Pérez-Salicrup D R, Barker M G
Harvard Forest, Harvard University, P.O. Box 68, Petersham, MA 01366-0068, USA e-mail:
Department of Forestry, MacRobert Building, University of Aberdeen, Aberdeen AB24 5UA, UK, , , , , , GB.
Oecologia. 2000 Sep;124(4):469-475. doi: 10.1007/PL00008872.
Lianas, or woody climbing plants, are a major constituent of seasonally dry tropical forests, and are thought to impact negatively their host trees. In this study we evaluated whether liana presence was associated with reduced leaf water potentials and growth in adult Senna multijuga trees during the dry season in a lowland Bolivian forest. We used leaf water potentials in trees as a first approach to assess trees' water status, under the assumption that leaf water potentials become more negative when water losses (via transpiration) exceed gains (by uptake). We measured relative growth in girth at 1.5 m height (gbh) to quantify tree growth. At the beginning of the 1996 dry season (early June), we selected 20 S. multijuga trees 10-20 cm dbh, and measured their gbh. We also recorded pre-dawn and mid-day leaf water potentials in these trees. In ten experimental trees all lianas were then cut, while the remaining trees were used as controls. Pre-dawn and mid-day water potentials were re-measured 1 day after liana-cutting, and then every week in all trees for 1 month and then at 3 and 5 months, until the beginning of the next rainy season (November); gbh was measured again in July 1997 to estimate relative growth rate. Liana removal was associated with less negative pre-dawn (-0.3 vs -0.4 MPa) and mid-day (-0.5 vs -0.7 MPa) water potentials in trees during the dry season. This difference appeared as early as 1 day after cutting, and disappeared once the rainy season began. Liana-cut trees grew more (0.4 mm/mm year) than liana-uncut trees (0.2 mm/mm year). These findings suggest that lianas may interfere with water availability to these trees during the dry season, and may also hinder tree growth.
藤本植物，即木质攀缘植物，是季节性干燥热带森林的主要组成部分，被认为会对其寄主树木产生负面影响。在本研究中，我们评估了在玻利维亚低地森林的旱季，藤本植物的存在是否与成年多花番泻树的叶片水势降低和生长减缓有关。我们将树木的叶片水势作为评估树木水分状况的首要方法，其假设依据是当水分损失（通过蒸腾作用）超过水分获取（通过吸收）时，叶片水势会变得更负。我们测量了树木1.5米高度处的周长相对生长量（胸径生长量，gbh）以量化树木生长。在1996年旱季开始时（6月初），我们挑选了20棵胸径为10 - 20厘米的多花番泻树，并测量了它们的胸径生长量。我们还记录了这些树木的黎明前和正午时的叶片水势。然后，在十棵实验树上砍伐了所有藤本植物，其余树木作为对照。在砍伐藤本植物1天后重新测量黎明前和正午时的水势，然后在所有树木中每周测量一次，持续1个月，之后在3个月和5个月时测量，直到下一个雨季开始（11月）；1997年7月再次测量胸径生长量以估计相对生长速率。在旱季，去除藤本植物与树木黎明前（-0.3 vs -0.4兆帕）和正午时（-0.5 vs -0.7兆帕）水势负值减小有关。这种差异在砍伐后1天就出现了，并且在雨季开始后消失。砍伐藤本植物的树木比未砍伐藤本植物的树木生长得更多（每年0.4毫米/毫米）（每年0.2毫米/毫米）。这些发现表明，藤本植物可能在旱季干扰这些树木的水分供应，并且也可能阻碍树木生长。
