Werk K S, Oren R, Schulze E -D, Zimmermann R, Meyer J
Lehrstuhl für Pflanzenökologie, Universität Bayreuth, Postfach 101251, D-8580, Bayreuth, Federal Republic of Germany.
Oecologia. 1988 Sep;76(4):519-524. doi: 10.1007/BF00397863.
The water relations of Picea abies in a healthy stand with green trees only and a declining stand with trees showing different stages of needle yellowing were investigated in northern Bavaria. The present study is based on observations of trees differing in their nutritional status but apparently green on both sites in order to identify changes in the response pattern which might be caused by atmospheric concentrations of air pollutants and could lead to the phenomenon of decline. Transpiration was measured as water flow through the hydroactive xylem using an equilibrium mass-flow measurement system. Total tree transpiration was monitored diurnally, from July 1985 until October 1985 at both sites. The relationship between transpiration and meteorological measurements indicated that transpiration was a linear function of the vapor pressure deficit. No differences in transpiration of green trees were observed between the two sites. Canopy transpiration was 57%-68% of total throughfall and 41%-54% of total rainfall. Due to this positive water balance, soil water potential at 10 and 20 cm depths remained close to-0.02 MPa (max.-0.09 MPa) for most of the summer. Soil water potential was correlated with the difference between the weekly precipitation and transpiration. No differences in the water relations of apparently healthy trees in the two P. abies stands were observed. It is concluded that differences between green trees at the two sites in terms of nutrient relations or growth rate cannot be explained by changes in whole-tree transpiration or soil water status.
在德国巴伐利亚州北部，对仅生长着绿色树木的健康云杉林分以及树木呈现出不同程度针叶黄化的衰退林分中的欧洲云杉水分关系进行了研究。本研究基于对营养状况不同但在两个地点看起来均为绿色的树木的观察，目的是确定可能由大气污染物浓度引起且可能导致衰退现象的响应模式变化。使用平衡质量流测量系统，通过水分活跃木质部中的水流来测量蒸腾作用。1985年7月至10月期间，在两个地点对树木的总蒸腾作用进行了每日监测。蒸腾作用与气象测量之间的关系表明，蒸腾作用是水汽压差的线性函数。在两个地点未观察到绿色树木蒸腾作用的差异。林冠蒸腾量占总穿透雨量的57% - 68%，占总降雨量的41% - 54%。由于这种正水平衡，在夏季的大部分时间里，10厘米和20厘米深度处的土壤水势保持在接近 - 0.02兆帕（最大值 - 0.09兆帕）。土壤水势与每周降水量和蒸腾量之间的差值相关。在两个欧洲云杉林分中，未观察到明显健康树木的水分关系存在差异。得出的结论是，两个地点绿色树木在营养关系或生长速率方面的差异无法通过整树蒸腾作用或土壤水分状况的变化来解释。
