Influence of Hydrology and Recreational Pack Stock Grazing
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INFLUENCE OF HYDROLOGY AND RECREATIONAL PACK STOCK GRAZING ON SUBALPINE MEADOWS OF THE JOHN MUIR AND ANSEL ADAMS WILDERNESS AREAS, CALIFORNIA by Daniel F. Shryock A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment Of the Requirements for the Degree Masters of Science In Natural Resources: Planning and Interpretation May, 2010 ABSTRACT Influence of Hydrology and Recreational Pack Stock Grazing on Subalpine Meadows of the John Muir and Ansel Adams Wilderness Areas, California Daniel F. Shryock Subalpine meadows of the Sierra Nevada are groundwater-dependant ecosystems, making them highly vulnerable to hydrologic disturbances, including pack stock grazing. This study evaluated the interrelated effects of hydrology and grazing on plant species composition in subalpine meadows of the John Muir and Ansel Adams Wilderness Areas, California. Evidence was found for the primary importance of the hydrologic gradient in structuring subalpine meadow plant communities through vegetation sampling at groundwater monitoring wells and multivariate statistical analyses. Species composition was significantly correlated to water table depth, while species diversity was significantly correlated to water table drawdown. Basal cover of vegetation at monitoring wells was not significantly correlated to water table variables and may correspond more to some other factor. Seven meadows with stream channels previously rated to be in Proper- Functioning-Condition were also compared to seven meadows with channels rated Functional-At-Risk in a downward or unknown trend. Meadows in Proper-Functioning- Condition had significantly greater cover of hydric, deep-rooted graminoids and hydric woody species than meadows rated Functional-At-Risk, but no differences in bare soil levels were detected. Finally, permanent meadow plots in four meadows were sampled iii for changes in species composition over the last two decades. Plots in two meadows showed significant decreases in cover of obligate wetland species, possibly as a result of hydrologic changes stemming from past grazing pressure. Inconsistent trends across plots within each meadow highlighted the inherent variability of these environments. iv TABLE OF CONTENTS Page ABSTRACT……………………………………………………………………………. iii LIST OF TABLES……………………………………………………………………… vii LIST OF FIGURES…………………………………………………………………….. ix LIST OF APPENDICES……………………………………………………………….. x INTRODUCTION…………………………………………………………………........ 1 MATERIALS AND METHODS……………………………………………………….. 14 Study Site…………………………………………………………………………….. 14 Vegetation Sampling at Monitoring Wells………………………………………….. 16 Meadow Vegetation Analysis………………………………………………………. 24 Permanent Meadow Plots…………………………………………………………… 26 RESULTS………………………………………………………………………………. 28 Vegetation Sampling at Monitoring Wells………………………………………….. 28 Meadow Vegetation Analysis………………………………………………………. 36 Permanent Meadow Plots…………………………………………………………… 37 DISCUSSION………………………………………………………………………….. 52 Transect Cluster Analysis…………………………………………………………… 57 Conclusion…………………………………………………………………………… 64 v TABLE OF CONTENTS (CONTINUED) LITERATURE CITED…………………………………………………………………..68 APPENDICES…………………………………………………………………………...76 vi LIST OF TABLES Table Page 1 Functional groups derived from classification of six species traits, as reported in Weixelman (2006)…………………………………………………...10 2 Location and characteristics of meadows sampled during summer 2008 and 2009 field work in the John Muir and Ansel Adams Wilderness Areas, California….……………………………………………………………………..17 3 Indicator Species Analysis comparing vegetation plots at monitoring wells in meadows of the John Muir Wilderness where the water table was measured less than 40 cm from the soil surface and those where the water table was always greater than 40 cm from the surface. P-values derive from a permutation procedure…………………………………………….30 4 Canonical correlation analysis of basal cover, species diversity, and increaser species cover versus water table measurements taken at monitoring wells in meadows of the John Muir Wilderness during summer 2009. Each pair of canonical variates (Ui and Vi) is associated with one Canonical correlation (r) and p-value………………………………….31 5 Indicator Species Analysis comparing meadows of the John Muir and Ansel Adams Wilderness Areas previously rated Proper-Functioning- Condition with those rated Functional-At-Risk, based on sampling conducted in summer 2008. P-values derive from a permutation procedure…………………………………………………………………………38 6 Transect groups identified through hierarchical, agglomerative cluster analysis of plant species cover values sampled during summer 2008 in the John Muir and Ansel Adams Wilderness Areas. Indicator Species Analysis was used to identify