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Table of Content
    Volume 48 Issue 9
    20 September 2024
    Spring landscape of Lushan Botanical Garden (Photographed by Lushan Botanical Garden). Niu et al. analyzed the dynamic changes of transpiration water age and water utilization strategies for four typical tree species at different altitudes based on meteorological data, soil moisture, soil and vegetation moisture stable isotope at different altitudes in Lushan area. The findings help reduce uncertainties in hydrological and climate modeling and provide scientific support for vegetation [Detail] ...
      
    Research Articles
    Water uptake and niche characteristics of neighboring plants for arbors and shrubs under different rainfall conditions in a rocky mountainous area, Beijing
    ZHOU Hong-Juan, LIU Zi-He, LIU Ke-Yan, ZHANG Chu-Rui, HU Xu, HAN Lu, CHEN Li-Xin
    Chin J Plant Ecol. 2024, 48 (9):  1089-1103.  doi: 10.17521/cjpe.2024.0057   cstr: 32100.14.cjpe.2024.0057
    Abstract ( 395 )   Full Text ( 96 )   PDF (1747KB) ( 320 )   Save
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    Aims Our study aims to explore water usage strategies and the competitive or complementary relationships among neighboring arboreal and shrubby plants within the same stand under diverse rainfall conditions. Through an analysis of soil water absorption and water niche characteristics of these neighboring plants, we aim to provide a theoretical basis for vegetation restoration and management in the rocky mountainous areas, Beijing.

    Methods Xylem samples were collected from trees including Robinia pseudoacacia, Koelreuteria paniculata, and Platycladus orientalis, as well as from the shrub Vitex negundo. Additionally, samples of soil, groundwater, and rainwater were gathered both before and 1-4 days following different types of rainfall events: light rain during a dry period, moderate rain during a wet period, and rainstorms during a dry period. These samples were analyzed to examine the characteristics and dynamic changes of hydrogen and oxygen isotopes composition (δ2H and δ18O). The MixSIAR model was employed to determine the contribution rates of groundwater and soil water from different soil layers to various plant species. Furthermore, water niche width and niche overlap were assessed using the Levins index and Levins overlap formula, respectively.

    Important findings The results indicate that soil water content, δ2H and δ18O, water absorption depth, and niche characteristics of neighboring arboreal and shrubby plants were significantly influenced by the types of rainfall. Following light rainfall during a dry period, shrubs exhibited heightened sensitivity to precipitation, shifting their water source from deep soil to upper soil layers, while arboreal species predominantly relied on groundwater. After moderate rainfall during a wet period, arboreal and shrubby plants from different forest types primarily absorbed water from soil layers within the 0-40 cm depth range. Rainstorms during a dry period altered the water utilization strategies of arboreal and shrubby plants, with shrubs predominantly sourcing water from the 0-40 cm soil layers, while arboreal species exhibited more uniform water uptake across different soil layers. The niche width of R. pseudoacacia and K. paniculata was lower compared to corresponding shrubs before and after light rainfall during a dry period, whereas the niche width of K. paniculata exceeded that of understory shrubs both before and after rainstorms during dry periods. Platycladus orientalis and understory shrubs exhibited similar responses to different types of rainfall, with the niche width of P. orientalisexperiencing a sharp increase on the first day following rain, while that of shrubs spiked on the second day post-rainfall. For the dry period before light rainfall, there was a substantial overlap in the water niche between R. pseudoacaciaand understory shrubs, which diminished with an increase in the number of rainfall days thereafter. Except for the dry period before light rainfall, arboreal and shrubby plants demonstrated distinct water utilization strategies across different types of rainfall, thus mitigating water competition between them.

    Dynamic changes of transpiration water age and water utilization strategies for trees at different altitudes in Lushan area
    NIU Yun-Ming, JIA Guo-Dong, WANG Xin, LIU Zi-He
    Chin J Plant Ecol. 2024, 48 (9):  1104-1117.  doi: 10.17521/cjpe.2024.0022   cstr: 32100.14.cjpe.2024.0022
    Abstract ( 260 )   Full Text ( 48 )   PDF (2543KB) ( 192 )   Save
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    Aims To explore the water age of dominant vegetation at different altitudes in Lushan area in the humid climate region and the strategy of water utilization for different aged sources, so as to provide scientific basis for ecological protection and resource utilization in this region.

