Topographic controls on snow distribution, soil moisture, and species diversity of herbaceous alpine vegetation, Niwot Ridge, Colorado

Abstract

[1] The nature of the snowpack has the potential to strongly influence the patterns of alpine plant productivity and composition by governing soil moisture levels, growing season duration and the thermal regime of alpine soils. This study evaluates these relationships by modeling the interrelationships of snow depth, snow water equivalent (SWE), snow disappearance rate, soil moisture, attributes of the alpine plant community and selected terrain factors using decision-tree techniques at Niwot Ridge, Colorado Front Range. The modeling results showed a strong correlation (r 2 > 0.9, P < 0.001) between the snow disappearance rate and SWE and terrain factors that control the degree of shelter and exposure of a given local and elevation. The model was sufficiently robust to predict the spatial distribution of the snowpack for 12 years that exhibited average snow fall (r 2 = 0.8, P < 0.001), but yielded lower correlation (r 2 = 0.2, P < 0.001) in drought years. Soil moisture was significantly correlated (r 2 = 0.7, P < 0.001) with snow-fall amounts and terrain factors; however, meltwater and summer rain offset the potential soil moisture deficit in windward sites. Annual plant biomass did not correlate well with snow attributes and soil moisture because the cascading impact of topography on snowpack and soil moisture was not well captured by measurements of aboveground biomass. In contrast, the species richness index was significantly correlated with snow depth and soil moisture (r 2 = 0.7, P < 0.001), thereby demonstrating the importance of snow on some attributes of the alpine plant community.Citation: Litaor, M. I., M. Williams, and T. R. Seastedt (2008), Topographic controls on snow distribution, soil moisture, and species diversity of herbaceous alpine vegetation, Niwot Ridge, Colorado,

Forecasting Alpine Vegetation Change Using Repeat Sampling and a Novel Modeling Approach

“…The decrease in the prevalence of Snowbed vegetation in the monitoring sites is somewhat expected (Björk and Molau 2007) despite evidence suggesting winter snow-depth has not changed (Litaor et al 2008). Snowmelt, however, is occurring earlier (Chow 2010).…”

“…and nitrate (NO 3 -) deposition ). While it is unclear what the impact increased N-deposition has had on vegetation composition, species removal, N fertilization, altered snow depth, and warming result in profound differences in ecosystem function in manipulative experiments (Williams et al 1998;Suding et al 2006;Walker et al 2006;Volk et al 2011;) all of which together with results from modeling studies (e.g., Litaor et al 2008) illustrate the sensitivity of alpine tundra on Niwot Ridge to global change.…”

Controls on the temporal and spatial variability of soil moisture in a mountainous landscape: the signature of snow and complex terrain

“…The ability of the distance to divide variable in this study to represent available water input throughout the year, both the early season lateral flow and the late season snow water input, storage, and lateral flow, explains its more significant correlation with overall soil moisture trends as compared with snow and soil variables. These correlations suggest the spatial domain of the dynamic influence of snowmelt on soil moisture patterns is dependent on how static variables like slope position and orientation influence snowpack development and retention of snow and early season meltwater (Litaor et al, 2008).…”

“…In snow-dominated mountain regions precipitation does not necessarily enter the soil where it falls, but where it melts. Redistribution of snow by wind and differential melt patterns controlled by elevation, aspect, and vegetation create spatially heterogeneous snow cover that leads to spatially variable soil moisture patterns (Litaor et al, 2008;Seyfried et al, 2009). Few studies have documented how the distribution of snow interacts with other variables to control soil moisture patterns.…”

The niche, limits to species' distributions, and spatiotemporal variation in demography across the elevation ranges of two monkeyflowers

“…Temperature increases may also interact with changes in other important environmental variables. For example, changes in snowpack may have dramatic influences on all species by altering the availability of soil moisture during the growing season (47) and on riparian species in particular by also altering the magnitude of spring flooding events, which can increase both adult mortality and seedling recruitment (48). Longer time series of demographic parameters are desirable for relating variation in vital rates and population dynamics to interannual variation in climate and hydrology.…”