CEC Research | https://doi.org/10.21973/N3BT0P Summer 2018 1/10

Examining changes in plant communities of alpine fellfield meadows of the White Mountains

Sarah Ardell1, Karina Arzuyan1, Neil Singh2, Haleigh Yang1, Steven Zhou1

1University of California, San Diego, 2University of California, Davis

ABSTRACT

Alpine meadows are havens of biodiversity and limiting resources, especially in arid and semi-arid climate zones. With climate change exacerbating the seasonal variation of moisture and temperature, such havens continue to shift upward and reduce in range, disrupting vital habitats that endemic organisms rely on. We examined plant communities of three alpine fellfield meadows in the White Mountains of California by conducting a follow-up survey to a baseline assessment performed in 2006 (Ababneh and Woolfenden 2010) of two meadows and surveying an additional meadow to expand the scope of the study. Our analysis focuses specifically on how climate change influences meadow plant communities over time, as well as examining shifts in their reproductive phenology. From these methods, we found plant communities of the original two meadows changed over time with the driest meadow resulting in the greatest local extinction of wetland species and an overall increase in upland affinity species from 2006 to 2018. Additionally, there were abnormal temporal patterns in the reproductive phenology of many forbs, with some blooming before and some after their expected bloom time. This resurvey demonstrates the importance of conducting baseline studies in alpine meadow habitats that may disappear over time and highlights the role of moisture and precipitation patterns in predicting shifts of plant community dynamics. Keywords: climate change, alpine, alpine meadows, plant communities, phenology

INTRODUCTION

Recent shifts in global temperature and precipitation patterns are causing major impacts on ecosystems and altering the plant communities within them (Penuelas et al. 2018). Meadows are particularly sensitive to climatic changes (Lambrecht et al. 2006, Sloat et al. 2015), which suggests that any shifts in plant community composition could be clear indicators of changing local climate

conditions. Furthermore, alpine areas have also been shown to be sensitive to climate changes (Pauli et al. 2012), meaning that alpine meadows may be under significant threat.

Moisture and temperature strongly regulate the composition of meadow vegetation (Berlow et al. 2003, Lambrecht et al. 2006). Climate projections point to greater variations in precipitation (Trenberth 2011), and under both

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extremes—of drought or high precipitation—plant survival in meadows typically diminishes (You et al. 2014, Gattringer et al. 2018). The presence of wetland species are strong indicators of water content; lower numbers of wetland species or an absence thereof indicate drier conditions (Tiner 1999). In addition to moisture levels, increases in temperature have also been correlated with declines in alpine meadow species richness (Theobald et al. 2017).

Drier and hotter conditions can increase encroachment of more drought-tolerant species, shifting plant community dynamics of alpine meadows. In cases such as grass-dominated alpine meadows, shifts towards lower precipitation or higher temperatures can cause transitions towards a shrub or forest-dominated plant community, as both shrubs and trees have greater tolerance of drought (Wood 1975, Knapp et al. 2008).

Climate change also creates more stochasticity in ecosystem functionality due to greater variations in weather conditions over time. This stochasticity can then manifest itself by shifting phenological patterns of plant growth and development. According to Fu et. al (2018), growing seasons are delayed if precipitation occurs later than normal. A shift in growing seasons can severely affect the next generation of flowering plants’ blooming times. Thus, plant phenology may indicate how plant communities react to changes in the event of global temperature increases.

Because of their ability to support many plant species and their sensitivity to precipitation and temperature, wet alpine meadows are excellent study systems for observing effects of changing abiotic factors on plant communities. A 2006 plant diversity survey on two wet alpine meadows at the

White Mountains in California intended to establish a baseline for future study on the effects of climate change on meadow plant communities (Ababneh and Woolfenden 2010). The White Mountains have harsh environmental conditions with high altitude and large annual climatic variability. Nevertheless, many species of plants have persisted in this harsh climate. Since the original 2006 survey twelve years ago, mean annual temperature has increased by 1°C in the region (WRCC 2008).

In this study, our goals were to note differences in plant diversity and composition from the 2006 baseline study, compare methodology of plant community assessments, and examine an additional wet meadow to expand the scope of the baseline study for future analysis. We predicted that there would be an overall decline in wetland species diversity and cover compared to 2006. We also predicted the present-day wet meadow would have a similar species composition to the previous meadows due to similar standing water presence. Lastly, we predicted forb blooming periods would shift as a result of the fluctuations in precipitation and increases in temperature. Using a baseline study, we sought to gain a stronger understanding of how alpine meadow species composition can change over time in response to shifts in climate.