    Methods Four species of Pinus (P. massoniana at low altitude, P. taiwanensisat high altitude) and Quercus (Q. variabilisat low altitude, Q. serrataat high altitude) from Lushan Mountain were studied, using stable hydrogen and oxygen isotopes technology and linear mixing water age model in order to analyze the transpiration water age of dominant vegetation at different altitudes from July 2020 to August 2021. After then, water age results and the MixSIAR source mixture model were combined to analyze the strategy of water utilization and seasonal changes. Simultaneously monitored included the air temperature and humidity, soil water content, root distribution and others. In the end, the seasonal changes of the transpiration water age and the water sources was analyzed with all the available data.

    Important findings (1) Plants in Lushan area mainly use the seasonal precipitation, and the age of transpiration water is between 8.67 and 16.68 d. For the same genus of species, the transpiration water age of high altitude tree species is smaller than that of low altitude. Moreover, during the observation period, the water age of P. massoniana was “single valley-shaped” and P. taiwanensiswas “single peak-shaped”. (2) The low-altitude tree species mainly uses shallow soil water in the early rainy season. With the going-on of rainy season, the main water-absorbing layer moves down to the deep layer, and is stabilized in the deep soil in the late rainy season. However, in the late rainy season, the high-altitude tree species mainly use the water in the middle soil level. (3) In comparison, for the low-altitude trees, their water source is less dependent on shallow (0-20 cm) soil and absorbs more of deep (60-100 cm) soil water. High altitude is on the opposite.

    Transpiration estimates in Pinus sylvestris var. mongolica plantation based on the radial pattern of sap flow and its influencing factors
    TONG Yu-Qiang, WU Meng-Ge, WANG Ling, ZHAO Shi, HAN Xu, ZHANG Tong, LIU Jing, QIN Sheng-Jin, DONG Ying-Hao, WEI Ya-Wei, ZHOU Yong-Bin
    Chin J Plant Ecol. 2024, 48 (9):  1118-1127.  doi: 10.17521/cjpe.2023.0121   cstr: 32100.14.cjpe.2023.0121
    Abstract ( 181 )   Full Text ( 20 )   PDF (1360KB) ( 110 )   Save
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    Aims Pinus sylvestris var. mongolica is one of the key afforestation species in the semi-arid region of western Liaoning Province. Precise estimation of its transpiration is crucial for the scientific management of these plantations.

    Methods This study utilized multi-point TDP probes with different probe sizes to examine the radial pattern of sap flow in 30-year-old P. sylvestris var. mongolica on sandy terrain, and to explain the factors affecting transpiration.

    Important findings Results revealed significant differences in the radial pattern of sap flow within the plantation, which also varied across seasons. In August, the sap flow exhibited a distinct unimodal radial pattern, peaking at 15 mm depth from sapwood. However, in October, the radial pattern showed a significant difference, presenting a gradual decline from the outer sapwood towards the heartwood. Based on radial sap flow changes, the daily transpiration of 30-year-old P. sylvestris var. mongolica in August and October was estimated to be between 25.32-27.45 and 14.05-16.49 kg, respectively. The transpiration from the outer 0-20 mm of the sapwood accounted for a substantial majority of the whole tree’s transpiration. Estimation of the entire P. sylvestris var. mongolica transpiration based on a single point could lead to significant errors, with the highest error reaching up to 133.22%. There was a notable correlation between sap flux densities at different depths (5, 15, 25 mm) out of sapwood, and a satisfactory linear fit was observed between sap flux density at various depths and weighted mean sap flux density on a sapwood area basis. Thus, a single-point estimation of individual tree transpiration can be achieved using conversion equations. The most significant effect on sap flow at different depths in P. sylvestris var. mongolica was from photosynthetically active radiation. However, the response degree of sap flow at different depths to meteorological factors were different, implying that meteorological influences on whole-tree transpiration cannot be predicted based on the impacts at a single depth.

