Preterm birth associated alterations in brain structure, cognitive functioning and behavior in children from the ABCD dataset.

BACKGROUND: Preterm birth is a global health problem and associated with increased risk of long-term developmental impairments, but findings on the adverse outcomes of prematurity have been inconsistent. METHODS: Data were obtained from the baseline session of the ongoing longitudinal Adolescent Brain and Cognitive Development (ABCD) Study. We identified 1706 preterm children and 1865 matched individuals as Control group and compared brain structure (MRI data), cognitive function and mental health symptoms. RESULTS: Results showed that preterm children had higher psychopathological risk and lower cognitive function scores compared to controls. Structural MRI analysis indicated that preterm children had higher cortical thickness in the medial orbitofrontal cortex, parahippocampal gyrus, temporal and occipital gyrus; smaller volumes in the temporal and parietal gyrus, cerebellum, insula and thalamus; and smaller fiber tract volumes in the fornix and parahippocampal-cingulum bundle. Partial correlation analyses showed that gestational age and birth weight were associated with ADHD symptoms, picvocab, flanker, reading, fluid cognition composite, crystallized cognition composite and total cognition composite scores, and measures of brain structure in regions involved with emotional regulation, attention and cognition. CONCLUSIONS: These findings suggest a complex interplay between psychopathological risk and cognitive deficits in preterm children that is associated with changes in regional brain volumes, cortical thickness, and structural connectivity among cortical and limbic brain regions critical for cognition and emotional well-being.

Associations between body mass index, sleep-disordered breathing, brain structure, and behavior in healthy children.

Pediatric overweight/obesity can lead to sleep-disordered breathing (SDB), abnormal neurological and cognitive development, and psychiatric problems, but the associations and interactions between these factors have not been fully explored. Therefore, we investigated the associations between body mass index (BMI), SDB, psychiatric and cognitive measures, and brain morphometry in 8484 children 9-11 years old using the Adolescent Brain Cognitive Development dataset. BMI was positively associated with SDB, and both were negatively correlated with cortical thickness in lingual gyrus and lateral orbitofrontal cortex, and cortical volumes in postcentral gyrus, precentral gyrus, precuneus, superior parietal lobule, and insula. Mediation analysis showed that SDB partially mediated the effect of overweight/obesity on these brain regions. Dimensional psychopathology (including aggressive behavior and externalizing problem) and cognitive function were correlated with BMI and SDB. SDB and cortical volumes in precentral gyrus and insula mediated the correlations between BMI and externalizing problem and matrix reasoning ability. Comparisons by sex showed that obesity and SDB had a greater impact on brain measures, cognitive function, and mental health in girls than in boys. These findings suggest that preventing childhood obesity will help decrease SDB symptom burden, abnormal neurological and cognitive development, and psychiatric problems.

Associations among body mass index, working memory performance, gray matter volume, and brain activation in healthy children.

To investigate the neural mechanisms underlying the association between poorer working memory performance and higher body mass index (BMI) in children. We employed structural-(sMRI) and functional magnetic resonance imaging (fMRI) with a 2-back working memory task to examine brain abnormalities and their associations with BMI and working memory performance in 232 children with overweight/obesity (OW/OB) and 244 normal weight children (NW) from the Adolescent Brain Cognitive Development dataset. OW/OB had lower working memory accuracy, which was associated with higher BMI. They showed smaller gray matter (GM) volumes in the left superior frontal gyrus (SFG_L), dorsal anterior cingulate cortex, medial orbital frontal cortex, and medial superior frontal gyrus, which were associated with lower working memory accuracy. During the working memory task, OW/OB relative to NW showed weaker activation in the left superior temporal pole, amygdala, insula, and bilateral caudate. In addition, caudate activation mediated the relationship between higher BMI and lower working memory accuracy. Higher BMI is associated with smaller GM volumes and weaker brain activation in regions involved with working memory. Task-related caudate dysfunction may account for lower working memory accuracy in children with higher BMI.

Leguminous plants significantly increase soil nitrogen cycling across global climates and ecosystem types.

