Abstract
Litterfall is the primary source of carbon and nutrients that determine soil fertility in forest ecosystems. Most current studies have focused on foliar litter, but the seasonal dynamics and allometric scaling relationships among different litter components (e.g., foliar litter, woody litter, reproductive litter, and epiphytic litter) are poorly understood. Here, we investigated the litter production of various litter components in a sub-alpine spruce-fir forest on the eastern Tibetan Plateau based on one year of observations (from August 2015 to July 2016). Our results showed that total litter production (LT) was 2380 kg·ha−1·year−1 (3% of the aboveground forest biomass), of which 73.6% was foliar litter (LF), 15.6% was woody litter (LW), 3.0% was reproductive litter (LR), 1.3% was epiphytic litter (LE), and 6.5% was miscellaneous material (LM). The total litterfall was bimodal (with peaks occurring in April and October) and was dominated by tree species (85.4% of LT, whereas shrubs accounted for 6.8% of LT). The litter production of evergreen species (68.4% of LT) was higher than that of deciduous species (23.8% of LT). Isometric relationships were observed between litter components and the total litter (i.e., LF∝LT0.99≈1 and LR∝LT0.98≈1), and allometric relationships were also found (i.e., LW∝LT1.40>1 and LM∝LT0.82<1). However, because some components did not exhibit obvious seasonal dynamics (i.e., LE), some relationships could not be expressed using allometric equations (i.e., LE versus LT, LF versus LE, LW versus LE, and LE versus LM). Thus, the different litter components showed different seasonal dynamics, and the total litter dynamics were primarily determined by the variation in foliar litter. In addition, the allometric relationships of the forest litterfall varied with the litter components, functional types (evergreen versus deciduous) and vertical structures (tree versus shrub). This study provides basic data and a new insight for future plant litter studies.
Highlights
Forest litterfall involves active carbon and nutrient fluxes and represents a key link between tree community composition and the soil [1]; its production and input patterns are important for maintaining the stability of forest ecosystem structure and function [2,3]
Litter production is a major factor that determines the nutrient return of forest ecosystems [9], and its components affect the efficiency of material circulation [10], the rate of nutrient return [11], and litter decomposition through litter quality and dynamics [12,13]
Foliar litter was the largest component, and foliar litter production was significantly related to total litter production (R2 = 0.91, p < 0.001; Figure S1)
Summary
Forest litterfall involves active carbon and nutrient fluxes and represents a key link between tree community composition and the soil [1]; its production and input patterns are important for maintaining the stability of forest ecosystem structure and function [2,3]. Due to low temperatures and frequent geological disasters, coniferous forest ecosystems in high-altitude frigid regions have a thin mineral soil layer and poor soil development [7]; litterfall is the primary source of nutrients and energy for the soil [8]. Due to the complex terrain and dynamic climate environment, information on the litter production of coniferous forests in high-altitude frigid regions is inconsistent. In high-altitude frigid regions, litterfall may exhibit different seasonal dynamics mainly due to the short growing season and more complex climate [17,18]. The different litter components should differ in quantities and dynamics in high-altitude frigid forest ecosystems, but these factors have not received focused attention
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