    Nocturnal sap flow characteristics of two typical forest tree species and responses to environmental factors in the loess region of West Shanxi, China
    FU Zhao-Qi, HU Xu, TIAN Qin-Rui, GE Yan-Ling, ZHOU Hong-Juan, WU Xiao-Yun, CHEN Li-Xin
    Chin J Plant Ecol. 2024, 48 (9):  1128-1142.  doi: 10.17521/cjpe.2023.0219   cstr: 32100.14.cjpe.2023.0219
    Abstract ( 249 )   Full Text ( 57 )   PDF (2284KB) ( 164 )   Save
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    Aims Understanding the nighttime water use of typical forest tree species in the west Loess Plateau is crucial for accurately evaluating the watershed-scale water and carbon cycles. However, the nighttime sap flow dynamics and its response to environmental factors are currently unclear for typical forest species in the west Loess Plateau.

    Methods We monitored the sap flow with thermal dissipation probes (TDP) and concurrent environmental factors of Robinia pseudoacaciaplantation and Quercus mongolica natural forest in the Caijiachuan watershed from June to September 2021. The time series model (ARMAX model) was used to distinguish between nighttime transpiration (Tn) and stem water replenishment (Re) in nocturnal sap flow (QNighttime). We used the machine learning model XGboost and Shapley additive interpretation framework to analyze and explain the relationship between QNighttime and nighttime environmental factors.

    Important findings The proportion of nighttime transpiration (Tn/QNighttime) was 73.97% and 30.12% for the R. pseudoacacia and the Q. mongolica, respectively, during the growing season. The proportion of stem water filling (Re/QNighttime) was 26.03% and 69.88% for the two species, respectively. The XGboost model showed that nighttime vapor pressure deficit (VPD) and nighttime soil water content (SWC) were the main factors driving QNighttime in R. pseudoacacia and Q. mongolica, respectively. VPD, nighttime air temperature (Ta), nighttime relative humidity (RH), and daily sap flow (QDaily) can promote the QNighttime when they reach 0.30 kPa, 19.84 °C, 85.3%, and 339.11 kg·h-1. For Q. mongolica, VPD inhibited QNighttime when it reached 1.5 kPa, while Ta and nighttime wind speed (WS) promoted QNighttime when it reached 23.11 ℃ and 0.58 m·s-1, respectively. The effects of SWC on QNighttime in R. pseudoacacia and Q. mongolica were similar. The SWC within 0-12.9% range would promote the occurrence of QNighttime. Therefore, our study highlights the importance of considering the magnitude of all environmental factors in establishing the nocturnal sap flow model. This study revealed the characteristics of QNighttime composition and their responses to environmental factors of two typical tree species in the west Loess Plateau. Our findings are of great significance for accurately understanding the stability of typical forest tree species in the loess region under climate change.

    Characteristics of canopy stomatal conductance of Populus simonii stands with different degradation degrees and its responses to environmental factors
    ZHANG Xiao-Yu, JIA Guo-Dong, YU Xin-Xiao, SUN Li-Bo, JIANG Tao
    Chin J Plant Ecol. 2024, 48 (9):  1143-1156.  doi: 10.17521/cjpe.2023.0106   cstr: 32100.14.cjpe.2023.0106
    Abstract ( 339 )   Full Text ( 68 )   PDF (1641KB) ( 187 )   Save
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    Aims Canopy stomatal conductance (gs) is an important indicator for measuring canopy atmospheric water vapor exchange. Studying its characteristics and responses to environmental factors could enhance the understanding of canopy water vapor exchange process and the comprehensive mechanism of environmental factors controlling forest canopy. Currently, differences in canopy stomatal conductance characteristics and its responses to environmental factors of the same tree species with different degradation degrees are still unclear.

    Methods In the growing-season of 2019 (May-September), four types of Populus simonii stands with different degrees of degradation (non-degraded, mildly degraded, moderately degraded and severely degraded) in Zhangbei County of Bashang Plateau were selected, and thermal diffusion technology (TDP) probes were set to monitor trunk sap flow continuously. Environmental factors such as photosynthetically active radiation (PAR), vapor pressure deficit (VPD), air temperature (T), relative air humidity (RH) and soil water content (SWC) were monitored synchronously to analyze the sap flow rate and canopy stomatal conductance characteristics of P. simonii and their responses to environmental factors.

