Next Article in Journal
Determining a Safe Distance Zone for Firefighters Using a High-Resolution Global Canopy Height Dataset—A Case in Türkiye
Previous Article in Journal
Refined Classification of Mountainous Vegetation Based on Multi-Source and Multi-Temporal High-Resolution Images
Previous Article in Special Issue
Enhancing Root Water Uptake and Mitigating Salinity through Ecological Water Conveyance: A Study of Tamarix ramosissima Ledeb. Using Hydrus-1D Modeling
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Forests
Volume 16
Issue 4
10.3390/f16040708
forests-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Seasonal Water Use Patterns of Eucalyptus with Different Ages in Southern Subtropical China

by
Haijun Zuo
,
Qing Xu
,
Deqiang Gao
,
Wenbin Xu
,
Ke Diao
and
Beibei Zhang
*
Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Ecology and Nature Conservation Institute, Chinese Academy of Forestry, Beijing 100091, China
*
Author to whom correspondence should be addressed.
Forests 2025, 16(4), 708; https://doi.org/10.3390/f16040708
Submission received: 11 March 2025 / Revised: 3 April 2025 / Accepted: 18 April 2025 / Published: 21 April 2025
(This article belongs to the Special Issue The Relationship Between Forest Vegetation and Water and Its Regulation in Changing Environments)
Browse Figures
Versions Notes

Abstract

:
Seasonal droughts induced by climate change pose a significant threat to the normal growth patterns of forests in the subtropical regions of southern China. Therefore, it is crucial to explore the response of tree water use patterns to seasonal drought to maintain tree physiological activities. However, it remains unknown whether changes in dry and wet seasons have an impact on the water use patterns of trees of different ages. In this study, a two-year experiment was conducted in Eucalyptus urophylla × Eucalyptus grandis (hereinafter referred to as Eucalyptus) plantations at three ages (4, 7, and 17 years). Specifically, the water use patterns of Eucalyptus in dry and wet seasons were calculated using hydrogen stable isotopes (including the isotopes in xylem water and 0–150 cm soil layers) coupled with MixSIAR. The results showed that there were notable variations in the proportions of water absorption from different soil layers by Eucalyptus during dry and wet seasons. During the dry season (April 2024), 4-year-old and 7-year-old Eucalyptus primarily utilized water from the 40–90 cm soil layer, while 17-year-old Eucalyptus mainly relied on deep soil water at depths of 60–150 cm, with a utilization ratio of 50.9%. During the wet season (August 2023), the depth of water uptake by Eucalyptus of different ages significantly shifted towards shallow layers, and the trees primarily utilized surface soil water from the 0–60 cm layer, with utilization ratios of 59.9%, 64.8%, and 61.6% for 4-year-old, 7-year-old, and 17-year-old Eucalyptus, respectively. The water sources of Eucalyptus during dry and wet seasons were variable, which allowed Eucalyptus to cope with seasonal drought stress. The differences in the water uptake strategies of Eucalyptus between dry and wet seasons can be attributed to their long-term adaptation to the environment. Our research revealed the differences in the water utilization of Eucalyptus with various ages between dry and wet seasons in subtropical China, providing new insights for a better understanding of the adaptive mechanisms of subtropical forests in response to alterations in water conditions caused by climate change.

1. Introduction

The water use pattern of trees is not only a key factor determining their survival, growth, and distribution, but also the foundation for forest ecosystems to fulfil functions such as material supply, water conservation, and climate regulation [1,2,3]. Especially in the context of frequent seasonal drought events caused by climate change, the flexible water use pattern of trees is crucial for maintaining forest biodiversity and ecosystem stability [4,5]. Forest age, a major characteristic indicator of forest stands, has a direct impact on the water use pattern of trees in forests, thereby reflecting the adaptability of forest ecosystems to changing environments [6,7]. Therefore, exploring the water use patterns of trees of different ages is of great significance for revealing the response mechanism of forests to climate change and promoting sustainable forest development.
Despite the importance of this topic, two uncertainties still exist in studies examining the water use patterns of trees of different ages. First, the water use patterns of trees of different ages remain controversial. Generally, compared with young trees, mature trees (Populus tomentosa Carrière, Pinus ponderosa Douglas ex C. Lawson, and Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg.) mainly absorb water from deeper soil layers due to their deeper and wider root distribution [8,9,10]. However, Wang et al. [11] found that the main water absorption depth of Malus pumila Mill. became shallower with increasing forest age (10, 15, and 22 years); moreover, their water absorption patterns were not correlated with root distribution [11]. The above inconsistent results indicate that there is significant difference in the water use patterns of trees of different ages among diverse tree species. Therefore, it is necessary to explore the water use patterns of various tree species at different ages.
Second, it is still unclear whether seasons affect the water use patterns of trees of different ages. In general, trees primarily absorb water from shallow soil layers during the wet season, whereas they tend to utilize more water from deep soil layers during the dry season [12,13]. However, recent research has obtained opinions that are inconsistent with the aforementioned studies. For example, young Pinus sylvestris L. (4 years old) mainly absorbed shallow soil water during both dry and wet seasons, while older P. sylvestris (10 and 18 years old) exhibited a flexible water use pattern, specifically absorbing shallow and middle soil water during the wet season but middle and deep soil water during the dry season [14]. Similarly, 18-year-old Robinia pseudoacacia L. mainly utilized deep soil water during the dry season, while it switched to absorb shallow soil water during the wet season. However, there was no difference in the water use pattern of 30-year-old R. pseudoacacia between the dry and wet seasons [15]. These incompatible results imply that the water use patterns of trees of different ages vary significantly on a seasonal scale. Therefore, it is urgent to investigate the water use patterns of trees of different ages based on seasonal scales to enrich our understanding of this field.
In order to address the above issues, this study chose Eucalyptus plantations of different ages as objects to explore their water use patterns during the dry and wet seasons. Eucalyptus, an important timber tree species, is widely cultivated in tropical and subtropical regions around the world due to its fast-growing and high-yielding characteristics. The preserved area of Eucalyptus plantations is about 5,694,000 ha in southern China [16]. Against the backdrop of climate change, the increasing severity of seasonal drought severely limits Eucalyptus growth and poses a significant risk to the productivity of Eucalyptus plantations [17,18,19]. Therefore, in this study, we employed hydrogen stable isotopes coupled with the Bayesian mixture model to reveal the seasonal variations in water sources and the water use patterns of Eucalyptus of different ages in the low mountainous hilly areas of southern China. This study aims to answer the two following questions: (1) Does forest age affect the water use patterns of Eucalyptus? (2) Are there differences in the water use patterns of Eucalyptus in various seasons?