Leguminous plants are an important component of terrestrial ecosystems and significantly increase soil nitrogen (N) cycling and availability, which affects productivity in most ecosystems. Clarifying whether the effects of legumes on N cycling vary with contrasting ecosystem types and climatic regions is crucial for understanding and predicting ecosystem processes, but these effects are currently unknown. By conducting a global meta-analysis, we revealed that legumes increased the soil net N mineralization rate (Rmin ) by 67%, which was greater than the recently reported increase associated with N deposition (25%). This effect was similar for tropical (53%) and temperate regions (81%) but was significantly greater in grasslands (151%) and forests (74%) than in croplands (-3%) and was greater in in situ incubation (101%) or short-term experiments (112%) than in laboratory incubation (55%) or long-term experiments (37%). Legumes significantly influenced the dependence of Rmin on N fertilization and experimental factors. The Rmin was significantly increased by N fertilization in the nonlegume soils, but not in the legume soils. In addition, the effects of mean annual temperature, soil nutrients and experimental duration on Rmin were smaller in the legume soils than in the nonlegume soils. Collectively, our results highlighted the significant positive effects of legumes on soil N cycling, and indicated that the effects of legumes should be elucidated when addressing the response of soils to plants.

Trajectory Planning for Coal Gangue Sorting Robot Tracking Fast-Mass Target under Multiple Constraints.

Aiming at the problems of grab failure and manipulator damage, this paper proposes a dynamic gangue trajectory planning method for the manipulator synchronous tracking under multi-constraint conditions. The main reason for the impact load is that there is a speed difference between the end of the manipulator and the target when the manipulator grabs the target. In this method, the mathematical model of seven-segment manipulator trajectory planning is constructed first. The mathematical model of synchronous tracking of dynamic targets based on a time-minimum manipulator is constructed by taking the robot's acceleration, speed, and synchronization as constraints. The model transforms the multi-constraint-solving problem into a single-objective-solving problem. Finally, the particle swarm optimization algorithm is used to solve the model. The calculation results are put into the trajectory planning model of the manipulator to obtain the synchronous tracking trajectory of the manipulator. Simulation and experiments show that each joint of the robot's arm can synchronously track dynamic targets within the constraint range. This method can ensure the synchronization of the position, speed, and acceleration of the moving target and the target after tracking. The average position error is 2.1 mm, and the average speed error is 7.4 mm/s. The robot has a high tracking accuracy, which further improves the robot's grasping stability and success rate.

Earthworms regulate plants' effects on soil microbial nutrient limitations: Examinations with contrasting soils and moisture.

Soil microbial nutrient limitations significantly affect microbial processes and thus ecosystem functionality, whereas the response of soil microbial nutrient limitations to earthworms has rarely been addressed but is urgently needed due to the important role of earthworms in terrestrial ecosystems. By examining how earthworms regulate plants' effects on microbial nutrient limitations under contrasting soil types and moisture conditions, we showed that plant presence reduced microbial carbon (C) limitation and such reduction was enhanced by earthworm. Plant presence increased soil microbial phosphorus (P) limitation in soils with earthworms in most cases. Additionally, the effects of plants on microbial nutrient limitations and their responses to earthworms were dependent on soil type (or soil nutrients) and moisture. These results suggested that earthworms have the potential to reduce soil microbial C limitation but enhance P limitation and highlighted the importance of nutrients and moisture in influencing the effects of earthworms and plants on microbial nutrient limitations.

Afforestation can lower microbial diversity and functionality in deep soil layers in a semiarid region.

Afforestation is an effective approach to rehabilitate degraded ecosystems, but often depletes deep soil moisture. Presently, it is not known how an afforestation-induced decrease in moisture affects soil microbial community and functionality, hindering our ability to understand the sustainability of the rehabilitated ecosystems. To address this issue, we examined the impacts of 20 years of afforestation on soil bacterial community, co-occurrence pattern, and functionalities along vertical profile (0-500 cm depth) in a semiarid region of China's Loess Plateau. We showed that the effects of afforestation with a deep-rooted legume tree on cropland were greater in deep than that of in top layers, resulting in decreased bacterial beta diversity, more responsive bacterial taxa and functional groups, increased homogeneous selection, and decreased network robustness in deep soils (120-500 cm). Organic carbon and nitrogen decomposition rates and multifunctionality also significantly decreased by afforestation, and microbial carbon limitation significantly increased in deep soils. Moreover, changes in microbial community and functionality in deep layer was largely related to changes in soil moisture. Such negative impacts on deep soils should be fully considered for assessing afforestation's eco-environment effects and for the sustainability of ecosystems because deep soils have important influence on forest ecosystems in semiarid and arid climates.

