Search Results (319)

Stem radius growth (GRO), tree water deficit (TWD), and maximum daily shrinkage (MDS) were monitored throughout 2023 in a semi-arid Mediterranean forest stand in Burdur, Türkiye, where Pinus nigra subsp. pallasiana (Lamb.) Holmboe and Pinus brutia Ten. naturally co-occur. These indicators, derived from electronic band dendrometers, were analyzed in relation to key climatic variables. Results indicated that P. brutia had a longer growth period, while P. nigra exhibited a higher average daily increment under the environmental conditions of 2023 at the study site. Annual stem growth was nearly equal for both species. Based on dendrometer observations, P. brutia exhibited lower normalized TWD and higher normalized MDS values under varying vapor pressure deficit (VPD) and soil water potential (SWP) conditions. A linear mixed-effects model further confirmed that P. brutia consistently maintained lower TWD than P. nigra across a wide climatic range, suggesting a comparatively lower degree of drought-induced water stress. GRO was most influenced by air temperature and VPD, and negatively by SWP. TWD was strongly affected by both VPD and SWP, while MDS was primarily linked to minimum air temperature and VPD. Moreover, MDS in P. brutia appeared more sensitive to climate variability compared to P. nigra. Although drought limited stem growth in both species during the study year, the lower TWD and higher MDS observed in P. brutia may indicate distinct physiological strategies for coping with drought. These findings offer preliminary insights into interspecific differences in water regulation under the particular climatic conditions observed during the study year in this semi-arid Mediterranean ecosystem. Full article

This article addresses the impact of deficit irrigation on the agronomic and physiological performance of “Rojo Brillante” persimmon trees in a Mediterranean climate. It compares the effect of a sustained deficit irrigation (SDI; imposing water deficit uniformly throughout the entire crop cycle) strategy and two regulated deficit irrigation (RDI; enforcing a water deficit during the phenological phases that are less sensitive to water stress) strategies. Field trials were conducted from 2022 to 2024 at the Cajamar Experimental Center in Paiporta, Valencia, Spain. The trees respond to mild water stress reducing transpiration through stomatal closure. RDI resulted in modest irrigation water savings (11–16%), minimizing fruit drop, leading to an increased number of fruits per tree and a higher marketable yield, although this came at the cost of a reduced unit fruit weight. SDI achieved a 30% reduction in irrigation water usage without impacting on the marketable yield, but it also caused a decrease in unit fruit weight. RDI increased water productivity (yield obtained per amount of water applied) primarily through higher yields, while SDI improved productivity mainly by lowering the amount of irrigation water applied. Both irrigation strategies are recommended for cultivating “Rojo Brillante” persimmons. RDI is especially advisable in years with lower fruit loads as more intensive thinning may be necessary in years with higher fruit loads. Conversely, SDI is recommended in situations where water availability is limited. Full article

Soil moisture content (SMC) is a critical parameter for agricultural productivity, particularly in semi-arid regions, where irrigation practices are extensively used to offset water deficits and ensure decent yields. Yet, the socio-economic and remote context of these regions prevents sufficiently dense SMC monitoring in space and time to support farmers in their work to avoid unsustainable irrigation practices and preserve water resource availability. In this context, our study addresses the challenge of high spatial resolution (i.e., 20 m) SMC estimation by integrating remote sensing datasets in machine learning models. For this purpose, a dataset made of 166 soil samples’ SMC along with corresponding SMC, precipitation, and radar signal derived from Soil Moisture Active Passive (SMAP), Integrated Multi-satellitE Retrievals for GPM (IMERG), and Sentinel-1 (S1), respectively, was used to assess four machine learning models’ (Decision Tree—DT, Random Forest—RF, Gradient Boosting—GB, Extreme Gradient Boosting—XGB) reliability for SMC mapping. First, each model was trained/validated using only the coarse spatial resolution (i.e., 10 km) SMAP SMC and IMERG precipitation estimates as independent features, and, second, S1 information (i.e., 20 m) derived from single scenes and/or composite images was added as independent features to highlight the benefit of information (i.e., S1 information) for SMC mapping at high spatial resolution (i.e., 20 m). Results show that integrating S1 information from both single scenes and composite images to SMAP SMC and IMERG precipitation data significantly improves model reliability, as R² increased by 12% to 16%, while RMSE decreased by 10% to 18%, depending on the considered model (i.e., RF, XGB, DT, GB). Overall, all models provided reliable SMC estimates at 20 m spatial resolution, with the GB model performing the best (R² = 0.86, RMSE = 2.55%). Full article

