Relationship between Forest Ecophysiology and Environment

Ecophysiological mechanisms underlie plant responses to environmental conditions and the influence these responses have on ecological patterns and processes. In this Special Issue, with a particular interest in the interactions between climate change, environmental disturbance, and functional ecology, experimental observations are described at a range of spatial scales. A modeling framework is used in an effort to relate mechanistic responses to ecosystem functions and services, and link forest ecophysiology and environmental indicators. This Special Issue collects important advances in studying and monitoring plant–environment interactions, covering biogeographic gradients from Mediterranean woodlands to boreal forests and from Alpine mountains to tropical environments

Determining the context and scale at which functional traits increase Nicotiana attenuata yields

At least 10,000 years ago, humans began domesticating crop plants into consistent, high-yielding food sources. Plants continue to provide 90% of human food energy intake worldwide. However, as human populations increase and arable land becomes scarce or unproductive due to climate instability, plant food sources may no longer be able to sustain human nutritional requirements. Plant populations must become more productive. This dissertation uses an ecological model plant, Nicotiana attenuata, to evaluate the contexts and scales at which plant populations can increase their productivity. I explore the current uses and future potentials of three functional traits that can be selected for, or genetically modified, in crop cultivars to improve agricultural yields. First, I test the efficacy of current agricultural pest-resistance technology in increasing yield. The pest-resistance technology (Cry1Ac expression), conferred through genetic modification to N. attenuata, did not increase yield in comparison to endogenously defended, or even undefended N. attenuata lines. Due to the scarcity of Cry1Ac-targeted insects in this field season, plants with more flexible use of their direct defenses were able to be more productive, demonstrating the benefit of naturally evolved defenses in the face of yearly-inconsistent pests. Resource-use traits such as plant water-use or association with arbuscular mycorrhizal fungal (AM) networks that facilitate nutrient access are as important to agricultural productivity as pest-resistance. Current screenings for water-use traits among agricultural varieties are insufficient: they do not account for varying rates of soil water consumption or plant development in applying drought treatments, and therefore, do not lead to reproducible results in the field. We use variance decomposition to quantify the extent to which these factors, when left uncontrolled, can significantly change observed results. I then apply the ecologically established biodiversity-productivity phenomenon to attempt to increase population yields by varying the percentage of plants with a low water-use efficiency trait among control plants in N. attenuata field populations. Low percentages of this trait caused overyielding. Using both novel and developed methodologies, I advance the understanding of the mechanisms behind this effect by identifying one of its genetic bases, and narrowing the spatial scale and plant tissue at which it occurs. Finally, we develop a method for screening agricultural cultivars for association with AM fungal networks by using a high-throughput leaf molecular marker rather than traditional microscopy methods, which are laborious and destructive. This work emphasizes the benefits of methodological development, which can both improve screenings for agriculturally-relevant functional traits and allow for application of ecologically-informed alternatives to increase population yield (e.g. intraspecific diversity).Bereits vor mindestens 10 000 Jahren begannen Menschen Pflanzen zu domestizieren und gewannen damit einheitliche und ertragreiche Nahrungsquellen. Auch heute nehmen Menschen 90% ihrer Nahrungsenergie über Pflanzen auf. Allerdings könnten in Zukunft Pflanzen nicht ausreichen, um die menschlichen Nahrungsbedürfnisse zu decken. Die Weltbevölkerung wächst und Klimainstabilität führt zu schrumpfenden Agrarflächen oder sinkenden Erträgen. Pflanzen müssen dementsprechend ertragreicher werden. In dieser Dissertation wird die Modellpflanze Nicotiana attenuata verwendet, um die Zusammenhänge und Ausmaße zu erforschen, in denen Pflanzenpopulationen ihre Leistungsfähigkeit steigern können. Ich untersuche die derzeitige Anwendung sowie zukünftige Potentiale von drei funktionellen Eigenschaften, die in der Züchtung selektiert oder in Pflanzen genetisch modifiziert werden können, um landwirtschaftliche Erträge zu steigern. Zuerst analysiere ich, wie effizient derzeitige landwirtschaftliche Schädlingsresistenztechnologien die Ausbeute erhöhen. Die Expression des Cry1Ac als Verteidigungssystem, eingebracht in N. attenuata durch genetische Modifikation, führte zu keiner Ertragssteigerung im Vergleich zu Pflanzen mit endogener Verteidigung oder sogar unverteidigten N. attenuata-Linien. Da in der Saison des Feldversuchs nur wenige Insekten vorkamen, gegen die das Cry1Ac-System gerichtet ist, reagierten Pflanzen mit endogener Verteidigung plastischer und damit produktiver auf ganzjährlich variierende Herbivorgemeinschaften. Genauso wichtig wie Schädlingsresistenz sind die Ressourcennutzung sowie die Assoziation mit arbuskulären Mykorrhizapilzen (AM-Pilzen), die den Zugang zu Nährstoffen unterstützen. Derzeitige Untersuchungen zu Wassernutzungseigenschaften verschiedener Agrarsorten sind unzureichend: In Versuchen mit Dürrebehandlung werden Unterschiede im Bodenwasserverbrauch oder die Entwicklung der Pflanzen nicht berücksichtigt und führen dementsprechend nicht zu reproduzierbaren Ergebnissen im Feld. Durch Varianzzerlegung quantifizieren wir, in welchem Ausmaß die einzelnen Faktoren, sollten sie unkontrolliert bleiben, die Ergebnisse signifikant verändern können. Mithilfe des ökologisch etablierten Biodiversitäts-Produktivitäts-Phänomens habe ich versucht die Populationserträge zu erhöhen, indem ich die Anteile von Pflanzen mit geringer Wasserverbrauchseffizienz und Kontrollpflanzen variiert habe. Waren solche Pflanzen zu einem geringen Prozentsatz in N. attenuata Feldpopulationen vorhanden, führte dies zu einer Ertragssteigerung. Mittels sowohl neuer als auch etablierter Methoden ist es mir gelungen zum Verständnis der Mechanismen hinter diesem Effekt beizutragen, indem ich eine der zugrundeliegenden genetischen Ursachen identifiziert habe und das räumliche Ausmaß sowie das Pflanzengewebe, in dem dieser Effekt auftritt, eingegrenzt habe. Abschließend entwickelten wir eine Methode, um Kultivare in Agrarpopulationen auf Assoziation mit AM-Pilzen zu untersuchen, bei der im high-throughput-Verfahren ein molekularer Marker im Blatt statt der traditionellen, aufwendigen und schädlichen Mikroskopiemethode verwendet wurde. Diese Arbeit betont die Vorteile von Methodenentwicklung, welche sowohl die Suche nach landwirtschaftlich relevanten Eigenschaften verbessern kann als auch die Anwendung von ökologisch begründeten Alternativen zur Ertragssteigerung ermöglicht (z.B. intraspezifische Diversität)

