Water Tree Research Articles

Invasive plant species interact with drought to shift key functions and families in the native rhizosphere

Background and aimsInteractions between species invasions and climate change have the potential to drive changes in plant communities more than either factor alone. One pathway through which these effects can occur is via changes to the rhizosphere microbial community. Invasive plants can alter these microbial communities affecting natives’ abilities to compete with invaders. At the same time, climate change is leading to more frequent extreme wet and dry events. Understanding the response of plant communities to these combined global change drivers requires a comprehensive approach that assesses the relationship between plant competition and belowground rhizosphere microbial community responses.MethodsHere we use a field experiment in a California grassland with a set of six native annual forbs (i.e., wildflowers) and three invasive annual grasses to test how competition with invasive plants alters both identity and function in the native rhizosphere microbiome, and whether competition between these groups interacts with rainfall to amplify or ameliorate microbial shifts.ResultsMetagenomics of rhizosphere communities revealed that drought combined with competition from invaders altered a higher number of functions and families in the native rhizosphere compared to invasive competition alone or drought alone. Watering combined with invasion led to fewer shifts.ConclusionThis suggests invasion-driven shifts in the microbial community may be involved in weakening natives’ ability to cope with climate change, especially drought. Understanding the role of the microbial community under invasion and climate change may be critical to mitigating the negative effects of these interacting global change drivers on native communities.Graphical abstractUnderstanding plant community response to global change drivers requires a comprehensive approach that assesses the relationship between plant competition and belowground rhizosphere microbial community responses. (a) In this work, we use a field experiment in a California grassland with a set of native forbs (purple) and invasive grasses (teal) to assess the combined effects of competition and water availability (drought, control, watered) on the rhizosphere microbiome. (b) Drought combined with competition from invaders altered the relative abundance of 36 functions (white) and 22 microbial families (blue) in the native rhizosphere compared to the effects of competition (3 functions, 16 families) or drought alone on natives (not shown: 5 functions, 0 families). (c) Additionally, regardless of watering treatment, invasive grasses sourced more of the taxonomic community in native-invasive mixes and this was exacerbated during drought. Overall, these results suggest invasion-driven shifts in the microbiome may be involved in weakening natives’ ability to cope with climate change, especially drought.

Socio-Economics Importance and Its Determinant Factors of Wetlands in Eastern Ethiopia

Wetland in Ethiopia provides various socio-economic benefits for the local community and for the people who live around the ecosystem. Despite this, the wetland in Ethiopia provides various benefits to the local community, it is under severe pressure and degradation from natural causes and human activity. The present study aims to assess the socio-economic importance of the wetland that existed in the East Harerghe zone. Both primary and secondary data were employed to answer the study objective. Accordingly, a total of 220 respondents were selected to administer the questionnaire. SPSS version 20 was used for data analysis and a multiple regression model was used to see the relationship between dependent and independent variables. The income generated varies in two lakes, Lake Langie is 56,196.8 birr, whereas the mean annual income in Lake Adele is 54,662.6 birr. The determining factor for the income generated from the wetland is the respondent land size and the distance between the wetland and farmland. Among respondents, 53.2% of the respondents perceived that the lakes are highly degraded followed by less degraded 33.9% and 12.6% in good condition. Agricultural expansions are indicated as the major triggering factor for the degradation of wetlands followed by population pressure, sedimentation, deforestation, overgrazing, and poor law enforcement and regulation respectively. Most respondents are interested in participating in conservation activity and the recommended activity to tackle this degradation is soil and water conservation and tree planting activity.

Induced Drought Stress Response of European Beech Seedlings Treated with Hydrogel and Ectomycorrhizal Inoculum

