Simulated Atmospheric N Deposition Alters Fungal Community Composition and Suppresses Ligninolytic Gene Expression in a Northern Hardwood Forest

High levels of atmospheric nitrogen (N) deposition may result in greater terrestrial carbon (C) storage. In a northern hardwood ecosystem, exposure to over a decade of simulated N deposition increased C storage in soil by slowing litter decay rates, rather than increasing detrital inputs. To understand the mechanisms underlying this response, we focused on the saprotrophic fungal community residing in the forest floor and employed molecular genetic approaches to determine if the slower decomposition rates resulted from down-regulation of the transcription of key lignocellulolytic genes, by a change in fungal community composition, or by a combination of the two mechanisms. Our results indicate that across four Acer-dominated forest stands spanning a 500-km transect, community-scale expression of the cellulolytic gene cbhI under elevated N deposition did not differ significantly from that under ambient levels of N deposition. In contrast, expression of the ligninolytic gene lcc was significantly down-regulated by a factor of 2–4 fold relative to its expression under ambient N deposition. Fungal community composition was examined at the most southerly of the four sites, in which consistently lower levels of cbhI and lcc gene expression were observed over a two-year period. We recovered 19 basidiomycete and 28 ascomycete rDNA 28S operational taxonomic units; Athelia, Sistotrema, Ceratobasidium and Ceratosebacina taxa dominated the basidiomycete assemblage, and Leotiomycetes dominated the ascomycetes. Simulated N deposition increased the proportion of basidiomycete sequences recovered from forest floor, whereas the proportion of ascomycetes in the community was significantly lower under elevated N deposition. Our results suggest that chronic atmospheric N deposition may lower decomposition rates through a combination of reduced expression of ligninolytic genes such as lcc, and compositional changes in the fungal community

Leaf litter decomposition in temperate deciduous forest stands with a decreasing fraction of beech (Fagus sylvatica)

We hypothesised that the decomposition rates of leaf litter will increase along a gradient of decreasing fraction of the European beech (Fagus sylvatica) and increasing tree species diversity in the generally beech-dominated Central European temperate deciduous forests due to an increase in litter quality. We studied the decomposition of leaf litter including its lignin fraction in monospecific (pure beech) stands and in stands with up to five tree genera (Acer spp., Carpinus betulus, Fagus sylvatica, Fraxinus excelsior, Tilia spp.) using a litterbag approach. Litter and lignin decomposition was more rapid in stand-representative litter from multispecific stands than in litter from pure beech stands. Except for beech litter, the decomposition rates of species-specific tree litter did not differ significantly among the stand types, but were most rapid in Fraxinus excelsior and slowest in beech in an interspecific comparison. Pairwise comparisons of the decomposition of beech litter with litter of the other tree species (except for Acerplatanoides) revealed a “home field advantage” of up to 20% (more rapid litter decomposition in stands with a high fraction of its own species than in stands with a different tree species composition). Decomposition of stand-representative litter mixtures displayed additive characteristics, not significantly more rapid than predicted by the decomposition of litter from the individual tree species. Leaf litter decomposition rates were positively correlated with the initial N and Ca concentrations of the litter, and negatively with the initial C:N, C:P and lignin:N ratios. The results support our hypothesis that the overall decomposition rates are mainly influenced by the chemical composition of the individual litter species. Thus, the fraction of individual tree species in the species composition seems to be more important for the litter decomposition rates than tree species diversity itself

Paradox as a Metatheoretical Perspective

Organizations are rife with tensions – flexibility vs. control, exploration vs. exploitation, autocracy vs. democracy, social vs. financial, global vs. local. Researchers have long responded using contingency theory, asking “under what conditions should managers emphasize either A or B?” Yet increasingly studies apply a paradox perspective, shifting the question to: “how can we engage both A and B simultaneously?” Despite accumulating exemplars, commonalities across paradox studies remain unclear, and ties unifying this research community weak. To energize further uses of a paradox perspective, we build from past reviews to explicate its role as a metatheory. Contrasting this lens to contingency theory, we illustrate its meta-theoretical nature. We then dive deeper to sharpen the focus and widen the scope of a paradox perspective. Identifying core elements viewed from a paradox perspective – underlying assumptions, central concepts, nature of interrelationships and boundary conditions – offers a guide, informing the practice of paradox research. Next, we illustrate diverse uses of this lens. We conclude by exploring implications and next steps, stressing the rising need for paradox research, as complexity, change and ambiguity intensify demands for both/and approaches in theory and practice

