Soil Moisture Treatments Research Articles

Leveraging extensive soil, vegetation, fire, and land treatment data to inform restoration across the sagebrush biome

ContextWidespread ecological degradation has prompted calls for massive global investments in ecological restoration, yet limited resources necessitate efficient application of restoration efforts. In western North America, altered fire regimes are increasing the scale of restoration needed to preserve the sagebrush (Artemisia species) biome but prioritizing and implementing effective restoration is complicated by the vast and heterogeneous sagebrush landscape, which includes gradients in climate, disturbance, and species composition.ObjectivesTo develop spatially explicit and context-dependent estimates of treatment efficacy and sagebrush recovery rates.MethodsWe leveraged a suite of spatio-temporally extensive datasets to evaluate the influence of restoration treatments and environmental conditions on trends in post-disturbance sagebrush cover, with an emphasis on understanding differences between sites recovering naturally and sites receiving restoration treatments. We used estimates from these models to develop spatially explicit projections for sagebrush recovery, conditional on disturbance, restoration practice, and environmental conditions.ResultsWe found seeding Artemisia spp. increased sagebrush cover over time relative to natural recovery, but this relationship depended on spring soil moisture availability and treatment methods. Natural recovery was positively influenced by soil moisture and sagebrush cover and negatively influenced by cumulative burns and annual herbaceous cover, while the influence of perennial herbaceous cover varied with soil moisture.ConclusionsOur results provide biome-wide insights and spatially explicit tools that can inform economic cost-effectiveness analyses, restoration prioritization tools, and other scientific endeavors to ensure managers have the tools and information needed to effectively steward the sagebrush biome in a rapidly changing world.

Soybean plants enhance growth through metabolic regulation under heterogeneous drought stress

Heterogeneous drought stress (HED) is prevalent in drought-resistant practices such as deficit irrigation, root zone irrigation and strip intercropping. The mechanisms and improvement of crop drought resistance under HED are not fully understood. This study used double-root grafted Nandou 12 (ND12) soybean seedlings to simulate HED treatment under controlled conditions. Seedlings were transplanted into root cups with waterproof partitions to establish different soil moisture treatments: sufficient irrigation (SI) with 80 % soil moisture on both sides, HED with 80 % on one side and 40 % on the other, and homogeneous drought stress (HOD) with 60 % on both sides. The results indicated that soybean plants treated with HED exhibited healthier growth compared to those treated with HOD. Photosynthesis rate (Pn), stomatal conductance (cond.), transpiration rate (Tr), and relative water content (RWC) decreased by 10.24 %, 43.90 %, 152.66 %, and 8.69 % in HED-treated plants, respectively, but dry biomass increased by 3.38 %. Conversely, HOD conditions led to a significant decline in these parameters. Metabolomic and transcriptomic analyses revealed significant changes in the biosynthesis and signaling pathways of key phytohormones and metabolites, including abscisic acid (ABA), gibberellin (GA), jasmonic acid (JA), isoflavones, starch, and sugars. In HED-treated plants, GmNCED downregulation resulted in 54.22 % less ABA than HOD. GA levels increased under HED with upregulation of GmGA3OX1 and GmGA3OX2. JA content in HED-treated roots was 90.90 % higher than in HOD-treated roots. Isoflavones concentration including genistein (73.01 %), genistin (63.63 %), malonylgenistin (20.58 %), malonylgenistin (65 %), diadzin (38.15 %), and malonyldiadzin (47.61 %) levels, were significantly higher in HED-treated plants. Antioxidant enzyme activities indicated a 20 % increase in peroxidase (POD) activity under HED, while malondialdehyde (MDA) content was 27 % higher in HOD-treated plants, indicating greater oxidative stress. Chlorophyll content remained stable, and starch concentration increased by 33.33 % in HED-treated plants compared to HOD-treated plants. HED enhances phytohormonal responses and metabolic adjustments in soybean plants, boosting photosynthetic efficiency, antioxidant capabilities, growth, and drought resilience. This regulatory mechanism balances growth promotion and drought resistance, highlighting HED potential in improving crop resilience.

