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Replacing long-lived, rarely disturbed vegetation with short-lived, frequently disturbed vegetation is a widespread phenomenon in the Anthropocene that can influence ecosystem functioning and soil development by reducing the abundance of deep roots. We explore how sources and fate of soil CO2 vary with organic substrate source, abundance of respiring biota (i.e., roots and soil microbes), season, and soil depth. We quantified multiple isotopic signatures of CO2 (δ13C, Δ14C, δ18O) as well as concentrations and δ18O of free O2 in the upper 5 m of soil at sites where root abundances and soil organic C have been previously quantified: in late-successional forests, cultivated fields, and ~ 80 y old regenerating pine forests growing on previously cultivated land. We hypothesized that soil CO2sources would vary across soil depth and land cover, reflecting varying abundances of organic substrates, and seasonally as the dominance of root vs. microbial CO2 production changes through the year. δ13C–CO2 revealed respiration of C4-derived substrates in cultivated fields particularly during the growing season. This effect was not evident in soils of regenerating pine or older hardwood forests, suggesting that ~ 80 y of pine inputs to reforested soils have been sufficient to dominate microbial substrate selection over any remnant, historic agricultural C4 inputs. Δ14C–CO2 diverged by land use at 3 and 5 m, indicating that more recently-produced photosynthate is available for mineralization in forests compared to cultivated plots, and in late-successional forests compared to regenerating pine forests. At 1.5, 3, and 5 m in forested plots we observed evidence of respiratory demands on soil pore space O2. In these soils, we observed declines in [O2] compared to other depths and to the agricultural plots and concurrent increases in δ18O of free O2, consistent with the idea that roots and heterotrophic soil microbes are more active where photosynthate is more available. The δ18O–CO2 values, a likely proxy for δ18O of soil porewater, exhibited 18O enrichment during the winter, when many sampling wells were flooded, compared to growing season values. These data suggest an isotopically-distinct and laterally-flowing source of CO2-laden porewater during winter months. Combined, these datasets document how ~ 80 y of forest regeneration can provide sufficient C inputs to mask any microbial mineralization of decades-old organic inputs, but belowground C inputs still lag those of late successional forests. We also infer that lateral and vertical flows of water can serve as a sink for biotically-generated CO2, and that where deep soil [CO2] is lower due to lower root and microbial activities, production of carbonic acid is also diminished. Where reaction rates are weathering limited, a paucity of deep roots imposed by anthropogenic land cover change thus may limit the production of this agent of soil development and the C sink represented by the silicate weathering it can promote. The data suggest deep and persistent effects of the loss of deeply rooted long-lived vegetation on deep soil C storage and transformations that promote acid-dissolution weathering reactions that help form soil itself. [ABSTRACT FROM AUTHOR]

Community composition in semi-arid ecosystems has largely been explained by water availability; however, nitrogen is a common limiting nutrient, and may be an important control on plant function and carbon uptake. We investigated nitrogen relations and photosynthesis of several dominant species at shallow groundwater sites in Owens Valley, California. We measured soil nitrogen (N) availability, leaf N and isotopes, water isotopes, and gas exchange of dominant shrub species Atriplex torreyi and Ericameria nauseosa and grass species Distichlis spicata throughout the summer season in three sites that had similar watertable depths, but that varied in community composition and N availability. Surface soil inorganic N was greatest at the grassland site and declined from June to September at all sites. Leaf N declined throughout the season in all species, and was correlated with soil inorganic N. Photosynthesis of A. torreyi remained relatively constant throughout the season. In contrast, D. spicata and E. nauseosa experienced seasonal declines in photosynthesis at sites with greater inorganic N availability. Leaf N was significantly correlated with photosynthesis in D. spicata across all sites and measurement periods. Controls on N cycling are likely to be an important determinant of photosynthesis of D. spicata in this region.

