Abstract:

To analyze the influence of shading on the environment of tea plantation and leaf gas exchange characteristics of the tea, four different levels of shading (75%, 56%, 30% and 0%) were designed with different black shade cloths in summer. The results showed that shading improved the ecological environment of tea plantation effectively, the photo synthetically active radiation under 75%, 56% and 30% shading treatments decreased significantly compared with the control treatment. The daily average air temperature under 75%, 56% and 30% shading treatments were 1.7℃, 1.1℃ and 0.7℃ lower than in the control, and daily average soil surface temperature was 8.2℃, 5.7℃, 3.5℃ lower compared with that under the control. In addition, the daily average temperature of the 5 cm soil profile was 5.4℃, 3.4℃ and 2.3℃, lower than in the control, respectively. Humidity increased as temperature decreased. Relative humidity under 75%, 56% and 30% shading was 2.7%, 1.6%, 0.9% higher than in the control. Besides, significant difference was found between the 75% shading and the control treatment. The water content of one-bud-three-leaves was 21.8% higher and the average leaf area of the third mature leaf was 8.96 cm2 larger than those of control. Diurnal variation of net photosynthetic rate of tea was single-peak curve under 75% and 56% shading and bimodal curve under 30% and control. The total net photosynthetic rates of different treatments was in the order of 56%＞75%＞30%＞0%. At the same time, transpiration rate increased as the shading intensity become higher. Stomatal conductance showed a single peak curve under 56% and 75% shading, while it showed bimodal curve under 30% shading and control treatment.