Bo Xiao

China Agricultural University | CAU · College of Land Science and Technology

Biological soil crusts (BSCs) are extensively developed and commonly regarded as a kind of vegetation in desertification areas around the world. The natural recovery process of BSCs after disturbance and their long-term impacts on the soil water conditions are important but not well understood. In order to provide more insights into this problem, w...

Soil and water loss have become a critical problem on sloping croplands in Northern China. Vetiver grass (Vetiveria zizanioides (L.) Nash) hedges have been suggested to be effective in preventing soil and water in tropical and subtropical regions but appear to be ineffective in temperate regions because they cannot withstand the low temperatures in...

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...

Biological soil crusts are receiving increasing attention due to their potentially positive effects on desert ecosystems. Artificial propagation of crusts is one way to restore degraded desert soils. However, little is known about their effectiveness on overland flow or water infiltration. Consequently, a study was done on soils of the Loess Platea...

As an important biological component of the soil surface in drylands, biocrusts play an indispensable role in maintaining soil ecosystem multifunctionality. However, the microstructure of these biocrusts remains unclear. For this end, both cyanobacterial and moss crusts inhabiting sandy and loessial soils were collected on the Chinese Loess Plateau...

Vascular plants and biocrusts are highly vulnerable to climate change in drylands wherein they control carbon (C) cycling. In drylands, these organisms are known to thrive alone or coexisting with each other. Yet, how multiple combinations of biocrusts and vascular plants influence C cycling remains poorly understood. Here, we conducted a mesocosm...

Biocrusts are a critical surface cover in global drylands, but knowledge about their influences on surface soil thermal properties are still lacking because it is quite challenging to make accurate thermal property measurements for biocrust layers, which are only millimetres thick. In this study, we repacked biocrust layers (moss‐ and cyanobacteria...

Biocrusts are an important component of dryland ecosystems as they perform crucial ecological functions like stabilizing soils, mediating the hydrological cycle, and improving nutrient availability. The high mechanical stability of biocrusts is understood to be linked to exopolymeric substances (EPS), which in turn, are responsible for the adsorpti...

Commonly comprised of cyanobacteria, algae, bacteria and fungi, hypolithic communities inhabit the underside of cobblestones and pebbles in diverse desert biomes. Notwithstanding their abundance and widespread geographic distribution and their growth in the driest regions on Earth, the source of water supporting these communities remains puzzling....

The role of runoff in providing nutrients to runon loci in deserts was not extensively explored. Here we report 2 years of measurements of the chemical composition of rain and runoff (three events for each year, which correspond to the long-term runoff events) in plots that were constructed over four biocrust types in the Negev Desert, Israel. The...

Biocrusts perform important ecological functions such as stabilizing the soil surface, resisting erosion, regulating soil water partitioning, storing soil fertility, and promoting biological community diversity. The mechanical stability of biocrusts is the physical basis for many of their ecological functions, while their high mechanical stability...

Background and aims Vascular plants and moss biocrusts are known to coexist in drylands, wherein vascular plant cover is known to be a major influencing factor for biocrusts development. Vascular plants produce litter which may affect moss biocrusts when covering them. However, to which extent the cover of litter may affect the physiology, e.g., p...

Biological soil crusts (biocrusts) are living ground covers that result from intimate associations between soil particles and organisms, which can modify soil properties and support fundamental ecosystem functions in drylands. Despite numerous studies concerning effects of biocrusts on soil hydrological processes, their impacts on grassland evapotr...

Although commonly considered the gold standard for measurement of non-rainfall water (NRW), providing reasonable reliable data for vegetated soils, microlysimeters (MLs) tend to grossly overestimate NRW (primarily in form of dew) on barren soil. In arid and semiarid regions, the reported values may be overestimated by hundreds and even 1000 %. This...

Soil surface cover is one of the most critical factors affecting soil water vapor transport, especially in drylands where water is limited, and the water movement occurs predominantly in the form of vapor instead of liquid. Biocrusts are an important living ground cover of dryland soils and play a vital role in modifying near‐surface soil propertie...

Seasonally frozen soils are extensively distributed in drylands at middle- and high-latitude regions across the earth and experience intensive freeze-thaw cycles during cold winters. Cyanobacterial and moss biocrusts are critical living skins that cover a large portion of cold-winter drylands and, thus, have potential to regulate soil structure and...

Abstract book containing 66 papers both in English and in Chinese that presented during this symposium.

