Water Tree Research Articles

Drought tolerance to overwatering, periodic underwatering and complete withholding of water in interior Douglas-fir seedlings

Seedlings of 95 greenhouse-grown interior Douglas-fir half-sibling families originating from four breeding zones were subject to overwatering and periodic underwatering and compared to an optimally watered control (15 per family = 1425 seedlings total). Averaged over all trees, annual height was reduced by 4% and 11% compared to controls for overwatering and periodic underwatering, respectively. Family overwatered seedling height was 135–75%, and underwatered height was 100–75% of their respective control heights. Shorter families under stress grew like their control compared to taller families, but this was reversed in taller families when the watering conditions were ideal. A survival analysis indicated that after 30–50 days without water, family survival varied from 25% to 90%, and most trees died after 60 days. The breeding zone had little effect on the tolerance to suboptimal water or survival during complete water withdrawal and did not interact with watering treatments. Family traits for tolerance to overwatering favoured root biomass, traits for underwatering favoured reduced stem biomass, especially in ratio to roots, and traits for survival favoured belowground biomass over aboveground biomass. No tradeoffs between tolerance to over- and underwatering were found. Some families did well in all three conditions and some in one or the other. The study results suggest that variation in family growth and survival to suboptimal watering partly relate to root and stem biomass partitioning in the interior Douglas-fir population of British Columbia.

Enhancing highland ecosystems in East Hararge, Ethiopia: evaluating intervention strategies for species diversity, soil organic carbon stock, and carbon sequestration

Forest loss and soil degradation pose significant challenges globally, particularly in developing nations like Ethiopia. Various intervention strategies have been implemented to rehabilitate degraded ecosystems. However, research gaps exist in understanding the most effective approaches, particularly in highland ecosystems. This study aimed to evaluate the effectiveness of different intervention strategies on species diversity and carbon stock in the West Hararghe zone, specifically at the Doba district Hades site. The data was collected from 5 February 2022 to 10 December 2022. The study area was characterized by systematic plots and transects to assess vegetation diversity and soil properties across four intervention categories: (physical; only soil and water conservation structures were used, enclosure; only animal and human interaction was restricted, biological; only different tree species were planted, biophysical; both soil water conservation and tree planting were used). Soil samples were collected at different depths, and biomass estimation was conducted using established formulas. Statistical analyses, including one-way ANOVA and post-hoc tests, were performed to test the level of significance. Biophysical interventions exhibited the highest species diversity index (SDI) (4.65 ± 1.21), followed by enclosure interventions (1.68 ± 0.58), while physical interventions recorded the lowest SDI (0.63 ± 0.18). Enclosure interventions led to the highest soil organic carbon (SOC) stocks at 40.13 t C ha−1, followed by biophysical interventions at 39.26 t C ha−1. Physical interventions resulted in the lowest SOC stocks at 23.9 t C ha−1, underscoring their potential for carbon sequestration. Biophysical interventions, which include both above-ground and below-ground biomass, showed significant carbon stock accumulation, totaling 173.8 t C ha−1 (39.26 t C ha−1 from SOC and 114.6 t C ha−1 from biomass), highlighting their effectiveness in enhancing ecosystem resilience. Other studies support these findings, underscoring the importance of context-specific approaches and long-term monitoring for sustainable land management. Enclosure and biophysical interventions emerge as promising strategies for enhancing species diversity and soil health, as well as promoting carbon sequestration in highland ecosystems. These findings emphasize the need for informed decision-making and community involvement in ecosystem restoration efforts to achieve meaningful and lasting impacts.

Effect of propolis added to single-bottle adhesives on water permeation through the hybrid layer.

