Increased Water Use Efficiency Research Articles

The combination of high leaf hydraulic safety and water use efficiency allows alpine shrubs to adapt to high‐altitude habitats

Abstract Leaf hydraulic traits are considered the key determinants of gas exchange and therefore affect species distributions along environmental gradients, but the patterns of leaf hydraulic traits and their associations with gas exchange across altitudinal gradients remain largely unknown. Here, we measured leaf hydraulic traits, gas exchange, leaf anatomical traits and plant size traits in two dominant alpine shrubs (Caragana jubata and Salix gilashanica) across an altitudinal gradient from 3100 to 3700 m. The findings indicated that with increasing altitude, both shrub species exhibited an increase in leaf hydraulic safety (more negative Kleaf P50), a decrease in leaf hydraulic efficiency (Kleaf‐max) and an increase in intrinsic water use efficiency (WUEi), thus allowing them to adapt to higher altitude habitats. The more negative Kleaf P50 was associated with a greater ratio of major to minor vein density (VLAmaj/VLAmin), the lower Kleaf‐max was associated with a lower minor vein density (VLAmin) and greater increase in WUEi arose from the small decrease in the photosynthetic rate relative to the stomatal conductance. However, C. jubata was consistent with the ‘hydraulic safety strategy’ with a great decrease in Kleaf P50, a small decrease in Kleaf‐max and a small increase in WUEi along with decreasing plant height and leaf area with increasing altitude. Whereas S. gilashanica was consistent with the ‘photosynthetic efficiency strategy’ with a small decrease in Kleaf P50, a greater decrease in Kleaf‐max and a greater increase in WUEi along with an increasing plant height and unchanged leaf area with increasing altitude. Overall, these findings provide new insights to improve understanding how shift in leaf hydraulic traits and their associations with gas exchange and plant size allow plants to adapt to high‐altitude habitats. Read the free Plain Language Summary for this article on the Journal blog.

Quantifying the effects of diffuse photosynthetically active radiation on water use efficiency in different ecosystems

Compared with direct radiation, diffuse radiation could be more efficiently used for photosynthesis because of the diffuse fertilization effect (DFE). Because carbon uptake and water loss are coupled through leaf stomata, DFE probably increases gross primary productivity (GPP) and evapotranspiration (ET) simultaneously. Multi-year eddy covariance flux observation data and simulated diffuse fraction of photosynthetically active radiation (PAR) for nine ecosystems across China (containing forest, grassland, wetland, and cropland) were used to quantify the impact of DFE on water use efficiency (WUE). The results showed that GPP firstly increased and then decreased with increasing diffuse fraction of PAR (kd-PAR = diffuse PAR/PAR) for each ecosystems. The kd-PAR values at which maximum GPP occurred varied between 0.34 and 0.76 across nine ecosystems. ET decreased with increasing kd-PAR in most ecosystems mainly because high kd-PAR (indicating low PAR) could reduce evaporation in most ecosystems. The relationships between WUE and kd-PAR were significantly linear with averaged slopes of forest, grassland, wetland, and cropland of 1.64, 0.96, 1.19, and 4.51 g C kg−1 H2O, respectively. A multiple linear regression method was used to analyze the effect of diffuse PAR (PARdif) and direct PAR (PARdir) on GPP and ET. The conversion efficiencies for PARdif were greater than for PARdir, and the relative differences were 178.35% and 23.77% for GPP and ET, respectively. The intensity of DFE for GPP and ET were greater for forest and cropland than for grassland and wetland. The intensity of DFE was 3.05 to 236.96 times higher for GPP than for ET. The mathematical analysis results demonstrated that the promoting effect of PARdif was greater for GPP than for ET, thereby inducing an increase in WUE with increasing kd-PAR. These results will be helpful for improving modeling accuracy of carbon and water cycles under the conditions accompanying global climate change.