Biocrusts are a prevalent form of living cover in worldwide drylands, and their presence are intimately associated with herbaceous community, forming a spatially mosaic distribution pattern in dryland ecosystems. The role of biocrusts as modulators of herbaceous community assembly is extensively studied, whereas, less is known whether their interac...

Biocrusts are common living covers found across drylands worldwide, and their photosynthesis substantially contributes to carbon input in these ecosystems. However, direct monitoring of biocrusts’ photosynthetic carbon fixation is challenging due to their scattered distribution, dark pigments, and lower CO2 exchange rate. Current studies have limit...

Evaporation, one of the main components of the water and energy balance between soil and atmosphere, plays a key role in hydrological processes particularly in semi-arid and arid climate regions. As critical living organism communities inhabiting the soil-atmosphere boundary, biocrusts are capable of modifying near-surface soil properties and struc...

Soil nematodes are the most abundant animals on Earth and play critical roles in regulating numerous ecosystem processes, from enhancing primary productivity to mineralizing multiple nutrients. In dryland soils, a rich community of microphyte organisms (biocrusts) provide critical habitats for soil nematodes, but their presence is being threatened...

The effect of biochar amendment of a multi-element contaminated soil on the transfer and accumulation of Cd, Zn, Pb, and As in wheat was investigated in this study. Addition of biochars from rice residues (straw, husk, and bran) significantly decreased shoot Cd, Zn, and Pb concentrations by up to 71%, 37%, and 60%, respectively, but increased As by...

Biocrusts are known to regulate soil respiration in drylands. However, how biocrusts influence the changes in soil respiration across seasons and soil depths is far less understood. This knowledge gap hampers our ability to accurately predict the impacts of biocrust development or disturbance on soil carbon (C) balance in drylands, which covers alm...

Given their global prevalence, dryland (including hyperarid, arid, semiarid, and dry subhumid regions) ecosystems are critical for supporting soil organic carbon (SOC) stocks, with even small changes in such SOC pools affecting the global carbon (C) cycling. Biocrusts play an essential role in supporting C cycling in semiarid ecosystems. However, t...

Biocrusts are a crucial living cover of dryland soils that alter near-surface soil structure and properties. To date, it is still unclear how biocrusts affect soil pore structure, and subsequently alter gas and water transport processes. In this study, we investigated aeolian sand and loess soil colonized with moss-dominated biocrusts and in bare s...

The term ‘succession’ was first proposed to describe the gradual development of plants from an initial stage such as a bare ground to a well-developed plant community, which at its peak, may reach a climax (primary succession). Accordingly, the earlier and fast growing stage (such as an annual plant community) may grant stability, organic matter an...

The Great Wall of China, one of the most emblematic and historical structures built by humankind throughout all of history, is suffering from rain and wind erosion and is largely colonized by biocrusts. However, how biocrusts influence the conservation and longevity of this structure is virtually unknown. Here, we conducted an extensive biocrust su...

Knowledge regarding dew distribution has great ecological importance in light of the uncertainty regarding recent climate change and its effect on microorganisms. Nevertheless, the role of dewfall as a water source for biocrusts is controversial, with most scholars attributing a central role to dewfall as water source for biocrusts, a notion that p...

Regardless of lithology and plant cover, chemical composition of floodwater in the Negev show a consistent enrichment in K+ and Mg2+ ions, which could not have been explained by the rock or clay minerals or (due to the scarcity of plants) by plant decomposition. Hypothesizing that rock-dwelling (lithobionts) or soil (loess)-dwelling biocrusts may s...

Biocrusts are a dominant component in drylands worldwide and play critical roles in supporting soil microbial diversity and carbon (C) stocks. Nitrogen (N) fertilization associated with human activities threatens drylands, which are often considered N-limited ecosystems. Here, we conducted a field experiment in two contrasting soil types (loess vs....

Biological soil crusts (biocrusts) are a prevalent form of organic cover in drylands across the world, and they play a crucial role in shaping the ecohydrological processes and functioning of dryland ecosystems. However, in desert steppe ecosystems, the ecohydrological influences of biocrusts and their pathways have not yet been thoroughly understo...

Biological soil crusts (biocrusts) are widely distributed in global drylands and have multiple significant roles in regulating dryland soil and ecosystem multifunctionality. However, maps of their distribution over large spatial scales are uncommon and sometimes unreliable, because our current remote sensing technology is unable to efficiently disc...

AimsBiocrusts, the living skin of dryland ecosystems, contain diverse soil microorganisms that are essential to biocrust formation and the maintenance of multiple ecological functions including nitrogen fixation, carbon sequestration, soil stability, and rainfall redistribution. We know that biocrusts are important modulators of the soil microbiome...