significant indicator species associated with each cluster. P-values derive from a permutation procedure………………40 7 Average plant species abundances within clusters derived through hierarchical, agglomerative cluster analysis of meadow transects sampled during summer 2008 in the John Muir and Ansel Adams Wilderness Areas………………………………………………………………...41 vii LIST OF TABLES (CONTINUED) 8 Species recorded on permanent plots in Spooky Meadow in 1990, 1999, and 2008. Table entries are total hits for each species in a 2’ x 2’ plot at points formed by the intersections of gridlines spaced four inches apart, resulting in 25 points per plot. The dominant species at each point was recorded…………………………………………………………………………..44 9 Species on permanent plots in Purple Meadow, as recorded in 1990, 1999, and 2008. Table entries are total hits for each species in a 2’ x 2’ plot, at points formed by the intersections of gridlines spaced four inches apart, resulting in 25 points per plot. The dominant species at each point was recorded. Plot 3 could not be located in 2008 and is omitted…………………...46 10 Species recorded on permanent plots in Upper Alger Lakes Meadow in 1990, 1999, and 2008. Table entries are total hits for each species in a 2’ x 2’ plot at points formed by the intersections of gridlines spaced four inches apart, resulting in 25 points per plot. The dominant species at each point was recorded………………………………………………………….47 11 Species recorded on permanent plots in Horse Heaven in 1990, 1999, and 2008. Table entries are total hits for each species in a 2’ x 2’ plot at points formed by the intersections of gridlines spaced four inches apart, resulting in 25 points per plot. The dominant species at each point was recorded…………………………………………………………………………..49 viii LIST OF FIGURES Figure Page 1 Study Area within the Inyo National Forest, including portions of the John Muir and Ansel Adams Wilderness Areas…………………………………15 2 Graphical display of correlations between original variables and canonical variates derived through the canonical correlation analysis given in Table 4. These correlations provide a measure of the degree to which variability in each original variable is reflected in the linear combinations comprising the canonical variates………………………………...33 3 Nonmetric multidimensional scaling ordination of vegetation plots located at monitoring wells in the John Muir Wilderness, based on total cover of Weixelman’s (2006) functional groups. The significant vectors for high water table, low water table, and diversity are displayed on the ordination. Approximate centers for each functional group are also displayed by weighted averaging…………………………………………...35 4 Nonmetric multidimensional scaling ordination of vegetation plots associated with monitoring wells in the John Muir Wilderness, based on total cover of Weixelman’s (2006) functional groups. This plot shows water table group centers resulting from factor fitting, along with polygons enclosing all plots in each group. Group B contains plots where the water table was measured less than 40 centimeters from the soil surface, while Group A contains all other plots. Centers for functional groups are also displayed by weighted averaging……………………36 5 Dendogram from hierarchical, agglomerative cluster analysis of meadow transects sampled during summer 2008 in the John Muir and Ansel Adams Wildernesses. Transect labels at the bottom of the dendogram begin with the first letter of the meadow names given in Table 2……………….39 6 Proportions of Weixelman’s (2006) ecological condition classes in permanent meadow plots within the John Muir and Ansel Adams Wilderness Areas monitored in 1990, 1999, and 2008…………………………..50 ix LIST OF APPENDICES Appendix Page A Vascular plant species found in study area within the John Muir and Ansel Adams Wilderness Areas and organized by family. Nomenclature follows the USDA Plants database (2010)……………………….76 B Water table variables and plant species cover measured at monitoring wells in Purple Meadow, John Muir Wilderness, during summer 2009………...79 C Water table variables and plant species cover measured at monitoring wells in Tully Hole Meadow, John Muir Wilderness, during summer 2009………………………………………………………………………………80 D Water table variables and plant species cover measured at monitoring wells in Agnew Meadow, Inyo National Forest, during summer 2009………….82 E Water table variables and plant species cover measured at monitoring wells in Johnston Meadow, John Muir Wilderness, during summer 2009………………………………………………………………………………84 F Snow depth at Gem Pass and Mammoth Pass snow stations for the period from 1989 to 2009. Snow Station information was retrieved from the California Department of Water Resources Data Exchange Center.………….…85 x INTRODUCTION Recreational use of Congressionally designated Wilderness Areas is an increasingly