Modelling seed retention curves for eight weed species on clothing

The ecological footprint of outdoor activities: Factors affecting human-vectored seed dispersal on clothing

In the Anthropocene, humans are among the most abundant long-distance seed dispersal vectors globally, due to our increasing mobility and the growing global population. However, there are several knowledge gaps related to the process of human-vectored dispersal (HVD) on clothing. In a multi-site field experiment covering various habitat types in three countries of Central-Europe, we involved 88 volunteer participants and collected 251 HVD samples and 2008 subsamples from their socks and shoes. We analysed the number of diaspores and species in the samples. Specifically, we studied the effects of site characteristics (variables related to habitat types and season), vector characteristics (activity type, gender, clothing type, shoe type) and plant characteristics (species pool of the visited habitats and plant traits) on the number of diaspores and array of species dispersed. We assessed the habits of people that could be relevant for HVD with a questionnaire survey. A total of 35,935 diaspores of 229 plant taxa were identified from the samples, which indicates a huge potential of HVD in dispersing diaspores across habitats and regions. Most diaspores were recorded in grassland habitats, and more diaspores were dispersed during fieldwork than excursions. Clothing type also played a decisive role: there were more diaspores and species when wearing short-top shoes and short trousers than long ones. Even though our study was carried out mainly in natural or semi-natural habitats, a large number of dispersed species were disturbance-tolerants and weeds and only a few were specialists, suggesting the controversial role of HVD in conservation. At the individual level, people can reduce the number of diaspores through their clothing choices and diaspore removal habits, while providing adequate equipment for staff, operating cleaning stations, and increasing awareness of employees are main ways in which unintended diaspore dispersal can be tackled at the institutional level.

Mountain bike riding and hiking can contribute to the dispersal of weed seeds

Mountain biking and hiking are popular, but both recreational activities can contribute to the unintentional dispersal of seeds including non-native plants that cause environmental harm (e.g. environmental weeds). Addressing the requirement for more information about the ecological impacts of recreational activities, seed dispersal from mountain biking and hiking were compared under different climatic and environmental conditions. Seeds from a range of graminids and forbs were found to attach to the mountain bike, rider and hiker, including environmental weed seeds, on trails and in-field in montane Australia. While the composition of seeds differed between the two activities, no significant differences were found between traits, such as natives or environmental weed, graminids or forbs, perennial or annual, large or small, attachment or no attachment structures, although sample sizes were small. Few seeds attached to the mountain bike, rider or hiker on dry trails, some seeds attached when trails were wet, but more seeds attached when riding/hiking off trail in a field. Cleaning clothing and bikes and avoiding areas with environmental weed seeding could reduce the risk of this type of unintentional human mediated dispersal, but compliance with such measures may be challenging. Given the increasing popularity of mountain biking and the current controversy about the relative impacts of mountain biking in areas of high conservation concern, additional research assessing severity, duration and range of impacts of mountain biking on soil, wildlife, waterways and vegetation is critical.

The diversity of microfungi associated with grasses in the Sporobolus indicus complex in Queensland, Australia

There are five closely related Sporobolus species, collectively known as weedy Sporobolus grasses (WSG) or the rat's tail grasses. They are fast growing, highly competitive, unpalatable weeds of pastures, roadsides and woodlands. An effective biological control agent would be a welcomed alternative to successive herbicide application and manual removal methods. This study describes the initial exploratory phase of isolating and identifying native Australian microfungi associated with WSG, prior to evaluating their efficacy as inundative biological control agents. Accurate species-level identification of plant-pathogenic microfungi associated with WSG is an essential first step in the evaluation and prioritisation of pathogenicity bioassays. Starting with more than 79 unique fungal morphotypes isolated from diseased Sporobolus grasses in Queensland, Australia, we employed multi-locus phylogenetic analyses to classify these isolates into 54 fungal taxa. These taxa belong to 22 Ascomycete families (12 orders), of which the majority fall within the Pleosporales (>24 taxa in 7 families). In the next phase of the study, the putative species identities of these taxa will allow us to prioritise those which are likely to be pathogenic based on existing literature and their known ecological roles. This study represents the first step in a systematic, high-throughput approach to finding potential plant pathogenic biological control agents.

Seed Mucilage Promotes Dispersal of Plantago asiatica Seeds by Facilitating Attachment to Shoes

Understanding the mechanisms underlying seed dispersal is a fundamental issue in plant ecology and vegetation management. Several species demonstrate myxospermy, a phenomenon where the seeds form mucilage after absorbing water. Mucilage is thought to act as a glue, enabling seeds to attach to the external surfaces of dispersing agents. However, there have been no quantitative investigations of the efficacy of this function of seed mucilage. We performed a trampling and walking experiment to investigate the seed dispersal of a perennial herb, Asian plantain (Plantago asiatica L.), which forms polysaccharide mucilage upon hydration. Our experiment showed that: (1) after trampling, more seeds of P. asiatica attached to shoes in wet conditions (after rainfall), in which seed mucilage was created, than in dry conditions (no rainfall); and (2) after walking for 1000 m, more seeds remained attached to shoes in wet conditions than in dry conditions. Our results indicate that mucilage promotes the adherence of seeds to the surface of vectors. We therefore provide the first empirical evidence that seed mucilage facilitates epizoochory and human-mediated dispersal.