Long-term variations in ecosystem water use efficiency in the Tibetan Plateau: Vegetation types, attribution methods and main drivers

Ecosystem water use efficiency (WUE) is a key indicator for understanding the response of carbon–water processes to environmental changes. However, as affected by uncertainty of WUE estimation and attribution, the individual contributions of environmental drivers to WUE changes and the underlying mechanisms remain unclear on the Tibetan Plateau (TP). Here, a theory-based analytical WUE model was modified by introducing an optimal stomatal behavior model, and used to estimate monthly WUE and their drivers during 1982–2018 for main vegetation types on the Tibetan Plateau (TP). Rationality of three mainstream analytical attribution methods—analytical-based partial derivative method (APDM), regression-based partial derivative method (NPDM), and climate elasticity method (CEM)—was examined. Furtherly, the contributions of various environmental drivers to WUE variation trend were estimated for various vegetation types. Results indicate that: (1) The modified model performed well in estimating WUE against with observed WUE at five eddy-covariance (EC) flux stations, which decreased the uncertainty of WUE estimation. WUE increased significantly in the TP with a slope of 0.49 × 10-2 g C kg−1 H2O yr−1 during 1982–2018 with forests increased most rapidly; (2) Only APDM captured both the variation and magnitude of WUE trends, and both NPDM and CEM failed to reproduce the magnitude of WUE trends, though CEM was better than NPDM benefited from its nonlinear structure. Through comparing these methods, we found that the nonlinear direct effects of these forcing variables on WUE change could be higher than their indirect effects caused by their interactions. (3) There are some differences in the main drivers of WUE trends for various vegetation types. Increase in WUE was mainly driven by the increase in leaf area index (LAI) for both steppes and meadows, while decreased air water vapor pressure deficit (VPD) and elevated CO2 showed higher positive effects for broad-leaf forests. The distinct response and extremely scarce EC observations of forests suggest that more attention should be paid to forests in the TP. This study could help in selection of attribution methods and understanding the mechanisms of carbon–water coupling of alpine ecosystems under a changing climate.

Additional organic and bacterium fertilizer input regulated soybean root architecture and dry matter distribution for a sustainable yield in the semi-arid Region of China.

In the dryland area of the Loess Plateau in northwest China, long-term excessive fertilization has led to soil compaction and nutrient loss, which in turn limits crop yield and soil productivity. To address this issue, we conducted experiments using environmentally friendly organic fertilizer and bacterium fertilizer. Our goal was to investigate the effects of additional organic and bacterium fertilizer inputs on soil water migration, crop root architecture, and yield formation. We implemented six different fertilizer strategies, namely: Nm (mulching, N 30 kg/ha), NPK1m (mulching, N 60 kg/ha; P 30 kg/ha; K 30 kg/ha), NPK2m (mulching, N 90 kg/ha; P 45 kg/ha; K 30 kg/ha), NPKOm (mulching, N 90 kg/ha; P 45 kg/ha; K 30 kg/ha; organic fertilizer 2 t/ha), NPKBm (mulching, N 60 kg/ha; P 30 kg/ha; K 30 kg/ha; bacterium fertilizer 10 kg/ha), and N (N 30 kg/ha; no mulching). The results revealed that the addition of bacterium fertilizer (NPKBm) had a positive impact on soybean root system development. Compared with the other treatments, it significantly increased the total root length, total root surface area, and total root length density by 25.96% ~ 94.89%, -19.63% ~ 36.28%, and 9.36% ~ 28.84%, respectively. Furthermore, NPKBm enhanced soil water consumption. In 2018, water storage during the flowering and podding periods decreased by 12.63% and 19.65%, respectively, while water consumption increased by 0.97% compared to Nm. In 2019, the flowering and harvest periods decreased by 23.49% and 11.51%, respectively, while water consumption increased by 0.65%. Ultimately, NPKBm achieved high grain yield and significantly increased water use efficiency (WUE), surpassing other treatments by 76.79% ~ 78.97% and 71.22% ~ 73.76%, respectively. Subsequently, NPK1m also exhibited significant increases in yield and WUE, with improvements of 35.58% ~ 39.27% and 35.26% ~ 38.16%, respectively. The use of bacterium fertilizer has a profound impact on soybean root architecture, leading to stable and sustainable grain yield production.

Endophyte-Mediated Populus trichocarpa Water Use Efficiency Is Dependent on Time of Day and Plant Water Status

