Dispersal potential rather than risk assessment scores predict the spread rate of non‐native pines across New Zealand

Wyse, Sarah V.; Hulme, Philip E.

doi:10.1111/1365-2664.13947

Cited by 16 publications

(21 citation statements)

References 78 publications

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“…Previous research efforts have focussed on trying to elucidate which plant traits give some pine species a higher propensity for invasive spread in their introduced ranges, where they have been planted extensively primarily for forestry purposes (Richardson & Higgins, 1998). Among wind‐dispersed pines, those species with the highest dispersal abilities due to their small seeds and low wing‐loadings (and therefore low diaspore terminal velocity) are understood to be the most invasive (Rejmánek & Richardson, 1996; Wyse & Hulme, 2021a). Here, we hypothesised that the pines with the greatest spreading abilities would be less likely to display within‐species competition–colonisation trade‐offs, due to the associated reduction in dispersal distances that are likely to result from such a trade‐off (Figure 1).…”

Section: Discussionmentioning

confidence: 99%

Competition–colonisation trade‐offs are found among but not within wind‐dispersed Pinus species

Wyse

Hulme

2022

Functional Ecology

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1. The competition-colonisation trade-off is recognised as a key mechanism for diversity maintenance, whereby weak competitors can avoid competition with stronger competitors due to their greater dispersal ability. To date, most theoretical and empirical work has focused on trade-offs among different species yet a within-species perspective is crucial to assess the scope for natural selection on competition-colonisation trade-offs.2. For six wind-dispersed Pinus species encompassing a wide range of seed masses, we examined whether within and among species there was evidence that heavier seeds typically disperse shorter distances but produce seedlings that are stronger competitors with a higher likelihood of successful establishment, under different treatment conditions.3. Within species, we found seedling establishment to be independent of diaspore terminal velocity (a measure of dispersal potential), which would maximise the variation in potential dispersal distances and locations reached by the seeds shed from a parent tree, and therefore the chances that some offspring will reach a favourable recruitment site. However, among Pinus species the likelihood of seedling emergence and survival was higher in species that produce heavier seeds with higher terminal velocity. 4. We found a marked competition-colonisation trade-off among all six species consistent with expectations from coexistence theory. In contrast, within species, there was no evidence of competition-colonisation trade-offs for any species, despite differences in the relationships between diaspore mass and terminal velocity. This is consistent with weak selection within species for a competitioncolonisation trade-off. The results suggest that within-species trade-offs do not influence the risk of invasive spread.

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Section: Discussionmentioning

confidence: 99%

Competition–colonisation trade‐offs are found among but not within wind‐dispersed Pinus species

Wyse

Hulme

2022

Functional Ecology

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“…Unfortunately, pine species favoured by the forestry industry are generally those with the most rapid growth rates and greatest heights at maturity and, as a result, are also those most likely to escape cultivation and spread rapidly (McGregor et al, 2012;Wyse & Hulme, 2021). The spread of pines from plantations represents a substantial and intractable weed problem where non-native conifers form the bulk of commercial forestry plantings (Nuñez et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Pines ( Pinus species) have long been cultivated for timber and other forest products, with the result that they have been planted extensively outside their native range, particularly in the Southern Hemisphere (Le Maitre, 1998; Richardson & Rundel, 1998). Unfortunately, pine species favoured by the forestry industry are generally those with the most rapid growth rates and greatest heights at maturity and, as a result, are also those most likely to escape cultivation and spread rapidly (McGregor et al, 2012; Wyse & Hulme, 2021). The spread of pines from plantations represents a substantial and intractable weed problem where non‐native conifers form the bulk of commercial forestry plantings (Nuñez et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Quantifying the risk of non‐native conifer establishment across heterogeneous landscapes

