Research ArticleECOLOGY

Biocrust as one of multiple stable states in global drylands

See allHide authors and affiliations

Science Advances  25 Sep 2020:
Vol. 6, no. 39, eaay3763
DOI: 10.1126/sciadv.aay3763
  • Fig. 1 Illustration of ecosystem states used in this study.

    Biocrust state (pink), high biocrust cover (>50%), and low vascular plant cover (<10%); bare soil state (green), both biocrust and vascular plant covers are low (<10%); vascular plant state (black), low in biocrust cover (<10%) and high in vascular plant cover (>50%). Other situations belong to the “mixed state” (blue).

  • Fig. 2 The distribution of biological soil crust (biocrust) sites in global drylands.

    Different colors outline four subtypes of drylands (red, hyperarid land; pink, arid land; green, semiarid land; and light blue, dry subhumid land). Deep blue points show distributions of biocrust data compiled in this study.

  • Fig. 3 Frequency distribution of biological soil crust (biocrust) cover.

    Frequency distribution of biological soil crust (biocrust) cover under the entire (A) or divided (B to G) range of the AI. (A) “Partial data” refer to the data points where vascular plant cover data were also available. Dashed squares show different modes of frequency distribution. (B to G) Different colors of squares indicate different states corresponding to Fig. 1 (green, bare soil state; red, biocrust state; blue, biocrust-vascular mixed state; and black, vascular plant state). Squares with other colors denote the intermediate states. Note that vegetation cover data have been arcsine–square root transformed.

  • Fig. 4 Stability landscape of biological soil crust (biocrust) cover in driver (AI) space.

    Green and white in the bottom panel describe the local maxima and minima of the stability landscape, respectively. The solid and dashed lines outline the stable (i.e., local minima) and unstable (i.e., local maxima) states. Green, blue, pink, and black segments denote the bare soil, mixed, biocrust, and vascular plant states, respectively. The red ball in the bottom panel denotes the “cross” point where two branches of stable states cross. Two light blue shadow walls on the bottom panel indicate the values delimiting different states (refer to the “Data compilation” section in Materials and Methods). The gray-black walls and balls on the top show attraction basins and local minima of ecosystems as a function of aridity. Different colors of balls correspond to different states over the range of aridity (refer to Fig. 1). Biocrust cover data have been arcsine–square root transformed.

  • Fig. 5 Comparison of the “crossed” and “classic” fold bifurcations.

    (A) The “crossed” fold bifurcation. (B) The “classic” fold bifurcation. Solid and dashed lines signify the stable and unstable states, respectively. Lines and arrows in the same color demonstrate the changes of system state as the driver variable increases or decreases. The bottom panels demonstrate the potential of system state as a function of the driver variable. Lines with different colors indicate different stable states.

  • Fig. 6 Illustration of the effects of vascular plants on biocrusts.

Supplementary Materials

  • Supplementary Materials

    Biocrust as one of multiple stable states in global drylands

    Ning Chen, Kailiang Yu, Rongliang Jia, Jialing Teng, Changming Zhao

    Download Supplement

    This PDF file includes:

    • Figs. S1 to S6
    • Tables S1 to S4

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article