Spring Vegetation Monitoring

The dry wash of Cottonwood Springs in Joshua Tree National Park
Cottonwood Springs in Joshua Tree National Park.

NPS Photo

Overview

Spring riparian areas in Mojave Desert Network parks are some of the most significant habitats for maintaining biological diversity and some of the most threatened habitats.

In these parks, as elsewhere in the arid west, land-use practices such as livestock grazing, surface water diversion, groundwater withdrawal, mining, and introduced invasive species have radically altered ecological processes and led to losses in riparian productivity and biodiversity. In many riparian areas, plant communities are now dominated by non-native tamarisk (Tamarix spp.), a woody plant that accesses groundwater more easily and tolerates saline soils better than native plant species.

A significant number of species of special concern are associated with riparian habitat in Mojave Desert Network parks, including the Southwestern willow flycatcher (Empidonax traillii extimus), least Bell's vireo (Vireo bellii pusillus), and the relict leopard frog (Rana onca).

Monitoring Objectives

  • How stable are riparian plant communities through time as measured by species composition, abundance, and structure? Are major shifts in dominant vegetation observed?
  • Is the areal extent of Network park riparian plant communities declining?
  • What are the trends in abundance and composition of targeted invasive plant species in riparian communities?
  • Are changes in vegetation cover, composition, and structure correlated with long-term changes in discharge or stream flow rates?
  • Are changes in native vegetation communities associated with changes in exotic plant species cover and species composition?

Last updated: August 28, 2018