Water-limited Areas Research Articles

Participatory evaluation and demonstration of furrow irrigation systems with full irrigation application on Onion (Allium cepa L.) yield, yield component and water use efficiency at Docha Dembela in Demba Gofa woreda, South Ethiopia

Poor irrigation water management is one of the major factors limiting crop production in Ethiopia. Field experiment was conducted at farmers filed at Docha Dambal kebele in Demba Gofa woreda, Gofa zone, South Ethiopia for two consecutive years (2019 & 2020) to evaluate and demonstrate the effect of furrow irrigation systems on onion yield and water use efficiency. The treatments consisted of three furrow irrigation systems (conventional, alternative and fixed). The irrigation treatments were laid out in randomized complete block design with six replications and participant farmers were used as a replication. Results indicated that highest mean value of marketable bulb yield (27758.2 kg ha-1) was brought under Conventional furrow system. However the lowest mean value of marketable bulb yield was recorded from the fixed furrow system (20482.5). However, Superior water use efficiency of 13.33kg/m3 was recorded from alternative furrow irrigation system. The lowest water use efficiency (7.78 kg/m3) was recorded from the Conventional furrow system. Therefore, It could be concluded that alternate furrow irrigation system maximized water use efficiency of onion with tolerable yield penalty at the study area. This result is important for farmers to irrigate supplemental lands with water saved, thus achieving a more efficient and rational use of land and water resources in the water limited area. If areas with no water scarcity, conventional furrow system could be a potential approach for promoting onion bulb yield under field conditions.

Water limitation regulates positive feedback of increased ecosystem respiration.

Terrestrial ecosystem respiration increases exponentially with temperature, constituting a positive feedback loop accelerating global warming. However, the response of ecosystem respiration to temperature strongly depends on water availability, yet where and when the water effects are important, is presently poorly constrained, introducing uncertainties in climate-carbon cycle feedback projections. Here, we disentangle the effects of temperature and precipitation (a proxy for water availability) on ecosystem respiration by analysing eddy covariance CO2 flux measurements across 212 globally distributed sites. We reveal a threshold precipitation function, determined by the balance between precipitation and ecosystem water demand, which separates temperature-limited and water-limited respiration. Respiration is temperature limited for precipitation above that threshold function, whereas in drier areas water limitation reduces the temperature sensitivity of respiration and its positive feedback to global warming. If the trend of expansion of water-limited areas with warming climate over the last decades continues, the positive feedback of ecosystem respiration is likely to be weakened and counteracted by the increasing water limitation.

Biomass carbon stock and allocation of planted and natural forests in the Loess Plateau of China

Establishing planted forests (PF) by afforestation and naturally regenerating forests (NF) are important measures of enhance carbon (C) sequestration in terrestrial ecosystems. However, the difference of biomass C stocks and allocation between NF and PF and their determinants in water-limited areas remain unclear. To address this gap, we conducted a synthesis of above-ground biomass C (AGBC), below-ground biomass C (BGBC) stocks and root to shoot ratios (R:S) of PF and NF in the Chinese Loess Plateau. The changes in biomass C stock and R:S along a climate gradient were investigated, and the relationships between R:S and soil properties were also quantified. We found that PF exhibited lower AGBC and BGBC stocks compared to NF, but the average R:S in PF was significantly higher than that of NF (0.48 ± 0.27 vs. 0.30 ± 0.11, p < 0.05). Turning points existed in biomass C allocation along climatic gradient for both PF and NF. More biomass C was allocated to AGBC in PF and NF when mean annual precipitation exceeded 494 mm and 588 mm, respectively. Higher mean annual temperature promoted larger C allocations to BGBC in PF compared to NF. Soil properties had a stronger effect on the biomass C allocation patterns after afforestation, but to a lesser extent on NF. This study indicates that afforestation promotes a larger allocation of biomass C into the below-ground compared to naturally regenerated forests, and using the default R:S estimates may result in a severe underestimation of below-ground C stocks in water-limited areas. The biomass C stocks and allocation are collectively determined by climate conditions and soil properties, and accumulated below-ground biomass C stock induced by dryland afforestation may be an important C sink at a broad geographic scale.