Endophytes are potential partners for improving the resource use efficiency of bioenergy feedstock systems such as short rotation coppice Populus species. Endophytes isolated from members of the Salicaceae family have broad host compatibility and can improve water use efficiency (WUE) through decreases in stomatal conductance. However, the literature is inconsistent with regard to the environmental conditions and temporal patterns of these benefits. This study investigated how endophyte-mediated changes in Populus trichocarpa ‘Nisqually-1’ stomatal conductance and WUE shift with time and scale in response to water deficit stress. Leaf gas exchange and aboveground productivity were used to evaluate the carbon and water balance of greenhouse-grown plants in response to endophyte inoculation and water deficit. Differences in stomatal conductance between control and inoculated plants were more pronounced (39.7% decrease, Welch two-sample t [14.34 adjusted degrees of freedom] = –2.358, P = 0.033) under water deficit conditions in the late morning during a period of higher light intensity. The decrease in stomatal conductance accompanied a substantial increase in intrinsic WUE (iWUE) for water deficit inoculated plants. However, increases in iWUE did not result in improvements in aboveground productivity or shoot biomass WUE for water deficit inoculated plants. This decoupling between iWUE and aboveground productivity may be an indicator of assimilate allocation to microbial metabolism as an additional carbon sink or a shift in carbon allocation toward belowground biomass. Future work should take a whole plant approach that accounts for diurnal patterns in incident irradiance to evaluate the impact of endophyte inoculation on host WUE and stress tolerance.

Dynamic process of ecosystem water use efficiency and response to drought in the Yellow River Basin, China

Ecosystem water use efficiency (WUE) is a crucial indicator of the impact of climate change on terrestrial ecosystems, reflecting the balance between biological processes (photosynthesis and transpiration) and physical processes (evapotranspiration). However, the response mechanisms and driving processes of WUE to drought remain to be further understood. In this study, we analyzed the spatial and temporal dynamics and response mechanisms of WUE in the Yellow River Basin (YRB) using data on Gross Primary Productivity (GPP), Evapotranspiration (ET) and Standardized Precipitation Evapotranspiration Index (SPEI), which revealed the cumulative effect of drought on WUE and assessed the ecosystem's resilience. The study results showed that (1) GPP, ET and WUE in the YRB exhibited a significant increasing trend, with 63.04 % of the area showing a marked increase in WUE. (2) GPP was the dominant factor influencing WUE in 65.36 % of the area, particularly in cropland and grassland, while ET was more influential in forested areas. Vapor pressure deficit (VPD) was identified as the principal driver affecting vegetation GPP in semi-arid and semi-humid regions of the YRB. In contrast, soil moisture (SM) was the limiting factor in arid areas. (3) 71.00 % of the WUE in the basin was affected by drought cumulative effects, with an average cumulative duration of 4.5 months. Arid regions experienced the most extended duration of 7.29 months, compared to 3.05 months in semi-humid regions. (4) 74.85 % of the regional ecosystems exhibited ecological resilience to drought, particularly in the source areas of the western basin of the YRB. Shrublands have the highest drought resilience among vegetation types, while grasslands have the lowest. The resilience of each climatic zone was in the order of semi-humid, semi-arid, and arid order. This study comprehensively analyzed of the spatial and temporal dynamics and response mechanisms of WUE in the YRB, offering a new perspective and scientific basis for understanding and predicting the ecosystem response to climate change.

Differential responses in water-use strategies of evergreen (Ligustrum lucidum) and deciduous (Robinia pseudoacacia) trees to tunnel excavation in a subtropical karst trough valley

Tunnel(s) excavation could decrease groundwater levels and soil water storage and consequently change trees growth conditions in karst areas. However, the adaptation mechanisms of different tree species to altered hydrological conditions caused by tunnel(s) construction in karst areas remain unknown. Here, we investigated the water-use strategies of two different tree species (the evergreen Ligustrum lucidum and deciduous Robinia pseudoacacia) in response to tunnel excavation in a typical subtropical karst trough valley by using the sap flow density, stable isotopes (δ13C, δ2H, and δ18O) and MixSIAR models. Tunnel excavation resulted in a 3.7–6.3 % reduction in soil moisture content (SMC) in Zhongliang Mountain Karst Trough (ZMKT) Valley. Both tree species demonstrated reduced transpiration in tunnel-affected valley (TAV) compared to tunnel-unaffected valley (TUAV) (transpiration in TAV was only 77.6 % of TUAV), with evergreen trees exhibiting a smaller decline in transpiration compared to deciduous trees. Furthermore, the proportions of karst groundwater utilized by evergreen and deciduous tree species in TAV were 8.3 % and 5.0 % higher than in TUAV, respectively, with evergreen tree species exhibiting greater absorption of karst groundwater than deciduous tree species. Meanwhile, the average leaf δ13C values and WUEi (intrinsic water-use efficiency) of both tree species in TAV were 0.9 ‰ and 15.7 μmol/mol higher than those in TUAV, respectively, with evergreen trees exhibiting a smaller increase in WUEi compared to deciduous trees. These results indicate that tunneling-induced water stress events may prompt trees to adopt more conservative water-use strategies. Evergreen tree species rely on more karst groundwater absorption to sustain relatively higher transpiration rates, and deciduous trees adapt to severe water stress by increasing their WUEi or shedding leaves to minimize transpiration. Our finding contributes to the evaluation of eco-hydrological processes in karst areas affected by tunnel(s) excavation.