Almond (Prunus dulcis Mill.) is characterized by its water stress tolerance and adaptability to diverse management strategies, allowing it to maintain or even enhance almond quality while achieving optimal yields. Limited research has been conducted to date on how almond production and quality vary across different water regimes and production systems, or how tree age modulates crop responses to deficit irrigation and organic practices. This study examines the effects of regulated deficit irrigation (RDI) under organic (OPS) and conventional (CPS) production systems, analyzing the impact on nut quality (physical and chemical parameters) and its sensorial properties in an almond orchard during seasons in 2019 and 2023, when the trees were 3-years old and when they were close to their yield potential at 7-years old, respectively. The PS and irrigation strategy affected the nut quality, yield, and tree growth. The OPS and RDI methods accumulated season-dependent yield losses in both studied periods. The kernel weight under OPS was lower than CPS in 2019, with these differences being less evident in 2023. The highest antioxidant activity and total phenolic compound values were obtained with the OPS and RDI methods in 2019, whereas the sugar and organic acid contents showed improvements under the OPS and the RDI strategy during 2019 and 2023, respectively. Finally, significant improvements were observed in relation to the fatty acids profile for nuts harvested under OPS in both seasons, especially in the latter season with RDI. Thus, almond quality can be enhanced by the integration of both OPSs and RDI strategies, although these improvements are dependent on tree age. Full article

Walnut (Juglans regia L.) exhibits a high sensitivity to water deficit, making it crucial to comprehend this characteristic in order to optimize irrigation strategies to improve its productivity. Deficit irrigation is widely used under drought conditions to achieve water savings goals. This study examines the impact of sustained deficit irrigation (SDI) strategies—applying 33%, 50%, or 75% of the crop water demand—on yield and quality parameters of two walnut cultivars (Chandler and Cisco) over a three-year monitoring period. These treatments were compared against control trees receiving full irrigation at 100% of crop water requirements (C₁₀₀). The nut yield was significantly and proportionally reduced under the SDI treatments. In the experiment, the average yield for cv. Chandler amounted to 6.7, 6.4, and 12.2 kg tree⁻¹ under SDI₃₃, SDI₅₀, and SDI_75, respectively, which were less than 13.9 kg tree⁻¹ in the C₁₀₀ plot. Similarly, cv. Cisco yielded 8.0, 11.6, 11, and 15.6 kg tree⁻¹ under SDI₃₃, SDI₅₀, SDI₇₅, and C₁₀₀, respectively. These findings indicate that the cultivar Cisco exhibits greater tolerance to moderate and intermediate levels of water deficit. Furthermore, the SDI treatments notably influenced several morphological and physicochemical kernel parameters. The key affected attributes include the weight, size, color, profiles of specific sugars, and mineral content (notably potassium, iron, and zinc), as well as the composition of unsaturated fatty acids (palmitoleic and cis-vaccenic) and polyunsaturated fatty acids (linoleic and α-linolenic), with pronounced effects observed particularly under the SDI₇₅ treatment. Thus, deficit irrigation did not drastically affect the kernel quality parameters, and it is also possible to augment them by selecting the appropriate water stress level. Therefore, for both walnut cultivars, approximately 25% of the irrigation water (SDI₇₅), equivalent to an average of 1681 m³ ha⁻¹, can be conserved relative to the total crop water requirement without negatively impacting walnut tree performance in the short to medium term. Here, we show the key role of adjusting irrigation practices by stressing the benefits of SDI that can save water, foster water productivity, and boost walnut health-promoting phytochemicals. Full article