Vegetation greening accelerated hydrological drought in two-thirds of river basins over China

Although the vegetation-greening-induced water supply reduction has been widely recognized, little is known about the impacts of vegetation greening on hydrological drought. Here Standardized Water Availability Index (SWAI, based on surface water-balance), driven by evapotranspiration (ET, with vegetation dynamics), was developed to quantify the impacts of vegetation greening on hydrological drought at multiple timescales over China from 1982 to 2015. The ET with vegetation dynamics was modeled by the improved PT-JPL model, and was validated with in-situ observed data from 8 flux tower sites and 4 on-site field experiments (covered with 12 different land-cover types in China). SWAI was also validated with monthly runoff records (from 59 gauging stations over different climatic regimes in China), and proved to effectively capture the response of water surplus/deficit to vegetation dynamics. Results reveal that percentage drought-affected areas increased (increased by 2 % to 9 %) and drought intensity enhanced in two-thirds of Chinese river basins due to vegetation greening. Moreover, in nearly half of the river basins in China, drought duration increased by 0.035–0.131 months, and drought frequency increased by 0.016–0.085 months/34-year. Hydrological drought accelerated by vegetation greening mainly occurred in arid and semi-arid river basins (water-limited areas), while it was not obvious in humid and sub-humid river basins due to limited energy for ET in these areas. Our work and findings provide new insights for understanding the vegetation-induced water resource shortage and have potential applications for government and water managers to timely monitor and assess the balance between ecological restoration and water resources.

Impacts of Deep-Rooted Apple Tree on Soil Water Balance in the Semi-Arid Loess Plateau, China

Partitioning soil water balance (SWB) is an effective approach for deciphering the impacts of vegetation change on soil hydrological processes. Growing apple trees on the Loess Plateau, China, leads to a substantial deep soil water deficit, posing a serious threat to the sustainable development of apple production. However, the impact of deep-rooted apple trees on SWB remains poorly understood. In this study, we conducted a “Paired Plot” experiment to achieve this objective by decoupling SWB components using water stable isotopes, tritium, and soil water contents from deep soil cores (up to 25 m) under apple orchards with a stand age gradient of 8–23 years. The results showed that deep soil water storage under apple orchards was notably reduced compared to nearby farmland, showing a stand age-related pattern of deep soil water deficit (R2 = 0.91). By analyzing the changing patterns of SWB components, we found that the main factor driving this deficit is the water uptake process controlled by the deep root system. This process is triggered by the increased transpiration demand of apple trees and short-term water scarcity. These findings have implications for understanding soil water dynamics, sustainable agroforestry management, and soil water resources’ protection in this region and other similar water-limited areas.

Light thinning effectively improves forest soil water replenishment in water-limited areas: Observational evidence from Robinia pseudoacacia plantations on the Loess Plateau, China

Soil water plays a key role in vegetation growth and recovery, mainly replenished by rainfall in the water-limited areas. Thinning is an important practice for forest reconstruction and soil water regulation. However, the effects of different thinning intensities on the dynamics of soil water and its replenishment by rainfall have been inadequately quantified, which could provide a guide for reasonable thinning intensity determination for in high-density forests from a hydrological perspective. In this study, one nonthinning plot and 5 plots with different thinning intensities, i.e., 35 % (light), 45 % (medium), 55 % (moderate), 65 % (heavy) and 80 % (extremely heavy) in Robinia pseudoacacia plantations, which are widely planted on the Loess Plateau, were set up. The volumetric soil water content (SWC) at 0–200 cm depths and rainfall were observed simultaneously and continuously for up to two years. The soil properties and vegetation structure in each plot were also measured regularly. The results showed that (1) the SWC in all the thinning plots was significantly greater than that in the nonthining plot (P < 0.05). (2) The replenishment increased with increasing thinning intensity, and then decreased after reaching a maximum at T35 % under most rainfall events except for light events. (3) The variations in the soil water response characteristics among the plots with different thinning intensities were mainly significantly correlated with the initial soil water content (ISWC), leaf area index (LAI) and understorey vegetation characteristics (P < 0.05). (4) Based on the relationship between soil water replenishment and retention with thinning intensity and stand density, quantitative equations were fitted to determine the reasonable thinning intensity (22–28 %) and retained stand density (1019–1091 trees/ha), respectively. Our study concluded that thinning could effectively improve soil water, especially light thinning, which could obviously enhance the replenishment of soil water by rainfall in Robinia pseudoacacia plantations. This study can provide a reference for determining forest thinning intensity or stand retention density, which is beneficial for water and reforestation management in water-limited regions.

