Death by Cavitation - Mysterious Juniper Death


In May 2003, as the orange brown color of death began to finger its way through Central Oregon’s juniper forests, local forest and rangeland extension agents began to field calls from concerned people…

What could be killing the trees? Was it a new disease or insect attack? Simply freezing damage from an unusually frigid cold spell the previous October….? Or was it something more fundamentally sinister….?

To answer this riddle, we must travel deep into the inner workings of plants themselves….we must enter the Xylem zone…. 

 Stubble Height Predicts Livestock Grazing of Shrubs


Managing Livestock grazing in riparian areas along streams can be facilitated by predicting when cattle are likely to focus primarily on eating grass and when they are likely to begin consuming shrubs. Cattle, like most ungulates, have teeth on the lower jaw, but a dental pad instead of individual teeth on their upper jaw. They feed by sweeping forage into their mouth with the tongue and then ripping off a portion to grind against the dental pad. This makes it difficult for them to bite off short plants. Field observations of cattle grazing riparian meadows suggest that green growing grass is preferred to shrubs as long as grass height is 3 inches or more. Once herbaceous stubble height drops below 3 inches, cattle have trouble efficiently harvesting it, and begin to consume palatable shrubs or trees such as willows.  As herbaceous vegetation matures (and dries), it becomes less attractive and cattle begin to consume green woody feed rather than dry grass, regardless of grass height.

Stubble Height to Evaluate Livestock Grazing Impacts 


Using height of forage residue remaining after grazing of rangelands and associated riparian strips is as common as it is controversial. Residue remaining after livestock grazing is easily observable and is related to the amount of plant material left to protect soils, support future plant growth, and to feed other consumers in the ecosystem. It is, however, only one of several structural attributes that together drive subsequent ecosystem processes. Management objectives are most often aimed at re-establishing or maintaining a properly functioning ecosystem. Residue standards are tools to help move towards these goals. They are not the goals themselves. While residue can be very useful as a "trigger indicator" or an "end-point indicator" to make management decisions, such as when to move livestock on to other areas, it is by itself, not sufficient to evaluate whether broader management objectives are being achieved. Evaluation of current land status and management success is probably better done with ecological indicators such as Greenline monitoring, or Rangeland Health assessment.

Forage Utilization Photoguides.


Optical estimates of forage use by livestock or large native herbivores such as deer or elk are greatly improved if a visual reference  is available. Use of a visual reference, such as a set of pictures representing known levels of grazing or browsing use (a photoguide) is very helpful. However, it does not entirely replace rthe need for training of people who will be making estimates of grazing use. Photoguides for specific plants can be easily made by simply removing known amounts of current season's growth from plants and then photographing the remaining plant. In the field, individual grazed plants are compared to the pictures and their percent of tissue missing (% utilization) is recorded. The resulting estimates of % utilization are not exact, but are probably adequate to support decision making and to identify general trends in forage use.

About DoctorRange

Dr. Sharrow's pictureDr. Sharrow is Professor of Rangeland Ecology and Management at Oregon State University, USA, where he has taught undergraduate and graduate level natural resources classes for the past 31 years.

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