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A novel variation of the mixed lymphocyte reaction for measuring T cell responses to skin-specific antigens of pigs
No full textSkin and vascularized composite allografts (VCA) containing skin are transplanted to restore form and function of tissues after major injuries. Skin has long been recognized as being particularly immunogenic, causing high risk of rejection and immune sensitization. Due to skin-specific antigens, donor skin is often rejected even in animals that are tolerant of the remaining donor tissue. To study the reaction of lymphocyte subsets against these minor and/or tissue-specific skin antigens in swine made tolerant to allogeneic donors through hematopoietic stem cell transplants (HSCT), we developed a skin-adapted variation of the mixed lymphocyte reaction (MLR). We processed porcine skin into single cell suspensions to be used as stimulators. Peripheral blood mononuclear cells were used as responders. We first optimized the concentrations of skin stimulators to achieve T cell proliferation with minimal self-background reactivity. The assay was then tested in two pigs that had received combined VCA/ HSCT. The first pig had not rejected any part of the VCA, and the second pig was actively rejecting the epidermis of the VCA at the time of the assay. Despite lack of anti-donor MLR responses against donor lymphocytes in the peripheral blood in either animal, the second pig demonstrated a specific response against donor skin cells. Our results suggest that the assay will be useful to study recipient sensitization against skin antigens, even in otherwise tolerant animals. This assay may have both diagnostic and therapeutic implications for immune responses specific to the skin
Limited response of boreal forest litterfall mercury deposition to declines in atmospheric mercury concentrations (1987-2000)
No full textAtmospheric mercury (Hg) uptake by vegetation and subsequent deposition via litterfall constitutes a major pathway in the global Hg cycle. However, the temporal dynamics of litterfall Hg deposition and its environmental controls remain poorly understood. Here, we present a detailed assessment of Hg concentrations and deposition fluxes for individual litter components in a Swedish boreal forest from 1987 to 2000. Atmospheric Hg concentrations declined 41 % during this period. Correspondingly, Hg concentrations in Scots pine and Norway spruce needles decreased significantly (similar to 22 % and similar to 26 %, respectively). However, the total litterfall Hg deposition flux remained stable at 11.7 +/- 1.8 mu g m(-2) yr(-1), showing no clear temporal trend. Foliar litter (needles) contributed 44 % of total Hg deposition, while non-foliar litter (twigs, residual material, and cones) accounted for the remaining 56 % (32 %, 22 %, and 2 %, respectively). The importance of this non-foliar component in modulating litterfall Hg deposition is often overlooked. Litterfall Hg deposition was 1.7 times higher in the non-growing season than in the growing season, primarily due to greater litterfall biomass. The weak response of litterfall Hg deposition to declining atmospheric Hg concentrations highlights the importance of biological factors (e.g., litterfall compositions and productivity) in regulating Hg inputs to boreal forest. Our findings also underscore the need for long-term assessments of Hg deposition dynamics via different litterfall components for assessing the effectiveness of the Minamata Convention on Mercury
Boreal tree species selection enhances forest carbon stocks through above-rather than below-ground changes
No full textForest management has the potential to impact the net forest carbon (C) balance, and a better understanding of how tree species influence soil C provides a potential tool to promote higher C uptake and storage in forests. In this study, we utilized two common garden experiments located in northern and central Sweden to compare soil organic C stocks associated with six different boreal tree species (Betula pendula, Larix sp., Picea abies, Picea glauca, Pinus contorta and Pinus sylvestris), approximately 30 years after planting. We measured both above-and below-ground C inputs and C outputs via decomposition and analyzed how these factors influenced soil C stocks. Our results showed that the vertical distribution of SOC differed between the species, and furthermore, many of the SOC input and output processes measured were species-dependent. Despite this, we found no differences in total belowground soil C stock between the species. The aboveground biomass C stocks, in contrast, were highly species-specific, with the rank order of species differing between the two sites. As such, our study indicates that tree species choice may serve as a tool to promote ecosystem C stocks, and in turn enhance the climate change mitigation potential of forests
The PeatPic project: predicting plot-scale green leaf phenology across peatlands