Wyse

Etherington

Hulme

2022

Journal of Applied Ecology

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Pines (genus Pinus) are cultivated extensively for forestry purposes, particularly in regions that are outside the genus' native range. The most common forestry species are also typically those most likely to escape cultivation and spread rapidly, and thus pines constitute a substantial weed problem in many regions. However, there is limited knowledge of the factors underlying the spread of pines from plantations. Assessments across heterogeneous landscapes are required to provide rigorous data to support management tools and policies aiming to protect vulnerable ecosystems from pine invasions. We examined the spread of Pinus radiata from forestry plantations over a ~9,000 km2 landscape on Banks Peninsula, New Zealand. We used ground‐based surveys from a set of viewpoints to determine tree locations, coupled with geographical information system (GIS) viewsheds to define the area surveyed. We used boosted regression trees to build a habitat model for P. radiata establishment on Banks Peninsula. We surveyed an area approximately 107 km2, recording 470 naturally established P. radiata individuals. Our habitat models suggested that proximity to the nearest plantation forest was the most important variable predicting P. radiata establishment, with individuals most likely to establish within 150 m of a plantation. Individuals were also most likely to establish in early successional shrub communities, proximate to roads, and on steeper topography. Highly grazed habitats were least vulnerable to P. radiata establishment. The slope and aspect of the source plantation influenced the distances from the plantation at which P. radiata individuals were recorded, with individuals recorded furthest away likely to have originated from plantations that were south‐facing or on steeper slopes, and therefore most exposed to strong winds. Synthesis and applications. Our findings on distances from plantations at which individuals established, vulnerable habitats, and the interactions we detected among our predictor variables, can be extended to aid management of non‐native conifer plantings elsewhere in the Southern Hemisphere. These data can be used to contribute to improvements of decision support systems that assess likely spread risk from non‐native conifer plantings. Such tools can reduce the likelihood of future pine establishment, potentially preventing biological invasions.

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“…Many of the most problematic conifer species are those able to spread long distances via wind dispersal (Wyse & Hulme, 2021), while habitat suitability, grazing pressure and other environmental conditions are fundamental in determining their establishment success (Ledgard, 2001). Species-environment relationship analyses (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…and Pseudotsuga menziesii , widely planted for forestry purposes, are a particular threat throughout the southern hemisphere, predominantly in low‐stature plant communities such as grasslands and shrublands where high light levels facilitate their establishment (Nuñez et al., 2017; Richardson & Rejmánek, 2004). Many of the most problematic conifer species are those able to spread long distances via wind dispersal (Wyse & Hulme, 2021), while habitat suitability, grazing pressure and other environmental conditions are fundamental in determining their establishment success (Ledgard, 2001). Species–environment relationship analyses (e.g.…”

Section: Introductionmentioning

confidence: 99%

Combining laser rangefinder and viewshed technologies to improve ground surveys of invasive tree distributions

2021

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Quantifying the spatial extent, location and habitat associations of invasive tree species is critical to predict their future spread and prioritise areas for management. Species–environment relationship analyses are useful tools for understanding and predicting the potential geographical distribution of these species; however, such tools require rigorous and extensive data about species presence and, crucially, the area surveyed. Here, we describe a method for performing ground‐based visual surveys of invasive trees from a set of viewpoints that utilises laser rangefinder and global navigation satellite system (GNSS) technology to detect tree locations. We then highlight the novel use of geographical information system (GIS) viewsheds as a tool to define the area surveyed. Using the invasive conifer, Pinus radiata, as our target, we undertook a ground‐truthing exercise for 50 trees established in the wild to assess the accuracy of the method and determine the suitable spatial resolution for GIS data that would be used in subsequent species–environment relationship analyses. For these trees, location error was positively related to distance from the tree to the viewpoint. The calculated locations for all trees within 600 m of the observer were within 25 m of the location as determined by the GNSS unit, with a median location error of 4 m. These results indicate that data of a resolution suitable for mapping invasive trees can be efficiently collected over large areas. We also outline suggestions and instructions for computing the viewsheds to determine the surveyed area. This approach allows for efficient collection of accurate data on the occurrence of non‐native trees and the land area surveyed. These data can underpin species–environment relationship analyses that then form the basis of risk maps for areas prone to future invasion. Given the speed and accuracy with which data can be obtained using this method, and the use of standard and easily accessible field equipment and GIS software, we recommend this approach to other spatial and invasion ecologists.

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Dispersal potential rather than risk assessment scores predict the spread rate of non‐native pines across New Zealand

Cited by 16 publications

References 78 publications

Competition–colonisation trade‐offs are found among but not within wind‐dispersed Pinus species

Competition–colonisation trade‐offs are found among but not within wind‐dispersed Pinus species

Quantifying the risk of non‐native conifer establishment across heterogeneous landscapes

Combining laser rangefinder and viewshed technologies to improve ground surveys of invasive tree distributions

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