Study region: 15 catchments in the Chinese Loess Plateau (CLP) Study focus: In catchment-scale hydrological processes, both precipitation and potential evapotranspiration play dominant roles, while all relevant factors from the land surface to the atmosphere are coupled together to play a regulating role. The Budyko-based and orthogonality-based graphical attribution methods (BGA and OGA, respectively) visually separate the direct effect of dryness index (& empty;) and the regulating effect of land-atmosphere system. This study identified the limitations of OGA in its path section and accuracy, explored its essential difference from the wellestablished BGA, and proposed a more appropriate graphical attribution method in the waterenergy partitioning (WEP) space. Finally, the proposed method was applied to attribute runoff change for 15 CLP catchments. New hydrological insights for the region: The orthogonality-induced linearization in OGA may fail to capture nonlinear Budyko relationships, potentially leading to violations of the water and energy boundaries. By mapping Budyko curves in the WEP space, we elucidated the inconsistencies between OGA and BGA in both decomposition orders and paths, and proposed the two-path BGA as a more appropriate attribution framework in the WEP space. The improved method uncovered that, on average, the direct effect of & empty; and the regulating effect of land-atmosphere system contributed 18 % and 82 %, respectively, to runoff change for 15 CLP catchments. This study contributes to the advancement of hydrological change attribution methods.

Water stress poses an escalating threat to wheat (Triticum aestivum L.), often inducing oxidative damage in plants and deteriorating soil properties. While organic amendments can mitigate these effects, their comparative efficacy in enhancing drought resilience remains insufficiently explored. A pot experiment was conducted using a completely randomized design under a factorial arrangement (two factors) with three replicates. We evaluated four amendments including farmyard manure, organic waste compost, vermicompost, and biochar under three soil moisture regimes (50%, 75%, and 100% field capacity). Severe water stress (50% FC) significantly reduced soil moisture, root growth, nutrient uptake, and yield. Vermicompost combined with 100% FC emerged as the most effective amendment, enhancing drought resilience through a dual mechanism: it acted as a biostimulant, strengthening the plant's antioxidant defense system to reduce oxidative stress, and as a soil conditioner, improving soil organic matter, water contents and aggregate stability. This synergistic enhancement in soil-plant interaction led to better root growth, nutrient uptake, and yield stability under water stress. Our findings highlight the potential of vermicompost as a promising amendment for developing more drought-resilient wheat cultivation systems, a premise that warrants further validation under field conditions.

Terrace sidewalls represent a critical yet frequently overlooked pathway for lateral vapor loss in semi-arid landscapes. While traditional land surface models primarily focus on vertical evapotranspiration, they often neglect the three-dimensional (3D) nature of topographic evaporative interfaces. To address this gap in understanding, we conducted a three-year (2023-2025) in-situ monitoring campaign in typical terraced fields on the Chinese Loess Plateau, utilizing spatial neutron probe transects to capture deep-profile (0-300 cm) soil moisture dynamics. We employed a coupled statistical framework, integrating Random Forest (RF) to rank non-linear environmental drivers and Structural Equation Modeling (SEM) to disentangle causal mechanisms. We demonstrate that sidewall evaporation drives a persistent moisture gradient extending 450 cm, causing a 30 % cumulative water deficit compared to the unaffected reference area (D600); notably, >70 % of this loss occurs within 150 cm of the edge. RF analysis identified horizontal distance (26.9 %) as the primary driver, surpassing soil depth. SEM further revealed the mechanism: the sidewall functions as an "evaporative pump," where synergistic solar radiation and topography-induced aerodynamic turbulence maintain a steep vapor pressure gradient, extracting deep soil moisture. This process establishes a distinct geomorphologically induced permanent moisture deficit zone characterized by low temporal stability. Consequently, we propose a paradigm shift from a 2D planar view to a 3D interface-based framework to accurately capture land-atmosphere water exchanges in complex terraced terrains.