Effects of CO2 and Soil Moisture Treatments on Morphological and Allometric Trait Variation in Coppiced Seedlings: A Study of Four Early-Successional Deciduous Species

Atmospheric CO2 levels have been increasing, and likewise, increasing drought events have been following increasing temperatures. There is very little literature on the effects of climate change factors on early-successional deciduous species used for ecological restoration. Thus, morphological and allometric variation in four coppiced early-successional deciduous species was examined in response to a 2 × 2 factorial of ambient CO2 (aCO2, 400 ppm) and elevated CO2 (eCO2, 800 ppm), as well as well-watered and drought treatments with 15%–20% and 5%–10% volumetric moisture content, respectively, grown in sandy soil with low soil nitrogen (N) under greenhouse conditions. The four species examined were as follows: green alder (Alnus viridis subsp. crispa (Ait.) Turrill), speckled alder (A. incana subsp. rugosa (Du Roi) R.T. Clausen), gray birch (Betula populifolia (Marshall)), and white birch (B. papyrifera (Marshall)), and all are from the same phylogenetic family, Betulaceae. Genus differences in morphological and growth traits were large, especially in response to the environmental treatments used. Alders upregulated all growth traits under eCO2 because of the strong coppicing sink effect and the additional foliar N provided by the actinorhizal ability of the genus, whereas birches remained the same or slightly decreased under eCO2. As a result, alders have a significantly greater foliar N than birches, with 2.8 and 1.0%, respectively. All species reduced growth under drought, and green alder had the greatest stem dry mass growth, followed by speckled alder and then the birches. Under drought, eCO2 not only mitigated the alder drought dry mass but, in fact, doubled the stem dm, whereas eCO2 only just mitigated the birches drought response. When corrected for size using stem height, alders allocated more to stem and leaf and less to root dry mass than birches. Atmospheric CO2 and soil moisture treatments changed organ biomass allocation. The tallest stem height was the best predictor of total (above and below) dry mass. With increasing atmospheric CO2, particularly on low nutrient sites, the results show alders are capable of sequestering far more carbon than birches. In addition, with more atmospheric CO2, alders can mitigate against drought conditions better compared to birches.

RESPONSE OF SUNFLOWER CROP TO DIFFERENT LEVELS OF SOIL MOISTURE DEPLETION

The amount of water utilized by the plant has a significant impact on its yield. In this regard, yield response factor (Ky) permits measuring yield decline as a function of evapotranspiration. As a result, the purpose of this study was to calculate Ky for the sunflower crop grown in North Nile Delta, Egypt and to calculate economic water productivity. Seasons 2021 and 2022 were studied. The experiment used a complete randomized block design with three replicates. W1 (50-55%), W2 (55-60%), and W3 (60-65%) maximum allowable depletion of available soil moisture (MAD of ASW) treatments were used. In total, the average two seasons (0.52 and 0.61) found for sunflower crop under W2&W3, respectively, demonstrated its strong sociability to water deficit. Its yield is substantially impacted by water availability, with average 0.65 & 0.47% loss in yield for every 1% reduction in evapotranspiration with w2 and w3 treatments, respectively. The treatment without stress, w1 (50-55% MAD of ASW), yielded the highest grain yield. However, after considering water and irrigation costs, it could conclude that other stressed treatments, W2&W3, were more cost-effective.

Microbial resistance and resilience to drought and rewetting modulate soil N2O emissions with different fertilizers

Future climate models indicate an enhanced severity of regional drought and frequent rewetting events, which may cause cascading impacts on soil nitrogen cycle and nitrous oxide (N2O) emissions, but the underlying microbial mechanism remains largely unknown. Here we report an incubation study that examined the impacts of soil moisture status and nitrification inhibitor (DCD) on the N2O-producers and N2O-reducers following the application of urea and composted swine manure in an acid soil. The soil moisture treatments included 100 % water-holding capacity (WHC) (wetting, 35.3 % gravimetric soil water content), 40 % WHC (drought, 7 % gravimetric soil water content), and 40 % to 100 % WHC (rewetting). The results showed that N2O emissions were significantly decreased under drought conditions and were significantly increased after rewetting. The resistance of ammonia-oxidizing bacteria and nosZII, which was inhibited by urea or manure application, modulated N2O emissions under drought conditions. The resilience of the functional guilds modulated their dominant role in N2O emissions with rewetting. Ammonia-oxidizing bacteria, nirS-type denitrifying bacteria and nosZI showed significant resilience in response to rewetting. Significant negative relationships were observed between N2O emissions and nosZII clade under wetting condition and between N2O emissions and nosZI clade after rewetting. Our results highlighted the importance of microbial resistance and resilience in modulating N2O emissions, which help to better understand the dominant way of N2O emissions, and consequently make efficient mitigation strategies under the global climate change.

