Soil phosphorus does not keep pace with soil carbon and nitrogen accumulation following woody encroachment. (7th February 2018)

• Record Type: Journal Article
• Authors: Zhou, Yong; Boutton, Thomas W.; Wu, X. Ben
• Is Part Of: Global change biology. Volume 24:Number 5(2018)
• Page Start: 1992
• Page End: 2007
• Publication Date: 2018-02-07
• Subjects: landscape scale -- N2 fixation -- soil C‐N‐P imbalance -- soil profile -- spatial patterns -- structural equation models -- subtropical savanna -- woody encroachment; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14048
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: Soil carbon, nitrogen, and phosphorus cycles are strongly interlinked and controlled through biological processes, and the phosphorus cycle is further controlled through geochemical processes. In dryland ecosystems, woody encroachment often modifies soil carbon, nitrogen, and phosphorus stores, although it remains unknown if these three elements change proportionally in response to this vegetation change. We evaluated proportional changes and spatial patterns of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) concentrations following woody encroachment by taking spatially explicit soil cores to a depth of 1.2 m across a subtropical savanna landscape which has undergone encroachment by Prosopis glandulosa (an N2 fixer) and other woody species during the past century in southern Texas, USA. SOC and TN were coupled with respect to increasing magnitudes and spatial patterns throughout the soil profile following woody encroachment, while TP increased slower than SOC and TN in topmost surface soils (0–5 cm) but faster in subsurface soils (15–120 cm). Spatial patterns of TP strongly resembled those of vegetation cover throughout the soil profile, but differed from those of SOC and TN, especially in subsurface soils. The encroachment of woody species dominated by N2 ‐fixing trees into this P‐limited ecosystem resulted in the accumulation of proportionally less soil P compared to C and N in surface soils; however, proportionally more P accrued in deeper portions of the soil profile beneath woody patches where alkaline soil pH and high carbonate concentrations would favor precipitation of P as relatively insoluble calcium phosphates. This imbalanced relationship highlights that the relative importance of biotic vs. abiotic mechanisms controlling C and N vs. P accumulation following vegetation change may vary with depth. Our findings suggest that efforts to incorporate effects of land cover changes into coupled climate–biogeochemical models should attempt to represent C‐N‐P imbalances that may arise following vegetation change. Abstract : We evaluated how woody encroachment affects landscape‐scale changes in soil organic C (SOC), total N (TN), and total P (TP) throughout the 1.2 meter profile. SOC and TN were coupled with respect to increasing magnitudes and spatial patterns, while soil TP increased slower than SOC and TN in topsoil but faster in subsoil. This imbalanced relationship is likely due to differences in the biotic/abiotic mechanisms that control C and N vs. P accumulation, and to variation in the relative importance of these mechanisms with depth in the profile.