The Loess Plateau (LP) ecosystems are expected to play an important role in achieving the national carbon neutrality goals. However, significant uncertainty remains in assessing the spatiotemporal dynamics of carbon sequestration rates (CSRs) in regional terrestrial ecosystems. Here, we integrated large amounts of field-plot data and models (forest carbon sequestration model and machine learning models) to systematically explore the CSR of terrestrial ecosystems over the LP from 1980 to 2060 under three climate scenarios. Results showed that an increase of 2.62 +/- 0.43 Pg C for terrestrial ecosystems over the LP during 1980-2060, with 1.98 +/- 0.31 Pg C and 0.64 +/- 0.13 Pg C in vegetation and soil, respectively, representing an increase of 54.60%. The CSR of forests, shrublands, grasslands, and croplands over the LP were estimated to be 36.63 +/- 6.96, 0.09 +/- 0.01,-7.74 +/- 1.13, and 3.81 +/- 0.66 Tg C yr-1, respectively. Between 1980 and 2060, the ecosystem CSR (ECSR) over the LP ranged from 9.62 to 64.45 Tg C yr-1, with an average of 32.78 +/- 6.79 Tg C yr-1. The ECSR will be peaking during 2040-2050 before decreasing. Our findings provide comprehensive picture of the spatiotemporal dynamic trajectory of CSR over the LP and can be used to inform future policymaking to achieve regional carbon neutrality.

Study region: The loess tableland region, China. Study focus: A decade-long (2014-2023) investigation assessed soil water content (SWC) dynamics across four rainfed farmlands (Alfalfa field, AF; Fertilized cropland, FC; Unfertilized cropland, UC; Fallow field, FF) to clarify post-drought soil water replenishment. Using the Standardized Precipitation Index (SPI), three extreme drought-rewetting events (WE1: 93.6 mm, WE2: 47.4 mm, WE3: 131.2 mm) representing precipitation gradients were identified. New hydrological insights for the region: Soil water response varied significantly with land use and rainfall intensity. Recharge depths differed notably: during WE1, the depths reached 100 cm for AF, FF, and UC, but only 50 cm for FC, with corresponding Delta SWC increments of 5.3%, 6.4%, 8.1%, and 3.7%, respectively. In WE2, the depths for AF, FF, and UC reached 120 cm versus FC's 100 cm. During WE3, FF achieved 260 cm, while AF and FC remained at 100 cm. Precipitation storage efficiency (PSE) peaked in FF (WE1, 48.2%) and AF (WE2, 80.9%; WE3, 56.3%), showing a nonlinear relationship with precipitation linked to antecedent soil water content (ASWC). Daily precipitation and duration governed wetting duration and front uniformity; FC exhibited the longest duration (12 days) under low-intensity, long-duration rainfall. These findings elucidate soil water dynamics during extreme climate events, aiding disaster forecasting in rain-fed agricultural regions.

The generalized proportionality hypothesis (GPH) highlights the competitive relationships among hydrological components as precipitation (P) transforms into runoff (Q) and evapotranspiration (E), providing a novel perspective on E partitioning that differs from the traditional physical source-based approach. To achieve sequential partitioning of E into initial (Ei) and continuing (Ec) evapotranspiration under the GPH, a P-Q relationship-based Ei estimation method was proposed for the Model Parameter Estimation Experiment (MOPEX) catchments. On this basis, we analyzed the relationship between the GPH-based E components and the physical source-based ones separated by the Penman-Monteith-Mu algorithm. Additionally, we explored the differences between the calculated and inverse Budyko-WT model parameter (Ei/E) and discussed the implications for the Budyko framework. The results showed the following: (1) A significant linear P-Q relationship (p < 0.05) prevailed in the MOPEX catchments, providing a robust data foundation for Ei estimation. Across the MOPEX catchments, Ei and Ec contributed 73% and 27% of total E, respectively. (2) The combined proportion of evaporation from canopy interception and wet soil averaged about 25%, and it was much lower than that of Ei, indicating that it was difficult to establish a connection between Ei and the physical source-based E components. (3) The potential evapotranspiration (EP) satisfying the Budyko-WT model was strictly constrained by the GPH, while the inappropriate EP estimation method largely explained the discrepancy between the calculated and inverse Ei/E. This study deepens the knowledge of the sequential partitioning of E components, uncovers the discrepancies between different E partitioning frameworks, and provides new insights into the characterization of key variables in Budyko models.