Water treeing and water droplets are observed within adhesive layers and on the hybridized surface after bonding sound dentin using single-bottle etch-and-rinse adhesives, indicating permeability of the hybrid layer to water. The aim of this study was to assess the efficacy of dentin sealing by adhesives containing propolis by quantifying the area of water transudation from dentinal tubules after dentin hybridization. Brazilian red propolis was added to experimental adhesive and Single Bond (3M/ESPE) adhesive; experimental adhesive and Single Bond without propolis were used as controls. Under simulated pulp pressure, two layers of adhesive were applied to etched human dentin discs. Three minutes after light-curing, the hybridized dentin surface was replicated, and epoxy resin replicas were created to obtain scanning electron microscope images. Data were evaluated using ANOVA and Tukey's test. Single Bond containing propolis significantly decreased water permeation through the hybrid layer compared with the control group. Three minutes after polymerization, the experimental adhesive without propolis had formed a permeable hybrid layer. The addition of Brazilian red propolis significantly reduced surface water on hybridized dentin in a concentration-dependent manner. Two-step etch-and-rinse adhesives containing propolis were effective in reducing water permeation through the hybridized dentin surface.

Talking to the young generation: perception of nature-based solutions’ attractiveness by children from Generation Z

ABSTRACT Current studies on nature-based solutions (NBS) in urban areas often overlook young people, who are essential users of urban spaces. Our study from the Czech Republic fills this gap by investigating how children (Generation Z, 11–15 years) perceive 12 NBS and 3 grey infrastructure measures and their ecosystem services (ES). Results from an image-based questionnaire survey indicate that water features, trees and flower beds are the most attractive for spending leisure time, while most other features were perceived as relatively unattractive by the children surveyed. In addition, the results highlight oxygen production as the most valued service by children, followed by biodiversity support and aesthetic function. This study emphasises the need for inclusive management of NBS and recognises the role of multiple stakeholders, including children, in creating attractive urban spaces. Key policy highlights Exploring the preferences of Generation Z towards different nature-based solutions Some measures and benefits were perceived as more attractive and important Water features, trees, and flower beds were rated as the most attractive measures Oxygen provisioning, biodiversity, and aesthetics were identified as the most important benefits Children and young people are essential users of urban nature and public spaces

Impact of urban spatial dynamics and blue-green infrastructure on urban heat islands: A case study of Guangzhou using Local Climate Zones and predictive modeling

Amidst mounting concerns regarding health risks associated with excessive carbon emissions, attention has turned to the heat mitigation ability of blue-green infrastructure (BGI). BGI offers heat mitigation through transpiration cooling, effectively countering the urban heat island (UHI) effect while facilitating energy conservation and carbon reduction. This study adopted the InVEST model to assess the spatial pattern of UHI and heat mitigation service based on the Local Climate Zone (LCZ) classification, along with quantifying the energy savings in Guangzhou for 2019. The results revealed that the UHI effect exhibited greater intensity in the southwest built-up area. Compact Lowrise (LCZ-3) and Heavy Industry (LCZ-10) areas demonstrated higher UHI intensity, while Water (LCZ-G) and Dense Trees (LCZ-A) areas showcased the highest heat mitigation index (HMI) and optimal cooling capacities. Three urban development scenarios were devised to simulate the UHI distribution, heat mitigation capacity, and energy savings by 2025, using the CA-Markov model. In comparison to the Baseline scenario, the Environmental Protection scenario showed a modest 3.67 % decrease in the built-up area, but a noteworthy increase in HMI and energy saving, by 21.2 % and 6.6 % respectively. This scenario can serve as a reference pathway for urban energy conservation and sustainable development.

Structural Integrity Analysis of Marine Dynamic Cables: Water Trees and Fatigue

Abstract Offshore power cables are typically designed to have a service life of around 25 years. A pattern is emerging where these cables only last 10 years or even as little as two. The main consensus as to why the service life is so short is due to a combination of fatigue and fretting/wear damages of the copper conductors and water treeing in the insulation material. This study presents a method that can be used to analyze the structural integrity of dynamic subsea power cables and estimate their service life determined by the factors above. The numerical simulation models developed and used to carry out global and local fatigue analyses of dynamic subsea power cables are presented, together with methods and models for assessing fretting, wear, and growth of water tree defects. A methodology for structural integrity assessment that includes all these factors is proposed. A dynamic subsea power cable connected to a wave energy converter is used as the case study for comparison of the service life when these factors are considered compared to when, e.g., the growth of water trees is excluded. A numerical sensitivity analysis demonstrates that the value of the seawater's electrical conductivity and the insulation material's threshold stress-intensity factor greatly influence the cable's service life.

