Soil Water Use Research Articles

The importance of monsoon precipitation for foundation tree species across the semiarid Southwestern U.S.

Forest dynamics in arid and semiarid regions are sensitive to water availability, which is becoming increasingly scarce as global climate changes. The timing and magnitude of precipitation in the semiarid southwestern U.S. (“Southwest”) has changed since the 21st century began. The region is projected to become hotter and drier as the century proceeds, with implications for carbon storage, pest outbreaks, and wildfire resilience. Our goal was to quantify the importance of summer monsoon precipitation for forested ecosystems across this region. We developed an isotope mixing model in a Bayesian framework to characterize summer (monsoon) precipitation soil water recharge and water use by three foundation tree species (Populus tremuloides [aspen], Pinus edulis [piñon], and Juniperus osteosperma [Utah juniper]). In 2016, soil depths recharged by monsoon precipitation and tree reliance on monsoon moisture varied across the Southwest with clear differences between species. Monsoon precipitation recharged soil at piñon-juniper (PJ) and aspen sites to depths of at least 60 cm. All trees in the study relied primarily on intermediate to deep (10-60 cm) moisture both before and after the onset of the monsoon. Though trees continued to primarily rely on intermediate to deep moisture after the monsoon, all species increased reliance on shallow soil moisture to varying degrees. Aspens increased reliance on shallow soil moisture by 13% to 20%. Utah junipers and co-dominant ñons increased their reliance on shallow soil moisture by about 6% to 12%. Nonetheless, approximately half of the post-monsoon moisture in sampled piñon (38-58%) and juniper (47-53%) stems could be attributed to the monsoon. The monsoon contributed lower amounts to aspen stem water (24-45%) across the study area with the largest impacts at sites with recent precipitation. Therefore, monsoon precipitation is a key driver of growing season moisture that semiarid forests rely on across the Southwest. This monsoon reliance is of critical importance now more than ever as higher global temperatures lead to an increasingly unpredictable and weaker North American Monsoon.

Ecohydrological niche segregation among desert shrubs in a gypsum-calcareous formation, north-western Iran

ABSTRACT Background Xerophilic subshrubs exhibit multiple functional types and frequently show hydrological niche segregation. In the poorly studied Irano-Turanian gypsum deserts, knowledge of the ecohydrological strategies of different plant species is essential to understand community complexity in these vulnerable ecosystems. Aim We studied the ecohydrological strategies of five co-existing subshrub members of Caryophyllales, ascertaining if their rooting architecture, gypsum affinity or photosynthetic pathway determined their water uptake, and if gypsum crystallisation water could be a relevant water source for plants in different seasons. Methods We conducted soil and xylem sampling for isotope analyses in spring and summer and extracted water by cryogenic vacuum distillation. Oxygen and hydrogen isotope compositions were determined and compared with visual representation and Bayesian Mixing Models to determine species ecohydrological strategies. Results Species – season interactions were related to differences in xylem sap isotopic composition. Three basic strategies relying on contrasting the use of free topsoil moisture and deep soil water could be detected and were in part explained by rooting architecture. Plant gypsum affinity and photosynthetic pathways did not have a significant effect on the water sources used by the plants. Conclusions Ecohydrological niche segregation was explained partly by rooting architecture and species-specific traits. Gypsum crystallisation water was not used in summer by the studied species.

Agro-Techniques for Enhancing Wheat Productivity under Dry-land Conditions; An Overview

Wheat, being a most important stable food crop of the world and second most important food crop after rice in India, played vital role in food security of the country. Wheat is grown in India in 6 wheat growing zones, both under irrigated and dry land conditions with a lot of variation in yield. Agronomic practices such as planting pattern, seeding rate, nitrogen (N) application strategy as well as cultivars influences the pattern of use of soil water [1]. Despite sizeable area under dry land condition, production is very low mainly due to lack of proper adaptation of agro-technology. Although, there is sufficient scope to increase the dry land wheat productivity by treating seed with 1% Potassium salts, sowing drought tolerant varieties on or before 20th November in moist zone that gives more yield as compared to delayed sowing. Fertilizer application in the moist zone @ 50, 45 and 30 Kg N, P2O5, K2O ha-1, and one foliar application @ 2 % urea performed best under dry-land condition. Intercropping of dry land wheat with legume and oilseed (4:1) give more wheat equivalent yield over sole wheat. Weed management during (30-45 DAS) critical period of crop-weed competition increase wheat productivity.

