On the eastern side of the Sierra, ribbons of brilliant gold flow down the mountainside. The color can be seen from miles away. Meadows spread wide covered with vivid yellow-leafed aspen quaking in a fall breeze. It's the height of the fall foliage season in this part of California.
As I drove down Highway 89 south of Lake Tahoe past Markleeville and then over Monitor Pass to Highway 395, each stand of aspen seemed to glow brighter than the last. I wondered if they would be as beautiful for future generations, or if our impact on the environment would cause these glorious trees to change in any way.
Quaking aspen (Populus tremuloides) is the most widespread tree species in North America. It provides food for foraging animals and habitat for wildlife. It also acts as a fuel break and retains much more water in the environment than do most conifer species.
High mountain systems, such as the Sierra Nevada, are uniquely sensitive to anticipated global climate changes and act as canaries in the coal mine to provide early signals of significant climate-driven changes.
Research in the Sierra Nevada by Pacific Southwest Research Station, which is a U.S. Department of Agriculture Forest Service research organization, shows how vegetation has responded to the climate in the past and indicates changes than might be coming in the future over the next decade.
Climate has a profound influence in shaping our environment and natural resources. By looking at tree-ring records of living and ancient wood and pollen lake sediments, the present climate can be compared to these historical patterns to show climate changes.
Research indicates a complex, unpredictable future for aspen in the West, where increased drought, ozone and insect outbreaks will compete with carbon dioxide fertilization and warmer soils, with unknown cumulative effects.
Aspen are valuable in providing moisture in the landscape and habitat and food for wildlife. They are vulnerable in the face of global warming and climate change. Hopefully, we will not lose this wonderful tree in California.
If you're from a part of the country where these trees are native and you miss their fall color, there is a new cultivar of Improved Quaking Aspen developed for mild winter areas like ours. It provides a splash of color for areas that are naturally moist, such as a natural stream or a high water table. They grow 20 to 30 feet tall and 15 feet wide and spread by underground roots to form a stand.
Plant spring-blooming bulbs
Continuing in the spirit of all things fall, it's prime time to plant tulips and other spring-blooming bulbs.
If you're like me and have squirrels scampering up every tree, checking out planting beds and planters for choice acorn-planting spots, you are undoubtedly aware of how difficult it is to keep them from digging up and eating the bulbs. Yes, you can plant the bulbs surrounded by chicken wire or hardware cloth — but there's an easier way that's just as effective.
Dig the hole and plant the bulb as you normally would, but instead of caging it, cover the bulb with poultry grit, which is made up of crushed granite, shale or oyster shells and is available at feed stores. The squirrels don't like trying to dig through the sharp grit and quickly give up.
Next spring, if they have the nerve to eat the flower buds right when they emerge from the soil, you might just have to plant the types of bulbs that squirrels won't eat, such as daffodils, snowdrops, chionodoxa, hyacinth or fritillaria.
Try a cover crop
It's also time to plant a cover crop in your vegetable garden to improve production next year. Fall cover crops include legumes such as fava beans, peas, vetch and clovers, which germinate and grow quickly, but not so fast as to harm late-season or overwintering vegetable crops. Oat grass can be sown to hold the soil and protect it from erosion.
Cover crops also protect the soil from pounding winter rains, which compact the soil surface and leach out nutrients. They are thick enough to choke out emerging weeds, and their root systems break up and aerate hard soil. Members of the pea family gather nitrogen into their roots to further enrich the soil.
In the spring, you can turn the cover crop into the soil and allow it to decompose in place or pull the plants and compost them separately. That way, you can plant right away and add the compost back into the garden later, when it has finished decomposing.
Seeds germinate best when the soil is in the 50-degree range, so don't delay.
- Jan Nelson, a landscape designer and California certified nursery professional, will answer questions about gardening in the Santa Cruz Mountains. Email her at email@example.com, or visit www.jannelsonlandscapedesign.com to view past columns and pictures.