Does this mean a dense healthy cover of grass can’t protect karst health and function? No. It means grass cannot establish a dense cover on degraded Texas karst country as effectively as a mountain cedar thicket. Until the land starts regenerating, it cannot support a dense cover of grass.
Aging Your Mountain Cedars
There’s a general perception that mountain cedars do not grow very large or that large ones aren’t very old. Neither is true. Although mountain cedars can quickly spread across a rangeland, their growth once established is very slow. It is, after all, a juniper– and junipers are long-lived species.
Measure the trunk diameter in inches 4.5′ up from the ground. Then divide the diameter by .1 and .06
Using .1 and .06 gives a range of ages. If your tree is growing near water in bottomland soils, it will be closer to the .1 number. If your tree is growing on a drier hillside, .06 will be more accurate.
For instance, if your tree has a 12″ wide trunk (measured 4.5′ up from the ground), then it will be about 120 years old if it’s growing near water, but at least 200 years old if growing on top of a hill.
Limestone Junipers of Texas
Mountain cedars are native junipers that prefer limestone karst country. They are most abundant on the eastern Edwards Plateau and on karst country north to the Red River. They are less common on the semi-arid western Edwards Plateau:
Ashe juniper (Juniperus ashei) is the most common mountain cedar. It typically grows as a bushy shrub and is most often seen colonizing degraded rangelands and hillsides. Its range extends to the Ozark Mountain in Missouri.
Adams Juniper (Juniperus ovata) is a more ancestral juniper species that would have been more widely dispersed during the last ice age (10K+ years ago). Current populations exist in western New Braunfels (several are growing in Mission Hill Park) and western Comal County. There is also a population near Big Bend National Park. This species is also called Lemon Cedar due to its lemon-colored sapwood (Ashe Juniper sapwood is white). It is a woodland/forest tree.
Hybrid Juniper is a hybrid of Ashe Juniper and Adams Juniper. Ashe Junipers do not hybridize with any other juniper species. The hybrids can be found growing as a tree in and near forests and woodlands.
Field observations reveal that Adams junipers and the hybrids tend to grow as trees inside established woodlands and forests of the Eastern Edwards Plateau and karst country regions northward.
Two other juniper species can be found growing on limestone karst country, but neither has a preference for limestone:
Eastern Red Cedar (Juniperus virginiana) that grows from the central region of Texas to the Atlantic Ocean, can occasionally be found growing on limestone karst country. It does not hybridize with other limestone junipers.
Redberry Juniper (Juniperus pinchotti) is found mostly on the drier western Edwards Plateau and grows as a shrub. Although common on karst country, it is just as common on non-karst country. It does not hybridize with other limestone junipers.
Project Bedrock informally named Adams Juniper to honor Dr. Robert Adams of Baylor University who identified this separate species. It is also called Lemon Cedar.
The Two Types of Cover
Cedar Thicket
Dense cover, less than about 40 years old, dominated by bushy cedars working as pioneers to regenerate degraded karst country. Can occur where forests once grew or in open rangelands.
Helps regenerate karst function.
- increase karst porosity
- enhance spring flows
- rebuild soil structure & biology
- reduce erosion
- protect new plants
- provide wildlife winter shelter and food
Can take 5 – 75 years based on level of degradation–however we can use nature-based solutions to help speed up the process.
Cedar Forest
Mostly continuous to completely continuous canopy cover. Will contain a mix of hardwoods and mountain cedars (oak-juniper forest) OR be dominated by tree-like tall mountain cedars growing close together (cedar brakes).
Sustains healthy karst function.
- protects karst porosity
- sustains spring flows
- protects soils
- controls erosion
- moves carbon deep
- supports diverse wildlife habitat
- feeds winter wildlife
Forest cover can be old-growth, regenerating old-growth, or areas where forests should be reestablished. Most of our forests are classified as dryland forests.
The dense thickets of bushy mountain cedars we see today are pioneering (or colonizing) thickets. These are NOT cedar brakes. True old-growth cedar brakes are 250+ years old dense forests dominated by tall, timber-like mountain cedars. Historically, pioneer thickets were uncommon, but true cedar brakes were common. Pioneer thickets are acting as pioneers because to help regenerate degraded Texas karst country.
True old-growth brakes and juniper-oak forests make up the bulk of dryland forests in Texas karst country. They are both characterized by a mostly continuous canopy of shorter (30-60′ tall) trees and can be found in bottomlands and on hillsides. The rolling terrains between bottomlands and hillsides with deeper soils historically were more characterized as open, wooded prairies.
Each cover type needs to be managed differently because they play different ecological roles.