Topoedaphic constraints on woody plant cover in a semi-arid grassland

The proliferation of unpalatable woody plants at the expense of perennial grasses in recent decades has challenged our ability to manage rangelands. While there is substantial research documenting shrub proliferation, we know little about the maximum potential shrub cover for a given topoedaphic setting. To better understand the environmental controls over and constraints on shrub cover, we used high spatial resolution imagery to classify cover of a shrub (Prosopis velutina, velvet mesquite) proliferating in a Sonoran Desert grassland in southern Arizona, USA and explored how maximum shrub cover varies across ecological sites and topoedpahic settings. While the upper limit of shrub cover at the continental-scale is constrained by mean annual precipitation (MAP), our results show that this maxima has a wide range variously dictated by elevation, slope inclination/aspect, soil texture, and rainfall re-distribution. Within the watershed, maximum potential shrub cover ranged from < 3% to 45% with the magnitude and direction of topoedaphic influences varying significantly between landscape components. For example, topoedaphic properties enhanced precipitation (PPT) effectiveness and elevated maximum shrub cover above what might be predicted based on MAP alone on some ecological sites, but reduced PPT effectiveness and constrained shrub cover to levels below what would be predicted from MAP on other sites. Knowledge of upper limits of shrub cover at the within-watershed scale will strengthen dynamic vegetation models, serve as a basis to better design field and modeling experiments and decision support tools, and provide a spatial context indicators for prioritizing conservation/land management goals and objectives. © 2023 The Author(s)Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Assessing vegetation response to multi-scalar drought across the mojave, sonoran, chihuahuan deserts and apache highlands in the Southwest United States

Understanding the patterns and relationships between vegetation productivity and climatic conditions is essential for predicting the future impacts of climate change. Climate change is altering precipitation patterns and increasing temperatures in the Southwest United States. The large-scale and long-term effects of these changes on vegetation productivity are not well understood. This study investigates the patterns and relationships between seasonal vegetation productivity, represented by Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI), and the Standardized Precipitation Evapotranspiration Index (SPEI) across the Mojave, Sonoran, and Chihuahuan Deserts and the Apache Highlands of the Southwest United States over 16 years from 2000 to 2015. To examine the spatiotemporal gradient and response of vegetation productivity to dry and wet conditions, we evaluated the linear trend of different SPEI timescales and correlations between NDVI and SPEI. We found that all four ecoregions are experiencing more frequent and severe drought conditions in recent years as measured by negative SPEI trends and severe negative SPEI values. We found that changes in NDVI were more strongly correlated with winter rather than summer water availability. Investigating correlations by vegetation type across all four ecoregions, we found that grassland and shrubland productivity were more dependent on summer water availability whereas sparse vegetation and forest productivity were more dependent on winter water availability. Our results can inform resource management and enhance our understanding of vegetation vulnerability to climate change. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Structural tuning of the fluorescent protein iLOV for improved photostability

Background: iLOV is a fluorescent flavoprotein engineered from the plant blue light receptor phototropin. &lt;p/&gt;Results: Structures reveal altered protein-chromophore interactions within the flavin-binding cavity of iLOV when compared with its progenitors. Directed evolution further anchored the chromophore to increase iLOV photostability by an order of magnitude. &lt;p/&gt;Conclusion: Improving iLOV photostability by constraining its fluorophore establishes a framework for fine-tuning fluorescence. &lt;p/&gt;Significance: Enhanced photostability increases iLOV utility as an oxygen-independent fluorescent reporter