The dimensions of deep-layer soil desiccation and its impact on xylem hydraulic conductivity in dryland tree plantations

Abstract. In water-limited areas, planted trees can extract substantial amounts of soil water from deep layers (&gt; 200 cm) to meet their high water demand, resulting in deep soil desiccation, which influences not only regional water cycling but also the sustainability of trees per se in drylands. However, the specific dimensions of deep soil desiccation in relation to both the soil moisture limitation and the maximum root water uptake (RWU) depth are still not well determined. Whether the dimensions depend on tree species and how they will affect trees' xylem hydraulic conductivity are also unclear, restricting our ability to predict the fate of dryland tree plantations. Therefore, we studied the spatiotemporal distribution of deep soil moisture deficit (DSMD) for two typical planted trees, apple (Malus pumila Mill.) and black locust (Robinia pseudoacacia L.), based on published data and multiple field samplings on China's Loess Plateau. The results indicated that the lowest deep soil moisture (DSM; units of gravimetric percent, i.e., grav-%) occurred under the planted trees aged 24–28 years at all sites. The lowest DSMD varied around −0.6, which was close to the DSMD at the permanent wilting point (PWP, grav-%), regardless of tree species and site, although shallow (&lt; 200 cm) soil moisture was not reduced to the point of limitation. This suggests that PWP is a reliable indicator of the moisture limitation of deep-layer soil desiccation for the tree species examined. The corresponding depth of soil moisture use reached 18.0–22.0 m for these old planted trees at different sites, while it was more than 25 m for R. pseudoacacia in the drier site of Mizhi. Furthermore, the mean values of native percentage loss of hydraulic conductivity of planted trees' branches xylem reached 74.9 %–96.5 % in the plantations sampled in this study, indicating that tree mortality may occur. The findings help predict the sustainability of planted trees in semi-arid regions with a thick vadose zone.

Vegetation dynamics regulate baseflow seasonal patterns of the Chaohe watershed in North China

Study regionThe Chaohe watershed is Beijing's primary potable water source. Study focusThe initiation of ecological restoration (ER), combined with the rapid acceleration of climate change (CC), has precipitated severe water shortages in North China. The seasonal responses of baseflow (BF), pivotal for sustaining rivers' fundamental flow and ecological equilibrium, to ER and CC are poorly understood. This study provides a precise depiction of the seasonal variations in BF by leveraging multiple separation methodologies. By applying the BFAST algorithm and a comprehensive sensitivity analysis, we unveil the nuanced seasonal patterns of BF adjustments in reaction to ER and CC. New hydrological insights for the regionBaseflow, primarily influenced by the wet season, constituted 64.21% of the annual aggregate. Considerable decreases in BF during the dry (−32.61%) and wet (−68.21%) seasons pose increasing threats to available water resources. The decrease in sub-surface runoff (−1.91 mm per decade) dominated the reduction of dry season BF. Indeed, vegetation regulated seasonal water distribution, maintaining the essential flow throughout the dry season. In the wet season, the reduction in BF acts as a supplemental water source to fulfill the escalating evapotranspiration needs due to afforestation and a drying climate. This study highlights the persistent hydrological consequences of ER and CC on water resources, emphasizing the crucial function of vegetation in baseflow, a key component for ecological restoration and water resource management in water-limited areas.