Artificial Grassland Had Higher Water Use Efficiency in Year with Less Precipitation in the Agro-Pastoral Ecotone.

Improving plant water use efficiency is a key strategy for the utilization of regional limited water resources as well as the sustainable development of agriculture industry. To investigate the effects of different land use types on plant water use efficiency and their mechanisms, a randomized block experiment was designed in the agro-pastoral ecotone of northern China during 2020-2021. The differences in dry matter accumulation, evapotranspiration, soil physical and chemical properties, soil water storage and water use efficiency and their relationships among cropland, natural grassland and artificial grassland were studied. The results show that: In 2020, the dry matter accumulation and water use efficiency of cropland were significantly higher than those of artificial and natural grassland. In 2021, dry matter accumulation and water use efficiency of artificial grassland increased significantly from 364.79 g·m-2 and 24.92 kg·ha-1·mm-1 to 1037.14 g·m-2 and 50.82 kg·ha-1·mm-1, respectively, which were significantly higher than cropland and natural grassland. The evapotranspiration of three land use types showed an increasing trend in two years. The main reason affecting the difference of water use efficiency was that land use type affected soil moisture and soil nutrients, and then changed the dry matter accumulation and evapotranspiration of plants. During the study period, the water use efficiency of artificial grassland was higher in years with less precipitation. Therefore, expanding the planted area of artificial grassland may be one of the effective ways to promote the full utilization of regional water resources.

Nontraditional production additives fail to improve potato yield and economic return

AbstractManufacturers of nontraditional crop additives may claim products will enhance yield and improve economic return, yet many offer only grower testimonials for product validation rather than unbiased, peer‐reviewed research. If the products do not perform as described, they may serve to reduce grower revenue. To investigate these claims in potato (Solanum tuberosum L.), field trials were conducted near Othello, Washington from 2016 to 2019 on 27 nontraditional additive treatments composed of 32 products. Treatments were applied using one or more application techniques: in‐furrow and surface bands, foliar sprays, and chemigations/fertigations (applied through irrigation system) per manufacturer recommendations and in addition to grower standard practices. Conventional nutrients were applied to be nonlimiting to potato growth. Economic return was calculated using a mock processing contract and adjusted for individual product costs that ranged from US$15 to US$889 ha−1. Treatment‐adjusted gross return values ranged from <7.7% to >8.5% the grower standard treatment value, and total yields ranged from 108 to 136 Mg ha−1, but differences from the control were not significant for any treatment. Reclaim, a surfactant, and OneUP and NutriCal, both specialty fertilizers, increased US No. 1 yield, average tuber weight, and tuber specific gravity, respectively. Some of the tested products may provide other benefits like soil health improvement or water use reduction but those parameters were not included in this study. Growers should avoid applying unproven products until they are tested and approved by an unbiased, trustworthy research entity.

Supporting decision-makers in estimating irrigation demand for urban street trees

Greening cities is of considerable significance to creating sustainable cities. Cost-benefit analyses have shown that urban green is not only ecologically and socially desirable but also economically advantageous. However, maintaining this urban green is becoming challenging due to changing climatic conditions. With frequent heat-waves, droughts and increasing water scarcity in many regions, it is crucial to establish systematic approaches to economise the available water used for irrigation. Currently, cities rely on rough approximations to assess irrigation demand. To address this gap, a linear time series model was developed based on soil water balance and Water Use Classifications of Landscape Species approach. The model uses publicly available data regarding trees, soil, and current and forecasted weather to estimate the irrigation demand of urban street trees on a weekly time scale. The developed model is applied in a case study of a metropolis in a moderate continental climate. The results show more distributed irrigation demand than the currently implemented soil moisture based model of the case study city. Accordingly, the model can support the decision-makers to not only assess the irrigation demand of existing trees but also help in water budgeting of new plantation under varying climatic conditions.