Precipitation-driven water scarcity imposes a critical constraint on sustainable development in the Chinese Loess Plateau, where the development of desiccated soil layers (DSLs) through persistent soil water deficits has emerged as a major ecological stressor. Although previous studies have extensively characterized the dynamics of DSLs in reforested ecosystems, the mechanisms underlying their formation in agroecosystems remain not fully elucidated. Soil water dynamics throughout 0-300 cm soil profiles under a winter wheat (Triticum aestivum L.)-winter wheat-spring maize (Zea mays L.) rotation system (2003-2022) were systematically investigated using high-resolution monitoring data. The Soil Desiccation Index (SDI) was employed to quantified desiccation severity and evaluate interactions between precipitation variability and cropping patterns. Key findings revealed four primary thematic takeaways:1) Significant interannual fluctuations in soil water storage (SWS: 382.7-924.7 mm), with pronounced seasonal variability (minimum: 560.6 mm in June; maximum: 690.6 mm in October); 2) Drought memory effects dominated interannual dynamics-SDI exceeded 75 % during drought/ post-drought years, sustaining strongly/extremely desiccated layers (>8 months), yet all DSLs fully recovered following >= 2 consecutive wet years. Non-desiccated layers dominated observations in wet (72 %), normal (65 %), and drought years (49 %), reflecting precipitation-dependent water availability. 3) Deep soil desiccation (>200 cm) showed heightened sensitivity to antecedent precipitation deficits, with SDI-precipitation correlations intensifying with depth (r2 =-0.21 at 60-100 cm;-0.41 at 120-200 cm;-0.54 at 220-300 cm; p < 0.01). 4) Spring maize cultivation outperformed winter wheat in soil water retention, particularly during June-September. These findings reveal the intervention mechanisms of cropping pattern adjustments on soil water resilience, clarify the hysteresis response patterns of deep soil drying to precipitation deficits, and enhance the theoretical framework of soil water resilience in semiarid regions.

Abstract. Potential evapotranspiration (EP) is one of input variables in the Budyko framework, yet the diverse estimation methods cause discrepancies in its values. This raises a question about whether there exists a kind of EP specially satisfying the Budyko framework. Based on the relationships among variables in the Budyko models and the deterministic value of EP with known mean annual precipitation and runoff, we uncover the characteristics of EP and its estimation method from hydrological observation in the Budyko framework. Accordingly, we introduce the concept of Budyko EP. The non-parametric and parametric Budyko equations correspond to the reference and the adjustable Budyko EP, respectively. For the Model Parameter Estimation Experiment catchments, the reference Budyko EP is higher in the central and southern contiguous United States and lower in the northeastern and northwestern regions. The linear conversion functions are established from the meteorological EP to the reference and optimized adjustable Budyko EP separately. When estimating actual evapotranspiration (E) by Budyko models with the same data resources, employing two conversion functions with the meteorological EP reduces the mean absolute error of E estimation by 33 % and 35 %, respectively, compared to using the optimized Budyko model parameter with the meteorological EP. Further investigation suggests that the complementary relationship for evapotranspiration is one factor affecting the expression of the region-specific conversion function. Future in-depth exploration of the spatiotemporal differences in conversion functions will advance E estimation and the applications of Budyko EP.

Study region: 15 catchments in the Chinese Loess Plateau (CLP) Study focus: The concept of the water year has been widely used in analyzing the coupled water- energy balance at the annual scale. However, a comprehensive quantitative investigation about its determination and usability in catchment water balance analysis remains absent. Leveraging long-term hydrometeorological observations and terrestrial water storage (TWS) data, we ascertained the commencement month of the water year for 15 catchments in the CLP and explored the feasibility of the Budyko framework at the water year scale concerning evapotranspiration (ET) estimation and its change attribution. New hydrological insights for the region: (1) TWS recharge commenced predominately in July, with the minimal TWS variation (Delta S) consistently observed for years starting from July. Consequently, July marked the start of the water year for CLP catchments. (2) Disregarding Delta S at the calendar year scale caused significant errors in estimating ET (MAE = 51.16 mm yr-1 ), while the MAE decreased by 35.40% at the water year scale. (3) The relative contributions of precipitation (P), potential evapotranspiration (ET0), and w to ET change deviated significantly from the actual values when ignoring Delta S at the calendar year scale. Conversely, these contributions aligned closely with actual values at the water year scale. Overall, the improved accuracy in ET estimation and enhanced consistency in ET change attribution results collectively justify the water year temporal framework.

