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Abstract Detail


Turk, Tyler [1], Faist, Akasha [1].

Connectivity and Seed Availability: the Role of Seeds in Dryland State Transitions.

Drylands globally make up 41% of the terrestrial land surface area. These systems have faced widespread degradation due to a variety of factors including climatic events and land use. Woody plant encroachment into arid grasslands is one widespread phenomenon often associated with dryland degradation. This encroachment leads to structural and functional changes in the system which facilitate positive feedback loops that further reinforce the shrubland state. For instance, shrub encroached areas are characterized by large, bare plant-interspaces where wind and water erosion occur, redistributing resources including sediment, seeds and litter. This results in greater nutrient availability and infiltration under shrub canopies as well as deficient interspaces where the ability of herbaceous plants to establish is greatly restricted. As encroachment worsens and presence of bare ground increases, the interspaces become long connected pathways through which abiotic transport occurs. Sediment deposition, in turn, occurs at increasingly larger scales, further separating deposited resources from the source. An emerging framework to understand dryland dynamics describes dry-landscapes with many large, bare plant-interspaces, and movement of materials at large extents, as having a high degree of connectivity. Restoration in drylands has often incorporated methods to reduce the length of connectivity pathways to mitigate erosion and retain resources locally which promote herbaceous plant growth. This can be achieved in areas with high aeolian transport using structures known as connectivity modifiers (ConMods). Seeds are an important resource captured by ConMods: quantifying the seeds captured in ConMods will allow us to gain insight into seed movement on the landscape. For this research I quantified the amount of sediment and number of germinable seeds captured in ConMods at two long term research sites with variable grass and shrub cover at the Jornada Experimental Range in the northern Chihuahuan Desert by performing a seedling emergence study on the materials collected over one growing season. I also conducted a short-term seed predation study to determine whether removal by granivores was contributing to patterns of seed availability. I found that seed movement was occurring broadly across the landscape. However, sediment and seed movement did not have similar relationships to large-scale connectivity metrics and patches with altered connectivity. My research suggests that successful use of ConMods as restoration tools necessitates consideration of current and past vegetation, and that increased seed removal by rodent granivores in shrublands may be further reducing seed availability.

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1 - New Mexico State University, Department of Animal and Range Sciences, Las Cruces, NM, 88003, USA

shrub encroachment
state transitions

Presentation Type: Oral Paper
Session: ECO6, Ecology: Restoration and Conservation
Location: /
Date: Thursday, July 22nd, 2021
Time: 3:30 PM(EDT)
Number: ECO6003
Abstract ID:717
Candidate for Awards:None

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