•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+.
Tidal freshwater forested wetlands (TFFW) provide critical ecosystem services including an essential habitat for a variety of wildlife species and significant carbon sinks for atmospheric carbon ...dioxide. However, large uncertainties remain concerning the impacts of climate change on the magnitude and variability of carbon fluxes and storage across a range of TFFW. In this study, we developed a process‐driven Tidal Freshwater Wetlands DeNitrification‐DeComposition model (TFW‐DNDC) that has integrated new features, such as soil salinity effects on plant productivity and soil organic matter decomposition to explore carbon dynamics in the TFFW in response to drought‐induced saltwater intrusion. Eight sites along the floodplains of the Waccamaw River (USA) and the Savannah River (USA) were selected to represent the TFFW transition from healthy to moderately and highly salt‐impacted forests, and eventually to oligohaline marshes. The TFW‐DNDC was calibrated and validated using field observed annual litterfall, stem growth, root growth, soil heterotrophic respiration, and soil organic carbon storage. Analyses indicate that plant productivity and soil carbon sequestration in TFFW could change substantially in response to increased soil pore water salinity and reduced soil water table due to drought, but in interactive ways dependent on the river simulated. These responses are variable due to nonlinear relationships between carbon cycling processes and environmental drivers. Plant productivity, plant respiration, soil organic carbon sequestration rate, and storage in the highly salt‐impacted forest sites decreased significantly under drought conditions compared with normal conditions. Considering the high likelihood of healthy and moderately salt‐impacted forests becoming highly salt‐impacted forests under future climate change and sea‐level rise, it is very likely that the TFFW will lose their capacity as carbon sinks without up‐slope migration.
Demand for mangrove forest resources has led to a steady decline in mangrove area over the past century. Land conversions in the form of agriculture, aquaculture and urbanization account for much of ...the deforestation of mangrove wetlands. However, natural processes at the transition zone between land and ocean can also rapidly change mangrove spread. In this study, we applied a robust field-based carbon inventory and new structural and temporal remote sensing techniques to quantify the magnitude and change of mangrove carbon stocks in major deltas across Africa and Asia. From 2000-2016, approximately 1.6% (12 270 ha) of the total mangrove area within these deltas disappeared, primarily through erosion and conversion to agriculture. However, the rapid expansion of mangroves in some regions during this same period resulted in new forests that were taller and more carbon-dense than the deforested areas. Because of the rapid vertical growth rates and horizontal expansion, new mangrove forests were able to offset the total carbon losses of 5 332 843 Mg C by 44%. Each hectare of new mangrove forest accounted for ∼84% to ∼160% of the aboveground carbon for each hectare of mangrove forest lost, regardless of the net change in mangrove area. Our study highlights the significance of the natural dynamics of erosion and sedimentation on carbon loss and sequestration potential for mangroves over time. Areas of naturally regenerating mangroves will have a much larger carbon sequestration potential if the rate of mangrove deforestation of taller forests is curbed.
Hyperhidrosis is a disease affecting around 5% of the western population. The qualitative field within hyperhidrosis among adolescents has been sparsely investigated. The aim of this study was to ...investigate the impact of adolescent hyperhidrosis patients' everyday life experiences on their hyperhidrosis treatment.
Qualitative, semi-structured interviews were carried out. In total, 10 adolescents, aged 12-18 years, participated in the study. Data were analyzed using a set of inseparable activities as described by Van Manen.
Three main themes were identified to represent common shared experiences across participants. The first theme was related to the impact of hyperhidrosis on the physical and psychological dimensions of life as it negatively affected both physical abilities and one's self-concept. Having hyperhidrosis was experienced as living a life in secrecy, characterized by individual routines for concealment and isolation in order to protect social identity.
The large negative impact of hyperhidrosis on adolescents is a strong justification for treatment of the disease. The substantial emotional distress suggests that treatment may need to include psychological support.
