After weed managers have identified invasive plant species and understand why and how the species have become a problem in an area, weed managers need to know how far the weeds have spread. Weed managers can devise strategies to quantify and then control an invasion when they understand the plant biology, ecosystem dynamics, and extent of the problem. Weed inventories are an important tool for weed managers because they provide data that is important to developing effective weed-control strategies.

Weed managers perform inventories for the following reasons:

Areas that weed managers inventory vary in size and shape. Weed managers may target a small area, such as a single campground, or a large area, such as a 10,000-acre wildfire. Inventories may target a single species, for example, yellow star thistle. Inventories may also be general, for example, one inventory may target 20 or more species on a state noxious weed list.

In actual weed inventories, timing is critical for accuracy. Timing varies with the targeted species and the plant identification skills of the field staff. Inventories usually occur when the target species are in full bloom, because the weeds are most obvious to observers when in this stage. Weed managers conduct aerial surveys only when weeds are in bloom and easily identified from the air.

The procedure for conducting inventories varies, depending on the goals of the inventory. Effective problem solving to meet project goals is an essential aspect of any inventory. Weed managers must carefully consider the purpose of the inventory, species in question, amount of time available, size of the area, and size and skill of the field staff. In some situations, it might be necessary and possible to canvas every inch of ground for weeds. In most situations, weed managers devise a plan to walk a transect or move out from points of known infestation or high-risk potential.

Field work involves long hours of driving or walking in remote locations. In actual situations, it is essential that weed inventory data be usable. The staff conducting the inventory must adhere to strict data collection standards. To ensure that data will be usable and can be shared among colleagues, states have developed elaborate protocols for data collection. There are protocols for recording the following information when collecting data:

Weed managers and their staff may record inventory data by using Global Positioning System (GPS) technology, writing information on a map or photo, or recording legal descriptions using township, range, and section. The individual who conducts the inventory should make a note of the accuracy of the data. The accuracy depends on the method and capability of the equipment used and the skill of the individual recording the data.

Species are often recorded using abbreviations or codes, such as the naming and code system used by the USDA National Resource Conservation Service (NRCS). Recording methods vary by location. Sometimes field staff will enter data by hand onto a paper form, which might later be entered into a computer database for eventual inclusion in a Global Information System (GIS) layer for analysis or mapping. More often, field staff will enter data directly into a GPS data dictionary. The data is then transferred directly into a GIS database.

In this unit, students will learn what weed inventories are, why they are important, how to conduct an inventory, and the importance of collecting accurate data. Students should grasp the concept that inventories are unique. Inventories must be crafted to achieve the objectives of the project or inventory. Students should also learn how to ask questions to develop an appropriate plan for the inventory.

Invent an Inventory – Explains what weed inventories are and why they are important. After creating an imaginary weed infestation, students practice creative problem solving to devise a weed inventory and method of control.

The Right Inventory for the Job – Expands and reinforces students’ knowledge of weed inventories. Students devise inventory strategies for two weed-invasion scenarios.

Practicing Protocols – Emphasizes the importance of understanding and adhering to data collection protocols. Students apply their knowledge of protocols and inventories to collect data in the field.

Dollars and Sense – Refines students’ knowledge of weed inventories. Students develop a weed-control plan for a realistic scenario.

Sample Inventory Protocol – Explains how to conduct a weed inventory using a transect line. Students set up a transect and conduct a live stem count.