Bareroot European beech (Fagus sylvatica L.) seedlings are frequently used in reforestation programs in Central Europe. However, beech outplanting is often unsuccessful due to drought stress. In this study, the effects of a simulated water deficit and of a hydrogel and ectomycorrhizal fungi (EMF) application were estimated on the development of 1 + 1 beech seedlings. The roots of 1-year-old bareroot seedlings were treated with the additives at the time of transplanting to pots in spring and then exposed to the whole growing season under different watering regimes: (i) full watering (FW; volumetric water content 70%), (ii) reduced watering (RW; 40%), (iii) periodic watering (PW; substrate rewetted to 70% after drying), and (iv) no watering (NW). Almost all FW seedlings survived the whole growing season, whereas all NW seedlings died after 17 weeks of desiccation. The survival and growth of FW and NW seedlings were significantly higher and lower, respectively, than those under both PW and RW treatments. The additives significantly increased survival in RW seedlings only but had no effect on growth. A promoting effect of FW on the chlorophyll a fluorescence parameters was found. The number and EMF colonization of the short roots were significantly lower in FW seedlings compared to the other watering treatments. The additives did not affect these parameters. The occurrence of neither treatment-specific EMF root morphotype nor fungi applied in the inoculum and traced by molecular analysis indicated the formation of ectomycorrhizas with native EMF in all treatments. The seedlings in the water-deficient treatments exhibited higher foliar nutrient concentrations than FW seedlings. The additives increased the concentration of nutrients in PW and phosphorus in NW seedlings. The results suggest the significant effect of the water supply, but a weaker effect of the additives tested on beech seedling development under experimental conditions.

Stormwater Tree Pits for Decentralized Retention of Heavy Rainfall

Stormwater tree pits with storage elements enable the irrigation of urban trees and can potentially act as decentralized rainwater retention basins. This paper mainly focuses on analyzing this potential. Field tests were conducted to investigate the irrigation behavior and the storage effect of a storm water tree pit system using Perl hoses as irrigation elements over a period of two years. The rainfall, storage volumes, and soil moisture within the employed planting pit were measured. With the help of system modeling, the retention ability of the storm water tree pit system was analyzed. The available storage volume was sufficient to irrigate trees for several days. During the measurement period, about 15% of the inflowing rainwater was fed to the root zone of the tree. With practical storage volumes of 200 to 300 m3/ha, a remarkable amount of water from heavy rainfall could be completely stored, thus significantly reducing the risk of flooding. The retention effect and irrigation behavior largely depend on the soil conditions and the technical possibilities of the equipment supplying the root area (in this case, Perl hoses). Further investigations are required to determine the influence on the growth conditions of trees and optimize of the system for discharge into the root zone.

Effect of Interface Defects on the Harmonic Currents in Distribution Cable Accessories under Damp Conditions

Dampness is one of the most important factors leading to the degradation of the insulation performance of cable accessories; it may easily lead to interface defects of composite insulation. In this paper, an electromagnetic field defect model of the cable composite insulation interface is established, and the effects of the defect degree and the defect type on the magnetic flux and the harmonic current are studied. The results show that the magnetic field is uniformly distributed with a decreasing trend when the cable is in good condition, and the grounding current has no obvious harmonic component. For different defects, the magnetic field changes at the defect location are notably different; for water droplets and the water film, the magnetic field distortion is obvious at the location of the defect and sheath, and for water tree defects, the distortion of the magnetic field is significant. In addition, the degree of distortion caused by the same defect at different positions is also different, and the magnetic field contrast is not obvious at different degrees of moisture exposure. The distortion of the grounding current caused by the water tree is higher than that of the water droplet and the water film, and the characteristics of the harmonic components of the grounding current caused by different defects have obvious distinctions. The type of cable defect can be judged by the proportion of harmonic components. This work can be used as a reference for the assessment of the cable insulation defect status.

Comparison of species composition and community characteristics of Quercus forests on south and north slopes of Taibai Mountain, China.

We examined species composition, community characteristics, diversity, and community similarity of five Quercus communities composed of three Quercus species (Q. variabilis, Q. aliena var. acutiserrata, Q. wutaishanica) on the altitudinal gradient on the south and north slopes of Taibai Mountain. The results showed that there was an altitudinal transition pattern from Q. variabilis pure forest to Q. variabilis-Q. aliena var. acutiserrata mixed forest, Q. aliena var. acutiserrata pure forest, Q. aliena var. acutiserrata-Q. wutaishanica mixed forest and Q. wutaishanica pure forest on the south and north slopes of Taibai Mountain. The main companion species of Quercus community on the north slope were Pinus armandii, Castanea seguinii, and Sorbus alnifolia, and were Pinus tabuliformis, C. seguinii, Carpinus cordata, and Q. spinosa on the south slope. Species richness, woody plant density, and Quercus species dominance on the north slope of Taibai Mountain were higher than those on the south slope. α diversity of tree layer in Quercus community on the south and north slopes of Taibai Mountain increased first, then decreased and then increased with altitude. α diversity of tree layer was higher in mixed forests than pure forests. α diversity of shrub layer was higher than that of tree layer and herb layer in Quercus community on south and north slopes. β diversity fluctuated greatly along the altitudinal gradient on the south and north slopes, indicating that species composition changed greatly with altitude. Results of redundancy analysis showed that mean warmest month temperature, altitude and tree height accounted for 79.0% of the community diversity on the north slope, and that soil water content, tree height, canopy density and mean annual temperature accounted for 79.6% of the community diversity on the south slope. Overall, Quercus dominance was higher on the north slope of Taibai Mountain, and the substitution distribution pattern of Quercus species was clearer than that on the south slope. Environmental factors related to temperature and precipitation jointly affected α diversity of Quercus communities.

