Effect of Invasive Aquatic Plants (Azolla a., Myriophyllum a. and Cyperus a.) Biochar Amendment on Maize Growth: An Assessment

The management of invasive aquatic plants (IAPs), which is primarily accomplished through manual grubbing, incurs significant costs for populations, especially since the operations must be renewed on a regular basis. Converting IAPs into biochar for use as soil amendment will help offset the costs of this mechanical control strategy, while also improving carbon sequestration, soil fertility and crop yields. The objective of this study is to examine the effects of using IAPs biochar amendment on the quality of acidic soils and subsequently maize growth. Ten treatment groups including nine treatments and one control were established with four replicates each on freshly sown maize soils. Treatments options include applying IAP biochar (group 1), different combinations of IAP biochar and poultry manure (group 2), and mineral fertilizer (group 3). After 37 days, the average height of maize plants in the control group is 68.83±7.91cm, compared to 69.82 ± 7.34 cm (group1), 64.44 ± 7.82cm (group 2) and 69.08 ± 9.51cm (group 3). Multivariate analyses suggest that the IAPs biochar have significantly higher potential to improve plant growth parameters than either poultry manure or synthetic fertilizer. Based on the foregoing, the use of IAPs biochar amendment should be promoted among smallholder farmers because it is environmentally friendly, easy to produce, has a lower operational cost than other fertilizers, and has been shown to improve the acidic and impoverished dryland soils prevalent in Burkina Faso.

Invasive aquatic plants and the aquarium and ornamental pond industries

The purpose of the research was to clarify the common traits of a successful aquatic invasive plant. The biological traits of aquatic plants sold by aquarium and ornamental pond stores in the Greater Toronto Area, Ontario were analysed using logistic regression analyses (LRM). The multinomial LRM successfully predicts group identity 63% of the time, clearly differentiating native invasive and native non invasive from alien invasive (SI), but not ailen non invasive (ANI) from AI. In contrast, the binomial LRM effectively discriminates ANI from AI taxa 77% of the time. The variable that best discriminated between AI and ANI are type of propagation strategies, number of propagation strategies used, number of dispersal mechanisms used, minimum temperature, and sales volume of aquatic plants as a proxy for introduction. Recognizing the common traits of successful invaders allows for the identification of ANI taxa that have the potential to become invaders, prior to introduction, thus preventing future invasions.

Invasive aquatic plants and the aquarium and ornamental pond industries

The purpose of the research was to clarify the common traits of a successful aquatic invasive plant. The biological traits of aquatic plants sold by aquarium and ornamental pond stores in the Greater Toronto Area, Ontario were analysed using logistic regression analyses (LRM). The multinomial LRM successfully predicts group identity 63% of the time, clearly differentiating native invasive and native non invasive from alien invasive (SI), but not ailen non invasive (ANI) from AI. In contrast, the binomial LRM effectively discriminates ANI from AI taxa 77% of the time. The variable that best discriminated between AI and ANI are type of propagation strategies, number of propagation strategies used, number of dispersal mechanisms used, minimum temperature, and sales volume of aquatic plants as a proxy for introduction. Recognizing the common traits of successful invaders allows for the identification of ANI taxa that have the potential to become invaders, prior to introduction, thus preventing future invasions.

Embracing the Allelopathic Potential of Invasive Aquatic Plants to Manipulate Freshwater Ecosystems

Freshwater ecosystems provide essential resources and vital ecosystem services. These ecosystems exist in a delicate state of balance and are under increasing anthropogenic and climatic pressures. One of the major anthropogenic threats to freshwater ecosystems is eutrophication that often leads to algal blooms, some of which may be extremely harmful. Current chemical and physical interventions to prevent algal blooms can be expensive, ephemeral and disruptive to other aspects of the ecosystem. Therefore, there is interest in utilising biological methods of control. This study aimed to assess the viability of allelopathic repression of nuisance algae species by invasive aquatic plants. The allelopathic effect of Hydrocotyle ranunculoides (Floating Pennywort) and Crassula helmsii (Swamp Stonecrop) were tested in both whole plant and crushed plant states for their ability to affect the average population growth of monocultures and co-cultures of the green algae Chlorella vulgaris and the cyanobacterium Synechocystis sp. PCC6803. Methanol extracts from these species have been identified in the literature to have high allelopathic potential. The key findings of this study are that, for Chlorella: whole H. ranunculoides and crushed C. helmsii had a negative effect on the average population growth; whole H. ranunculoides had a greater negative effect than crushed H. ranunculoides; and crushed C. helmsii had a more negative effect than crushed H. ranunculoides. For Synechocystis: crushed C. helmsii had a greater negative effect on the average population growth than crushed H. ranunculoides; and the presence of Chlorella in co-culture experiments had a universally positive effect on its average population growth. The species-specific nature of these allelopathic interactions suggests that the use of allelopathy for algal bloom control may have to be assessed on a case-by-case basis and the use of combination treatments should be assessed. Moreover, the effects exerted by allelochemicals in open water systems is likely to be direct, indirect and context specific. Although this study explores the possibility of embracing the allelopathic potential of invasive aquatic plants, we do not encourage novel introductions of invasive species into open freshwater systems. However, potential allelopathic effects could be leveraged in already invaded systems, or in closed systems within an invaded range.

