Effects of different planting configurations and clones on biomass and carbon storage of a 12-year-old poplar ecosystem in southern China

Abstract

The main objective of this study was to compare the effects of two densities (278 stems·ha−1 with two spacings of 6 m × 6 m or 4.5 m × 8 m, 400 stems·ha−1 with two spacings of 5 m × 5 m or 3 m × 8 m) and three poplar clones (NL95, NL895, and NL797) on productivity and carbon (C) sequestration of poplar ecosystems. The results showed that planting density significantly affected the biomass of a single tree. The mean tree biomass of clone NL95 was higher in all spacings than that of the other clones, with a significant difference for the 6 m × 6 m spacing. The biomass of poplar trees ranged from 78.9 to 110.3 Mg·ha−1, with the highest tree biomass observed in the square configuration. Soil C concentration (0–100 cm) increased after 12 years of management. Soil C storage ranged from 138.1 to 164.3 Mg C·ha−1, and the highest soil C storage was in the NL797 poplar plantation with 6 m × 6 m spacing. Our results suggested that clones NL95 and NL797 should be chosen for planting, with a planting density of 278 stems·ha−1 and spacing of 6 m × 6 m.

Early Dynamics of Carbon Accumulation as Influenced by Spacing of a Populus deltoides Planting

“…Tree height, DBH, and AGB I were influenced by spacing such that each of these variables tended to increase as the spacing or area available to the tree increased. Consistent with the growth of poplars in other studies, height was mildly responsive to spacing while DBH and AGB I were considerably responsive [40,41,61,62]. Fang et al [63], who worked in the Jiangsu Province of China, confirmed genetic control over the correlation between DBH and crown volume for 14 eastern cottonwood clones native to the southeastern United States, but they also recognized the strong impact of environment on this relationship.…”

“…Evaluated against some other reports for poplars raised in SRWC systems across the temperate zone, early AGC stocks at our study site appear underwhelming [39,41,65,71]. The AGC stocks calculated for an eastern cottonwood planting spaced 3.7 × 3.7 m in Issaquena County, MS, USA, reveal that the similarly spaced stands at our study site accumulated 28.5 Mg ha −1 less carbon by year 10 [55].…”

“…Prior work in plantings of eastern cottonwood and other poplars explored the role of spacing on tree survival and growth in SRWCs [38,40,55,58]. Some studies clearly illustrate increased tree mortality associated with inter-tree competition that intensifies as spacing decreases [55,56,58], though this relationship is not apparent through rotation lengths conventional to SRWCs in other studies [40,41]. Various factors can contribute to mortality in young poplar plantations.…”

“…Additional factors include silvicultural decisions such as species and clonal selection, plantation spacing, and management regime (fertilization, irrigation, weed/pest control practices, and rotation length). All of these will impact annual increment and total carbon accumulation realized for a given planting [15,[39][40][41]58,[65][66][67]. Due to the extensive variability of these factors across studies reported from throughout the temperate zone, calculated rates of CAI AGC and MAI AGC in young poplar plantings range substantially.…”

“…Work on poplar SRWC systems in the temperate zone illustrates that planting arrangement and spacing hold a prevailing influence over tree growth and stand development [33,34]. This ultimately translates to affect variables that inform deci-sions relevant to bioenergy feedstock production such as feedstock dimension, feedstock quality, total biomass yield, and optimal rotation length [35][36][37][38]; additional variables that inform decisions relevant to a carbon stock objectives including tree allometry, stand-level carbon accumulation increment, and soil carbon status [39][40][41].…”