Restoring South African subtropical succulent thicket using Portulacaria afra: exploring the rooting window hypothesis.

Drought prone, arid and semi-arid ecosystems are challenging to restore once degraded due to low levels of natural recruitment and survival of reintroduced plants. This is evident in the restoration of degraded succulent thicket habitats in the Albany Subtropical Thicket Biome located in South Africa. The current restoration practice for this ecosystem focuses predominantly on reintroducing Portulacaria afra L. Jacq., which is naturally dominant in terms of cover and biomass, but largely absent in regions degraded by domestic livestock. This has been achieved by planting unrooted cuttings with limited consideration of soil water availability in a drought-prone ecosystem. This study tests the effects of the timing of water availability after planting on the root development of P. afra cuttings. Cuttings were harvested from seven individual plants and grown in a glasshouse setting. Eighty four cuttings were taken from each individual, twelve for each of the seven watering treatments per individual plant. The treatments represented a time-staggered initial watering after planting, including: on the day of planting, 4 days, 7 days, 14 days, 21 days, and 28 days after planting. After 32 days, all treatments were watered on a bi-weekly basis for two weeks; a control treatment with no watering throughout the experiment was included. The proportion of rooted cuttings per treatment and dry root mass were determined at the end of the experimental period (day 42). The early onset of watering was associated with a higher percentage of rooting (X2(5) = 11.352, p=0.045) and had a weak, but non-significant, impact on the final dry root mass (F5,36 = 2.109, p=0.0631). Importantly, no clear rooting window within 28 days was detected as the majority of cuttings exhibited root development (greater than 50% of cuttings rooted for each individual parent-plant); this suggests that watering at the time of planting P. afra cuttings in-field for restoration may not be necessary. An unexpected, but important, result was that parent-plant identity had a strong interaction with the accumulation of root mass (F36,460 = 5.026, p<0.001; LR7 = 122.99, p<0.001). The control treatment, which had no water throughout the experiment, had no root development. These findings suggest that water availability is required for the onset of rooting in P. afra cutting. However, the duration of the experiment was insufficient to detect the point at which P. afra cuttings could no longer initiate rooting once exposed to soil moisture, and thus no rooting window could be defined. Despite harvesting material from the same source population, parent-plant identity strongly impacted root development. Further work is required to characterise the rooting window, and to explore the effect of parent-plant condition on in-field and experimental restoration results; we urge that experiments using P. afra closely track the parent-source at the individual level as this may be a factor that may have a major impact on results.

Ruppert's delaunay triangulation refinement scheme for optimal RSUs placement in vehicle to infrastructure communication network

Road Side Units (RSUs) are the essential component of vehicular communication for the objective of improving safety and mobility in the road transportation. RSUs are generally deployed at the roadside and more specifically at the intersections in order to collect traffic information from the vehicles and disseminate alarms and messages in emergency situations to the neighborhood vehicles cooperating with the network. However, the development of a predominant RSUs placement algorithm for ensuring competent communication in VANETs is a challenging issue due to the hindrance of obstacles like water bodies, trees and buildings. In this paper, Ruppert's Delaunay Triangulation Refinement Scheme (RDTRS) for optimal RSUs placement is proposed for accurately estimating the optimal number of RSUs that has the possibility of enhancing the area of coverage during data communication. This RDTRS is proposed by considering the maximum number of factors such as global coverage, intersection popularity, vehicle density and obstacles present in the map for optimal RSUs placement, which is considered as the core improvement over the existing RSUs optimal placement strategies. It is contributed for deploying requisite RSUs with essential transmission range for maximal coverage in the convex map such that each position of the map could be effectively covered by at least one RSU in the presence of obstacles. The simulation experiments of the proposed RDTRS are conducted with complex road traffic environments. The results of this proposed RDTRS confirmed its predominance in reducing the end-to-end delay by 21.32%, packet loss by 9.38% with improved packet delivery rate of 10.68%, compared to the benchmarked schemes.

