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Journal of Arid Land  2021, Vol. 13 Issue (7): 730-743    DOI: 10.1007/s40333-021-0010-8
Research article     
Effects of water and nitrogen on growth and relative competitive ability of introduced versus native C4 grass species in the semi-arid Loess Plateau of China
DING Wenli1, XU Weizhou2, GAO Zhijuan1, XU Bingcheng1,3,*()
1State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China
2College of Life Science, Yulin University, Yulin 719000, China
3Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling 712100, China
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Abstract  

Switchgrass is an introduced C4 grass in the semi-arid Loess Plateau of China, but there is a lack of information to assess its ecological invasive risk. In this study, Old World bluestems (native C4 grass) and switchgrass were sowed at five mixture ratios (8:0, 6:2, 4:4, 2:6 and 0:8) under two soil water levels (80% field capacity (FC) and 40% FC) and two nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) in a pot experiment in 2012. Biomass, root morphological traits and relative competitive abilities of these two species were analyzed. Results showed that biomass of both species was significantly greater under 80% FC or N fertilization, and switchgrass had a relatively larger root:shoot ratio (RSR). Total root length (TRL) and root surface area (RSA) of switchgrass were significantly higher under 80% FC irrespective of N treatment, while those of Old World bluestems were only significantly higher under N fertilization. N had no significant effect on TRL and RSA of switchgrass, while RSA of Old World bluestems significantly increased under 80% FC and N fertilization. Under 40% FC and N0-unfertilized treatment, the aggressivity of Old World bluestems was larger than zero at 2:6 and 4:4 mixture ratios of two species, whereas it was close to zero at 6:2 mixture ratio. Root competitive ability of switchgrass significantly increased under 80% FC or N fertilization. The aggressivity of Old World bluestems was negative at 6:2 mixture ratio under 80% FC and N fertilization, while it was positive at 2:6 mixture ratio. Switchgrass may become more aggressive when N deposition or rainfall increases, while a proper mixture ratio with appropriate water and N management could help with grassland management in the semi-arid Loess Plateau.



Key wordsaggressivity      nitrogen deposition      relative competitive ability      root trait      water stress     
Received: 04 January 2021      Published: 10 July 2021
Corresponding Authors: XU Bingcheng     E-mail: Bcxu@ms.iswc.ac.cn
About author: *XU Bingcheng (E-mail: Bcxu@ms.iswc.ac.cn)
Cite this article:

DING Wenli, XU Weizhou, GAO Zhijuan, XU Bingcheng. Effects of water and nitrogen on growth and relative competitive ability of introduced versus native C4 grass species in the semi-arid Loess Plateau of China. Journal of Arid Land, 2021, 13(7): 730-743.

URL:

http://jal.xjegi.com/10.1007/s40333-021-0010-8     OR     http://jal.xjegi.com/Y2021/V13/I7/730