Seaweed supplementation to organic dairy cows may reduce climate impact of manure in pasture soils during a laboratory incubation

AbstractIntroductionEnteric methane (CH4) emissions are one of the largest components of the anthropogenic CH4 budget, and with accelerating climatic changes, there are calls to reduce anthropogenic greenhouse gas emissions. Certain seaweeds fed as supplements can reduce enteric CH4 emissions from ruminant animals by as much as 80%; however, these studies have yet to analyze downstream impacts that may arise from the deposit of affected manures on pastures or agricultural fields.Materials and MethodsHere we conducted a 28‐day soil and manure incubation utilizing manures collected from dairy cows in a seaweed feeding trial to analyze the impacts of manure on greenhouse gas fluxes and nutrient cycling. Cows were fed different diets with a control group (no seaweed supplementation), and a 3% and 6% by dry‐weight seaweed (Chondrus crispus) supplementation. Three soil moisture treatments were also tested, with a field moist capacity [67% gravimetric water content (GWC)], a drier group (50% GWC), and a saturated treatment (84% GWC).ResultsWe found that manure from seaweed‐fed cows reduced emissions of carbon dioxide and had similar emissions of methane and nitrous oxide to the control. Higher moisture levels increased CH4 emissions and nitrous oxide emissions with CH4 emissions trending higher in seaweed supplements trending higher in. Inorganic nitrogen turnover varied more based on moisture levels than seaweed supplements, as did the magnitude of methane and nitrous oxide emissions. Total carbon and nitrogen mostly decreased except in the 3% seaweed supplementation, which increased carbon and nitrogen with a drop in C:N in the 50% GWC group.ConclusionSeaweed supplements may partially reduce climate impacts of manures from cows fed seaweed supplements or at least not cause harm or impact manure quality. Given feeds may reduce enteric CH4 emissions, they may be a part of a successful strategy to reduce climate impacts of cattle.

Effect of soil moisture on efficacy to eliminate dampness and relieve jaundice and flavonoid content of Sedum sarmentosum

The growth environment of medicinal plants plays an important role in the formation of their medicinal quality. However, there is a lack of combined analysis studying the close relationship between the growth environment, chemical components, and related biological activities of medicinal plants. Therefore, this study investigated the effect of different soil moisture treatments on the efficacy to eliminate dampness and relieve jaundice and the flavonoid content of Sedum sarmentosum, and explored their correlation. The flavonoid content in the decoction of S. sarmentosum growing under field conditions with soil moisture levels of 35%-40%(T1), 55%-60%(T2), 75%-80%(T3), and 95%-100%(T4) was compared. The effects of these treatments on liver function parameters, liver inflammation, and oxidative damage in mice with dampness-heat jaundice were evaluated, and the correlation between pharmacological indicators and flavonoid content was analyzed. The results showed that the total flavonoid and total phenolic acid content in the decoction of S. sarmentosum were highest in the T1 treatment, followed by the T3 treatment. The content of quercetin, kaempferol, and isorhamnetin was highest in the T2, T1, and T3 treatments, respectively. Among the different moisture treatments, the T3 group of S. sarmentosum effectively reduced the levels of serum ALT, AKP, TBIL, DBIL, TBA, as well as hepatic TNF-α and IL-6 in mice with jaundice, followed by T2 treatment, especially in reducing AST level. The T4 treatment had the poorest effect. Correlation analysis showed a significant negative correlation between AST, ALT, AKP levels in mice and the total content of quercetin and the three flavonoids. MDA showed a significant negative correlation with the total flavonoid content and kaempferol. TNF-α exhibited a significant negative correlation with the content of isorhamnetin. In conclusion, S. sarmentosum growing under field conditions with a soil moisture level of 75%-80% exhibited the best efficacy to eliminate dampness and relieve jaundice. This study provides insights for optimizing the cultivation mode of medicinal plants guided by pharmacological experiments.

Effects of shading, soil moisture, fertilizations and sowing time on isoflavone content of soybean seed in Hokkaido

ABSTRACT Aiming to produce soybean seeds with high yield and high isoflavone content in Hokkaido, which has cool weather, we evaluated the effects of shading, soil moisture, fertilizations (K,N,P,Mo) and sowing time on yield and seed isoflavone content using mainly a high-isoflavone variety, Yukipirika. Shading treatments of 50 % and 70 % during the seed filling stage in a greenhouse decreased both yield and isoflavone content. Applying four soil moisture treatments from pF 1.5 to pF 2.8 in the seed filling stage in a greenhouse gave a positive correlation between soil moisture and both yield and isoflavone content. K fertilization treatments with different amount and various types of fertilizers were conducted in fields at medium or high level of K2O in soils typical of Hokkaido uplands. The additional K treatments did not increase yield or isoflavone content significantly in the field experiments. N (urea foliar application) treatments in fields did not affect yield and isoflavone content significantly. And P (phosphite root application) and Mo (seed treatment) in fields did not change isoflavone content, either. Sowing two weeks and four weeks later than the standard sowing time in a field decreased the yield but did not change the isoflavone content. From a practical application perspective, for producing soybean seeds with high isoflavone contents and high yield in Hokkaido, it is effective to plant at a standard time with a normal amount of fertilizer in fields with minimum shade and to maintain the soil moisture at well-watered levels during the seed filling stage.

