Identification of factors influencing the restoration of cyanobacteria-dominated biological soil crusts.

Biological soil crusts (BSCs) cover >35% of the Earth's land area and contribute to important ecological functions in arid and semiarid ecosystems, including erosion reduction, hydrological cycling, and nutrient cycling. Artificial rapid cultivation of BSCs can provide a novel alternative to traditional biological methods for controlling soil and water loss such as the planting of trees, shrubs, and grasses. At present, little is known regarding the cultivation of BSCs in the field due to lack of knowledge regarding the influencing factors that control BSCs growth. Thus, we determined the effects of various environmental factors (shade; watering; N, P, K, and Ca concentrations) on the growth of cyanobacteria-dominated BSCs from the Sonoran Desert in the southwestern United States. The soil surface changes and chlorophyll a concentrations were used as proxies of BSC growth and development. After 4 months, five factors were found to impact BSC growth with the following order of importance: NH4NO3 ≈ watering frequency>shading>CaCO3 ≈ KH2PO4. The soil water content was the primary positive factor affecting BSC growth, and BSCs that were watered every 5 days harbored greater biomass than those watered every 10 days. Groups that received NH4NO3 consistently exhibited poor growth, suggesting that fixed N amendment may suppress BSC growth. The effect of shading on the BSC biomass was inconsistent and depended on many factors including the soil water content and availability of nutrients. KH2PO4 and CaCO3 had nonsignificant effects on BSC growth. Collectively, our results indicate that the rapid restoration of BSCs can be controlled and realized by artificial "broadcasting" cultivation through the optimization of environmental factors

Interactive Effects of Moss-Dominated Crusts and Artemisia ordosica on Wind Erosion and Soil Moisture in Mu Us Sandland, China

To better understand the effects of biological soil crusts (BSCs) on soil moisture and wind erosion and study the necessity and feasibility of disturbance of BSCs in the Mu Us sandland, the effects of four treatments, including moss-dominated crusts alone, Artemisia ordosica alone, bare sand, and Artemisia ordosica combined with moss-dominated crusts, on rainwater infiltration, soil moisture, and annual wind erosion were observed. The major results are as follows. (1) The development of moss-dominated crusts exacerbated soil moisture consumption and had negative effects on soil moisture in the Mu Us sandland. (2) Moss-dominated crusts significantly increased soil resistance to wind erosion, and when combined with Artemisia ordosica, this effect became more significant. The contribution of moss-dominated crusts under Artemisia ordosica was significantly lower than that of moss-dominated crusts alone in sites where vegetative coverage > 50%. (3) Finally, an appropriate disturbance of moss-dominated crusts in the rainy season in sites with high vegetative coverage improved soil water environment and vegetation succession, but disturbance in sites with little or no vegetative cover should be prohibited to avoid the exacerbation of wind erosion

Soil organic matter content of the cyanobacterial crust layer in the treatments with the highest (21–24) and lowest (1–4) measured biomass.

<p>Note: Different letters above the bars indicate significant differences (<i>P</i><0.01) between treatments.</p

Soil nutrient content.

<p>Soil nutrient content.</p

Chlorophyll <i>a</i> content in each of the 32 treatments after 4 months of cultivation.

<p>Note: W10∶300 ml deionized water was added to each sample every 10 days. W5∶300 ml deionized water was added to each sample every 5 days. S: each sample was covered by a 60% shade cloth positioned 20 cm above the pot. NS: no shading. N: 2.10 g NH₄NO₃ added to each pot. NN: no NH₄NO₃ added to any pots. KP: 1.05 g KH₂PO₄ added to each pot. NKP: no H₂PO₄ added to any pots. Ca: 2.10 g CaCO₃ added to each pot. NCa: no CaCO₃ added to any pots. The capital letters indicate the different treatments, while different lower case letters above the bars indicate significant differences between any two treatments at <i>P</i><0.01.</p

Changes to the surface of moss crust under treatment 6,000 lx+1 watering/2 days-Knop during cultivation.

<p>A, B, and C, represent the status at day 0, day 20, and day 40, respectively.</p

Relationship between chlorophyll <i>a</i> and exopolysaccharides (EPS).

<p>Relationship between chlorophyll <i>a</i> and exopolysaccharides (EPS).</p

Key Factors Influencing Rapid Development of Potentially Dune-Stabilizing Moss-Dominated Crusts

<div><p>Biological soil crusts (BSCs) are a widespread photosynthetic ground cover in arid and semiarid areas. They have many positive ecological functions, such as increasing soil stability, and reducing water and wind erosion. Using artificial technology to achieve the rapid development of BSCs is expected to become a low-cost and highly beneficial ecological restoration measure. In the present study, typical moss-dominated crusts in a region characterized by mobile dunes (Mu Us Sandland, China) were collected, and a 40-day cultivation experiment was performed to investigate key factors, including watering frequency, light intensity and a nutrient addition, which affect the rapid development of moss crusts and their optimal combination. The results demonstrated that watering frequency and illumination had a significant positive effect (P=0.049, three-factor ANOVA) and a highly significant, complicated effect (P=0.000, three-factor ANOVA), respectively, on the plant density of bryophytes, and a highly significant positive effect on the chlorophyll <i>a</i> and exopolysaccharide contents (P=0.000, P=0.000; P=0.000, P=0.000; one-way ANOVA). Knop nutrient solution did not have a significant positive but rather negative effect on the promotion of moss-dominated crust development (P=0.270, three-factor ANOVA). Moss-dominated crusts treated with the combination of moderate-intensity light (6,000 lx) + high watering frequency (1 watering/2 days) - Knop had the highest moss plant densities, while the treatment with high-intensity light (12,000 lx) + high watering frequency (1 watering/2 days) + Knop nutrient solution had higher chlorophyll <i>a</i> contents than that under other treatments. It is entirely feasible to achieve the rapid development of moss crusts under laboratory conditions by regulating key factors and creating the right environment. Future applications may seek to use cultured bryophytes to control erosion in vulnerable areas with urgent needs.</p></div

Dynamic characteristics of the growth rates of moss plant densities for four treatments under 2000 lx, 6000 lx, and 12000 lx illumination intensities, respectively.

<p>The values were presented as the Mean ± SE.</p

Treatments used in the cyanobacteria-dominated crust cultivation experiments.

<p>Note: W10∶300 ml deionized water was added to each sample every 10 days. W5∶300 ml deionized water was added to each sample every 5 days. S: each sample was covered by a 60% shade cloth at 20 cm above the pot. NS: no shading. N: 2.10 g NH₄NO₃ added to each pot. NN: no NH₄NO₃ added to any pots. KP: 1.05 g KH₂PO₄ added to each pot. NKP: no H₂PO₄ added to any pots. Ca: 2.10 g CaCO₃ added to each pot. NCa: no CaCO₃ added to any pots.</p