Tracing the Sources and Fate of NO3- in the Vadose Zone-Groundwater System of a Thousand-Year-Cultivated Region.

Excess nitrate (NO3-) loading in terrestrial and aquatic ecosystems can result in critical environmental and health issues. NO3--rich groundwater has been recorded in the Guanzhong Plain in the Yellow River Basin of China for over 1000 years. To assess the sources and fate of NO3- in the vadose zone and groundwater, numerous samples were collected via borehole drilling and field surveys, followed by analysis and stable NO3- isotope quantification. The results demonstrated that the NO3- concentration in 38% of the groundwater samples exceeded the limit set by the World Health Organization. The total NO3- stock in the 0-10 m soil profile of the orchards was 3.7 times higher than that of the croplands, suggesting that the cropland-to-orchard transition aggravated NO3- accumulation in the deep vadose zone. Based on a Bayesian mixing model applied to stable NO3- isotopes (δ15N and δ18O), NO3- accumulation in the vadose zone was predominantly from manure and sewage N (MN, 27-54%), soil N (SN, 0-64%), and chemical N fertilizer (FN, 4-46%). MN was, by far, the greatest contributor to groundwater NO3- (58-82%). The results also indicated that groundwater NO3- was mainly associated with the soil and hydrogeochemical characteristics, whereas no relationship with modern agricultural activities was observed, likely due to the time delay in the thick vadose zone. The estimated residence time of NO3- in the vadose zone varied from decades to centuries; however, NO3- might reach the aquifer in the near future in areas with recent FN loading, especially those under cropland-to-orchard transition or where the vadose zone is relatively thin. This study suggests that future agricultural land-use transitions from croplands to orchards should be promoted with caution in areas with shallow vadose zones and coarse soil texture.

Boreal and temperate trees show strong acclimation of respiration to warming.

Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 °C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated.

Rapid and efficient reduction of chromate by novel Pd/Fe@biomass derived from Enterococcus faecalis.

Efficient reduction of chromate is highly desirable for its detoxification and remediation of the contaminated environment. This study described a fusion of the concepts of precious metal biorecovery and fabrication of Pd/Fe@biomass derived from simulated wastewater. The effectiveness of Pd/Fe@biomass during reduction process of Cr(VI) was evaluated by comparing with pure nZVI, E. faecalis and Pd@biomass. Results showed that Pd(II) could be recovered by E. faecalis with Fe(II) as the electron donor, and precipitation could yield nZVI anchored onto Pd-loaded E. faecalis. The nano particles (NPs) on Pd/Fe@biomass were well-dispersed, which provided 2.70 folds specific surface area comparing with nZVI. Efficient Cr(VI) reduction could be achieved at a higher catalyst dosage, the most appropriated Pd/Fe molar ratio of 2% and a wide pH range. Typically, 0.5 mM Cr(VI) could be completely reduced in 5 min driven by Pd/Fe@biomass under the conditions of dosage of 1.0 g/L and pH 3. Moreover, the mechanisms of Cr(VI) reduction by Pd/Fe@biomass were proposed, which intimately related to nZVI electron donating capacities, Pd catalysis for hydrogenation and galvanic cell effects between Fe and Pd. Therefore, Pd/Fe@biomass could be an alternative for rapid and complete reduction of Cr(VI).

Multi-Arm Global Cooperative Coal Gangue Sorting Method Based on Improved Hungarian Algorithm.

The existing multi-manipulator sorting method for gangue that utilizes a multi-task allocation strategy is not satisfactory. The single manipulator working space is fixed, lowering the cooperation degree between the manipulators and leading to a low sorting rate. Therefore, this paper proposes a multi-manipulator cooperative sorting method that can work globally. First, a benefit function based on the sorting time and quality of the gangue is constructed by combining the gangue flow information and the manipulator state. The time parameter is obtained via the manipulator's dynamic target tracking trajectory planning algorithm based on PID control. Secondly, the benefits matrix is standardized and updated many times to improve the Hungarian algorithm to achieve task allocation, and the initial solution with priority is obtained. Finally, the solutions are analyzed and processed cooperatively in order of priority. The conflicts between multiple robotic arms are eliminated through task cooperation and trajectory cooperation until the sorting task that the robot arm can execute is obtained from the allocation results. Experiments involving different sorting methods were completed on a multi-arm coal and gangue sorting experimental robot platform. The experimental results show that the sorting efficiency of the proposed method is about 10% and 20% higher than that of the fixed space dynamic and designated space fixed points methods, respectively, under different belt speeds. This method can guarantee system benefits, effectively implements cooperative control of multi-manipulator operations in the whole area, and improves the efficiency of coal gangue sorting.