A Novel Technique for Estimating the Location of Defect or Inception of Water Treeing in the Semiconducting Screen of a Cable

A Novel Technique for Estimating the Location of Defect or Inception of Water Treeing in the Semiconducting Screen of a Cable

Inception of vented water trees in high voltage XLPE cable insulation: Effect of inorganic contaminations inside the semiconductive material

AbstractWet‐design AC subsea power cables are currently rated up to a maximum voltage of 72.5 kV. These high voltage (HV) cables are cost‐effective alternatives to subsea cables kept dry by a protective lead sheath and exhibit superior properties for dynamic applications. However, several vented water trees, degradation phenomena reducing the cable lifetime, are observed in a HV XLPE insulated cable subjected to wet aging in the laboratory. The water trees initiate from a smooth and clean XLPE insulation/semiconductive screen interface. In this paper, we show that voids in the range 15–150 μm are observed in the conductor screen, 50–320 μm from the water tree inception sites. Degradation of the semiconductive material is observed, in the form of porous regions that connect the voids to the water tree inception sites. NaCl impurities are detected on the void surfaces and in the porous regions. These features are proposed to be the pre‐requisites for the formation of the vented water trees observed in this type of cable. The mechanism responsible for the formation of the void and porous regions in the semiconductive cable screen is discussed based on the observations.

Effects of enriched CO2, temperature, and irrigation on soil properties in greenhouse apple tree cultivation

The significant contributions of anthropogenic activity to global warming are evidenced by the increasing average atmospheric temperatures and CO2 concentration. To date, data on the impact of global warming on crops, particularly field-scale fruit growth and the soil environment, remain lacking. Therefore, we conducted a 4-year monitoring experiment on semi-closed apple tree populations cultivated under the present or near-future climate to assess the effects of atmospheric temperature and CO2 concentrations on soil moisture, temperature, and inorganic ion concentration. Apple saplings were grown in three independent environment-controlled greenhouses, namely greenhouses A (GH_A; control), B (GH_B; high-temperature), and C (GH_C; high-temperature and high CO2), representing climate modification experiments. The pH increased by 0.02, 0.20, and 0.12/year for GH_A, GH_B, and GH_C, respectively. In particular, GH_B (standard irrigation plot; STD) showed a significant pH increase of 0.25/year. The EC increased by 0.014 mS/cm/year for GH_A, decreased by -0.010 mS/cm/year for GH_B, and increased by 0.006 mS/cm/year for GH_C, showing no clear overall increasing or decreasing trend. The NO3 concentration increased by 1.2 mg/L/year for GH_A, decreased by 10.2 mg/L/year for GH_B and decreased by 0.7 mg/L/year for GH_C. The apparent activation energy (Ea) ranged from 85.3 to 214.4 (kJ/mol NH4+) and, regardless of watering treatment, GH_A > GH_B > GH_C. The values in STD plots were 1.4 to 1.7 times those in abundant irrigation plots. Using GH_A (STD) as a standard, the soil temperature dependence of the nitrification rate did not change overall at high or low air temperatures with increasing watering (Ea = 150.5 kJ/mol) or heating (Ea = 154.1 kJ/mol). The soil temperature dependence of the nitrification rate did not vary under heating and increased watering (Ea = 89.5 kJ/mol) or under heating, increased watering, and increased CO2 (Ea = 85.3 kJ/mol). This study provides novel insights into determining the environmental impacts of apple tree community soils under near-future climatic conditions.