The genotypic variation in the positive response of sorghum to higher sowing density is linked to an increase in water use efficiency

In semi-arid tropical areas, sorghum is sown at very low planting densities. Hence, increasing plant density represents an opportunity to improve productivity. However, assessing the expected increase in water needs is critical prior to testing higher densities under rainfed conditions. This was tested with a panel of elite cultivars in field and lysimiter experiments, and testing the effects of two density treatment, high (HD, 22 plants.m-²) and low (LD, 11 plants.m-²), on grain and biomass yield and on water use and water use efficiency (WUE). Doubling the conventional sowing density significantly increased biomass and grain yield, with a genotypic variability in the biomass response. No link was found between the response to density and the maintenance of the tillering capacity, whereas the response to density was somewhat explained by a differential increase in the leaf area index under high density (r=0.43 P<0.05). Lysimeter experiments showed that, compared with the conventional density, the high-density treatment had 62% increase in biomass vs a 38% increase in water use, resulting in a 17% higher WUE on average of the genotypes tested. There was an appreciable genotypic variability in this degree of WUE increase under high density. The most striking result was the very tight positive link between the biomass response to density and the differential increase in WUE in the dry season (r=0.91 P<0.0001), whereas in the wet season this link was negative (r=-0.48 P<0.02). This work shows that intensifying sorghum production by increasing sowing density is possible, in the short term using cultivars that show the largest WUE increase under high density, in the longer term by breeding high-density adapted cultivars, targeting plant traits that explain the tight link between higher WUE and higher yield under high density.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology.

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.

Quantifying the water use efficiency of karst ecosystems and response to environmental factors

Study regionThe study area is located in Guizhou province, the centre of the karst region in southwest China. Study focusAs a typical karst region, Guizhou has long faced challenges with water scarcity. Quantifying water use efficiency (WUE) is crucial for the efficient use of water resources and sustainable management. This study examined the spatio-temporal evolution patterns and its driving factors on WUE in Guizhou using Theil-Sen's slope, partial correlation methods, and the geographic detector model. New hydrological insights for the region(1) The multi-annual mean WUE of non-karst region (NKR, 2.75 gC kg−1 H2O yr−1) is higher than that of karst region (KR, 2.10 gC kg−1 H2O yr−1) during 2001–2020. (2) The rate of increase of WUE was three times higher in KR than in NKR. (3) Precipitation and temperature were identified as the key factors influencing WUE. Interactions between each environmental factors were observed to have both bi-variate and non-linear enhancement effects. Notably, in the NKR, soil moisture, vegetation type and leaf area index were the dominant factors influencing WUE, with interactions between environmental factors had both enhanced and weakened effect on WUE. (4) The synergistic effects of these interactions exceeded the individual or cumulative effects of the two environmental factors. These findings contribute to our understanding of the environmental factors driving changes in WUE in the KR.

Arbuscular Mycorrhizal Fungi Improve the Performance of Tempranillo and Cabernet Sauvignon Facing Water Deficit under Current and Future Climatic Conditions.

