1999-2000 Pollen Analysis Results

Pinon Pine

The 16 pollen samples counted span the last 15,000 years, or one sample every 1000 years. More samples currently being counted will fill in the gaps and provide to at least 1 sample per 500 years. This will give us an idea of long-term trends and how responsive (sensitive) the vegetation of the site is to climate change.

Sagebrush (Artemisia)

The pollen percentage diagram shows that pine and sage plants dominated the land around Bear Lake from 14,000 years ago until today. We know from other paleoclimate records that major climatic changes occurred around 14,000; 11,000 and 4500 years ago in North America. The last glaciation ended about 14,000 years ago and the entire Northern Hemisphere warmed considerably afterwards.

During the ice age, giant lakes formed in the Great Basin, extending across much of Nevada and Utah (Morrison, 1991 and Oviatt and others, 1992). From 28,000 until about 10,000 years ago, the Great Basin lakes created a lake-effect on storms traveling across Nevada, Utah, Wyoming and Colorado. Those regions, which include deserts today, received enough moisture to support widespread pine and spruce forests. Today, the modern Great Lakes of Michigan, Superior, Huron, Erie and Ontario cause lake-effect precipitation events in New York, Michigan, Ontario and Quebec.

Pinus Contorta

At Bear Lake we find pollen from cold forests and tundra-like environments from the earliest part of our record until about 12,500 years ago. Grasses and meadow species dominated, with low shrubs like bitterbrush and potentilla common. Birch (Betula) and buckwheat (Eriogonum spp) pollen are most abundant in this early period.

Pine (Pinus) and sagebrush (Artemisia) are the most abundant pollen throughout the record, and they trade off with each other in being most abundant. Sagebrush comes into the area and dominates during two periods: between 15,000-14,000 years ago and between 11,000-9000 years ago. An unexpected peak in pine and other types (hemlock, buttercup, saxifrage and cattail) occurs 9000-8000 years ago, suggesting that a change in climate lasting about 1000 years may have occurred. These species prefer wetter conditions. The geochemistry and diatom results also indicate increased precipitation during this interval. During this wet period, Bear Lake was probably deeper and more extensive than today.

Buttercup

In the last 4000 years, the pollen assemblage shows some similarity to the environment of 15,000 years ago, with Asters, pinks, saxifrage, ephedra, horsetail (Equisetum) and spore types more common. This suggests that the climate has cooled and maybe become slightly wetter than it was from 8000-4000 years ago.

Our next goal for the Bear Lake Project is to develop records that will show more recent changes at the lake and identify current trends in lake level and precipitation. This goal requires high-resolution sample analyses, with at least two samples every 100 years (minimal decadal-scale resolution). In August 2000 we will return to Bear Lake with our coring equipment and will take a series of short cores in the north end of the lake and in the wetlands beyond that. We expect this to show us when and how much the lake level changed in the last couple thousand years. It will also help us determine how much the diversion of the Bear River in to the lake has affected the natural hydrology of the lake and the wetlands.

Cattails line Bear Lake outlet canal in Dingle Swamp

Sedges (rushes) are also common in Dingle Swamp

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