The movement of dissolved organic matter (DOM) through forest soils is regulated by a suite of physicochemical and biological processes that retain, transform, and release DOM. While sorptive ...processes are known to limit DOM losses, there are still uncertainties about what regulates DOM composition. This study examined DOM dynamics in waters percolating through ex-situ soil cores from six diverse forest soils to determine if DOM leaching losses reflected dynamic exchange processes between fresh DOM inputs and soil surfaces or the continual stripping of surface-reactive compounds from recent DOM inputs. There was a net desorption of hydrophilic compounds into soil solutions after 10 cm soil depth that coincided with an increase in DOM biodegradability as solutions percolated to depth. There was also a limited net retention of dissolved organic nitrogen (DON) in surface soils. Taken together, these results support a dynamic exchange model of DOM dynamics where highly sorptive, hydrophobic compounds displace previously sorbed, N-rich hydrophilic compounds from soil surfaces. These soils also demonstrated fairly consistent leaching losses of dissolved organic carbon (DOC) and DON despite their variation in texture, hydraulic conductivity, and Fe and Al mineralogy, removing 72–85% of the DOC added by 50 cm depth. The strong sorption capacity of these soils may be one reason for the fairly uniform DOM chemistry leaching from these soil cores.
•Compared dynamic exchange and continual stripping models for DOM.•Results support dynamic exchange model.•DOM biodegradability increased with depth.•Limited net retention of DON, especially in surface soils.
The role of B cells in anti-tumour immunity is still debated and, accordingly, immunotherapies have focused on targeting T and natural killer cells to inhibit tumour growth
. Here, using ...high-throughput flow cytometry as well as bulk and single-cell RNA-sequencing and B-cell-receptor-sequencing analysis of B cells temporally during B16F10 melanoma growth, we identified a subset of B cells that expands specifically in the draining lymph node over time in tumour-bearing mice. The expanding B cell subset expresses the cell surface molecule T cell immunoglobulin and mucin domain 1 (TIM-1, encoded by Havcr1) and a unique transcriptional signature, including multiple co-inhibitory molecules such as PD-1, TIM-3, TIGIT and LAG-3. Although conditional deletion of these co-inhibitory molecules on B cells had little or no effect on tumour burden, selective deletion of Havcr1 in B cells both substantially inhibited tumour growth and enhanced effector T cell responses. Loss of TIM-1 enhanced the type 1 interferon response in B cells, which augmented B cell activation and increased antigen presentation and co-stimulation, resulting in increased expansion of tumour-specific effector T cells. Our results demonstrate that manipulation of TIM-1-expressing B cells enables engagement of the second arm of adaptive immunity to promote anti-tumour immunity and inhibit tumour growth.
Free amino acids (FAAs) in soil solution are increasingly recognized as a potentially important source of nitrogen (N) for plants, yet we are just beginning to understand the behavior of FAAs in ...soil. I investigated the effects of amino-acid chemistry and soil properties on mineralization, microbial assimilation and sorption of amino-acid N in soils from three ecosystems representing the two endpoints and mid point of a temperate forest fertility gradient ranging from low mineral N availability/high FAA oak forests to high mineral N availability/low FAA maple-basswood forests. Soils were amended with six
15N-labeled amino-acid substrates that ranged widely in chemical properties, including molecular weight, C:N ratio, average net charge, hydrophobicity, and polarity: Arginine (Arg), Glutamine (Gln), Glutamate (Glu), Serine (Ser), Glycine (Gly) and Leucine (Leu). Mineralization of amino-acid N accounted for 7–45% (18% avg.) of the added label and was most strongly affected by soil characteristics, with mineralization increasing with increasing soil fertility. Mineralization of amino-acid N was unrelated to amino-acid C:N ratio, rather, I observed greater N mineralization from polar FAAs compared to non-polar ones. Assimilation of amino-acid N into microbial biomass accounted for 6–48% (29% avg.) of the added label, and was poorly predicted by either intrinsic amino-acid properties or soil properties, but instead appeared to be explicable in terms of compound-specific demand by soil micoorganisms. Sorption of amino-acid N to soil solids accounted for 4–15% (7% avg.) of the added label and was largely controlled by charge characteristics of individual amino acids. The fact that both positively- and negatively-charged amino acids were more strongly sorbed than neutral ones suggests that cation and anion exchange sites are an important factor controlling sorption of FAAs in these acid forest soils. Together, the findings from this study suggest that there may be important differences in the behavior of free amino acids in sandy, acidic forest soils compared to generalizations drawn from finer-textured grassland soils, which, in turn, might affect the availability of some FAAs in soil solution.
Background and Aims
Patients with cirrhosis are at increased risk of postoperative mortality. Currently available tools to predict postoperative risk are suboptimally calibrated and do not account ...for surgery type. Our objective was to use population‐level data to derive and internally validate cirrhosis surgical risk models.
