Effects of fertilization on the relations of diameter at breast height between different-aged ramets of Phyllostachys edulis population

Abstract

Aims Clonal plants are physiologically integrated, allowing translocation of photosynthates, water, nutrients and other substances between connected ramets within a clone. This suggests that the sizes of ramets of different ages may be correlated. So far, however, little is known about the effects of fertilization on the size relationships between ramets of different ages. In this study, we aim to examine how fertilization affects the relations of diameter at breast height(DBH) between ramets of different ages in the giant clonal bamboo Phyllostachys edulis. Methods We established 112 20 m × 30 m plots of P. edulis in Longquan City, Zhejiang Province, China. Among them, 46 plots were fertilized only in 2008, 49 fertilized in five consecutive years from 2004 to 2008, and 17 unfertilized(the control). We measured DBH of ramets of one, three and five years old in each plot in 2009. The relations of DBH between ramets of different ages in different fertilization treatments were examined using allometric scaling by the standardized major axis(SMA) analysis, and that were also analyzed by multiple linear regression. Important findings The DBH of the 1-year-old ramets was significantly greater than that of the 5-year-old ones in the 5-year fertilization plots, while no significant difference was found in the 1-year fertilization plots. Under different fertilization treatments, the slopes of SMA(0.88–1.10) for the relations of DBH between ramets of one, three and five years old were not significantly different from 1.00(p 0.05), suggesting isomeric growth relationships. Compared to the control(unfertilization), fertilization in one or five years did not change the slope of SMA. However, fertilization in five years increased the intercept of SMA, indicating that continuous fertilization could result in greater DBH increment in the 1-year-old ramets. The multiple linear stepwise regression analysis indicated that 3-year-old ramets could greatly influence DBH of the newly produced ramets, and that the effect of DBH of the 5-year-old ramets on that of the 1-year-old ramets increased after five years of continuous fertilization.