Water competition among the coexisting Platycladus orientalis, Prunus davidiana and Medicago sativa in a semi-arid agroforestry system

Agroforestry has been widely used for the ecological restoration construction of semi-arid regions of the Chinese Loess Plateau. Investigating plant water sources is crucial for understanding the key ecohydrological processes of plant root water uptake and the water relations between coexisting plants. Clarifying the plant water use strategies can help to assess the sustainability of the vegetation restoration in agroforestry systems and provide references for the vegetation management. Thus, we investigated the water use characteristics of plants in an agroforestry system consisting of Platycladus orientalis, Prunus davidiana and Medicago sativa. The δD and δ18O of plant stem water and soil water in the 0–300 cm layer were measured. The MixSIAR model and proportional similarity (PS) were used to quantify the proportion of soil water absorbed by the plants in each layer and the hydrological niche overlap of plants. The results showed that the combined effects of rainfall recharge and evapotranspiration (ET) loss resulted in a decrease in soil water content (SWC) for the agroforestry system with increasing soil depth, and the SWC of the deep layer (80–300 cm) had minor variability (6.1–7.1%) throughout the study period. During the study period, due to the deep soil desiccation, P. orientalis, P. davidiana and M. sativa mainly utilized water from shallow (0–80 cm) soil layers, with a contribution rate of 65.4 ± 8.3%, 64.9 ± 7.7% and 73.0 ± 0.2%, respectively. The three coexisting plants relied on the unstable shallow soil water (recharged by rainfall) while the water use proportion of the deep soil layer was consistently low. This implies that the three plants were less resistant to drought stress, thus posing a threat to the stability and sustainability of the agroforestry system. Moreover, even in July and September with the high SWC in agroforestry, the partitioning of soil water among the three coexisting plants did not increase with increased ET loss. The three coexisting plants showed strong competition for soil water use, as indicated by the high values (0.69–0.97) of PS. Overall, the hydrological niche overlap of the coexisting plants in the agroforestry system resulted in low ecosystem stability. Density reduction or selection of suitable species is required to achieve sustainable vegetation restoration.

Differences in soil water storage, consumption, and use efficiency of typical vegetation types and their responses to precipitation in the Loess Plateau, China

After massive afforestation, the Loess Plateau is facing the severe challenge of water shortages. Water use efficiency (WUE) is an important indicator of plant drought resistance, and high WUE is an important way to reconcile the contradiction between vegetation growth and soil water consumption (SWC). Different vegetation types significantly influence hydrological cycle process and WUE. In this study, the Biome-BGC model was used to simulate and analyze the soil water storage (SWS), SWC, and WUE of 3 typical vegetation types in the Loess Plateau from 2005 to 2020. The results showed that the order of SWS of different vegetation types from largest to smallest was grassland (GL, 81.82 mm/day), abandoned farmland (AF, 66.92 mm/day), and Robinia pseudoacacia forest (RP, 55.64 mm/day); SWC was RP (480.09 mm/year), GL (464.68 mm/year), and AF (421.79 mm/year); WUE was RP (2.37 gC/kgH2O), GL (1.10 gC/kgH2O), and AF (0.60 gC/kgH2O). GL showed a better water retention capacity. Precipitation recharge did not meet the full SWC of vegetation. In years of high vegetation growth, as well as in the dry season when water was scarce, both RP and GL showed varying degrees of water deficit. Correlation analysis revealed that a positive effect of precipitation on WUE has a threshold effect, and the thresholds range from approximately 15–50 mm/day for RP, 15–25 mm/day for GL, and no clear pattern for AF. Overall, in water-stressed areas, a large expansion of forest land should be reduced and GL should be increased. In seasons and areas where vegetation is growing vigorously or extremely arid, irrigation regarding precipitation thresholds should be carried out to improve the WUE of vegetation and promote the sustainable development of regional ecology.

