Snowmelt timing alters shallow but not deep soil moisture in the Sierra Nevada

Abstract

Roughly one-third of the Earth's land surface is seasonally covered by snow. In many of these ecosystems, the spring snowpack is melting earlier due to climatic warming and atmospheric dust deposition, which could greatly modify soil water resources during the growing season. Though snowmelt timing is known to influence soil water availability during summer, there is little known about the depth of the effects and how long the effects persist. We therefore manipulated the timing of seasonal snowmelt in a high-elevation mixed-conifer forest in a Mediterranean climate during consecutive wet and dry years. The snow-all-gone (SAG) date was advanced by 6 days in the wet year and 3 days in the dry year using black sand to reduce the snow surface albedo. To maximize variation in snowmelt timing, we also postponed the SAG date by 8 days in the wet year and 16 days in the dry year using white fabric to shade the snowpack from solar radiation. We found that deeper soil water (30-60 cm) did not show a statistically significant response to snowmelt timing. Shallow soil water (0-30 cm), however, responded strongly to snowmelt timing. The drying effect of accelerated snowmelt lasted 2 months in the 0-15 cm depth and at least 4 months in the 15-30 cm depth. Therefore, the legacy of snowmelt timing on soil moisture can persist through dry periods, and continued earlier snowmelt due to climatic warming and windblown dust could reduce near-surface water storage and availability to plants and soil biota.

Anthropogenic warming has increased drought risk in California

“…35), and continued global warming is likely to result in earlier snowmelt and increased rain-to-snow ratios (35,36). As a result, the peaks in California's snowmelt and surface runoff are likely to be more pronounced and to occur earlier in the calendar year (35,36), increasing the duration of the warm-season low-runoff period (36) and potentially reducing montane surface soil moisture (37). Although these hydrological changes could potentially increase soil water availability in previously snow-covered regions during the cool low-ET season (34), this effect would likely be outweighed by the influence of warming temperatures (and decreased runoff) during the warm high-ET season (36,38), as well as by the increasing occurrence of consecutive years with low precipitation and high temperature (Fig.…”

Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale

“…Comparing the ARF and no-ARF scenarios, we see a general shift in the discharge, with the ARF scenario producing greater discharge early in the season, and having less discharge after June. Such a shift in seasonal water balance will potentially have impacts on soil moisture and agriculture (Blankinship et al, 2014), as well as on regional climate (Qian et al, 2011). While we recognize significant uncertainties associated with conceptual hydrologic modelling that may impact the applicability of these results (Beven and Binley, 1992; see also the uncertainty discussion in Sect.…”

Natural selection on floral morphology can be influenced by climate

“…B 282: 20150178 trait [29]. For traits with 10 or more years of data, we examined the environmental sensitivity of selection [30] by calculating the correlation between the selection measure and either of two environmental variables: (i) summer precipitation between 1 June and 15 July at Gothic, CO (National Atmospheric Deposition Program CO10), the period when Ipomopsis is developing inflorescences and prior to most of our floral measurements in late July and early August, or (ii) the date of first snowmelt at Gothic, CO, 8 km from our common gardens and at a similar elevation near 2900 m. Later snowmelt is associated with higher soil moisture in mountainous regions, with effects lasting for two to four months after snowmelt, at least in the Sierra Nevada [31]. We also compared selection in years with versus without hawkmoths.…”