Unraveling mechanisms underlying effects of wetting–drying cycles on soil respiration in a dryland

Rewetting of dry soils usually stimulates soil carbon (C) emission, a phenomenon known as the Birch effect. Soil C cycling in drylands, which store approximately one third of terrestrial soil organic C (SOC), is strongly affected by wetting–drying cycles. However, the physical, chemical, and biological mechanisms that link rewetting cycles with dryland soil C cycling have not been comprehensively studied, nor do we understand how these mechanisms interact with each other. Here, we conducted a dryland soil incubation experiment manipulating four factors related to global change (soil moisture content, soil moisture variability, C availability, and prior warming) in a factorial design. The experiment was divided into two periods: a rewetting period consisting of six 14-d wetting–drying cycles; and a recovery period lasting 28 days during which soil moisture content was held stable, allowing for examination of the legacy effects of the wet-dry cycles. Rewetting cycles decreased soil aggregate stability under some conditions, but their effects on soil microbial biomass and fungal communities, soil enzyme activities, soil priming, and soil dissolved C were not significant. We found lower average soil respiration under the wetting–drying treatment than the stable soil moisture treatment, and Birch effects were observed, but only under some conditions. This was probably because moisture variability exacerbated soil microbial metabolic stress, which showed itself as oxygen limitation during the initial precipitation pulse and as water limitation during soil drying. Notably, respiration rates remained low even after moisture fluctuations ceased, suggesting a legacy effect of rewetting cycles on dryland microbial communities. Overall, rewetting inhibited aggregate formation (physical mechanism), and suppressed soil respiration by inducing soil microbial metabolic stress (biological mechanism), ultimately leading to lower soil C loss under rewetting. Our findings indicate that Birch effects are mediated by the magnitude of moisture variability, the availability of C, and the degree of physiological stress microbes experience.

Intraspecific trait variation and adaptability of Stipa krylovii: Insight from a common garden experiment with two soil moisture treatments.

Understanding patterns of intraspecific trait variation can help us understand plant adaptability to environmental changes. To explore the underlying adaptation mechanisms of zonal plant species, we selected seven populations of Stipa krylovii, a dominant species in the Inner Mongolia Steppe of China, and evaluated the effects of phenotypic plasticity and genetic differentiation, the effects of climate variables on population trait differentiation, and traits coordinated patterns under each soil moisture treatment. We selected seeds from seven populations of S. krylovii in the Inner Mongolia Steppe, China, and carried out a soil moisture (2) × population origin (7) common garden experiment at Tianjin City, China, and measured ten plant traits of S. krylovii. General linear analyses were used to analyze how soil moisture and population origin affected each trait variation, Mantel tests were used to analyze population trait differentiation-geographic distance (or climatic difference) relationships, regression analyses were used to evaluate trait-climatic variable relationships, and plant trait networks (PTNs) were used to evaluate traits coordinated patterns. Both soil moisture and population origin showed significant effects on most of traits. Aboveground biomass, root-shoot ratio, leaf width, specific leaf area, and leaf nitrogen (N) content were significantly correlated with climate variables under the control condition. Specific leaf area and leaf N content were significantly correlated with climate variables under the drought condition. By PTNs, the hub trait(s) was plant height under the control condition and were aboveground biomass, root length, and specific leaf area under the drought condition. This study indicates that both phenotypic plasticity and genetic differentiation can significantly affect the adaptability of S. krylovii. In addition, soil moisture treatments show significant effects on trait-climate relationships and traits coordinated patterns. These findings provide new insights into the adaptive mechanisms of zonal species in the semiarid grassland region.