Interactions between ecosystem carbon, nitrogen and water cycles under global change: Results from field and mesocosm experiments.

N additions increased NEE by enhancing light interception, RUE, and extending growing seasons. Different N application methods (PF versus GF) caused differential seasonal dynamics of LAI, NEE and RUE due to their different N supply doses during different growth periods. N fertilization stimulated evapotranspiration primarily by extending growing season. N fertilization enhanced photosynthesis more than evapotranspiration, causing higher ecosystem WUE. Different fertilization methods changed the seasonal dynamics of WUE due to their differential effects on gross ecosystem photosynthesis.Little is known about how climate warming, land-use change and N fertilization/deposition affect ecosystem carbon (C), nitrogen (N) and water cycles. By reducing plant C substrate input via cutting aboveground biomass and shading, I investigated how plant C supply affects soil N dynamics in a tallgrass prairie. By incubating litter bags in the field, I studied the effects of warming and clipping on litter decomposition and N dynamics of 3 litter species. By measuring whole-ecosystem CO2 and water fluxes of a model grassland ecosystem, I investigated whether N fertilization (simulated by pulse N fertilization) and deposition (mimicked by gradual N fertilization) increase NEE, radiation-use efficiency (RUE), ET, and water-use efficiency (WUE).Warming and clipping together significantly altered the mass remaining percentage of S. scoparium shoot litter, with the treatment effects being mainly caused by clipping. Warming and clipping did not affect the net nitrogen (N) immobilization/release of the 3 litter types. However, the decay constant k and N remaining percentages differed among the 3 litter types due to their different initial litter quality. Warming reduced whereas clipping increased the in situ litter quality, suggesting a potential impact on the long-term ecosystem C and N cycles.Biomass removal (BR) and shading (S) increased soil inorganic N, likely due to the severed plant N uptake and reduced microbial N immobilization. Shading increased net N mineralization and nitrification probably by reducing microbial N immobilization. Soil respiration, together with soil microclimate, accounted for 27--38% additional variations in NH4 +-N, net N mineralization and nitrification rates than soil microclimate alone, suggesting an important role of plant C supply in regulating NH 4+-N, net N mineralization and nitrification rates