Assessing the relevant time frame for temperature acclimation of leaf dark respiration: A test with 10 boreal and temperate species.

Plants often adjust their leaf mitochondrial ("dark") respiration (Rd ) measured at a standardized temperature such as 20°C (R20 ) downward after experiencing warmer temperatures and upward after experiencing cooler temperatures. These responses may help leaves maintain advantageous photosynthetic capacity and/or be a response to recent photosynthate accumulation, and can occur within days after a change in thermal regime. It is not clear, however, how the sensitivity and magnitude of this response change over time, or which time period prior to a given measurement best predicts R20 . Nor is it known whether nighttime, daytime, or 24-hour temperatures should be most influential. To address these issues, we used data from 1620 Rd temperature response curves of 10 temperate and boreal tree species in a long-term field experiment in Minnesota, USA to assess how the observed nearly complete acclimation of R20 was related to past temperatures during periods of differing lengths. We hypothesized that R20 would be best related to prior midday temperatures associated with both photosynthetic biochemistry and peak carbon uptake rates that drive carbohydrate accumulation. Inconsistent with this hypothesis, prior night temperatures were the best predictors of R20 for all species. We had also hypothesized that recent (prior 3-10 days) temperatures should best predict R20 because they likely have stronger residual impacts on leaf-level physiology than periods extending further back in time, whereas a prior 1- to 2-day period might be a span shorter than one to which photosynthetic capacity and Rd adjust. There was little to no support for this idea, as for angiosperms, long time windows (prior 30-60 nights) were the best predictors, while for gymnosperms both near-term (prior 3-8 nights for pines, prior 10-14 nights for spruce/fir) and longer-term periods (prior 45 nights) were the best predictors. The importance of nighttime temperatures, the relatively long "time-averaging" that best explained acclimation, and dual peaks of temporal acclimation responsiveness in some species were all results that were unanticipated.

Efficient separation of aluminum foil from mixed-type spent lithium-ion power batteries.

The disposal of spent lithium-ion power batteries (LIBs) has become an important research topic owing to the booming market for electric vehicles. However, the recovery efficiency of the alkaline solution and organic solvent methods currently used to separate Al foil from cathode materials still has room for improvement. The insufficient separation of Al foil and complexity of the battery types present obstacles to the extraction of valuable metals using simple processes. In this study, an efficient approach is developed to separate the Al foil in mixed-type spent LIBs (M-LIBs), namely, LiNixCoyMnzO2 (NCM), LiFePO4 (LFP), and LiMn2O4 (LMO) LIBs, by controlled pyrolysis. Hundred percent of the Al foil was recovered at the temperature of 450 °C, holding time of 60 min, and heating rate of 10 °C/min. The purity of Al in the recovered foil was 99.41 %, 99.83 % and 99.92 %, and the recovery efficiency of the active cathode materials was 96.01 %, 99.80 % and 99.15 % for NCM, LFP and LMO, respectively, without the loss of active cathode materials. The obtained active cathode materials exhibited a favorable crystalline structure, and the average particle diameter was reduced from 300.497 to 24.316 µm with a smaller and looser morphology. The process could be well fitted with the Friedman differential equation, and the correlation coefficients were higher than 0.99. The efficient separation could be attributed to the complete rupture of long chain -(CH2CF2)-n bonds in the poly (vinylidene difluoride) (PVDF) binder, which resulted in the formation of HF, trifluorobenzene, alkanes, and gaseous single molecule CH2CF2. Therefore, this work potentially provides an alternative approach for the efficient separation of Al foil in M-LIBs, thereby simplifying the process and achieving lower cost, reduced loss of valuable metals, and higher recovery efficiency.

Dam Construction as an Important Anthropogenic Activity Disturbing Soil Organic Carbon in Affected Watersheds.