Performance and Feasibility of Drone-Mounted Imaging Spectroscopy for Invasive Aquatic Vegetation Detection

Invasive plants are non-native species that can spread rapidly, leading to detrimental economic, ecological, or environmental impact. In aquatic systems such as the Sacramento-San Joaquin River Delta in California, USA, management agencies use manned aerial vehicles (MAV) imaging spectroscopy missions to map and track annual changes in invasive aquatic plants. Advances in unmanned aerial vehicles (UAV) and sensor miniaturization are enabling higher spatial resolution species mapping, which is promising for early detection of invasions before they spread over larger areas. This study compared maps made from UAV-based imaging spectroscopy with the manned airborne imaging spectroscopy-derived maps that are currently produced for monitoring invasive aquatic plants in the Sacramento-San Joaquin Delta. Concurrent imagery was collected using the MAV mounted HyMap sensor and the UAV mounted Nano-Hyperspec at a wetland study site and classification maps generated using random forest models were compared. Classification accuracies were comparable between the Nano- and HyMap-derived maps, with the Nano-derived map having a slightly higher overall accuracy. Additionally, the higher resolution of the Nano imagery allowed detection of patches of water hyacinth present in the study site that the HyMap could not. However, it would not be feasible to operate the Nano as a replacement to HyMap at scale despite its improved detection capabilities due to the high costs associated with overcoming area coverage limitations. Overall, UAV-based imaging spectroscopy provides comparable or improved capability, and we suggest it could be used to supplement existing monitoring programs by focusing on target areas of high ecologic or economic priority.

Distribution of Five Aquatic Plants Native to South America and Invasive Elsewhere under Current Climate

Biological invasions and climate pose two of the most important challenges facing global biodiversity. Certainly, climate change may intensify the impacts of invasion by allowing invasive plants to increase in abundance and further expand their ranges. For example, most aquatic alien plants in temperate climate are of tropical and subtropical origins and the northern limits of their ranges are generally determined by minimum winter temperatures, and they will probably expand their distributions northwards if climate warms. The distribution of five invasive aquatic plants in freshwater systems across continents were investigated. Their global distributions in the current climate were modeled using a recently developed ensemble species distribution model approach, specifically designed to account for dispersal constraints on the distributions of range-expanding species. It was found that the species appear capable of substantial range expansion, and that low winter temperature is the strongest factor limiting their invasion. These findings can be used to identify areas at risk of recently introduction of neophytes, and develop future monitoring programs for aquatic ecosystems, prioritizing control efforts, which enables the effective use of ecological niche models to forecast aquatic invasion in other geographic regions.

Identification of resistant clones of Eurasian (Myriophyllum spicatum) and hybrid (Myriophyllum spicatum × Myriophyllum sibiricum) watermilfoil to an operational rate of fluridone

Genetic assays to identify herbicide-resistant plants are a promising tool to reduce herbicide failures. However, the genetic basis of herbicide resistance is frequently unknown. In clonal weed species, DNA fingerprinting could be a useful tool to identify known resistant versus susceptible genets (clones) that occur in multiple locations, without an immediate need for understanding the genetic mutation(s) conferring resistance. Eurasian watermilfoil (Myriophyllum spicatum L.) and hybrids with native northern watermilfoil (Myriophyllum spicatum × Myriophyllum sibiricum Kom.) are mostly clonal invasive aquatic plants, and the same clones can be found in multiple waterbodies. Previously, a clone was confirmed as resistant to the commonly used herbicide fluridone, and a recent genetic survey in Michigan identified this genotype (MG-237) in at least seven other lakes. We hypothesized that MG-237 collected from different lakes would also exhibit fluridone resistance. However, MG-237 may have accumulated resistance mutations at different times during its spread across Michigan, resulting in fluridone-resistant and fluridone-susceptible MG-237 clones distributed in different lakes. We used a herbicide assay to test the response of several accessions, including MG-237 accessions from multiple lakes, to the Michigan operational rate of 6 µg L−1 fluridone. We found that all accessions of MG-237 exhibited resistance to 6 µg L−1 fluridone. A second genotype (MG-377) was also resistant to 6 µg L−1 fluridone. The rest of the accessions were found to be significantly injured by 6 µg L−1 fluridone. Our results suggest that 6 µg L−1 fluridone would not effectively control waterbodies dominated by MG-237 or MG-377, whereas waterbodies dominated by the other genotypes in our study would likely be controlled. Although more studies are needed to identify the variation in sensitivity of the accessions tested here and the genetic basis of fluridone resistance in Myriophyllum, our results suggest that multilocus genotype data may be an effective tool to identify and track herbicide-resistant genotypes of Myriophyllum in the short term.