title: Charophyte Response to Herbicide and Mycoherbicide Applications

authors: Kelly, Chrystal Leigh

subjects: New Zealand

abstract: This thesis describes an investigation into the impacts on charophytes of four selected aquatic herbicide and a mycoherbicide products currently used or under development in New Zealand for alien invasive aquatic plant management. Of particular interest was the charophyte response with respect to oospore germination, germling susceptibility and species response. In New Zealand, charophytes are native submerged aquatic plants which are recognized as beneficial components of lake ecosystems. They form dense meadows on the lake sediment and are rapid colonisers as they are the first plant to recolonise a lake after a disturbance event. Charophytes produce oospores (seeds) which can remain dormant in seed banks until suitable germination conditions are met. New Zealand lake sediments contain a seed bank which is dominated by charophyte oospores. Alien invasive plants severely impact charophytes by rapidly forming tall, dense monospecific stands which can displace and completely replace the native vegetation. Chemical weed control in New Zealand is limited to two aquatic herbicides, diquat and endothall, which are currently registered for use on submerged aquatic weeds in lakes and waterways. Fluridone, which is widely used in the USA, is not currently registered for commercial use in New Zealand but has been used in several New Zealand studies. More recently, the development of a mycoherbicide, an inundative biological control, using a formulated naturally occurring aquatic fungus has been trialed in the USA and New Zealand. The effects of these four products on charophytes were investigated in this study. Chelated copper was included as a control, as it is known to control algae, including charophytes overseas. For this research, lake sediment was collected from three New Zealand lakes and combined to give one mixed seed bank material of known oospore density and composition. There were two types of charophyte experiments; germination experiments and germling experiments. Two germination experiments examined different scenarios for herbicide treatments under controlled temperature and light conditions. Oospores were either retained in sediment or directly exposed to treatment. Two germling experiments examined germling susceptibility to herbicide treatments under outdoor conditions as well as controlled temperature and light conditions. The second germling experiment included a known charophyte control treatment (chelated copper compound) and a known target invasive plant (Lagarosiphon major) control treatment for the herbicides. Herbicide treatment doses started at the maximum label rate and decreased in concentration across a dilution series. Results from this research indicate that oospore germination was not negatively impacted by any of the herbicide treatments or doses although some species-specific sensitivity was evident. However, further research into species sensitivity is required to ascertain if the sensitivity was due to herbicidal effects or a combination of naturally occurring factors and what the implications of sensitivity are for weed management. For the germling experiments no negative effects were observed for the duration of the study. These results have positive implications for field application of herbicides, indicating that the younger charophyte growth stages (oospores and germlings) were unaffected by the type of herbicide used at any potential field application rate.

text: Charophyte Response to Herbicide and Mycoherbicide Applications This thesis describes an investigation into the impacts on charophytes of four selected aquatic herbicide and a mycoherbicide products currently used or under development in New Zealand for alien invasive aquatic plant management. Of particular interest was the charophyte response with respect to oospore germination, germling susceptibility and species response. In New Zealand, charophytes are native submerged aquatic plants which are recognized as beneficial components of lake ecosystems. They form dense meadows on the lake sediment and are rapid colonisers as they are the first plant to recolonise a lake after a disturbance event. Charophytes produce oospores (seeds) which can remain dormant in seed banks until suitable germination conditions are met. New Zealand lake sediments contain a seed bank which is dominated by charophyte oospores. Alien invasive plants severely impact charophytes by rapidly forming tall, dense monospecific stands which can displace and completely replace the native vegetation. Chemical weed control in New Zealand is limited to two aquatic herbicides, diquat and endothall, which are currently registered for use on submerged aquatic weeds in lakes and waterways. Fluridone, which is widely used in the USA, is not currently registered for commercial use in New Zealand but has been used in several New Zealand studies. More recently, the development of a mycoherbicide, an inundative biological control, using a formulated naturally occurring aquatic fungus has been trialed in the USA and New Zealand. The effects of these four products on charophytes were investigated in this study. Chelated copper was included as a control, as it is known to control algae, including charophytes overseas. For this research, lake sediment was collected from three New Zealand lakes and combined to give one mixed seed bank material of known oospore density and composition. There were two types of charophyte experiments; germination experiments and germling experiments. Two germination experiments examined different scenarios for herbicide treatments under controlled temperature and light conditions. Oospores were either retained in sediment or directly exposed to treatment. Two germling experiments examined germling susceptibility to herbicide treatments under outdoor conditions as well as controlled temperature and light conditions. The second germling experiment included a known charophyte control treatment (chelated copper compound) and a known target invasive plant (Lagarosiphon major) control treatment for the herbicides. Herbicide treatment doses started at the maximum label rate and decreased in concentration across a dilution series. Results from this research indicate that oospore germination was not negatively impacted by any of the herbicide treatments or doses although some species-specific sensitivity was evident. However, further research into species sensitivity is required to ascertain if the sensitivity was due to herbicidal effects or a combination of naturally occurring factors and what the implications of sensitivity are for weed management. For the germling experiments no negative effects were observed for the duration of the study. These results have positive implications for field application of herbicides, indicating that the younger charophyte growth stages (oospores and germlings) were unaffected by the type of herbicide used at any potential field application rate.