Genetic polymorphisms of the RAS-cytokine pathway and chronic kidney disease

Chronic kidney disease (CKD) in children is irreversible. It is associated with renal failure progression and atherosclerotic cardiovascular (CV) abnormalities. Nearly 60% of children with CKD are affected since birth with congenital or inherited kidney disorders. Preliminary evidence primarily from adult CKD studies indicates common genetic risk factors for CKD and atherosclerotic CV disease. Although multiple physiologic pathways share common genes for CKD and CV disease, substantial evidence supports our attention to the renin angiotensin system (RAS) and the interlinked inflammatory cascade because they modulate the progressions of renal and CV disease. Gene polymorphisms in the RAS-cytokine pathway, through altered gene expression of inflammatory cytokines, are potential factors that modulate the rate of CKD progression and CV abnormalities in patients with CKD. For studying such hypotheses, the cooperative efforts among scientific groups and the availability of robust and affordable technologies to genotype thousands of single nucleotide polymorphisms (SNPs) across the genome make genome-wide association studies an attractive paradigm for studying polygenic diseases such as CKD. Although attractive, such studies should be interpreted carefully, with a fundamental understanding of their potential weaknesses. Nevertheless, whole-genome association studies for diabetic nephropathy and future studies pertaining to other types of CKD will offer further insight for the development of targeted interventions to treat CKD and associated atherosclerotic CV abnormalities in the pediatric CKD population

Paradox Research in Management Science: Looking Back to Move Forward

Paradox studies offer vital and timely insights into an array of organizational tensions. Yet this field stands at a critical juncture. Over the past 25 years, management scholars have drawn foundational insights from philosophy and psychology to apply a paradox lens to organizational phenomena. Yet extant studies selectively leverage ancient wisdom, adopting some key insights while abandoning others. Using a structured content analysis to review the burgeoning management literature, we surface six key themes, which represent the building blocks of a meta-theory of paradox. These six themes received varying attention in extant studies: paradox scholars emphasize types of paradoxes, collective approaches, and outcomes, but pay less attention to relationships within paradoxes, individual approaches, and dynamics. As this analysis suggests, management scholars have increasingly simplified the intricate, often messy phenomena of paradox. Greater simplicity renders phenomena understandable and testable, however, oversimplifying complex realities can foster reductionist and incomplete theories. We therefore propose a future research agenda targeted at enriching a meta-theory of paradox by reengaging these less developed themes. Doing so can sharpen the focus of this field, while revisiting its rich conceptual roots to capture the intricacies of paradox. This future research agenda leverages the potential of paradox across diverse streams of management science

Decomposing ability of diverse litter-decomposer macrofungi in subtropical, temperate, and subalpine forests

An integrative survey was conducted on the ability of litter-decomposing macrofungi (LDM) from forests of different climatic regions to decompose litter materials and recalcitrant compounds in the litter under pure culture conditions. A total of 75 isolates in six families of LDM from subtropical, cool temperate (CT), and subalpine (SA) forests in Japan were tested for their ability to decompose a total of eight litter types that are major substrates for macrofungi at each site. The mass loss of the litter (% original mass) during incubation for 12 weeks at 20 °C ranged from −3.1 % to 54.5 %. Macrofungi originated from forests of different climatic regions exhibited similar decomposing abilities, but the SA isolates caused negligible mass loss of Abies needles, possibly due to inhibitory compounds. Decomposing activity for recalcitrant compounds (as acid-unhydrolyzable residues, AUR) was found in many macrofungal isolates. The isolates of Marasmiaceae were generally more able to cause selective decomposition of AUR than those of Mycenaceae and to decompose AUR in partly decomposed materials. The isolates of Xylariaceae had lower ligninolytic activity than those of Basidiomycetes. The AUR mass loss caused by CT isolates was significantly lower in nitrogen-rich beech litter than in its nitrogen-poor counterpart, suggesting a retarding effect of nitrogen on AUR decomposition, which was obvious for Mycenaceae. The effect of fungal family was generally more significant than that of litter type, suggesting that possible changes in the composition of fungal assemblages influence their functioning more than changes in the quality of substrates