Mangroves are recognized for their valued ecosystem services to coastal areas, and the functional linkages between those services and ecosystem carbon stocks have been established. However, spatially ...explicit inventories are necessary to facilitate management and protection of mangroves, as well as providing a foundation for payment for ecosystem service programs such as REDD+. We conducted an inventory of carbon stocks in mangroves within Pongara National Park (PNP), Gabon using a stratified random sampling design based on forest canopy height derived from TanDEM-X remote sensing data. Ecosystem carbon pools, including aboveground and belowground biomass and necromass, and soil carbon to a depth of 2 m were assessed using measurements and samples from plots distributed among three canopy height classes within the park. There were two mangrove species within the inventory area in PNP, Rhizophora racemosa and R. harrisonii. R. harrisonii was predominant in the sparse, low-stature stands that dominated the west side of the park. In the east side of the park, both species occurred in tall-stature stands, with tree height often exceeding 30 m. Canopy height was an effective means to stratify the inventory area, as biomass was significantly different among the height classes. Despite those differences in aboveground biomass, the soil carbon density was not significantly different among height classes. Soils were the main component of the ecosystem carbon stock, accounting for over 84% of the total. The ecosystem carbon density ranged from 644 to 943 Mg C ha−1 among the three height classes. The ecosystem carbon stock within PNP is estimated to be 40,588 Gg C. The combination of pre-inventory information about stand conditions and their spatial distribution within the assessment area obtained from remote sensing data and a spatial decision support system were fundamental to implementing this relatively large-scale field inventory. This work exemplifies how mangrove carbon stocks can be quantified to augment national C reporting statistics, provide a baseline for projects involving monitoring, reporting and verification (i.e., MRV), and provide data on the forest composition and structure for sustainable management and conservation practices.
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•Remote sensing data greatly facilitates the inventory of mangrove carbon stocks•Canopy height classes are useful for stratifying the inventory area.•Soils contain the majority of ecosystem carbon stock•The forest included the tallest mangrove reported globally
Low salinity tidal wetlands (LSTW) are vulnerable to sea level rise and saltwater intrusion, thus their carbon sequestration capacity is threatened. However, the thresholds of rapid changes in carbon ...dynamics and biogeochemical processes in LSTW due to changes in hydroperiod and salinity regime remain unclear. In this study, we examined the effects of soil porewater salinity and water level on changes in net primary productivity (NPP) and greenhouse gas fluxes GHG: methane (CH
4
), nitrous oxide (N
2
O), and carbon dioxide (CO
2
) in LSTW using a wetland biogeochemistry model, Tidal Freshwater Wetland Denitrification and Decomposition (TFW-DNDC). TFW-DNDC was run with a series of combinations of soil salinities (0.1, 0.5, 1, 2, 4, 6, 8, 10 psu) and water levels relative to soil surface (-30, -20, -10, -5, 0, 5, 10, 20, 30 cm) for tidal forest and oligohaline marsh sites along the Savannah River and Waccamaw River, USA. Our results indicate that soil salinity and water level have antagonistic effects on CH
4
emissions and synergistic effects on CO
2
release. A soil salinity of 2-3 psu is the tipping point for the ecosystem level functional changes (e.g., NPP and CH
4
emissions) in LSTW. There are negative and nonlinear responses (NPP and CH
4
emission) to soil salinity. Furthermore, a soil water level from 10 cm below to 10 cm above the surface is a critical range in which biogeochemical processes respond strongly to hydrological changes. The presence of nonlinear tipping points in LSTW has large implications for understanding and predicting the effects of climate change on coastal wetland blue carbon storage and ecosystem dynamics.
Emissions of methane (CH4) and nitrous oxide (N2O) from soils to the atmosphere can offset the benefits of carbon sequestration for climate change mitigation. While past study has suggested that both ...CH4 and N2O emissions from tidal freshwater forested wetlands (TFFW) are generally low, the impacts of coastal droughts and drought‐induced saltwater intrusion on CH4 and N2O emissions remain unclear. In this study, a process‐driven biogeochemistry model, Tidal Freshwater Wetland DeNitrification‐DeComposition (TFW‐DNDC), was applied to examine the responses of CH4 and N2O emissions to episodic drought‐induced saltwater intrusion in TFFW along the Waccamaw River and Savannah River, USA. These sites encompass landscape gradients of both surface and porewater salinity as influenced by Atlantic Ocean tides superimposed on periodic droughts. Surprisingly, CH4 and N2O emission responsiveness to coastal droughts and drought‐induced saltwater intrusion varied greatly between river systems and among local geomorphologic settings. This reflected the complexity of wetland CH4 and N2O emissions and suggests that simple linkages to salinity may not always be relevant, as non‐linear relationships dominated our simulations. Along the Savannah River, N2O emissions in the moderate‐oligohaline tidal forest site tended to increase dramatically under the drought condition, while CH4 emission decreased. For the Waccamaw River, emissions of both CH4 and N2O in the moderate‐oligohaline tidal forest site tended to decrease under the drought condition, but the capacity of the moderate‐oligohaline tidal forest to serve as a carbon sink was substantially reduced due to significant declines in net primary productivity and soil organic carbon sequestration rates as salinity killed the dominant freshwater vegetation. These changes in fluxes of CH4 and N2O reflect crucial synergistic effects of soil salinity and water level on C and N dynamics in TFFW due to drought‐induced seawater intrusion.
