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Journal of Arid Land
Journal of Arid Land  2026, Vol. 18 Issue (11): 2008-2026    DOI: 10.1016/j.jaridl.2026.11.008    
Research article     
Root distribution and water competition mechanism between farmland shelterbelts and cotton under drip irrigation in an oasis of Xinjiang, China
JIANG Yan1,2, AN Dongliang3,*(), XUE Bing1,2, YAO Yandi4, HOU Zhen'an1,2
1 Agricultural College, Shihezi University, Shihezi 832003, China
2 The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Corps, Shihezi 832003, China
3 Shihezi Meteorological Bureau of Xinjiang, Shihezi 832003, China
4 Shihezi Academy of Agricultural Sciences, Shihezi 832003, China
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Abstract  

Farmland shelterbelts play a crucial role in protecting arable land in arid and semi-arid areas, but they may also compete for soil water with crops in agroforestry systems. Film-mulched drip irrigation in adjacent farmland substantially alters the water supply dynamics of shelterbelts, yet studies on the hydrological interactions between farmland shelterbelts and crops under this irrigation regime in the arid oasis areas along the desert margins of Xinjiang Uygur Autonomous Region, China remain limited. This study conducted an experiment in an oasis at the southern margin of the Gurbantunggut Desert in Xinjiang over the 2022-2024 growing seasons. We characterized the evapotranspiration (ET) patterns of the cotton field and adjacent Populus shelterbelt, quantitatively evaluated their interspecific water relationships, and examined fine root distribution to identify the zones and intensity of water competition. The results indicated that during the seedling and flowering-bolling stages, cotton field ET exceeded shelterbelt ET by 56.0%-66.1%; however, during the boll-opening stage, shelterbelt ET was 24.2% higher than cotton field ET. Within the 0.1H-0.5H into the cotton field from the shelterbelt-cotton field interface (where H is the mean tree height), Populus exhibited a competitive advantage in the 20-40 cm soil layer, with a competitiveness index of 0.083-0.146 (versus 0.039-0.051 for cotton), while competition was weakest in the 40-60 cm layer. At 0.1H, Populus root biomass density (RBD) and root length density (RLD) were 1.0-15.2 and 6.0-50.0 times those of cotton, respectively; at 1.0H, cotton RBD accounted for 63.0%-93.5% of total root biomass; and no Populus roots or evidence of water competition were detected at 2.0H and 3.0H. Supplemental irrigation should be applied to cotton fields adjacent to shelterbelts to offset water loss from interspecific competition, particularly during the boll-opening stage. The findings provide a practical basis for optimizing agricultural water management in oasis-desert agroforestry systems under film-mulched drip irrigation and offer regional empirical evidence for global research on water competition in arid-zone agroforestry systems.

Key words： farmland shelterbelt      cotton field      film-mulched drip irrigation      evapotranspiration      interspecific water competition      root distribution      agroforestry systems     
Received: 18 November 2025      Published: 30 November 2026
Corresponding Authors: *AN Dongliang (E-mail: an_dongliang@163.com)
About author: Author contributions

Conceptualization: AN Dongliang, YAO Yandi; Data curation: JIANG Yan, XUE Bing; Formal analysis: JIANG Yan, AN Dongliang, YAO Yandi; Funding acquisition: JIANG Yan, AN Dongliang, YAO Yandi; Investigation: XUE Bing; Methodology: AN Dongliang, YAO Yandi; Project administration: AN Dongliang, YAO Yandi; Resources: JIANG Yan, YAO Yandi; Software: XUE Bing, HOU Zhen'an; Supervision: AN Dongliang, YAO Yandi, HOU Zhen'an; Validation: JIANG Yan, AN Dongliang, YAO Yandi; Visualization: JIANG Yan, XUE Bing; Writing - original draft: JIANG Yan; Writing - review & editing: JIANG Yan, AN Dongliang, YAO Yandi. All authors approved the manuscript.

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JIANG Yan
AN Dongliang
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HOU Zhen'an
Cite this article:

JIANG Yan, AN Dongliang, XUE Bing, YAO Yandi, HOU Zhen'an. Root distribution and water competition mechanism between farmland shelterbelts and cotton under drip irrigation in an oasis of Xinjiang, China. Journal of Arid Land, 2026, 18(11): 2008-2026.