    Important findings (1) The daily variation of sap flow rate in P. simonii showed a single-peak curve, while the gs showed a double-peak curve. On the monthly scale, both sap flow rate and gs showed a trend of increasing at first and declining subsequently, and then reaching the highest values in July. The differences in sap flow rate and gs of P. simonii among the four stands of degradation degrees were significant in May and September. (2) The gs was all affected by T, VPD and SWC. However, due to the differences in degradation, gs in the non-degraded stands was mainly affected by T, VPD and 80-160 cm SWC. In the mildly degraded stands gs was mainly affected by T, 0-80 cm SWC and VPD, and that in the moderately degraded was mainly affected by 0-80 cm SWC, T, VPD, while it in the severely degraded was mainly affected by T, PAR and VPD. (3) For the all P. simonii of different degradation degrees, the gs above 18 °C was positively correlated with T. At 0.6-2.2 kPa, it was positively correlated with VPD, while negatively correlated with SWC. The gs of the severely degraded P. simonii was positively correlated PAR when it was below 250 μmol·m-2·s-1. (4) Compared to the other three types of P. simonii, the severely degraded one had a more positive response to T changes and a lower sensitivity to other environmental factors. Due to morphological degradation, control of canopy transpiration of the severely degraded P. simonii will be even stricter to avoid further degradation or dieback.

    Impact of drought on carbon and water fluxes and their coupling in a Quercus variabilis plantation
    WANG Yin, TONG Xiao-Juan, ZHANG Jin-Song, LI Jun, MENG Ping, LIU Pei-Rong, ZHANG Jing-Ru
    Chin J Plant Ecol. 2024, 48 (9):  1157-1171.  doi: 10.17521/cjpe.2023.0354   cstr: 32100.14.cjpe.2023.0354
    Abstract ( 224 )   Full Text ( 27 )   PDF (1933KB) ( 168 )   Save
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    Aims Water use efficiency (WUE) is an important indicator for understanding the carbon and water cycles and coupling mechanisms in terrestrial ecosystems. Inherent water use efficiency (IWUE) is a more suitable indicator than WUE for analyzing the carbon-water coupling mechanism of ecosystems on a daily scale. Here, we aimed to investigate the mechanism of water and carbon fluxes and their responses to drought in a planted forest ecosystem.

    Methods We carried out an in-situobservation on the water and carbon fluxes and environmental factors in a Quercus variabilisplantation using eddy covariance techniques and the micrometeorological observation system. The effects of biophysical factors on the gross primary productivity (GPP), evapotranspiration (ET), and IWUE during 2021-2022 were analyzed.

    Important findings GPP, ET, and IWUE showed obvious seasonal variations. GPP and ET in the wet year were 7.9% and 21.0% higher than those in the normal year, respectively, whereas IWUE in the wet year was 21.4% lower than that in the normal year. Vapor pressure deficit (VPD) was the main factor affecting GPP in the normal year, and net radiation (Rn) was the primarily factor limiting GPP in the wet year. ET was mainly determined by Rn in both normal and wet years. Relative extractable soil water (REW) was the main factor regulating IWUE in the normal year, whereas leaf area index (LAI) was the main factor controlling IWUE in the wet year. Environmental factors regulated carbon and water fluxes by affecting canopy conductance, and consequently impacting IWUE. The occurrence of soil drought significantly increased IWUE. The response of GPP and ET to REW showed a time lag of 1 month, while the response of IWUE to REW had no lag.