Tree diversity, growth status, and spatial distribution affected soil N availability and N2O efflux: Interaction with soil physiochemical properties

Soil nitrogen (N) is an essential nutrient for tree growth, and excessive N is a source of pollution. This paper aims to define the effects of plant diversity and forest structure on various aspects of soil N cycling. Herein, we collected soils from 720 plots to measure total N content (TN), alkali-hydrolyzed N (AN), nitrate N (NO3−-N), ammonium N (NH4+-N) in a 7.2 ha experimental forest in northeast China. Four plant diversity indices, seven structural metrics, four soil properties, and in situ N2O efflux were also measured. We found that: 1) high tree diversity had 1.3–1.4-fold NO3−-N, 1.1-fold NH4+-N, and 1.5–1.8-fold N2O efflux (p < 0.05). 2) Tree growth decreased soil TN, AN, and NO3−-N by more than 13%, and tree mixing and un-uniform distribution increased TN, AN, and NH4+-N by 11–22%. 3) Soil organic carbon (SOC) explained 34.3% of the N variations, followed by soil water content (1.5%), tree diameter (1.5%) and pH (1%), and soil bulk density (0.5%). SOC had the most robust linear relations to TN (R2 = 0.59) and AN (R2 = 0.5). 4) The partial least squares path model revealed that the tree diversity directly increased NO3−-N, NH4+-N, and N2O efflux, and they were strengthened indirectly from soil properties by 1%–4%. The effects of tree size-density (−0.24) and spatial structure (0.16) were mainly achieved via their soil interaction and thus indirectly decreased NH4+-N, AN, and TN. Overall, high tree diversity forests improved soil N availability and N2O efflux, and un-uniform spatial tree assemblages could partially balance the soil N consumed by tree growth. Our data support soil N management in high northern hemisphere temperate forests from tree diversity and forest structural regulations.

Response of Spontaneous Plant Communities to Sedum mexicanum Cover and Water Availability in Green Roof Microcosms

Lack of maintenance can lead to ‘weedy’ spontaneous vegetation on green roofs. Aspects of green roof design, including substrate depth and roof height, have been shown to influence the composition of spontaneous vegetation. In drier climates, Sedum species are often planted on shallow substrate ‘extensive’ green roofs and irrigated during summer to maintain cover. However, the response of spontaneous vegetation to Sedum cover and water availability is unclear. Understanding this relationship could help minimise maintenance and maintain Sedum vegetation cover. We hypothesised that increasing Sedum (Sedum mexicanum) cover and reduced water availability would reduce the abundance, biomass, species and functional richness, and the community weighted mean specific leaf area (SLA; CWM by abundance) of spontaneous plant communities. We conducted a 10-month experiment in green roof microcosms planted with S. mexicanum (0%, 25%, 50%, 75% and 100% total cover), subjected to a well-watered or water-deficit irrigation treatment, and sown with a mix of 14 plant species that commonly occur as spontaneous on green roofs. We measured spontaneous species abundance, community biomass, and functional traits (specific leaf area, leaf dry matter content, and relative growth rate), and calculated species and functional richness. Increasing S. mexicanum cover reduced spontaneous species abundance and species and functional richness but did not affect community biomass. Species richness was affected by the interaction of S. mexicanum cover and watering treatment and was greatest in well-watered microcosms with 0% S. mexicanum cover. Increased water availability increased spontaneous plant biomass but did not affect functional richness. The SLA of spontaneous communities was affected by the interaction of S. mexicanum cover and watering and was significantly greater in well-watered treatments where S. mexicanum cover was &lt;100%. Therefore, maximising Sedum cover and limiting water availability on green roofs will likely limit the abundance, biomass, and diversity of spontaneous vegetation. Conversely, for green roofs where substrate is left to be naturally colonised, increasing water availability could encourage establishment and increase functional richness of spontaneous vegetation.