2. Materials and Methods

2.1. Study Area

This study was carried out at the Nanning Eucalypt Plantation Ecosystem Observation and Research Station of Guangxi, China (107°59′ E–108°18′ E, 22°28′ N–22°46′ N, Figure 1), which experiences a South Asian monsoon climate. The mean annual air temperature fluctuates between 21 °C and 22 °C. The mean annual precipitation ranges from 1200 mm to 1300 mm, with more than 80% of the rainfall occurring from May to September. The area receives an average of 1800 h of sunshine per year. The study area is characterized primarily by hilly terrain, and the soil type is mainly lithosols. The average thickness of the soil layer is approximately 0.8 m, and the soil pH value is slightly acidic. The soil fertility is moderate.
The vegetation type in the experimental area is classified as subtropical evergreen broad-leaved forest, with the main forest stand consisting of Eucalyptus plantations. The dominant species in the arbor layer of the Eucalyptus plantation is E. urophylla × E. grandis (hereinafter referred to as Eucalyptus). The shrub layer is primarily composed of Melastoma candidum D. Don, Rhodomyrtus tomentosa (Ait.) Hassk., Cyrtococcum patens (L.) A. Camus, Trema tomentosa (Roxb.) Hara, Rhus chinensis Mill., and Maesa japonica (Thunb.) Moritzi. The herbaceous layer mainly consists of Miscanthus sinensis Andersson, Hedyotis vestita R. Br. ex G. Don, and Commelina diffusa Burm.f. The experiment was conducted between August 2023 and April 2024 in Eucalyptus plantations aged 4, 7, and 17 years. Three random plots with areas of 20 m × 20 m were selected within each Eucalyptus stand, ensuring a relatively uniform spatial distribution of trees. The stand characteristics of each experimental site, such as geographical location, tree height, diameter at breast height, and stand density, were investigated (Table 1). In addition, the soil texture across 0–150 cm soil layers of Eucalyptus plantations of different ages was also examined (Table 2). Given that the three experimental sites were all situated on hilly areas far from the groundwater level (4 m below the surface, at an elevation of 140 m), groundwater was not considered a source of plant water.

2.2. Sample Collection

2.2.1. Collection of Rainfall Samples

Precipitation in the region occurs in the form of rainfall, and we utilized rain gauges to collect rainfall samples. During the collection process, we aimed to prevent the exchange of collected rainfall with the surrounding air to minimize evaporation. Before sampling, precipitation was recorded for each rainfall event in which the precipitation exceeded 5 mm during the observation period. After each rainfall event, a rainfall sample was collected in a sampling bottle. The bottle was subsequently sealed with Parafilm and stored at 4 °C.

2.2.2. Collection of Tree Stem (Xylem) Samples

The distinction between dry and wet seasons in Nanning was clear: the wet and dry seasons occurred from May to October each year and November to April of the following year, respectively. To ensure the representativeness of the collected samples from the dry and wet seasons, wet season sampling was conducted 2 days after moderate rain (10–25 mm), and dry season sampling was conducted after 15 days with no precipitation. In each sample plot of each site, three Eucalyptus trees with a similar crown width and ground diameter were selected for sampling. In accordance with the specific weather conditions, tree stems were collected on 27 July 2003, during typical wet season conditions, and on 18 April 2024, during typical dry season conditions, with one sample per tree. During sampling, nongreen corked twigs with a diameter of 0.3–0.5 cm and a length of 3–5 cm were cut from the sunny side of Eucalyptus, quickly peeled, placed in sampling bottles, and sealed with Parafilm. The samples were promptly placed in a portable icebox at approximately 4 °C and subsequently delivered to the lab for freezing and kept at −20 °C.

2.2.3. Collection of Soil Samples

The collection time of soil samples is consistent with that of tree stem samples. During stem sample collection, two soil samples were gathered adjacent to the sampled plants at various depths: 0–20 cm, 20–40 cm, 40–60 cm, 60–90 cm, and 90–150 cm by soil drill. These soil samples were obtained to assess the soil water content and stable hydrogen isotopes in soil water. Among these samples, the soil samples tested for isotopic composition were put in a bottle that was hermetically wrapped with a Parafilm membrane. The preservation of the soil samples was consistent with that of the tree stem samples. Another portion of the soil sample was stored in the aluminium box.

