Abstract
To effectively address the issues of poor ventilation, light deficiency, increased pest and disease pressure, and declining fruit quality in closed-canopy walnut orchards, this study was conducted in a standard, densely planted ‘Xinwen 185’ walnut orchard. Three treatments were established: an unthinned control (CK), a 1-year thinning treatment (T1), and a 2-year thinning treatment (T2). All parameters were uniformly investigated during the 2023 growing season to analyze the effects of thinning on orchard population structure, microenvironment, leaf physiological characteristics, fruit quality, and yield. The results demonstrated that tree thinning significantly optimized the population structure: crown width expanded by 6.22–6.76 m, light transmittance increased to 27.74–33.64%, and orchard coverage decreased from 100% to 75.94–80.51%. The microenvironment was improved: inter-row temperature increased by 2.34–4.08 °C, light intensity increased by 5.38–25.29%, and relative humidity decreased by 2.15–3.30%. Furthermore, leaf physiological functions were activated: in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively; the leaf carbon-to-nitrogen ratio increased by 18.67%; the net photosynthetic rate (Pn) during fruit expansion increased by 34.21–46.10%; and the intercellular CO2 concentration (Ci) decreased by 10.18–10.31%. Fruit quality and yield were synergistically enhanced: single fruit weight increased by 23.39~37.94%, and kernel weight increased by 26.79–41.13%. The total sugar content in inner-canopy fruits increased by 16.50–16.67%, while the protein and fat content in outer-canopy fruits increased by 0.69–12.50% and 0.60–2.18%, respectively. Yield exhibited a “short-term adjustment and long-term gain” pattern: the T2 treatment (after 2 years of thinning) achieved a yield of 5.26 t·ha−1, which was 20.38% higher than the CK. The rates of diseased fruit and empty shells decreased by 65.71% and 93.22%, respectively, and the premium fruit rate reached 90.60%. This study confirms that tree thinning is an effective measure for improving the growing environment and enhancing overall productivity in closed-canopy walnut orchards, providing a scientific basis for sustainable orchard management and increased orchard profitability.
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Claims 20
Claim · model-written summary
Tree thinning expanded crown width by 6.22-6.76 m.
Verbatim
t1“Walnut Orchards”
e0“crown width expanded by 6.22–6.76 m”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Tree thinning increased light transmittance to 27.74-33.64%.
Verbatim
t1“Walnut Orchards”
e0“light transmittance increased to 27.74–33.64%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Tree thinning reduced orchard coverage from 100% to 75.94-80.51%.
Verbatim
t1“Walnut Orchards”
e0“orchard coverage decreased from 100% to 75.94–80.51%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Tree thinning raised inter-row temperature by 2.34-4.08 degrees C.
Verbatim
t1“Walnut Orchards”
e0“inter-row temperature increased by 2.34–4.08 °C”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Tree thinning raised light intensity by 5.38-25.29%.
Verbatim
t1“Walnut Orchards”
e0“light intensity increased by 5.38–25.29%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Tree thinning lowered relative humidity by 2.15-3.30%.
Verbatim
t1“Walnut Orchards”
e0“relative humidity decreased by 2.15–3.30%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
In the T2 treatment, chlorophyll content in outer-canopy leaves increased by 15.23% at the kernel-hardening stage.
Verbatim
t1“Walnut Orchards”
e0“in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively”
e1“an unthinned control (CK)”
Claim · model-written summary
In the T2 treatment, chlorophyll content in outer-canopy leaves increased by 12.45% at the maturity stage.
Verbatim
t1“Walnut Orchards”
e0“in the T2 treatment, the chlorophyll content in outer-canopy leaves increased by 15.23% and 12.45% at the kernel-hardening and maturity stages, respectively”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased the leaf carbon-to-nitrogen ratio by 18.67%.
Verbatim
t1“Walnut Orchards”
e0“the leaf carbon-to-nitrogen ratio increased by 18.67%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased net photosynthetic rate during fruit expansion by 34.21-46.10%.
Verbatim
t1“Walnut Orchards”
e0“the net photosynthetic rate (Pn) during fruit expansion increased by 34.21–46.10%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning decreased intercellular CO2 concentration by 10.18-10.31%.
Verbatim
t1“Walnut Orchards”
e0“the intercellular CO2 concentration (Ci) decreased by 10.18–10.31%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased single fruit weight by 23.39-37.94%.
Verbatim
t1“Walnut Orchards”
e0“single fruit weight increased by 23.39~37.94%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased kernel weight by 26.79-41.13%.
Verbatim
t1“Walnut Orchards”
e0“kernel weight increased by 26.79–41.13%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased total sugar content in inner-canopy fruits by 16.50-16.67%.
Verbatim
t1“Walnut Orchards”
e0“The total sugar content in inner-canopy fruits increased by 16.50–16.67%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Thinning increased protein and fat content in outer-canopy fruits by 0.69-12.50% and 0.60-2.18%, respectively.
Verbatim
t1“Walnut Orchards”
e0“the protein and fat content in outer-canopy fruits increased by 0.69–12.50% and 0.60–2.18%, respectively”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
After 2 years of thinning (T2) yield reached 5.26 t/ha, 20.38% higher than the control.
Verbatim
t1“Walnut Orchards”
e0“the T2 treatment (after 2 years of thinning) achieved a yield of 5.26 t·ha−1, which was 20.38% higher than the CK”
Claim · model-written summary
Yield followed a short-term adjustment and long-term gain pattern under thinning.
Verbatim
t1“Walnut Orchards”
e0“Yield exhibited a “short-term adjustment and long-term gain” pattern”
Claim · model-written summary
Thinning lowered the rates of diseased fruit and empty shells by 65.71% and 93.22%, respectively.
Verbatim
t1“Walnut Orchards”
e0“The rates of diseased fruit and empty shells decreased by 65.71% and 93.22%, respectively”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
Under thinning the premium fruit rate reached 90.60%.
- Taxon
- Walnutt1
- Treatment
- Tree Thinningt0
- Outcome
- premium fruit ratee0
- Value
- 90.60%e0
- Comparator
- an unthinned control (CK)e1
Not reportedDirection
Verbatim
t1“Walnut Orchards”
e0“the premium fruit rate reached 90.60%”
t0“Tree Thinning”
e1“an unthinned control (CK)”
Claim · model-written summary
The authors conclude that tree thinning is an effective measure for improving the growing environment and productivity of closed-canopy walnut orchards.
Verbatim
e0“tree thinning is an effective measure for improving the growing environment and enhancing overall productivity in closed-canopy walnut orchards”
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