Deep roots mitigate drought impacts on tropical trees despite limited quantitative contribution to transpiration

Deep rooting is considered a central drought-mitigation trait with vast impact on ecosystem water cycling. Despite its importance, little is known about the overall quantitative water use via deep roots and dynamic shifts of water uptake depths with changing ambient conditions. Knowledge is especially sparse for tropical trees. Therefore, we conducted a drought, deep soil water labeling and re-wetting experiment at Biosphere 2 Tropical Rainforest. We used in situ methods to determine water stable isotope values in soil and tree water in high temporal resolution. Complemented by soil and stem water content and sap flow measurements we determined percentages and quantities of deep-water in total root water uptake dynamics of different tree species. All canopy trees had access to deep-water (max. uptake depth 3.3 m), with contributions to transpiration ranging between 21 % and 90 % during drought, when surface soil water availability was limited. Our results suggest that deep soil is an essential water source for tropical trees that delays potentially detrimental drops in plant water potentials and stem water content when surface soil water is limited and could hence mitigate the impacts of increasing drought occurrence and intensity as a consequence of climate change. Quantitatively, however, the amount of deep-water uptake was low due to the trees' reduction of sap flow during drought. Total water uptake largely followed surface soil water availability and trees switched back their uptake depth dynamically, from deep to shallow soils, following rainfall. Total transpiration fluxes were hence largely driven by precipitation input.

Modelling Electro-Mechanical Behaviour of an XLPE Insulation Layer for Hi-Voltage Composite Power Cables: Effect of Voids on Onset of Coalescence

The harshness of the submarine environment represents a serious threat for immersed high voltage power cables, extensively used for offshore wind farms, which in turn are supposed to last for at least 20 years for their total investment to be economically viable. The Crosslinked Polyethylene (XLPE) used for the insulating layer of the cables may suffer different degradation phenomena, leading to unexpected breakdowns and rises in costs. In this work, numerical simulations have been developed to study the mechanisms by which micrometric pores inside XLPE can enlarge and coalesce (namely, water treeing) when the insulation is subjected to the intense electric field generated by hi-voltage wires. The study aim is to predict material plasticization next to voids, which is supposed to represent the onset of coalescence of neighboring pores. A microscale-level finite element coupled electro-mechanics model has been developed to describe the interactions between the intense electric fields and the subsequent Maxwell stresses in a dielectric. The roles of different influencing parameters such as distance, relative volumes, and the shape of two neighboring voids in a representative unit volume are considered. Finally, the behavior of a generic microstructure characterized by randomly distributed voids immersed in an electric field is simulated.

ENVIRONMENTAL SANITATION IN MAINTAINING THE QUALITY OF LIFE IN THE MANGROVE BEACH AREA

Mangrove forest is one of the plant communities that live in coastal areas. One of the causes of inhibiting the proliferation of mangrove forests is garbage disposal, the impact of garbage pollution will affect marine biota. Many tourists throw garbage in the mangrove forest area and this garbage can damage the growth of mangrove trees. The purpose of this study was to determine environmental sanitation in coastal areas and mangrove forests. This type of research is to use a descriptive qualitative research design in the form of written or spoken words from people and observed behavior. The results of the study show that the environment around the mangrove forest can be categorized as fulfilling the requirements. However, there are still several problems, such as the management of waste that is directly burned individually and not transported by the government. The availability of clean water and mangrove trees are put to good use.

Influence of snowpack on forest water stress in the Sierra Nevada

Higher global temperatures and intensification of extreme hydrologic events, such as droughts, can lead to premature tree mortality. In a Mediterranean climate like California, the seasonality of precipitation is out of sync with the peak growing season. Seasonal snowpack plays a critical role in reducing this mismatch between the timing of water input to the root zone and the peak forest water use. A loss of snowpack, or snow droughts, during warmer years, increases the asynchrony between water inputs and the peak of forest water use, intensifying water stress and tree mortality. Therefore, we hypothesize that the montane vegetation response to interannual climate variability in a Mediterranean climate is regulated by the snowpack. We tested this hypothesis using the 2012–2015 drought as a natural experiment. Regional Generalized Additive Models (GAMs) were used to infer and quantify the role of snowpack on forest water stress. The models simulate the Normalized Difference Infrared Index (NDII) as a proxy of forest water stress using water deficit (as seasonality index), location, slope, and aspect. The GAMs were trained using 75% of the data between 2001 and 2014. The remaining 25% of the data were used for validation. The model was able to simulate forest water stress for 2015 and 2016 across the northern, central, and southern Sierra Nevada with a range of R2 between 0.80 and 0.84. The simulated spatial patterns in forest water stress were consistent with those captured by the USDA Forest Service Aerial Detection Survey. Our findings suggest that the failure of a reduced snowpack in mitigating water deficit exacerbates forest water stress and tree mortality. Variations in water and surface energy budget across an elevational gradient play a critical role in modulating the vegetation response. These results provide insights into the importance of the Sierra Nevada snowpack under a warming climate. The models can aid forest managers to identify future forest water stress and tree die-off patterns.