Climate change (CC) threatens Mediterranean viticulture. Rhizospheric microorganisms may be crucial for the adaptation of plants to CC. Our objective was to assess whether the association of two grapevine varieties with arbuscular mycorrhizal fungi (AMF) increases grapevine's resilience to environmental conditions that combine elevated atmospheric CO2, increased air temperatures, and water deficit. Tempranillo (T) and Cabernet Sauvignon (CS) plants, grafted onto R110 rootstocks, either inoculated (+M) or not (-M) with AMF, were grown in temperature-gradient greenhouses under two environmental conditions: (i) current conditions (ca. 400 ppm air CO2 concentration plus ambient air temperature, CATA) and (ii) climate change conditions predicted by the year 2100 (700 ppm of CO2 plus ambient air temperature +4 °C, CETE). From veraison to maturity, for plants of each variety, inoculation treatment and environmental conditions were also subjected to two levels of water availability: full irrigation (WW) or drought cycles (D). Therefore, the number of treatments applied to each grapevine variety was eight, resulting from the combination of two inoculation treatments (+M and -M), two environmental conditions (CATA and CETE), and two water availabilities (WW and D). In both grapevine varieties, early drought decreased leaf conductance and transpiration under both CATA and CETE conditions and more markedly in +M plants. Photosynthesis did not decrease very much, so the instantaneous water use efficiency (WUE) increased, especially in drought +M plants under CETE conditions. The increase in WUE coincided with a lower intercellular-to-atmospheric CO2 concentration ratio and reduced plant hydraulic conductance. In the long term, mycorrhization induced changes in the stomatal anatomy under water deficit and CETE conditions: density increased in T and decreased in CS, with smaller stomata in the latter. Although some responses were genotype-dependent, the interaction of the rootstock with AMF appeared to be a key factor in the acclimation of the grapevine to water deficit under both current and future CO2 and temperature conditions.

Water and nitrogen footprint assessment of integrated agronomic practice management in a summer maize cropping system

The footprints of water and nitrogen (WF and NF) provide a comprehensive overview of the type and quantity of water consumption and reactive nitrogen (Nr) loss in crop production. In this study, a field experiment over two years (2019 and 2020) compared three integrated agronomic practice management (IAPM) systems: An improved management system (T2), a high-yield production system (T3), and an integrated soil–crop management system (ISCM) using a local smallholder farmer's practice system (T1) as control, to investigate the responses of WF, Nr losses, water use efficiency (WUE), and nitrogen use efficiency (NUE) to IAPM. The results showed that IAPM optimized water distribution and promoted water use by summer maize. The evapotranspiration over the whole maize growth period of IAPM increased, but yield increased more, leading to a significant increase in WUE. The WUE of the T2, T3, and ISCM treatments was significantly greater than in the T1 treatment, in 2019 and 2020 respectively, by 19.8–21.5, 31.8–40.6, and 34.4–44.6%. The lowest WF was found in the ISCM treatment, which was 31.0% lower than that of the T1 treatment. In addition, the ISCM treatment optimized soil total nitrogen (TN) distribution and significantly increased TN in the cultivated layer. Excessive nitrogen fertilizer was applied in treatment T3, producing the highest maize yield, and resulting in the highest Nr losses. In contrast, the ISCM treatment used a reduced nitrogen fertilizer rate, sacrificing grain yield partly, which reduced Nr losses and eventually led to a significant increase in nitrogen use efficiency and nitrogen recovery. The Nr level in the ISCM treatment was 34.8% lower than in the T1 treatment while NUE was significantly higher than in the T1 treatment by 56.8–63.1% in 2019 and 2020, respectively. Considering yield, WUE, NUE, WF, and NF together, ISCM should be used as a more sustainable and clean system for sustainable production of summer maize.

Effects of different fertilization practices on maize yield, soil nutrients, soil moisture, and water use efficiency in northern China based on a meta-analysis

The application of fertilizer to ensure the steady improvement of crop yield has become the main means of agricultural production. However, it remains to be determined whether fertilization practices with different combinations of nitrogen (N), phosphorus (P), potassium (K), and organic (O) fertilizers play a positive role in the sustainability of maize yield and the soil in which it is grown. Therefore,this meta-analysis extracted 2663 data points from 76 studies to systematically analyze and explore the effects of different fertilization measures on maize yield, soil nutrients, water content and water use efficiency (WUE) in northern China. Articles addressing this topic showed that fertilization effectively increased the soil nutrient content and maize yield. The soil organic matter (SOM) increased by 2.36 (N)–55.38% (NPO), total nitrogen content increased by 6.10 (N)–56.39% (NPO), available phosphorus content increased by 17.12 (N)–474.74% (NPO), and available potassium content changed by − 2.90 (NP)–64.40% (NPO). Soil moisture increased by 3.59% under a single organic fertilizer application and decreased by 4.27–13.40% under the other treatments. Compared with no fertilization, the yield increase of fertilized maize reached 11.65–220.42%. NP, NPK and NPKO contributed the most to increased yield in lithological, black and fluvo-aquic soils, respectively. The effects of different fertilization practices on maize yield varied in response to the same meteorological factors. The WUE increased from 9.51 to 160.72%. In conclusion, rational fertilization can improve the soil nutrient content and increase maize yield. The combined application of chemical and organic fertilizer showed the greatest increase in yield and WUE. Organic fertilizer application alone increased soil moisture. Our results provide a theoretical basis for fertilizer application and for improving the soil structure for maize cultivation in northern China.

