Components Of Biological Soil Crusts Research Articles

The effects of drying following heat shock exposure of the desert moss Syntrichia caninervis

Desert mosses are components of biological soil crusts (BSCs) and their ecological functions make assessment and protection of these mosses a high-ranking management priority in desert regions. Drying is thought to be useful for desert mosses surviving heat shock. In this study, we investigated the role of drying by monitoring the responses of physiological characters and asexual reproduction in the typical desert moss Syntrichia caninervis. Heat significantly decreased chlorophyll content and weakened rapid recovery of photochemical activity, and increased carotenoid content and membrane permeability. Lethal temperatures significantly destroyed shoot regeneration potential. In comparison with heat alone, drying significantly increased protonema emergence time and depressed protonema emergence area. Drying combined with heat accelerated water loss, followed by a decrease of photosynthetic activity. Drying had different influences on membrane permeability at different temperatures. When moss leaves were subjected to a combined stress of drying and heat shock, photosynthesis was maintained mainly due to the effects of drying on physiological activity although the cellular morphological integrity was affected. Drying caused opposing effects on moss physiological and reproductive characteristics. On the one hand, drying caused a positive synergistic effect with heat shock when the temperature was below 40 degrees C. On the other hand, drying showed antagonism with heat shock when the moss was subjected to temperatures higher than 40 degrees C. These findings may help in understanding the survival mechanism of dessert mosses under heat shock stress which will be helpful for the artificial reconstruction of BSCs.

A Technology for Rapid Reconstruction of Moss-Dominated Soil Crusts

Reconstruction of moss-dominated soil crusts is crucial for ecological restoration. A desert moss Tortula desertorum (Broth.), the main component of biological soil crusts in the Gurbantunggut desert, was used to build a procedure for construction of moss-dominated crust. Micropropagation of desert mosses is a core technology to build biological soil crusts. Although the micropropagation of mosses has been extensively studied, little is known about that of desert mosses. Effects of media, explants, and culture temperature on regeneration potential of T. desertorum were investigated respectively in this study. The factors such as relative humidity, light intensity, and photoperiod, which might take an important role in the regeneration and development of the desert moss T. desertorum, were optimized through an orthogonal test design. The life cycle of the desert moss T. desertorum in cultivation was also investigated according to several factors affecting asexual reproduction. The results showed the explants cultivated with in situ soil had produced more protonema and shoots than those cultivated with other media. Detached leaves as explants yielded more biomass per gametophyte. It was found that a slightly higher temperature facilitated shoot growth. It should be pointed out that the favorable period for T. desertorum asexual reproduction occurred mainly in early summer, which contributes to the efficient protection of biological soil crusts. Based on the life cycle of T. desertorum in cultivation, a procedure for artificial reconstruction of moss-dominated soil crusts was established and assessed. A large number of protonema were induced to grow by breeding detached green leaves in agar-solid Knop medium after 1 month as day/night temperature and humidity were set at 20/10°C and 60–85%, respectively. Moss-dominated crusts formed through transplanting protonema into sand supplemented with liquid Knop medium under day/night temperatures of 25/15°C after another month.

The variation of morphological features and mineralogical components of biological soil crusts in the Gurbantunggut Desert of Northwestern China

Increasingly complex life forms were found in older biological soil crusts in the Gurbantaunggut Desert in Northwestern China. These crusts may play a critical role in mineral erosion and desert soil formation by modifying the weathering environment and ultimately affecting mineralogical variance. To test this hypothesis, variations in the morphological features and mineralogical components of successional biological soil crusts at 1 cm were studied by optical microscopy, SEM and grain size analysis. Concentrations of erosion-resistant minerals decreased with crust succession, while minerals susceptible to weathering increased with crust development. Neogenetic minerals were found in late stage crusts, but not in early stage crusts. Silt and clay concentrations were highest in early formation crusts and soil mean particle size decreased with crust succession. Cyanobacteria, lichen and moss were shown to erode and etch rocks, and secondary minerals produced by weathering were localized with the living organisms. Thus, more developed crusts appeared to contribute to greater mineral weathering and may be a major cause of mineralogical variance seen in the Gurbantunggut Desert. The greater activity and complexity of older crusts, as well as their improved moisture condition may function to accelerate mineral weathering. Therefore, protection and recovery of biological crusts is vital for desert soil formation.