    Responses of stem sap flow of Haloxylon ammodendron to rainfall pulses in Ulan Buh Desert
    HAN Yu-Qing, XIONG Wei, WU Bo, LU Qi, YANG Wen-Bin, LIU Ya-Li, ZHANG Jing-Bo, XIN Zhi-Ming, MA Ying-Bin, LIAN Hong-Lin, WANG Si-Han
    Chin J Plant Ecol. 2024, 48 (9):  1172-1179.  doi: 10.17521/cjpe.2023.0168   cstr: 32100.14.cjpe.2023.0168
    Abstract ( 155 )   Full Text ( 30 )   PDF (1219KB) ( 121 )   Save
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    Aims Quantifying the responses of eco-hydrological processes of desert plants to rainfall pulses is the key to understand the impact of climate change in dryland ecosystem. Our objective was to explore the responses of stem sap flow of Haloxylon ammodendron to rainfall pulses in a H. ammodendron plantation in the Ulan Buh Desert.

    Methods From June to October 2020, the stem sap flow of H. ammodendron, micrometeorological factors and soil moisture in the plantation were continuously observed by thermal diffusion probes as well as the hydrometeorological methods, to analyze the characteristics of stem sap flux density (SFD) of H. ammodendron and its response to rainfall.

    Important findings (1) The average daily SFD was 0.044 g·cm-2·min-1 after the rain, which was 1.16 times of that before the rain among the selected 17 rainfall events during the study period. The diurnal variation of SFD were changed from “bimodal pattern” before rain to “unimodal pattern” after rain for 9 of the all events. The characteristic value of daily SFD fluctuation were obviously changed after the other 8 rains. For example, the initiation time of SFD after rain were earlier from 8:00 before rain to 7:00 in the morning. And its peak values of daily SFD were also increased from 0.067 g·cm-2·min-1 before rain to 0.085 g·cm-2·min-1, and the duration of the peak interval was significantly extended. (2) The impacts of rainfall pulses on the sap flow of H. ammodendron could be well described with the threshold delay model (T-D model). And the lowest rainfall threshold and the lag time of SFD responded to rain were 0.8 mm and 1.71 d, respectively, indicating that the sap flow of this shrub species was sensitive to rainfall pulses and had a certain lag. (3) The SFD of H. ammodendron was significantly positive correlated with atmospheric temperature, vapor pressure deficit, solar radiation, wind speed and soil volumetric water content, and significantly negative correlated with the relative humidity, but no significant correlated with rainfall, suggesting that SFD of H. ammodendronwould be indirectly affected by rainfall pulses by changing the physiological characteristics of the species as well as soil water condition. Our results are helpful to further understand the water use characteristics of desert plants and their response to climate change, and are of great significance for the sustainable management of artificial sand-fixation forests in future.

    Spatial-temporal variation of water use efficiency in three species of sand-fixing shrubs on the Ordos Plateau
    WU Feng-Yan, WU Yong-Sheng, CHEN Xiao-Han, FENG Ji, LU Li-Yuan, CHASINA , WANG Chao-Yu, MENG Yuan-Fa, YIN Qiang
    Chin J Plant Ecol. 2024, 48 (9):  1180-1191.  doi: 10.17521/cjpe.2023.0266   cstr: 32100.14.cjpe.2023.0266
    Abstract ( 169 )   Full Text ( 26 )   PDF (1934KB) ( 124 )   Save
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    Aims To evaluate the adaptability of Salix psammophila, Artemisia ordosica and Caragana korshinskii to different hydrothermal gradients.

    Methods In this paper, fixed sample plots were established in the areas of Dalad Banner and Uxin Banner, Ordos City and Jingbian County, Yulin City, respectively, to study the carbon stable isotope composition (δ13C) and water use efficiency (WUE) of the leaves of the above three types of sand-fixing plants during the months of July to September, and to analyze the relationships between the WUE of the different types of sand-fixing plants and air temperature, precipitation and aridity index (AI).

    Important findings The results showed that: (1) The δ13C and WUE values were highest in C. korshinskii, and lowest in A. ordosica, and these values were significantly higher in July than in August and September; (2) for Salix psammophila, leaf δ13C and WUE did not exhibit a systematic trend with the increase in AI, while in Dalad Banner, where AI was the highest, leaf δ13C and WUE were significantly higher than Uxin Banner and Jingbian County in C. korshinskii and A. ordosica; the results of multifactorial ANOVA showed that the plant species and the spatial differences in which they were located had the greatest influence on plant δ13C and WUE; (3) The results of linear regression analysis showed that air temperature, precipitation and AI significantly affected WUE, except for C. korshinskii WUE, which had no significant effect on air temperature changes. among them, C. korshinskii WUE was the most sensitive to changes in AI, S. psammophila was more sensitive to changes in air temperature, while WUE of A. ordosica had a smoother response to changes in the above environmental factors.

