Santa Cruz Sandhills Plant Adaptations
Sandhills plants have a variety of adaptations that allow them to grow in the droughty, low nutrient Zayante Soils, including:
Several characteristics of Sandhills plant leaves and roots can facilitate plant growth in the Sandhills.
Light colored hairs on leaves and stems reflect excess sunlight and reduce water loss, as observed on Zayante everlasting (Gnaphalium sp. nov.) and a silver bush lupine seedling (Lupinus albifrons var. albifrons)
Other morphological adaptations that aid sandhills plant growth include
- Long roots to access moisture deep in the soil
- Dense, fibrous roots to gather available soil moisture
Small or waxy leaves reduce water loss, as observed on peak rush rose (Helianthemum scoparium; left) and pussy paws (Calyptridium umbellatum; right)
Some plant species adapt to life in the Sandhills through mutually beneficial relationships with other organisms.
Bacteria that fix atmospheric nitrogen are found on or around the roots of some Sandhills plant species, including silver bush lupine (Lupinus albifrons var. albifrons; left), and buck brush (Ceanothus cuneatus var. cuneatus; right). The symbiotic bacteria increase availability of nitrogen, which is important for plant growth and scarce in Zayante soils. Sandhills plants provide the bacteria with energy in the form of carbon created through photosynthesis.
Fungus on plant roots (mycorrhizae) enhance absorption of water and nutrients by plants, which in return provide the fungi with carbon (energy) from their roots. The two Sandhills dominant plants, ponderosa pine (Pinus ponderosa; left) and silverleaf manzanita (Arctostaphylos silvicola; right) are both thought to benefit from associations with soil fungi.
Another way to adapt to life in the Sandhills is to avoid the hot, droughty conditions of the summer months, and instead grow only in the winter and spring when temperatures are mild and soil moisture is more available.
Thirty-five percent of Sandhills plant species are annuals, which germinate following the first hard rains in the fall, grow throughout the winter and early spring, and then flower and die in spring, thus avoiding the summer drought and heat. Many of these annual plants are very small (less than 6 inches), and are referred to as "belly plants" because one needs to be on their belly to appreciate them.
During the summer, perennial species can drop their leaves to reduce transpirational water loss, as observed in the drought-deciduous California broom (Lotus scoparius; left). Alternatively, they can shed all aboveground structures and persist through storage organs in the soil (e.g. bulbs, corms), as observed in blue dicks (Dichelostemma capitatum; upper right) and sea muilla (Muilla maritima; lower right).