Ekstam B
Department of Ecology, Limnology, Ecology Building, S-223 62, Lund, Sweden.
Oecologia. 1995 Dec;104(4):440-446. doi: 10.1007/BF00341341.
The influence of shading from older generations of dead culms (standing litter) on density, growth rate and development of size structure at the ramet level was investigated in a pure stand of Phragmites australis by experimental neutral shading of plots after removal of standing litter. Initial differences in height distribution between autumn and spring cohorts disappeared in the course of shoot growth. The Gini coefficients of shoot heights and estimated shoot weights indicated that the size structure of the shoots became more equal with increasing mean size in both shaded and unshaded plots. Relative growth rate for height (RHGR) and weight of individual shoots was negatively related to shoot size during the early and presumably storage-dependent growth period, suggesting a strong support for growth of smaller shoots. No etiolation was indicated by mean or maximum height in shaded and unshaded plots, or by the relationship between shoot height and weight. Mean shoot density was significantly lower in shaded than in unshaded plots in one of two shade treatment years. A regression model indicated a small but significant effect of shoot density on the approximately linear relationship between RHGR and the logarithm of height. The growth rate of small shoots was slightly larger at low than at high shoot density. Therefore, it is suggested that the shade from standing litter in P. australis stands can decrease shoot natality in the spring cohort, and thereby increase the support to fewer small shoots.
在去除直立凋落物后，通过对样地进行实验性中性遮荫，研究了老一代死亡茎秆（直立凋落物）的遮荫对芦苇纯林中分株水平上的密度、生长速率和大小结构发育的影响。秋季和春季分株群体之间初始的高度分布差异在茎秆生长过程中消失。茎秆高度和估计茎秆重量的基尼系数表明，在遮荫和未遮荫样地中，随着平均大小的增加，茎秆的大小结构变得更加均匀。在早期且可能依赖储存的生长阶段，单个茎秆的高度相对生长速率（RHGR）和重量与茎秆大小呈负相关，这表明对较小茎秆的生长有强烈支持。遮荫和未遮荫样地的平均或最大高度，以及茎秆高度与重量之间的关系均未表明有黄化现象。在两个遮荫处理年份中的一年，遮荫样地的平均茎秆密度显著低于未遮荫样地。一个回归模型表明，茎秆密度对RHGR与高度对数之间的近似线性关系有微小但显著的影响。在低茎秆密度下，小茎秆的生长速率略高于高茎秆密度时。因此，有人认为芦苇群落中直立凋落物的遮荫会降低春季分株群体的出生率，从而增加对较少小分株的支持。
