Carbon Stocks in a 20-Year-Old Coniferous Plantation ‒ A Case Study in Fandoghloo Region, Northwestern Iran

Abstract

Abstract. In Fandoghloo region, northwestern Iran, tree plantations were established on a degraded rangeland, which was previously mainly used for grazing. We assessed the above-and belowground ecosystem biomass and carbon (C) pools of pure and mixed Pinus nigra, Cedeus libani and Picea abies plantation stands (20 years-old) in Ardabil, Iran. Biomass and C stocks of above-and belowground tree biomass and litter were determined from plot-level inventories. Mineral soil C stocks were estimated from soil cores at three depths 0-15, 15-30 and 30-50 cm. Our results showed an increase in the total ecosystem carbon stock after the afforestation. The highest total carbon stock was 55.57 Mg ha -1 in the mixed P. nigra -C. libani and it was 25.006 Mg ha -1 in the degraded rangeland. The carbon stock in the aboveground biomass ranged from 2.4 Mg ha -1 in the degraded rangeland to 19.28, 15.1, 6.17, 4.55, and 3.87 Mg ha -1 in the P.nigra -C. libani, P.nigra, P. abies-P.nigra, C. libani and P. abies stands, respectively. The amount of litter carbon stock ranged from 0.53 Mg ha -1 in the degraded rangeland to 3.51, 3.06, 2.03, 1.55, 1.41 Mg ha -1 in the P. abies-P.nigra, P.nigra-C. libani, P.nigra, C. libani and P. abies stands, respectively. The soil carbon stock increased from 21.41 to 30.11, 28.58, 28.41, 27.45 and 25.43 Mg ha -1 in the C. libani, P.nigra, P.nigra -C. libani, P. abies -P.nigra and P. abies stands, respectively. Significant interactions were observed between stand and soil depth on carbon stock after rangeland afforestation with coniferous species. Aboveground tree biomass became the major ecosystem C pool. The difference in total ecosystem C between the degraded rangeland and mixed P.nigra -C. libani stand was 30.56 Mg ha -1 . The highest SOC accumulation was observed in the surface layer of the C. libani (34.95 Mg ha -1 ), but the accumulation rate is species dependent. Our results highlight the importance of coniferous plantations on degraded rangeland that will most probably increase the rate of C sequestration and thereby mitigate the negative effects of increasing atmospheric CO 2 concentrations. As a matter of fact, the selection of appropriate species and plantation will be considered in the next afforestation projects.

Latitude or altitude as the future refugium? A case for the future of forests in Asia Minor and its surroundings

“…Pinus nigra , a drought‐resistant temperate conifer with an affinity for the continental climate (Candel‐Pérez et al., 2022) takes dominance in Central Anatolia and on the edges of the Central Iranian Highlands in our simulations (prioritizing mid‐latitudes) where our datasets forecast a warming and drying trend for the end of the century. P. nigra 's survival success in plantations in northern Iran where it is not a native species has been documented in separate studies (Fataei, 2016; Picchio et al., 2022; Tavankar et al., 2018). The taxon is native to Central Anatolia, and in our simulations not only consolidates its spatial density dominance in this region, but also increases its biomass.…”