分类： 生物学 >> 植物学 提交时间： 2018-01-22
摘要： Bamboo species—the only herbal trees—have unique structural and physiological characteristics that differ from those of other tree taxa. However, the role of night-time water use in bamboo is poorly understood and has rarely been investigated. We studied day- and night-time sap flow response to culm age and rhizome structure in three age levels (juvenile, mature, and senescent) of Phyllostachys pubescens growing in the Nankun Mountain Natural Reserve, South China. We found that sap flow density and whole-tree hydraulic conductance decreased with culm age. After cutting, day-time sap flow and night-time water recharge decreased obviously. In addition, night-time water recharge accounted for the largest proportion (up to 30%) of total daily transpiration in senescent normal bamboos. Therefore, our study indicates that the connected rhizome system and night-time water recharge played significant roles in water compensation during the day and at night in bamboos. Night-time water recharge is especially critical to senescent bamboos because of their weaker transpiration due to the lower whole-tree hydraulic conductance and those are more dependent on night-time water recharge for fulfilling their whole-day water consumption needs.
分类： 生物学 >> 植物学 提交时间： 2018-01-22
摘要： Thermal dissipation probes were used to measure xylem sap flux density for a Schima superba plantation growing in the urban area of Guangzhou city, South China. Stand transpiration was calculated by multiplying mean sap flux density by total sapwood area. The peak of sap flux density occurred later in wet season than in dry season. The maximum of daily sap flux density was the highest of 59 g m-2 s-1 in July and August, and the lowest of 28 g m-2 s-1 in December. During November 2007- October 2008 and during November 2008-October 2009, the stand transpiration was 263.2 and 291.6 mm, respectively. In the study periods, stand transpiration in wet season (from April to September) could account for about 58.5% and 53.8% of the annual transpiration, respectively. Heat energy absorbed by tree transpiration averaged 1.4×108 and 1.6×108 kJ per month in the Schima superba plantation with the area of 2885 m2, and temperature could be reduced by 4.3 and 4.7 oC s-1 for 10 m3 air.
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