Approach and Results
We conducted a retrospective cohort study using data from the Veterans Outcomes and Costs Associated with Liver Disease (VOCAL) cohort, which contains granular data on patients with cirrhosis from 128 U.S. medical centers, merged with the Veterans Affairs Surgical Quality Improvement Program (VASQIP) to identify surgical procedures. We categorized surgeries as abdominal wall, vascular, abdominal, cardiac, chest, or orthopedic and used multivariable logistic regression to model 30‐, 90‐, and 180‐day postoperative mortality (VOCAL‐Penn models). We compared model discrimination and calibration of VOCAL‐Penn to the Mayo Risk Score (MRS), Model for End‐Stage Liver Disease (MELD), Model for End‐Stage Liver Disease‐Sodium MELD‐Na, and Child‐Turcotte‐Pugh (CTP) scores. We identified 4,712 surgical procedures in 3,785 patients with cirrhosis. The VOCAL‐Penn models were derived and internally validated with excellent discrimination (30‐day postoperative mortality C‐statistic = 0.859; 95% confidence interval CI, 0.809‐0.909). Predictors included age, preoperative albumin, platelet count, bilirubin, surgery category, emergency indication, fatty liver disease, American Society of Anesthesiologists classification, and obesity. Model performance was superior to MELD, MELD‐Na, CTP, and MRS at all time points (e.g., 30‐day postoperative mortality C‐statistic for MRS = 0.766; 95% CI, 0.676‐0.855) in terms of discrimination and calibration.
Conclusions
The VOCAL‐Penn models substantially improve postoperative mortality predictions in patients with cirrhosis. These models may be applied in practice to improve preoperative risk stratification and optimize patient selection for surgical procedures (www.vocalpennscore.com).
Perennial cellulosic feedstocks may have potential to reduce life-cycle greenhouse gas (GHG) emissions by offsetting fossil fuels. However, this potential depends on meeting a number of important ...criteria involving land cover change, including avoiding displacement of agricultural production, not reducing uncultivated natural lands that provide biodiversity habitat and other valued ecosystem services, and avoiding the carbon debt (the amount of time needed to repay the initial carbon loss) that accompanies displacing natural lands. It is unclear whether recent agricultural expansion in the United States competes with lands potentially suited for bioenergy feedstocks. Here, we evaluate how recent land cover change (2008-2013) has affected the availability of lands potentially suited for bioenergy feedstock production in the U.S. Lake States (Minnesota, Wisconsin, Michigan) and its impact on other natural ecosystems. The region is potentially well suited for a diversity of bioenergy production systems, both grasses and woody biomass, due to the widespread forest economy in the north and agricultural economy in the south. Based on remotely-sensed data, our results show that between 2008 and 2013, 836,000 ha of non-agricultural open lands were already converted to agricultural uses in the Lake States, a loss of nearly 37%. The greatest relative changes occurred in the southern half that includes some of the most diverse cultivable lands in the country. We use transition diagrams to reveal gross changes that can be obscured if only net change is considered. Our results indicate that expansion of row crops (corn, soybean) was responsible for the majority of open land loss. Even if recently lost open lands were brought into perennial feedstock production, there would a substantial carbon debt. This reduction in open land availability for biomass production is closing the window of opportunity to establish a sustainable cellulosic feedstock economy in the Lake States as mandated by current Federal policy, incurring a substantial GHG debt, and displacing a range of other natural ecosystems and their services.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Since the early 1980s, ca 1,550 hectares (3,800 ac) of high-density jack pine (Pinus banksiana) plantations have been established annually in northern Lower Michigan to serve as habitat for ...the federally endangered Kirtland’s warbler (KW; Setophaga kirtlandii). Because these plantations do not appear capable of producing merchantable sawlogs by their planned 50-year harvest age, we investigated the potential to implement reduced rotation lengths in these stands to produce biomass and/or pulpwood. We used space-for-time substitution to assess biomass and volume accrual over time, using our own locally derived allometric biomass equations. The predicted optimal rotation age for biomass was 20 years, and the predicted optimal rotation age for pulpwood volume was 28 years. We compared the total land area required for management under these rotation scenarios to continue establishing 1,550 hectares (3,800 ac) of KW habitat annually. Management on the current 50-year cycle requires ca 77,500 hectares (191,500 ac). Management for pulpwood would reduce this to ca 43,400 hectares (107,250 ac), and management for biomass would require ca 31,000 hectares (76,600 ac). Our results suggest that rotation lengths in these plantations could be substantially reduced, allowing for reductions in the total land area dedicated to warbler habitat, allowing for diversification of management at the landscape scale.