Fruits are increasingly recognized as an important part of a healthy diet. Fruit crops represent a wide range of woody perennial species grown in orchards. Water availability is a primary environmental factor limiting fruit crop growth and productivity. Erratic rainfall patterns and increased temperatures due to climate change are likely to increase the duration of droughts. This review aims to highlight the different mechanisms by which fruit crops respond to water stress deficits. Emphasis is placed on physiological, genetic and epigenetic determinants of stress response in fruit crops. These findings can contribute to a deeper understanding of the underlying effects of drought. We also describe new research opportunities made possible by the increasing availability of population-level genomic data from the field, including genome-wide association studies (GWAS) and high-throughput phenotyping. Full article

Proximal plant-based monitoring provides high-resolution data about trees, leading to more precise orchard management and in-depth knowledge about tree physiology. The present work focuses on continuous real-time monitoring of olive cv. ‘Ascolana tenera’ over hourly intervals during the third stage of fruit growth (mesocarp cell expansion) under mild water stress conditions (ψStem above −2 MPa). This is achieved by mounting dendrometers on the root, trunk, branch, and fruit to assess and model the behavior of each organ. The diameter variation in each organ over different time intervals (daily, two-weeks, and throughout the entire experiment), as well as their hysteretic patterns relative to each other and vapor pressure deficit, are demonstrated. The results show different correlations between various organs, ranging from very weak to strongly positive. However, the trend of fruit versus root consistently shows a strong positive relationship throughout the entire experiment (R² = 0.83) and a good one across various two-week intervals (R² ranging from 0.54 to 0.93). Additionally, different time lags in dehydration and rehydration between organs were observed, suggesting that the branch is the most reactive organ, regulating dehydration and rehydration in the tree. Regarding the hysteretic pattern, different rotational patterns and characteristics (shape) were observed among the organs and in relation to vapor pressure deficit. This research provides valuable insight into flow dynamics within a tree, models plant water relations and time lags in terms of water storage and transport, and could be implemented for precise olive tree water status detection. Full article

Climate change is increasing global temperatures and imposing new constraints on tree regeneration, especially in late-successional species exposed to simultaneous drought and low-light conditions. To disentangle the effects of warming from those of atmospheric drought, we conducted a multifactorial growth chamber experiment on Fagus sylvatica seedlings, manipulating temperature (25 °C and +7.5 °C above optimum), soil moisture (well-watered vs. water-stressed), and light intensity (high vs. low), while maintaining constant vapor pressure deficit (VPD). We assessed growth, biomass allocation, leaf gas exchange, water relations, and xylem hydraulic traits. Warming significantly reduced total biomass, leaf area, and water-use efficiency, while increasing transpiration and residual conductance, especially under high light. Under combined warming and drought, seedlings exhibited impaired osmotic adjustment, reduced leaf safety margins, and diminished hydraulic performance. Unexpectedly, warming under shade promoted a resource-acquisitive growth strategy through the production of low-cost leaves. These results demonstrate that elevated temperature, even in the absence of increased VPD, can compromise drought tolerance in beech seedlings and shift their ecological strategies depending on light availability. The findings underscore the need to consider multiple, interacting stressors when evaluating tree regeneration under future climate conditions. Full article

The long-term arid climate in Xinjiang poses a major challenge to sustainable jujube production. In this study, we systematically evaluated the impacts of deficit irrigation (DI) by comparing a full irrigation control (CK) with six DI treatments—mild DI (75% CK) and severe DI (50% CK) water deficits applied during either flowering + fruit setting or fruit enlargement stages. The key findings demonstrate that flowering + fruit setting DI effectively balances water conservation with productivity. Mild DI (75% CK) during flowering + fruit setting reduced irrigation by 72 mm while maintaining near-optimal photosynthesis (95% recovery post-rewatering) and significantly improving fruit quality (5.49–10.28% higher sugar content, 3.40–5.06% larger fruit volume), despite a moderate 4.22–11.36% yield reduction. In contrast, severe DI caused irreversible physiological stress (only 75% photosynthetic recovery), and fruit-enlargement-stage DI uniformly compromised both yield and fruit size. An economic analysis confirmed flowering + fruit setting mild DI as optimal, generating 17,139–20,550 RMB·ha⁻¹ profit through enhanced water use efficiency (WUE) and premium-quality fruit production. PLS-PM validation revealed that targeted flowering + fruit setting water deficit suppresses vegetative overgrowth while optimizing source–sink relationships, achieving a 23–31% WUE improvement without sacrificing marketable yield. Thus, mild DI during flowering + fruit setting is a climate-smart irrigation strategy for Xinjiang’s jujube industry, resolving water scarcity challenges with economic viability. Full article

