Schulze E -D, Čermák J, Matyssek M, Penka M, Zimmermann R, Vasícek F, Gries W, Kučera J
Lehrstuhl Pflanzenökologie der Universität Bayreuth, Postfach 3008, D-8580, Bayreuth, Federal Republic of Germany.
Institute of Forest Ecology, Brno University of Agriculture, 64400, Brno-Soběšice, ČSSR.
Oecologia. 1985 Jul;66(4):475-483. doi: 10.1007/BF00379337.
Leaf gas exchange, transpiration, water potential and xylem water flow measurements were used in order to investigate the daily water balance of intact, naturally growing, adult Larix and Picea trees without major injury. The total daily water use of the tree was very similar when measured as xylem water flow at breast height or at the trunk top below the shade branches, or as canopy transpiration by a porometer or gas exchange chamber at different crown positions. The average canopy transpiration is about 12% lower than the transpiration of a single twig in the sun crown of Larix and Picea. Despite the similarity in daily total water flows there are larger differences in the actual daily course. Transpiration started 2 to 3 h earlier than the xylem water flow and decreased at noon before the maximum xylem water flow was reached, and stopped in the evening 2 to 3 h earlier than the water flow though the stem. The daily course of the xylem water flow was very similar at the trunk base and top below the lowest branches with shade needles. The difference in water efflux from the crown via transpiration and the water influx from the trunk is caused by the use of stored water. The specific capacitance of the crown wood was estimated to be 4.7 x 10 and 6.3 x 10 kg kg Pa and the total amount of available water storage was 17.8 and 8.7 kg, which is 24% and 14% of the total daily transpiration in Larix and Picea respectively. Very little water was used from the main tree trunk. With increasing transpiration and use of stored water from wood in the crown, the water potential in the foliage decreases. Plant water status recovers with the decrease of transpiration and the refilling of the water storage sites. The liquid flow conductance in the trunk was 0.45 x 10 and 0.36 x 10 mol ms Pa in Larix and Picea respectively. The role of stomata and their control by environmental and internal plant factors is discussed.
为了研究未受重大损伤的完整、自然生长的成年落叶松和云杉树的每日水分平衡，我们进行了叶片气体交换、蒸腾作用、水势和木质部水流测量。当以胸高处或树干顶部低于遮荫枝条处的木质部水流来衡量，或以不同树冠位置的气孔计或气体交换室测量的冠层蒸腾作用来衡量时，树木的每日总用水量非常相似。落叶松和云杉平均冠层蒸腾作用比阳树冠层单个小枝的蒸腾作用低约12%。尽管每日总水流相似，但实际的每日变化过程存在较大差异。蒸腾作用比木质部水流早2至3小时开始，在中午达到最大木质部水流之前就开始下降，并在傍晚比通过茎干的水流早2至3小时停止。在树干基部和最低枝条以下有遮荫针叶的顶部，木质部水流的每日变化过程非常相似。通过蒸腾作用从树冠流出的水分与从树干流入的水分之间的差异是由储存水的使用造成的。估计冠层木材的比电容分别为4.7×10和6.3×10千克·千克⁻¹·帕⁻¹，可用储水量分别为17.8千克和8.7千克，分别占落叶松和云杉每日总蒸腾量的24%和14%。树干主体使用的水分很少。随着蒸腾作用的增加和冠层木材中储存水的使用，叶片中的水势降低。随着蒸腾作用的降低和储水部位的重新补水，植物水分状况得以恢复。落叶松和云杉树干中的液流传导率分别为0.45×10和0.36×10摩尔·米⁻¹·秒⁻¹·帕⁻¹。本文还讨论了气孔的作用及其受环境和植物内部因素的控制。