Response of soil microbial community structure, carbon and nitrogen cycling to drying and rewetting

Global change scenarios predict that precipitation regimes will become more variable in many parts of the world, extending drought periods and increasing rainfall intensity. Under these conditions, soil microbial community composition will likely change in ways that have implications for microbially-mediated nutrient cycling. Understanding these responses is key to predicting consequential changes in ecosystem functions. A 30 day incubation experiment was used to investigate the response of microbial community structure to three different soil moisture treatments, namely, constantly moist (CM), constantly dry (CD), and drying-rewetting (DRW), in soils of three different land condition types (Remnant, Restored, and Old-field) from Para Woodlands Nature Reserve, South Australia. Soil respiration and inorganic N transformations were approximately the same across soils, despite fundamental differences in physicochemical properties, vegetation communities, and land-use history. Soil microbial community structure changed in response to the different soil moisture treatments; responses of taxa was divergent among soils. These results demonstrate that changes to soil moisture regimes under climate projections will almost certainly have consequences for soil microbial communities and C and N dynamics. The results highlight the need for further research to understand the mechanisms driving divergent responses to soil moisture, particularly in areas of different land-use types.

Unraveling the interaction effects of soil temperature and moisture on soil nematode community: A laboratory study

Soil nematode communities and their functions are simultaneously influenced by abiotic factors such as temperature and soil moisture. However, the complex interaction effects of these factors have not been clearly demonstrated, limiting our understanding of soil biodiversity and functions under different climate scenarios. Here, we conducted a short-term microcosm experiment, implementing three temperature treatments (20 °C, 25 °C, and 30 °C) combined with two soil moisture treatments (50% and 80% water-holding capacity). We comprehensively assessed the changes in abundance, diversity, composition, and functions (carbon footprints) of soil nematode communities under these different treatments. Our findings revealed that temperature and moisture did not have significant effects on the richness or Shannon diversity of nematodes, while they did have significant impacts on other properties. We found that the interaction effect between temperature and moisture had a greater influence on total abundance compared to their independent effects. Moisture emerged as the primary driver of nematode community composition, followed by the interaction term, while temperature exhibited the least influence. Contrary to expectations, increasing temperature did not cause a shift in the community towards small-bodied genera when considering intraspecific variability in body mass. However, elevating moisture level led to an increase in community-weighted mean body mass, irrespective of intraspecific variability. Consequently, the body-mass-related footprints varied among treatments when considering intraspecific variability, with the dominant influence arising from the interaction effect. Overall, our study highlights the dominant interaction effect of temperature and soil moisture on multiple ecological properties of nematode communities. Additionally, we underscore the importance of incorporating intraspecific trait variability when assessing the responses and functions of nematodes under distinct environmental conditions.

Automatic Drought Tolerance Measurement of the Soil-Living Microarthropod, Folsomia Candida

Soil is a complex habitat where microarthropods, such as mites (Acari) and springtails (Collembola) species occur in high number and species diversity. Microarthropods play an essential role in organic matter decomposition and provide an important ecosystem service in soil. The soil-dwelling microarthropods are sensitive to environmental changes; therefore, their ecological characteristics are used to evaluate soil conditions. In modern environmental ecology, several species are involved in assessing the ecological consequences of drought periods. The growth rate is a standard sublethal parameter by which the body size of individuals is measured. Extracting microarthropods from the soil is difficult and time-consuming, requiring a high amount of human resources. Only a few samples can be processed due to laboratory limitations and high costs. However, nowadays the rapidly developing artificial intelligence (AI) technologies promise new opportunities in many research areas.Data on soil-dwelling microarthropods could be collected quickly and automatically using our new digital soil extractor device, the Edapholog, equipped with image analysis based on AI. This device recognizes living individuals, classifies them, and measures their body length automatically. Using this system, the growth and reproductive success of various species in the same experimental culture could be rapidly and simultaneously monitored. In this study, we aimed to analyse the applicability of the Edapholog for measuring the body size of Collembola species and Folsomia candida through a set of drought tolerance tests with three soil moisture treatment levels. Moisture content was set based on the maximum water holding capacity (Wmax) of the soil applied. The three levels were set to Wmax:35%, 40%, and 50%. Furthermore, we aimed to test the reliability of the detection and recognition of the species and the accuracy and reliability of the automatic body size measurement of individuals.Significant correlation (r= 0.94) exists between the automatically and manually measured body sizes. Although the different soil moisture treatments did not show marked differences in the collembolan body sizes between the moisture treatments, we found a significant difference in the reproduction rates between W50 and the other two (W35 and W40) treated groups. The Edapholog can greatly contribute to quick and precise data extraction and can have vast applicability in environmental ecology.

Developing Functional Relationships between Soil Moisture Content and Corn Early-Season Physiology, Growth, and Development.

