Protecting and preserving mountain meadows: a look at seasonal patterns and soil properties

Background/Question/Methods

Sierra Nevada meadows are highly productive, yet limited by temperature and moisture, which determines snow-melt timing, duration of seasonally high water tables, and length of short growing seasons in these ecosystems. Although small on the landscape, meadows are keystone ecosystems due to their broad-scale functional importance as water filtration and storage systems, flood attenuators, hotspots for biodiversity, and critical habitat for wildlife. Wilderness meadows are frequent stop-overs for backpackers and pack stock users due to scenery and water proximity. Early season trampling can damage these sensitive ecosystems when soils are saturated and vegetation is developing, resulting in potential alteration to ecosystem condition and function. Our study examined seasonal patterns in meadow ecological processes (i.e.; moisture dry-down and soil firm-up) in relation to biotic and abiotic factors including vegetation and soil properties. Our objective was to inform land managers on effective tools for appropriate meadow opening date forecasting needed to preserve proper function. Specifically, we determined which soil properties correlated with seasonal variation in soil resistance within meadow plant communities, among three hydrologic regimes (xeric, mesic, hydric). We conducted weekly sampling in differing randomized 1 m² plots within five meadows at Yosemite National Park during the growing season until plant senescence.

Results/Conclusions

Results using multivariate analysis approaches suggest significant correlations among predictive variables of soil resistance (SR). The main interaction found was that soils display greater resistance as soil moisture decreases over the growing season. SR strongly correlated with abiotic metrics including volumetric and gravimetric soil moisture (R²= .319, .430, p-values .035, .010 respectively) and soil properties; bulk density (R²=. 351, p-value .026), rock fraction (>4mm) (R²=. 474, p-value .007), and clay fraction (R²=.440, p-value .010). SR significantly correlated with biotic factors including root fraction (R²=.600, p-value .001) and total vegetation cover (R²=.831, p-value <.000). Results imply that SR is best explained by plant biomass (vegetation cover and roots) among communities. Soil moisture also significantly correlated with organic matter (R²=.862, p-value <. 000), pH (R²=0.497, p-value .005), carbon (R²=0.706, p-value <0.000), and nitrogen (R²=0.528, p-value 0.003). Relationships among snow melt-out date, meadow green-up, air temperature, and plant phenology were also detected. These data may be scalable to a larger data set because many explanatory and response variables significantly correlated in both communities and meadows. Our results show promise for the development of a useful wilderness management planning tool needed for the protection and preservation of proper functioning condition in these keystone ecosystems.