Temporal changes of fine root overyielding and foraging strategies in planted monoculture and mixed forests

Abstract

BackgroundMixed forests are believed to enhance ecosystem functioning and sustainability due to complementary resource use, environmental benefits and improved soil properties. The facilitation between different species may induce overyielding. Meanwhile, the species-specific fine root foraging strategies and tradeoffs would determine the structure and dynamics of plant communities. Here the aim was to investigate the admixing effects of fine-root biomass, vertical distribution and morphology in Pinus massoniana–Cinnamomum camphora mixed plantations and corresponding monocultures at 10-, 24- and 45-year old stands.ResultsThe fine root biomass in the Pinus–Cinnamomum mixed forest exerted a certain degree of overyielding effect. These positive admixing effects, however, did not enhance with forest stand development. The overall relative yield total ranged from 1.83 and 1.51 to 1.33 in 10-, 24- and 45-year-old stand, respectively. The overyielding was mainly attributed to the over-performance of late successional species, Cinnamomum, in mixed stands. The vertical fine root biomass distribution model showed fine roots of pioneer species, Pinus, shifted to the superficial layer when mixed with Cinnamomum. Furthermore, the specific root length (SRL) of Pinus was significantly higher in Pinus–Cinnamomum mixed stands than that in monocultures, and the magnitude of differences increased over time. However, the vertical fine-root distribution and SRL for Cinnamomum did not show significant differences between monoculture and mixtures.ConclusionsOur results indicated that the magnitude of fine root overyielding in mixed forests showed a high degree of consistency with the total amount of fine root biomass itself, suggesting the overyielding effects in mixed forests were correlated with the degree of belowground interaction and competition degree involved. The late successional species, Cinnamomum, invested more carbon to belowground by increasing the fine root biomass in mixtures. While the pioneer species, Pinus, adapted to the presence of the species Cinnamomum by modification of vertical distribution and root morphological plasticity in the mixtures. These species-specific fine root foraging strategies might imply the differences of forest growth strategies of co-occurring species and contribute to the success and failure of particular species during the succession over time.

Fine Root Dynamics in Three Forest Types with Different Origins in a Subalpine Region of the Eastern Qinghai-Tibetan Plateau

“…In spite of previous studies that estimated that mixed forests have higher production rates compared to monoculture forests [29,68], our result showed that P. asperata plantation had a higher fine root biomass within the entire profile. It agreed more with the study that demonstrated fine root Fine root turnover rate was negatively associated with annual fine root production in the soil depth of 0-10 cm (Figure 6a), but was positively related to fine root production in the soil depths of 10-20 cm and 20-30 cm (Figure 6b) across all forest types.…”

“…In spite of previous studies that estimated that mixed forests have higher production rates compared to monoculture forests [29,68], our result showed that P. asperata plantation had a higher fine root biomass within the entire profile. It agreed more with the study that demonstrated fine root biomass was lower in mixed forests than in the corresponding monoculture forests [38].…”

“…Belowground interaction among co-occurring species is vital for community structure and functioning [29]. The coexisting species tend to proliferate more roots into substrate, which likely lead to a higher fine root production or biomass in mixed forests than in monocultures [30].…”

Seasonal Changes and Vertical Distribution of Fine Root Biomass During Vegetation Restoration in a Karst Area, Southwest China

“…The successional changes in tree density with stand development could contribute to the observed patterns. In this study, the fine root biomass of secondary forests and primary forests in the 0–30 cm soil layer was lower than that in non-karst communities in a subtropical region (Hunan Province) that included 10- and 24-year-old mixed plantations of Pinus massoniana and Cinnamomum camphora (Shu et al, 2018), but similar to that of the 45-year-old stands. Moreover, the fine root biomass of karst vegetation in Maolan, bordering our study area, show similar results (Ni et al, 2015).…”

“…Extensive studies have indicated that fine root biomass, necromass, and production vary with vegetation types, and that they vary considerably among the different soil horizons owing to varied water and nutrient content in different soil layers (Hansson et al, 2013; Wang W. et al, 2016; Shu et al, 2018). In most ecosystems, roots tend to be most abundant in the topsoil layer, decreasing exponentially with increasing soil depth (Zhou et al, 2016).…”