Drought is a severe threat to agriculture production that affects all growth stages of plants, including corn (Zea mays L.). Any factor affecting early seedling growth and development will significantly impact yield. Despite the recurrence of low rainfall during the growing seasons, corn responses to different early-season soil moisture content levels have not been investigated. In this study, we investigated how corn morpho-physiological and biomass traits responded to varied soil moisture content during the early vegetative stage. Two corn hybrids were grown in a pot-culture facility under five different soil moisture treatments (0.15, 0.12, 0.09, 0.06, and 0.03 m3 m-3 volumetric water content, VWC) to assess the growth and developmental responses to varied soil moisture content during early-season growth (V2 to V7) stage. Sub-optimal soil moisture content limited plant growth and development by reducing physiological and phenotypic expression. Stomatal conductance and transpiration were decreased by an average of 65% and 59% across stress treatments relative to optimum conditions. On average, soil moisture deficit reduced the total leaf area by 71% and 72% compared to the control in 'A6659VT2RIB' and 'P1316YHR', respectively. Shoot and root dry weights were reduced by 74% and 43% under 0.03 m3 m-3 VWC. An increase in the root-to-shoot ratio was noticed under low VWC conditions compared to the control. Based on the stress tolerance index, the physiology and leaf growth parameters were more sensitive to soil moisture deficit. Our results highlight the impact of sub-optimal soil moisture on physiology and morphological traits during early-season growth. 'P1316YHR' demonstrated better physiological performance under stress conditions, while 'A6659VT2RIB' produced relatively better root growth. The findings suggest that biomass partitioning between shoot and root components is dynamic and depends on stress intensity. The current findings can help to prioritize traits associated with the early-season drought tolerance in corn. The functional relationships developed between soil moisture content and growth and developmental responses can be integrated into corn crop modeling to allow better irrigation management decisions.

Effects of water use efficiency on plant dry matter in NERICA and Japanese rice cultivars under drought conditions

NERICA (New Rice for Africa) was produced by crossing Asian rice (Oryza sativa L.) and African rice (Oryza glaberrima Steud.) and recorded to be drought tolerance. This study aimed to examine the transpiration and water use efficiency affected plant aboveground dry matter in total 29 cultivars including 23 NERICA, 1 indica-type and 5 japonica-type cultivars. Seedlings were transplanted 2 plants per pot (1/5000 a Wagner pot) on June 14, 2021. When the flag leaf appeared, three water treatments with three replications were imposed for 14 days. The control plot (C) was watered daily to maintain the water content per pot at field capacity (SW). The water content of medium dry pots (MD) and hard dry pots (HD) were maintained at 40% and 10% of SW, respectively. Surface of the pots was covered to eliminate the evaporation. Samples for dry matter measurement were collected on the same day starting and ending water treatment. Water use efficiency (WUE) was significantly different among cultivars when soil moisture treatments were included, and the same observation on soil moisture treatments when included cultivars. NERICA 4 showed the lowest WUE while NERICA 9 and Hokuriku 193 had the highest WUE. Cultivars with higher transpiration rate (Tr) had higher dry matter production (ΔDW). Under high vapor pressure deficit, ΔDW was more correlated with transpiration corrected by vapor pressure deficit (Tr/VD) than with WUE.

Characteristics of Maize Roots under Subsurface Drip Irrigation through Various Oxygen Treatment