To explore whether and how anthropogenic activities related to surface water regulation (i.e., dam construction) disturb soil ecosystems in the surrounding uplands, a long-term monitoring program was conducted from 1998 to 2017 in the Three Gorges Reservoir Region, China. The Three Gorges Dam (TGD) is the largest hydraulic engineering project in the world. We present a direct, ecosystem-scale demonstration of changes in the soil organic carbon (SOC) content in the TGD watershed before and after the surface water was reshaped. The average SOC content decreased from 12.9 to 9.5 g/kg between 2004 and 2012 and then recovered to 13.8 g/kg in 2017. Dynamics of SOC were partly attributed to shifts in the composition of soil microbial communities responsible for carbon biogeochemistry. The shifts in microbial taxa were associated with the changed microclimate affected by the TGD as well as global and regional climate variability. The microclimate, soil microorganisms, and plant organic carbon input explained 40.2% of the variation in the SOC content. This study revealed that dam construction was an important and indirect driver for the SOC turnover, and the subsequent effects on the upland soil ecosystem must be considered when large-scale disturbance activities (such as dam construction) are conducted in the future.

Efficient degradation of sodium diclofenac via heterogeneous Fenton reaction boosted by Pd/Fe@Fe3O4 nanoparticles derived from bio-recovered palladium.

Dehalogenation of emerging pollutants has attracted worldwide attention. In this study, novel bio-Pd/Fe@Fe3O4 nanoparticles (NPs) were proposed to boost the heterogeneous Fenton reaction for degradation of sodium diclofenac (DCF). Specifically, Enterococcus faecalis (E. faecalis) was employed to achieve bio-recovered palladium (bio-Pd). Results showed that expected preparation of bio-Pd/Fe@Fe3O4 NPs was confirmed by various characterization techniques. The prepared bio-Pd/Fe@Fe3O4 NPs were spherical morphology with average size of 9 nm. Under the optimum conditions, the removal efficiency of 10 mg/L DCF in 20 min and 40 min reached as high as 94.69% and 99.65%, respectively. The dechlorination and mineralization efficiencies of DCF were 85.16% and 59.21% in 120 min, respectively. The main degradation pathway of DCF was complete mineralization with the final products CO2, chloride ions and H2O. The improvement of dechlorination efficiency was ascribed to the accelerated corrosion of nano zero valent iron (nZVI) by Pd/Fe galvanic effect and the rise of active hydrogen. Meanwhile, more ferrous ions were released into this solution, resulting in the higher heterogeneous Fenton reaction rate driven by bio-Pd/Fe@Fe3O4 NPs. Therefore, the findings suggested that bio-Pd/Fe@Fe3O4 NPs were effective catalysts for DCF dechlorination and mineralization. The work provided a novel strategy for degradation of halogen-containing environmental pollutants.

Legumes regulate grassland soil N cycling and its response to variation in species diversity and N supply but not CO2.

Legumes are an important component of plant diversity that modulate nitrogen (N) cycling in many terrestrial ecosystems. Limited knowledge of legume effects on soil N cycling and its response to global change factors and plant diversity hinders a general understanding of whether and how legumes broadly regulate the response of soil N availability to those factors. In a 17-year study of perennial grassland species grown under ambient and elevated (+180 ppm) CO2 and ambient and enriched (+4 g N m-2  year-1 ) N environments, we compared pure legume plots with plots dominated by or including other herbaceous functional groups (and containing one or four species) to assess the effect of legumes on N cycling (net N mineralization rate and inorganic N pools). We also examined the effects of numbers of legume species (from zero to four) in four-species mixed plots on soil N cycling. We hypothesized that legumes would increase N mineralization rates most in those treatments with the greatest diversity and the greatest relative limitation by and competition for N. Results partially supported these hypotheses. Plots with greater dominance by legumes had greater soil nitrate concentrations and mineralization rates. Higher species richness significantly increased the impact of legumes on soil N metrics, with 349% and 505% higher mineralization rates and nitrate concentrations in four-species plots containing legumes compared to legume-free four-species plots, in contrast to 185% and 129% greater values, respectively, in pure legume than nonlegume monoculture plots. N-fertilized plots had greater legume effects on soil nitrate, but lower legume effects on net N mineralization. In contrast, neither elevated CO2 nor its interaction with legumes affected net N mineralization. These results indicate that legumes markedly influence the response of soil N cycling to some, but not all, global change drivers.

Disentangling species and functional group richness effects on soil N cycling in a grassland ecosystem.