As a crucial living skin inhabiting the soil-atmosphere interface, biocrusts play a vital role in various soil properties and processes, especially surface soil pore structure and soil pore-related hydrological processes, such as infiltration and evaporation. However, it remains unclear how biocrusts affect pore structure in the micrometric point o...

To investigate the effects of biocrusts development on aggregate stability and splash erosion of Mollisols and to understand its function in soil and water conservation, we collected biocrusts (cyano crust and moss crust) samples in croplands during the growing season and measured the differences in aggregate stability between biocrusts and uncrust...

Global climate change is expected to cause both increased and reduced precipitation in the next decades, especially in drylands with semi-arid climates. Biocrusts are an essential soil surface cover in global drylands, and they strongly influence most soil properties and support fundamental ecosystem functions, especially soil carbon (C) cycling. N...

Soil aeration is an important factor influencing soil biological and biochemical processes because it directly affects soil microbial activity and respiration. As an important living skin of the soil, biocrusts strongly impact various soil properties and play a vital role in maintaining surface soil structure and multifunctionality. Although there...

Soil gas transport properties and aeration are essential influencing factors of soil chemical and biochemical reactions, especially the respiration processes of plant roots and microorganisms. As ecosystem engineers in drylands, biocrusts may greatly alter surface soil gas transport properties and aeration, but their influences remain unclear and u...

As a “living skin” of soil in drylands, biocrusts possibly change the retention and movement of soil water, and thus critically influence hydrological and erosion processes as well as soil moisture regime. Contrary to vertical infiltration, little attention was paid to horizontal infiltration, which may provide important information on soil water d...

Accurate estimation of soil carbon (C) stock and efflux in drylands is vital for understanding the C cycling processes and predicting global climate change. As a “living skin”, biocrusts strongly change soil C fixation and respiration, but till now it is still challenging to accurately estimate and assess biocrust's contributions to soil C stock an...

As a crucial living feature inhabiting the soil‐atmosphere boundary, biocrusts play a vital role in liquid water or vapor transport through surface soil and thus have strong effects on soil water regimes. However, it remains unclear how biocrusts affect annual or multi‐year soil water budgets through the regulation of evaporation outputs and NRW or...

Globally widespread biocrusts form a “living skin” on most dryland soils, helping govern fundamental ecosystem functions, particularly hydrological processes. However, the underlying mechanisms of biocrust effects on soil water infiltration and evaporation are still controversial. Biocrusts possibly regulate infiltration and evaporation due to thei...

The changes in soil properties caused by grazing and trampling are important reasons for the changes in soil respiration rates, carbon fixation, and emission. However, the effects of different intensities of grazing and trampling on biocrusts respiration rate are unclear. In this study, we simulated grazing and trampling disturbances of 10%, 30%, 5...

We selected typical croplands in the black soil region of Northeast China to analyze the characteristics of biocrusts during the growing season, including species composition, thickness, coverage, and biomass (chlorophyll content). We collected bareground soil and biocrusts samples with chlorophyll content of 5-15, 15-25, 25-35, and 35-50 mg·g-1, a...

Microhabitat factors play an important role in regulating bryophyte species distribution and the development of bryophyte-dominated biological soil crusts (hereafter bryophyte crusts). We investigated the distribution and development of bryophytes in eight microhabitats in the water-wind erosion crisscross region of the Loess Pla-teau. We used the...

Biocrusts are photosynthetic biotic communities of cryptogams and microbes that aggregate minerals at the soil surface in many ecosystems. Due to their high tolerance to harsh environments, biocrusts are present in a wide range of habitats, but are especially representative ground covers in regions with restricted vegetation growth, such as dryland...

Globally widespread, biocrusts form a “living skin” on most dryland soils, helping govern fundamental ecosystem functions, particularly water and heat balances in drylands. Nevertheless, the underlying mechanisms of biocrust effects on topsoil thermal properties and temperature (T) are still unclear. In this study, we continuously measured thermal...

Long‐term field campaigns in the Negev observed wet‐dry cycles (WDCs) following rain events, principally on sand. Aiming to assess the relevant mechanism (whether dewfall, water capillarity or distillation derived by temperature‐induced vapor flux (TIVF) which stems from the soil), a set of outdoor experiments was conducted on sand and loess. They...

The scholarship on evaporation has yet to fully comprehend the effects of biocrusts on evaporation. This lacuna profoundly impacts our understanding regarding the hydrological role played by biocrusts in shaping arid and semiarid ecosystems. While most scholars maintain that biocrusts decrease evaporation, playing therefore a cardinal positive role...