2.3. Sample Processing and Isotope Analysis

The soil sample in the aluminium box was subsequently subjected to drying at 105 °C for 12 h to analyse the soil water content. Tree xylem and soil water were extracted using the evaporative cooling method through a vacuum extraction apparatus (LI-2100, LICA, Beijing, China) [20]. To assure the accuracy of sample analysis and eliminate the influence of organic pollution, a 13 mm diameter organic filter with a minuscule pore size of 0.45 μm was used to filter the extracted water sample. The stable hydrogen isotopes of all water samples, including precipitation, soil water, and xylem water, were examined with a liquid water isotope analyser (LWIA-45-EP, Los Gatos Research, Santa Clara, CA, USA). Hydrogen isotope ratios were expressed in per mil (‰) notation compared with V-SMOW (Vienna Standard Mean Ocean Water), and the estimation accuracy of the LGR (Los Gatos Research) instrument was <0.2‰ for δD [21].

2.4. Data Analysis

Firstly, we used the direct inference method to ascertain the water sources of Eucalyptus. In this study, the xylem water of Eucalyptus was exclusively derived from soil water at varying depths. The method is applied to determine the primary water-absorbing soil layers of Eucalyptus by analysing the isotopic intersection locations between the xylem water and soil water lines [22]. Secondly, the Bayesian mixed model (MixSIAR) (version 3.1.7) was used to determine the proportion of water uptake by Eucalyptus from each soil layer. The calculation process included the following steps. The δD values of xylem water were uploaded into the MixSIAR model as mixed data, and the means and standard deviations of δD from the soil water in each layer were input into the MixSIAR model as source data. The δD fractionation coefficient was then set to 0, which means that there was no fractionation of isotopes during water transport from the root to the xylem [23]. The running length of “Markov chain Monte Carlo, MCMC” was set to “long”; furthermore, “Specify prior” and “Error structure” were set to “Uninformative prior” and “Residual only”, respectively. The model was evaluated for convergence via the “Gelman–Rubin” and “Geweke” methods [24]. A one-way ANOVA was conducted to investigate the xylem water δD among Eucalyptus of varying ages (p < 0.05).

3. Results

3.1. Meteorological and Environmental Conditions

During the entire research period (April 2023 to June 2024), the total precipitation was 1844.2 mm, with the precipitation primarily concentrated in the wet season from May to October, totalling 862.4 mm. It should be noted that between April 2023 and March 2024, the precipitation was 1168 mm, which is close to the perennial mean precipitation (1286 mm) in the study area. In the dry season (November 2023 to April 2024), the precipitation was only 286.6 mm, indicating a notable disparity in precipitation between the dry and wet seasons (Figure 2). Specifically, in the typical wet season month of June 2023, the precipitation reached 231.7 mm, accounting for 26.9% of the total precipitation in the wet season. Conversely, in December 2023, which is in the middle of dry season, the precipitation was 17.7 mm, constituting only 6.2% of the total precipitation in the dry season. Similar to precipitation, the daily average temperature notably varied between the dry and wet seasons. In the wet season, the daily average temperature was relatively high, measuring 26.6 °C and ranging from 19.3 to 32.3 °C. While in the dry season, the daily average temperature was lower, at 17.9 °C, but with a wider range of variation, ranging from 7.0 to 28.7 °C. Therefore, it is evident that the study area experiences greater precipitation and higher temperatures during the wet season, whereas the opposite situation was manifested in the dry season, indicating obvious characteristics of rain and heat in the same season. In addition, the average δD value of rainfall from May to October was −63.20‰, whereas that from November to April of the following year was −9.70‰. There was substantial variation in the δD values between the dry and wet seasons, with a positive deviation observed during the dry season and a negative deviation during the wet season.

3.2. Variation in Soil Water Content in Stands of Different Ages During Dry and Wet Seasons

This study revealed that the surface soil (0–20 cm) in Eucalyptus plantations of different ages was characterized by a low water content in both the dry and wet seasons (Figure 3). However, as the soil layer deepened, the soil water content gradually increased in the wet and dry seasons. In the dry season, the soil water content in April ranged from 14.8% to 26.9%, averaging 22.5% within the 0–150 cm soil layers. The average soil water content in the 0–20 cm surface layer was only 17.0%, indicating a relative deficiency of soil water in the dry season. During the wet season, the soil water content in August ranged from 25.1% to 34.9%, averaging 31.1% within the 0–150 cm soil profile, which was significantly greater than the average soil water content in the dry season (p < 0.05). The average soil water content at depths of 0–20 cm was as high as 28.3%, indicating that the soil water was recharged in a timely manner by ample precipitation during the wet season and that the soil water content remained high.

3.3. δD in Soil and Xylem Water

Figure 4 showed that the soil water δD values varied between the dry and wet seasons in the Eucalyptus plantations of different ages. Specifically, in the dry season, the δD of soil water in the 4-year-old and 7-year-old Eucalyptus plantations gradually decreased with increasing soil depth, whereas the soil water δD of the 90–150 cm deep soil layer in the 17-year-old Eucalyptus plantations was higher than that of the upper 0–40 cm layer. In the wet season, the soil water δD in the 0–20 cm was slightly greater in the 7-year-old Eucalyptus plantation than that in the 90–150 cm deep soil. Conversely, the opposite was observed in the 17-year-old Eucalyptus plantation.
The δD of xylem water in Eucalyptus plantations of different ages significantly varies during the dry and wet seasons, indicating that there was a difference in the water sources utilized by Eucalyptus in different seasons. In April, during the dry season, the xylem water δD of the 4-year-old Eucalyptus intersected with the δD of the soil water in the 20–60 cm and 90–150 cm layers, indicating that 4-year-old Eucalyptus primarily absorbed soil water from the 20–40 cm, 40–60 cm and 90–150 cm layers in the dry season. In addition, the xylem water δD of the 7-year-old and 17-year-old Eucalyptus closely matched the soil water δD in the 90–150 cm soil layer, suggesting that 7-year-old and 17-year-old Eucalyptus mainly utilized soil water in the 90–150 cm and 60–90 cm soil layers in the dry season. In August, during the wet season, the xylem water δD of the 4-year-old Eucalyptus intersected with the soil water δD of the 20–40 cm and 40–60 cm layers, suggesting that 4-year-old Eucalyptus primarily utilized soil water from the 20–60 cm soil layer in the wet season. The xylem water δD from 7-year-old and 17-year-old Eucalyptus closely resembled the soil water in the 0–40 cm soil layer, indicating that 7-year-old and 17-year-old Eucalyptus mainly relied on soil water from the 0–40 cm soil layer in August.