High-resolution operational soil moisture monitoring for forests in central Germany

Abstract. The forests of central Germany (Saxony, Saxony-Anhalt, and Thuringia) are vital components of the local ecosystems, the economy, and recreation. However, in recent years, these forests have faced significant challenges due to prolonged climate-change-induced droughts, causing water shortages, tree stress, and pest outbreaks. One of the key components of the forests' vitality and productivity is the availability of soil moisture. Given the anticipated increase in the frequency and severity of drought events, there is a growing demand for accurate and real-time soil moisture information. This underscores the need for development of an appropriate monitoring tool to make forest management strategies more effective. The article introduces an operational high-resolution soil moisture monitoring framework for the forests in central Germany. The key components of this system include the advanced LWF-BROOK90 1D water balance model, a large database of the National Federal Forest Inventory, high-resolution forest soil maps, real-time climate data from the German Meteorological Service, and a web information platform for the presentation of daily updated results. This system informs the public and empowers forest managers and other decision-makers to take targeted, local measures for sustainable forest management, aiding in both drought mitigation and long-term forest health in the face of climate change. The validation of the system using soil moisture measurements from 51 stations with various sensor depths (up to 100 cm) showed an overall good agreement (0.76 median Pearson correlation), which was found to be higher for deciduous rather than coniferous forests. Finally, the framework is discussed against the background of the main limitations of existing monitoring systems and how operational soil moisture measurements contribute to better interpretation of simulations.

Response on root regrowth potential to soil moisture in Sedum species during winter in Særheim, Norway

PurposeThe impact of winter moisture on root metabolism and root integrity has potential consequences for the geographical distribution of drought-adapted succulent species and for their long-term performance on green roofs. The interacting effects of soil characteristics and precipitation frequency on root mortality under winter conditions and the potential to grow new roots in spring were evaluated for six Sedum species under controlled conditions. MethodsTo test for the impact of soil moisture during winter on root regrowth potential in six Sedum species, we used a combination of two substrates with differing water-holding capacity and four contrasting watering regimes. Specially, for the fine and coarse substrates, total pore volume was 42 and 46 %, respectively, and maximum water-holding capacity (i.e. field capacity) was 0.50 and 0.33 kg water per L, respectively. The four watering treatments involved overhead watering to runoff (approx. 10 mm): once every second week, once a week, three times per week and three times per week with 1 cm standing water in trays from January to March 2019. ResultsIt was found that winter soil moisture had no major impact on root mortality or root regrowth potential in spring. Root mortality was not affected by watering frequency and regrowth potential showed no directional response to increased watering frequency, although species-specific responses were involved. Root diameter did not differ between the substrates, but there were some differences between the species. Sedum rupestre had on average the thickest roots (0.17 mm), followed by S. acre, S. anglicum and S. sexangulare (0.15–0.16 mm), while S. album and S. hispanicum had the thinnest roots (0.12–0.13 mm). Moreover, effects of watering frequency on root mortality and regrowth potential were not influenced by soil water-holding capacity across species. We concluded that winter soil moisture had no negative effects on root performance within the range of treatments tested here. ConclusionsRoot response to transient waterlogging or moist but unsaturated soil may not be an important mechanism for determining the survival and distribution of temperate Sedum species during winter.

Impact of alternate partial root-zone irrigation on the rhizosphere microbiota of alfalfa plants inoculated with rhizobia.

Water is an important constraint on alfalfa (Medicago sativa) production in arid and semiarid areas, and alternate irrigation in root areas has water-saving potential for alfalfa production. To investigate the impact of alternate partial root-zone irrigation (APRI) on the rhizosphere soil microorganisms of alfalfa, this study subjected alfalfa plants to different irrigation methods and irrigation levels. The growth status and rhizosphere soil microbial community diversity of alfalfa plants under alternate root-zone watering treatment were analyzed through laboratory experiments and high-throughput sequencing. The results showed that at soil moisture levels of 80% field moisture capacity (FMC) and 60% FMC, APRI had no significant impact on the biomass or nodule number of alfalfa. However, 40% FMC significantly reduced the individual plant dry weight, chlorophyll content, and nodule number of the alfalfa plants. APRI increased the relative abundance of Actinomycetes in the alfalfa rhizosphere soil. Moreover, at 60% FMC, the MBC and MBN of rhizosphere, relative abundance of Actinobacteria and unclassified K fungi and Chao 1 index of bacteria significantly increased under APRI treatment. While relative abundance of Ascomycetes and Proteobacteria in the alfalfa rhizosphere significantly reduced under 60% FMC + APRI treatment. In summary, under the same irrigation conditions, APRI did not significantly affect the growth of alfalfa in the short term. And 60%FMC + APRI treatment did significantly affect the groups, structure and diversity of the rhizosphere soil microbial communities.

