined. The average surface air temperature and wind velocities during the sampling period were −0.87°C and 4.3 m s−1. The average pH, plant biomass (standing crops) and moisture content were 7.5, 22.5 g m−2 and 375.4%. Total organic carbon (TOC) contents of the soil samples ranged from 1.16 to 2.58% and the mean value was 1.58%. Dehydrogenase activity (DHA) was low and the average was 0.008 mg Triphenyl formazan (TPF) g soil−1 day−1. The low DHA in SO suggests that anaerobic oxidation of organic C is poor. TOC and DHA are negatively correlated with plant biomass (r=−0.14, P= 0.62 and r=−0.21, P= 0.48). The organic C and microbial activities are dependent on the amount of the autotrophic productivity and abundances. TOC correlated significantly with DHA (r= 0.85, P < 0.001), which indicates that organic C is an important factor in controlling the development of DHA in the SO. The averaged bio‐physicochemical data in the oasis do not deviate much from the respective mean values and the TOC is expected to remain in the range of 1–2%; however, a small change in human activity is likely to cause long‐term impacts in this pristine ecosystem.

Tensile test of natural microbiotic crust

The mechanical properties of microbiotic crust are important to stabilize sandy surfaces in arid and semi-arid regions. We developed a new experimental approach to perform the tensile test of natural microbiotic crust. The modulus of elasticity, ultimate stress and one-dimensional stress–strain relation was obtained. The microbiotic crust we measured exhibits linear elastic behavior firstly and then breaks. This mechanical character was applied to the study of the rupture of microbiotic crust under the impact of one saltating grain. A very simple dimensionless variable was suggested to quantitatively assess surface stability.

Effects of microbiotic crusts on dew deposition in the restored vegetation area at Shapotou, northwest China

Information regarding dew deposition on microbiotic crusts is scarce in Chinese desert areas. An area of restored vegetation, where microbiotic crusts with different developmental levels are distributed in the revegetated enclosures of different ages, provides an ideal opportunity to study the hydrological issues related to the development processes of microbiotic crusts in a temporal sequence. The effects of microbiotic crusts on dew condensation were studied during the late summer and autumn of 2004. The results show that the amount of dew increases with the level of development of the microbiotic crusts. The physical crust, which is an initial form of microbiotic crust and is composed of sand with a higher proportion of clay and silt because of its aeolian origin, collects more dew than sand soil. In addition, the microorganisms adhering to the crusts cause the amounts of dew on the algae and moss crust to increase dramatically. ANOVA analysis results also indicate a significant difference between well-developed microbiotic crusts (algal and moss crusts), initial microbiotic crusts (physical crust) and sandy soil. It is potential that dew acts as a driving factor for restored vegetation succession through its benefits in the development of microbiotic crust.

Mechanical Disturbance of Microbiotic Crusts Affects Ecohydrological Processes in a Region of Revegetation-fixed Sand Dunes

ABSTRACT Microbiotic crusts (MC), also called biological soil crusts or cryptogamic crusts, are formed by cyanobacteria, fungi, blue-green algae, lichens, and mosses, and are widespread in arid and semiarid zones such as the area of sands fixed in place by revegetation near Shapotou at the southeastern edge of China's Tengger Desert. We studied mechanically disturbed and 40-year-old intact MC in this area using a series of soil hydrological experiments and ecological investigations to examine the ecohydrological responses after mechanical disturbance of the MC. Once the MC was disturbed, the MC layer became ore primitive or disappeared entirely, resulting in a 32.8% decrease in the fine particles content of the upper soil layers, a 28.7% increase in soil albedo and a 168.9% decrease in the topsoil's water-retention capacity. These changes greatly altered soil hydrological processes in the disturbed soils: the steady-state infiltration rates in the upper soil layer increased by 693%, the precipitation recharge layer deepened, and the surface evaporation rate decreased by 20.3%. Moreover, the disturbance increased storage of plant-available water in the herbaceous rooting zone and improved the environment for germination and subsequent growth of annual herb species, as shown by a notable increase in the coverage, density, frequency, and biomass of annual plants. We conclude that MC represent a major component of Shapotou's regional ecosystem and that disturbance will significantly alter local ecohydrological processes.

Experimental Studies on the Natural Restoration and the Artificial Culture of the Moss Crusts on Fixed Dunes in the Tengger Desert, China

Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world and play an important ecological role. Moss is one of the major components in the crusts. The reproduction and establishment of the mosses are crucial to the formation of moss crusts. Bryum argenteum is the dominant species of moss crusts in the Shapotou region (104°57′E, 37°27′N) of the Tengger Desert. In search for the characteristics of natural reproduction and establishment of the mosses, 10 quadrates (10×10 cm for each) were obtained by removing the moss crusts in different positions of fixed dunes. These 10 quadrates were observed for 3 years depending on the species’ components and coverage. Meanwhile, in the third year, two quadrates (1×1 m for each) were set up in a crust-absent area and two different experiments of the asexual reproduction (broadcast planting and offshoots) were conducted, respectively. The reproductive process was observed under the microscope, and the morphological indicators of the new individuals were measured. The results were compared with the ones from indoor experiments using the same methods. All the results showed the following: (1) 70% of the quadrates (i.e., 7 of the 10 quadrates) were recovered within 3–4 years; thus, the quick recovery might be due to the dispersal and reproduction of the fragments of stems and leaves of B. argenteum; (2) as for the two quadrates in the artificial reproduction test, the new plants occupied the uncovered space of the quadrates in 1 month, and there were two main reproduction approaches, one of which was that the stems continually branched and produced young plants, and the other was that the young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema, which finally developed into a large number of new plants; (3) the reproductive characteristics were identical, though the protonema in the field was more robust and had more branches than the ones indoors.