Trees in temperate alley-cropping systems develop deep fine roots 5 years after plantation: What are the consequences on soil resources?

Trees in alley-cropping systems (AC) were reported to develop deeper fine roots compared to forest trees and that they can modify soil water (SWC), mineral nitrogen (SMN) and organic matter (SOM) content. However, intercropping young trees has not been studied extensively. This study aimed to count tree fine roots abundance (TFRA) along a chronosequence of AC stands, to determine factors explaining its variability and to highlight its effects on soil resources. Seventeen alley-cropping plots ranging from 3 to 12 years old were chosen on farms in northern France. TFRA was measured by the core break method using soil samples collected at 0, 1, 3 and 10 m from a referent tree (a maple, a hybrid walnut or a hornbeam) down to 2 m depth. Before four years old, tree fine roots colonized the topsoil (0–30 cm) in rows and then mainly grew vertically from 4 to 6 years old, before laterally exploring deep soil layer (1–2 m) beyond this age. Stepwise analyses showed that stand age, tillage frequency and crop rotation duration explained 60 % of the variability of the sum of TFRA calculated for all soil layers at all distances from the tree row. The SWC was negatively correlated to TFRA suggesting that as trees get older, they dried the deep soil layer below the crop rooting zone and increased the soil depth able to store autumn and winter rainfall. No significant effect of either stand age or distance from tree rows was observed for SMN. It varied significantly with soil depth (R² = 0.3***) and was strongly correlated with soil nitrate content (R² = 0.97***). The soil ammonium content was significantly correlated with TFRA, suggesting that tree fine roots favor ammonium production or accumulation in soil, which may potentially allow for a reduction in the mineral nitrogen (N) mobility for leaching. Finally, we found a significantly high SOM correlated with TFRA only in topsoil on the tree rows at our oldest stands. No change of SOM was observed in the deep soil layer regardless of stand age. From this study, we concluded that fine root plasticity of intercropped trees occurred at early stage and may contribute with age to a better use of soil water, to managing the soil mineral N dynamic and to sequestrating carbon, at least in tree rows.

The natural abundance of stable water isotopes method may overestimate deep-layer soil water use by trees

Abstract. Stable water isotopes have been used extensively to study the water use strategy of plants in various ecosystems. In deep vadose zone (DVZ) regions, the rooting depth of trees can reach several meters to tens of meters. However, the existence of roots in deep soils does not necessarily mean the occurrence of root water uptake, which usually occurs at a particular time during the growing season. Therefore, quantifying the contribution of deep-layer soil water (DLSW) in DVZ regions using the natural abundance of stable water isotopes may not be accurate because this method assumes that trees always extract shallow- and deep-layer soil water. We propose a multi-step method for addressing this issue. First, isotopic labeling in deep layers identifies whether trees absorb DLSW and determines the soil layer depths from which trees derive their water source. Next, we calculate water sources based on the natural abundance of stable isotopes in the soil layer determined above to quantify the water use strategy of trees. We also compared the results with the natural abundance of stable water isotopes method. The 11- and 17-year-old apple trees were taken as examples for analyses on China's Loess Plateau. Isotopic labeling showed that the water uptake depth of 11-year-old apple trees reached 300 cm in the blossom and young fruit (BYF) stage and only 100 cm in the fruit swelling (FSW) stage, whereas 17-year-old trees always consumed water from the 0–320 cm soil layer. Overall, apple trees absorbed the most water from deep soils (>140 cm) during the BYF stage, and 17-year-old trees consumed more water in these layers than 11-year-old trees throughout the growing season. In addition, the natural abundance of stable water isotopes method overestimated the contribution of DLSW, especially in the 320–500 cm soil layer. Our findings highlight that determining the occurrence of root water uptake in deep soils helps to quantify the water use strategy of trees in DVZ regions.