Synergy of carbon and water use efficiencies in the Huai River Basin

Carbon Use Efficiency (CUE) and Water Use Efficiency (WUE) are pivotal ecological indicators. Clarifying whether they change synergistically can aid in understanding how terrestrial ecosystems adapt to climate and environmental changes. Utilizing meteorological and remote sensing data, our study assessed the spatial and temporal patterns of CUE and WUE in terrestrial ecosystems within the Huai River Basin from 2001 to 2020. Our findings revealed multi-year annual averages of 0.43 and 0.82 gC kg−1H2O for CUE and WUE, respectively. While CUE showed a significant increasing trend (P < 0.01), the increase in WUE was not significant (P > 0.05). The primary drivers behind temporal variations in these efficiencies included leaf area index (LAI), temperature, and soil moisture. In 77.96 % of the basin area, CUE and WUE exhibit synergistic changes. LAI was the predominant factor affecting both CUE and WUE, and dual-factor interactions amplify their influence. These insights enhance our understanding of regional carbon and water cycles and offer valuable guidance for the refinement of ecological conservation strategies.

Irrigation as an Effective Way to Increase Potato Yields in Northern China: A Meta-Analysis

A meta-analysis was conducted with the aim of exploring the influence of irrigation on potato yield, evapotranspiration (ET), and water-use efficiency (WUE) in northern China, considering factors such as irrigation methods, growing region, irrigation water-use efficiency (IWUE), irrigation frequency, soil types, and nitrogen (N) fertilizer rate. Overall, irrigation significantly increased potato yield and ET by an average of 45 and 54% compared to non-irrigation, respectively, but did not significantly increase the WUE. The increase in potato yield under irrigation is the most evident in aeolian sandy soil in northeast China and northwest China. Drip irrigation demonstrated the highest positive impact on both yield and WUE. Optimal yields were achieved with an irrigation amount ranging from 100 to 200 mm, while the highest WUE was observed with an irrigation amount of 30–50 mm. When the amount of irrigation exceeded 100 mm, the irrigation significantly resulted in decreased WUE compared to non-irrigation. The relative increase in yield per unit of irrigation amount and IWUE gradually decreased and eventually stabilized when the irrigation amount exceeded 100 mm. Therefore, the yield and WUE perform best when the irrigation amount is below 100 mm and the irrigation frequency is less than three times for sprinkling and flood irrigation methods. The greatest increases in yield and WUE under irrigation were found under a moderate N rate (150–250 kg N ha−1). Additionally, the relative increase in yield per unit of irrigation amount decreases gradually as the organic matter content increases. These findings suggest that the optimal benefits from irrigation might be realized when the irrigation amount is below 100 mm, with a moderate nitrogen fertilizer application and an irrigation frequency of three times. However, it is essential to consider local environmental factors such as the growing region, soil types, and organic carbon content.

Extreme drought triggers parallel shifts in wood anatomical and physiological traits in upper treeline of the Mediterranean Andes

BackgroundTreeline ecotones of Mediterranean ecoregions have been affected by the increasing intensity and severity of droughts. Even though the effect of droughts on forest dynamics has been widely documented, knowledge is relatively scarce of how extreme climate episodes affect the hydraulic structure and, therefore, the physiology of woody plants. The Mediterranean Andes have experienced an uninterrupted period of drought since 2010, including an extremely dry year in 2019 with approximately 80% rainfall deficit. Here, we investigated shifts in wood anatomical and physiological traits of Kageneckia angustifolia, an endemic treeline species, in response to this drought period.MethodsWe evaluated the xylem plasticity of three K. angustifolia populations across their natural distribution (31–35° SL) based on anatomical (vessel structure and distribution) and physiological (intrinsic water-use efficiency) variables in the tree rings. We focused on the period 2000–2020 that corresponds to before the megadrought (2000–2007), (ii) megadrought (2008–2018) and (iii) hyperdrought (2019–2020). The variables were annualized and analyzed by linear mixed-effects models.ResultsOur results provide insights to the anatomical and physiological mechanisms underlying the resilience of treeline forests to persistent droughts in central Chile. We found that the extreme drought in 2019–2020 triggered shifts in vessel size and frequency that increased hydraulic safety. These significant shifts in vessel traits occurred in parallel with a decrease in pit aperture area and an increase in water-use efficiency, further increasing the resilience of K. angustifolia to extreme drought stress.ConclusionsOur results revealed coordinated shifts in vessel size and frequency and water-use efficiency in response to the megadrought, thereby reducing vulnerability to hydraulic failure. The apparent resilience of K. angustifolia to extreme droughts suggests that this adaptation to drought stress may increase its ability to tolerate novel climatic conditions of treeline environments of the Mediterranean Andes, although it is not clear whether these adaptations will be sufficient to persist in scenarios that predict intensification of climate stress. Finally, our results provide empirical evidence that integrating wood anatomical and physiological traits facilitates the understanding of resilience mechanisms that treeline forests develop in the face of increasing drought stress.