No full textPeatlands store approximately one-third of the world's soil carbon (C), but their functioning is highly variable at fine spatial scales due to differences in vegetation cover and environmental conditions such as water table depth. This fine-scale heterogeneity plays a key role in carbon dynamics yet capturing it-particularly in relation to green leaf phenology (GLP)-is challenging with traditional remote sensing methods. To address this, we developed a smartphone-based methodology and community-science project called the PeatPic Project. We gathered over 3700 photographs from 27 sites across 10 countries in 2021 and 2022, representing different peatland types (bog, fen, and swamp), at 1-2 week intervals. We calculated GLP metrics, such as the data of the start of the season and end of the season, based on the red-blue-green bands from these photographs. We found that GLP metrics varied significantly across peatland types and dominant vegetation communities. Notably, peak greenness at bog sites occurring approximately 10 days later in the year compared to fen sites. Furthermore, variables relation to peatland/vegetation type and energy balance were key predictors of peatland GLP. The PeatPic Project's readily available methodology offers low-cost opportunities for further research into peatland phenology, enabling the calculation of additional phenological indices and integration with other data types. By refining our understanding of peatland GLP, we can improve predictive C modelling and better assess the impacts of future changes on these important ecosystems
Ecosystems mediate climate impacts on northern hemisphere seabirds
No full textEcosystem structure and biophysical processes mediate biological responses to climate changes, but few studies have examined impacts of this dynamic among upper trophic levels. We investigated ecosystem differences in how diverse seabird populations across the northern hemisphere have responded to changes in regional mixed layer temperature and water column stratification. Using 138 time series of breeding productivity over the past half-century, we show that seabird reproductive productivity has declined in the Arctic and North Atlantic but not in the Pacific during a period of ubiquitous mixed layer warming and regionally-variable stratification trends. Models of breeding productivity and ocean drivers show that seabird responses to climate change vary by ecosystem. Additionally, ecosystems in which seabirds exhibit detectibly declining productivity tend to have lower overall diet diversity across seabird species. These findings emphasize the importance of ecosystem processes and structure in determining the vulnerability of marine predators to climate change
Visual Soil Structure Quality Is Mostly Explained by Small-Size Structural Pores
No full textVisual assessment of soil structure receives growing interest but its physical meaning is still to be explored. This study examined the relationships between soil pore systems volume and size distribution and visual structure quality scores in undisturbed soil samples from Swiss cropland soils covering a wide range of soil organic carbon (SOC) and clay contents. Structure quality scores were determined with CoreVESS. The pore system volumes were quantified by shrinkage analysis, and the water retention curves were used to determine the equivalent pore-size distribution. CoreVESS scores showed non-linear relationships with total and structural pore volumes. They correlated mainly to structural porosity volume, whereas plasma pores did not explain structure quality scores. As a result, the total porosity was less correlated to CoreVESS than structural porosity. The small-size (< 50-100 mu m equivalent diameter) structural pore volume showed the higher correlation to structure quality score. The small-size structural pore volume was mostly correlated with the SOC:clay ratio and, to a lesser extent, with SOC, highlighting the link between soil structure quality and clay-SOC complexation in these soils. Soils with SOC:clay ratios above 0.1 showed significantly larger volumes of small structural pores. Our findings underline the functional importance of these small-size structural pores, which are also accounting for air-water equilibrium close to field capacity, and were pointed out for their role as soil biota habitat. Their tight relationship with SOC suggests a good stability upon stresses and slow changes over time. In contrast, large structural pores, which are known to be sensitive to mechanical stress of soil fauna activity, were primarily influenced by carbonate content
Nitrogen fixation under declining Arctic sea ice
No full textWith climate change-induced sea ice decline in the Arctic Ocean, nitrogen is expected to become an increasingly important determinant of primary productivity. Nitrogen fixation is the conversion of molecular nitrogen to bioavailable ammonium by microorganisms called diazotrophs. Here, we report nitrogen fixation rates, diazotroph composition, and expression under different stages of declining sea ice in the Central Arctic Ocean (multiyear ice, five stations) and the Eurasian Arctic (marginal ice zone, seven stations). Nitrogen fixation in the Central Arctic Ocean was positively correlated with primary production, ranging from 0.4 +/- 0.1 to 2.5 +/- 0.87 nmol N L-1 d-1. Along two transects across the marginal ice zone, nitrogen fixation varied between days and ice regime from below detection up to 5.3 +/- 3.65 nmol N L-1 d-1 associated with an ice-edge phytoplankton bloom. We show nitrogen fixation in sea ice-covered waters of the Arctic Ocean and provide insight into present and active non-cyanobacterial diazotrophs in the region
In Vitro Effect of Elevated Ammonia and Urea Levels on Post-Thawed Bull Semen Sperm Characteristics