Effects of maize straw biochar application on soil physical properties, morph-physiological attributes, yield and water use efficiency of greenhouse tomato

Effects of maize straw biochar application on soil physical properties, morph-physiological attributes, yield and water use efficiency of greenhouse tomato

不同滴灌下限对南疆枣树土壤水分变化及水分利用率的影响

不同滴灌下限对南疆枣树土壤水分变化及水分利用率的影响

Effect of Varying Irrigation and Fertigation Levels on Soil Water Dynamics and Water Use Efficiency of Potato in Wet Temperate Zone of Himachal Pradesh

Effect of Varying Irrigation and Fertigation Levels on Soil Water Dynamics and Water Use Efficiency of Potato in Wet Temperate Zone of Himachal Pradesh

Evaluation of Partitioned Evaporation and Transpiration Estimates within the DisALEXI Modeling Framework over Irrigated Crops in California

Accurate characterization of evapotranspiration (ET) is imperative in water-limited cropping systems such as California vineyards and almond orchards. Satellite-based ET modeling techniques, including the atmosphere–land exchange inverse model (ALEXI) and associated flux disaggregation technique (DisALEXI), have proven reliable in determining field scale ET. However, validation efforts typically focus on ET and omit an evaluation of partitioned evaporation (E) and transpiration (T). ALEXI/DisALEXI is based on the two-source energy balance (TSEB) model, making it uniquely qualified to derive E and T individually. The current study evaluated E and T estimates derived using two formulations of DisALEXI; one based on Priestley-Taylor (DisALEXI-PT) and the other on Penman-Monteith (DisALEXI-PM). The modeled values were validated against partitioned fluxes derived from the conditional eddy covariance (CEC) approach using EC flux towers in three wine grape vineyards and three almond orchards for the year 2021. Modeled estimates were derived using Landsat 8 Collection 2 thermal infrared and surface reflectance imagery as well as Harmonized Landsat and Sentinel-2 surface reflectance datasets as input into DisALEXI. The results indicated that the modeled total ET fluxes were similar between the two methods, but the partitioned values diverged, with DisALEXI-PT overestimating E and slightly underestimating T when compared to CEC estimates. Conversely, DisALEXI-PM agreed better with CEC-derived E and overestimated T estimates under non-advective conditions. Compared to one another, DisALEXI-PM estimated canopy temperatures ~5 °C cooler and soil temperatures ~5 °C warmer than DisALEXI-PT, causing differences in E and T of −2.6 mm day−1 and +2.6 mm day−1, respectively. The evaluation of the iterative process required for DisALEXI indicates DisALEXI-PM ET values converge on ALEXI ET with proportionate adjustments to E and T, while DisALEXI-PT convergence is driven by adjustments to E. The analysis presented here can potentially drive improvements in the modeling framework to provide specific soil and canopy consumptive water use information in unique canopy structures, allowing for improved irrigation and water use efficiencies in these water-limited systems.

Fall Straw Incorporation with Plastic Film Cover Increases Corn Yield and Water Use Efficiency under a Semi-Arid Climate

Corn straw incorporation in soil has been regarded as an environment-friendly approach for straw utilization. However, straw incorporation has been a challenge under a cold and dry climate due to slow decomposition. This field study was to use a novel approach to incorporate corn straw into the soil during the fall season with a plastic film cover in an effort to enhance the straw degradation, soil water use efficiency, and corn growth and yield. Two-year field experiments were conducted in northeast China to investigate the effects of four treatments on soil properties and corn growth: (1) straw incorporation with film cover, (2) straw incorporation only, (3) film cover only, and (4) control. Soils and corn plants were collected during the growing season and analyzed for soil temperature and moisture, straw degradation, corn biomass, grain yield, and water use efficiency. Results indicated that straw incorporation with film cover increased grain yield by 53% as compared to straw incorporation only and by 102% to control. The straw decomposition under film cover was 20% faster, significantly higher than that of the straw incorporation treatment. In all cases, soil water content before planting, corn water uptake, and corn water use efficiency under straw incorporation with film cover were significantly higher than straw incorporation and control. Surface film cover resulted in 10-day earlier corn tasseling in compared to treatments without film cover. This field study demonstrated that straw incorporation with film cover would enhance straw degradation in soil, improve soil properties, and increase corn yield and water use efficiency, which could be potentially used as a sustainable soil management practice in northeast China.

