Moss-dominated biocrusts decrease soil moisture and result in the degradation of artificially planted shrubs under semiarid climate
2017
Xiao, Bo | Hu, Kelin
The relationships between biocrusts and shrubs in semiarid areas, are of great importance, however, not yet sufficiently investigated. It is unknown whether or not biocrusts will decrease soil moisture and result in the degradation of artificially planted shrubs in semiarid climates. In a semiarid watershed on the Loess Plateau of China, we selected 18 sampling sites in artificial shrublands and measured at each the soil moisture from 0 to 200cm depth under bare land, moss-dominated biocrusts, artificially planted Artemisia ordosica, A. ordosica with biocrusts, and dead A. ordosica with biocrusts. We also estimated the water-holding capacity and infiltrability of the soil with and without biocrusts. The A. ordosica with biocrusts had 24.4% lower biomass and 18.9% lower leaf area index than those without biocrusts, suggesting negative effects of biocrusts on these shrubs. Moreover, the biocrusts underneath A. ordosica decreased soil moisture 14.8% on average (2.6% vs. 3.1%; p<0.01) due to their significant higher water-holding capacity (≥21.6%) and lower infiltrability (50.4%), compared to the area without biocrusts. Most importantly, the area with biocrusts and dead A. ordosica had similar soil moisture to the area with biocrusts and live A. ordosica, suggesting that the decreased soil moisture under the biocrusts persists after the death of A. ordosica. Our results suggest that biocrusts reduce soil water resources available to the artificially planted shrubs, thus increasing the risks of shrub mortality and further land degradation. The high coverage of moss-dominated biocrusts appears to be a dominant factor in soil moisture variations in artificial shrublands under semiarid climates, making the soil water balance more vulnerable in this region.
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