Accumulation of carbon and nitrogen by old arable land reverting to woodland

Abstract

The accumulation of carbon (C) and nitrogen (N) was measured on two sites on Rothamsted Farm that had been fenced off some 120 years ago and allowed to revert naturally to woodland. The sites had previously been arable for centuries. One had been chalked and was still calcareous; the other had never been chalked and the pH fell from 7.1 in 1883 to 4.4 in 1999. The acidic site (Geescroft wilderness) is now a deciduous wood, dominated by oak (Quercus robor); the calcareous site (Broadbalk wilderness) is now dominated by ash (Fraxinus excelsior), with sycamore (Acer pseudoplatanus) and hawthorn (Craetagus monogyna) as major contributors. The acidic site gained 2.00 t C ha−1 yr−1 over the 118‐year period (0.38 t in litter and soil to a depth of 69 cm, plus an estimated 1.62 t in trees and their roots); the corresponding gains of N were 22.2 kg N ha−1 year−1 (15.2 kg in the soil, plus 6.9 kg in trees and their roots). The calcareous site gained 3.39 t C ha−1 year−1 over the 120‐year period (0.54 t in the soil, plus an estimated 2.85 t in trees and roots); for N the gains were 49.6 kg ha−1 yr−1 (36.8 kg in the soil, plus 12.8 kg in trees and roots). Trees have not been allowed to grow on an adjacent part of the calcareous site. There is now a little more C and N in the soil from this part than in the corresponding soil under woodland. We argue from our results that N was the primary factor limiting plant growth and hence accumulation of C during the early stages of regeneration in these woodlands. As soil organic N accumulates and the sites move towards N saturation, other factors become limiting. Per unit area of woodland, narrow strips; that is, wide hedges with trees, are the most efficient way of sequestering C – provided that they are not short of N.

Species and Genotype Effects of Bioenergy Crops on Root Production, Carbon and Nitrogen in Temperate Agricultural Soil

“…1) with the same units (replacing 'root' with 'SOC' or 'TN'). Following others [18,31], we used an 'equivalent soil mass' approach to adjust the measured SOC and TN density of the initial baseline data to that based on the bulk density measured after 4 and 6 years, which did not differ significantly. For only the soils collected from Miscanthus plots, the 13 C/ 12 C stable isotope ratios were quantified on prepared carbonate-free soil [23] with an IsoPrime 100 Stable Isotope Ratio Mass Spectrometer (Isoprime Ltd., Cheadle Hulme, UK) coupled with a Vario MICRO Cube Elemental Analyser (Elementar Analysensysteme GmbH, Langenselbold, Germany).…”

Impacts of land-use history on the recovery of ecosystems after agricultural abandonment

“…Additionally, most of the available studies were conducted in Amazonia or North America and there is large variability in physical and biotic characteristics as well as in land management (Kauffman et al, 2009). Many studies focus on the recovery of biodiversity or species richness (Cramer et al, 2008;Queiroz et al, 2014), but these variables cannot be adequately captured by our large-scale PFT approach. It is often assumed that the ecosystem will gradually return to its previous state and that intensive LU delays recovery but the timescales are widely unknown and differ across variables and regions, e.g., tropical species composition recovers much slower than forest structure and soil nutrients (Chazdon, 2003).…”

“…Analyses of the long-term effects of historical LU are often limited by the availability of adequate LU information and the absence of undisturbed ecosystems, and usually rely on chronosequences (Chazdon, 2003;Knops and Tilman, 2000). Only a few long-term observational study plots like the one maintained at the Rothamsted Experimental Station (e.g., Poulton et al, 2003) exist. Differences between (near) pristine and post-agricultural forests or grasslands have been reported to persist for decades or centuries after agricultural abandonment for various variables, including soil pH (Falkengren-Grerup et al, 2006); microbial communities (Fichtner et al, 2014); soil C, N and phosphorus (Compton and Boone, 2000); and other nutrients (Wall and Hytonen, 2005).…”

Distribution of inorganic phosphorus in profiles and particle fractions of Anthrosols across an established riparian buffer and adjacent cropped area at the Dian lake (China)

“…3). The greater accumulation of plant debris by the revegetation and the slower rate of organic matter decomposition by the lack of cultivation might have contributed to the build up of soil organic carbon (SOC) in the buffer soils (Reddy et al, 2008). There was a significant relationship between SOC and N at the research area (r = 0.944, P < 0.01).…”

“…There was a significant relationship between SOC and N at the research area (r = 0.944, P < 0.01). Several studies have indicated that the rate of SOC accumulation is controlled by the rate of N accumulation in the early stages of vegetation regeneration of abandoned agricultural soils (Knops et al, 2000;Poulton et al, 2003). Differences of SOC and N between the crop and the buffer soils were less significant as depth increased at the HG and XL sites but increased at the NL sites.…”