3.4. Water Use Patterns of Eucalyptus of Different Ages

The results of the MixSIAR model indicated significant differences in the utilization of soil water at distinct depths by Eucalyptus of different ages during the dry and wet seasons (Figure 5). In April, during the dry season, Eucalyptus aged 4, 7, and 17 years primarily absorbed water from the 40–150 cm soil layer. Among them, the highest proportion existed in water uptake from the 60–150 cm soil layer by 17-year-old Eucalyptus, with an absorption proportion of 50.9%. However, 4-year-old and 7-year-old Eucalyptus mainly absorbed water from the 40–90 cm soil layer, with absorption proportions of 40.6% and 40.8%, respectively. The utilization ratios of surface soil water (0–20 cm) were relatively low in the Eucalyptus stands of different ages, with the lowest utilization ratio of 0–20 cm soil water observed in the 17-year-old Eucalyptus, at only 15.5%.
In August, during the wet season, the water sources for Eucalyptus stands of different ages varied from those in the dry season. All the trees relied primarily on soil water at a 0–60 cm depth. Among the stands, the 7-year-old Eucalyptus utilized a relatively high proportion of water uptake from the upper 0–20 cm and 20–40 cm soil layers, with values of 23.7% and 22.6%, respectively. For 17-year-old Eucalyptus, most of the soil water was obtained from the 0–20 cm soil layer, at 22.9%, then the 20–40 cm soil layer followed at 21.4%. The water obtained from the 40–60 cm soil layer was the lowest, at 17.3%. For 4-year-old Eucalyptus, compared with the dry season, the proportion of soil water obtained from the 0–20 cm soil layer slightly increased in the wet season, at 19.7%, whereas the proportion of deep soil water utilized in the 90–150 cm soil layer decreased.
These findings clearly indicated that in the dry season, Eucalyptus plants of different ages exhibited relatively low water utilization from the 0–20 cm soil layer. Instead, they primarily depended on water from the 40–150 cm soil layer. During the wet season, Eucalyptus mainly utilized soil water from layers above 60 cm. Notably, 7-year-old Eucalyptus obtained 64.8% water from the 0–60 cm soil layer.

4. Discussion

4.1. Soil Water Content and Hydrogen Isotopes of Soil Water in Eucalyptus Plantations of Different Ages During Dry and Wet Seasons

Our study found that surface soil has a low water content and a wide range of variation in Eucalyptus plantations of different ages, which is consistent with previous research [25]. This phenomenon may be attributed to the severe impact of surface evaporation on the surface soil [26]. As the soil layer deepens, the impact of the external environment gradually diminishes, resulting in an increase in the soil water content and a tendency towards stabilization. In addition, the average soil moisture within the 0–150 cm profile in August considerably exceeded that in April (p < 0.05), particularly in the 0–20 cm surface soil. This observation indicated that the soil water deficit in the dry season was more severe than that in the wet season, especially in the surface soil. The main reason may be related to factors including rainfall, soil characteristics, and local meteorological conditions [27,28,29]. Specifically, the precipitation of the study area in the wet season is significantly higher than that in the dry season; therefore, the soil moisture in the wet season is higher than that in the dry season. Meanwhile, the evaporation of the surface soil layer during the dry season is stronger than that of the other soil layers, resulting in severe water deficit in the surface soil during the dry season.
Our results also showed that the δD values of the soil water in every layer gradually decreased with increasing soil depth in the 4-year-old and 7-year-old Eucalyptus plantations in the dry season. This phenomenon is chiefly caused by the significant evaporative enrichment of stable isotopes in surface soil water [30,31,32,33]. However, the δD values of the soil water within the 0–150 cm profile of the 17-year-old Eucalyptus plantation exhibited the opposite trend in the dry season. This observation suggests that while evaporation weakly enriched the δD values of deep soil water, the presence of older soil water (referred to as old water), the distribution of roots, strong water absorption capacity, and high clay content and water holding capacity contributed to the elevated δD values of soil water [34,35]. During the wet season, the δD values of the soil water showed slight fluctuation in the various layers (0–150 cm) of the 4-year-old Eucalyptus plantation. The δD value of soil water increased with increasing soil depth in the 7-year-old Eucalyptus plantation, which can be attributed to the mixing and dilution of rainwater isotopes and initial soil water isotopes during the infiltration process [36]. However, in the 17-year-old Eucalyptus plantation, the δD value of the soil water decreased following the increase in soil layers. This may be influenced by factors such as lateral groundwater recharge and soil texture.

