Biomass allocation pattern of urban shrubs in the Yangtze River Delta region, China – A field observation of 13 shrub species

Abstract

As a crucial part of urban green space, urban shrub biomass and biomass allocation play an important role in the urban carbon cycle. However, the current body of research mainly focuses on natural vegetation, and the biomass allocation patterns of urban shrubs remain poorly addressed. In this study, whole-plant harvests of 13 common urban shrubs in the Yangtze River Delta region were conducted to ascertain their biomass allocation patterns (i.e., leaf mass fraction (LMF), stem mass fraction (SMF), root mass fraction (RMF), and root/shoot ratio (R/S)) as well as the effects of ontogeny (i.e., plant height) and leaf traits (evergreen and deciduous). Our findings were as follows: (1) Among the 13 urban shrubs, the mean values of LMF, SMF, RMF and R/S were 0.22, 0.47, 0.31, and 0.46. Specifically, nine species had the most resources invested in stems, whereas four species exhibited similar proportion of roots and stems. (2) With increasing plant height, the changes in shrub biomass allocation to organs could be divided into three categories: 1) eight shrub species displayed increased partitioning of resources to stems (SMF) and decreased partitioning to leaves (LMF) and roots (RMF); 2) two shrub species shifted biomass from leaves to stems, with RMF remaining stable; and 3) three shrub species exhibited no response to increasing plant height. (3) Evergreen shrubs had higher LMF values (0.26 vs. 0.17) and lower SMF values (0.42 vs. 0.54) compared to deciduous species (P < 0.05), and their RMF and R/S values did not differ significantly (P> 0.05). We concluded that urban shrub biomass allocation was influenced by both plant ontogeny and leaf traits, and the data presented in this study could be made available for the precise estimation of regional urban shrub biomass and carbon storage.