Patterns of vegetation along a spatiotemporal gradient on shoreline strands of a desert basin lake

Shoreline strands of Mono Lake, California, show clear evidence ofregular temporal change in plant communities and the soils associated with themalong a primary successional sere, contradicting the traditional notion thatsuccession sensu stricto does not occur in aridenvironments. We documented spatial patterns, and inferred temporal patternsfrom aerial photographs taken each decade from 1930, in communities ofperennialshrubs and in characteristics of the physical environment in sand-duneand shoreline ecosystems on the north shore of Mono Lake, a receding terminalQuaternary lake in the Great Basin desert of the United States that is highlysaline and alkaline. Our study plot was aligned with an extreme physicochemicalgradient, representing a primary sere beginning with the historic, acceleratedregression of Mono Lake since 1940 and ending with upland surfaces exposed bylake regression between 500 and 1000 years ago. Four shrub species composedmost of the 7–11% percent coverof perennial vegetation: populations of Sarcobatusvermiculatus extended farthest toward the lake and colonized themostrecently exposed and toxic surfaces; populations of Chrysothamnusnauseosus, Tetradymia tetrameres, andC. viscidiflorus ended at increasing distances (inthis order) from the lake shore, reflecting each species'respectivelylower tolerance of soil salinity, alkalinity, and toxic soil elements ratherthan the ability to disperse. Values of soil variables that decrease plantgrowth and establishment (EC, pH, B, S) were lower in oldersubstrates, in the upper soil horizons, and at increasing distances from thelake, reflecting leaching and other pedogenic processes with time. Individualsof S. vermiculatus appeared to promote dune building bytolerating burial, enhancing their own growth and establishment, and catchingmore sand. We hypothesize that this process also facilitates the establishmentof less stress tolerant species. Plant nutrients (N, P) decreasedwithdepth, evidence of progressive soil enrichment by litter and leaf fall. Thusboth allogenic processes (weathering of parent material) andautogenicprocesses (facilitation in particular) resulting fromplant-environment interactions occurred and contributed to ecosystemchange in this extreme primary sere, adhering to the strictest definition ofsuccession.