Whereas it is recognized that most trees have the capacity to take up free amino acids, it is unclear how important amino acid uptake is in situ. In-situ root uptake of isotopically-labeled ammonium, ...glycine and glutamine were compared between low-nitrogen (N)-availability and high-N-availability temperate forests. Comparable immediate 13C- and 15N-enrichment of fine roots indicated that short-term uptake of amino-acids by tree roots was similar between the two sites. Over the remainder of the experiment, recovery of amino-acid 15N in fine roots was greater, and recovery of 13C lower, in the high-N-availability site. Together with greater rates of conversion of amino-acid-derived 15N into inorganic forms, this indicates that a greater proportion of amino-acid-derived N was taken up after it was converted to inorganic forms by soil microorganisms in the high N availability site. Results from this study suggest that capacity for amino acid uptake by tree roots did not differ between high- and low-N availability sites, but differences in microbial mineralization drove strong differences in the availability of inorganic forms of N between sites.
•Amino acids were added to soils of temperate forests of contrasting N availability.•Plant roots at both sites were able to take up intact amino acids.•Mineralization of added amino-acid N was greater at the high N availability site.
Our understanding of nutrient limitations to jack pine (Pinus banksiana Lamb.) growth is lacking across the Lake States of the USA (Michigan, Wisconsin and Minnesota), where this species makes up an ...important forest cover type on nutrient poor sands. Currently this cover type is managed using whole-tree harvesting (WTH) across large areas of state and federal forestland, which raises concerns for long-term declines in soil fertility and future productivity. In this study, I carried out a factorial fertilization experiment to better understand potential nutrient limitations to jack pine growth on excessively drained sandy soils in northern Lower Michigan. Treatments were nitrogen (N), phosphorus (P) and base cations applied singly and in all factorial combinations. In addition, I constructed input-output nutrient budgets for jack pine management in northern Lower Michigan using existing data on atmospheric deposition, weathering and harvest nutrient removals. In no case did I observe an increase in tree growth rate to fertilization, instead I observed an overall decline in growth rates, and an increase in mortality rates, in trees fertilized with N. Nitrogen-induced imbalances of foliar N: potassium (K) were strongly correlated with decreased growth in N amended plots. Together with nutrient budget analysis, which indicated that harvest removals of K greatly exceed inputs over the planned rotation, this suggests that WTH may not be sustainable over multiple rotations. Furthermore, the impacts of WTH on ecosystem K status are likely to be exacerbated over time by anthropogenic N deposition.
Despite increasing recognition that free amino acids can be an important source of N for plant uptake, we have a poor understanding of environmental variation in the availability of amino-acid N in ...soils outside of arctic, alpine and boreal regions. I investigated patterns of amino-acid availability along a temperate forest fertility gradient ranging from low mineral N availability, oak-dominated forests to high mineral N availability, maple-basswood forests (5 sites). I measured standing pools of free amino acids, soluble peptides, ammonium and nitrate, rates of amino acid production (native proteolysis activity) and rates of consumption of a ¹⁵N-labeled leucine tracer. Standing pools of amino acid N decreased consistently along the fertility gradient from the low fertility black oak/white oak system to the high fertility sugar maple/basswood system, with a 25-fold difference in pool sizes between the poorest and richest sites. Standing pools of soluble peptides varied little among sites, instead, the relationship between free amino acids and peptides changed markedly across the gradient. At low fertility sites free amino acids were positively correlated with soluble peptides, whereas free amino acid pools were universally low at high fertility sites, regardless of peptide pools. Assays for native proteolysis activity indicated that amino acid production did not vary significantly among sites. Recovery of leucine tracer in inorganic (NH₄ ⁺ and NO₃ ⁻) pools and in residual soil organic matter both increased with increasing soil fertility; however, total consumption of the added amino-acid tracer did not vary among sites. Results from this study demonstrate that free amino acids can make an important contribution to potentially plant-available N pools in temperate forest soils, particularly at low fertility sites.
Dissolved organic nitrogen (DON) is a potentially significant vector of N loss from forest ecosystems that has been characterized as an “N leak.” Although the term “leak” suggests a lack of ...regulation, it is clear DON losses are a function of biological and physicochemical processes that influence its production and retention across the landscape. In this study, we investigated how soil processes that influence DON cycling impact ecosystem patterns of DON loss in five northern hardwood forests that spanned a gradient of N availability, tree species composition, and moisture–edaphic characteristics. We collected soil leachate from the forest floor and at 15 and 100 cm soil depths and related solution chemistry to its physical environment. We found that DON losses were a function of ecosystem N status and increased modestly with soil N stock. We also found a unimodal pattern of DOC/DON losses across the gradient driven by low DOC/DON in the lowest N availability stand, likely due to the interaction between strongly sorbing DOM inputs from C-rich, oak-derived leaf litter with highly sorptive soils. We suggest DOM losses from forests depend on interactions between soil solution input chemistry from the forest floor, which reflects changes in tree species composition across the landscape, and soil sorptive processes where organic compounds are dynamically exchanged between solid and dissolved phases. These results emphasize the need to understand how fine-scale processes can interact to shape ecosystem patterns of DOM loss.
PDF