Assessing seed pellet formulations to improve native plant restoration under water‐limited conditions

Water scarcity, a challenge expected to worsen with climate change, significantly hinders native plant community restoration. Enhancing seed‐based restoration requires methods to increase the water availability for seeds and seedlings. Surfactants and superabsorbent polymers (SAPs) can improve soil water‐holding capacity and infiltration, but their use in seed enhancements remains underexplored. We investigated whether pellets containing surfactants or SAPs could improve seedling emergence of two native species (Rytidosperma caespitosum and Chrysocephalum apiculatum) common in temperate grasslands in south‐eastern Australia under different watering treatments. We used a randomized block design with five watering treatments to simulate predicted changes in precipitation for south‐eastern Australia: ambient, two reducing overall water volume, and two reducing watering frequency while increasing watering volume to maintain ambient treatment water volume. We explored four enhanced pellets (two containing surfactants and two containing SAPs) and non‐pelleted seeds. Our results showed that watering events with larger volumes but reduced frequency increased seedling emergence. Under these conditions, block co‐polymer surfactants further increased seedling emergence of C. apiculatum, while synthetic SAP pellets promoted emergence of R. caespitosum. Block co‐polymer surfactants decreased R. caespitosum emergence, and both SAPs reduced C. apiculatum emergence under reduced watering frequency. A 50% reduction in overall water volume significantly reduced seedling emergence for both species, regardless of seed enhancement. These findings suggest that surfactants and SAP pellets can improve the success of seed‐based restoration under ambient conditions and when rainfall events are larger in volume but reduced in frequency, but not when the overall volume of rainfall is reduced.

Responses of non-native and native plant species to fluctuations of water availability in a greenhouse experiment.

Water availability strongly influences the survival, growth, and reproduction of most terrestrial plant species. Experimental evidence has well documented the effect of changes in total amount of water availability on non-native vs. native plants. However, little is known about how fluctuations in water availability affect these two groups, although more extreme fluctuations in water availability increasingly occur with prolonged drought and extreme precipitation events. Here, we grew seven non-native and seven native plant species individually in the greenhouse. Then, we exposed them to four watering treatments, each treatment with the same total amount of water, but with different divisions: W1 (added water 16 times with 125 mL per time), W2 (8 times, 250 mL per time), W3 (4 times, 500 mL per time), and W4 (2 times, 1000 mL per time). We found that both non-native and native plants produced the most biomass under medium frequency/magnitude watering treatments (W2 and W3). Interestingly, non-native plants produced 34% more biomass with the infrequent, substantial watering treatment (W4) than with frequent, minor watering treatment (W1), whereas native plants showed opposite patterns, producing 26% more biomass with W1 than with W4. Differences in the ratio of root to shoot under few/large and many/small watering treatments of non-native vs. native species probably contributed to their different responses in biomass production. Our results advance the current understanding of the effect of water availability on non-native plants, which are affected not only by changes in amount of water availability but also by fluctuations in water availability. Furthermore, our results indicate that an increased few/large precipitation pattern expected under climate change conditions might further promote non-native plant invasions. Future field experiments with multiple phylogenetically controlled pairs of non-native and native species will be required to enhance our understanding of how water availability fluctuations impact on non-native invasions.

From waste to soil: Can we create functioning manufactured soils by recycling rock processing waste?