Effect of long term application of super absorbent polymer on soil structure, soil enzyme activity, photosynthetic characteristics, water and nitrogen use of winter wheat.

Water scarcity and seasonal drought are major constraints on agricultural development globally. Super absorbent polymer (SAP) is a good amendment that can improve soil structure, increase soil water retention, and promote crop growth even with less soil moisture. We hypothesize that long term application of SAP has a better effect on soil organic carbon, soil enzyme activity, photosynthetic characteristics, yield, and water and nitrogen use than short term application. A long term field experiment with different application rates (0 (CK), 15 (L), 30 (M), 45 (H) kg ha-1) of SAP was conducted at the Yuzhou water conservation agriculture base of the Henan Academy of Agricultural Sciences from 2011 to 2019. The results indicate that applying SAP increases > 0.25 mm aggregates and decreased<0.25 mm aggregates in the soil after one year (2011) and 9 years (2019) of application. In addition, soil organic carbon, soil microbial biomass carbon, soil sucrase and cellulase activities, soil water consumption, water consumption, net photosynthetic rate (Pn), leaf water use efficiency (LWUE) of wheat and yield, all increased after SAP application. SAP also boosts water use efficiency and nitrogen use efficiency. Correlation analyses show that SAP promotes the growth of wheat, and improves the utilization rate of soil water and nutrients by improving the soil structure and increasing soil organic carbon and microbial enzyme activity. Based on our research, SAP treatment at a dosage of 45 kg ha-1 is most effective and is thus recommended.

Nitrogen Fertilization Effects on Soil Nitrate, Water Use, Growth Attributes and Yield of Winter Wheat under Shallow Groundwater Table Condition

Shallow groundwater plays a vital role in water use and the yield of winter wheat. Nitrogen (N) application significantly affects crop uptake and utilization of water from irrigation, but little is known about groundwater use. More importantly, excessive N application will also bring a series of environmental problems. An experiment was carried out in micro-lysimeters at 0, 150, 240, and 300 kg/ha N fertilization rates based on 0.6 m groundwater depth with relatively strong alkaline soil in the winter wheat growing season. The results showed that increasing the N application rate significantly increased the sensitivity of the daily groundwater evaporation velocity of winter wheat to environmental meteorological factors (soil surface moisture, humidity, atmospheric pressure and atmospheric temperature), and promoted crop water use, crop growth and yield under the 0.6 m groundwater depth. From 150 kg/ha to 300 kg/ha N fertilization, LAI and yield increased by 26.95–82.02%, and evapotranspiration (ET) and groundwater use efficiency (GUE) increased by 11.17–14.38%. However, a high N application rate would sharply induce surface soil drought, leading to a rapid increase in nitrate accumulation in the vadose zone and a significant decrease in partial factor productivity of applied N (PFPN). With the N application of 150–300 kg/ha, the accumulation of nitrate in the vadose zone increased by 8.12 times, and soil moisture in 0–20 cm and PFPN significantly decreased by 19.16–57.53%. N fertilization had a significant effect on water transfer and could promote the consumption and utilization of groundwater at 0.6 m depth. Considering yield, water use, the accumulation of nitrate, and PFPN, the optimal N application was 219.42–289.53 kg/ha at 0.6 m depth.