Response of Productivity of Oilseed Flax Farmland to Different Crop Rotation Patterns Based on DSSAT Modeling

Abstract To further study the effect of different crop rotation patterns on the productivity of oilseed flax. In this study, the “Jinya No. 10” flax cultivar was used as the object, and a DSSAT model was constructed using 2017-2018 data to simulate the field trials (4-year rotation cycle) during the 30 years from 1994. The experiments were designed with six different crop rotation patterns including the following: flax→flax→flax→flax[(F)FFF], flax→wheat→maize→flax[(F)WMF], flax→maize→flax→wheat[(F)MFW], flax→flax→wheat→maize[(F)FWM], flax→wheat→flax→maize [(F)WFM], flax→wheat→maize→wheat[(F)WMW]. We investigated the effects of crop stubble, planting frequency of oilseed flax, years between plantings of oilseed flax, and years of continuous cropping on grain yield, aboveground biomass, and water use efficiency (WUE) in a semi-arid agricultural area. The results of the study showed that: (1) In the model calibration and validation, the RMSE of yield was 213.67 kg ha−1−217.43 kg ha−1, the RRMSE was 9.76%-10.79%; the RMSE of aboveground biomass was 796.24 kg ha−1−1527.81kg ha−1, the RRMSE was 13.46%-22.71%. The growing period of the cultivar was 95-97 d, indicating that the DSSAT model can simulate the productivity index of oilseed flax well. (2) Oilseed flax yield rotation than continuous mode significantly increased, the increase in 53.43%-54.28%, wheat, and maize stubble both significantly increased oilseed flax yield, compared with oilseed flax stubble increased by 31.04%, 31.95%. 25% oilseed flax frequency and 50% oilseed flax frequency than 100% oilseed flax planting frequency was significantly increased by 54.28% and 53.79%. The increase in grain yield of oilseed flax in the planting interval years was shown as 2a (32.97%) &gt; 3a (31.51%) &gt; 1a (30.84%). (3) The aboveground biomass of oilseed flax in the crop rotation compared to the continuous cropping pattern had a significant increase in the increase ranged from 60.49% to 100.31%. Wheat and maize stubble significantly increased the aboveground biomass of oilseed flax, compared with oilseed flax stubble increased by 25.67% and 22.56%. 25% oilseed flax frequency and 50% oilseed flax frequency than 100% oilseed flax planting frequency significantly increased by 92.02% and 72.81%. Oilseed flax aboveground biomass production in the planting intervals between the years of the increase in the performance of the 3a (39.8%) &gt; 2a (28.99%) &gt; 1a (19.45%). (4) The WUE of rotation compared to the continuous cropping mode increased between 45.78% and 58.54% for flax. The presence of wheat and maize stubble significantly increased the WUE of oilseed flax, compared to stubble of oilseed flax, which increased by 29.32% and 32.41%. 25% flax frequency and 50% flax frequency than 100% oilseed flax planting frequency significantly increased by 45.77% and 59.73%. Compared to the interval year 0a, the specific increase in WUE showed 2a (33.03%) &gt; 1a (31.37%) &gt; 3a (26.06%). Therefore, the continuous cultivation of oilseed flax will reduce productivity, should choose to rotate farming methods, replace different stubble, reduce the frequency of oilseed flax planting, and extend the interval between years of oilseed flax planting, and flax→wheat→maize→wheat is a suitable crop rotation mode in the northwestern dry zone.

