Abstract
The role of forest stands in estimating the snow water equivalent (SWE) over large areas is mainly related to the physical barrier they create, which make both direct and indirect measurements more difficult, and to the influence they have on the properties of the snowpack.The goal of the 5th SWE INTERCOMPARISON meeting, hold in Bolzano (BZ) on 18 and 19 March 2019, was to test a new survey scheme for field teams in order to improve the estimation of SWE in alpine environments, as well as to investigate the relationship between degree of forest cover and SWE. The work required a day of field surveys, with the aim of acquiring as much data as possible over a wide area. The survey scheme was designed based on the already available literature, according to which forest cover determines a reduction in snow height (HS) compared to a non-forest area under the same topographical conditions. The samplingsites were identified in the Ski Center Latemar area (BZ) using orthophotos, to include forest areas with different degree of cover and open field areas. In total, 79 sites were investigated, collecting 22 values of HS [cm], 1 value of snow density [kg m-3] and 1 value of stand density [number of trees ha-1] for each measurement site. Overall, the altitudinal range is between 1520 and 2490 m a.s.l., the stand density between 0 and 2546 trees ha-1and the SWE between 4 and 386 mm. The collected data allow coupling 51 values of HS in the forest with as many values outside the forest and to calculate the relative delta HS (∆HS = HSforest -HSopen field). In 43 cases this difference is negative, while in 8 cases it is positive (more snow in the forest compared to the open field). On average, the reduction of HS in the forest is 27%. In terms of SWE, the reduction is 34%, due to the fact that the snow density is on average lower in the forest (-14%) than in the open field. The second aspect analysed relates to the influence of the reduction effect caused by different forest stand densities. In order to investigate this factor, the sampling sites were classified into three macro-categories of stand density. The statistical tests show a significant difference between HS in open areas and in denser forest conditions, while the intermediate conditions of sparse and medium dense forests are not differentiated. The same applies for SWE.In general, the adopted sampling design worked well for the intended purpose. By estimating the density of the forest in a qualitative way by class, it is possible to observe a reduction of HS, SWE and snow density in the densest forests, when compared to the open field sites. To better investigate the relationship between delta HS and thedegree of cover it will be necessary to consider the total intercepting area in future measurement campaigns.