Spatiotemporal variations in the growth status of declining wild apple trees in a narrow valley in the western Tianshan Mountains, China

doi:10.1007/s40333-022-0087-8

Journal of Arid Land

2022, Vol. 14

Issue (12): 1413-1439 DOI: 10.1007/s40333-022-0087-8 CSTR: 32276.14.s40333-022-0087-8

Research article

Spatiotemporal variations in the growth status of declining wild apple trees in a narrow valley in the western Tianshan Mountains, China

QIU Dong¹^,², TAO Ye², ZHOU Xiaobing², Bagila MAISUPOVA³, YAN Jingming², LIU Huiliang², LI Wenjun², ZHUANG Weiwei¹^,^*(

), ZHANG Yuanming²^,^*(

)

¹Xinjiang Key Laboratory of Special Species Conservation and Regulatory Biology/Key Laboratory of Special Environment Biodiversity Application and Regulation in Xinjiang/Key Laboratory of Plant Stress Biology in Arid Land/College of Life Sciences, Xinjiang Normal University, Urumqi 830054, China
²State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
³Kazakh Scientific Research Institute of Forestry and Agroforestry, Astana 010000, Kazakhstan

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Abstract

Malus sieversii (wild apple tree), only distributed in the Tianshan Mountains in Central Asia, is a tertiary relic species and an ancestral species of cultivated apples. However, existing natural populations of wild apple trees have been declining. To date, spatiotemporal variations in the growth status of declining wild apple trees and influencing factors in the narrow valley areas in the Tianshan Mountains remain unclear. In this study, field investigation and sampling were carried out in three years (2016-2018) at four elevations (1300, 1400, 1500, and 1600 m) in the Qiaolakesai Valley (a typical longitudinal narrow valley in the Yili River Valley) of the western Tianshan Mountains in Xinyuan County, Xinjiang Uygur Autonomous Region, China. Projective coverage, dead branch percentage, and 18 twig traits (these 20 parameters were collectively referred to as plant traits) were determined to comprehensively reflect the growth status of declining wild apple trees. The values of dead branch percentage ranged from 36% to 59%, with a mean of 40%. Year generally showed higher impact on plant traits than elevation. In 2017 and 2018, projective coverage, leaf size, leaf nitrogen concentration, and nitrogen to phosphorous ratio were markedly higher than those in 2016. However, dead branch percentage and leaf and stem phosphorous concentrations showed the opposite trend. Most of the topological parameters of plant trait networks differed in the three years, but the strength of trait-trait association increased year by year. The mean difference between day and night temperatures (MDT), annual accumulative precipitation, soil electrical conductivity, and soil pH had the greatest impact on the plant trait matrix. The growth status of declining wild apple trees was directly and positively affected by MDT and leaf size. In conclusion, the growth of declining wild apple trees distributed in the narrow valley areas was more sensitive to interannual environmental changes than elevation changes. The results are of great significance for further revealing the decline mechanism of wild apple trees in the Tianshan Mountains.

Key words： Malus sieversii plant attributes plant trait network elevation gradient meteorological factor western Tianshan Mountains

Received: 14 March 2022 Published: 31 December 2022

Corresponding Authors: ^*ZHUANG Weiwei (E-mail: zww8611@sina.com);ZHANG Yuanming (E-mail: ymzhang@ms.xjb.ac.cn)

About author: First author contact:The first and second authors contributed equally to this work.

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	QIU Dong
	TAO Ye
	ZHOU Xiaobing
	Bagila MAISUPOVA
	YAN Jingming
	LIU Huiliang
	LI Wenjun
	ZHUANG Weiwei
	ZHANG Yuanming

Cite this article:

QIU Dong, TAO Ye, ZHOU Xiaobing, Bagila MAISUPOVA, YAN Jingming, LIU Huiliang, LI Wenjun, ZHUANG Weiwei, ZHANG Yuanming. Spatiotemporal variations in the growth status of declining wild apple trees in a narrow valley in the western Tianshan Mountains, China. Journal of Arid Land, 2022, 14(12): 1413-1439.

URL:

http://jal.xjegi.com/10.1007/s40333-022-0087-8 OR http://jal.xjegi.com/Y2022/V14/I12/1413

Fig. 1 Location of the study area (the Qiaolakesai Valley) in the Yili River Valley of the western Tianshan Mountains in Xinyuan County, Xinjiang Uygur Autonomous Region, China (a) and the distribution of sampling sites of declining wild apple trees at four elevations in the Qiaolakesai Valley (near the Yili Botanical Garden) (b). Note that no wild apple trees are distributed at elevations lower than 1300 m and higher than 1600 m. DEM, digital elevation model.

Fig. S1 Plant height (a) and basal diameter (b) of declining wild apple trees at different elevations in the Qiaolakesai Valley in 2016. Different lowercase letters indicate significant differences among the four elevations (P<0.05).

Table S1 Coefficients of variation for 20 plant traits of declining wild apple trees in the Qiaolakesai Valley

Fig. 2 Differences in projective coverage (PC; a) and dead branch percentage (DBP; b) of declining wild apple trees at different elevations in different years in the Qiaolakesai Valley. Different capital and lowercase letters indicate significant differences (P<0.05) among the four elevations in the same year and among the three years at the same elevation, respectively. A summary of the results of a repeated measures ANOVA (F value) addressing the effects of year and elevation is shown in the upper part of each panel. ^** indicates that F value is significant at P<0.01 level; ^ns means no significance (P>0.05).

Fig. S2 Differences in projective coverage (PC; a), dead branch percentage (DBP; b), individual leaf area (LA; c), individual leaf weight (LW; d), and leaf mass per area (LMA; e) of declining wild apple trees at different elevations in the Qiaolakesai Valley in 2016. Different lowercase letters indicate significant differences among the four elevations (P<0.05).