Laundry washing increases dispersal efficiency of cloth-dispersed propagules

Due to increased human mobility, cloth-dispersed propagules can be transported over long distances, which would not have been bridged otherwise. We studied a potentially important component of human-mediated seed dispersal by assessing the effects of laundry washing on the dispersed propagules. We studied the germination of 18 species, which have morphological adaptations for epizoochory and are commonly dispersed by people. We tested six treatments (washing with water, soap nut or detergent, at 30 °C or 60 °C) compared to an untreated control. Washing intensity was the most significant factor affecting germination. Washing at 30 °C was neutral for 14 species, suppressed one species and supported three species. Washing at 60 °C decreased seedling numbers of half of the studied species. The intensive washing treatments at 60 °C significantly decreased the synchrony of germination. We showed that people are not purely transporting propagules from one location to another, but via the laundry cycle, we can also influence the fate of the transported propagules by affecting germination potential, seedling fitness and germination dynamics. These results have new implications for understanding the early stages of biological invasions and call for improved biosecurity measures in nature reserves subjected to a growing pressure of tourism.

Ecosystem functioning in urban grasslands: The role of biodiversity, plant invasions and urbanization

Urbanization is driving the transformation of natural and rural ecosystems worldwide by affecting both the abiotic environment and the biota. This raises the question whether urban ecosystems are able to provide services in a comparable way to their non-urban counterparts. In urban grasslands, the effects of urbanization-driven ecological novelty and the role of plant diversity in modulating ecosystem functioning have received little attention. In this study, we assessed the influence of biodiversity, abiotic and biotic novelty on ecosystem functioning based on in situ measurements in non-manipulated grasslands along an urbanization gradient in Berlin (Germany). We focused on plant aboveground biomass (AGB), intrinsic water-use efficiency (iWUE) and 15N enrichment factor (Δδ15N) as proxies for biomass production, water and N cycling, respectively, within grassland communities, and tested how they change with plant biogeographic status (native vs alien), functional group and species identity. Approximately one third of the forb species were alien to Berlin and they were responsible for 13.1% of community AGB. Community AGB was positively correlated with plant-species richness. In contrast, iWUE and Δδ15N were mostly determined by light availability (depicted by sky view factor) and urban parameters like the percentage of impervious surface or human population density. We found that abiotic novelty potentially favors aliens in Berlin, mainly by enhancing their dispersal and fitness under drought. Mainly urban parameters indicating abiotic novelty were significantly correlated to both alien and native Δδ15N, but to AGB and iWUE of alien plants only, pointing to a stronger impact of abiotic novelty on N cycling compared to C and water cycling. At the species level, sky view factor appeared to be the prevailing driver of photosynthetic performance and resource-use efficiency. Although we identified a significant impact of abiotic novelty on AGB, iWUE and Δδ15N at different levels, the relationship between species richness and community AGB found in the urban grasslands studied in Berlin was comparable to that described in non-urban experimental grasslands in Europe. Hence, our results indicate that conserving and enhancing biodiversity in urban ecosystems is essential to preserve ecosystem services related to AGB production. For ensuring the provision of ecosystem services associated to water and N use, however, changes in urban abiotic parameters seem necessary.

Weed hygiene practices in rural industries and public land management: Variable knowledge, patchy implementation, inconsistent coordination

Weed management science and practice largely focuses on eradicating, containing and reducing existing weed populations; the focus is on plants in situ. More recently, the redefinition of biosecurity to include weeds has seen greater attention paid to preventing the introduction of weeds to previously uninfested areas within countries. Thus weed hygiene has come to the fore, with a growing number of publications recommending a diverse range of practices to minimise the spread of weeds across farm, regional and state boundaries. Yet little is known about the uptake of weed hygiene practices. The aim of this paper is to evaluate the extent to which best practice weed hygiene is being implemented on, across and along private and public lands. Telephone interviews were conducted with 54 private and public land managers, weed contractors, and agricultural transport operators in New South Wales, Australia. Vehicle hygiene was commonly undertaken across all stakeholder groups when it was consistent with other goals, requirements or norms. Other practices, such as sequencing harvesting from least to most weedy paddocks or including weed hygiene clauses in contracts were often known, but rarely practiced because of the onerous labour and financial costs or concerns about social etiquette. Individual commitment to weed hygiene efforts were also undermined by intra and inter-organisational coordination challenges. Public debate and assessment are needed on the benefits and costs to society of weed hygiene compared to in situ weed control to determine where best to invest limited time and resources.

Pilot Testing of a Sampling Methodology for Assessing Seed Attachment Propensity and Transport Rate in a Soil Matrix Carried on Boot Soles and Bike Tires

Land managers of natural areas are under pressure to balance demands for increased recreation access with protection of the natural resource. Unintended dispersal of seeds by visitors to natural areas has high potential for weedy plant invasions, with initial seed attachment an important step in the dispersal process. Although walking and mountain biking are popular nature-based recreation activities, there are few studies quantifying propensity for seed attachment and transport rate on boot soles and none for bike tires. Attachment and transport rate can potentially be affected by a wide range of factors for which field testing can be time-consuming and expensive. We pilot tested a sampling methodology for measuring seed attachment and transport rate in a soil matrix carried on boot soles and bike tires traversing a known quantity and density of a seed analog (beads) over different distances and soil conditions. We found % attachment rate on boot soles was much lower overall than previously reported, but that boot soles had a higher propensity for seed attachment than bike tires in almost all conditions. We believe our methodology offers a cost-effective option for researchers seeking to manipulate and test effects of different influencing factors on these two dispersal vectors.