Small-scale spatial patterns of bamboos Bashania fargesii and Fargesia qinlingensis in the Qinling Mountains, China

Abstract

While the spatial distribution of bamboos may substantially affect the quality of giant panda habitats, no attempts have been made to examine the spatial pattern of bamboos at small scales. We analyzed small-scale spatial patterns of two bamboos, Bashania fargesii and Fargesia qinlingensis, that are grazed by the giant panda (Ailuropoda melanoleuca) in the Qinling Mountains, China. The analysis used univariate and bivariate Ripley’s K function, and geostatistics. Culms (live and dead) and live shoots were aggregately or randomly distributed in space with aggregation repeated. The mortality pattern of F. qinlingensis was aggregated throughout the entire study scale (0–5 m), while the mortality pattern of B. fargesii was aggregated at smaller scales< 1.3 m. The size class distribution showed more medium-sized dead culms of B. fargesii and F. qinlingensis than expected, suggesting ramet survivorship was size-dependent. The shoot distribution in space either resulted from the characteristics of clonal growth or resource limitation. Both clonal habit and resource limitation drove the observed shoot distribution pattern in F. qinlingensis throughout the entire study scale, while clonal growth was likely responsible for the shoot regeneration pattern in B. fargesii at smaller scales. A positive relationship was observed between live culms and the number of dead culms in B. fargesii and F. qinlingensis, implying the importance of intraspecific competition for resources among culms. However, a negative relationship was found between the average basal diameter and culm density in B. fargesii and F. qinlingensis, indicating density-dependent mortality among culms. Variograms revealed spatially explicit structures of culms and new shoots, and revealed repeated patterns in space. These findings imply that intraspecific competition and clonal growth habit in heterogeneous microenvironments in space generated the spatial pattern of F. qinlingensis and B. fargesii. We further concluded that the quality of giant panda habitats varied in space, based on size class distribution and spatial patterns, implying that giant panda habitat may be over-estimated.