Distribution and composition of cyanobacteria, mosses and lichens of the biological soil crusts of the Tehuacán Valley, Puebla, México

Cyanobacteria, mosses and lichens are the main components of biological soil crusts that cover extensive areas of cold and hot deserts. Approximately 50 species of cyanobacteria, 52 species of mosses and 34 species of lichens have been described from North American deserts. We collected samples of biological crusts from 87 sites in the rainshadow desert of Tehuacán, Puebla, central Mexico, to compare the assemblages of cyanobacteria and mosses with those from other North American sites. We found seven species of cyanobacteria, 19 species of mosses and eight species of lichens within the sampled soil crusts. Cyanobacteria were present in all crusts, with the most common species being Scytonema javanicum, Microcoleus paludosus and Chroococcidiopsis sp. Seven species of mosses are unique to the region, with Pottiaceae and Bryaceae being the best represented families. Placydium squamulosum and Lepraria spp. were the most common lichens. Sørensen analysis shows that the assemblages of cyanobacteria and moss communities of Tehuacán are different from other deserts, despite the presence of several cosmopolitan species in the sampled soil crusts.

Comparing Artemisia sieberi Besser and Artemisia scoparia Waldst and Kit. Elemental Content Grown on Crusted and Uncrusted Soils

Biological soil crusts occur as assemblage of lichens, mosses, liverworts, and cyanobacteria. Lichens and mosses are the two important components of biological soil crusts, especially in arid and semiarid rangeland environments, where vascular plants vegetation is poor. Biological soil crusts contribute to a variety of ecological functions. The current study was carried out to compare two native shrubs elemental content. For this purpose, aerial parts of two native annual and perennial shrubs, Artemisia scoparia and A. sieberi, were collected from crusted and uncrusted soils in Qara Qir rangelands, next to Iran - Turkmenistan border line. N, P, K, Zn and Fe of the samples were measured. Factorial experiment based on Completely Randomized Design (CRD) was used for data analysis. Results showed that N, Fe and Zn content of samples collected from crusted and uncrusted sites were significantly different. Different treatments showed different behavior for each of mentioned elements. A. scoparia related to crusted and uncrusted soils contained the highest and lowest nitrogen percent, respectively. Zinc of A. sieberi and A. scoparia both collected from crusted site showed the greatest and lowest amount, respectively. This status was true for Fe changes in understudy treatments, too.

Biological soil crusts in deserts: a short review of their role in soil fertility, stabilization, and water relations

Cyanobacteria and cyanolichens dominate most desert soil surfaces as the major component of biological soil crusts (BSC). BSCs contribute to soil fertility in many ways. BSC can increase weathering of parent materials by up to 100 times. Soil surface biota are often sticky, and help retain dust falling on the soil surface; this dust provides many plant-essential nutrients including N, P, K, Mg, Na, Mn, Cu, and Fe. BSCs also provide roughened soil surfaces that slow water runoff and aid in retaining seeds and organic matter. They provide inputs of newly-fixed carbon and nitrogen to soils. They are essential in stabilizing soil surfaces by linking soil particles together with filamentous sheaths, enabling soils to resist both water and wind erosion. These same sheaths are important in keeping soil nutrients from becoming bound into plant-unavailable forms. Experimental disturbances applied in US deserts show soil surface impacts decrease N and C inputs from soil biota by up to 100%. The ability to hold aeolian deposits in place is compromised, and underlying soils are exposed to erosion. While most undisturbed sites show little sediment production, disturbance by vehicles or livestock produces up to 36 times more sediment production, with soil movement initiated at wind velocities well below commonly-occurring wind speeds. Winds across disturbed areas can quickly remove this material from the soil surface, thereby potentially removing much of current and future soil fertility. Thus, reduction in the cover of cyanophytes in desert soils can both reduce fertility inputs and accelerate fertility losses.

Patton's Tracks in the Mojave Desert, USA: An Ecological Legacy

Recovery of soil properties from World War II-era military training exercises in the Mojave Desert was measured approximately 55 years following disturbance. Tracks from military vehicles were still visible, particularly in areas of desert pavement. Soil penetrability was much lower in visible tracks than outside the tracks. Soils in tracks had fewer rocks in the top 10cm of the soil profile than adjacent untracked soils. Larger particles (> 4.8mm) formed a moderately well-developed pavement outside of the tracks, while smaller, loose particles ( h 4.8mm) dominated the surface of the tracks. The time required to restore the desert pavement is likely to be measured in centuries. Based on biomass estimates, the cyanobacterial component of biological soil crusts had recovered 46-65% in tracks, compared to outside the tracks. Overall recovery of lichen cover has been much slower. Under plant canopies, cover of Collema tenax was not significantly different between areas inside and outside the tracks; however, recovery of Catapyrenium squamulosum was only 36%. In plant interspaces with less favorable moisture and temperature conditions, C. tenax showed a 6% recovery and C. squamulosum a 3% recovery. Assuming recovery of the biological soil crust is linear, and complete only when the most sensitive species (C. squamulosum) has fully recovered in the most limiting microhabitats (plant interspaces), it may require almost two millennia for full recovery of these areas.