In Korea, irrigation technology using subsurface drip irrigation (SDI) is new in agriculture system. Many limitations of SDI are not well known. SDI can damage crops from overwatering. To address this weakness, it is important to improve and test the applicability of the SDI with air injection (oxygation). Therefore we investigated soil oxygen (O2) and carbon dioxide (CO2), root characteristics and yield of maize using two conditions of soil moisture regime: field capacity (FC) × 100% and 120%. Maize was planted, and then air was injected by compressor and venturi. In the field, irrigation was controlled by a controller connected to soil moisture sensors. Soil moisture sensors were measured at 20 cm below soil surface. Soil O2 and CO2 were measured at 10 and 30 cm below soil surface before and after oxygation. Root activity was measured from tip of roots. Root volume and dry weight were measured. Post-harvest, number and weight of maize ears were surveyed as well. As a result, soil oxygen values increased by 59% in the compressor treatment and by 34% in the venture treatment. However, soil CO2values did not depend on the oxygation. In all soil moisture treatments, the activity of oxygated roots was greater than that of the control, and root activity was increased by 152%. Root volume and dry weight were also greater than those in the control. No significant effect of soil moisture was found on the number and weight of ears of maize. The average ear weight of maize in the FC 100% soil moisture treatment was 1,292 kg 10a-1 in the oxygation and 1,278 kg 10a-1 in the control. In addition, no effect of oxygation was observed on number and weight of ears. The average ear weight of maize in the FC 120% soil moisture treatment was 1,229 kg 10a-1 in the oxygation and 960 kg 10a-1 in the control. Maize yield was 28% greater in the oxygation treatment than that in the control. The yield of maize grown in the control field showed a tendency to decrease as the soil moisture content increased. At FC 120% soil moisture, the ear weight of control maize was reduced by 25% compared to FC 100% soil moisture. These results reflected that the oxygation process had a great effect on the root growth even in humid conditions, which was expected to have a positive effect on the maize plants planted above-ground.Root activity, dry weight and volume of corn as a result of soil moisture and oxygation; Soil moisture treatments (field capacity × 100%, field capacity × 120%), Oxygation treatments (compressor, venturi), Control (no air was injected). Soil moisture regime Oxygation treatment Root activity (µg g-1 h-1) Root dry weight (g) Root volume (cm3) 100% of field capacity Compressor 50.1 ± 1.69 b† 49.5 ± 19.25 a 269 ± 83.8 a Venturi 67.8 ± 3.25 a 44.6 ± 10.17 a 224 ± 34.9 a Control 32.2 ± 2.08 c 12.5 ± 5.55 b 59 ± 43.8 b 120% of field capacity Compressor 50.8 ± 1.07 a 42.4 ± 0.74 ab 225 ± 5.0 b Venturi 39.2 ± 1.54 b 73.7 ± 25.75 a 326 ± 56.6 a Control 35.8 ± 1.52 c 14.6 ± 9.81 b 60 ± 48.2 c †a, b and c represent significant difference level at 95%.

Water limitation reveals local adaptation and plasticity in the drought tolerance strategies of Bouteloua gracilis

AbstractAs the frequency and severity of drought increase in many regions around the globe, quantification of key drought tolerance traits and the intraspecific variability of these traits will improve predictions of the vulnerability of a species to novel drought conditions. The objective of this study was to quantify the variability in drought tolerance traits and correlate this to the sensitivity of plant growth to different soil moisture levels across populations of Bouteloua gracilis. Fourteen populations of B. gracilis were sampled along one local elevation‐aridity gradient in northern Colorado and one latitude‐aridity gradient from South Dakota to New Mexico. Individuals from each population were clonally propagated and subjected to high and low soil moisture treatments in a greenhouse and were measured for gas exchange, midday water potential (Ψmid), osmotic potential (Ψosm), biomass production, and morphological traits. Under water‐abundant conditions, plants from the most arid region produced more total biomass (67%) than plants from the most mesic system, yet experienced the greatest sensitivity (−34%) when subjected to water limitation. Productivity was strongly and negatively correlated with the magnitude of osmotic investment across all populations: each megapascal of osmotic potential was correlated with a decrease of 2.3 g of biomass under water‐limited conditions. Gas‐exchange and leaf morphological measurements did not explain these patterns. Unlike plants from the mesic regions, plants from the most arid regions did not adjust Ψosm. This lack of plasticity may be a local adaptation and the likely source of increased sensitivity in these populations.

Effects of different soil moisture on the growth, quality, and root rot disease of organic Panax notoginseng cultivated under pine forests

The under-forest economy in the agroforestry system can improve land use efficiency, protect ecological environment, and promote arable land sustainable development. However, the effects of soil moisture in the forest and irrigation strategies on the healthy growth of intercropping crops are still incomplete. Here, considering the organic Panax notoginseng cultivated under pine forests (PPF) as the research object, we explored the effects of different soil moisture on the physiological state, yield, quality and disease occurrence of PPF. Our results suggested that 80–85% and 95–100% field capacity (FC) treatments were more conducive to increased photosynthetic rate and biomass accumulation of PPF, but 50–55% and 65–70% FC treatments were more conducive to the accumulation of saponins in PPF leaves. Notably, the root rot index of PPF was highest under 95–100% FC (19.51) treatment, significantly higher than that under 65–70% FC (8.44) and 80–85% FC (10.21) treatments. Further, the rhizosphere microorganisms of PPF under different soil moisture treatments were sequenced, and the sequencing data analysis revealed that high soil moisture (95–100% FC) could destroy the microbial diversity balance and cause the accumulation of pathogens (Fusarium oxysporum and Ilyonectria radicicola), leading to a high incidence of root rot. The incidence of PPF root rot was negatively correlated with rhizosphere microbial diversity. Overall, our results highlight that the quantitative irrigation (80–85% FC) is conducive to maintaining the balance between yield, saponin content and disease occurrence of PPF, providing a practical basis for PPF irrigation strategy and promoting the sustainable development of PPF agroforestry system.