    Water- and carbon-related physiological mechanisms underlying the decline of wild apricot trees in Ili, Xinjiang, China
    OUYANG Yi-Lei, GONG Xue-Wei, DUAN Chun-Yang, ZHANG Chi, MA Chen-Yang, HAN Peng, ZHANG Yuan-Ming, HAO Guang-You
    Chin J Plant Ecol. 2024, 48 (9):  1192-1201.  doi: 10.17521/cjpe.2023.0110   cstr: 32100.14.cjpe.2023.0110
    Abstract ( 212 )   Full Text ( 50 )   PDF (1640KB) ( 163 )   Save
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    Aims Wild apricot (Prunus armeniaca var. ansu) in Xinjiang of China, one of the origin species of apricot cultivars around the world, has important economical and ecological values, whereas natural apricot forests in Xinjiang have experienced serious decline and mortality in recent years. It is of great significance to carry out research on the underlying mechanisms for the conservation and recovery of wild apricots in Xinjiang.

    Methods In the present study, the xylem hydraulic properties and tissue non-structural carbohydrate (NSC) contents of relatively healthy (dead branches ≤30%) and seriously declined (dead branches ≥70%) wild apricot trees in Ili, Xinjiang were compared to analyze the potential role of hydraulic dysfunction and carbon imbalance in mediating the decline and mortality of this species.

    Important findings The results showed that the seriously declined apricot trees had significantly lower leaf area at the branch level, but there were no significant differences in leaf mass per area, relative chlorophyll content and stomatal conductance between the severely declined and relatively healthy trees. The midday leaf water potential, branch hydraulic efficiency and embolism resistance of seriously declined apricot trees were significantly lower than those of relatively healthy ones, indicating an evident xylem hydraulic impairment. The total NSC content of seriously declined trees was lower than that of relatively healthy trees, but the soluble sugar-to-starch content ratio in the stem xylem of seriously declined trees was significantly higher. Impaired hydraulic functioning was accompanied by decreased carbon assimilation capacity and reduced NSC reserve. On top of hydraulic dysfunction, carbon imbalance further contributed to the weakening of tree defense against scale insects, eventually leading to the decline and mortality of apricot trees due to the interplay between plant water relations and carbon economy.

    Water utilization strategy of Ziziphus jujuba under different sand cover thicknesses based on stable isotope tracing
    LI Bei-Bei, ZHANG Ming-Jun, CHE Cun-Wei, LIU Ze-Chen, ZHONG Xiao-Fei, ZHANG Yuan-Yuan, ZHANG Yu
    Chin J Plant Ecol. 2024, 48 (9):  1202-1212.  doi: 10.17521/cjpe.2023.0295   cstr: 32100.14.cjpe.2023.0295
    Abstract ( 140 )   Full Text ( 25 )   PDF (1380KB) ( 131 )   Save
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    Aims Sand cover conditions in arid zones significantly affect soil water status, which in turn affects the utilization of soil water by vegetation. However, little is known about the water uptake strategies of Ziziphus jujuba under different sand cover conditions and its dynamic response to input water.

    Methods In this study, the water utilization strategies of Z. jujuba under different sand cover thicknesses and their responses to input water were investigated using the hydroxide stable isotope method combined with a Bayesian mixed model (MixSIAR).