Shrubification of grasslands is becoming more severe due to both climate change and human activity. Nevertheless, it is still unclear how the organic acids (OAs) released by invasive plants' roots affect the conversion of carbon (C) and nitrogen (N) in soil. Lonicera thibetica-infested shrubified grassland soil on the eastern Qinghai-Tibetan Plateau was treated with malic acid, lactic acid, oxalic acid, and a composite mixture of these acids at three concentrations for 30 days. On the basis of this study's hypothesis, OAs alter the rate at which soil C and N are mineralized. ANOVA analysis showed that OAs greatly enhanced soil-dissolved organic C and N, and reduced NO3--N and NH4+-N. Even though nitrification and net N mineralization rates both decreased, OAs caused the former to increase. Mineralization rates of C and N were significantly affected by concentration levels and their interaction with different types of OAs. Particularly noteworthy was the fact that oxalic acid enhanced C mineralization the most and that mineralization was most robust in OAs with high concentrations. Moreover, in high-concentration settings, the effects of OAs on microbial biomass C, microbial biomass N, sucrase, chitinase, beta-glucosidase, and urease enzymes were more noticeable. By increasing bioavailable C and N, microbial biomass, and enzyme activity, OAs increase soil C mineralization and decrease N mineralization, according to the structural equation model. This work suggests that root secretions decouple soil C and N, making resource competition-based alpine meadow management measures like restricting shrub expansion by managing N availability more effective.

Soil erosion status is a comprehensive indicator reflecting the quality and stability of ecosystems. Soil erosion changes in China are becoming more unclear due to climate change and intensified human activity. Within the framework of climate change, this study treats the rainfall erosion factor as a dynamic factor and examines three types of contrasting precipitation—general, heavy, and extreme—through integrates the Revised Universal Soil Loss Equation and Geographic Information Systems to reveal differences in water erosion driven by varying intensities of precipitation. The results reveal that over 63% of China's land area has experienced soil erosion during the historical period (1980–2022), with slight erosion being the most common. Severe water erosion is predominantly found in the Southwest Basin, the Yangtze River Basin, and the Yellow River basin. The multi‐year average soil erosion rate in China is estimated at 2.46 t·ha −1 yr −1 , with R95P and R99P contributing 26.50% and 7.71%, respectively. Future projections (2023–2100) indicate that soil erosion driven by PRCPTOT, R95P, and R99P could increase by 22%–91% under SSP5‐RCP8.5 and SSP2‐RCP4.5 scenarios. Overall, climate change has a limited effect on the spatial pattern of soil erosion in China, mainly influencing the intensity and extent of water erosion and adversely impacting most regions. Extreme precipitation is more sensitive to climate change, making future erosion risks associated with it a critical concern. These findings can guide decision‐makers and resource managers in regional planning to enhance resilience to climate change and secure water and food resources.

Study region: The loess tableland-gully region, China. Study focus: The Grain for Green Program (GFGP) has been implemented on the Loess Plateau for over 20 years, and the changes of soil water resources are widely concerned. Based on measurements of soil water content (0-6 m) in 2003, 2011, and 2024, this study investigates the changing trend and recharge characteristics of soil water under different land uses. New hydrological insights for the region: Soil water recharge depth reached to 2.4-2.6 m in forestlands, and 4.2-4.6 m in both wheat fields and grassland in a wet year with a 6-year return period. Soil water content (SWC) was consistently in a severe deficit status in the root zone below the recharge depth in forestland after 14 years old, but did not show a continuous decreasing trend, which reflected a balance between forest water consumption and precipitation infiltration. As the orchards were converted to cropland or grassland, the SWC gradually increased with rainfall infiltration and was back to be close to the field capacity in 3-6 m soil depths after 4-6 years. The GFGP has not caused a severe soil water crisis under a reasonable land use structure. The limited and variable precipitation should be maximally intercepted and infiltrated into the soil, so both the rainfed agricultural production and the forest-grassland vegetation can achieve sustainable development in the Loess Plateau under the carrying capacity of precipitation resources.