Fig. 1 Schematic diagram of the experimental design. Open and filled circles represent Old World bluestems and switchgrass, respectively.
Index Species Water (W) Nitrogen (N) Mixture ratio (MR) W×N W×MR N×MR W×N×MR
Shoot biomass B <0.001 <0.001 <0.001 <0.001 0.422 0.001 0.776
P <0.001 <0.001 <0.001 <0.001 0.257 <0.001 0.402
B+P <0.001 <0.001 <0.001 <0.001 0.031 <0.001 0.492
Root biomass B 0.001 <0.001 <0.001 0.007 0.218 <0.001 0.782
P 0.003 <0.001 <0.001 0.045 0.176 0.356 0.285
B+P <0.001 <0.001 <0.001 0.002 0.291 <0.001 0.477
Total biomass B <0.001 <0.001 <0.001 0.470 0.914 <0.001 0.264
P <0.001 <0.001 <0.001 0.386 0.529 0.321 0.744
B+P <0.001 <0.001 0.160 0.870 0.434 0.691 0.724
RSR B <0.001 <0.001 <0.001 <0.001 0.670 <0.001 0.588
P <0.001 <0.001 <0.001 <0.001 0.346 <0.001 0.660
B+P <0.001 <0.001 <0.001 <0.001 0.378 <0.001 0.673
WUE B+P <0.001 <0.001 <0.001 0.020 0.646 0.727 0.863
Table 1 Analysis of variance of the effects of soil water, nitrogen, mixture ratio and their interactions on shoot, root and total biomass, root:shoot ratio (RSR) and water use efficiency (WUE) of Old World bluestems (B) and switchgrass (P)
Fig. 2 Shoot (a-f) and root biomass (g-l) of Old World bluestems (Bothriochloa ischaemum) and switchgrass (Panicum virgatum) under different soil water levels (40% FC and 80% FC), nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) and mixture ratios of two species. Bars are standard errors. Different uppercase letters indicate significant differences between two soil water levels within each mixture ratio and N treatment, while different lowercase letters indicate significant differences among different mixture ratios within each soil water level and N treatment. * indicates significant differences between two N treatments within each mixture ratio and soil water level (based on Tukey's post hoc analysis, P<0.05 level). B8P0, B6P2, B4P4, B2P6 and B0P8 indicate 8:0, 6:2, 4:4, 2:6 and 0:8 mixture ratios of Old World bluestems to switchgrass, respectively. The abbreviations are the same as in Figures 3-6.
Fig. 3 Total biomass (a-f) and root:shoot ratio (g-l) of Old World bluestems (Bothriochloa ischaemum) and switchgrass (Panicum virgatum) under different soil water levels (40% FC and 80% FC), nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) and mixture ratios. Bars are standard errors.
Source of variation df Total root length Root surface area Root average diameter
B P B P B P
Water (W) 1 <0.001 0.036 <0.001 0.009 0.263 0.001
Nitrogen (N) 1 <0.001 0.012 0.232 0.073 <0.001 <0.001
Mixture ratio (MR) 3 <0.001 0.060 <0.001 0.022 0.313 0.030
W×N 1 <0.001 0.294 <0.001 0.271 0.014 0.958
W×MR 3 0.142 0.160 0.212 0.140 0.020 0.057
N×MR 3 0.531 0.109 0.507 0.091 0.667 0.519
W×N×MR 3 0.775 0.203 0.742 0.191 0.070 0.847
Table 2 Analysis of variance of the effects of soil water, nitrogen, mixture ratio and their interactions on total root length, root surface area and root average diameter of Old World bluestems (B) and switchgrass (P)
Fig. 4 Total root length (a-d) and root surface area (e-h) of Old World bluestems (Bothriochloa ischaemum) and switchgrass (Panicum virgatum) under different soil water levels (40% FC and 80% FC), nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) and mixture ratios. Bars are standard errors.
Fig. 5 Root average diameter (RAD) of Old World bluestems (Bothriochloa ischaemum, a and b) and switchgrass (Panicum virgatum, c and d) under different soil water levels (40% FC and 80% FC), nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) and mixture ratios. Bars are standard errors.
Source of variation df Aggressivity (A) Relative yield total (RYT)
Shoot Root Total biomass Shoot Root Total biomass
Water (W) 1 0.002 0.543 <0.001 <0.001 0.035 <0.001
Nitrogen (N) 1 0.019 <0.001 <0.001 <0.001 <0.001 <0.001
Mixture ratio (MR) 2 <0.001 <0.001 <0.001 <0.001 0.398 0.104
W×N 1 0.056 <0.001 0.002 <0.001 0.414 0.414
W×M 2 0.045 0.290 0.080 0.099 0.275 0.275
N×M 2 <0.001 <0.001 0.142 0.133 0.264 0.264
W×N×MR 2 0.007 0.032 0.059 0.557 0.804 0.804
Table 3 Analysis of variance for the effects of soil water, nitrogen, mixture ratio and their interactions on the aggressivity and relative yield total
Treatment Mixture ratio Shoot Root Total biomass
N0-unfertilized+80% FC B6P2 -0.23±0.12aA* -0.14±0.02aA* -0.17±0.01aA*
B4P4 -0.26±0.25abA* 0.32±0.01b* -0.03±0.25aA
B2P6 0.36±0.06bA* 1.07±0.30c 0.48±0.01bA*
N1-fertilized+80% FC B6P2 -0.79±0.20a* -0.93±0.17aA* -1.25±0.02aA*
B4P4 1.16±0.22bB* -0.01±0.08bA* 0.01±0.16b
B2P6 4.45±1.47bB 1.06±0.43b 1.32±0.44cB*
N0-unfertilized+40% FC B6P2 0.06±0.07aB* 0.02±0.10aB* 0.05±0.05aB*
B4P4 0.34±0.18abB 0.13±0.04a 0.24±0.07aB
B2P6 1.08±0.25bB 1.11±0.34b* 1.10±0.21bB*
N1-fertilized+40% FC B6P2 -0.59±0.17a* -0.43±0.11aB* -0.51±0.11aB*
B4P4 0.30±0.27bA 0.25±0.04bB 0.28±0.14b
B2P6 0.56±0.11bA 0.49±0.17b* 0.53±0.11bA*
Table 4 Aggressivity values of shoot, root and total biomass of Old World bluestems (B) to switchgrass (P) under different water and nitrogen (N) treatments
Treatment Mixture ratio Shoot Root Total biomass
N0-unfertilized+80% FC B6P2 0.83±0.02bA* 0.72±0.06B* 0.79±0.03bB*
B4P4 0.89±0.05bA* 0.75±0.06B* 0.86±0.03bB*
B2P6 0.74±0.01aA* 0.82±0.06B* 0.70±0.02aB*
N1-fertilized+80% FC B6P2 2.31±0.12bB* 0.93±0.06B* 1.09±0.07aB*
B4P4 2.37±0.12bB* 0.96±0.06B* 1.17±0.08aB*
B2P6 2.22±0.12aB* 1.02±0.06B* 1.43±0.09bB*
N0-unfertilized+40% FC B6P2 0.91±0.03bB* 0.60±0.06A* 0.72±0.05bA*
B4P4 0.97±0.05bB* 0.63±0.06A* 0.78±0.06bA*
B2P6 0.81±0.02aB* 0.69±0.06A* 0.63±0.05aA*
N1-fertilized+40% FC B6P2 1.06±0.11bA* 0.81±0.06A* 0.81±0.06aA*
B4P4 1.11±0.11bA* 0.84±0.06A* 0.89±0.06aA*
B2P6 0.96±0.11aA* 0.90±0.06A* 1.15±0.05bA*
Table 5 Relative yield total of shoot, root and total biomass of Old World bluestem (B) and switchgrass (P) under different water and nitrogen (N) treatments
Fig. 6 Water use efficiency (WUE; a and b) of Old World bluestems (Bothriochloa ischaemum) and switchgrass (Panicum virgatum) together under different soil water levels (40% FC and 80% FC), nitrogen (N) treatments (0 and 100 mg N/kg dry soil, termed N0-unfertilized and N1-fertilized treatments, respectively) and mixture ratios. Bars are standard errors.
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