Kes1, and other oxysterol-binding protein superfamily members, are involved in membrane and lipid trafficking through trans-Golgi network (TGN) and endosomal systems. We demonstrate that Kes1 ...represents a sterol-regulated antagonist of TGN/endosomal phosphatidylinositol-4-phosphate signaling. This regulation modulates TOR activation by amino acids and dampens gene expression driven by Gcn4, the primary transcriptional activator of the general amino acid control regulon. Kes1-mediated repression of Gcn4 transcription factor activity is characterized by nonproductive Gcn4 binding to its target sequences, involves TGN/endosome-derived sphingolipid signaling, and requires activity of the cyclin-dependent kinase 8 (CDK8) module of the enigmatic “large Mediator” complex. These data describe a pathway by which Kes1 integrates lipid metabolism with TORC1 signaling and nitrogen sensing.
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► Kes1 coordinates sterol-binding with PtdIns-4-P signaling on Golgi/endosomes ► Kes1 regulates sphingolipid signaling and activation of TOR by amino acids ► Sphingolipids dampen activity of the nutrient stress transcription factor Gcn4 ► CDK module of large Mediator is required for Gcn4 regulation by sphingolipids
Kes1 regulates endosomal trafficking, integrating lipid metabolism with nutrient sensing to modulate proliferation and maintain cellular homeostasis.
Mangroves are among the most carbon-rich terrestrial ecosystems, primarily attributable to the soil pool. There are substantial differences in soil carbon (C) and nitrogen (N) due to the disparities ...in geomorphic settings and ecological drivers, but this insight is drawn primarily from observational studies. An objective inventory of carbon stocks in mangroves of the Rufiji River Delta, Tanzania was conducted. Seventy-five soil cores were collected within a 12,164 ha inventory area, comprising the northern portion of the delta. Cores were collected from intact and dwarf mangroves, agricultural fields, and mudflats. The spatial mean soil organic carbon (SOC) density in mangroves was 16.35 ± 6.25 mg C cm
−3
. Mean SOC density in non-vegetated mudflats was 12.16 ± 4.57 mg C cm
−3
, demonstrating that mangroves develop on soils with a substantial soil C stock. However, long-established mangroves had had a higher C density (17.27 ± 5.87 mg C cm
−3
). Using a δ
13
C mixing model, the source of soil organic matter in mudflats was primarily marine, while long-established mangroves was predominantly mangrove. There were small differences in SOC among long-established mangrove sites in different geomorphic settings. The proportion of marine-sourced SOC increased with soil depth in mangroves. The SOC and nitrogen of agricultural sites resemble those of mudflats, suggesting those sites are developed from relatively young forests. The SOC and nitrogen density in dwarf mangrove sites were lower than others, perhaps reflecting past disturbances.
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•A stratified random sampling inventory was used to quantify the Zambezi mangrove C stock.•Mangrove canopy height estimates were used effectively as the basis for ...stratification.•Ecosystem C density ranged from 373.8 to 620.8MgCha−1.•Soil C was the largest C pool, accounting for 45–73% of the C in each stratum.•Precision of final stock estimate was within a 95% confidence interval equal to ±6% of the total.
Mangroves are well-known for their numerous ecosystem services, including storing a globally significant C pool. There is increasing interest in the inclusion of mangroves in national climate change mitigation and adaptation plans in developing nations as they become involved with incentive programs for climate change mitigation. The quality and precision of data required by these programs necessitates the use of an inventory approach that allows for quantification, rather than general characterization, of C stocks. In this study, we quantified the ecosystem C stock of the Zambezi River Delta mangroves utilizing a rigorous, yet operationally feasible approach. We applied a stratified random sampling inventory design, based on five forest canopy height classes, derived from Ice, Cloud, and Land Elevation Satellite/Geoscience Laser Altimeter System (ICE Sat/GLAS) and the Shuttle Radar Topography Mission (SRTM) data, and a Spatial Decision Support System to allocate inventory plots. Carbon content in above- and below-ground biomass pools in addition to soils to a depth of 200cm was measured. The average biomass C density for the height classes ranged from 99.2MgCha−1 to 341.3MgCha−1. Soil C density was the largest measured C pool, containing 274.6MgCha−1 to 314.1MgCha−1 and accounting for 45–73% of the height class ecosystem C densities, which ranged from 373.8MgCha−1 to 620.8MgCha−1. The ecosystem C density estimates for the five strata were weighted based on their spatial distribution across the landscape to yield a total C stock for the Zambezi River Delta mangroves of 1.4×107MgC. The error bounds from the 95% confidence interval are ±6% of our ecosystem C stock estimate, well within acceptable levels of uncertainty.