This paper deals with the early hydration and structure development aspects of advanced cement-based systems that contain micro and nanoscale pozzolanic additives. We have used highly reactive ...colloidal silica produced by pyrogenic route (pyrogene oxides) as representative of nanoscale pozzolanic additives. Colloidal silica shortens the induction period to an extent that can be qualitatively correlated to the size of its primary silica particles and the specific surface area. Colloidal silica accelerates the early hydration reactions by providing large amounts of reactive siliceous surface, which serves as a site for the early C–S–H precipitation. Additionally the use of pozzolanic additives as cement replacement smoothes and reduces the heat of hydration evolved. The high performance specimens that contain microscale additives and especially those that contain both micro and nanoscale additives are characterised by very tight structure and are made up of finer structures in closer contact than the normal performance specimen without pozzolanic additive.
Coptotermes formosanus
, known in its native China as the ‘House White Ant’, was introduced to the southeast USA likely in the 1950s, where it is known as the Formosan subterranean termite. In the ...USA it is best known as a pest of buildings in urban areas, however
C. formosanus
also attacks live trees along streets and in urban parks, suggesting it may be able to invade forests in the USA. A survey of 113 forest patches around Charleston South Carolina and New Orleans Louisiana, where
C. formosanus
was first recorded, found that 37% and 52%, respectively, were infested. Resistograph measurement of internal hollows in tree trunks in forest patches infested with
C. formosanus
found infested sites contained more and larger hollows compared with non-infested sites. Compared with forest patches free of
C. formosanus,
infested patches had 32% more trees with hollows in Charleston, and 115% more in New Orleans. Similarly, compared with patches free of
C. formosanus
, hollows were 2–3 times larger in infested patches in Charleston, and 2–6 times larger in New Orleans.
Quercus
(oak) and
Acer
(maple) were the most damaged trees in Charleston, whereas
Carya
(bitternut hickory),
Taxodium
(bald cypress),
Nyssa
(blackgum) and
Liquidamber
(sweetgum) were the most damaged in New Orleans. As termite damaged trees are more likely to die, these differing damage levels between tree species suggests that
C. formosanus
may alter community structure in US forests.
The disjunct distribution of several Palearctic species has been widely shaped by the changes in climatic conditions during the Quaternary. The observed genetic differentiation or reproductive ...isolation between extant populations may be the outcome of their contemporary geographic separation or reproductive incompatibility due to differences in phenotypic traits which have evolved in isolated refugia. In the boreal ant Leptothorax acervorum, colonies from central and peripheral populations differ in social structure: colonies from Central and Northern Europe may contain several equally reproductive queens (facultative polygyny), while in colonies from peripheral populations in Spain only one the most dominant of several queens lays eggs (functional monogyny). By reconstructing the specie's evolutionary and demographic history in Southwestern Europe we examine whether variation in social organization is associated with restricted gene flow between the two social forms.
We show that multi-queen colonies from all so far known inner Iberian populations of L. acervorum are functionally monogynous, whereas multi-queen colonies from all Pyrenean populations are polygynous, like those from other previously studied areas in Europe. Our analyses revealed complex spatial-genetic structure, but no association between spatial-genetic structure and social organization in SW-Europe. The population in the western Pyrenees diverged most strongly from other Iberian populations. Moreover, microsatellite data suggest the occurrence of recent bottlenecks in Pyrenean and inner Iberian populations.
Our study shows a lack of reproductive isolation between the two social forms in SW-Europe. This in turn suggests that demographic and spatial patterns in genetic variation as well as the distribution of social phenotypes are better explained by co-variation with climatic, ecological, and historical factors. Moreover, we for the first time show the existence of substantial spatial-genetic structure in L. acervorum, suggesting the existence of multiple refugia in SW-Europe, including two extra-Mediterranean refugia in France. While gene flow among inner Iberian refugia may have been larger during the late glacial, extra-Mediterranean refugia in southern France may have contributed to the post-glacial recolonization of W-Europe.
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