Identifying thresholds in pattern-process relationships: a new cross-scale interactions experiment at the Jornada Basin LTER

TitleIdentifying thresholds in pattern-process relationships: a new cross-scale interactions experiment at the Jornada Basin LTER
Publication TypeConference Proceedings
Year of Publication2012
AuthorsPillsbury FC, Peters DC, Okin GS, Duniway M.C., Anderson JP, Sala O.E, Vivoni ER, Herrick JE, Havstad K
Conference Name2012 LTER All Scientists Meeting
Volumep. 43
Date Published09/2012
Publisher LTER All Scientists Meeting
Conference LocationEstes Park, Colorado
ARIS Log Number286001
Abstract

Interactions among ecological patterns and processes at multiple scales play a significant role in threshold behaviors in arid systems. Black grama grasslands and mesquite shrublands are hypothesized to operate under unique sets of feedbacks: grasslands are maintained by fine-scale biotic feedbacks promoting the retention of plant-available water that promotes grass establishment and persistence, while shrublands are maintained by broader-scale abiotic feedbacks promoting an increase in bare ground connectivity and redistribution of material by wind that promote shrub expansion. We recently established a large-scale, long-term manipulative experiment to test these hypotheses in order to identify the threshold distribution of bare gaps beyond which plant-scale processes are overwhelmed by abiotic drivers to shift grassland system into shrublands. In a 2 x 2 factorial design at 15 experimental blocks arrayed along an existing gradient of bare ground connectivity, we manipulated a plant-scale biotic process and a patch-scale abiotic process to measure the relative importance of these controls on primary production, soil water dynamics, and other ecological responses. All mesquite shrubs were killed to manipulate plant-scale competition for resources. We installed small fence-like structures (connectivity modifiers, or ConMods) to manipulate bare ground connectivity of surface soil and plant material by wind at a patch scale. This experiment will improve understanding of the role of cross-scale interactions that lead to threshold dynamics across mixed lifeform ecotones.