OOS 39-2
Developing an understanding of how to map using the current National Vegetation Classification: Recent improvements and suggestions for better representation and accuracy
The standardization of the principles and methodologies of photo interpretation in conjunction with the gathering of comprehensive and detailed on-site field data used to develop vegetation description and keys have allowed for the creation of accurate, fine scale vegetation maps that conform to the National Vegetation Classification Standards (NVCS). The development of these standards over the past 20 years comes at a time when high resolution sub meter digital imagery over extensive and continuous areas of land is increasingly available to the public at little or no cost.
The use of on-screen heads-up interpretation using high resolution digital imagery allows the photo interpreter to apply the techniques of manual photo interpretation developed over the last several decades, thus eliminating the intermediate steps involved in correcting the results of computer generated linework. This direct process requires the photo interpreter to understand the biogeography and resultant plant species responses to the landscape of the region being mapped, in addition to the varying ranges of photo-image signatures that typify those plant communities, in order to conform to and accurately map to the NVC standards.
Results/Conclusions
The end data from this direct remote sensing of the vegetation has resulted in highly accurate and standardized map products depicting Alliance-level classification in addition to detailed structural characteristics of over 15 million acres of critical habitat in California during the past two decades. The final products have proved highly valuable to agencies such as the National Park Service, California Department of Fish & Wildlife, California State Parks, The Nature Conservancy, and the California Native Plant Society as well as many county, quasi-governmental, and local organizations. The standardized vegetation maps are used in studies that evaluate the remaining habitat for species such as the Stephens kangaroo rat, least bell’s vireo and Kirtland’s warbler to mention just a few. Furthermore, they are also used to help predict the path, intensity and likelihood of catastrophic fires in addition to providing valuable information in monitoring the stand health of forest communities threatened by invasive species, insect infestations and other diseases which threatens vegetation nationwide. The three phased effort (ground assessment, photo interpretation and map verification) needed to achieve the final product requires considerable planning and time; however, the end product has been shown to be well worth the often substantial upfront costs.