Plant Responses to Stress and Environmental Stimulus

Plants respond to diverse environmental stimuli such as light, nutrients, temperature, and oxygen, which shape their growth and fate. When these stimuli are suboptimal for adequate plant growth, they cause stress. This book is a collection of research articles providing evidence about plant responses to stresses and environmental stimuli, as well as new methodologies for plant phenotyping

A study of molecular responses to abiotic and biotic stresses in Arachis

Em seu ambiente natural, as plantas são expostas a uma série de estresses abióticos e bióticos. Entre eles, a seca é um grande obstáculo à agricultura e, em associação com patógenos e pragas, pode causar prejuízos de até US$38 bilhões de 2005 a 2015, e comprometer a segurança alimentar. Com as mudanças climáticas e aquecimento global, esse cenário tende a agravar-se, aumentando a ocorrência de secas, a amplitude da gama de hospedeiros e virulência de agentes patogênicos. O estudo da resposta molecular à estresses individuais em diferentes plantas assim como a resposta a estresses combinados, constitui um grande avanço, para a compreensão de possíveis trade-offs entre tolerância e suscetibilidade à estresses abióticos e bióticos, quanto o desenvolvimento de cultivares mais resistentes. Visando um melhor entendimento da resposta moleculares de plantas, o presente estudo empregou diferentes ferramentas, como genômica comparativa e transcritomas. O uso dessas ferramentas visou a identificação de genes comumente regulados por diferentes estresses. No capítulo I, o transcritoma de quatro diferentes espécies de plantas (Arachis stenosperma, Coffea arabica, Glycine max e Oryza glaberrima) inoculadas com nematoides das galhas (Meloidogyne spp.) foram analisados e combinados com dados de genômica comparativa gerados a partir do proteoma de 22 espécies de plantas. No total, 17 famílias de proteínas ortólogas são comumente reguladas pela inoculação de nematoides das galhas, representando ao todo 364 proteínas. A anotação funcional desses ortogrupos indicou que a maioria dessas proteínas está associada à parede celular, receptores quinases e a estresse, e tendo uma única família de fatores de transcrição representada, ERF a qual desempenha um papel fundamental na resposta de defesa da planta. No Capítulo II, a análise do transcritoma de Arachis stenosperma submetido à combinação de dois estresses, seca e inoculação por nematoides das galhas, foi realizada. Diversos genes de resistência a estresses combinados foram identificados sendo que uma resposta transcricional distinta foi observada quando da imposição de estresses combinados, quando comparada a estresses individuais. Apenas 14 genes foram encontrados em comum entre a seca, inoculação por nematoides e estresses combinados e 209 genes foram exclusivamente regulados no tratamento combinado. Este resultado demonstra que uma reprogramação molecular única é empregada pela planta sob múltiplos estresses, o que não pode ser previsto pela análise de cada estresse aplicado individualmente. A análise de genômica comparativa e a análise de estresse combinado realizadas no presente estudo permitiram a identificação de famílias de genes essenciais à resistência / tolerância de plantas. A família das expansinas, a qual foi modulada durante a seca, infecção por RKN e UV, revelando uma importante família de genes em resposta a múltiplos estresses e em espécies distintas; e um gene de desidrina, cuja superexpressão em Arabidopsis revelou um importante trade-off entre estresses abióticos e bióticos.In their natural environment plants are exposed to a range of abiotic and biotic stresses. Among them, drought is a major constraint to agriculture and, in association with pathogen and pests, can cause losses of up to$38 billion from 2005 to 2015 and compromise food security. With the advent of climate change and global warming, this scenario tends to become worse, with an increase in drought occurrence and pathogen`s host range and virulence. Breeding programs are doing great efforts to find solutions to improve multiple stress resistance in plants, however, the trade-offs between abiotic stress tolerance and biotic stress susceptibility have hardly been investigated. Here, a comparative genomics study was conducted, which has the potential to identify putative evolutionarily conserved genes involved in universal defense mechanisms, to identify genes regulated in common by Meloidogyne spp infection in four plant species (Arachis stenosperma, Coffea arabica, Glycine max, and Oryza glaberrima). In total, 17 orthologs protein families which respond to the inoculation of RKN in the four species, comprising a total of 364 proteins. The functional annotation of these orthogroups indicated that the majority of these genes are associated with the cell wall, receptor kinases and stress related, with the transcription factor ERF playing a pivotal role in these defense responses. A number of multiple-stress resistant genes was identified by analyzing the transcriptome of a resistant wild Arachis species, A. stenosperma, under the combination of RKN and drought imposition. An overall distinct transcriptional response was observed for the combinatory stress imposition when compared to each individual stress, with only 14 genes found in common among drought, nematode infection and combined stresses and 209 exclusively regulated genes within the combined treatment. This result demonstrates that a unique molecular reprogramming is employed by the plant under multiple stresses, which cannot be predicted by the analysis of each individual stress alone. The comparative genomics and the cross-stress analysis conducted in this study enabled the identification of genes families which are essential to plant resistance/tolerance. The gene family of the expansins which was modulated during drought, RKN infection and UV, disclosing an important gene family in response to multiple stresses and across species; and a dehydrin gene, 13 which overexpression in Arabidopsis revealed an important trade-off between abiotic and biotic stresses