Partial root-zone drying subsurface drip irrigation increased the alfalfa quality yield but decreased the alfalfa quality content.

Water shortage seriously restricts the development of grassland agriculture in arid land and dramatically impacts alfalfa (Medicago sativa L.) quality content and hay yield. Reasonable irrigation methods have the potential to enhance the alfalfa quality content, hay yield, and thus quality yield. Whether partial root-zone drying subsurface drip irrigation (PRDSDI) improves the alfalfa quality yield, quality content, and hay yield is still unknown compared with conventional subsurface drip irrigation (CSDI). The effects of PRDSDI compared with that of CSDI and the interaction with irrigation volume (10 mm/week, 20 mm/week, and 30 mm/week) on the alfalfa quality yield were investigated in 2017-2018 and explained the change in quality yield with the alfalfa quality content and hay yield. Here, the results showed that PRDSDI did not increase the alfalfa quality yield in 2 years. PRDSDI significantly increased acid detergent fiber by 13.3% and 12.2% in 2018 with 10-mm and 20-mm irrigation volumes and neutral detergent fiber by 16.2%, 13.2%, and 12.6% in 2017 with 10-mm, 20-mm, and 30-mm irrigation volumes, respectively. PRDSDI significantly decreased the crude protein by 5.4% and 8.4% in 2018 with 10-mm and 20-mm irrigation volumes and relative feed value by 15.0% with 20-mm irrigation volume in 2017 and 9.8% with 10-mm irrigation volume in 2018, respectively. In addition, PRDSDI significantly increased the alfalfa average hay yield by 49.5% and 59.6% with 10-mm and 20-mm irrigation volumes in 2018, respectively. Our results provide a counterexample for PRDSDI to improve crop quality. Although there was no significant improvement in average quality yield by PRDSDI, the positive impact of average hay yield on quality yield outweighed the negative impact of quality content. Thus, it has the potential to improve quality yields. The novel findings regarding the effects of PRDSDI on quality yield are potentially favorable for the forage feed value in water-limited areas.

Aging Mongolian pine plantations face high risks of drought-induced growth decline: evidence from both individual tree and forest stand measurements

Discerning vulnerability differences among different aged trees to drought-driven growth decline or to mortality is critical to implement age-specific countermeasures for forest management in water-limited areas. An important species for afforestation in dry environments of northern China, Mongolian pine (Pinus sylvestris var. mongolica Litv.) has recently exhibited growth decline and dieback on many sites, particularly pronounced in old-growth plantations. However, changes in response to drought stress by this species with age as well as the underlying mechanisms are poorly understood. In this study, tree-ring data and remotely sensed vegetation data were combined to investigate variations in growth at individual tree and stand scales for young (9 − 13 years) and aging (35 − 52 years) plantations of Mongolian pine in a water-limited area of northern China. A recent decline in tree-ring width in the older plantation also had lower values in satellited-derived normalized difference vegetation indices and normalized difference water indices relative to the younger plantations. In addition, all measured growth-related metrics were strongly correlated with the self-calibrating Palmer drought severity index during the growing season in the older plantation. Sensitivity of growth to drought of the older plantation might be attributed to more severe hydraulic limitations, as reflected by their lower sapwood- and leaf-specific hydraulic conductivities. Our study presents a comprehensive view on changes of growth with age by integrating multiple methods and provides an explanation from the perspective of plant hydraulics for growth decline with age. The results indicate that old-growth Mongolian pine plantations in water-limited environments may face increased growth declines under the context of climate warming and drying.