year: 2011

title: Report on the INTAV international tephra conference “Crossing New Frontiers: Tephra Hunt in Transylvania”, 24 June-1 July, 2018, Moieciu de Sus, Romania

authors: Lowe, David J.

abstract: The International Focus Group on Tephrochronology and Volcanism (INTAV) held a tephra conference, “Crossing New Frontiers: Tephra Hunt in Transylvania”, at Moieciu de Sus, near Braşov in the southern Carpathian Mountains of Transylvania, Romania, from 24 June to 1 July, 2018. The conference encompassed many aspects of INTAV’s underpinning EXTRAS project: EXTending tephRAS as a global geoscientific research tool stratigraphically, spatially, analytically, and temporally in the Quaternary.

text: Report on the INTAV international tephra conference “Crossing New Frontiers: Tephra Hunt in Transylvania”, 24 June-1 July, 2018, Moieciu de Sus, Romania The International Focus Group on Tephrochronology and Volcanism (INTAV) held a tephra conference, “Crossing New Frontiers: Tephra Hunt in Transylvania”, at Moieciu de Sus, near Braşov in the southern Carpathian Mountains of Transylvania, Romania, from 24 June to 1 July, 2018. The conference encompassed many aspects of INTAV’s underpinning EXTRAS project: EXTending tephRAS as a global geoscientific research tool stratigraphically, spatially, analytically, and temporally in the Quaternary.

year: 2018

title: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand

authors: Noble, Anya S.

subjects: Science & Technology

abstract: The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

text: A core phyllosphere microbiome exists across distant populations of a tree species indigenous to New Zealand The phyllosphere microbiome is increasingly recognised as an influential component of plant physiology, yet it remains unclear whether stable host-microbe associations generally exist in the phyllosphere. Leptospermum scoparium (mānuka) is a tea tree indigenous to New Zealand, and honey derived from mānuka is widely known to possess unique antimicrobial properties. However, the host physiological traits associated with these antimicrobial properties vary widely, and the specific cause of such variation has eluded scientists despite decades of research. Notably, the mānuka phyllosphere microbiome remains uncharacterised, and its potential role in mediating host physiology has not been considered. Working within the prevailing core microbiome conceptual framework, we hypothesise that the phyllosphere microbiome of mānuka exhibits specific host association patterns congruent with those of a microbial community under host selective pressure (null hypothesis: the mānuka phyllosphere microbiome is recruited stochastically from the surrounding environment). To examine our hypothesis, we characterised the phyllosphere and associated soil microbiomes of five distinct and geographically distant mānuka populations across the North Island of New Zealand. We identified a habitat-specific and relatively abundant core microbiome in the mānuka phyllosphere, which was persistent across all samples. In contrast, non-core phyllosphere microorganisms exhibited significant variation across individual host trees and populations that was strongly driven by environmental and spatial factors. Our results demonstrate the existence of a dominant and ubiquitous core microbiome in the phyllosphere of mānuka, supporting our hypothesis that phyllosphere microorganisms of mānuka exhibit specific host association and potentially mediate physiological traits of this nationally and culturally treasured indigenous plant. In addition, our results illustrate biogeographical patterns in mānuka phyllosphere microbiomes and offer insight into factors contributing to phyllosphere microbiome assembly.

year: 2020