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Soil extracellular enzyme activities correspond with abiotic factors more than fungal community composition

Soil extracellular enzymes are the proximal drivers of decomposition. However, the relative influence of climate, soil nutrients and edaphic factors compared to microbial community composition on extracellular enzyme activities (EEA) is poorly resolved. Determining the relative effects of these factors on soil EEA is critical since changes in climate and microbial species composition may have large impacts on decomposition. We measured EEA from five sites during the growing season in March and 17 sites during the dry season in July throughout southern California and simultaneously collected data on climate, soil nutrients, soil edaphic factors and fungal community composition. The concentration of carbon and nitrogen in the soil and soil pH were most related to hydrolytic EEA. Conversely, oxidative EEA was mostly related to mean annual precipitation. Fungal community composition was not correlated with EEA at the species, genus, family or order levels. The hyphal length of fungi was correlated with EEA during the growing season while relative abundance of taxa within fungal phyla, in particular Chytridiomycota, was correlated with the EEA of beta-glucosidase, cellobiohydrolase, acid phosphatase and beta-xylosidase in the dry season. Overall, in the dry season, 35.3� % of the variation in all enzyme activities was accounted for by abiotic variables, while fungal composition accounted for 27.4� %. Because global change is expected to alter precipitation regimes and increase nitrogen deposition in soils, EEA may be affected, with consequences for decomposition

Fidelity of information transmission in local campaigns on water issues

Most issues involving water supply are public issues, and achieving consensus for solution of problems in this area is problematic, therefore a study was designed to assess whether information about water issues is distorted in successive transmissions, thereby inhibiting achievement of consensus. The issue in the study community hinged on expansion of its sewage treatment facility, or losing local industry in order to abate the flow of inadequately treated effluent into a local river. Analysis showed that degree of exposure to information about water pollution, and especially to official information sources, contributed to consensus on the seriousness of the problem, but not to consensus on problem solution. Therefore it seemed unlikely that sheer information loss or other modifications of message content in successive transmissions of information could account for a lack of consensus on problem solution. However, analyzing respondents' basic attitudes as determinants of positions on pollution issues, showed more promising results. Tentative findings indicate that people who view themselves as dependent, and lacking in ability to predict events, are most prone to favor corporate action. It is suggested that information campaigns on public issues should take into account the link between peoples' basic attitudes and issue-specific attitudes.U.S. Department of the InteriorU.S. Geological SurveyOpe

Evolutionary trade-offs among decomposers determine responses to nitrogen enrichment.

Evolutionary trade-offs among ecological traits are one mechanism that could determine the responses of functional groups of decomposers to global changes such as nitrogen (N) enrichment. We hypothesised that bacteria targeting recalcitrant carbon compounds require relatively high levels of N availability to support the construction costs of requisite extracellular and transport enzymes. Indeed, we found that taxa that used more recalcitrant (i.e. larger and cyclic) carbon compounds were more prevalent in ocean waters with higher nitrate concentrations. Compared to recalcitrant carbon users, labile carbon users targeted more organic N compounds, were found in relatively nitrate-poor waters, and were more common in higher latitude soils, which is consistent with the paradigm that N-limitation is stronger at higher latitudes. Altogether, evolutionary trade-offs may limit recalcitrant carbon users to habitats with higher N availability

Tropical Tree Species Effects on Soil pH and Biotic Factors and the Consequences for Macroaggregate Dynamics

Physicochemical and biotic factors influence the binding and dispersivity of soil particles, and thus control soil macroaggregate formation and stability. Although soil pH influences dispersivity, it is usually relatively constant within a site, and thus not considered a driver of aggregation dynamics. However, land-use change that results in shifts in tree-species composition can result in alteration of soil pH, owing to species-specific traits, e.g., support of nitrogen fixation and Al accumulation. In a long-term, randomized complete block experiment in which climate, soil type, and previous land-use history were similar, we evaluated effects of individual native tropical tree species on water-stable macroaggregate size distributions in an Oxisol. We conducted this study at La Selva Biological Station in Costa Rica, in six vegetation types: 25-year-old plantations of four tree species grown in monodominant stands; an unplanted Control; and an adjacent mature forest. Tree species significantly influenced aggregate proportions in smaller size classes (0.25–1.0 mm), which were correlated with fine-root growth and litterfall. Tree species altered soil pH differentially. Across all vegetation types, the proportion of smaller macroaggregates declined significantly as soil pH increased (p ≤ 0.0184). This suggests that alteration of pH influences dispersivity, and thus macroaggregate dynamics, thereby playing a role in soil C, N, and P cycling