Climate change increases drought events, resulting in lower agricultural productivity. Almond trees (Prunus dulcis (Mill.) D.A. Webb) are drought-tolerant; however, prolonged periods of water deficit can affect plant growth and productivity. The physiological and molecular responses of two almond genotypes, Filippo Ceo and Tuono, growing in the Apulia region (Italy) under well-watered and drought conditions were evaluated. Results indicate that cv. Filippo Ceo is more drought-tolerant than cv. Tuono, exhibiting higher RWC values, good levels of photosynthetic pigments, and high proline accumulation. This behavior is confirmed by gene expression analysis, which revealed upregulation of drought-responsive genes, indicating a more effective adaptation to stress of cv. Filippo Ceo. In contrast, cv. Tuono experienced greater oxidative damage and diminished physiological response. These findings indicate that cv. Filippo Ceo could be a promising cultivar for drought-prone areas, with implications for targeted breeding and agronomic strategies to improve almond tree production under water-stressed conditions. Full article

A field experiment was conducted in 2023 and 2024 in Beijing, China, to investigate effects of soil water stress, applied before the fruit ripening stage, on the fruit total soluble solid accumulation and cracking of jujube trees. The experiment consisted of two variation factors: (a) irrigation levels (MDI and SDI, applied 80% and 50% of the irrigation volume, respectively) and (b) growth stages (stage 1, before the fruit enlargement stage, and 2, before the fruit ripening stage). The two irrigation levels were applied at each growth stage in a 2 × 2 factorial arrangement, plus a control treatment receiving 100% irrigation volume, resulting in five treatments per replicate. The findings indicated that pre-enlargement stage water stress enhanced the accumulation of total soluble solid content within fruits, which subsequently promoted faster fruit growth in from the early- to mid-August period. However, by late August, both the total soluble solid content and fruit growth rates had declined, thereby mitigating the risk of fruit cracking. During the fruit enlargement stage, the fruit total soluble solid content in SDI-2 increased by approximately 24% by the end of August compared to the control, leading to lower osmotic potential and higher turgor pressure during the following ripening stage. As skin growth ceased, high turgor pressure caused fruit cracking at the following ripening stage. The SDI-2 treatment demonstrated a fruit cracking rate approximately 1.5 times higher than that of the control. Pearson correlation analysis also indicated that fruit cracking was positively correlated with total soluble solids accumulated in August. Meanwhile, the yield of SDI-2 was reduced about 18%. Therefore, the adequate soil moisture during the fruit enlargement stage was crucial to minimize jujube fruit cracking and economic losses. Meanwhile, the deficit irrigation applied during the pre-enlargement stage could effectively conserve water resources and mitigate the occurrence of extensive jujube fruit cracking. Full article

Seasonally dry tropical forests (SDTFs) represent about 41.5% of the planet’s tropical forests. The objective of this study was to characterize the annual mortality and recruitment patterns of stems and trees between the years 2012–2021 in a Caatinga remnant in the state of Pernambuco, Brazil, through geostatistical modeling, and to associate the drought events recorded in the region with vegetation dynamics. Mortality and recruitment of stems and trees were monitored in 80 permanent plots located in an SDTF remnant, counted year by year between 2012 and 2021. The standardized precipitation index (SPI) was calculated to quantify the deficit or excess of rainfall in the evaluated period. The data were then subjected to geostatistical analysis based on the calculation of classical semivariances. As a result, there was a loss of 68.33% of trees and 61.93% of stems in the forest community during 2012–2021, which were associated with the water deficit caused by drought events recorded based on precipitation data and SPI calculation for the region. The Gaussian semivariogram model better represented the spatial variability of mortality and recruitment of stems and trees. An accumulative effect of droughts on increasing mortality rates and reducing recruitment during the study period was observed. The relationship between tree and stem mortality and recruitment rates and drought events highlights the impact of water deficit on vegetation, emphasizing the importance of considering extreme climatic events in the proper management of natural resources. Full article

