Topography Significantly influences the Growth Dynamics of Moso Bamboo Along a 10-year Chrono Sequence Following Afforestation

Topography plays a critical role in the growth, development, and carbon accumulation of Moso bamboo. However, it is still unknown whether the effects of topography on the newly sprouted culms, the diameter at breast height (DBH) and the carbon stocks of newly sprouted culms (called carbon stocks below) vary temporally following Moso bamboo afforestation. In this study, thirty-one 20 x 20 m long-term sample plots were established and the DBH, age, height, and coordination of every newly sprouted culm were measured from 2009 to 2018. Four Moso bamboo expansion periods (rhizome expansion period, early period, middle period, and stable period) were divided according to the patterns of change of newly sprouted culms. Structural equation modeling and univariate analysis were combined to assess the dynamic effects of topographic factors (slope, aspect, slope position, and topographic complexity) and the effect of single topographic factors and their interactions on the carbon stocks during the four expansion periods. The result showed that the leading topographic factors influencing DBH, newly sprouted culms and carbon stocks were depended on the expansion period. Furthermore, the effective degree of leading topographic factor, aspect, decreased from the early period to a stable period. The four topographic factors studied here did not influence carbon stocks and newly sprouted culms during the stable period. The optimal interactions between carbon stocks and slope position and aspect (an east aspect of lower and upper slope positions) were relatively larger than those of a single aspect (east aspect), and significantly decreased in a stable period. Low topographic complexity was beneficial to the carbon accumulation under abrupt slopes but middle topographic complexity was needed under steeper slopes (steep and dangerous slope). Overall, this study offers a greater understanding of the effect of topography on Moso bamboo growth and provides a scientific basis for the selection of suitable afforestation locations for forest management.