Ecological state transitions involving the encroachment of shrubs and loss of herbaceous species are common and highly persistent in the Chihuahuan Desert, even when disturbances are reduced and shrubs are removed. The existing seed bank in these soils is poorly documented and seed bank limitation may constrain the recovery of historical herbaceous communities. Seed bank quantification could enhance our understanding of future shift implications in ecological sites and states. Addressing these core issues of how biodiversity may change in drylands across degradation levels, three primary questions were posited:
- What can the seed bank tell us about biodiversity in the Chihuahuan Desert?
- How does the seed bank differ by ecological site and the different states (levels of degradation) in those sites?
- What does the seed bank tell us about grassland to shrubland shifts?
From 2015 to 2017 a germinable seed bank study was conducted 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. Collection sites were stratified by ecological states within each of the ten ecological sites found on the range. Over a two-year period, these samples were provided ample water and monitored in greenhouse conditions.
Results/Conclusions
The soil yielded 12,777 seedlings from 159 species of vascular plants. Mean values of germinated seed for ecological sites and states exhibited high biodiversity. Species identified were mostly native perennials, many of them not displayed in their aboveground vegetative counterparts.
Seed banks in the Chihuahuan desert have limited ability to express themselves as degradation progresses through ecological states and with climatic shifts. Biodiversity remains in degraded sites as soil seed caches. Seeding may not be necessary for restoration efforts.