4.2. Water Use Patterns of Eucalyptus of Different Ages During Dry and Wet Seasons

The distribution of precipitation in the subtropical region of southern China during dry and wet seasons is uneven, resulting in fluctuations in water resource availability for plants during different growing seasons [37,38,39]. Plants generally alter their water usage strategies to adapt to these changes in water availability, and different plants may exhibit various water use adaptations during dry and wet seasons [40,41,42]. In this study, Eucalyptus plantations of different ages primarily utilized soil water in the 40–150 cm layer during the dry season. However, the main depth of water uptake varied slightly among the different age groups of the Eucalyptus plantations. The 4-year-old and 7-year-old Eucalyptus plantations mainly relied on soil water in the 40–90 cm soil layer, whereas the 17-year-old Eucalyptus plantation primarily absorbed deeper soil water in the 60–150 cm layer. This may be because of the absence of rainfall for an extended period and dry air during the dry season, which, combined with high surface evaporation, led to reductions in soil moisture levels in the surface layer. As a result, the utilization of deep soil water by Eucalyptus plantations of different ages increased. Furthermore, given that the root distribution of the 17-year-old Eucalyptus was deeper and wider than that of the 4-year-old and 7-year-old trees, it demonstrated a greater ability to utilize soil water in the 60–150 cm layer [43,44]. In contrast, the main water-absorbing soil layer of Eucalyptus significantly shifted towards the upper soil layer during the wet season. The primary reason for this is that the frequent rainfall during the wet season effectively replenishes shallow soil water, resulting in a greater availability of shallow soil water. Plants require less energy to absorb water through surface roots; hence, they prioritize absorbing water stored in shallow soil to minimize energy consumption. This pattern of water utilization is similar to that observed in 9-year-old Eucalyptus on the Leizhou Peninsula [19]. This similarity may be attributed to comparable climate characteristics, tree species, and soil conditions between tropical and subtropical regions.
The tropical and subtropical regions of South China are highly vulnerable to climate change. In recent years, the frequency of extreme weather events, such as seasonal droughts, has increased in this region, which poses substantial risks to local plantation ecosystems [45,46]. This study aimed to reveal the water utilization patterns of Eucalyptus plantations of different ages. The results can provide a scientific foundation for the accurate management of plantation vegetation and the efficient utilization of water resources in South China. Furthermore, they can contribute to the formulation of environmental risk management strategies in anticipation of future climate change.

5. Conclusions

In this study, stable hydrogen isotopes and a MixSIAR model were primarily utilized to examine the water uptake patterns of Eucalyptus at different ages during dry and wet seasons. The findings indicated that there was a notable difference in the water use pattern of Eucalyptus of different ages between the dry and wet seasons. In the dry season, 4-year-old and 7-year-old Eucalyptus primarily utilized soil water in the 40–90 cm soil layer, with utilization ratios of 40.6% and 40.8%, respectively, and 17-year-old Eucalyptus mainly absorbed water from the 60–150 cm soil layer, with an absorption ratio of 50.9%, while the remaining 49.1% was predominantly sourced from the 0–60 cm soil layer. During the wet season, 4-year-old, 7-year-old, and 17-year-old Eucalyptus primarily utilized the upper soil water at depths of 0–60 cm, with utilization ratios of 59.9%, 64.8%, and 61.6%, respectively. These findings demonstrate that following varying water source availability in the environment, Eucalyptus could flexibly alter its water uptake strategy, indicating a strong ability to cope with seasonal drought induced by climate change.

Author Contributions

Conceptualization, H.Z. and Q.X.; methodology, H.Z.; software, B.Z.; validation, H.Z., B.Z. and Q.X.; formal analysis, H.Z.; investigation, H.Z., D.G., K.D. and W.X.; resources, K.D. and B.Z.; data curation, W.X.; writing—original draft preparation, H.Z.; writing—review and editing, H.Z., Q.X. and B.Z.; visualization, H.Z. and B.Z.; supervision, Q.X.; project administration, Q.X.; funding acquisition, H.Z., Q.X. and D.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Fundamental Research Funds of CAF (CAFYBB2020SY025; CAFYBB2017ZB003; CAFYBB2021ZE002; CAFYBB2024MA013) and the National Natural Science Foundation of China (31870716; 32160362).

Data Availability Statement

Data are contained within the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

