Identification of Factors Influencing the Restoration of Cyanobacteria-Dominated Biological Soil Crusts

Chongfeng Bu,Mingguo Zheng,Yongsheng Yang,Shufang Wu,Brett Neilan

doi:10.1371/journal.pone.0090049

Abstract

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.

Highlights

Biological soil crusts (BSCs) are highly complex communities composed of mosses, cyanobacteria, lichens, bacteria, and fungi with soil particles [1,2]
Based on crust sampling in the field, lab cultivation, and the investigation of biomass and surface changes, the present study examined the effects of light intensity, watering frequency, and nutrient amendment of N, P, K, and CaCO3 amendment (Ca) on the development of cyanobacteria-dominated BSCs located in the Sonoran Desert in the southwestern United States
We found that higher K and Ca levels did not benefit the development of cyanobacterial crusts, which contrasts with the results of a previous report [20]

Summary

Introduction

Biological soil crusts (BSCs) are highly complex communities composed of mosses, cyanobacteria, lichens, bacteria, and fungi with soil particles [1,2]. BSCs are known to enrich soil nutrients, enhance soil stability, and reduce soil erosion by wind and water [7,8,9]. In the Loess Plateau, moss-dominated BSC were shown to reduce water runoff and sediment loss from soils by .30% and .80%, respectively [10]. In a separate wind tunnel experiment, moss- and cyanobacteria-dominated BSCs reduced the wind erosion rate of soils by more than 90% as compared to uncovered desert soils [11]. Attempts have been made to establish artificial BSCs to promote soil stability and to reduce losses due to wind and water erosion. The average thickness of this artificial BSC ranged from 2.23 to 5.36 mm, with coverage of 70%, after 3 years of growth, suggesting that this approach may have long-term positive effects on soil stability [17]

Methods

Results

Discussion

Conclusion