From spatial patterns to ecological processes at landscape boundaries

January 30, 2023Research highlights Standard

Spatial point pattern analysis can tell us how a bamboo spreading front advances via vegetative dispersal and clonal integration.

In this case study, I went to Mt. Tianmu in Zhejiang Province, China, and found transitional regions (i.e., ecotones) between bamboo forests and deciduous broadleaf forests (one of many native forest communities there) to set up “cross-sections” that allow us to sample the bamboo spreading front. A typical sampling area of 10 meters by 90 meters with three zones (bamboo-dominant zone B, transitional mixed zone M, and tree-dominant zone F) is shown below. We censused every single stem within the sampling area and mapped their spatial locations. We also measured plant traits that are relevant to bamboo’s allocation of resources to fuel its rhizome spread.

The rapid spread of bamboo in space is not news to homeowners worldwide who have tried planting bamboo as screens to protect their privacy but ended up struggling to control its spread. The competitive exclusion of other species through shading is also well-known to farmers cultivating bamboo stands or anyone who has taken a walk within a bamboo forest. The ground is covered with pale-yellow bamboo leaves that appear to decay slowly, with only a few species of shrubby or herbaceous bamboo standing in the understory. If you’re fortunate enough to visit at the right time, you’ll witness emerging bamboo shoots sprouting from the rhizome underground, pointing straight up into the air, showcasing remarkable structural integrity. These shoots can reach their maximum height in less than two months! The process of producing these shoots is a deliberate decision made by bamboo at the colony level—the location of new shoots determines their resource levels within the bamboo stand and their contribution to the collective spatial spread through rhizome extension. Deciphering the patterns of such distribution at the forefront of bamboo spreading is the first step towards understanding the process of bamboo expansion, moving beyond simply documenting their spatial expansion from ground and satellite observations.

The spatial distributions of bamboo and tree stems were not random at their transitional interfaces and were affected by competition. Successful bamboo expansion into trees required close coordination between stems and rhizomes within a colony, as they served different functions in clonal integration. Our study initiates a scale-dependent analysis of shifts in bamboo-tree boundaries, which provides insights on how to accurately predict future bamboo distributions under climate change accounting for interspecific competition and bamboo’s clonal integration of resources.

This work has been published in Landscape Ecology. You can view the full article here.

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