A syndrome called “Kiwifruit Decline Syndrome” (KiDS) affects kiwifruit in several Mediterranean areas, causing growth arrest and wilt that rapidly progress to desiccation, scarce root growth, absence of fibrous roots, brown soft-rotting areas, and cortical detachment from the central cylinder. The origin is considered multifactorial, and a correlation with hydraulic conductance impairment caused by a high vapor pressure deficit (VPD) and temperature was detected. In this work, over-tree micro-sprinkler irrigation and shading nets were tested to protect leaves from overheating and locally decrease VPD. Leaf gas exchanges, leaf temperature, stem water potential, stem growth, root starch content, root xylem vessel diameter, density, and vulnerability to cavitation were assessed. A positive effect of over-tree irrigation associated with shading was observed: lower leaf temperature, higher stem water potential, stomatal conductance, and photosynthesis were detected; moreover, root starch content was higher in the summer. Narrow xylem vessel diameters were observed, indicating a long-term adaptation to rising VPD for lower vulnerability to cavitation, in all plants, but higher diameter, lower density, and higher vulnerability index indicated lower plant water stress under over-tree irrigation associated with shading. These results indicate that microclimate control by proper agronomic management can protect kiwifruit from climate stress, decreasing the risk of KiDS onset. Full article

This study investigated the effects of rootstock selection and deficit irrigation on the growth, physiological, and photosynthetic performance of young ‘W. Murcott’ mandarin trees. A two-way ANOVA was conducted to evaluate the impact of rootstocks (sour orange, Carrizo citrange, and Volkameriana) and deficit irrigation treatments (40%, 50%, and 70% of field capacity as control) on various plant parameters. Results revealed that rootstock diameter, scion diameter, leaf chlorophyll concentration (Chl), fresh weight, total dry weight, and photosynthetic rate (P_N) were significantly influenced by rootstocks and/or deficit irrigation treatments. Deficit irrigation significantly reduced plant height, fresh and dry weights, rootstock diameter, Chl, Fv’/Fm’ (chlorophyll fluorescence), and P_N, while scion diameter, stomatal conductance, and water-use efficiency (WUE) remained unaffected. Among rootstocks, sour orange exhibited the highest Chl and Fv’/Fm’ values under water stress, indicating greater drought tolerance, despite showing lower growth compared to Carrizo and Volkameriana. Conversely, Carrizo and Volkameriana rootstocks demonstrated higher fresh and dry weights under optimal irrigation but were more sensitive to water stress. Photosynthetic rate was highest in sour orange-grafted plants under deficit irrigation, while transpiration rates were highest in control plants. These findings suggest that sour orange rootstock may enhance drought resilience by maintaining photosynthetic efficiency and chlorophyll integrity, albeit at the cost of reduced vegetative growth. At the end of this study, it was determined that W. Murcott seedlings grafted onto sour orange rootstock were more tolerant compared to the other two rootstocks. Full article

Urban forests play important roles in carbon sequestration and climate change mitigation. However, their adaptive mechanisms and limitations on photosynthesis throughout the canopy are poorly understood. This study takes the most widely distributed 50-year-old camphor plantations (Cinnamomum camphora) in Shanghai as the research objects. We investigated the variations in leaf morphology and photosynthetic physiology and biochemistry at six different canopy positions during a summer and an autumn period. We discovered that on account of leaf nitrogen loss and water deficit, light-saturated photosynthesis (A_max) declined in upper sunlit leaves despite being exposed to high sunlight in the same fashion as stomatal and mesophyll conductance (g_sw, g_m), photochemical quenching coefficient and actual photochemical efficiency of PSII (Φ_PSII, q_P), and maximum rate of electron transport and carboxylation (J_max, V_cmax) during the growing season. Although seasonal change had little effect on A_max, the relative importance of limitations varied temporally. Mesophyll and biochemical limitation were the major contributors to the decline in the A_max in upper sunlit leaves between summer and autumn, respectively. Our study highlights the constraints of carbon fixation capacity in dense stands of mature camphor trees and offers technical support for the accurate prediction of canopy photosynthesis and the enhancement of carbon sequestration management in urban forests. Full article