The long-term stability of terraced landscapes is a cornerstone of regional ecological security and agricultural sustainability, and this stability depends upon their most vulnerable element-the terrace sidewalls. However, the interactive regulatory mechanisms by which terrace land use types (LUT) and sidewall cover types (CT) influence terrace sidewalls remain poorly understood. This study proposed and tested an "upper surface-sidewall coupling" framework. A factorial experiment with LUT (woodland, grassland, cropland) x CT (uncovered, plant cover, biocrust cover) assessed the response of soil stability on terrace sidewalls. Results indicated that the stabilizing effect of CT is contingent upon LUT, with some combinations yielding synergistic effects and others antagonistic, resulting in unexpected stability trade-offs. A critical paradox emerged in woodland terraces: despite having the highest soil organic matter (4.72 +/- 0.37 g kg(-1)) and clay content (25.4 +/- 0.3 %), their sidewalls exhibited the lowest erosion resistance (erodibility factor K = 0.241). Plant cover on cropland terrace sidewalls demonstrated remarkable synergistic benefits, increasing the mean weight diameter (MWD) of aggregates by 617 %, a stabilizing effect that far surpassed the 248 % improvement in woodlands. Biocrust cover exhibited a dual effect of water retention versus structural instability: although it increased soil moisture by 27.9 %, it showed limited improvement in aggregate stability and intensified clay loss due to enhanced wet-dry cycling. Structural equation modeling revealed that LUT and CT jointly regulated soil temperature, soil moisture, and bulk density, which directly or indirectly affected soil compaction (explaining 60 % of variance), erodibility (44 %), and aggregate stability (R0.25 43 %). This study unravels the complex interactions between LUT and CT, providing a theoretical foundation for precision terrace sidewall management on the Loess Plateau and in other ecologically fragile regions globally. It also provides a new perspective for understanding the ecological processes of upper terrace surface-sidewalls coupling systems.

Soil salinization poses a significant challenge to farmland tillage and production worldwide, especially in the dryland saline-sodic soils area characterized by clayey texture, low permeability, and high compaction. How to solve soil water infiltration of the low-permeability saline-sodic soils is an important practical problem that has been restricting its agricultural production availability. In this study, fine sand with particle sizes of 0.15-0.50 mm was used for two treatments: covering soil with a 0.5 cm thick layer and mixing at a 1:2 ratio (fine sand: saline-sodic soil) to evaluate sand addition effects on soil physical and hydraulic properties. Results showed that the addition of fine sand to the low-permeability soil significantly improved the soil physical properties. Mixing fine sand into low-permeability soil reduced bulk density (BD) and soil compressive strength (SCS) of surface soil by 2.8% and 41.5%, while increasing total porosity (TP), non-capillary porosity (NCP) and soil water content (SWC) by 3.0%, 11.3%, and 26.6%, respectively. Additionally, fine sand covering onto the low-permeability dryland soils led to a significant decrease in SCS, TP, and NCP by 30.1%, 4.6%, and 20.3%, respectively, while SWC increased by 81%. Soil infiltration rate was increased due to mixing fine sand into the soil. The initial infiltration rate (IIR) and steady-state infiltration rate (SIR) significantly increased by 65.1% and 44.5% after mixing fine sand into the soil, respectively. BD and NCP were the dominant influence factors on SIR, and SCS and NCP were identified as the main influence factors on IIR when employing fine sand covering and mixing for the low-permeability soils. Therefore, this study's findings highlighted the effectiveness of the addition of fine sand in improving soil permeability and soil water conservation and provided a tested practical basis for the addition of fine sand to enhance the sustainability of the saline-sodic soils.