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http://jal.xjegi.com/10.1016/j.jaridl.2026.11.008     OR     http://jal.xjegi.com/Y2026/V18/I11/2008

Fig. 1 Layout of measuring points in the shelterbelt and cotton field. P1, P5, and P10 indicate Populus trees selected at three distances (1.0, 5.0, and 10.0 m) from the shelterbelt-cotton field interface for evapotranspiration (ET) measurement of individual trees. H is the mean tree height.
Fig. 2 Diurnal variation of mean sap flux density (Fmean; a), annual variation of individual tree evapotranspiration (ETp; b), and diurnal variation of ET of shelterbelt (c)
Fig. 3 Variation in daily ET of cotton field (ETcd) at different distances from the shelterbelt on selected dates. Different lowercase letters indicate significant differences among distances (P<0.05). Error bar represents the standard error of the mean.
Fig. 4 Comparative analysis of ET of shelterbelt and cotton field. (a), daily ET dynamics from May to September; (b), total ET at four growth stages of cotton. ETpd, daily ET of shelterbelt. Gray shaded areas highlight the two periods when cotton field ET is greater than shelterbelt ET.
Scale Growth stage ET ratio at each distance class
0.1H 0.5H 1.0H 2.0H 3.0H
Unit area Seedling stage 0.07 0.09 0.12 0.17 0.16
Squaring stage 0.14 0.16 0.19 0.23 0.22
Flowering-bolling stage 0.15 0.15 0.19 0.21 0.20
Boll-opening stage 0.06 0.08 0.08 0.11 0.14
Actual area Seedling stage 0.78 1.03 1.14 1.21 1.25
Squaring stage 0.90 1.03 1.22 1.38 1.34
Flowering-bolling stage 0.94 1.05 1.39 1.97 1.95
Boll-opening stage 0.50 0.58 0.84 0.96 0.93
Table 1 Evapotranspiration (ET) ratios of cotton field to shelterbelt across cotton growth stages at different scales
Fig. 5 Variations in soil water content of the cotton field at different distances from the shelterbelt (0.1H, 0.5H, and 3.0H) and the shelterbelt across five soil depths (a) and cotton dry matter across three months (May, July, and August) at five distances from the shelterbelt (b). In Figure 5a, different lowercase letters indicate significant differences among measuring points (P<0.05). In Figure 5b, different lowercase letters indicate significant differences among months (P<0.05); different capital letters indicate significant differences among measuring points (P<0.05). Error bar represents the standard error of the mean.
Fig. 6 Niche width of Populus and cotton in the shelterbelt-cotton agroforestry system. Different capital letters indicate significant differences among measuring points (P<0.05); different lowercase letters indicate significant differences between Populus and cotton (P<0.05). Error bar represents the standard error of the mean.
Fig. 7 Competitiveness index of Populus and cotton. (a), horizontal variation; (b-d), vertical variation at 0.1H, 0.5H, and 1.0H. P-C indicates Populus relative to cotton; C-P indicates cotton relative to Populus. Different lowercase letters indicate significant differences between Populus and cotton (P<0.05). Error bars represent the standard error of the mean.
Fig. 8 Root biomass density (RBD; a-d) and root length density (RLD; e-h) of Populus and cotton fine roots at 0.1H, 0.5H, 1.0H, and 3.0H. P and C indicate Populus and cotton, respectively. Different lowercase letters indicate significant differences between Populus and cotton (P<0.05). Error bar represents the standard error of the mean.
Fig. 9 Correlation between RBD and soil water content. Data included 10 observations from the Populus shelterbelt and 10 observations (5 distances×2 replicates) from the adjacent cotton field.
Fig. 10 Vertical distribution of the proportion of RBD for Populus and cotton fine roots at different distances from the shelterbelt. (a), 0.1H; (b), 0.5H; (c), 1.0H; (d), 3.0H. Bars represent the proportions of RBD for each species relative to the total at each soil depth layer. Error bar represents the standard error of the mean.
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