Understanding the physical, chemical, and biological processes and estimating water balance in drylands rely on accurate soil moisture (θ) measurements. Surface soil moisture is influenced by the presence and types of bio-crusts because they strongly modify surface soil properties and hydrological processes. Nevertheless, it is still a challenge to...

Biocrusts are extensively developed in arid and semiarid climate regions, and they cover a large part of land surface with degraded sparse vegetation. Due to their mulch effects and biological metabolism, biocrusts exert an important influence on almost every ecological process, such as soil water and nutrient cycle, carbon and nitrogen sequestrati...

Soil evaporation is a three-stage process and plays a vital role in soil physical, chemical, and biological processes, as well as global climate change. As an important living skin, biocrusts strongly influence most soil properties and support fundamental ecosystem functions. Although there are many studies concerning biocrust effects on surface so...

As ecosystem engineers in drylands, biocrusts possibly generate great influences on surface soil water holding capacity and availability, but these effects have not yet been sufficiently investigated, especially through analyzing and modeling their soil water retention curve (SWRC). On the Loess Plateau of China, the naturally developed moss biocru...

The assumption that microlysimeters (MLs) adequately reflect the soil conditions is widespread. Nevertheless, previous findings raised doubts regarding the reliability of MLs to adequately reflect the amounts of dew and fog of the intact soil (control, COT). We therefore hypothesized that the structure (whether a single cylinder inserted into the s...

Surface soil vapor sorption and non-rainfall water (NRW) deposition are important sources, and can be highly influential in soil water dynamics and biochemical processes in drylands. As an important living skin, biocrusts have great impacts on soil water balance and play a vital role in water transport at near surface soil, while it remains unclear...

Non-rainfall water deposition is an important water resource, critical for the survival of dryland vegetation and soil biota and maintaining dryland water balance. As a “living skin”, biocrusts are attracting increasing attention due to their potentially positive impacts on non-rainfall water deposition. However, the magnitude and underlying mechan...

The distribution characteristics of exogenous carbon (C) in the C fractions of biocrusts-covered soil are critical for understanding the geochemical cycling of C with biocrusts in drylands. A 13C pulse labeling experiment was conducted for moss-dominated biocrusts-covered soil and bare soil on the Loess Plateau of China with semiarid climate, with...

Biological soil crusts (BSCs) greatly change surface soil structure and nutrient enrichment processes in arid and semiarid regions. However, their impacts on solute transport characteristics and nutrient loss are still not clear. In this study, the solute (Cl- and Ca2+) transport experiments were conducted on soils covered by moss-dominated BSCs an...

Nitrogen (N) labeled with 15N was evenly added into plots of moss-dominated biological soil crusts (BSCs) and bare soil on the Chinese Loess Plateau. After that, the surface BSCs and bare soil samples were continuously collected within 1-30 days. The 15N content of each N fraction in soil, microorganisms, and mosses was measured for each sample. Th...

Biocrust is a potentially extensive living cover in drylands, which comprises much of the land surface, but presently its contribution to the soil respiration rate (Rs) and CO2 efflux is still not clearly understood. In this study, we continuously measured the Rs of moss-dominated biocrust (biocrust and biocrust covered soil) and bare soil, togethe...

Land surface albedo measures the degree to which the sun's radiation is absorbed or reflected, and thus can be highly influential in global climate trends, local weather phenomena, and biological processes. As an extensive living cover in drylands, biocrusts cover substantial land surface but their potential influences on surface albedo and energy...

Biocrusts are widely distributed throughout the world in dryland ecosystems, but their respiration rate (Rs) and responses to soil temperature and mositure have not yet been fully investigated. In a semiarid region of the Loess Plateau in China, the Rs of moss-dominated biocrusts was continuously (104 days) measured in summer through an automated s...

Biocrust effects on soil infiltration have attracted increasing attention in dryland ecosystems, but their seasonal variations in infiltrability have not yet been well understood. On the Chinese Loess Plateau, soil infiltrability indicated by saturated hydraulic conductivity (Ks) of biocrusts and bare soil, both on aeolian sand and loess soil, were...

Biocrusts are promising ecosystem engineers in dryland ecosystems, but their effects on soil temperature, which is the most important environmental factor of soil biological and biochemical processes, have not yet been well understood. In a semiarid ecosystem on the Chinese Loess Plateau, the thermal properties of moss-dominated biocrust layer and...

