Grass-shrub interactions at the core of woody plant encroachment – Contributions to conceptual models, process, and mechanism

Authors: Browning, Dawn; PREDICK, KATHERINE - Arizona Sonoran Desert Museum; ARCHER, STEVEN - University Of Arizona

Submitted to: Society for Range Management
Publication Type: Abstract Only
Publication Acceptance Date: 1/29/2023
Publication Date: 2/16/2023
Citation: Browning, D.M., Predick, K., Archer, S.R. 2023. Grass-shrub interactions at the core of woody plant encroachment – Contributions to conceptual models, process, and mechanism. Society for Range Management. Abstract.

Interpretive Summary: Rangeland managers require timely, reliable, and easily interpretable information about their land to inform decisions. One of the biggest challenges managers face is the high temporal variability in plant establishment, growth, and reproduction. Phenology data that describe the timing of plant seasonal stages offer an incredibly powerful and underutilized opportunity to increase management effectiveness through precision timing. The data are easier to collect than ever using field observation, phenocams and satellite imagery. On-line tools make metric calculation simple, while increasingly sophisticated algorithms are facilitating the integration of different sources of phenological data. The results of these integrated analyses will increasingly allow managers in the private and public sectors to target management interventions, including grazing, herbicide applications and prescribed fire, with pinpoint accuracy in both space and time.

Technical Abstract: Plant phenology—the timing of seasonal life cycle events—is a primary control on ecosystem productivity and an integrative indicator of species’ responses to the environment. Plant phenology data can be used to design better management systems by adjusting the timing of grazing, fire and other disturbances relative to the growth stage of key species and in planning restoration activities such as herbicide applications or targeted grazing. Repeated observations needed to understand phenology can be collected at various spatial scales with a variety of methods from field-based observations of individual plants to broad-scale observations of landscape “greenness” from satellite imagery. Digital cameras mounted on towers (phenocams) provide a more cost-effective way to collect data to capture vegetation “greenness.” Phenocam greenness values are used to generate plant canopy- and community-level metrics in real-time for a fraction of the cost of on-the-ground field observations. Phenocam greenness metrics also serve to link plant- or community-scale phenology observations collected in the field with those from satellite remote sensing and can reveal the plant species or functional groups contributing to satellite NDVI. Phenocam image time series also help interpret rangeland monitoring data by placing data in the context of inter- and intra-annual variability.