DISSECTION OF YIELD AND FIBER QUALITY TRAITS UNDER DROUGHT CONDITION IN GOSSYPIUM HIRSUTUM L.

Moisture is a significant component in cotton growth and yield, but stress is the main factor limiting crop productivity since it has a negative impact on cotton's ability to produce high-quality fiber as well as square/boll and lint output. Reduced water availability during the development of the bolls could lead to drastically decreased yield. Four cotton genotypes (MNH-1020, FH-114, BH-178 and CIM-602) were grown under regular irrigation and water-deficit circumstances to examine the tolerance to water scarcity. To further understand the impacts of water shortage, four watering treatments were used in this study: control 100% field capacity, 70% field capacity, 60% field capacity, and 40% field capacity at the squaring stage till boll formation. As the amount of soil moisture declines, we have observed fall in fiber length, fiber fineness, and fiber strength. Yield/plant reduced under water stress due to less no of flowers and bolls, but also because of reduced boll weight. When the stress was extreme during the reproductive growth stage. MNH-1020 showed drought tolerance as by exhibiting maximum yield, boll weight and fiber characters when compared to other three varieties, while FH-114 being second. CIM-602 showed drought susceptibility as it exhibited least no of bolls/plant, yield/plant and boll weight.

Trait‐mediated community assembly during experimental grassland restoration is altered by planting year rainfall

Abstract Ecological restoration outcomes are highly variable, undermining efforts to recover biodiversity and ecosystem functions. One poorly understood source of variability is ‘year effects’—interannual variation in environmental conditions during the first year of restoration that alter successional trajectories of plant communities. There have been few experimental tests disentangling planting years from other differences among restoration projects (e.g. edaphic conditions, restoration approach), particularly those resolving mechanisms for year effects such as planting‐year rainfall. Moreover, past year effect studies focused almost exclusively on species‐level consequences. Therefore, the extent to which year effects influence the traits of communities is unknown. To address these gaps and provide a mechanistic test of how precipitation contributes to year effects, we conducted an experiment where we manipulated rainfall (drought, average and high levels) during the first growing season, replicated across three establishment year treatments to disentangle the effects of precipitation from other drivers of year effects. In each establishment year, we seeded the same species mix to initiate grassland restoration. We then surveyed plant community compositions annually for 5 years to quantify trait responses of restored communities to planting year rainfall. We found that variation in planting‐year precipitation altered community assembly trajectories by influencing community‐weighted mean (CWM) trait composition, and these effects persisted for at least 5 years. Over time, CWM specific leaf area and CWM seed mass decreased and CWM plant height increased. The effect of age on CWM plant height was stronger in plots that received mean and high watering treatments compared to drought treatments. This effect was also observed for CWM seed mass, albeit weaker. We also found some evidence for planting year effects unrelated to planting‐year rainfall for the three CWM traits, illustrating how interannually varying environmental conditions besides rainfall can generate persistent year effect on plant communities through their traits. Synthesis and applications. Our results provide evidence for planting year rainfall interacting with community assembly to alter the functional trait composition of restored grasslands. This suggests that interannual variation in rainfall during establishment is an important source of divergent biodiversity and functional outcomes in restored grasslands.