Fig. S3 Differences in PC (a), DBP (b), LA (d), LW (d), and LMA (e) of declining wild apple trees among the three years in the Qiaolakesai Valley. Different lowercase letters indicate significant differences among the three years (P<0.05).

Table 1 Summary of repeated measures ANOVA (F value) on twig traits of declining wild apple trees at different elevations in different years in the Qiaolakesai Valley

Fig. 3 Differences in individual leaf area (LA; a), individual leaf weight (LW; b), and leaf mass per area (LMA; c) of declining wild apple trees at different elevations in different years in a typical valley in the Qiaolakesai Valley. Different capital and lowercase letters indicate significant differences (P<0.05) among the four elevations in the same year and among the three years at the same elevation, respectively.

Fig. 4 Differences in leaf nutrient concentrations per unit mass (a, c, e) and leaf nutrient concentrations per unit area (b, d, f) of declining wild apple trees at different elevations in different years in the Qiaolakesai Valley. N, nitrogen; P, phosphorus; K, potassium. N_mass, P_mass, and K_mass indicate leaf N, P, and K concentrations per unit mass, respectively. N_area, P_area, and K_area indicate leaf N, P, and K concentrations per unit area, respectively. Different capital and lowercase letters indicate significant differences (P<0.05) among the four elevations in the same year and among the three years at the same elevation, respectively.

Fig. S4 Differences in leaf N_mass, P_mass, and K_mass concentrations (a, b, and c), leaf N_area, P_area, and K_area concentrations (d, e, and f), and leaf stoichiometric ratios (g, h, and i) of declining wild apple trees at different elevations in the Qiaolakesai Valley. N, nitrogen; P, phosphorus; K, potassium. N_mass, P_mass, and K_mass indicate leaf N, P, and K concentrations per unit mass, respectively. N_area, P_area, and K_area indicate leaf N, P, and K concentrations per unit area, respectively. Different lowercase letters indicate significant differences among the four elevations (P<0.05).

Fig. S5 Differences in leaf N_mass, P_mass, and K_mass concentrations (a, b, and c), leaf N_area, P_area, and K_area concentrations (d, e, and f), and the stoichiometric ratios (g, h, and i) of declining wild apple trees among three years in the Qiaolakesai Valley. Different lowercase letters indicate significant differences among the three years (P<0.05).

Table S2 Differences in the current-year stem stoichiometric parameters of declining wild apple trees among different elevations or years in the Qiaolakesai Valley

Fig. 5 Differences in leaf N:P (a), N:K (b), and P:K (c) of declining wild apple trees at different elevations in different years in the Qiaolakesai Valley. Different capital and lowercase letters indicate significant differences (P<0.05) among the four elevations in the same year and among the three years at the same elevation, respectively.

Fig. 6 Plant trait networks (PTNs) of declining wild apple trees sampled in 2016 (a), 2017 (b), and 2018 (c) in the Qiaolakesai Valley. Green nodes represent different plant traits, and node size shows degree. Red and blue lines indicate positive and negative correlations, respectively. The thickness of the line indicates the association strength. Blue solid circle indicates the hub trait.

Table S3 Topological properties of plant trait networks (PTNs) of declining wild apple trees in different years in the Qiaolakesai Valley

Table S4 Node (plant trait) properties of PTNs of declining wild apple trees in different years in the Qiaolakesai Valley

Table S5 Differences in soil physical-chemical variables in sampling plots of declining wild apple trees among different elevations or years in the Qiaolakesai Valley

Fig. 7 Significance of correlation coefficient of environmental factors with PC, DBP, and twig traits of all declining wild apple trees sampled in the Qiaolakesai Valley. SOC, soil organic carbon; TN, total nitrogen; TP, total phosphorus; TK, total potassium; AN, available nitrogen; AP, available phosphorus; AK, available potassium; EC, electrical conductivity; AAP, annual accumulative precipitation; MDT, annual mean difference between day and night temperatures; MAT, mean annual temperature.

Table 2 Correlation coefficients of the first two axes of non-metric multidimensional scaling (NMDS) ordination with the environmental factors and plant traits of declining wild apple trees in the Qiaolakesai Valley

Fig. S6 Non-metric multidimensional scaling (NMDS) ordination diagram of environmental factors and plant traits of declining wild apple trees in the Qiaolakesai Valley. Axis 1, the first axis of NMDS ordination; Axis 2, the second axis of NMDS ordination. TN, total nitrogen; TP, total phosphorus; TK, total potassium; AN, available nitrogen; AK, available potassium; EC, electrical conductivity; AAP, annual accumulative precipitation; MDT, annual mean difference between day and night temperatures; MAT, mean annual temperature.

Fig. 8 Structural equation model (with standardized regression weights) depicting relative effects of meteorological factors, soil physical-chemical variables, twig nutrient, and LA on the plant growth status of declining wild apple trees in the Qiaolakesai Valley. The total amount of variance (R²) explained for each endogenous variable (i.e., those with arrows pointing to them) is given on the top of the variable. Red and blue arrows indicate significant positive and negative relationships, respectively. Numbers adjacent to arrows are standardized path coefficients. The thickness of the arrows denotes the strength of these significant paths. Dotted arrows represent non-significant paths (P>0.05). ^**, P<0.01 level; ^***, P<0.001 level. The fit of the model to the data is satisfactory (P=0.657, root mean square error of approximation (RMSEA)=0.000, χ²=0.198, degree of freedom (df)=1, normed-fit index (NFI)=0.999, reporting fit index (RFI)=0.986, incremental fit index (IFI)=1.003, Tucker-Lewis index (TLI)=1.059, comparative fit index (CFI)=1.000, and Akaike information criterion (AIC)=52.198).


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