Biocrusts are vulnerable to large scale disturbances including trampling activities, and their recovery rates are highly variable with estimates fluctuating by more than one order of magnitude, from <5 years (very fast) to >250 years (very slow). Also, the development of microbial abundance and community diversity of biocrusts after disturbances is...

Biocrust effects on soil water infiltration and hydropedological processes have attracted increasing attention in dryland ecosystems, but are nevertheless subjected to great controversy. According to some scholars, infiltration was assumed to decrease due to repellency and to increase with the organic matter content due to its role in increasing ag...

【Objective】 Soil macropores play an important role in hyrdologic processes, such as rainfall infiltration, runoff occurrence, soil water movement and sediment deposition. As soil erosion varies with terrain (bottom and costa colpi of gully and the damland) in generation and development process, the soil forms under soil erosion vary too in soil tex...

The 30-year-old biological soil crusts dominated by mosses (hereafter moss crusts) and corresponding uncrusted soil (hereafter no crust) were sampled on loess soil and aeolian soil at 0-12 cm depth on the Loess Plateau of China. Afterwards, the hydrolase activities of the samples were measured, and their correlations with soil physicochemical prope...

To provide more insights into the responses of the soil seed bank and vegetation to human disturbance intensity, we selected four land use types, including: native grassland (no human disturbance), abandoned artificial grassland (light human disturbance), artificial grassland (moderate human disturbance), and farmland (severe human disturbance) in...

Various ecological functions of biocrusts are mostly determined by their bacterial and fungal abundance and community diversity, which has not yet been fully investigated. To provide more insights into this issue, we collected samples of moss biocrusts, fixed sand, and mobile sand from a watershed with semi-arid climate on the Loess Plateau of Chin...

In order to identify the influencing factors of wind erosion in black soil area of Northeast China,the wind erosion rates of black soil under different wind speeds(5~14m/s),soil water contents(2%~11%),and straw coverage rates(0~80%)were measured through a series of simulated wind experiments.Subsequently,the relationships between the wind erosion r...

The 30-year-old biological soil crusts dominated by mosses( hereafter moss crusts) and corresponding uncrusted soil( hereafter no crust) were sampled on loess soil and aeolian soil at 0-12 cm depth on the Loess Plateau of China. Afterwards,the hydrolase activities of the samples were measured,and their correlations with soil physicochemical propert...

The respiration of biological soil crusts is an important contribution to carbon cycling in arid and semiarid ecosystems, but soil crust responses to rainfall have not yet been fully investigated. In this study, we conducted a series of simulated rainfall experiments with different rainfall intensities (2, 4, 6, 10, 20, 30, 40 mm) for moss-dominate...

In order to provide references for the application of emergent plants in the remediation and restoration of aquatic ecosystems, a hydroponic experiment was conducted for Iris pseudacorus L. with different nitrate mass concentrations (i. e., 10.68, 23.88, 42.22, 63.33, 82.92, 97.13 mg·L-1). The effects of nitrate mass concentration in water on the g...

Biological soil crusts(BSCs) are very important components of land cover in arid and semiarid climate regions. The soil water repellency of BSCs is of great importance to their hydrological and ecological function, but have not yet sufficiently investigated. On the Loess Plateau of China, the duration, intensity, and indices of soil water repellenc...

The soil respiration rales of sandy soil (Usi Sandic Enlisols) and sandy loam soil (Los Orlhic Enlisols) wilh and wilhoul the coverage of moss-dominated biological soil cmsls (moss crusis) were measured by a portable CO2 analyzer (LI-840) in a small watershed on die I,ocss Plateau ol China. The effects of moss crusis on soil respiration were determ...

Three kinds of plants, including Lythrum salicaria L., Iris pseudacorus L., and Iris tectorum Maxim., were introduced as floating bed plants, and their water quality purification effects were studied in a artificial lake in Beijing, China. The results showed that the three kinds of plants, especially L. salicaria, grew rapidly. The biomass of L. sa...

The emergent plants Acorus calamus, Lythrum salicaria, and Scirpus tabernaemontani were exposed to atrazine for 15, 30, 45, and 60 days in a hydroponic system. Effects were evaluated investigating plant growth, chlorophyll (Chl) content, peroxidase (POD) activity, and malondialdehyde (MDA) content. Results showed that selected plants survived in cu...

Vegetative filter strip (VFS) can effectively reduce farmland runoff and its carrying pollution, which is a best management measure governing watershed agricultural non-point source pollution. Mathematical model is an effective tool to design vegetation filter strips. The effects of different widths (1, 2, 3 m) and different slops (3.3, 6.7, 10.0%)...