Species richness (SR) and functional group richness (FGR) are often confounded in both observational and experimental field studies of biodiversity and ecosystem function. This precludes discernment of their separate influences on ecosystem processes, including nitrogen (N) cycling, and how those influences might be moderated by global change factors. In a 17-year field study of grassland species, we used two full factorial experiments to independently vary SR (one or four species, with FGR = 1) and FGR (1-4 groups, with SR = 4) to assess SR and FGR effects on ecosystem N cycling and its response to elevated carbon dioxide (CO2 ) and N addition. We hypothesized that increased plant diversity (either SR or FGR) and elevated CO2 would enhance plant N pools because of greater plant N uptake, but decrease soil N cycling rates because of greater soil carbon inputs and microbial N immobilization. In partial support of these hypotheses, increasing SR or FGR (holding the other constant) enhanced total plant N pools and decreased soil nitrate pools, largely through higher root biomass, and increasing FGR strongly reduced mineralization rates, because of lower root N concentrations. In contrast, increasing SR (holding FGR constant and despite increasing total plant C and N pools) did not alter root N concentrations or net N mineralization rates. Elevated CO2 had minimal effects on plant and soil N metrics and their responses to plant diversity, whereas enriched N increased plant and soil N pools, but not soil N fluxes. These results show that functional diversity had additional effects on both plant N pools and rates of soil N cycling that were independent of those of species richness.

Response of soil CO2 efflux to precipitation manipulation in a semiarid grassland.

Soil CO2 efflux (SCE) is an important component of ecosystem CO2 exchange and is largely temperature and moisture dependent, providing feedback between C cycling and the climate system. We used a precipitation manipulation experiment to examine the effects of precipitation treatment on SCE and its dependences on soil temperature and moisture in a semiarid grassland. Precipitation manipulation included ambient precipitation, decreased precipitation (-43%), or increased precipitation (+17%). The SCE was measured from July 2013 to December 2014, and CO2 emission during the experimental period was assessed. The response curves of SCE to soil temperature and moisture were analyzed to determine whether the dependence of SCE on soil temperature or moisture varied with precipitation manipulation. The SCE significantly varied seasonally but was not affected by precipitation treatments regardless of season. Increasing precipitation resulted in an upward shift of SCE-temperature response curves and rightward shift of SCE-moisture response curves, while decreasing precipitation resulted in opposite shifts of such response curves. These shifts in the SCE response curves suggested that increasing precipitation strengthened the dependence of SCE on temperature or moisture, and decreasing precipitation weakened such dependences. Such shifts affected the predictions in soil CO2 emissions for different precipitation treatments. When considering such shifts, decreasing or increasing precipitation resulted in 43 or 75% less change, respectively, in CO2 emission compared with changes in emissions predicted without considering such shifts. Furthermore, the effects of shifts in SCE response curves on CO2 emission prediction were greater during the growing than the non-growing season.

Acclimation of photosynthetic temperature optima of temperate and boreal tree species in response to experimental forest warming.

Rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain. Such changes may threaten temperature-sensitive species, causing local extinctions and range migrations. This study examined the optimal temperature of net photosynthesis (Topt ) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota, United States under two contrasting temperature regimes. We hypothesized that Topt would be higher in temperate than co-occurring boreal species, with temperate species exhibiting greater plasticity in Topt , resulting in better acclimation to elevated temperatures. The chamberless experiment, located at two sites in both open and understory conditions, continuously warmed plants and soils during three growing seasons. Results show a modest, but significant shift in Topt of 1.1 ± 0.21 °C on average for plants subjected to a mean 2.9 ± 0.01 °C warming during midday hours in summer, and shifts with warming were unrelated to species native ranges. The 1.1 °C shift in Topt with 2.9 °C warming might be interpreted as suggesting limited capacity to shift temperature response functions to better match changes in temperature. However, Topt of warmed plants was as well-matched with prior midday temperatures as Topt of plants in the ambient treatment, and Topt in both treatments was at a level where realized photosynthesis was within 90-95% of maximum. These results suggest that seedlings of all species were close to optimizing photosynthetic temperature responses, and equally so in both temperature treatments. Our study suggests that temperate and boreal species have considerable capacity to match their photosynthetic temperature response functions to prevailing growing season temperatures that occur today and to those that will likely occur in the coming decades under climate change.

Humic acid transport in saturated porous media: influence of flow velocity and influent concentration.

Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.