An official website of the United States government
Snowmelt is a critical water resource in the Sierra Nevada impactingpopulations in California and Nevada. In this region, forest managersuse treatments like selective thinning to encourage resilient ecosystemsbut rarely prioritize snowpack retention due to a lack of simplerecommendations and the importance of other management objectives likewildfire mitigation and wildlife habitat. We use light detection andranging (lidar) data collected over multiple snow accumulation seasonsin the Sagehen Creek Basin, central Sierra Nevada in California, USA, toinvestigate how snowpack accumulation and ablation are affected byforest structure metrics at coarse, stand-scales (e.g., fraction ofvegetation, or fVEG) and fine, tree-scales (e.g., a modified leaf areaindex, and the ratio of gap-width to average tree height). Using a newlydeveloped lidar point cloud filtering method and an “open-areareference” approach, we show that for each 10% decrease in fVEG thereis a ~30% increase in snow accumulation and a~15% decrease in ablation rate at the Sagehen fieldsite. To understand variability around these relationships, we use arandom forest analysis to demonstrate that areas with fVEG greater than~30% have the greatest potential increased accumulationresponse after forest removal. This spatial information allows us toassess the utility of completed and planned forest restorationstrategies in targeting areas with the highest potential snowpackresponse. Our new lidar processing methods and reference-based approachare easily transferrable to other areas where they could improvedecision support and increase water availability from landscape-scaleforest restoration projects.
more »
« less
On the use of a snow aridity index to predict remotely sensed forest productivity in the presence of bark beetle disturbance: SNOW ARIDITY AND TREE DEATH PREDICT NDVI
- Award ID(s):
- 1637686
- PAR ID:
- 10047540
- Date Published:
- Journal Name:
- Water Resources Research
- Volume:
- 53
- Issue:
- 6
- ISSN:
- 0043-1397
- Page Range / eLocation ID:
- 4891 to 4906
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
ABSTRACT It is unclear how environmental change influences standing genetic variation in wild populations. Here, we characterised environmental conditions that protect versus erode polymorphic chemical defences inBoechera stricta(Brassicaceae), a short‐lived perennial wildflower. By manipulating drought and herbivory in a 4‐year field experiment, we measured the effects of driver variation on vital rates of genotypes varying in defence chemistry and then assessed interacting driver effects on total fitness (estimated as each genotype's lineage growth rate,λ) using demographic models. Drought and herbivory interacted to shape vital rates, but contrasting defence genotypes had equivalent total fitness in many environments. Defence polymorphism thus may persist under a range of conditions; however, ambient field conditions fall close to the boundary of putatively polymorphic environment space, and increasing aridity may drive populations to monomorphism. Consequently, elevated intensity and/or frequency of drought under climate change may erode genetic variation for defence chemistry inB. stricta.more » « less
-
Abstract High nighttime urban air temperatures increase health risks and economic vulnerability of people globally. While recent studies have highlighted nighttime heat mitigation effects of urban vegetation, the magnitude and variability of vegetation-derived urban nighttime cooling differs greatly among cities. We hypothesize that urban vegetation-derived nighttime air cooling is driven by vegetation density whose effect is regulated by aridity through increasing transpiration. We test this hypothesis by deploying microclimate sensors across eight United States cities and investigating relationships of nighttime air temperature and urban vegetation throughout a summer season. Urban vegetation decreased nighttime air temperature in all cities. Vegetation cooling magnitudes increased as a function of aridity, resulting in the lowest cooling magnitude of 1.4 °C in the most humid city, Miami, FL, and 5.6 °C in the most arid city, Las Vegas, NV. Consistent with the differences among cities, the cooling effect increased during heat waves in all cities. For cities that experience a summer monsoon, Phoenix and Tucson, AZ, the cooling magnitude was larger during the more arid pre-monsoon season than during the more humid monsoon period. Our results place the large differences among previous measurements of vegetation nighttime urban cooling into a coherent physiological framework dependent on plant transpiration. This work informs urban heat risk planning by providing a framework for using urban vegetation as an environmental justice tool and can help identify where and when urban vegetation has the largest effect on mitigating nighttime temperatures.more » « less
-
Abstract Snow is a vital part of water resources, and sublimation may remove 10%–90% of snowfall from the system. To improve our understanding of the physics that govern sublimation rates, as well as how those rates might change with the climate, we deployed an array of four towers with over 100 instruments from NCAR’s Integrated Surface Flux System from November 2022 to June 2023 in the East River watershed, Colorado, in conjunction with the U.S. Department of Energy’s Surface Atmosphere Integrated Field Laboratory (SAIL) and the National Oceanic and Atmospheric Administration (NOAA)’s Study of Precipitation, the Lower Atmosphere and Surface for Hydrometeorology (SPLASH) campaigns. Mass balance observations, snow pits, particle flux sensors, and terrestrial lidar scans of the evolving snowfield demonstrated how blowing snow influences sublimation rates, which we quantified with latent heat fluxes measured by eddy-covariance systems at heights 1–20 m above the snow surface. Detailed temperature profiles at finer resolutions highlighted the role of the stable boundary layer. Four-stream radiometers indicated the important role of changing albedo in the energy balance and its relationship to water vapor losses. Collectively, these observations span scales from seconds to seasons, from boundary layer turbulence to valley circulation to mesoscale meteorology. We describe the field campaign, highlights in the observations, and outreach and education products we are creating to facilitate cross-disciplinary dialogue and convey relevant findings to those seeking to better understand Colorado River snow and streamflow.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1002/2016WR019887
