Michigan Technological University

About: Michigan Technological University is a education organization based out in Houghton, Michigan, United States. It is known for research contribution in the topics: Population & Volcano. The organization has 8023 authors who have published 17422 publications receiving 481780 citations. The organization is also known as: MTU & Michigan Tech.

CO2 enrichment and warming of the atmosphere enhance both productivity and mortality of maple tree fine roots

Abstract: Summary • Fine roots are the key link for plant water and nutrient uptake, soil carbon (C) input and soil microbial activity in forest ecosystems, and play a critical role in regulating ecosystem C balance and its response to global change. • Red maple ( Acer rubrum ) and sugar maple ( Acer saccharum ) seedlings were grown for four growing seasons in open-top chambers and exposed to ambient or elevated carbon dioxide concentration [CO 2 ] in combination with ambient or elevated temperature. Fine-root production and mortality were monitored using minirhizotrons, and root biomass was determined from soil cores. • Both elevated [CO 2 ] and temperature significantly enhanced production and mortality of fine roots during spring and summer of 1996. At the end of the experiment in September 1997, fine root biomass was significantly lower in elevated temperature chambers, but there were no effects of elevated [CO 2 ] or the interactions between elevated [CO 2 ] and temperature. • Deciduous trees have dynamic root systems, and their activity can be enhanced by CO 2 enrichment and climatic warming. Static measures of root response, such as soil core data, obscure the dynamic nature, which is critical for understanding the response of forest C cycling to global change.

Dissociation and horizontal transmission of codispersing lichen symbionts in the genus Lepraria (Lecanorales: Stereocaulaceae).

Abstract: Lichenized fungi of the genus Lepraria lack ascomata and conidiomata, and symbionts codisperse by soredia. Here, it is determined whether algal symbionts associated with Lepraria are monophyletic, and whether fungal and algal phylogenies are congruent, both of which are indicative of a long-term, continuous association between symbionts. The internal transcribed spacer (ITS) and part of the actin type I locus were sequenced from algae associated with Lepraria, and the fungal ITS and mitochondrial small subunit (mtSSU) were sequenced from fungal symbionts. Phylogenetic analyses tested for monophyly of algal symbionts and congruence between algal and fungal phylogenies. Algae associated with Lepraria were not monophyletic, and identical algae associated with different Lepraria individuals and species. Algal and fungal phylogenies were not congruent, suggesting a lack of strict codiversification. This study suggests that associations between symbionts are not strictly maintained over evolutionary time. The ability to switch partners may provide benefits similar to genetic recombination, which may have helped this lineage persist.

Atmospheric Co2, Soil‐N Availability, And Allocation Of Biomass And Nitrogen By Populus Tremuloides

Abstract: Our ability to predict whether elevated atmospheric CO2 will alter the cycling of C and N in terrestrial ecosystems requires understanding a complex set of feedback mechanisms initiated by changes in C and N acquisition by plants and the degree to which changes in resource acquisition (C and N) alter plant growth and allocation. To gain further insight into these dynamics, we grew six genotypes of Populus tremuloides Michx. that differ in autumnal senescence (early vs. late) under experimental atmospheric CO2 (35.7 and 70.7 Pa) and soil-N availability (low and high) treatments. Atmospheric CO2 concentrations were manipulated with open-top chambers, and soil-N availability was modified in open-bottom root boxes by mixing different proportions of native A and C horizon soil. Net N mineralization rates averaged 61 ng N·g−1·d−1 in low-N soil and 319 ng N·g−1·d−1 in high-N soil. After 2.5 growing seasons, we harvested above- and belowground plant components in each chamber and determined total biomass, N concentration, N content, and the relative allocation of biomass and N to leaves, stems, and roots. Elevated CO2 increased total plant biomass 16% in low-N soil and 38% in high-N soil, indicating that the growth response of P. tremuloides to elevated CO2 was constrained by soil-N availability. Greater growth under elevated CO2 did not substantially alter the allocation of biomass to above- or belowground plant components. At both levels of soil-N availability, elevated CO2 decreased the N concentration of all plant tissues. Despite declines in tissue N concentration, elevated CO2 significantly increased whole-plant N content in high-N soil (ambient = 137 g N/chamber; elevated = 155 g N/chamber), but it did not influence whole-plant N content in low-N soil (36 g N/chamber). Our results indicate that plants in high-N soil obtained greater amounts of soil N under elevated CO2 by producing a proportionately larger fine-root system that more thoroughly exploited the soil. The significant positive relationship between fine-root biomass and total-plant N content we observed in high-N soil further supports this contention. In low-N soil, elevated CO2 did not increase fine-root biomass or production, and plants under ambient and elevated CO2 obtained equivalent amounts of N from soil. In high-N soil, it appears that greater acquisition of soil N under elevated CO2 fed forward within the plant to increase rates of C acquisition, which further enhanced plant growth response to elevated CO2.

Genomic sweep and potential genetic rescue during limiting environmental conditions in an isolated wolf population

Abstract: Genetic rescue, in which the introduction of one or more unrelated individuals into an inbred population results in the reduction of detrimental genetic effects and an increase in one or more vital rates, is a potentially important management tool for mitigating adverse effects of inbreeding. We used molecular techniques to document the consequences of a male wolf (Canis lupus) that immigrated, on its own, across Lake Superior ice to the small, inbred wolf population in Isle Royale National Park. The immigrant’s fitness so exceeded that of native wolves that within 2.5 generations, he was related to every individual in the population and his ancestry constituted 56 per cent of the population, resulting in a selective sweep of the total genome. In other words, all the male ancestry (50% of the total ancestry) descended from this immigrant, plus 6 per cent owing to the success of some of his inbred offspring. The immigration event occurred in an environment where space was limiting (i.e. packs occupied all available territories) and during a time when environmental conditions had deteriorated (i.e. wolves’ prey declined). These conditions probably explain why the immigration event did not obviously improve the population’s demography (e.g. increased population numbers or growth rate). Our results show that the beneficial effects of gene flow may be substantial and quickly manifest, short-lived under some circumstances, and how the demographic benefits of genetic rescue might be masked by environmental conditions.