Regional Interpretation - Other (California annual grasslands and Florida)
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NRI Rangeland Resource Assessment - California and Florida Regional Interpretation (PDF; 1.9 MB)
The California annual grasslands and Florida are unique for different reasons. The California annual grasslands represent an area where a group of non-native plant species (primarily annual grasses) have replaced the pre-European settlement plant communities, which included perennial grasslands, savannas, and woodlands with a perennial grass-dominated understory. These areas are now dominated by and managed as annual grasslands. There is continuing debate about the extent to which the original plant communities can be restored, and in which parts of the original distribution of these plant communities the potential for restoration might be greater. The challenge of assessing, monitoring, and managing land that has crossed an ecological threshold in California is similar to that encountered in many other parts of the country where native plant communities have been replaced by functionally and structurally different communities dominated by invasive species that may be either native or non-native. California is unique because of the spatial extent of the transformation.
Florida is unique because of the dominance of its rangeland by sub-tropical grasslands, relatively high precipitation, high water tables, flat topography, and sandy soils. Consequently, hydrologic function indicators that are important for reflecting changes in infiltration and runoff in the other regions are much less sensitive in Florida. Modification of near-surface hydrology associated with depth to shallow water tables and length of inundation periods is poorly reflected in this assessment. Similar limitations apply to hydrologic function assessments in Louisiana coastal marshes. Whereas changes in the composition and productivity of plant communities in most rangeland in the Intermountain and Southwest regions are significantly affected by soil and vegetation factors that affect water infiltration and runoff, the flat, sandy soils of Florida experience little runoff.
The unique characteristics of California annual grasslands and Florida limit the ability to apply and interpret assessments of the three rangeland health attributes, albeit in slightly different ways. In the case of California, continuing debate about the reference conditions to be used for evaluations and incomplete implementation of ecological sites prevented development of the ecological site-specific reference sheets necessary to carry out the evaluations. In the case of Florida, the qualitative evaluation protocol has not been well tested and may need refinement to meet the needs of a subtropical system. In both cases, however, the quantitative indicators provide an appropriate and useful baseline for future monitoring.
Soil and Site Stability
Soil and site stability (Figure 1) was virtually unchanged from potential in Florida. The flat landforms and coarse sandy soils found in most of the state make this area highly resistant to degradation, while high levels of plant production facilitate rapid recovery where degradation does occur. Low soil aggregate stability values (Figure 2) were recorded on some plots largely because coarse sandy soils have low potential stability. In California, the quantitative indicators of soil stability all reflected the effects of high annual cover and litter accumulation in the absence of recent fire or extreme drought; there was little bare ground (Figure 3) and soil aggregate stability values were high and few plots had large intercanopy gaps.
The qualitative assessment of hydrologic function (Figure 4) in Florida showed no significant departure from potential. This landscape is relatively resistant to the types of hydrologic degradation that are reflected in the indicators included in the evaluation. For the most part, however, these indicators appear to be less sensitive to changes in near-surface hydrology that are critical for the maintenance of these ecosystems. In California, the quantitative indicators of hydrologic function again reflect the positive effects of high annual plant cover on ground cover during most years, but are not sensitive to changes in hydrologic function associated with the changes in the soil profile following conversion from a perennial- to an annual-dominated system.
Non-native species (Figures 5-6) and shifts in the relative proportion of native plants have led to significant changes to plant communities on some areas of Florida's rangeland, resulting in a reduction in biotic integrity (Figure 7). In California, the quantitative indicators of plant community composition reflect the virtually complete conversion of these rangeland to dominance by exotic species.
Figures 5-6. Non-Federal rangeland where non-native species are present and where they make up at least 50 percent of the plant cover
(Source: Non-Native Plant Species Table 2)
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