    Important findings We found that the peak of soil water content (SWC) appeared on the 2nd day after irrigation in the non-sand-covered sample plots, on the 4th day after irrigation in the 5 cm sand-covered sample plots, and on the 6th day after irrigation in the 10 and 15 cm sand-covered sample plots. Sand cover significantly increased the SWC, and enhanced the water retention of the soil. The oxygen stable isotope composition (δ18O) and hydrogen stable isotope composition (δ2H) were -5.4‰- -2.2‰ and -76.1‰- -61.0‰ in the non-sand-covered sample plots, and -5.6‰- -3.0‰ and -61.0‰- -75.7‰ in the sand-covered sample plots, respectively. The 2nd, 4th, and 6th day after irrigation, the percentage of water utilization by Z. jujuba in the 0-10 cm soil layer without sand cover (16.2%, 9.1%, 10.0%) was stable compared with that in the 5, 10, 15 cm sand-covered sample plots (73.0%, 54.5%, 37.0%; 49.0%, 46.2%, 22.8%; 27.1%, 36.1%, 21.4%) and sand-covering measures increased the date palm’s water utilization of the 0-10 cm soil water. The sand mulching measures increased the utilization of 0-10 cm soil water by Z. jujuba, i.e. there was a lag in the utilization of deep soil water by Z. jujuba. The above results show that sand mulching can effectively improve the water retention of soil and influence the water utilization strategy of plants, which has implications for the adaptation of plants to local drought conditions and other environmental changes.

    Xylem embolism characteristics and hydraulic safety risks of nine tree species in Qinling Mountains
    CHEN Si-Yi, TANG Yan, HE Teng, JIANG Yong-Kang, DU Guang-Yuan
    Chin J Plant Ecol. 2024, 48 (9):  1213-1222.  doi: 10.17521/cjpe.2023.0176   cstr: 32100.14.cjpe.2023.0176
    Abstract ( 325 )   Full Text ( 59 )   PDF (1143KB) ( 181 )   Save
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    Aims Climate warming exacerbate vulnerability of forest ecosystem in the Qinling Mountains, leading to increased forest mortality, and declined ecological function. The objectives of this study were to investigate xylem embolism vulnerability and hydraulic safety margin of nine tree species in the Qinling Mountains.

    Methods In this study, nine tree species of the Qinling Mountains, Betula albosinensis, Corylus ferox, Acer davidii, Acer maximowiczii, Quercus acutissima, Quercus aliena, Pinus armandii, Picea asperata and Larix principis-rupprechtii in two different forest sites, Xunyangba village in mid altitude and Pingheliang ridge in high altitude, were studied. Cochard centrifugation and Sperry centrifugation methods were used to establish vulnerability curves (VCs), which was defined as the percentage loss of hydraulic conductivity (PLC) vs. xylem water potential. The xylem maximum hydraulic conductivity (Kmax) of branches was measured by low pressure flowmeter. The midday xylem water potential (Pmd) was determined by the pressure chamber, which was used to obtain the hydraulic safety margin (HSM) to assess the risk of hydraulic failure for each tree species in natural conditions.

    Important findings 1) Xylem embolism vulnerability of nine species was ranked as Picea asperata < Larix principis-rupprechtii < Pinus armandii < Acer davidii < Acer maximowiczii < Betula albosinensis < Quercus aliena < Corylus ferox < Quercus acutissima. The HSM was ranked as Picea asperata > Pinus armandii > Acer davidii > Acer maximowiczii > Quercus aliena > Larix principis-rupprechtii > Betula albosinensis > Corylus ferox > Quercus acutissima. 2) The six broadleaf species in the Qinling Mountains had less negative 50% PLC water potential (P50) and narrower HSM in average than the three conifer species, and therefore were under greater risk of hydraulic failure. 3) The HSM of B. albosinensis, C. ferox and Q. acutissima were close to 0, which indicated an extremely high risk of xylem embolism. In conclusion, broadleaf species in Qinling Mountains had higher water transport efficiency than conifer species, in the cost of higher risk of xylem embolism and hydraulic failure.

