Variation of Seed Banks among Ecological States in the Chihuahuan Desert: Implications for Restoration

TitleVariation of Seed Banks among Ecological States in the Chihuahuan Desert: Implications for Restoration
Publication TypeConference Paper
Year of Publication2019
AuthorsRomig KB, James DK, Bestelmeyer BT, Maxwell CJ, Brown J, Salley SW
Conference Name72nd Society for Range Management International Meeting
Date Published02/2019
PublisherSociety for Range Management Meeting Abstracts
Conference LocationMinneapolis, Minnesota
ARIS Log Number361625
Abstract

State transitions involving the encroachment of shrubs and loss of herbaceous species are known to be highly persistent in the Chihuahuan Desert, even when disturbances are reduced and shrubs are removed. The existing seedbank in these soils is poorly documented and seed bank limitation might constrain the recovery of historical herbaceous communities. From 2015 to 2017 we conducted a germinable seed bank study by collecting a total of 258 soil samples (each measuring 796 cm3) from randomly selected sites on 190,000 acres of the Jornada Experimental Range in Southern New Mexico. Sites were stratified by ecological states within each of the 10 ecological sites found on the range. Over a two-year period, these samples were provided ample water and monitored in greenhouse conditions. The soil yielded 12,777 seedlings from 159 species of vascular plants. Variance partitioning and redundancy analysis showed that ecological site and state explains significantly more variability in germinable seeds by species than spatial structure alone (15.17% and 5.94%, respectively; p=0.001); however, a considerable amount of unexplained variability exists. Seed banks in degraded states within ecological sites were generally limited with respect to desirable (native perennial) species with the exception of mesa dropseed grass (Sporobolus flexuosus) which occurred in 61.24% of the sites and 39.54% of the seedlings identified. Additionally, mesa dropseed is more widely dispersed than other desirable grass species within ecological sites. Our results suggest that seed bank limitation may contribute to the persistent absence of key herbaceous species. The prevalence of mesa dropseed in the seed bank – even where it is not abundant aboveground – suggests that establishment limitations including soil surface degradation and herbivory need to be overcome to trigger mesa dropseed increase, but that seeding may not be necessary.