不同灌溉方式对樟子松生长、光合特性及土壤水分运移的影响

【目的】研究滴灌、漫灌和对照3种处理方式下樟子松(Pinus sylvestris var. mongolica)生长状况和土壤水分运移规律,探讨其生长、光合、蒸腾特性和水分运移对不同灌溉技术的响应,为在干旱、半干旱地区高效栽培樟子松提供参考。【方法】以内蒙古大青山国家级自然保护区的樟子松林为研究对象,基于单因素方差分析比较不同灌溉方式下樟子松的生长(地径、树高、冠幅、抽穗长和生物量)与光合特性[光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、胞间CO₂浓度(C_i)和水分利用效率(E_WUE)];采用土壤剖面观测法比较不同灌溉方式和灌溉时间下土壤水分垂直和水平运移的变化规律,并利用经验模型对土壤水分运移轮廓进行模拟。【结果】①滴灌处理下樟子松的地径、树高、冠幅、抽穗长和生物量分别比漫灌方式下高1.5 cm、0.5 m、10.0 cm、5.9 cm和11.5 kg,分别比对照高3.4 cm、0.9 m、60.0 cm、7.2 cm和2.5 kg;②滴灌处理下樟子松的光合速率、蒸腾速率、气孔导度和胞间CO₂浓度显著高于漫灌和对照(P < 0.05),各种灌溉方式下的上述指标大小具体表现为滴灌>漫灌>对照;水分利用效率大小表现为对照>滴灌>漫灌,表明樟子松可在较低的土壤含水量条件下生长;③在灌溉2、4和6 h后,樟子松林地滴灌比漫灌处理下土壤湿润锋的垂直运移距离和停灌后最终垂直运移距离深,两种灌溉方式下3种不同灌溉时长的土壤湿润锋的最大水平运移距离都出现在0~20 cm土层,然而停灌后的垂直运移距离以滴灌>漫灌;④利用经验模型对土壤湿润体轮廓进行模拟,设定:为垂直方向上任意位置处土壤水分水平运移距离(i=1,2,3,4);L_MR为土壤水分水平最大运移距离;R_MH为垂直方向上任意位置处土壤水分垂直运移相对距离;a_i为模型参数。则滴灌和漫灌的最优模型分别为多项式模型(M_R1)和Baldwin模型(M_R4), $M_{mathrm{R} 1}=L_{mathrm{MR}}left[a_{1}left(R_{mathrm{MH}}-1right)+a_{2}left(R_{mathrm{MH}}^{2}-1right)+a_{3}left(R_{mathrm{MH}}{ }^{3}-1right)+a_{4}left(R_{mathrm{MH}}^{4}-1right)right]$; $M_{mathrm{R} 4}=a_{1}+left[left(R_{mathrm{MH}}-1right) /left(R_{mathrm{MH}}+1right)right]+a_{2}left(R_{mathrm{MH}}-1right)$。【结论】在北方干旱区,滴灌区樟子松的生长和光合特性明显优于漫灌;在持续灌溉2、4和6 h后,滴灌试验区60 cm土层以上的土壤湿润锋在最终水平运移距离上均大于漫灌区。将滴灌技术应用于樟子松林木培育,有利于根系吸收水分和促进树木生长,且樟子松的光合特性受水分利用效率影响,合理的灌溉可改善林木的生长机制。

Effects of different irrigation methods on growth,photosynthetic characteristics and soil water transport of Mongolian pine (Pinus sylvestris var. mongolica)

【Objective】 The growth and soil water transport of Mongolian pine (Pinus sylvestris var. mongolica) were studied under three different drip treatments (drip irrigation, flood irrigation and control), and the responses of growth, photosynthesis, transpiration and water transport to the irrigation methods were discussed to provide a reference for efficient cultivation of P. sylvestris var. mongolica in arid and semi-arid areas. 【Method】 With P. sylvestris var. mongolica of the Daqingshan National Nature Reserve in Inner Mongolia as the research object, the growth (ground diameter, tree height, crown width, head sprouting length and biomass) and photosynthetic characteristics [photosynthetic rate (P_n), transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), and water use efficiency (E_WUE)] of P. sylvestris var. mongolica were compared under different irrigation methods based on One-way ANOVA; soil profile observation was used to compare the migration distance of soil water in horizontal and vertical directions under different irrigation methods and durations. 【Result】 (1) The ground diameter, tree height, crown width, head sprouting length and biomass parameters of P. sylvestris var. mongolica in the drip irrigation were 1.5 cm, 0.5 m, 10 cm, 5.9 cm and 11.5 kg higher, respectively, than those in the flood irrigation, and 3.4 cm, 0.9 m, 60.0 cm, 7.2 cm and 2.5 kg higher than those in the control, respectively. (2) The P_n, T_r, G_s and C_i values of samples under the drip irrigation were significantly higher than those under the flood irrigation and control (P < 0.05), and decreased in the following order: drip irrigation > flood irrigation > control. However, E_WUE decreased in the following order: control > drip irrigation > flood irrigation, indicating P. sylvestris var. mongolica had the ability to tolerate drought under low soil water conditions. (3) After 2, 4 and 6 h irrigation, the vertical migration distance of soil moisture front and the final vertical migration distance after stopping the irrigation were deeper in the drip irrigation than in the flood irrigation. Under the two irrigation methods, the maximum horizontal migration distance of soil moisture front for the three different irrigation times in each soil layer was observed to be in the range of 0-20 cm. However, the vertical migration distance after stopping the irrigation decreased in the following order: drip irrigation > flood irrigation. (4) A few empirical models were used to simulate the profile of soil wetting body and the results confirmed that the optimal models for the drip irrigation and the flood irrigation were Polynomial (Eq.1) $M_{mathrm{R} 1}=L_{mathrm{MR}}left[a_{1}left(R_{mathrm{MH}}-1right)+a_{2}left(R_{mathrm{MH}}^{2}-1right)+a_{3}left(R_{mathrm{MH}}{ }^{3}-1right)+a_{4}left(R_{mathrm{MH}}^{4}-1right)right]$ and Baldwin and Peterson (Eq.4) $M_{mathrm{R} 4}=a_{1}+left[left(R_{mathrm{MH}}-1right) /left(R_{mathrm{MH}}+1right)right]+a_{2}left(R_{mathrm{MH}}-1right)$, respectively. Among them, is the horizontal movement distance of soil water at any position in the vertical direction; L_MR is the maximum horizontal movement distance of soil water; R_MH is the vertical movement of soil water at any position in the vertical direction relative distance; a_i is the model parameter (i=1, 2, 3, 4).【Conclusion】 The drip irrigation was obviously better than the flood irrigation based on each evaluation index in the arid areas of the north China. After 2, 4 and 6 h irrigation, the final horizontal migration distance of soil water front above 60 cm soil layer in the drip irrigation was larger than that in the flood irrigation. The drip irrigation was beneficial to the root water absorption and the growth of P. sylvestris var. mongolica. The E_WUE affects the photosynthetic characteristics of P. sylvestris var. mongolica and reasonable irrigation can improve the growth mechanisms.