Evaluation of Deficit Irrigation on Potato Yield and Water use Efficiency in Gedeo Zone, South Region

Increased water scarcity necessitates the implementation of water-conserving irrigation management practices tosustain crop production, especially in water-limited areas. A two-year field study was conducted during 2020 and 2021 to evaluate the effect of deficit irrigation on potato yield and water use efficiency. The experiment was conducted in randomized complete block design with four irrigation levels (100% ETc (crop evapotranspiration), 85% ETc, 70% ETc, and 55%ETc). The results showed that, deficit irrigation level have a significant difference in number of tuber per plant, marketable, total yield and water use efficiency. Potato yield significantly reduced with deficit irrigation level. Next to full irrigation the maximum yield was obtained under 85% ETc and 70%ETc with better crop and irrigation water use efficiency. Maximum crop and irrigation water use efficiency was obtained under 55% ETc. The partial budget analysis showed that the maximum acceptable MRR was obtained from 70%ETc and the highest net benefit was obtained under full irrigation. Therefore, in area where sufficient amount of water is available full irrigation is recommended to obtain maximum yield, but in water scarce area applying 85%ETcand 70%ETc is recommended with 17.5% and 23.2% yield reduction respectively with acceptable economical benefit.

Aquaponics: A Sustainable Path to Food Sovereignty and Enhanced Water Use Efficiency

This comprehensive review explores aquaponics as an environmentally friendly solution aligned with SDGs and food sovereignty, assessing various aspects from system design to automation, and weighing social, economic, and environmental benefits through literature and case studies. However, challenges persist in obtaining organic certification and legislative recognition, hindering its growth. Achieving remarkable water use efficiency, up to 90%, relies on adaptable fish species like Nile tilapia and carp. Nutrient-rich fish feeds notably benefit low-nutrient-demanding greens. Ensuring water quality and efficient nitrification are pivotal, supported by IoT systems. Despite its efficiency, integrating Industry 4.0 involves complexity and cost barriers, necessitating ongoing innovation. Economies of scale and supportive horticultural policies can bolster its viability. Aquaponics, known for its efficiency in enhancing crop yields while minimizing water use and waste, is expanding globally, especially in water-scarce regions. Aquaponics, pioneered by the University of the Virgin Islands, is expanding in Europe, notably in Spain, Denmark, Italy, and Germany. Asia and Africa also recognize its potential for sustainable food production, especially in water-limited areas. While it offers fresh produce and cost savings, challenges arise in scaling up, managing water quality, and meeting energy demands, particularly for indoor systems. Egypt’s interest in desert and coastal regions highlights aquaponics’ eco-friendly food production potential. Despite the associated high costs, there is a quest for practical and affordable designs for everyday integration. Research in arid regions and industry advancements are crucial for aquaponics’ global food production potential. Deeper exploration of intelligent systems and automation, particularly in large-scale setups, is essential, highlighting the industry’s promise. Practical application, driven by ongoing research and local adaptations, is a key to fully harnessing aquaponics for sustainable food production worldwide.

Manfaat Irigasi Springkler pada Lahan Fasum untuk Peningkatan Produksi Pertanian Kampung Tangguh Poharin

This community service is the result of research in 2022 which will be poured on community service on the fasum land in Pondok Harapan Indah housing, Jalan Sigura-Gura Malang. Installation of pipes and sprinkler nozzles based on distance and height according to the type of plant that exists. With the potential for water sources and limited land area, farmers' businesses are expected to be able to utilize water efficiently. The sprinkler irrigation system is thought to be an alternative in the provision of irrigation and for this reason it is necessary to test the ability of the irrigation system to vary the distance between the sprinklers and the high sticks to the irrigation radius and its uniformity within a few minutes duration. For a stick height of 1 m with the same sprinkler spacing, a uniformity coefficient of less than 80% is obtained and the optimal irrigation radius is with an average spacing of 6 meters

Water-use characteristics of Syzygium antisepticum and Adinandra integerrima in a secondary forest of Khao Yai National Park in Thailand with implications for environmental management.

