Vegetation classification and map: White Sands National Monument

Muldavin, Esteban; Chauvin, Yvonne; Schulz, Keith; Neville, Teri; Neville, Paul; Smith, Jacqueline; Fettes, Anthony

A vegetation classification and map for White Sands National Monument, New Mexico is presented as part of the National Park Service Inventory & Monitoring – Vegetation Inventory Program to classify, describe, and map vegetation communities in more than 280 national park units across the United States. Building on a legacy mapping project from the 1990s, we updated the classification and built a new map using the latest aerial imagery and mapping technologies to meet current NPS standards. Embedded in the enclosed Tularosa Basin is a world-renowned and unique gypsum landscape. Along with its many gypsum landforms such as dunes, alluvial flats, playas, and desert piedmonts, the vegetation communities and ecology of White Sands National Monument are as dynamic as they are diverse. Following the US National Vegetation Classification standard (USNVC), we identified 50 plant associations, many of them unique to the Southwest. Within the gypsum dune system alone, we describe 19 gypsophilous plant associations that belong to the USNVC Chihuahuan Gypsophilous Grassland and Scrub groups. They range from shrublands that colonize and stabilize the dunes to a variety of grassland and shrublands that dominate the wind-scoured interdune flats. In addition, maintained by the shallow groundwater of the basin, there are pockets of riparian woodlands (Western Interior Riparian Forest & Woodland – NVC Group G797) dominated by Rio Grande cottonwood. Surrounding the dunelands are expansive alluvial basin bottomlands, alkali flats, and playas, which support grassland and shrubland associations dominated by salt-tolerant species. Here, we identified four associations belonging to the Chihuahuan Lowland Basin Semi-Desert Scrub and Grassland groups (G299 and G489, respectively) plus eight from periodically flooded areas that belong to the North American Desert Alkaline-Saline Wet Scrub (G537) and North American Desert Alkaline-Saline Marsh & Playa (G538) groups. In addition, there are areas dominated by a combination of quartz and gypsic sands that are represented by two Chihuahuan Desert Sand Scrub (G287) associations and one Chihuahuan Sandy Plains Semi-Desert Grassland (G491) association. Some of these sandy zones are dominated by honey mesquite coppice dunes and are part of the North American Warm Desert Ruderal Scrub group. Along the western margin of the monument are alluvial fan piedmonts composed of sediments derived from the neighboring San Andres Mountains limestones and sandstones. Here, we identified four associations of the Chihuahuan Creosotebush - Mixed Desert Scrub Group, which is widespread throughout the Chihuahuan Desert. Lastly, there are stands of exotic and invasive saltcedar (Tamarix chinensis) that occur in both the dune areas and surrounding flats. These are represented by four associations belonging to the Interior West Ruderal Riparian Forest & Scrub. The classification was based on 737 vegetation plots collected between 1993 and 2016. Full descriptions and diagnostic keys to the plant associations along with an overall plant species list are provided as appendices. Based on the vegetation classification and associated plot data, the vegetation map was developed using a combined strategy of automated digital object-oriented image classification and direct-analog image interpretation of four-band NAIP aerial photography from 2005, 2014, and 2016, and Landsat Enhanced Thematic Mapper satellite imagery. The map was designed to facilitate ecologically based natural resources management at a 1:24,000 scale with 0.5-ha minimum map unit size. The map legend was hierarchically structured with an upper Level 1 of nine map units corresponding in most cases to the USNVC Group level and a Level 2 composed of 22 nested map units reflecting various combinations of plant associations.

Vegetation classification and map: White Sands National Monument

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