Plant Proteomic Research

Plants, being sessile in nature, are constantly exposed to environmental challenges resulting in substantial yield loss. To cope with harsh environments, plants have developed a wide range of adaptation strategies involving morpho-anatomical, physiological, and biochemical traits. In recent years, there has been phenomenal progress in the understanding of plant responses to environmental cues at the protein level. This progress has been fueled by the advancement in mass spectrometry techniques, complemented with genome-sequence data and modern bioinformatics analysis with improved sample preparation and fractionation strategies. As proteins ultimately regulate cellular functions, it is perhaps of greater importance to understand the changes that occur at the protein-abundance level, rather than the modulation of mRNA expression. This Special Issue on "Plant Proteomic Research" brings together a selection of insightful papers that address some of these issues related to applications of proteomic techniques in elucidating master regulator proteins and the pathways associated with plant development and stress responses. This Issue includes four reviews and 13 original articles primarily on environmental proteomic studies

Carbon and Water Dynamics in Modern and Ancient Plants and Soils

During modern times of unprecedented climate change, historical and geological records of past climate allow us to understand and project ancient patterns in the carbon and water cycle. Plants and soils are excellent records for climate because of the direct interaction between the terrestrial biosphere and the atmosphere and their preservation potential. Organic carbon isotope records in plants and soils have been linked to several environmental, evolutionary, and edaphic drivers, in addition to being used to measure ecosystem stress. Most of the works use organic carbon isotope values in ancient plant fossils with unconstrained and uncertain environments or in modern plant growth experiments with highly controlled environments that are not directly comparable to the natural world. The period of Industrialization provides a natural experiment with measurable, but not lab-controlled climate change, ideal for investigating the relationship between climate variability (particularly the carbon and water cycles) and C isotope values. This dissertation includes several high-resolution spatiotemporal studies of several plant species through the pre-Industrial era. In Chapter II, leaf carbon isotope values from a single Great Lakes region species are compared to environmental variables involved in the water and carbon cycles (e.g. atmospheric CO2 concentration and isotopic signature, temperature, precipitation, etc.) over the span of 200 years. Leaf isotope biogeochemistry of this species is unresponsive to every environmental variable except the isotopic composition of atmospheric CO2. Chapter III expands on results from previous experiments, and investigates the relationship between the carbon dioxide of the atmosphere and plant carbon isotope geochemistry with eight Northern Hemisphere focal species. These specimens are complemented by C3 plant isotope analyses of aggregated from literature. Results from this work demonstrate that plants do not change biochemically as expected in response to CO2 rise. In Chapter IV, findings from previous chapters are re-examined from the context of aboveground carbon integrator: soils. The role of weathering in the development of soils provides incentive for investigating soils as potential water cycle records. As in Chapter III, this study includes soils collected across a climosequence, supplemented by aggregated carbon isotope values from prior publications. This work also tests the relationship between soil carbon isotopes and precipitation in ancient soils (paleosols). In both modern and ancient studies, carbon isotope values of soil correlate to precipitation. Chapter V integrates the results and conclusions from early dissertation chapters with pre-established geochemical and physiognomic proxies to provide a comprehensive analysis of early Eocene hothouse sediments. Depositional basins from the Eocene are well-studied and contain opportunities for multi-proxy-based environmental reconstruction. Using organic and inorganic tools to constrain provenance, parent material, and other features of the depositional environment, an early Eocene fluvial-lacustrine subtropical forest deposit shows constant sedimentological and hydrological inputs and consistent climate during a time of expected cooling and tectonic activity. In summary, this dissertation contains case studies relating soils and plants to the carbon and water cycle in modern, historical and deep time and demonstrates the recording power of the terrestrial biosphere. These findings can be used to contextualize and guide applications of organic isotope biogeochemistry in paleoclimate reconstructions. Related to modern climate problems, results from this dissertation provide integral information about plants and soils as carbon and water distributors and mitigators of anthropogenic climate change.PHDEarth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/166152/1/restein_1.pd

Impacts of climate change on the boreal forest ecosystem. Scientific Opinion of the Panel on Alien Organisms and Trade in Endangered species (CITES) of the Norwegian Scientific Committee for Food and Environment

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