METHODS

2.1 Natural History of the Study System

We surveyed the plant communities of three alpine fellfield meadows on the upper slopes of the White Mountains in Mono County, CA, from August 1st to August 4th, 2018. Climatic conditions at these alpine

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elevations consist of a semi-aridic moisture regime with high winds, extreme temperatures, and increased incidents of ultraviolet exposure and solar radiation year-round. Precipitation typically occurs as snow or hail in winter months, with occasional precipitation in spring and summer. The fellfield meadows here are primarily fed by springs and streams resulting from snowmelt in winter months, exhibiting predominately fen-like characteristics. This annual abundance of moisture allows many unique plants that are not typical of sagebrush communities to persist. Additionally, these meadows provide important sources of water and forage for a plethora of fauna despite the challenging climatic conditions that occur throughout the year, including marmots, pikas, bighorn sheep, and mule deer. We identified and delineated the three meadows and their boundaries according to pre-existing maps as well as abrupt changes in vegetation and slope gradient. The meadows were then classified as wet if there was standing water present and dry if it was absent.

The first two meadows, Barcroft Gate Meadow and East Shield Meadow, were surveyed in 2006 (Ababneh and Woolfenden 2010) and again in this study. Barcroft Gate Meadow is a lower elevation, dry meadow mosaic located approximately 180 m from Barcroft Gate Road (37o33'33.6" N, 118o13'29.9" W). It lies southeast of a rutted truck culvert at an elevation of 3370 m on a slightly sloping easterly aspect. The meadow sampled for baseline comparison measures 27 m EW by 90 m NS and contains several gullies from ephemeral streams created by snowmelt runoff. East Shield Meadow is a higher elevation, rocky wet meadow found

772 m directly east of Barcroft Field Station at an elevation of 3689 m (37o34'47.2" N, 118o13'29.9” W). It lies on a slight depression between several rocky knolls and two hummocks, measuring 68 m EW by 45 m NS on a western aspect. Further characterization and photos of these meadows can be found in Ababneh and Woolfenden (2010). The third meadow we surveyed, Marmot Meadow, is very wet, characterized by hummocks, an abundance of standing water, and many tussocks. It is located 80 m SE of Barcroft Road past the Barcroft Gate at an elevation of 3645 m, measuring 41 m EW and 32 m NS (Figure 1).

Figure 1: Panoramic photo of Marmot Meadow. The third meadow surveyed was characterized by grassy hummocks, rocky outcroppings, and moist soil. Transects ran 42 m (left to right in photo) by 31 m (top to bottom in photo).

2.2 Research Design

We first surveyed the vegetation of these meadows using the same methods as Ababneh and Woolfenden (2010), and within the same week as the initial study. Our team performed a complete inventory of the plant species present by walking in a zig-zag direction through each meadow. We also conducted 1 m point-intercept counts of species along two transects, one with a NS

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axis and another going EW crossing at the centroid of each meadow and stretching across to its boundaries. In addition to these two methods, our team also measured percent cover of meadow vegetation using a 0.25 m2 quadrat every five meters along the same two transects used for point-intercept. The use of two survey techniques allowed us to compare their accuracy for plant community assessments.

Each plant species was either identified in the field or sampled and photographed to identify later. They were then classified as wetland species or upland species based on the indicator categories of occurrence in wetlands given by the U.S. Army Corps of Engineers in the National Wetland Plant List. Species that are wetland obligates, wetland affiliates (found primarily in wetlands), or partial wetland affiliates (found in both wetlands and non-wetland environments) were classified as wetland species. Wetland non-tolerant species were classified as upland species.

We also assessed changes in reproductive phenology of plants in the three meadows by observing the reproductive stage of the majority of individuals for each species. We categorized reproductive phenology into six stages: 0. Not Reproducing, 1. Budding, 2. Budding with Some Flowers, 3. Flowering/Seeding, 4. Fruiting, and 5. Reproductive Senescence. We then compared our field observations to the typical flowering period of each species using current Jepson Herbarium data to determine if recent climatic factors are influencing blooming time.

