Military training from an ecological perspective represents a unique set of periodic landscape scale disturbances. There are two types of training related disturbance that occur on military lands, physical disturbance from vehicles maneuvering across the landscape and fire. Military vehicle maneuvers often produce intense localized disturbance during training exercises. Wildlfire is a common occurrence due the use of live tracer rounds and other incendiary ordnance while prescribed fire is used for a variety natural resource management purposes. In general, plant invasion occurs when resources (i.e. space, sunlight, soil resources) become available in the presence of suitable propagules. Physical disturbance from military training activities release resources that may facilitate establishment, spread and perpetuation of invasive species. Conversely frequent wildfire may inhibit invasive species by favoring fire adapted native species. The objective of our study was to use plant community and military disturbance data collected over a ten year period (1994 -2005) at Fort Pickett, Virginia to investigate relationships between invasive plant species and the two types of disturbance common on military training lands. We categorized each plot according the presence or absence of military vehicle traffic and fire frequency. We used a two-way analysis of variance to investigate the relationship between the two disturbance factors and total invasive species cover, total cover of non-native and native legumes and the top 5 (in terms of cover) individual invasive species.
Results/Conclusions
In general physical disturbance favored and high fire frequency reduced invasive species cover. Total cover of invasive species was significantly higher (P< 0.05) in plots where physical disturbance was present. The total cover of invasive species was generally lower in the high fire frequency plots but the results were not significant. Native legumes showed a significant reduction in cover in the physical disturbance plots while non-native legumes increased. Fire generally increased native legumes and decreased non-native legumes though the results were not significant. Of the top 5 invasive species tall fescue (Festuca elatior) showed the greatest differences between physical disturbance and fire. The cover of tall fescue was significantly higher in physically disturbed plots and lower in the high fire frequency plots. Japanese honeysuckle (Lonicera japonica) had significantly lower cover in the high fire frequency plots. Results from this study will play a key role in developing hypotheses that will test the linkages between military disturbance, invasion dynamics, and persistence of invasive species.
