Characteristics of Fine Roots of Pinus massoniana in the Three Gorges Reservoir Area, China

Abstract

Several studies have focused on fine roots characteristics because they provide a major pathway for nutrient cycling and energy flow in forest ecosystems. However, few studies have evaluated changes in fine root characteristics according to their diameter. Pinus massoniana forests are the main vegetative component in the Three Gorges Reservoir area and play an important role in providing forest resources and ecological services. Pinus massoniana fine roots were sorted into 0-0.5, 0.5-1, and 1-2 mm diameter classes, and their fine root standing biomass (FRB), necromass, annual production and decomposition rates were determined and correlated with soil characteristics. These fine roots in three diameter classes significantly differed in their initial carbon (C), C/N ratio, FRB, necromass, annual C and N production and decomposition rate. The production and decomposition of these different diameter classes varied significantly with soil variables including soil temperature, moisture, calcium and ammonium concentration but the strength of these interactions varied dependent on diameter class. The very fine roots had a faster decomposition ratio than larger fine roots due to the lower N content, higher C/N ratio and higher sensitivity to soil environmental factors. These results clearly indicate heterogeneity among fine roots of different diameters, and these variations should be taken into account when studying fine root characteristics and their role in the C cycle.

Heterogeneity in Decomposition Rates and Nutrient Release in Fine-Root Architecture of Pinus massoniana in the Three Gorges Reservoir Area

“…However, there have been few studies performed on fine-root decomposition and nutrient cycling of P. massoniana. In the two previous studies on the decomposition of fine roots [36,37], the results regarding the regularity of decomposition do not agree. It is possible that arbitrary diameter cutoffs may mask decomposition heterogeneity within fine-root branching systems [28].…”

“…The roots initially had a higher C:N ratio (low-N concentration) than microbes, but N immobilization from exogenous N is required to balance the microbial C:N ratio [32,40]. In the later stages of decomposition (days 120-360) when the C:N ratio reached critical values (35)(36)(37)(38)(39)(40), root residual N began to show the opposite trend regarding immobilization or release (Figures 2b and 3). These results agree with those from a previous meta-analysis of~2800 observations which reported that the critical value was from 67 to 77 during plant litter decomposition [40].…”

Coupling of different plant functional group, soil, and litter nutrients in a natural secondary mixed forest in the Qinling Mountains, China

“…2f), which is inconsistent with previous research (He et al 2008). This inconsistency might be caused by the roots not being classi ed into more ne classes, as ne roots (diameter < 2 mm) were not evaluated separately, because ne roots have higher N and P nutrient concentrations than coarse roots (Shen et al 2017). Previous studies have proposed that a leaf N:P ratio < 14 indicates N limitation, while a N:P > 16 indicates P limitation (Koerselman and Meuleman 1996).…”

Short-Term Effects of Low Intensity Thinning on the Fine Root Dynamics of Pinus massoniana Plantations in the Three Gorges Reservoir Area, China

“…Fine roots are primarily responsible for nutrient and water acquisition from the soil [45,53,54]. The relationships of fine root dynamics and soil temperature, moisture, and nutrients have been widely reported, but the results of these studies are not consistent [20,[55][56][57][58][59].…”