Southeast Asia has experienced widespread deforestation and change in land use. Consequently, many reforestation projects have been initiated in this region. However, it is imperative to carefully choose the tree species for planting, especially in light of the increasing climate variability and the potential alteration of plantation on the watershed water balance. Thus, the information regarding water-use characteristics of various tree species and sizes is critical in the tree species selection for reforestation. We estimated tree water use (T) of dominant species including Syzygium antisepticum and Adinandra integerrima, hereafter Sa and Ai, respectively, in a secondary tropical forest in Khao Yai National Park, Thailand, using sap flow data, and compared T between species and size classes. Additionally, we evaluated the responses of T of both species in each size class to environmental factors including soil moisture and vapor pressure deficit (VPD). Results showed consistently higher T in Sa compared to Ai across ranges of VPD and soil moisture. Under low soil moisture, T of Sa responded to VPD, following a saturating exponential pattern while Ai maintained T across different VPD levels, irrespective of tree size. No responses of T to VPD were observed in either species when soil water was moderate. When soil moisture was high, T of both species significantly increased and saturated at high VPD, albeit the responses were less sensitive in large trees. Our results imply that Ai may be suitable for reforestation in water-limited areas where droughts frequently occur to minimize reforestation impact on water availability to downstream ecosystems. In contrast, Sa should be planted in regions with abundant and reliable water resources. However, a mixed species plantation should be generally considered to increase forest resilience to increasing climate variation.

Belowground C sequestrations response to grazing exclusion in global grasslands: Dynamics and mechanisms

Globally, grazing exclusion is a widely implemented management strategy for restoring degraded grassland ecosystems and sequestering carbon (C). However, there is limited understanding regarding the temporal responses and underlying factors influencing ecosystem C stocks following grazing exclusion. In this study, we conducted a comprehensive synthesis of data from 199 independent experiments (454 pairwise observations) to analyze responses of plant and soil C stocks to grazing exclusion across four distinct grassland ecosystems (desert, typical, meadow, and alpine) in the globe. We found that rates of change in plant biomass C stocks and soil organic C stocks exponentially or rationally decreased with years since enclosure. Grazing exclusion generally enhanced aboveground biomass C in plants, while its effects on C stocks of belowground biomass and soil were more contingent upon various factors, such as climate, initial levels of C stocks, and grazing exclusion duration. Furthermore, the responses of C stocks of plant biomass and soil to livestock grazing cessation tend to stabilize over time, with equilibrium typically reaching after approximately 40 years, while soil C sequestration responses exhibited a lagged pattern compared to plant biomass C. Our results underscored the effectiveness of grazing exclusion as an effective strategy to enhance C stocks in regions characterized by low C content and non-water limited conditions. We propose that grazing exclusion for 1–5 years was the best restoration time for typical, meadow and alpine grasslands. Given the limited effects of grazing exclusion on soil organic C stocks of desert types, grazing exclusion might not be an effective measure to increase the soil organic C stocks in water-limited areas like desert grasslands.

Distinguishing the effects of climate change and vegetation greening on soil moisture variability along aridity gradient in the drylands of northern China

Drylands are particularly sensitive to climate change, and soil water availability is critical for dryland ecosystems. Climate change and large-scale ecological restoration have led to significant vegetation greening and soil moisture (SM) variations in the drylands. However, the influencing mechanisms of climate change and vegetation greening on SM variability were not well understood. In this study, the spatiotemporal variations of climate variables, vegetation cover, surface SM (SM_surf) and root-zone SM (SM_root) along aridity gradient in the drylands of northern China during 1981–2018 were investigated. The random forest model and partial least-squares structural equation modelling (PLS-SEM) analysis were employed to quantify the contributions of climate change and vegetation greening to SM variability and identify the influencing pathways. The climate change showed temporal trends of wetting to drying before 2000 and drying to more wetting in 2000–2018, and vegetation greening was significant in 2000–2018. The variations of SM displayed obvious east-negative and west-positive trends. The temporal trend of SM deficit decreased during 1981–2018 in most regions, and SM showed a significant increasing trend in all regions of different aridity gradient after 2000. The correlations of climate factors and vegetation cover with SM became stronger in the area with lower aridity. The vegetation greening-induced SM change was limited compared to climate change. The climate factors can directly impact SM availability, and also indirectly influence SM availability through vegetation (e.g., precipitation→LAI→SM_surf). The SM_surf had positive responses to vegetation greening, especially in semiarid subarea. In contrast, vegetation greening exacerbated SM_root consumption in semiarid and dry subhumid subareas, which became intensive after 2000. This study fills the knowledge gap in the underlying reasons for the variations of both surface and root zone SM in water-limited areas and reveals the potential risks of SM depletion, particularly in dry subhumid areas.