Global diversity and distribution of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi form associations with most land plants and can control carbon, nitrogen, and phosphorus cycling between above- and belowground components of ecosystems. Current estimates of AM fungal distributions are mainly inferred from the individual distributions of plant biomes, and climatic factors. However, dispersal limitation, local environmental conditions,and interactions among AM fungal taxa may also determine local diversity and global distributions. We assessed the relative importance of these potential controls by collecting 14,961 DNA sequences from 111 published studies and testing for relationships between AM fungal community composition and geography, environment, and plant biomes. Our results indicated that the global species richness of AM fungi was up to six times higher than previously estimated, largely owing to high beta diversity among sampling sites. Geographic distance, soil temperature and moisture, and plant community type were each significantly related to AM fungal community structure, but explained only a small amount of the observed variance. AM fungal species also tended to be phylogenetically clustered within sites, further suggesting that habitat filtering or dispersal limitation is a driver of AM fungal community assembly. Therefore, predicted shifts in climate and plant species distributions under global change may alter AM fungal communities

POLY (ADP) RIBOSE POLYMERASE INHIBITORS FOR THE TREATMENT OF MALIGNANT PERIPHERAL NERVE SHEATH TUMOR

Malignant peripheral nerve sheath tumor (MPNST) is a rare subtype of soft tissue sarcoma. Surgical excision has remained the standard of care for this highly aggressive malignancy for over a decade. Conventional chemotherapy and radiotherapy have shown limited efficacy in MPNST; therefore, it is imperative that targeted treatment be identified to improve the outcome for MPNST patients. Poly (ADP) ribose polymerase (PARP) inhibitors were first reported over a decade ago to have substantial anti-tumorigenic effects in malignancies with defective DNA repair, specifically those with BRCA1/2 (breast cancer, early onset 1/2) mutations. Further evaluation of these inhibitors has shown multiple mechanisms of sensitivity, all of which are associated with the DNA damage response and DNA repair. While no specific defects in DNA repair machinery have been reported in MPNST, sensitivity to PARP inhibition may be predicted by its complex karyotype and inherent genomic instability. We show increased PARP1 and PARP2 expression in MPNST patient tumor samples and increased PARP activity in cell lines. We also demonstrate the anti-MPNST effect of the PARP inhibitor AZD2281 in vitro and in vivo. Specifically, decreased cell proliferation and induction of apoptosis were observed in MPNST cell lines at AZD2281 doses and time points similar to, or less than, those used in cells lines with known DNA repair defects. In addition, AZD2281 treatment suppressed MPNST subcutaneous xenograft growth and lung metastasis progression, and increased survival times of mice with metastatic disease. Upon investigation of a potential mechanism of sensitivity, we found decreased efficacy of homologous recombination (HR) and increased activity of non-homologous end joining (NHEJ) in MPNST cell lines, suggesting a potential mechanism of sensitivity to PARP inhibition due to increased genomic instability. We also observed decreased expression of Cockayne syndrome B (CSB), a pivotal member of the transcription coupled repair (TCR) pathway. Subsequent overexpression of CSB decreased the sensitivity of a subset of MPNST cell lines to AZD2281 treatment. Our results suggest that PARP is a valuable anti-MPNST target and that sensitivity could be due to defective DNA repair pathways. Moreover, AZD2281 should be evaluated for its efficacy as a therapeutic agent for MPNST patients

KING OF THE HILL? HOW BIOTIC INTERACTIONS AFFECT BIOGEOGRAPHICAL PATTERN AND SPECIES RESPONSES TO CLIMATE CHANGE

As climate has warmed, many species have moved up mountains as physiological limits to their distributions have ameliorated. These distribution shifts are creating novel communities, begging the question: What happens to species at the tops of mountains as potential antagonists encroach upwards? Theory predicts that upward migrations will cause range contractions for high-elevation species because of novel interactions with encroaching antagonists. My dissertation work is one of the most comprehensive tests of this question to date, using a combination of ecological niche modeling (ENM), experiments, and demographic and trait-based modeling approaches. I created novel ENMs that suggest context-dependency of biotic interactions, where predictions of biotic interactions change from positive to negative over environmental gradients, is common over elevation gradients. Additionally, ENMs suggested the current focus on plant-plant interactions in niche modeling targets the most important biotic interaction for many species. I then constructed space-for-time experiments that transplanted alpine species into novel low elevation plant and mammal communities expected to encroach upwards, as well as into their native high elevation communities. Plant competition was manipulated by vegetation removals and mammals were excluded in a separate factorial experiment using below- and aboveground fencing. In both experiments, low elevation plant and mammal communities suppressed growth of alpine species to a greater extent than those antagonists found in their home range. However, demographic models suggested that environmental factors (e.g. temperature) other than novel plant and mammal communities are more consequential for determining population fate. The experiments validated a novel trait-based model of competitive interactions that can be broadly applied to other systems and conservation needs. My dissertation work found that alpine plants are unlikely to remain “king of the hill” under climate change, in part due to the upward encroachment of novel competitors and intensification of herbivore pressure