Chlorophyll Pigment and Leaf Macronutrient Trait Variation of Four Salix Species in Elevated CO2, under Soil Moisture Stress and Fertilization Treatments

Leaf chlorophyll pigment and macronutrient concentrations were quantified for four willow species (Salix cordata (COR), S. discolor (DIS), S. eriocephala (ERI) and S. interior (INT)) while growing under 2 × 2 factorial of ambient and elevated CO2 and well-watered and drought-stressed soil moisture treatments (Expt. 1). After the first year, we saw no difference in stem biomass between CO2 treatments. In the following year, a second experiment was conducted on a subset of well-watered willows as a 2 × 2 factorial of atmospheric CO2 and soil fertilization (FERT). For both years of Expt. 1, chlorophyll a, b, a + b (TCC) and carotenoids (CAR) significantly downregulated in response to elevated CO2 (eCO2) and upregulated in response to drought (DRT). In Expt. 2, FERT mitigated CO2 downregulation of TCC and CAR, and upregulated TCC and CAR. Across species, ERI had the greatest pigment concentrations followed by either COR or DIS. Except for one case, INT had the lowest pigment concentrations. A significant species x FERT interaction was due to magnitude effects. The CHLa:b ratio was not affected by CO2 or DRT but did increase in response to FERT. INT had the greatest CHLa:b ratio followed by DIS, then either ERI or COR. In the second year, TCC:CAR ratio decreased in response to eCO2 and increased in response to DRT and FERT. In Expt. 1, leaf N was the only nutrient to significantly downregulate in response to eCO2; whereas all other nutrient levels remained unchanged. In response to DRT, leaf N and Mg upregulated; whereas leaf P, K, and Ca were downregulated. In response to eCO2 in Expt. 2, again only leaf N downregulated; whereas all other nutrients remained unchanged. All leaf nutrients upregulated in response to FERT. Of the four species, INT had the greatest leaf N and K, and the lowest Ca. Species variation was important, but so to was clonal variation in response to change. Indeed, INT leaf chlorophyll and macronutrients are significantly different or segregated from the other three willow species and this may be related to the evolutionary origins of INT, and other species of the taxonomic section Longifoliae, in the arid southwest USA and Mexico. Furthermore, under low nutrient conditions, it may be necessary to fertilize the plants to see a biomass response to eCO2.

Terrestrial gastropod species-specific responses to forest management: Implications for Parelaphostrongylus tenuis transmission to moose

Landscape management can influence the distribution, abundance, and diversity of the terrestrial gastropods that host known parasites of managed species of ungulates. Multiple taxa of terrestrial gastropods are important intermediate hosts in the lifecycle of the parasitic nematode Parelaphostrongylus tenuis, for which white-tailed deer (Odocoileus virginianus) are definitive hosts. Moose (Alces alces) become infected with P. tenuis when they incidentally ingest gastropod intermediate hosts, leading to morbidity and mortality. Populations of moose in Minnesota have declined and P. tenuis infection has been identified as a leading cause of mortality. We investigated the role of forest management disturbance on the terrestrial gastropod community, and specifically known intermediate host species of P. tenuis, on the Grand Portage Indian Reservation in northeastern Minnesota, USA, where moose are an important subsistence species to the Grand Portage Band of Lake Superior Chippewa. Field crews surveyed gastropods through timed searches of soil and litter, and opportunistic collections from browse and pellets of white-tailed deer and moose. We digested all identified gastropods to determine prevalence of P. tenuis infection. We examined gastropod community responses to management and forest cover type using multivariate regressions. We additionally used regressions to examine total gastropod richness and abundance, as well as P. tenuis intermediate host responses to cover type, soil moisture class, canopy cover, treatment, and years since treatment. Digestions detected no infected gastropods from the 621 identified specimens. Gastropod community assemblages differed with recent understory treatment, but no other predictors. Total gastropod abundance, richness, and host abundance (liberal definition, including Deroceras spp.) were lower in sites treated within the last five years. For known intermediate host taxa, we observed species-specific responses to forestry treatments through time. Specifically, Deroceras spp. recolonized sites post-treatment (0–30 years), Discus cronkhitei were higher in abundance immediately following treatment, and the Succinea ovalis group, along with pooled intermediate hosts, displayed no discernable patterns. Our results underscore the complexity of P. tenuis lifecycles and transmission dynamics to moose, the importance of management disturbance and disturbance frequency in regulating gastropod populations, and the potential of forest management treatments to reduce P. tenuis infection in moose.