Elsevier

Biomass and Bioenergy

Volume 26, Issue 2, February 2004, Pages 97-105
Biomass and Bioenergy

Carbon sequestration in soil beneath long-term Miscanthus plantations as determined by 13C abundance

https://doi.org/10.1016/S0961-9534(03)00102-8Get rights and content

Abstract

Miscanthus is a perennial rhizomatous warm-season grass with C4-photosynthesis. It shows considerable production potentials (10–20t dry matter ha−1) under NW European growth conditions and plantations of Miscanthus are established to provide biomass for energy. The plant senesces in the autumn in response to adverse climatic conditions, but harvest is normally postponed until spring when the biomass is more suitable for combustion. Total pre-harvest and harvest losses may account for as much as two-thirds of autumn standing biomass and these losses provide a significant carbon input to the soil. In this study, we examine soil organic carbon (SOC) storage and turnovers beneath 9 and 16 year old Miscanthus plantations established at Hornum, Denmark (56°50′N, 09°26′E). The soil is a loamy sand (Typic Haplumbrept, coarse loamy, mixed, mesic) with a C3 vegetation history. Soil was sampled at 0–20, 20–50 and 50–100cm depth in the Miscanthus plantations and in two reference sites under C3-plants. The 0–20cm samples were divided into fine soil (<2mm), particulate organic matter (POM; 250–2000μm), rhizomes/stubbles and coarse roots. All samples were analysed for carbon content and 13C/12C ratio. Rhizomes/stubbles accounted for 10.9–12.6t DMha−1 and coarse roots for 3.2–3.7t DMha−1 at 0–20cm depth. No rhizomes and coarse roots were observed in the deeper soil layers. Concentrations of SOC were higher at all soil depths under the 16 year old Miscanthus whereas 9 years of Miscanthus and reference sites showed similar SOC concentrations. δ13C in 0–20cm reference soil averaged −27.6‰ while soil beneath 9 and 16 year Miscanthus showed −25.6‰ and −22.8‰, respectively. Difference in δ13C between reference and Miscanthus soils was smaller at greater soil depths. SOC inventories at 0–100cm ranged from 91–92t Cha−1 in reference and 9 year Miscanthus to 106t Cha−1 under 16 years of Miscanthus growing. The main part of the SOC was at 0–20 and 20–50cm soil with 30–40t Cha−1 in each layer. Although changes in the overall SOC storage were less significant, 13% and 31% of the SOC present in 0–20cm soil was derived from Miscanthus beneath 9 and 16 year plantations, respectively. The organic matter recovered in POM contained 48–65% of Miscanthus derived C. At 20–50 and 50–100cm depth, the fractions of SOC from Miscanthus were 6–9% and 1.3–6%, respectively. It was estimated that 26–29% of the cumulated C input from Miscanthus had been retained in the soil.

Introduction

Miscanthus (Miscanthus x giganteus Greef and Deu.) is a perennial rhizomatous grass native to East Asian tropic and subtropic regions and with a considerable biomass production potential even under cool temperate climatic conditions [1]. Miscanthus regularly shows an annual aboveground biomass production of 10–20t dry matter ha−1 under NW European growth conditions [2], [3], [4], [5] and research over the past two decades suggests Miscanthus as a potentially important bioenergy crop [1], [6]. Previous research has focused on management and economy in relation to establishment and productivity, harvest and storage, and combustion feasibility [6], whereas research on the impact of Miscanthus on SOC turnover remains scarce [5], [7].

The replacement of conventional cropping systems with annual crops, frequent soil tillage and relatively small returns of crop residues by a highly productive perennial bioenergy crop may introduce an increase in SOC. Under NW European climatic conditions, the harvest of Miscanthus is normally postponed until spring in order to achieve biomass with a reduced content of moisture and minerals, conditions that are desirable for biomass intended for combustion in energy plants. From late autumn when the crop becomes senescent due to adverse climatic conditions and until harvest in early spring, 25–50% of the dry matter (mostly leaves and non-woody tops) is shed from the plant [1]. Total pre-harvest and harvest losses may account for as much as two-thirds of autumn standing biomass. The biomass left after harvest will accumulate on the ground and eventually contribute to the SOC pool. Studies on other fast-growing perennial bioenergy crops (e.g. switchgrass; Panicum virgatum L.) established on cultivated land have demonstrated their ability to sequester carbon (C) in the soil, although reported responses show variable and occasionally rather moderate increases in SOC contents [8], [9], [10], [11], [12]. With regard to Miscanthus grown in NW European climate, data on C sequestration in soil is urgently needed to fully evaluate the environmental benefits of this bioenergy crop.