Mammalian inner ear hair cell loss leads to permanent hearing and balance dysfunction. In contrast to the cochlea, vestibular hair cells of the murine utricle have some regenerative capacity. Whether human utricular hair cells regenerate in vivo remains unknown. Here we procured live, mature utricles from organ donors (9 ears from 6 organ donors) and vestibular schwannoma patients (24 ears from 24 patients), and presented a single-cell transcriptomic atlas at unprecedented resolution. We validated marker genes using immunostaining and RNAscope in situ hybridization and described previously unknown markers of 13 sensory and non-sensory cell types. In addition, we compared and found partial overlap and correlation between transcriptomes of human and mouse hair cells and supporting cells. We further uncovered transcriptomes unique to hair cell precursors, which are validated in both organ donor and vestibular schwannoma utricles. Unexpectedly we found 14-fold more hair cell precursors in vestibular schwannoma utricles, demonstrating the existence of ongoing regeneration in humans. Lastly, supporting cell-to-hair cell trajectory analysis revealed 5 distinct patterns of dynamic gene expression and associated pathways. Our data-set constitutes a foundational resource, accessible via a web-based interface, serving to advance knowledge of the normal and diseased human inner ear. [ABSTRACT FROM AUTHOR]

Using Genetic Algorithms (GAs) to search for cellular automation (CA) rules from spatio-temporal patterns produced in CA evolution is usually complicated and time-consuming when both the neighborhood structure and the local rule are searched simultaneously. The complexity of this problem motivates the development of a new search which separates the neighborhood detection from the GA search. In this paper, the neighborhood is determined by independently selecting terms from a large term set on the basis of the contribution each term makes to the next state of the cell to be updated. The GA search is then started with a considerably smaller set of candidate rules pre-defined by the detected neighborhood. This approach is tested over a large set of one-dimensional (1-D) and two-dimensional (2-D) CA rules. Simulation results illustrate the efficiency of the new algorithm. Index Terms--Cellular automata, genetic algorithms, identification, spatio-temporal systems.

A multiobjective genetic algorithm (GA) is introduced to identify both the neighborhood and the rule set in the form of a parsimonious Boolean expression for both one- and two-dimensional cellular automata (CA). Simulation results illustrate that the new algorithm performs well even when the patterns are corrupted by static and dynamic noise. Index Terms--Boolean identification, cellular automata, genetic algorithms, spatio-temporal systems.

In this paper, a new method for evaluating output frequency responses of nonlinear systems under multiple inputs, defined as a sum of sinusoids of different frequencies, is developed. The method circumvents difficulties associated with the existing 'frequency-mix vector' based approaches and can easily be applied to investigate nonlinear behaviors of practical systems, including electronic circuits, at the system simulation and design stages. Application of the method to the analysis of nonlinear interference and distortion effects in communication receivers is studied, and specific procedures are proposed which can be directly used in practice for this analysis. Index Terms--Communication receivers, frequency-domain analysis, nonlinear systems/circuits.

Understanding how tree growth strategies may influence tree susceptibility to disturbance is an important goal, especially given projected increases in diverse ecological disturbances this century. We use growth responses of tree rings to climate, relationships between tree-ring stable isotopic signatures of carbon (δ13C) and oxygen (δ18O), wood nitrogen concentration [N], and contemporary leaf [N] and δ13C values to assess potential historic drivers of tree photosynthesis in dying and apparently healthy co-occurring northern red oak (Quercus rubra L. (Fagaceae)) during a region-wide oak decline event in Arkansas, USA. Bole growth of both healthy and dying trees responded negatively to drought severity (Palmer Drought Severity Index) and temperature; healthy trees exhibited a positive, but small, response to growing season precipitation. Contrary to expectations, tree-ring δ13C did not increase with drought severity. A significantly positive relationship between tree-ring δ13C and δ18O was evident in dying trees (P < 0.05) but not in healthy trees. Healthy trees' wood exhibited lower [N] than that of dying trees throughout most of their lives (P < 0.05), and we observed a significant, positive relationship (P < 0.05) in healthy trees between contemporary leaf δ13C and leaf N (by mass), but not in dying trees. Our work provides evidence that for plants in which strong relationships between δ13C and δ18O are not evident, δ13C may be governed by plant N status. The data further imply that historic photosynthesis in healthy trees was linked to N status and, perhaps, C sink strength to a greater extent than in dying trees, in which treering stable isotopes suggest that historic photosynthesis was governed primarily by stomatal regulation. This, in turn, suggests that assessing the relative dominance of photosynthetic capacity vs stomatal regulation as drivers of trees' C accrual may be a feasible means of predicting tree responses to some disturbance events. Our work demonstrates that a dual isotope, tree-ring approach can be integrated with tree N status to begin to unravel a fundamental question in forest ecology: why do some trees die during a disturbance, while other conspecifics with apparently similar access to resources remain healthy? [ABSTRACT FROM AUTHOR]