Effect of Partial Root-Zone Irrigation on Plant Growth, Root Morphological Traits and Leaf Elemental Stoichiometry of Tomato under Elevated CO2

The increasing CO2 concentration ([CO2]) in the atmosphere decreases mineral nutrients concentration in crops, whereas it increases water use efficiency (WUE). Partial root-zone irrigation (PRI) could not only increase WUE but also improve plant nutrient status. Yet the effect of PRI combined with elevated CO2 concentration (e[CO2]) on the element stoichiometry of tomato leaves remains unknown. This study sought to investigate the responses of leaf mineral nutrients status and element stoichiometric ratios in tomatoes to PRI combined with e[CO2]. Tomato plants (cv. Ailsa Craig) were grown in pots in climate-controlled growth chambers with ambient [CO2] (a[CO2], 400ppm) and elevated [CO2] (e[CO2], 800ppm), respectively. Three irrigation regimes, i.e., full irrigation (FI), deficit irrigation (DI) and PRI, were applied to tomato plants at the flowering stage. The results showed that plants grown under DI and PRI had a similar biomass, enhanced root growth including greater root to shoot ratio, root length, surface area, volume and specific length, and an improved WUE in comparison with FI under e[CO2]. Additionally, under e[CO2], PRI showed an increase in leaf [C](+1.5%) and [N] (+9.3%), no decrease in leaf [K], [Ca], [Mg], [S] and [15N], but a decrease in leaf C/N (−6.6%) as compared with FI. Conclusively, PRI had the ability to improve leaf N concentration, maintain most leaf mineral nutrient concentrations, and optimize or maintain leaf element stoichiometric ratios under e[CO2]. Therefore, PRI would be a practicable mode of irrigation for optimizing WUE and nutrient status in tomato leaves in a future freshwater-limited and higher-CO2 environment.

The state of the art on deficit irrigation in soybean

AbstractDeficit irrigation (DI) could be an important strategy to achieve the goal of reducing irrigation water consumption. This review aims to identify the impact of different DI strategies on grain yield, water use efficiency (WUE) and oil and protein content in soybean seeds. A total of 25 articles were considered and then divided into DI throughout the whole cycle (standard deficit irrigation, StDI) and DI only at certain stages of the cycle (regulated deficit irrigation, RDI). In StDI, yield reductions were approximately 20% when the replacement of the crop water requirement was between 70% and 90%. For RDI, yield reductions ranging from 9% to 30% were observed depending on the phenological stage at which the crop evapotranspiration (ETc) deficit was imposed. StDI always increased WUE compared to full irrigation, whereas for RDI, the response in terms of WUE changed considering the stressed phenological stage. Few studies have reported the effects on oil and protein content, showing high variability and contrasting results. In general, the application of a reduced amount of water led to a decrease in yield and an increase in WUE, with a magnitude significantly influenced by the stage at which the stress was imposed.

Modeling fuel moisture dynamics under climate change in Spain’s forests

BackgroundCurrent assessments of the effects of climate change on future wildfire risk are based on either empirical approaches or fire weather indices. No study has yet used process-based models over national scales to understand how and where will increases in climate aridity affect the likelihood of fire activity through changes in the moisture content of live (LFMC) and of dead (DFMC) fuels. Here, we used process-based models to forecast changes in LFMC and DFMC under the 21st century climatic conditions projected from moderate and high greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Predictions were performed across broad productivity gradients in peninsular Spain to understand how productivity mediates the effects of climate change on fuel moisture dynamics.ResultsLFMC and DFMC were predicted to decline under the climatic conditions projected for the coming decades. Increases in the annual frequency of days with fuel moisture content below wildfire occurrence thresholds were predicted to extend fire season lengths by 20 days under RCP4.5 and by 50 days under RCP8.5. The effects of climate change on LFMC and DFMC varied linearly and negatively with productivity (stronger fuel moisture decreases in least productive environments). Although we observed a significant mitigation effect from rising CO2 (via increases in water-use efficiency), it was not enough to offset LFMC declining trends induced by increased temperature and aridity.ConclusionsWe predicted that the warmer and more arid climatic conditions projected for the 21st century will lead to generalized declines in fuel moisture, lengthening fire seasons, and increasing wildfire danger. The use of process-based models to forecast LFMC dynamics allowed the consideration of plant species capabilities to buffer climate change impacts. Significant increases in the fire season length predicted in the most productive environments, currently with large fire return intervals, would pose an increase of fire danger in major Spanish carbon sinks. Finally, the CO2 mitigation effect would not be enough to offset climate change-driven declines in seasonal LFMC levels.