Simulating the effects of vegetation restoration and climate change on the long-term soil water balance on the Loess Plateau, 2021–2050

In water-limited areas, soil water content (SWC) is a critical factor for plant growth and ecosystem stability. To understand the long-term effects of three different land uses (Vigna radiata: VR, Stipa bungeana: SB, and Medicago sativa: MS) and two climate scenarios (representative concentration pathway 4.5 (RCP45) and nonclimate change (Non_CC)) on water budgets and the mechanisms of dried soil layer (DSL) formation, a new complete multilayered model, OpenKarHydro, was developed. The results showed that the model adequately captured the water budget for different land uses, with root mean square errors (RMSEs) of 0.058, 0.046, and 0.046 and coefficients of determination (R2) of 0.615, 0.605, and 0.582, respectively, for SWC dynamics. This model performance was also demonstrated by the verification of runoff. Sensitivity analysis indicated that the soil porosity (n) was the most sensitive parameter in all land uses. The DSL was primarily caused by higher evapotranspiration (VR: 83.16% vs. 82.48%, SB: 80.62% vs. 77.69%, and MS: 79.93% vs. 76.26%) and canopy interception (VR: 11.92% vs. 11.99%, SB: 17.56% vs. 23.15% and MS: 22.60% vs. 26.19%) in the Non_CC climate pattern than in the RCP45 climate pattern. Climate change has caused an increase in evapotranspiration and interception for all land uses, reducing bottom leakage. Rainfall is sufficient to meet the water demand in the VR plot regardless of climate change; however, the additional water consumption caused by climate warming cannot be offset by the increased rainfall for the SB and MS plots. Compared to Non_CC, RCP45 resulted in increases of 0%, 54.19%, and 57.62% in proportion with extreme drought and decreases of 4.70%, 38.74%, and 5.24% in proportion with no drought for the soil profiles of VR, SB, and MS, respectively. For MS, RCP45 (2026) caused the DSL to penetrate the soil profile (>400 cm) 4 years earlier than in the Non_CC (2030), which should take no more than 5 and 9 years, respectively. OpenKarHydro is a useful tool for optimal water resource management and ecological restoration in water-limited areas.

Integrated hydroponics systems with anaerobic supernatant and aquaculture effluent in desert regions: Nutrient recovery and benefit analysis

Hydroponics is a resource-efficient system that increases food production and enhances the overall sustainability of agricultural systems, particularly in arid zones with prevalent water scarcity and limited areas of arable land. This study investigated zero-waste hydroponics systems fed by agricultural waste streams as nutrient sources under desert conditions. Three pilot-scale systems were tested and compared. The first hydroponics system (“HPAP”) received its nutrient source internally from an aquaponic system, including supernatant from the anaerobic digestion of fish sludge. The second system (“HPAD”) was sourced by the supernatant of plant waste anaerobic digestion, and the third served as a control that was fed by commercial Hoagland solution (“HPHS”). Fresh weight production was similar in all treatments, ranging from 488 to 539 g per shoot, corresponding to 5.7 to 6.0 kg total wet weight per m2. The recovery of N and P from wastes and their subsequent uptake by plants was highly efficient, with rates of 77 % for N and 65 % for P. Plants that were fed using supernatants demonstrated slightly higher plant quality compared with those grown in Hoagland solution. Over the duration of the full study (3 months), water was only used to compensate for evapotranspiration, corresponding to ~10 L per kg of lettuce. The potential health risk for heavy metals was negligible, as assessed using the health-risk index (HRI < 1) and targeted hazardous quotient (THQ < 1). The results of this study demonstrate that careful management can significantly reduce pollution, increase the recovery of nutrients and water, and improve hydroponics production.

