Background

The intergovernmental panel on climate change reported in 2014 that over a period of 1976-2012 snow cover in the Northern Hemisphere has decreased by 11.7% per decade in the month of June (IPCC, 2014). Snowpack storage is crucial for headwater regions, and early water release could lead to water resource management and ecosystem function issues (Elias et al., 2015; Demaria et al., 2016). It has been predicted that snowmelt timing in the western U.S. could be enhanced by as much as two months by the end of this century (Rauscher et al., 2008), while a more recent study (Clow et al., 2016) reported advanced snowmelt offset by 1-2 weeks over the past two decades in Colorado, which is an essential headwater state. Shorter periods of snow cover and earlier water release have the potential to affect several aspects of ecosystem health in mountainous environments such as water availability and storage (Barnett et al., 2005), plant phenology and succession (Livensperger et al., 2016), and the soil microbial community structure (de Vries and Griffiths, 2018). With several aspects of the environment impacted by shifts in snowmelt timing, it is helpful to have a reliable and reproducible method that enables paired comparisons of enhanced and natural snowmelt across researchers and geographic regions.

A variety of methods have been used to manipulate snowmelt rates. Some have used a shovel to remove snow depth (Wipf et al., 2006), while others implemented more involved methods such as infrared heating sources (Harte et al., 1995; Bokhorst et al., 2008), or distributing black sand across the snow surface area (Steltzer et al., 2009; Blankinship et al., 2018). In contrast to these methods, the protocol described here is a noninvasive, low cost, and easily reproducible method that increases the absorption of solar radiation with a permeable black fabric deployed directly on the snow surface (Walsh et al., 2003; Steltzer et al., 2009). In addition, the method enables paired contrasts between accelerated and natural snowmelt processes in adjacent plots with conserved water equivalents. In contrast to black sand applications, the fabric is removed once the snow has fully melted and does not leave residual non-native material in associated soils. This refined protocol builds upon insights from past studies using permeable fabric covers (Steltzer et al., 2009) with a goal of increasing method utility, adoption and reproducibility. More recent efforts from 2017-2019 in Crested Butte, Colorado have documented snowmelt advancement of 14-23 days when contrasting manipulated and control plots at an elevation of 3,170 meters (Figure 1). The protocol and equipment explained below allows others to establish, deploy and monitor several aspects of the snowmelt process and can be adapted for a variety of environmental studies including but not limited to plant litter decay processes, geochemical shifts in the hydrosphere, and local plant phenology and growth.