Microtopography plays an important role in various ecological, hydrologic, and biogeochemical processes. However, quantifying the characteristics of microtopography represents a data-intensive ...challenge. Over the last decade, high-resolution or close-range remote sensing data and techniques have emerged as powerful tools to quantify microtopography. Traditional field surveys were mostly limited to transects or small plots, using limited sets of observations but with the decrease in the cost of close-range remote sensing technologies and the increase in computing performance, the microtopography even in forested environments can be assessed. The main objective of this article is to provide a systematic framework for microtopographic studies using close-range remote sensing technologies. This is achieved by reviewing the application of close-range remote sensing to capture microtopography and develop microtopographic models in natural ecosystems. Specifically, to achieve the main objectives, we focus on addressing the following questions: (1) What terrain attributes represent microtopography in natural ecosystems? (2) What spatial resolution of terrain attributes is needed to represent the microtopography? (3) What methodologies have been adopted to collect data at selected resolutions? (4) How to assess microtopography? Current research, challenges, and applicability of close-range remote sensing techniques in different terrains are analyzed with an eye to enhancing the use of these new technologies. We highlight the importance of using a high-resolution DEM (less than 1 m2 spatial resolution) to delineate microtopography. Such a high-resolution DEM can be generated using close-range remote sensing techniques. We also illustrate the need to move beyond elevation and include terrain attributes, such as slope, aspect, terrain wetness index, ruggedness, flow accumulation, and flow path, and assess their role in influencing biogeochemical processes such as greenhouse gas emissions, species distribution, and biodiversity. To assess microtopography in terms of physical characteristics, several methods can be adopted, such as threshold-based classification, mechanistically-based delineation, and machine learning-based delineation of microtopography. The microtopographic features can be analyzed based on physical characteristics such as area, volume, depth, and perimeter, or by using landscape metrics to compare the classified microtopographic features. Remote sensing techniques, when used in conjunction with field experiments/data, provide new avenues for researchers in understanding ecological functions such as biodiversity and species distribution, hydrological processes, greenhouse gas emissions, and the environmental factors that influence those parameters. To our knowledge, this article provides a comprehensive and detailed review of microtopography data acquisition and quantification for natural ecosystem studies.
•Successful combination of foam concrete and lightweight aggregates.•Lightweight aggregate concrete with open structure and porous matrix.•Nanoscale view on the texture of the lightweight ...aggregates.•Improved ratio between compressive strength and dry density/thermal conductivity.•Reduction of drying shrinkage due to the aggregates of almost 80%.
In this study the combination of foam concrete and lightweight aggregates was investigated in order to develop a lightweight aggregate concrete with open structure and porous matrix (LACPM). For this purpose the recipe of a foam concrete was combined with the following lightweight aggregates: pumice, expanded glass, foam glass, expanded clay, and expanded perlite. The successfully produced concretes showed a homogenous microscopic structure and arrangement of the aggregates. A nanoscale view on the texture of the aggregates helped to understand the different embedding in the foamed cement paste matrix and their interaction at the interface. The best embedding was shown by pumice, expanded perlite and expanded clay. The ratio between compressive strength and dry density as well as the ratio between compressive strength and thermal conductivity has been improved respectively. Compared to conventional foam concrete an improvement of the compressive strength by almost 40 % was measured. The same applied for the drying shrinkage, the change in length was reduced by the addition of the aggregates to almost 80 %.
Quantitative X-ray diffraction (QXRD) and thermogravimetry (TG) methods are used to determine the phase development up to 28 days of hydration in normal and ultra high performance cementitious ...systems (UHPC) that do not contain aggregate. The phase development in ultra high performance cementitious formulation is quantitatively and kinetically different from that in normal concrete formulation. This is related to the different components employed and their associated reactions. For both formulations the most remarkable changes of the phase contents are recorded between the first and second hydration day and up to the seventh day. After the seventh day less phase content changes are measured. Because of the non sufficient water amount for hydration, considerable amount of cement remains non hydrated in the UHPC formulation. The portlandite content, which is present in the UHPC specimen, gives evidence for non complete pozzolanic reactions even after 28 days of hydration, whereas the absence of calcite in the UHPC specimen indicates an insignificant carbonation in this specimen.
Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global climate change. Predictions of C dynamics require us to consider interactions among ...many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model, Wetland‐DNDC, for C dynamics and methane (CH4) emissions in wetland ecosystems. The general structure of Wetland‐DNDC was adopted from PnET‐N‐DNDC, a process‐oriented biogeochemical model that simulates C and N dynamics in upland forest ecosystems. Several new functions and algorithms were developed for Wetland‐DNDC to capture the unique features of wetland ecosystems, such as water table dynamics, growth of mosses and herbaceous plants, and soil biogeochemical processes under anaerobic conditions. The model has been validated against various observations from three wetland sites in Northern America. The validation results are in agreement with the measurements of water table dynamics, soil temperature, CH4 fluxes, net ecosystem productivity (NEP), and annual C budgets. Sensitivity analysis indicates that the most critical input factors for C dynamics in the wetland ecosystems are air temperature, water outflow parameters, initial soil C content, and plant photosynthesis capacity. NEP and CH4 emissions are sensitive to many of the tested input variables. By integrating the primary drivers of climate, hydrology, soil and vegetation, the Wetland‐DNDC model is capable of predicting C biogeochemical cycles in wetland ecosystems.