Recent Response of Vegetation Water Use Efficiency to Climate Change in Central Asia

Quantifying the coupled cycles of carbon and water is essential for exploring the response mechanisms of arid zone terrestrial ecosystems and for formulating a sustainable and practical solution to issues caused by climate change. Water use efficiency (WUE), one of the comprehensive indicators for assessing plant growth suitability, can accurately reflect vegetation’s dynamic response to changing climate patterns. This study assesses the spatio-temporal changes in WUE (ecosystem water use efficiency, soil water use efficiency, and precipitation water use efficiency) from 2000 to 2018 and quantifies their relationship with meteorological elements (precipitation, temperature, drought) and the vegetation index (NDVI). The study finds that the sensitivity of NDVI to WUE is highly consistent with the spatial law of precipitation. The εPre threshold range of different types of WUE is about 200 mm or 1600 mm (low-value valley point) and 300 mm or 1500 mm (high-value peak point), and the εTem threshold value is 3~6 °C (high-value peak point) and 9~12 °C (low-value valley point). The degree to which vegetation WUE is influenced by precipitation is positively correlated with its time lag, whereas the degree to which temperature influences vegetation is negatively correlated. The WUE time lag is very long in hilly regions and is less impacted by drought; it is quite short in plains and deserts, where it is substantially affected by drought. These findings may be of great significance in responding to the severe situation of increasingly scarce water resources and the deterioration of the ecological environment across Central Asia.

Satellite observed delaying effects of increased winds on spring green-up dates

Wind speeds have substantially changed over the Northern Hemisphere during the past a few decades, and such changes have been shown to have important implications for the growth, chemical composition, structure, and morphology of terrestrial ecosystems. However, the effects of wind change on the spring leaf green-up date (GUD) remain largely unknown. Using both 89 sites of flux measurements (972 site-year in total) and satellite observations over 1982–2015, here we show that higher winds in the spring preseason contributed to the delayed GUD for 29.8% of northern ecosystems, and various factors controlled the strength of the delaying effects. We further show that the earlier GUD with climate change was offset roughly by 24.4 ± 3.7% due to the increase of wind. Higher winds potentially caused delayed GUD by changes in soil conditions and differences between daytime and night-time temperatures. A higher precipitation could likely compensate the drying effects of winds on GUD. Among different vegetation types, soil water and water use efficiency were the most important regulators of the sensitivity of GUD to wind for all plant functional types, while evapotranspiration regulated grasslands and shrubs. Our results identified the new role of wind change on the spring phenology in respective of satellite observations, and future ecosystem models might consider these effects for a better representation of the responses of vegetation phenology to climate change.

Thinning promoted the rejuvenation and highly efficient use of soil water for degraded Caragana korshinskii plantation in semiarid loessal regions

AbstractHigh‐density afforestation of single‐species causes soil desiccation and vegetation degradation, posing severe challenges for plant rehabilitation, survival and its sustainable soil water use in drought regions. We explored the eco–hydrological responses of density adjustment for a typical degraded Caragana korshinskii plantation on the Chinese Loess Plateau, using 2‐year field observations. The treatments included two thinning intensities [thinning one at an interval of one (T50) and two (T67) shrubs], three pruning intensities [pruning 25% (P25), 50% (P50), and 75% (P75) of branches], and a control treatment (CK). Results indicated that the total soil water storage (0–600 cm) in T50 and T67 was 14.1% and 17.0% higher than that in CK in 2020 (p &lt; 0.05). Treatments T67 and P25 significantly affected the length, basal diameter, and biomass of stems compared with the CK. Moreover, canopy transpiration at the individual–scale in T67 was 43.5% and 37.6% higher in 2019 and 2020 than that in CK (p &lt; 0.05). At the stand–scale, the canopy transpiration in T67 was reduced by 81.2% in 2019 and by 79.2% in 2020 compared with that in CK (p &lt; 0.05), respectively. In 2020, the water use efficiency in T67 was 13.8% and 101.7% higher (p &lt; 0.05) than that in CK and T50, respectively. These observations indicate that thinning the stand density by 67% (T67) promotes plant rejuvenation and improves highly efficient use of soil water for the excessively afforested C. korshinskii plantations on the Loess Plateau. Our findings will guide the rational management of overcrowded C. korshinskii plantations in similar dry regions.