Improvement on water tree resistance and electrical properties of XLPE by adopting triallyl isocyanurate

The effect of TAIC (triallyl isocyanurate) on water tree resistance and electrical properties of XLPE (peroxide crosslinked polyethylene) was investigated in this paper. XLPE specimens with different content of TAIC were prepared for hot pressing method. Water blade method results showed that water tree ageing resistance of XLPE was improved obviously by adopting TAIC. The diameters of microvoids in specimens generated by water droplets would be reduced from micron scale to submicron scale due to the existence of TAIC. Contact angle test and Monte Carlo molecular simulation results revealed that water droplets would be disintegrated due to the presence of TAIC. Moreover, the addition of TAIC can also slightly improve the electrical properties of XLPE. The first-principles calculations revealed that an electron-bound state was generated in the band gap of XLPE for bonding with TAIC and formed a deep trap with 2.3eV. It can be concluded that low mixing energy of TAIC and water is an important reason for improving the water tree resistance of XLPE, and its improvement on electrical properties is attributed to the introduction of deep trap.

Reflection characteristics of water treeing insulation in medium voltage cables

This paper presents an analytical model based on wave reflection of dual interfaces for studying the reflection due to water treeing in the cross-linked polyethylene (XLPE) insulation of medium voltage cables. The model is expected to predict the reflection characteristics more accurately than that only considering reflection of a single interface. Experiments on a cable sample with mimic water trees are conducted to confirm the effectiveness of the presented model. The model can potentially be used to relate time-domain reflectometry (TDR) measurement results with characteristics of water treeing insulation in the cables.

Increasing the growth and yield of shallot (Allium cepa L. Aggregatum group) by using Methyl Jasmonic Acid (MeJA) concentrations under drought condition

Drought is one of the limiting factors for plant production, and there is a continuous demand for drought tolerant plants. Shallots are considered a shallow-rooted crop and have been reported to have little tolerance to drought conditions. One of the efforts to increase plant tolerance to drought conditions is through the addition of Methyl Jasmonic Acid (MeJA). MeJA is involved in several physiological and biochemical procedures in plant growth and development. Application of MeJA can increase the plant tolerance to drought conditions through chlorophyll synthesis, stomatal conductivity, transpiration, net photosynthetic rate and biomass production. This research was conducted in a complete randomized block design with three replications to determine the response of shallot plants to the application of MeJA (0 µM, 25 µM, 50 µM and 100 µM) under drought conditions, which was simulated through the frequency of watering (once daily, every other day, once in three days). Soil water content calculated before the watering treatment was 24.45%, 20.34% and 18.45% for watering once daily, every other day, once in three days, respectively. The results showed that the addition of MeJA played a role in enhancing the growth and productivity of shallot plants under normal and drought conditions. Application of 50 µM of MeJA could increase the Water Use Efficiency, maintain the Relative Water Content, increase the width of stomatal aperture, and increase the leaf area and Leaf Area Index. This also led to increasing Net Assimilation Rate and Plant Growth Rate. Application of 50 µM of MeJA gave in increasing bulb productivity and reached 7.86 ton.ha-1, which was 58.2 % higher than that of in control (without MeJA application). Application of MeJA to shallot plants exhibited avoiding type of physiological tolerance.

Restoring functional forested peatlands by combining ditch-blocking and partial cutting: An amphibian perspective

Artificial drainage for forestry has caused major degradation of temperate peatland ecosystems. Partial restoration of those ecosystems is now widely considered, but feasible targets and effectiveness of restoration practices are not well established. In this study, we analyse a forested peatland restoration experiment in Estonia from a functional perspective of amphibian populations. In 2014–2020, we surveyed a before-after-control-impact experiment that combined two habitat manipulations: partial cuttings for restoring sparse tree canopy cover, and ditch blocking with soil filling to restore the water table. We monitored the responses in the aquatic habitats and breeding of brown frogs (moor frog Rana arvalis and common frog R. temporaria). Along with the expected habitat changes (ditch blocking quadrupled water depths and tree cutting reduced the shade), we found that ditch blocking restored the soil-type specific water acidity levels that the draining had homogenized. Partial ditch blocking reduced frog breeding activity in the first year, but it recovered and increased later on, specifically on sapric Histosols and supported by temporary wetlands, floods and pools created. However, the number of offspring did not clearly respond to the restoration and instead varied much among years. Our results indicate that, in drained forested wetlands: (i) near-natural aquatic habitats are a distinct restoration target and several years of post-restoration monitoring are needed to confirm the development of ecological integrity; (ii) increased breeding activity of amphibians may not result in improved recruitment; and thus, (iii) integrative wetland restoration techniques could benefit from an “amphibian perspective” of sustaining their whole life cycles and the food webs they support.