We are very grateful to the Nanning Eucalypt Plantation Ecosystem Observation and Research Station of Guangxi for their support and assistance in the fieldwork.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Rosado, B.H.P.; Joly, C.A.; Burgess, S.S.O.; Oliveira, R.S.; Aidar, M.P.M. Changes in plant functional traits and water use in Atlantic rainforest: Evidence of conservative water use in spatio-temporal scales. Trees 2016, 30, 47–61. [Google Scholar] [CrossRef]
  2. Grossiord, C.; Sevanto, S.; Dawson, T.E.; Adams, H.D.; Collins, A.D.; Dickman, L.T.; McDowell, N.G. Warming combined with more extreme precipitation regimes modifies the water sources used by trees. New Phytol. 2017, 213, 584–596. [Google Scholar] [CrossRef] [PubMed]
  3. He, X.F.; Hui, D.F.; Liu, H.; Wang, F.M.; Yao, K.C.; Lu, H.F.; Ren, H.; Wang, J. Responses of plant water uptake sources to altered precipitation patterns in a tropical secondary forest. Agric. For. Meteorol. 2024, 355, 110138. [Google Scholar] [CrossRef]
  4. Lu, H.Q.; Wu, Y.H.; Li, Y.J.; Liu, Y.Q. Effects of meteorological droughts on agricultural water resources in southern China. J. Hydrol. 2017, 548, 419–435. [Google Scholar] [CrossRef]
  5. Hossein, G.; Tayebeh, A.A.; Alireza, E.; Mohammad, B. The spatial-temporal changes in water balance components under future climate change in the Gorganroud Watershed, Iran. Water Cycle 2025. [Google Scholar] [CrossRef]
  6. Socha, J.; Hawryło, P.; Tymińska-Czabańska, L.; Reineking, B.; Lindner, M.; Netzel, P.; Grabska-Szwagrzyk, E.; Vallejos, R.; Reyer, C.P.O. Higher site productivity and stand age enhance forest susceptibility to drought-induced mortality. Agric. For. Meteorol. 2023, 341, 109680. [Google Scholar] [CrossRef]
  7. Vangi, E.; Dalmonech, D.; Cioccolo, E.; Marano, G.; Bianchini, L.; Puchi, P.F.; Grieco, E.; Cescatti, A.; Colantoni, A.; Chirici, G.; et al. Stand age diversity (and more than climate change) affects forests’ resilience and stability, although unevenly. J. Environ. Manag. 2024, 366, 121822. [Google Scholar] [CrossRef]
  8. Kerhoulas, L.; Kolb, T.; Koch, G. Tree size, stand density, and the source of water used across seasons by ponderosa pine in northern Arizona. For. Ecol. Manag. 2013, 289, 425–433. [Google Scholar] [CrossRef]
  9. Wu, J.N.; Liu, W.J.; Chen, C.F. How do plants share water sources in a rubber-tea agroforestry system during the pronounced dry season? Agric. Ecosyst. Environ. 2017, 236, 69–77. [Google Scholar] [CrossRef]
  10. Zhu, W.; Zhou, O.; Sun, Y.M.; Li, X.M.; Di, N.; Li, D.D.; Yilihamu, G.; Wang, Y.F.; Fu, J.Y.; Xi, B.Y.; et al. Effects of stand age and structure on root distribution and root water uptake in fast-growing poplar plantations. J. Hydrol. 2023, 616, 128831. [Google Scholar] [CrossRef]
  11. Wang, S.F.; An, J.; Zhao, X.N.; Gao, X.D.; Wu, P.; Huo, G.P.; Robinson, B.H. Age- and climate-related water use patterns of apple trees on China’s Loess Plateau. J. Hydrol. 2020, 582, 124462. [Google Scholar] [CrossRef]
  12. Voltas, J.; Lucabaugh, D.; Chambel, M.R.; Ferrio, J.P. Intraspecific variation in the use of water sources by the Circum-Mediterranean conifer Pinus halepensis. New Phytol. 2015, 208, 1031–1041. [Google Scholar] [CrossRef] [PubMed]
  13. Wu, X.; Zheng, X.J.; Yin, X.W.; Yue, Y.M.; Liu, R.; Xu, G.Q.; Li, Y. Seasonal variation in the groundwater dependency of two dominant woody species in a desert region of Central Asia. Plant Soil 2019, 444, 39–55. [Google Scholar] [CrossRef]
  14. Pei, Y.W.; Huang, L.M.; Shao, M.A.; Zhang, Y.L.; Pan, Y.H. Water use pattern and transpiration of Mongolian pine plantations in relation to stand age on northern Loess Plateau of China. Agric. For. Meteorol. 2023, 330, 109320. [Google Scholar] [CrossRef]
  15. Wang, J.; Fu, B.J.; Jiao, L.; Lu, N.; Li, J.Y.; Chen, W.L.; Wang, L.X. Age-related water use characteristics of Robinia pseudoacacia on the Loess Plateau. Agric. For. Meteorol. 2021, 301–302, 108344. [Google Scholar] [CrossRef]
  16. National Forestry and Grassland Administration. Comprehensive Monitoring and Evaluation Report on Forest and Grassland Ecology in China; China Forestry Publishing House: Beijing, China, 2021. (In Chinese) [Google Scholar]
  17. Gándara, J.; Ross, S.; Quero, G.; Gonzalo, D.; Figarola, G.; Viega, L. Differential water-use efficiency and growth among Eucalyptus grandis hybrids under two different rainfall conditions. For. Syst. 2020, 29, e006. [Google Scholar] [CrossRef]
  18. Campoe, O.C.; Alvares, C.A.; Carneiro, R.L.; Binkley, D.; Ryan, M.G.; Hubbard, R.M.; Stahl, J.; Moreira, G.; Moraes, L.F.; Stape, J.L. Climate and genotype influences on carbon fluxes and partitioning in Eucalyptus plantations. For. Ecol. Manag. 2020, 475, 118445. [Google Scholar] [CrossRef]
  19. Wang, Z.; Du, A.; Xu, Y.; Zhu, W.; Zhang, J. Factors limiting the growth of Eucalyptus and the characteristics of growth and water use under water and fertilizer management in the dry season of Leizhou Peninsula, China. Agronomy 2019, 9, 590. [Google Scholar] [CrossRef]
