Effects of Land Management Practices on Plant Invasions in Wildland Areas

The alteration of natural ecosystems by humans and anthropogenic dispersal of plant propagules beyond their native ranges have facilitated the dramatic spread and increase in dominance of nonnative plants worldwide since the late 1800s (Hobbs 2000;Mack et al. 2000). The amount of ecosystem alteration is related to predominant land uses,which can be summarized into four categories of increasing impact: (1) conservation - nature reserves, wilderness; (2) utilization - pastoralism, non-plantation silviculture, recreation; (3) replacement - cropping agriculture, plantation silviculture; and (4) removal - urbanization, mining, industrial development (Hobbs and Hopkins 1990; Hobbs 2000). The rate at which propagules are dispersed into new regions is largely related to the frequency and intensity of human activities, which generally covary with the degree of ecosystem alteration among the four land use categories.

Compared to areas where replacement or removal land uses are the norm, the management of plant invasions tends to be more complicated where conservation or utilization land uses prevail. The latter two land uses emphasize the need to maintain the integrity of natural ecosystems, whereas the former two do not require that natural ecosystem properties be maintained, and in some cases involve replacing them with simpler ecosystems (e.g., cropping monocultures). Options for controlling invading plants are more limited when their potential negative effects on native ecosystems may preclude their usage. This chapter is focused on conservation and utilization land uses that occur where native ecosystems are largely present and functioning, otherwise known as wildland areas.