Diverse Understory Vegetation Alleviates Nitrogen Competition with Crop Trees in Poplar Plantations
Abstract
:1. Introduction
- (1)
- How does the presence of understory vegetation affect the growth and N utilization of poplar trees?
- (2)
- Does an increase in UVSR alleviate N competition with poplar trees and maintain poplar growth?
2. Materials and Methods
2.1. Study Site Description and Experimental Design
2.2. Tree Growth Monitoring
2.3. Poplar Leaf, Understory Vegetation, and Soil Sampling and Preparation
2.4. Measurement of Poplar Leaf, Understory Vegetation, and Soil Variables
2.5. Statistical Analyses
3. Results
3.1. Impact of UVSR on Poplar Growth
3.2. Impact of UVSR on Poplar Foliar N and Chlorophyll Content and Enzyme Activity
3.3. Biomass and N Accumulation in Understory Vegetation
3.4. Linking δ15N of Plants and Soil Inorganic N Pool in Response to UVSR
4. Discussion
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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June | August | ||||||
---|---|---|---|---|---|---|---|
Soil Layer (0–5 cm) | Soil Layer (5–10 cm) | Soil Layer (10–20 cm) | Soil Layer (0–5 cm) | Soil Layer (5–10 cm) | Soil Layer (10–20 cm) | ||
NH4+-N content (mg kg−1) | UR | 2.23 ± 0.22 b | 1.39 ± 0.22 b | 1.06 ± 0.18 b | 2.05 ± 0.28 a | 2.01 ± 0.28 a | 1.79 ± 0.26 a |
RS | 4.34 ± 0.45 a | 4.60 ± 1.06 a | 2.73 ± 0.55 a | 2.46 ± 0.62 a | 2.89 ± 0.49 a | 1.47 ± 0.06 a | |
RD | 3.97 ± 1.04 a | 3.81 ± 0.65 a | 1.77 ± 0.30 b | 2.43 ± 0.40 a | 2.11 ± 0.43 a | 1.61 ± 0.12 a | |
NO3−-N content (mg kg−1) | UR | 26.17 ± 5.67 a | 24.73 ± 1.86 a | 15.35 ± 3.28 a | 11.63 ± 2.49 a | 12.32 ± 1.95 a | 6.88 ± 0.81 a |
RS | 26.28 ± 5.26 a | 10.15 ± 1.92 b | 8.01 ± 1.59 b | 9.78 ± 1.99 a | 12.16 ± 1.66 a | 4.62 ± 0.95 b | |
RD | 24.53 ± 4.44 a | 10.19 ± 1.40 b | 6.74 ± 1.92 b | 10.66 ± 0.67 a | 9.15 ± 1.14 a | 5.69 ± 0.34 ab | |
δ15N of NH4+-N (‰) | UR | 4.75 ± 0.01 a | 4.75 ± 0.03 a | 6.78 ± 0.05 a | 2.62 ± 0.07 a | 2.65 ± 0.02 a | 3.25 ± 0.01 a |
RS | 4.52 ± 0.28 ab | 4.44 ± 0.26 b | 6.56 ± 0.10 a | 2.48 ± 0.15 a | 2.47 ± 0.14 a | 3.62 ± 0.09 a | |
RD | 4.26 ± 0.07 b | 4.30 ± 0.03 b | 6.53 ± 0.31 a | 2.57 ± 0.21 a | 2.62 ± 0.03 a | 3.48 ± 0.24 a | |
δ15N of NO3−-N (‰) | UR | 2.71 ± 0.07 a | 2.85 ± 0.02 a | 3.69 ± 0.09 a | −3.33 ± 0.26 a | −3.46 ± 0.17 a | 0.54 ± 0.02 b |
RS | 2.48 ± 0.03 b | 2.79 ± 0.05 a | 3.66 ± 0.18 a | −3.58 ± 0.10 a | −3.65 ± 0.03 a | 0.63 ± 0.01 a | |
RD | 2.67 ± 0.08 a | 2.44 ± 0.17 b | 3.65 ± 0.19 a | −3.67 ± 0.07 a | −3.68 ± 0.09 a | 0.64 ± 0.01 a |
Variable Y | Standardized Coefficient | r2 | p Value | ||||||
---|---|---|---|---|---|---|---|---|---|
x1 | x2 | x3 | x4 | x5 | x6 | ||||
June | δ15N of poplar leaf under UR treatment | - | - | 0.38 | - | - | 0.62 | 0.99 | 0.02 |
δ15N of poplar leaf under RS treatment | - | - | 0.49 | - | - | 0.51 | 0.99 | 0.02 | |
δ15N of poplar leaf under RD treatment | - | - | 0.59 | - | - | 0.41 | 0.99 | 0.00 | |
δ15N of barnyard grass under RS treatment | - | - | 0.34 | - | - | 0.67 | 0.99 | 0.01 | |
δ15N of barnyard grass under RD treatment | - | - | 0.33 | - | - | 0.67 | 0.99 | 0.00 | |
August | δ15N of poplar leaf under UR treatment | 0.04 | - | - | - | - | 0.97 | 0.99 | 0.02 |
δ15N of poplar leaf under RS treatment | - | - | 1.45 | - | 0.45 | - | 0.99 | 0.02 | |
δ15N of poplar leaf under RD treatment | 1.13 | - | - | - | 0.13 | - | 0.99 | 0.02 | |
δ15N of barnyard grass under RS treatment | - | - | - | - | 0.13 | 1.13 | 0.99 | 0.01 | |
δ15N of barnyard grass under RD treatment | 0.02 | - | - | - | - | 0.98 | 0.99 | 0.00 |
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Zhang, J.; Qin, G.; Zhai, Z.; Zhou, S.; Tang, L.; Tian, Y. Diverse Understory Vegetation Alleviates Nitrogen Competition with Crop Trees in Poplar Plantations. Forests 2021, 12, 705. https://doi.org/10.3390/f12060705
Zhang J, Qin G, Zhai Z, Zhou S, Tang L, Tian Y. Diverse Understory Vegetation Alleviates Nitrogen Competition with Crop Trees in Poplar Plantations. Forests. 2021; 12(6):705. https://doi.org/10.3390/f12060705
Chicago/Turabian StyleZhang, Jiayu, Guangzhen Qin, Zheng Zhai, Shichao Zhou, Luozhong Tang, and Ye Tian. 2021. "Diverse Understory Vegetation Alleviates Nitrogen Competition with Crop Trees in Poplar Plantations" Forests 12, no. 6: 705. https://doi.org/10.3390/f12060705