    Hydraulic regulation strategies of karst forest species exhibit variation across different successional stages in the mid-subtropical zone
    LIAO Su-Hui, NI Long-Kang, QIN Jia-Shuang, TAN Yu, GU Da-Xing
    Chin J Plant Ecol. 2024, 48 (9):  1223-1231.  doi: 10.17521/cjpe.2024.0004   cstr: 32100.14.cjpe.2024.0004
    Abstract ( 272 )   Full Text ( 21 )   PDF (1128KB) ( 189 )   Save
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    Aims The karst region encounters challenges such as low resistance to drought and delayed succession due to extensively exposed rocks and shallow soil layers, rendering the surface susceptible to dehydration. The study aims to investigate changes in hydraulic regulation strategies during different successional stages of species of subtropical karst forests. This exploration seeks to understand the mechanisms for adapting to drought following succession, and to establish a theoretical basis for vegetation restoration and reconstruction.

    Methods The study centered on dominant species in forest communities along the early, middle, and late stages of succession in karst areas. Various hydraulic traits including the vulnerability of embolism in stems and leaves (P50S and P50L), the vulnerability segmentation (P50L-S), the specific conductivity of stems and leaves (KS and KL), the hydraulic safety margin of leaf (HSML), density of sapwood, the Huber value, and the specific leaf area (SLA) were investigated.

    Important findings (1) No trade-off was found between hydraulic safety and efficiency at either species or community level; P50S, KS, and KL all decreased along the succession. (2) All species exhibited positive vulnerability segmentation, ranging from 0.53 to 6.59 MPa, and the vulnerability segmentation during early succession significantly exceeded those in the middle and late stages of succession. Furthermore, P50S was identified as the primary determinant of the vulnerability segmentation. (3) The plants at early successional stage exhibited higher resistance to embolism, KS, and KL, which enhance the abilities of water transport and drought resistance. Conversely, in the later stage, plants showed larger SLA to improve competition for light resources. Our study reveals the patterns of adjustment of hydraulic regulation strategies, shifting from strategies aimed at improving hydraulic efficiency and safety to strategies aimed at increasing investment in photosynthetic carbon during the succession process of karst forest plants. This provides a theoretical basis to elucidate the mechanisms of adaptation to drought of plants in the succession process of karst forest communities.

    Effects of warming and nitrogen and phosphorus addition on dissolved organic carbon biodegradability of litter in a subtropical forest
    RAN Jia-Xin, ZHANG Yu-Hui, WANG Yun, YANG Zhi-Jie, MAO Chao
    Chin J Plant Ecol. 2024, 48 (9):  1232-1242.  doi: 10.17521/cjpe.2023.0272   cstr: 32100.14.cjpe.2023.0272
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    Aims The biodegradability of dissolved organic carbon (DOC) is crucial to affect the amount of soil organic carbon in forest ecosystems as litter-derived DOC is one of the important sources of soil DOC. To further understand the formation and stability of forest soil organic carbon under climate change scenarios, it is essential to focus on the effects of climate warming and nutrient addition on the biodegradability of DOC (BDOC).

    Methods Based on a manipulative soil warming experiment in a subtropical evergreen broadleaf forest, we took leaf litter of Castanopsis kawakamii with 0-day decomposition (undecomposed stage) and 180-day decomposition (middle-late stage of decomposition) as research materials. We experimentally quantified the effects of warming and nitrogen and phosphorus addition and their interactions on the BDOC of litter and the corresponding variation in ultraviolet-visible spectral index (ΔDOC spectral index) at different decomposition stages.

    Important findings The results showed that: (1) the BDOC decreased gradually with litter decomposition, with a 22.6% reduction at the middle-late stage of decomposition compared to the undecomposed stage. (2) Warming significantly enhanced the BDOC at undecomposed stage while had no significant effects at the middle-late stage. Similarly, warming significantly increased the ΔDOC spectral index of undecomposed litter, but not at the milled-late stage. (3) Nitrogen addition significantly decreased BDOC at undecomposed stage but increased it at the middle-late stage. However, nitrogen addition did not change ΔDOC spectrum index at both decomposition stages. (4) Phosphorus addition significantly enhanced BDOC and ΔDOC spectrum index at both decomposition stages. (5) The interaction between warming and nutrient addition also had significant effects on increasing BDOC and ΔDOC spectrum index. Overall, both warming and phosphorus addition accelerated the degradation of DOC derived from undecomposed litter, while the degradation of DOC derived from middle-late decomposed litter was mainly regulated by nutrient contents.


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