[Objective]In order to explore the effects of different land use patterns on soil physicochemical properties in the Loess Plateau area.[Methods]This study used bare land as a control(CK),and set four different use patterns as conventional fertilization farmland(H),unfertilization farmland(L),and alfalfa grassland(A)in Changwu,Shaanxi Province since 2005.The physical and chemical properties of 0-200 cm soil in the four plots were determined in July 2021.[Results]After 17 years,there were significant differences between farmland and grassland on soil physicochemical properties.(1)In 0-40 cm soil surface,the volume fraction of clay and powder in alfalfa field slightly increased compared with the other three plots,the volume fraction of sand slightly decreased,while the proportion of clay and fine powder in bare field decreased.(2)In the 0-20 cm of the soil,compared to bare land,soil pH significantly increased by 0.8％in alfalfa grassland,and significantly decreased by 1.7％in fertilized farmland.Except for 80-100 cm,soil pH in 0-200 cm section of fertilized farmland was significantly lower than that in the other three plots.Compared with bare land,in the 0-20 cm of the soil,the organic carbon storage,organic matter and nitrogen content of alfalfa grassland and fertilized farmland increased significantly and the contents of them from alfalfa grassland was higher than those of fertilized farmland.The content of available phosphorus and available potassium of alfalfa grassland and unfertilized farmland decreased significantly.The content of available potassium of fertilized farmland also decreased significantly.The content of alkaline dissolved nitrogen and nitrate-ammonium nitrogen of unfertilized farmland decreased significantly.(3)Under different land use patterns,soil organic matter,organic carbon and total nitrogen showed a decreasing trend from 0 to 60 cm,then an increasing trend showed until it reached 100 cm depth and after where a decreasing trend showed again with the deepening of the soil layer.The available phosphorus content of the soil in grassland gradually increased after 60 cm.The vertical distribution of other nutrient indexes in 0-200 cm space showed a downward trend.(4)There was a significant positive correlation between soil organic matter,total nitrogen,alkaline dissolved nitrogen and nitrate-ammonium nitrogen at 0-100 cm,and a significant negative correlation between available phosphorus and organic matter,total nitrogen,alkaline dissolved nitrogen and pH.There was a significant positive correlation between soil organic matter and available potassium at 100-200 cm,and a significant negative correlation between available phosphorus and pH.[Conclusion]Reasonable farmland management and continuous planting of alfalfa in the Loess Plateau area can keep the nutrient indexes of organic matter,total nitrogen and available nitrogen at a high level,which can guarantee soil quality to a certain extent.In order to promote the sustainability of soil in this region,it is recommended to increase the input of potassium fertilizer and organic fertilizer in farmland,while the grassland needs to supplement the appropriate amount of phosphate and potassium fertilizer.

National Field Scientific Observation and Research Station of Farmland Ecosystem in Changwu,Shaanxi Province(Changwu Station)is located in a region that represents the typical farmland of the tableland-gully region of the Loess Plateau.The installation of meteorological automatic observation systems at Changwu Station for long-term positioning observation of meteorological elements is of great significance for studying the farmland ecosystem's water,soil,atmospheric,and biological processes under the background of climate change in this region.This dataset processes,controls and evaluates the original meteorological data from Changwu Station during 2005-2019,and discloses the information on 18 meteorological observation indexes(i.e.atmospheric temperature,relative humidity,precipitation,atmospheric pressure,total radiation,reflected radiation,ultraviolet radiation,net radiation,photosynthetic active radiation,sunshine hours and soil temperature at depths of 0 cm,5 cm,10 cm,15 cm,20 cm,40 cm,60 cm and 100 cm),comprising 180 monthly entries and 15 annual entries.The aim is to provide essential data support for agro-ecological research,weather disaster early warning and climatic potential productivity simulation in the tableland-gully region of the Loess Plateau.

With the vigorous promotion of apple tree planting on the Chinese Loess Plateau (CLP), a mosaic pattern of apple orchards and traditional farmland has emerged in the region. However, the interaction between adjacent farmland and apple orchards in terms of soil water and nutrient migration remains unclear. This study aimed to investigate the spatial distribution of the soil water content (SWC) and soil nutrients, as well as their interactions, in 0-10 m soil layers of apple orchards of different stand ages and adjacent farmland under the orchard-farmland land use pattern. The results revealed a significant decrease in average-depth SWC in the orchards in the 0-10 m soil profile (R-2 = 0.90) with increasing orchard age, accompanied by a significant increase in soil water deficit (SWD, R-2 = 0.94). The annual growth rate of SWD was found to be as high as 5.94 mm center dot m(-1)center dot y(-1). Deep soil and surrounding farmland were identified as important sources of soil water for apple tree growth, particularly in older orchards; a 25-year-old orchard absorbed approximately 10.8 % of soil water towards farmland with a horizontal distance of 7 m. The distribution of soil organic carbon (SOC) and total nitrogen (TN) in the 0-10 m soil profile exhibited a similar pattern, decreasing and then stabilizing with increasing depth. However, the peak depth and accumulation of soil nitrate (NO3--N) significantly increased with orchard age. The migration and accumulation of NO3--N in the soil provided a scientific basis for the transport of soil water, with NO3--N accumulation (405.32 mg kg(-1)) observed in the deep soil (3-6 m) of farmland located 5 m away from a 30-year-old orchard, confirming the exchange of soil water and nutrients between the orchard and the farmland. The stand age of the orchards was identified as the main environmental factor influencing soil water transport under the orchard-farmland land use pattern. Overall, our findings provide valuable insights into the interaction between apple orchards and farmland under the mosaic pattern, which can contribute to a more rational layout of apple orchards and farmland in the future, promoting the efficient utilization of soil water and nutrients on the CLP.