AbstractRock mining industries do not only exploit and transform extensive areas of land, but also produce vast amounts of rock waste material that lacks an adequate utilization. Some of these rock wastes have the potential to provide nutrients to plants and can therefore have positive impacts on soil properties. Consequently, we tested their potential for valorization as components of manufactured soils for use in urban areas. We conducted a 10‐week incubation experiment of soil mesocosms with sunflowers (Helianthus annuus L.) to evaluate the performance of manufactured soils with respect to plant growth and soil properties. We used three common rock materials (augite‐porphyry, greywacke‐hornfels, basalt), ground to powder and mixed into natural soils of either clayey or sandy texture. In order to test the performance under challenging environmental conditions, we applied a drought treatment in addition to a regular watering treatment. All manufactured soils were able to maintain plant growth, although the yield of aboveground biomass was significantly lower compared to the original soils. However, the effects of the water regime and the original soils on the overall plant growth were stronger than the effect of the rock powders, indicating that the manufactured soils were not hampering plant development more than challenging environmental conditions. The preparation of the manufactured soils altered the grain size distribution of the originally sandy and clayey soils. Since the rock powders contributed mainly to the silt‐sized particles, their addition to soils may improve the physical properties of the soil, especially the plant's available water content. We used wet‐sieving to isolate aggregate size fractions and thus analyse the formation of soil aggregates. The manufactured soils had a higher mass contribution of microaggregate‐sized particles, although this was mostly attributed to the presence of silt‐sized rock powder particles instead of aggregate formation. The total organic carbon (OC) content of the original soils was diluted in the manufactured soils, as the rock powders did not contain OC. However, the manufactured soils may have the potential for future OC storage due to the abundance of OC‐free mineral surfaces, which can retain organic matter as well as capture CO2 through enhanced weathering of primary minerals. Based on this work, the tested rock materials have the potential to be utilized as components in manufactured soils in the urban context that provide soil‐like functions, particularly in terms of sustaining plant growth. For improved results, additional measures to initiate a rapid development of soil structure are highly recommended, for example, by adding an easily decomposable source of organic matter.

Monitoring LULC Dynamics and Landscape Pattern Analysis Using Landsat at Mongla and Surrounding Cities in Bangladesh

This study presents a thorough analysis of the temporal dynamics in land use and land cover (LULC) within the Mongla Port and its adjacent regions in Bangladesh, spanning from 2018 to 2022 and utilizing Landsat 8 satellite imagery. A seven-category classification system, including water bodies, trees, flooded vegetation, crops, built-up areas, bare ground, and rangeland, facilitated a detailed exploration of changing landscape patterns. Over the study period, a 1.87% reduction in tree cover was observed, contrasting with consistent expansion in built-up areas, which increased by 2.42%. Noteworthy fluctuations in agricultural lands revealed a net decrease of 165.95 km², while water bodies experienced fluctuations, ultimately recording a net increase of 142.29 km². The robust accuracy assessment, with overall accuracy ranging from 86.7% to 88.8%, underscores the reliability of the classification process. This research holds significant implications, offering valuable insights into sustainable development, conservation strategies, and disaster preparedness in a region undergoing transformative changes due to port establishment, especially considering the inclusion of the ecologically critical Sundarbans in the study area.

Integrated analysis of transcriptomics and metabolomics of garden asparagus (Asparagus officinalis L.) under drought stress