No full textElevated ammonia and urea, common byproducts of nitrogen metabolism, are increasingly found in dairy cows and may negatively impact reproductive function. However, their effects on bull sperm remain unclear. This study aimed to assess the impact of ammonia and urea at physiologically relevant concentrations on key sperm characteristics. Thawed bull semen was incubated under five treatment conditions: control (no added ammonia or urea), low urea (LU), high urea (HU), low ammonia (LA), and high ammonia (HA). Sperm motility and kinematics were assessed using Computer-Assisted Semen Analysis (CASA), and sperm viability, DNA integrity, mitochondrial membrane potential (MMP), and oxidative stress markers were evaluated using flow cytometry. HA significantly reduced MMP (p = 0.008) and several motility parameters, including progressive motility and velocity (VCL, VSL, ALH), compared to LA and control groups. A decrease in sperm viability was observed in the HA group compared to LA at the beginning of incubation. While HU reduced MMP (p = 0.002), sperm motility was not significantly affected compared to LU. No significant differences were found in DNA fragmentation or oxidative stress biomarkers between groups. These results highlight the impact of ammonia, specifically, on sperm mitochondrial function and motility, which are crucial for successful fertilization
Temporal Decoupling Between Total Organic Carbon and Iron in Lakes Linked to Interannual Changes in Precipitation
No full textWidespread increases in lake browning, which affects primary production, have been observed in northern lakes. While lake browning is attributed to increases in terrestrially derived total organic carbon (TOC) and total iron (Fe), Fe does not consistently correlate with increasing TOC over time. This temporal mismatch between TOC and Fe indicates that we still do not fully understand the causes of lake browning, especially in the context of gradually changing climatic conditions. In this study, we utilized Fennoscandian 30-year (1990-2020) time series data for 102 lakes to describe possible reasons for the temporal decoupling between TOC and Fe. Using Bayesian mixed-effects models and wavelet coherence analysis, we found evidence for differential responses of TOC and Fe concentrations to changes in precipitation, temperature, and sulfur deposition. While TOC appeared more sensitive to the effects of precipitation, temperature and sulfur deposition in individual lakes, Fe concentrations were impacted by complex interactions among these environmental variables. Although TOC and Fe increased in most lakes in response to increased temperature and precipitation, 41% of the lakes-typically with larger catchment-to-lake area ratios and shorter water residence times-exhibited a declining trend in Fe. This analysis encompasses lakes of both significant and non-significant changes over time. This decline in Fe was associated with short-timescale (2-4 years) increases in precipitation, leading to a temporal decoupling between Fe and TOC. Our findings suggest that Fe concentrations do not increase uniformly with rising temperatures and increased precipitation, especially in regions where sulfur deposition has declined due to atmospheric recovery policies
Exploring gender dynamics in climate-smart agriculture adoption: a study in semi-arid Dodoma, Tanzania
Get PDFIntroduction Climate change threatens agricultural production, particularly in developing countries, where agriculture supports over 2.5 billion people. Women, who comprise 43% of the agricultural labor force, are particularly vulnerable due to gender inequalities, especially in African societies. While Climate-Smart Agriculture (CSA) offers potential benefits to mitigate the adverse effects of climate change, its benefits are not evenly distributed, with a notable gender gap in adoption.Methods This study investigates how gender dynamics influence CSA adoption patterns in Tanzania's semi-arid Dodoma regions, using a mixed-methods approach. The study included a survey of 380 households and focus group discussions with 75 participants.Results The results reveal lower CSA adoption among female-headed households (51% non-adopters) compared to male-headed households (38% non-adopters). Probit and Poisson regression analyses identify several key determinants of adoption and adoption intensity, including marital status, livestock ownership, land access, and the availability of extension services. Female-headed households face unique barriers, such as smaller landholdings, labor constraints, and limited access to credit, training, and group membership. The study also highlights the absence of female extension workers in villages.Discussion The findings emphasize the need for targeted policy interventions to address these challenges and promote more equitable CSA adoption. These include implementing land reforms to ensure equitable land access for women, designing inclusive training programs that accommodate women's time constraints, and increasing the representation of female extension workers to enhance CSA knowledge dissemination among female farmers. Additionally, improving access to credit facilities for female farmers, strengthening social networks through farmer groups, and improving transport infrastructure to reduce logistical barriers are crucial to further supporting CSA adoption. These targeted interventions are essential for overcoming gender-specific barriers, ensuring that CSA benefits are more equitably distributed, and ultimately supporting sustainable agricultural development