Studies on the spatiotemporal dynamics in ecosystem carbon and water exchanges are essential in predicting the effects of climate change on regional carbon and energy budgets. Using the eddy covariance technique, carbon and water fluxes were observed in a typical winter wheat ecosystem (WWE) and an agroforest ecosystem (AFE) in the southern Loess Plateau from 2004 to 2010. The seasonal and inter-annual variability in gross primary productivity (GPP), net ecosystem exchange (NEE), evapotranspiration (ET), and water use efficiency (WUE) were examined and the main influencing factors were identified using the Pearson correlation. The results indicate that the seasonal GPP and NEE showed a bimodal distribution in WWE, while this was unimodal in AFE. The sinusoidal function did well in the characterization of seasonal ET dynamics for both ecosystems, with the determination coefficients being 0.85 and 0.94, respectively. In WWE and AFE, the annual mean GPP were 724.33 and 723.08 g C m−2 a−1, respectively, and the corresponding ET were 392.22 and 410.02 mm a−1. However, the difference in NEE between the two ecosystems was obvious, NEE were −446.28 and −549.08 g C m−2 a−1, respectively, showing a stronger carbon sink in AFE. There were strong coupling relationships between the GPP and ET of both ecosystems; the overall slopes were 1.71 and 1.69, respectively. The seasonal trend of WUE was bimodal in WWE, with peak values of 3.94 and 3.65 g C kg−1 H2O, occurring in November and April, respectively. However, the monthly WUE in AFE had one single peak of 4.07 g C kg−1 H2O in January. Photosynthetically active radiation (PAR) and soil temperature (Ts) were most positively correlated with GPP, net radiation (Rn) and Ts were the major factors influencing ET, while vapor pressure deficit (VPD) and soil water content (SWC) were the major influencing factors for WUE. These results provide observational support for regional carbon neutrality simulations.

A large-scale conversion of apple orchards into farmland has occurred in the tableland region of the Chinese Loess Plateau due to the aging of apple trees and the increase in pests and diseases. However, the impact of this conversion on soil desiccation recovery and soil nutrient transportation remains unclear, posing a new challenge for sustainable agricultural development in the region. The study employed the space-time substitution approach to select a long-standing orchard and croplands that has been growing maize for 1-, 3-, 5-, and 10-years post-orchard conversion as sampling sites, to investigate the effects of recovery durations of orchard-to-cropland conversion on deep soil water recharge and residual nitrate dynamics, as well as the key factors driving these changes. The results indicated that within 5 years, the conversion led to a rapid recharge of desiccated deep soil (6-9 m), followed by a stable and slow increase in subsequent years. The annual soil water recovery rate in the deep soil was as high as 5.90 mm m(-1) a(-1). While, the increased water input also caused rapid leaching and accumulation of nitrate in the deep soil, with its peak depth increasing significantly from 3.4 m to 7.0 m over time (R-2 = 0.92). Soil water was identified as the key factor influencing nitrate leaching, with a correlation coefficient of 0.48 (P < 0.05). In conclusion, orchard-to-cropland conversion effectively replenished the deep soil water in the short term but also accelerated soil nitrate leaching. Therefore, while large-scale conversion of orchards to farmland is undertaken, it is crucial to acknowledge the trade-off relationship involving the recharge of deep soil water and the subsequent increase in deep nitrogen leaching. The findings of this study hold significant implication for the management of water and nutrient resources after the conversion of orchards to farmland, highlighting the necessity to mitigate nitrogen leaching while soil water is being restored.