BackgroundDrought is a leading environmental factor affecting plant growth. To explore the drought tolerance mechanism of asparagus, this study analyzed the responses of two asparagus varieties, namely, ‘Jilv3’ (drought tolerant) and ‘Pacific Early’ (drought sensitive), to drought stress using metabolomics and transcriptomics.ResultsIn total, 2,567 and 7,187 differentially expressed genes (DEGs) were identified in ‘Pacific Early’ and ‘Jilv3’, respectively, by comparing the transcriptome expression patterns between the normal watering treatment and the drought stress treatment. These DEGs were significantly enriched in the amino acid biosynthesis, carbon metabolism, phenylpropanoid biosynthesis, and plant hormone signal transduction pathways. In ‘Jilv3’, DEGs were also enriched in the following energy metabolism-related pathways: citrate cycle (TCA cycle), glycolysis/gluconeogenesis, and pyruvate metabolism. This study also identified 112 and 254 differentially accumulated metabolites (DAMs) in ‘Pacific Early’ and ‘Jilv3’ under drought stress compared with normal watering, respectively. The amino acid, flavonoid, organic acid, and soluble sugar contents were more significantly enhanced in ‘Jilv3’ than in ‘Pacific Early’. According to the metabolome and transcriptome analysis, in ‘Jilv3’, the energy supply of the TCA cycle was improved, and flavonoid biosynthesis increased. As a result, its adaptability to drought stress improved.ConclusionsThese findings help to better reveal the molecular mechanism underlying how asparagus responds to drought stress and improve researchers’ ability to screen drought-tolerant asparagus varieties as well as breed new varieties.

Does pollination interact with the abiotic environment to affect plant reproduction?

Abiotic and biotic components of the environment both limit plant reproduction, but how they interact with one another in combination is less understood. Understanding these interactions is especially relevant because abiotic and biotic environmental components respond differently to various global change drivers. Here we aim to understand whether the effects of pollination (biotic component) on plant reproduction depend on soil moisture (abiotic component), two factors known to affect plant reproduction and that are changing with global change. We conducted pollen supplementation experiments for two plant species, Delphinium nuttallianum and Hydrophyllum fendleri, in subalpine meadows in the Western USA across four years that varied in soil moisture. In a separate one-year field experiment, we factorially crossed water addition with pollen supplementation. We measured proportion fruit set, seeds per fruit, and seeds per plant, in addition to stomatal conductance, to determine whether plant physiology responded to watering. In the four-year study, only H. fendleri reproduction was pollen limited, and this occurred independently of soil moisture. Experimental water addition significantly increased soil moisture and stomatal conductance for both species. The effect of pollen addition on reproduction depended on the watering treatment only for H. fendleri fruit production. Reproduction in D. nuttallianum was not significantly affected by pollen addition or water addition, but it did respond to interannual variation in soil moisture. Although we find some evidence for the effect of a biotic interaction depending on abiotic conditions, it was only for one aspect of reproduction in one species, and it was in an unexpected direction. Our work highlights interactions between the abiotic and biotic components of the environment as an area of further research for improving our understanding of how plant reproduction responds to global change.

Study on water tree resistance and self‐healing properties of multi‐monomer melt‐grafted polyethylene

AbstractIn order to suppress the damage of cable insulation caused by water tree structure formed by micro‐droplets at insulation defects in low density polyethylene (LDPE) materials under AC electric field. In this paper, the siloxane group is grafted onto LDPE by melt grafting method, and different content of comonomer styrene (St) is added to improve the grafting rate of siloxane group grafted polyethylene. The effect of St on the microscopic characteristics of LDPE grafted KH570 is studied. In order to verify the accuracy and timeliness of water tree self‐healing of grafted polymer insulation materials, the microstructure characteristics of LDPE ungrafted and grafted polymer samples are analyzed by Fourier transform infrared spectroscopy, gel content test, and differential scanning calorimeter. Second, the AC dielectric properties of LDPE ungrafted and grafted polymer samples are studied by AC breakdown experiment and space charge test. Finally, the water tree length, micropore defects, and self‐healing of the samples are observed by optical microscopy and polarization and depolarization current method, and the changes of chemical composition in the water tree area before and after aging are analyzed by infrared spectroscopy. The principle and mechanism of repairing water tree defects with grafted monomers are explained. This paper not only combines the previous research results of self‐healing materials, but also provides a new method for the preparation process of LDPE grafted polymer, which has a good research prospect in practical application.

Irrigation optimization enhances water management and tree performance in commercial citrus groves on sandy soil

Irrigation optimization enhances water management and tree performance in commercial citrus groves on sandy soil