Aerial photographs as a tool for assessing the regional dynamics of the invasive plant speciesHeracleum mantegazzianum

Abstract

Summary 1.The initiation of an invasion event is rarely dated in studies of alien plants. Data from aerial photographs documenting the invasion from the outset facilitate the quantification of the rate of spread, allowing researchers to analyse species' population dynamics and providing a basis for management. 2. For 10 sites invaded by Heracleum mantegazzianum in the Slavkovsk y les, Czech Republic, aerial photographs from 11 sampling dates between 1947 (before invasion started) and 2000 were analysed. The area covered by the invader was measured digitally in a 60-ha section of landscape, and information obtained on invaded habitats, year of invasion, flowering intensity and structure of patches. Invaded area was regressed on residence time (time since the beginning of invasion) and regression slopes were used to measure the rate of spread. Data were analysed by  , multiple regression and path analysis. 3. Pastures and fields contributed 84·7% to Heracleum total cover, forest and scrub 13·7% and human settlements 1·6% at the later stage of invasion. The direct effect of the rate of invasion on invaded area (0·82) was greater than that of residence time (0·22), but the total effect (direct and indirect) of residence time was only slightly less (0·79) than that of the rate of invasion (0·82). As invasion proceeded, the populations spread from linear habitats to the surrounding landscape. Mean rate of areal spread was 1261 m 2 year − 1 and that of linear spread 10·8 m year − 1 . Flowering intensity did not exhibit any significant trend over time. 4. Synthesis and applications. The strong effect of the rate of spread on the invaded area indicates that local environmental conditions hardly limit the spread of Heracleum . The species is easily detectable on aerial photographs taken at flowering and early fruiting times, from June to August. Knowledge gained from aerial photographs allows managers to identify dispersal foci and to focus control efforts on linear landscape structures with developing populations. Knowledge of the rate of spread and habitat vulnerability to invasion facilitates the identification of areas at highest risk of immediate invasion.

The effects of temporally variable dispersal and landscape structure on invasive species spread

“…Remotely sensed distribution maps have been cited as one of the most accurate methods for estimating spread (Hastings et al 2005). All remote sensing of invasive plant species spread to date has used aerial photography, typically analyzed by manual photointerpretation, due to the length and value of the photo record (Lonsdale 1993, Brown and Carter 1998, Higgins et al 2001, Buckley et al 2005, Mu¨llerova´et al 2005, Maheu-Giroux and de Blois 2007, Browning et al 2008. However, the limitations of photointerpretation restrict analyses to species that are broadly different from the invaded communities, for example, to shrub encroachment of deserts and grasslands (Brown andCarter 1998, Browning et al 2008), pine invasions (Higgins et al 2001, Buckley et al 2005, and species with vivid floral displays (Mu¨llerovaé t al.…”

Impacts of Solidago Gigantea, Prunus Serotina, Heracleum Mantegazzianum and Fallopia Japonica Invasions on Ecosystems

“…Using aerial photographs from 11 sampling dates between 1947 (before H. mantegazzianum invasion started) and 2000, Müllerovà et al (2005) found that pastures and fields contributed 84.7 % to Heracleum total cover, forest and shrub 13.7% and human settlements 1.6 % at later stages of invasion. The authors found that as invasion proceeded, the populations spread from linear habitats to the surrounding landscape with the mean rate of aerial spread of 1,261 m 2 per year and linear spread of 10.8 m per year.…”

Does the Data Resolution/Origin Matter? Satellite, Airborne and Uav Imagery to Tackle Plant Invasions

“…Müllerová et al, 2013;Jones et al, 2011). Detection of herb species is only possible if the data provide enough spectral and/or spatial details, the species are distinct from their neighborhood, form dense and uniform stands, and/or are large enough to be detected (Maheu-Giroux and de Blois, 2004;Müllerová et al, 2005). The potential for invasive species monitoring using RS is still not fully exploited and for the majority of invasive species there are no detection algorithms described.…”