  20. Ehleringer, J.R.; Roden, J.; Dawson, T.E. Assessing ecosystem-level water relations through stable isotope ratio analyses. In Methods in Ecosystem Science; Sala, O.E., Jackson, R.B., Mooney, H.A., Howarth, R.W., Eds.; Springer: New York, NY, USA, 2000; pp. 181–198. [Google Scholar]
  21. Chen, Y.L.; Helliker, B.R.; Tang, X.H.; Li, F.; Zhou, Y.P.; Song, X. Stem water cryogenic extraction biases estimation in deuterium isotope composition of plant source water. Proc. Natl. Acad. Sci. USA 2020, 117, 33345–33350. [Google Scholar] [CrossRef]
  22. Ehleringer, J.R.; Dawson, T.E. Water uptake by plants: Perspectives from stable isotope composition. Plant Cell Environ. 1992, 15, 1073–1082. [Google Scholar] [CrossRef]
  23. Wang, J.; Fu, B.J.; Wang, L.X.; Lu, N.; Li, J.Y. Water use characteristics of the common tree species in different plantation types in the Loess Plateau of China. Agric. For. Meteorol. 2020, 288–289, 108020. [Google Scholar] [CrossRef]
  24. Stock, B.C.; Semmens, B.X. MixSIAR GUI User Manual, version 3.1; GitHub: San Francisco, CA, USA, 2013.
  25. Zheng, W.B.; Wang, S.Q.; Sprenger, M.; Liu, B.X.; Cao, J.S. Response of soil water movement and groundwater recharge to extreme precipitation in a headwater catchment in the North China Plain. J. Hydrol. 2019, 576, 466–477. [Google Scholar] [CrossRef]
  26. Pettit, N.E.; Froend, R.H. How important is groundwater availability and stream perenniality to riparian and floodplain tree growth? Hydrol. Process. 2018, 32, 1–13. [Google Scholar] [CrossRef]
  27. Zhu, G.F.; Yong, L.L.; Zhao, X.; Liu, Y.W.; Zhang, Z.X.; Xu, Y.X.; Sun, Z.G.; Sang, L.Y.; Wang, L. Evaporation, infiltration and storage of soil water in different vegetation zones in the Qilian Mountains: A stable isotope perspective. Hydrol. Earth Syst. Sci. 2022, 26, 3771–3784. [Google Scholar] [CrossRef]
  28. Sun, F.H.; Xiao, B.; Ghanbarian, B. Increasing effect of biocrusts on evaporation is evidenced by simulating evaporation and diffusion experiments and water stable isotope analysis. J. Hydrol. 2024, 637, 131427. [Google Scholar] [CrossRef]
  29. Yong, L.L.; Zhu, G.F.; Wan, Q.Z.; Xu, Y.X.; Zhang, Z.X.; Sun, Z.G.; Ma, H.Y.; Sang, L.Y.; Liu, Y.W.; Guo, H.W.; et al. The soil water evaporation process from mountains based on the stable isotope composition in a headwater basin and northwest China. Water 2020, 12, 2711. [Google Scholar] [CrossRef]
  30. Li, Y.; Huo, S.Y.; Guo, J.; Sun, J.; Pan, J.; Wang, D.; Tan, Q.K.; Pei, B.B. Using hydrogen and oxygen stable isotopes to estimate soil water evaporation loss under continuous evaporation conditions. Hydrol. Process. 2023, 37, e14885. [Google Scholar] [CrossRef]
  31. Xu, Q.; Liu, S.R.; Wan, X.C.; Jiang, C.Q.; Song, X.F.; Wang, J.X. Effects of rainfall on soil moisture and water movement in a subalpine dark coniferous forest in southwestern China. Hydrol. Process. 2012, 26, 3800–3809. [Google Scholar] [CrossRef]
  32. Gazis, C.; Feng, X. A stable isotope study of soil water: Evidence for mixing and preferential flow paths. Geoderma 2004, 119, 97–111. [Google Scholar] [CrossRef]
  33. Benettin, P.; Volkmann, T.H.M.; von Freyberg, J.; Frentress, J.; Penna, D.; Dawson, T.E.; Kirchner, J.W. Effects of climatic seasonality on the isotopic composition of evaporating soil waters. Hydrol. Earth Syst. Sci. 2018, 22, 2881–2890. [Google Scholar] [CrossRef]
  34. Wei, L.Z.; Qiu, Z.J.; Zhou, G.Y.; Zuecco, G.; Liu, Y.; Wen, Y. Soil water hydraulic redistribution in a subtropical monsoon evergreen forest. Sci. Total Environ. 2022, 835, 155437. [Google Scholar] [CrossRef] [PubMed]
  35. Wang, S.T.; Zhu, G.F.; Bai, W.W.; Yuan, R.P.; Zhang, Y. Root distribution and water uptake applied by hydrogen and oxygen stable isotopes for lianas in northwest China. Forests 2024, 15, 626. [Google Scholar] [CrossRef]
  36. Sprenger, M.; Leistert, H.; Gimbel, K.; Weiler, M. Illuminating hydrological processes at the soil-vegetation-atmosphere interface with water stable isotopes. Rev. Geophys. 2016, 54, 674–704. [Google Scholar] [CrossRef]
  37. McCole, A.A.; Stern, L.A. Seasonal water use patterns of Juniperus ashei on the Edwards Plateau, Texas, based on stable isotopes in water. J. Hydrol. 2007, 342, 238–248. [Google Scholar] [CrossRef]
  38. Nie, Y.P.; Chen, H.S.; Wang, K.L.; Tan, W.; Deng, P.Y.; Yang, J. Seasonal water use patterns of woody species growing on the continuous dolostone outcrops and nearby thin soils in subtropical China. Plant Soil 2011, 341, 399–412. [Google Scholar] [CrossRef]
  39. Yang, B.; Wen, X.F.; Sun, X.M. Seasonal variations in depth of water uptake for a subtropical coniferous plantation subjected to drought in an East Asian monsoon region. Agric. For. Meteorol. 2015, 201, 218–228. [Google Scholar] [CrossRef]