Long-term straw mulch underpins crop yield and improves soil quality more efficiently than plastic mulch in different maize and wheat systems

Field mulching efficiently increases crop production, yet the feasibilities of plastic mulch (PM) and straw mulch (SM) in different ecological regions are scarcely documented. This study aimed to investigate yield responses and soil quality changes following PM and SM, thereby identifying their suitability in different maize and wheat systems. A total of 202 peer-reviewed publications after 2000 that involved field experiments treated with no-mulch, PM, and SM were collected, and yield ratio of PM to SM (RPM/SM) was calculated to quantitatively understand their mulching efficacy. PM significantly increased grain yields in mono rather than double-cropping systems relative to SM, with an averaged RPM/SM at 1.28 in mono-maize, 1.11 in mono-wheat, and 1.05 for maize and 1.04 for wheat in double-cropping systems. Growing-season precipitation was significantly correlated with RPM/SM across mono and double-cropping systems, showing an RPM/SM of 1 at 530-mm for wheat in mono-cropping and 395-mm in double-cropping, and a stabilized RPM/SM observed at 1.082 in mono-cropping and 1.001 in double-cropping for maize, when growing-season precipitation exceeded 576-mm and 500-mm, respectively. Long-term field experiments illustrated significant relationships between RPM/SM and experimental duration, showing an RPM/SM of 1 at the 10.3-year for mono-maize, and 14.6-year for maize and 16.7-year for wheat in double-cropping, and a stabilized RPM/SM of 1.075 when trial time exceeded 3.7 years for mono-wheat, indicating a logged better performance of agronomic yield for SM. Owing to remarkable increases of soil organic C (SOC), total N, available K, and microbial biomass C, SM received the highest soil quality index across mono- and double-cropping systems, compared with PM and no-mulch. Growing-season precipitation, soil moisture at the sowing stage, SOC, and total N are the vital climatic and physicochemical variables mediating RPM/SM regardless of mono and double-cropping systems. Long-term SM rather than PM is an alternative for addressing the triple challenges of food security, soil degradation, and environmental mitigation. Quantifying the mulching efficacy on crop yields in different maize and wheat systems contributes to underpinning soil fertility and productivity in water-limited areas.

Thinning effectively mitigates the decline of aging Mongolian pine plantations by alleviating drought stress and enhancing plant carbon balance

Intensifying drought around the globe poses strong challenges to the growth and survival of trees, emphasizing the urgency of understanding the physiological mechanisms of drought-induced tree decline and mortality and the necessity of using silvicultural approaches to mitigate drought effects on tree growth. We experimentally explored whether thinning enhances tree growth vigor and drought resilience in early aging Mongolian pine (Pinus sylvestris var. mongolica Litv.) plantations in a water-limited area of Northeast China using dendrochronological methods. Meanwhile, we compared plant hydraulic traits, water relations, and non-structural carbohydrate concentrations between trees growing in the thinned and un-thinned stands with the aim of unraveling the physiological mechanisms underlying the density effects on tree growth performance. The results showed that basal area increments of Mongolian pine trees in the high-density plantations started to decline continuously at tree cambium age of around 15 years over about a decade, while thinning effectively reversed their growth decline. Trees in thinned stands exhibited significantly higher predawn leaf water potentials, higher stem hydraulic conductivities, and larger carbon reserves than trees in un-thinned stands. Although trees growing in high-density stands maintained as low risks of xylem hydraulic dysfunction as trees growing in low-density stands, that was at the cost of substantially reducing tree crown size through branch mortality that unavoidably undermined their carbon balance at the whole-plant level. Consistently, trees growing in the thinned low-density stands showed significantly higher levels of non-structural carbohydrate reserve in stems and enhanced growth resilience to extreme drought than trees growing in the high-density reference stands. Our results suggest that thinning can effectively enhance xylem hydraulic transport efficiency and reduce the risk of carbon imbalance by increasing soil water availability and hence mitigates the early aging of Mongolian pine plantations in water-limited environments.