2.3 Statistical Analyses

To test differences in meadow community composition over time in both meadows, we performed statistical analyses using JMP v13. Our team performed a multidimensional scaling analysis using the percent cover of all species from each meadow (both past and present) to visualize the differences between plant community compositions. We also performed a chi-squared analysis to test the effect of wetland affinity on species tendency to colonize or go locally extinct. Lastly, we tested for a relationship between quadrat and point-intercept percent cover estimates by performing a linear regression.

RESULTS

Barcroft Gate Meadow had a total of 22 plant species consisting of 12 species of shrubs and forbs, 5 species of sedges and rushes, and 5 species of grasses (Table 1). East Shield Meadow had a total of 25 plant species consisting of 15 species of shrubs and forbs, 5 species of sedges and rushes, and 5 species of grasses (Table 2). Marmot Meadow had a total of 31 species consisting of 19 species of shrubs and forbs, 7 species of sedges and rushes, and 5 species of grasses (Table 3).

The plant communities of both Barcroft Gate and East Shield changed over time; however, the overall plant community of East Shield changed more than Barcroft (Figure 2). In Barcroft, 11 species colonized the meadow and 6 went locally extinct. In East Shield, 10 species colonized and 3 went locally extinct. The Marmot Meadow plant community is most similar to the plant community of East Shield in 2018.

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Table 1: Plant Community Composition of Barcroft Gate Meadow 2018

Table 2: Plant community composition of East Shield Meadow 2018

Table 3: Plant community composition of Marmot Meadow 2018

Figure 2: NMDS illustrating differences in plant communities from 2006 to 2018. The East Shield Meadow changed more than the Barcroft Gate Meadow between 2006 and 2018. Marmot meadow’s plant community is most similar to the plant community of East Shield Meadow in 2018. Space between points represents differences in overall plant community. Grey shapes represent plant communities in 2006, and arrows show change in meadow plant community from 2006 to 2018.

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In Barcroft Gate Meadow, colonizing species tended to have upland affinity whereas species that went locally extinct tended to have wetland affinity (N = 17, χ 2 = 4.01, P = 0.05; Figure 3). In East Shield Meadow, wetland affinity was not associated with species colonization or local extinction (N = 12, χ 2= 0.17, P = 0.73).

Figure 3: Wetland affinity of colonizing and locally extinct species. In Barcroft Meadow, a higher proportion of plant species that went locally extinct (were present in 2006 but not in 2018; dark grey) have wetland affinity than plant species that colonized (were absent in 2006 but present in 2018; light grey). In East Shield Meadow, there was no significant difference in proportion of species that have wetland affinity between those that colonized and those that went locally extinct.

Several species of forbs in the meadows showed phenological patterns different from their typical bloom times. Four species were blooming earlier than expected, nine species were blooming later than expected, and eight were blooming within their usual bloom period (Figure 4).

Figure 5: Correlation between percent cover estimate for quadrat and point intercept methods. The quadrat and point intercept methods produce very similar percent cover estimates for species they both find. Each point represents percent cover estimates for an individual species.

Figure 6: Proportion of total species detected using point intercept and quadrat methods. the quadrat method (dark grey bars) detected a higher proportion of the total species in the meadow than the point intercept method (light grey bars) for all three meadows surveyed.

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Figure 4: Observed forb phenology patterns compared to expected bloom time intervals. Survey conducted on August 2 (Julian Date 214). Julian Bloom interval is the range of dates correlated with the days of the year in which each species is expected to be in bloom according to Calflora. Four forbs (blue crosses) were seen in a stage beyond flowering - either fruiting or senescing - despite our observation date being during their expected bloom interval. Eight forbs (red dots) were seen flowering during their expected bloom interval. Nine forbs (greens x’s) were observed in a flowering stage despite their expected bloom interval ending. Draba oligosperma was observed in a budding stage despite falling within its bloom period.

There was a strong correlation between the percent cover measurements taken using the point intercept versus quadrat methods (N = 90, R2 = 0.83 , P < 0.01 ; Figure 5). However, the quadrat method was able to detect more species than the point-intercept method in all meadows (Figure 6).