  40. Gao, D.Q.; Xu, Q.; Zuo, H.J.; Xu, W.B.; Diao, K.; Zhang, B.B. Changes in water uptake patterns of trees in forests across a successional gradient in southern China. Forests 2024, 15, 1329. [Google Scholar] [CrossRef]
  41. Yu, Z.C.; Zheng, X.T.; He, W.; Lin, W.; Yan, G.Z.; Zhu, H.; Peng, C.L. Different responses of macro- and microelement contents of 41 subtropical plants to environmental changes in the wet and dry seasons. J. Plant Ecol. 2023, 16, rtad027. [Google Scholar] [CrossRef]
  42. Li, Y.H.; Zhang, X.D.; Liu, M.; Wang, C.T.; Manuel, L.; Hu, L. Precipitation-induced soil properties and plant communities mediate root strategies in an alpine meadow. J. Plant Ecol. 2024, 17, rtae072. [Google Scholar] [CrossRef]
  43. Zhang, Z.Z.; Zhao, P.; McCarthy, H.R.; Ouyang, L.; Niu, J.F.; Zhu, L.W.; Ni, G.Y.; Huang, Y.Q. Hydraulic balance of a Eucalyptus urophylla plantation in response to periodic drought in low subtropical China. Front. Plant Sci. 2016, 7, 1346. [Google Scholar] [CrossRef]
  44. Schume, H.; Hailu, Z.; Hailu, T.; Sieghardt, M.; Godbold, D.L. Spatial analysis of soil water depletion and biomass production in the transition zone between a Eucalyptus camaldulensis stand and a maize field in Ethiopia. Agric. For. Meteorol. 2022, 320, 108956. [Google Scholar] [CrossRef]
  45. Yin, H.; Wu, Z.Y.; He, H. Interpreting seasonal droughts over the Yangtze River Basin utilizing anomalies of local-scale atmospheric circulation. J. Hydrol. 2025, 58, 102231. [Google Scholar] [CrossRef]
  46. Wu, J.J.; Wang, J.Y.; Hui, W.K.; Zhao, F.Y.; Wang, P.Y.; Su, C.Y.; Gong, W. Physiology of plant responses to water stress and related genes: A review. Forests 2022, 13, 324. [Google Scholar] [CrossRef]
Forests 16 00708 g001
Figure 1. Location of study area and sceneries of sample sites.
Figure 1. Location of study area and sceneries of sample sites.
Forests 16 00708 g001
Forests 16 00708 g002
Figure 2. Daily precipitation and average air temperature from April 2023 to June 2024: growing season (April to October) and non-growing season (November to March).
Figure 2. Daily precipitation and average air temperature from April 2023 to June 2024: growing season (April to October) and non-growing season (November to March).
Forests 16 00708 g002
Forests 16 00708 g003
Figure 3. Dynamic changes in the soil water content of Eucalyptus plantations of different ages during dry and wet seasons.
Figure 3. Dynamic changes in the soil water content of Eucalyptus plantations of different ages during dry and wet seasons.
Forests 16 00708 g003
Forests 16 00708 g004
Figure 4. δD in xylem water and soil water in Eucalyptus plantations of different ages in August 2023 and April 2024.
Figure 4. δD in xylem water and soil water in Eucalyptus plantations of different ages in August 2023 and April 2024.
Forests 16 00708 g004
Forests 16 00708 g005
Figure 5. The contributions of each soil layer to the xylem water of Eucalyptus of different ages in August 2023 and April 2024.
Figure 5. The contributions of each soil layer to the xylem water of Eucalyptus of different ages in August 2023 and April 2024.
Forests 16 00708 g005
Table 1. Site characteristics of Eucalyptus stands of different ages.
Table 1. Site characteristics of Eucalyptus stands of different ages.
Stand Age
(a)		Geographic
Location		Altitude
(m)		Average DBH
(cm)		Average Height
(m)		Density
(Tree∙ha−1)
4108°11′46″ E
22°43′58″ N		176–18712191248
7108°11′54″ E
22°41′24″N		201–20817241112
17108°11′43″ E
22°44′27″ N		174–1813437735
Note: DBH stands for diameter at breast height.
Table 2. Soil texture at 0–150 cm depth in Eucalyptus plantations of different ages.
Table 2. Soil texture at 0–150 cm depth in Eucalyptus plantations of different ages.
Stand Age (a)Soil Texture (%)Soil Depth (cm)
0–2020–4040–6060–9090–150
4Clay23.734.532.624.426.5
Silt46.835.426.138.934.3
Sand29.530.141.336.739.2
7Clay26.232.124.922.825.4
Silt38.537.240.536.330.5
Sand35.330.734.640.944.1
17Clay24.835.230.126.920.2
Silt33.940.236.538.447.5
Sand41.324.633.434.732.3
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zuo, H.; Xu, Q.; Gao, D.; Xu, W.; Diao, K.; Zhang, B. Seasonal Water Use Patterns of Eucalyptus with Different Ages in Southern Subtropical China. Forests 2025, 16, 708. https://doi.org/10.3390/f16040708

AMA Style

Zuo H, Xu Q, Gao D, Xu W, Diao K, Zhang B. Seasonal Water Use Patterns of Eucalyptus with Different Ages in Southern Subtropical China. Forests. 2025; 16(4):708. https://doi.org/10.3390/f16040708

Chicago/Turabian Style

Zuo, Haijun, Qing Xu, Deqiang Gao, Wenbin Xu, Ke Diao, and Beibei Zhang. 2025. "Seasonal Water Use Patterns of Eucalyptus with Different Ages in Southern Subtropical China" Forests 16, no. 4: 708. https://doi.org/10.3390/f16040708

APA Style

Zuo, H., Xu, Q., Gao, D., Xu, W., Diao, K., & Zhang, B. (2025). Seasonal Water Use Patterns of Eucalyptus with Different Ages in Southern Subtropical China. Forests, 16(4), 708. https://doi.org/10.3390/f16040708

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop