Organic Matter Dynamics in Reclaimed Lignite Mine Soils underRobinia pseudoacaciaL. Plantations of Different Ages in Germany

Abstract

In temperate regions, cultivation of Robinia pseudoacacia L. has recently received considerable attention because it is a fast-growing species for biomass and bioenergy production, while acting as a potential carbon (C) sink to counterbalance carbon dioxide (CO 2 ) emissions and an alternative to agricultural crops on marginal sites. The objective of our work was to compare total organic carbon (TOC), total nitrogen (TN), and organic C fractions in postlignite mining soils under different development stages of R. pseudoacacia. Soil samples from three different depths (0-3, 3-10 and 10-30 cm) were taken in plantations 2, 3, 4, and 14 years old (R2, R3, R4, and R14, respectively). The TOC and TN contents increased with increasing tree age in all layers (P < 0.01). In the top 30 cm, TOC and TN stocks ranged from 11.7 to 59.8 Mg C ha −1 and from 0.30 to 2.61 Mg N ha −1 at R2 and R14, respectively. The rate of C sequestration was calculated to be 4.0 Mg C ha −1 year −1 . Microbial biomass C and N were strongly correlated to TOC (r 2 = 0.96 -0.81; P < 0.001) and TN contents (r 2 = 0.92 -0.91; P < 0.001). The light fraction C (C LF ) accounted for 15-30% and the heavy fraction C for 70% of TOC in all layers. In the 0-to 3-cm layer, C LF increased by 0.5 g kg −1 year −1 . The results indicate that plantations of R. pseudoacacia are an attractive alternative to increase soil C contents in reclaimed lignite mining soils. In the short term, microbial biomass C and light fraction C are sensitive and provide an appropriate measure to assess soil C changes caused by cultivation of R. pseudoacacia.

Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services

“…Perennial WSGs without fertilizers or organic amendments may not sequester more than 1 Mg ha −1 of soil C per year (Blanco-Canqui et al, 2014). Data on C sequestration potential under SRWCs are very limited, but the study by Matos et al (2012) suggested that a black locust SRWC can sequester as much as 4 Mg ha −1 of soil C on reclaimed minesoils.…”

“…Soils with low initial C levels (Matos et al, 2012) can more rapidly accumulate C after the establishment of perennials compared with those with high initial C levels (Evers et al, 2013). For example, as discussed above, highly disturbed soils such as minesoils can sequester C in the soil at high rates (Matos et al, 2012).…”

“…These rates of C sequestration can be increased if perennial WSGs or SRWCs are planted on these reclaimed lands. For example, planting SRWCs on reclaimed minesoils could sequester as much as 4 Mg ha −1 yr −1 of soil C in the upper 30 cm of the soil (Matos et al, 2012). Because reclaimed minesoils are low in initial soil organic C concentration, they can more rapidly accumulate soil C compared with prime agricultural lands, which often have higher levels of organic C. The level of soil disturbance, soil profile characteristics after reclamation, initial soil C level, and management (e.g., application of amendments) will dictate biomass yields and the rate of soil organic C sequestration in reclaimed soils.…”

“…Soils with low initial C levels (Matos et al, 2012) can more rapidly accumulate C after the establishment of perennials compared with those with high initial C levels (Evers et al, 2013). For example, as discussed above, highly disturbed soils such as minesoils can sequester C in the soil at high rates (Matos et al, 2012). Regarding the type of land transition, Qin et al (2016) reported that cropland conversion to energy crops resulted in a 6 to 14% increase in the soil C concentration, while conversion from grassland or forest to switchgrass, miscanthus, or willow did not increase soil C levels.…”

Phosphorus Sorption Kinetics in Reclaimed Lignite Mine Soils under Different Age Stands ofRobinia pseudoacaciaL. in Northeast Germany

“…Besides, as a N 2 fixing tree, it can also improve soil fertility through increase in soil OM input and thereby greatly improve and increase nutrient content and availability [7][8][9][10][11][12][13]. The cultivation of R. pseudoacacia is considered as a good method for land reclamation [6,11,[14][15][16]. It grows very fast especially during the young stages of development and it has been reported that on reclamation sites in the Lusatia region the aboveground growth rates were about 5.8 t ha −1 year −1 [5] and can reach up to 9.5 t ha −1 year −1 in the older plantation [17].…”