Across the globe, wind speed trends have shown a slight decline for in situ meteorological datasets. Yet few studies have assessed long-term wind speed trends for alpine regions or how such trends could influence snow transport and distribution. Alpine-region meteorological stations are sparsely distributed, and their records are short. To increase spatial and temporal coverage, use of modeled data is appealing, but the level of agreement between modeled and in situ data is unknown for alpine regions. Data agreement, temporal trends, and the potential effects on snow distribution were evaluated using two in situ sites in an alpine region [Niwot Ridge in Colorado and the Glacier Lakes Ecological Experiments Station (GLEES) in Wyoming] and the corresponding grid cells of the North American Regional Reanalysis (NARR). Temperature, precipitation, and wind speed variables were used to assess blowing-snow trends at annual, seasonal, and daily scales. The correlation between NARR and in situ datasets showed that temperature data were correlated but that wind speed and precipitation were not. NARR wind speed data were systematically lower when compared with in situ data, yet the frequency of wind events was captured. Overall, there were not many significant differences between NARR and in situ wind speed trends at annual, seasonal, and daily scales, aside from GLEES daily values. This finding held true even when trends presented opposite signatures and slopes, which was likely a result of low trend slopes. The lack of agreement between datasets prohibited the use of NARR to broaden analyses for blowing-snow dynamics in alpine regions.
Riparian trees and their annual growth rings can be used to reconstruct drought histories related to streamflow. Because the death of individual trees reduces competition for survivors, however, tree-ring chronologies based only on surviving trees may underestimate drought impacts. This problem can be addressed by calculating productivity at the stand scale to account for tree mortality and establishment. In the semi-arid Great Basin in the western United States, we calculated riparian wood production from 1946 to 2016 along a stream where most flow has been removed by a diversion pipeline since 1961. The water table was found to be generally below the root zone of cottonwoods (Populus angustifolia and P. angustifolia  trichocarpa) in the pipeline-dewatered reach but within it in reference reaches. To reconstruct forest productivity through time, we separately combined measurements of tree-ring basal area increment with either changing forest area from aerial photos or a census of cross-dated living and dead cottonwoods. Both approaches revealed productivity declines in the dewatered reach relative to adjacent reference reaches, and the decline accelerated in the 2000s. Tree-ring narrowing resulted in divergence between the dewatered reach and one reference reach within 5 years after diversion. However, the dewatered reach did not diverge from the other reference reach until 40 years later, when an unprecedented early 2000s atmospheric drought coupled with diversion to cause extensive cottonwood mortality. We conclude that dendrochronological investigations of forest response to environmental stress should incorporate stand dynamics and that the full impacts of flow diversion can be delayed for decades.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.