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Nov 3rd, 2021 (Article in newsletter, November 2021)

The Impacts of Fire and Drought in the Southern Sierra Nevada

Nina House
Figure 1. Field assistants Erin Berkowitz, Dylan Layfield, and Lou collecting plant vouchers.

Growing up in central New York, wildfires were far from my mind. That quickly changed when I moved to southern California in the summer of 2017, having freshly graduated with my Biology degree from State University of New York at Oswego. My first year here I lived in La Crescenta, and I watched in shock from my apartment window as flames lit up the night sky above the Verdugo Mountains. The La Tuna Fire of early September 2017 was just the first of many wildfires that I would experience here in California.

Since then, I have begun to pay close attention to fire season – even more during my time as a Botany master’s student at the California Botanic Garden. For my thesis, I am working on a floristic inventory of the Manter and Salmon Creek watersheds in the southern Sierra Nevada – an area becoming ever more prone to devastatingly large wildfires. Floristic studies are vital to understanding the impacts of disturbances, such as wildfires, on plant life. These studies involve the thorough documentation of plant diversity in a region, via the collection of voucher specimens and detailed observations. The voucher specimens are ultimately deposited in herbaria and provide vital information for many other forms of botanical research. They can be used to discern plant responses to climate change, as well as provide material for DNA extractions that will enhance our understanding of plant species relationships. At its core, floristic work helps us understand where plants grow in space and time, the conditions they thrive in, and the disturbances and threats that they face. In this way, floristic work is an important step in the process of making informed conservation decisions.

Figure 2. Normally alive with wildflowers, foothill poppy (Eschscholzia caespitosa) was one of the few annuals on these hillsides in early April of 2021.

Our understanding of the California flora is extraordinary, having benefited from the work of botanists for many years. However, there are regions that remain poorly documented in the herbarium record. Remote and rugged, parts of the Sierra Nevada range fall under this category. My study site is made up of the Manter and Salmon Creek watersheds, a 51 sq. mi part of the southern Sierra Nevada that is lacking in formal botanical documentation. The Domeland Wilderness makes up half of the study site (25 mi2) and is especially under collected – with only 127 known previous plant collections. Varied habitat types (montane meadows, mixed coniferous forests, montane chaparral, etc.) and a wide elevation range between 3,346 ft and 9,984 ft, contribute to the high diversity of vascular plants in this area.

In a time of such dramatic climatic change, it has never been more important to document rare, threatened, and endemic plant species. Thus far, I have spent 89 days in the Manter and Salmon Creek watersheds during the 2019, 2020, and 2021 field seasons. Over 23 trips, I have collected 1,428 voucher specimens, and have spent countless hours documenting the threats that these plants face.

Drought was one of the foremost things on my mind this past summer. An early scouting trip in April of 2021 was spent at the lowest parts of my study site, in Kern Canyon. Following the Salmon Creek, my field assistant Cody Schaaf and I bushwhacked through montane chaparral up to the lower Salmon Creek Falls. Though the Salmon Creek was flowing strongly, the steep hillsides surrounding it were more reminiscent of late summer than early spring (Fig. 2). The dry landscape was devoid of many of the annual flowering plants I was expecting to find, likely a result of the snowpack being at just 18% of the historical average. The Kern River, which the Salmon Creek is a tributary of, was flowing at 440 cubic ft/sec – a trickle compared to its normal 1000 cubic ft/sec in early April. While the higher elevations of my study site proved more fruitful, supplied by perennial water sources and summer thunderstorms, the impacts of the drought were still evident. Drainages normally flush with snowmelt and riparian vegetation were brown and dry, conifer understories were devoid of summer annuals, and the tips of foxtail pine (Pinus balfouriana) branches were brown with drought stress. This was a worrying sign for the southernmost population of this iconic pine.

Figure 3. Map of the study site, outlined in black. Red designates burn scars. The two largest burn scars in the study site are from the Manter Fire (2000) and the McNally Fire (2002).

A long-lasting drought can have many impacts, including increased tree die-off. This has already been documented throughout much of the western United States, including parts of the southern Sierra Nevada. These dry conditions are the perfect fuel for high severity wildfires. Perhaps the most dramatic changes to my study site in recent years have occurred due to fire (Fig. 3). The Manter Fire of 2000 burned over 67,000 acres, including much of the Domeland Wilderness. Over twenty years later, these burn scars remain evident on the landscape (Fig. 4). While surrounding unburned hillsides are covered with montane coniferous forest, the burn scar is dense with montane chaparral – particularly mountain white thorn (Ceanothus cordulatus) and greenleaf manzanita (Arctostaphylos patula). Notable is the absence of young pines that would represent the next stage of succession, bringing the area back to the montane coniferous forest it was before the fire. Community conversion has been happening throughout the Sierra Nevada - only time will tell whether it will happen here as well.

In addition to their impacts on the landscape, drought and wildfires have also affected my research. Some plants, including those that are rare and threatened, are less likely to germinate in low rain years. This makes fully documenting the diversity of a region, already difficult to do in a three-year period, that much harder. In addition, the unprecedented fire seasons of 2020 and 2021 led to National Forest closures throughout the state of California in late summer, effectively ending my field season. Several fires in 2020 and 2021, though not reaching the boundaries of my study site, resulted in unsafe conditions that further inhibited field work.

Figure 4. The 2000 Manter Fire burned through much of the Domeland Wilderness, leaving a burn scar that can still be seen over 20 years later.

Despite these challenges, this project is resulting in a greater understanding of this region, which is vital given the context of climate change. Documenting the impact of drought and wildfires on the landscape gives us insight into our environment’s uncertain future. Floristic work establishes a baseline that can guide management, inform conservation, and facilitate our understanding of landscape scale change that results from a changing climate.

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