DISCUSSION

We found shifts in the plant communities of the meadows between 2006 and 2018; however, the changes were idiosyncratic. Based on climatic data, we predicted that wetland species richness and density would

decline. We found this pattern at Barcroft Gate Meadow, which dramatically changed in species composition, but not in East Shield Meadow. This difference is likely because Barcroft Gate Meadow experienced much more drying in the time between the baseline study and current study. Standing water was observed at Barcroft Gate Meadow in 2006 (Ababneh and Woolfenden 2010) but was not present in 2018 during our resurvey. This meadow was the driest site of the three and saw a sharp decline in the proportion of wetland-affinity plants from the 2006 survey (Figure 4). Forbs utilize water allocated close to the soil surface,

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making this site uninhabitable for wetland forbs and other wetland plants to sustain in (Debinski et al. 2010).

East Shield Meadow featured no significant change in the proportion of wetland species between 2006-2018 and had standing water at the time of both studies. East Shield Meadow sits in a depression between two hummocks, which allowed for a greater accumulation and retention of water. This allows for greater moisture within the meadow, in contrast to the flat, unidirectionally-sloping Barcroft Gate Meadow that is more likely to lose water.

Marmot Meadow, which was not surveyed in 2006, had a similar plant species composition to that found in the 2018 survey of East Shield Meadow (Figure 2). However, Marmot Meadow’s plant community was quite divergent from the 2006 survey of Barcroft Gate Meadow. The differences between the two meadows are best described by their respective topography. Marmot Meadow is characterized by rolling hummocks throughout the meadow’s boundaries, whereas Barcroft Gate meadow is a flat, uniformly sloping meadow. Conversely, Marmot Meadow and East Shield Meadow had greater similarity in species composition due to similarities in topographic features. Both occurred in rocky depressions capable of holding standing water, fostering greater species diversity.

Based on the predicted Julian bloom date and the observed phenological stage, we found 13 out of 21 forbs bloomed outside of their expected blooming range (Figure 3). These observed abnormalities could be attributed to fluctuations in climate and precipitation patterns. Blooming fluctuations in alpine environments depend

on the snowmelt, soil moisture, and temperature following snowmelt (Theobald et al. 2017). In 2018, the highest peaks of Northern California experienced up to one meter of snowfall in the early parts of March, later than expected (Swain 2018). The late snowfall led to cooler temperatures and more moist soils further into the 2018 year. As described by Theobald et al. (2017), high-elevation blooming occurs soon after snowmelt to optimize the growing season. Late blooming may have been in response to the late snowmelt. Hotter and drier summers may explain why four forbs bloomed early. In response to the dry season, some forbs with an expected bloom time of the fall bloomed earlier. As snowfall fluctuates and temperatures remain higher than previous years, shifts in blooming periods are imminent, having the potential to affect herbivory and pollinator patterns (Theobald et al. 2017).

Expanding this study to include more meadows would build upon the patterns we see as climatic factors continue to vary over time. Though there was no difference in the species percent cover estimates using point-intercept and quadrat methods (Figure 5), the greater number of species captured by the quadrat method suggests that using the quadrat method may create a better picture of the meadow plant composition (Figure 6). While conducting the quadrat method was more time-intensive, it creates replication within each meadow that strengthens our statistical power to perform higher-level analyses. Additionally, the quadrat method captures more species, including rare plants. We suggest using this method in future studies to obtain a more adequate representation of the meadow community.

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Another future study could consider how elevational differences between meadows impact plant diversity. This study could reveal more patterns about plant encroachments and local extinctions. Small changes in annual temperature have caused thermophilization—the decline in cold-adapted species and increase in warm-adapted species (Gottfried et al. 2012)—along with elevational shifts of plant species in alpine environments (Vanneste 2017). Comparing meadows from low, middle and high alpine altitudes could show patterns in plant movement.

Because the changes we observed in plant community composition between 2006 and 2018 were idiosyncratic and unpredictable, our study demonstrates that we cannot be sure how anthropogenic effects on climate will affect the world around us. As temperature and precipitation become more variable and unpredictable, so will the responses of different plant communities, making baseline assessments and resurveys a necessity in proactively monitoring anthropogenic climate impacts.

ACKNOWLEDGMENTS

Research was conducted at the University of California’s White Mountains Research Station at Crooked Creek, doi:10.21973/N3KM2J.

We would like to thank our professors Krikor Andonian and Tim Miller for their consistent guidance and support and our fellow California Ecology and Conservation students for their enthusiasm and kindness throughout the research process.

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