The behavioral traits that shape the structure of animal societies vary considerably among species but appear to be less flexible within species or at least within populations. Populations of the ant ...Leptothorax acervorum differ in how queens interact with other queens. Nestmate queens from extended, homogeneous habitats tolerate each other and contribute quite equally to the offspring of the colony (polygyny: low reproductive skew). In contrast, nestmate queens from patchy habitats establish social hierarchies by biting and antennal boxing, and eventually only the top-ranking queen of the colony lays eggs (functional monogyny: high reproductive skew). Here we investigate whether queen-queen behavior is fixed within populations or whether aggression and high skew can be elicited by manipulation of socio-environmental factors in colonies from low skew populations. An increase of queen/worker ratio and to a lesser extent food limitation elicited queen-queen antagonism in polygynous colonies from Nürnberger Reichswald similar to that underlying social and reproductive hierarchies in high-skew populations from Spain, Japan, and Alaska. In manipulated colonies, queens differed more in ovarian status than in control colonies. This indicates that queens are in principle capable of adapting the magnitude of reproductive skew to environmental changes in behavioral rather than evolutionary time.
Coarse woody debris (CWD) is an important component in forests, hosting a variety of organisms that have critical roles in nutrient cycling and carbon (C) storage. We developed a process-based model ...using literature, field observations, and expert knowledge to assess woody debris decomposition in forests and the movement of wood C into the soil and atmosphere. The sensitivity analysis was conducted against the primary ecological drivers (wood properties and ambient conditions) used as model inputs. The analysis used eighty-nine climate datasets from North America, from tropical (14.2° N) to boreal (65.0° N) zones, with large ranges in annual mean temperature (26.5°C in tropical to -11.8°C in boreal), annual precipitation (6,143 to 181 mm), annual snowfall (0 to 612 kg m.sup.-2 ), and altitude (3 to 2,824 m above mean see level). The sensitivity analysis showed that CWD decomposition was strongly affected by climate, geographical location and altitude, which together regulate the activity of both microbial and invertebrate wood-decomposers. CWD decomposition rate increased with increments in temperature and precipitation, but decreased with increases in latitude and altitude. CWD decomposition was also sensitive to wood size, density, position (standing vs downed), and tree species. The sensitivity analysis showed that fungi are the most important decomposers of woody debris, accounting for over 50% mass loss in nearly all climatic zones in North America. The model includes invertebrate decomposers, focusing mostly on termites, which can have an important role in CWD decomposition in tropical and some subtropical regions. The role of termites in woody debris decomposition varied widely, between 0 and 40%, from temperate areas to tropical regions. Woody debris decomposition rates simulated for eighty-nine locations in North America were within the published range of woody debris decomposition rates for regions in northern hemisphere from 1.6° N to 68.3° N and in Australia.
•Thirty-three years after stem only (SOH) and whole-tree (WTH).•No significant difference in tree biomass (as was the case 15years after harvest).•Greater forest floor mass and nutrient content in ...WTH (no difference at 15years).•Large increases in soil N in both treatments at 15years still evident.•Greater soil Ca2+ and Mg2+ in SOH at 15years still evident.
Vegetation, forest floor, and soils were resampled at a mixed oak site in eastern Tennessee that had been subjected to stem only (SOH), whole-tree harvest (WTH), and no harvest (REF) 33years previously. Although differences between harvest treatments were not statistically significant (P<0.05), average diameter, height, basal area and biomass were 8–18% lower in the WTH than in the SOH treatment 33years after harvest whereas they differed by 2% 15years after harvest. In contrast to results 15years post-harvest, total forest floor mass and nutrient contents were twofold greater in the WTH than in the SOH treatment at 33years post-harvest, due largely to differences in Oa horizon mass. Soil total C concentrations increased significantly (P<0.05) over the first 15years post-harvest in both harvest treatments. Decreases in soil C between 15 and 33years post-harvest were not statistically significant. Soil total N increased significantly in both harvest treatments over the first 15years post-harvest. Consistent decreases in soil total N occurred in the WTH treatment between years 15 and 33 post-harvest that bordered on statistical significance whereas total N was stable over that time period in the SOH treatment. The increases and decreases in soil N content cannot be explained by any known processes of N inputs or outputs. Harvest treatment effects on both Ca2+ and Mg2+ observed at 15years post-harvest are still observable and significant at 33years post-harvest, although decreases between 15 and 33years were found. Treatment effects and changes in soil exchangeable Ca2+ and Mg2+ are consistent with known inputs from decomposing logging residues, inputs from atmospheric deposition, and increments in forest floor and vegetation. No treatment effects were found for soil extractable P, but steady decreases over time were found. No treatment or time effects were found for soil exchangeable K+.
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