The discrimination against the 13C isotope associated with photosynthesis results in plant biomass that is depleted in 13C relative to atmospheric CO2 [13], the degree of depletion reflecting the type of photosynthetic pathway. Plants with the Calvin cycle pathway (C3-plants) become distinctly lower in 13C than plants with the Hatch-Slack pathway (C4-plants). Traditional crops and native vegetation in cool temperate regions are all C3-plants, while fast-growing grasses originating from warmer climate zones (e.g. maize, sugar cane and Miscanthus) rely on the C4 photosynthetic pathway. This difference between C3 and C4 plants in 13C abundance provides a unique tool to study C turnover on sites where long continued C3 vegetation has been replaced by C4 plants [14], [15], [16].

In this study, we report on C sequestration and turnovers in soil beneath 9 and 16 year old Miscanthus plantations established on a loamy sand with an arable history of C3 plants. Measurements of the 13C/12C ratios in the soil down to 100cm depth in Miscanthus plots and in nearby reference plots with a C3 plant history allow us to estimate the fraction of SOC derived from Miscanthus as well as changes in overall SOC storage. Recently a similar approach has been adopted for switchgrass sites situated under a considerably warmer climate in the south-eastern USA [10].

Section snippets

Site

Soil was sampled in May 1999 from two adjacent experimental fields (field A and H) at Hornum, North Jutland, Denmark (56°50′N, 09°26′E) carrying Miscanthus plantations of different age. The Miscanthus was established in a 1 by 1m2 grid (one plant per m2) in field A in 1983 (16-year old in 1999; termed Mis-16) and in field H in 1990 (9-year old in 1999; termed Mis-9). Two nearby fields without any history of C4 plants were sampled for reference, Ref-1 in May 1999 and Ref-2 in November 2000.

Biomass production

Aboveground production and harvestable plant biomass have been reported by Jørgensen [20]. Dry matter yields at spring harvest varied between 8 and 15tha−1 in the period from 1986 to 1992 in the Miscanthus plantation established in 1983 (Mis-16). From 1993 to 1996, yields have been 8tha−1 or less due to effects of severe drought in 1992 and frost in early June 1993 [20].

The amount of dry matter recovered in rhizomes/stubbles varied between cylinders (Table 1), with average yields of 10.9 and

Conclusions

Cultivation of Miscanthus for 9–16 years caused only moderate changes in the SOC storage on this coarse loamy soil. However, measurements of changes in stable C isotope ratios revealed that a large fraction of the SOC pool was accounted for by Miscanthus derived C. After 9 and 16 years, respectively, 13% and 31% of the SOC present at 0–20cm was derived from Miscanthus. This indicates that a significant fraction of the SOC in this soil layer is involved in short- to medium-term turnovers. In the

Acknowledgements

We gratefully acknowledge the valuable support provided by our colleagues Uffe Jørgensen and Jens Bonderup Kjeldsen, Department of Agroecology, Danish Institute of Agricultural Sciences. We appreciate their commitment to the Miscanthus experiments. This work was financially supported by The Danish Energy Agency (Project: Biomass for energy: effects on the soil carbon balance in agriculture and forestry, grant no. 51161/98-0036).

References (33)

  • G. Cadisch et al.

    Carbon turnover 13C) and nitrogen mineralization potential of particulate light soil organic matter after rainforest clearing

    Soil Biology and Biochemistry

    (1996)
  • B.T. Christensen et al.

    Soil organic matter and soil quality—lessons learned from long-term experiments at Askov and Rothamsted

  • M. Himken et al.

    Cultivation of Miscanthus under West European conditionsseasonal changes in dry matter production, nutrient uptake and remobilization

    Plant and Soil

    (1997)
  • S. Beuch et al.

    Effect of the organic residues of Mischanthus x giganteus on the soil organic matter level of arable soils

    Journal of Agronomy and Crop Science

    (2000)
  • U. Jørgensen et al.

    Why do basic research? A lesson from commercial exploitation of Miscanthus

    New Phytologist

    (2000)
  • P. Kahle et al.

    Auswirkungen des Anbaus von Miscanthus x giganteus auf chemische und physikalische Bodeneigenschaften

    Zeitschrift für Pflanzenernährung und Bodenkunde

    (1999)
  • Cited by (158)

    • Mound plantation as an effective climate change adaptation and mitigation measure: Evaluation of the growth in the Chittagong coastal forest division of Bangladesh

      2021, Environmental Challenges
      Citation Excerpt :

      To fully understand the carbon sequestration of a region, species and site-specific carbon data are necessary. Scientists identified the forest carbon sequestration in many regions of the world (Cannell, 2003; Hansen et al., 2004; Ismail, 1995; Karjalainen, 1996; Pussinen et al., 1997; Ravindranath and Somashekhar, 1995). Shin et al. (2007) have estimated that, on average, 92 tC ha−1 is stored by tree tissues in the forests of Bangladesh: more specifically, closed-large-crown forests 110 tC ha−1; and disturbed open forests 49 tC ha−1.

    View all citing articles on Scopus
    View full text