Contrasting ecosystem recovery on two soil textures: implications for carbon mitigation and grassland conservation

Abstract

Abstract. Understanding processes that promote or constrain ecosystem recovery from disturbance is needed to predict the restorative potential of degraded systems. We quantified a suite of ecosystem properties and processes across two chronosequences of restored grasslands on contrasting soil textures to test the hypothesis that restorations on silty clay loam soil would exhibit greater recovery of soil carbon (C) and nitrogen (N) pools and fluxes than on loamy fine sand because soil with higher clay content possesses a greater capacity to physico-chemically protect organic matter. Warm-season grass aboveground net primary productivity was similar between the two soil textures. Root biomass increased and root quality (as indexed by C:N ratio) decreased across both chronosequences. An asymptote in the accumulation of N in roots in the silty clay loam chronosequence resulted in wider C:N ratios of roots than in the loamy fine sand chronosequence. Total soil C (TC) and microbial biomass C (MBC) increased across the silty clay loam chronosequence at 21.2 and 5.7 g CÁm À2 Áyr À1, respectively, and contained .6 times the amount of C in large macroaggregates and nearly 3 times the aggregate mean weighted diameter (MWD) relative to cultivated soil following 15 yrs of restoration. In contrast, there were no changes in TC, MBC, or MWD in the loamy fine sand chronosequence. Total and microbial biomass N increased at 2.0 and 0.27 g NÁm À2 Áyr À1 , respectively, across the silty clay loam chronosequence, and restored soil contained nearly 6 times large macroaggregate N than cultivated soil following 15 yrs of restoration. Potential net N mineralization rates declined with years of grass establishment in both soil textures, but overall rates were lower in the silty clay loam soil relative to the loamy fine sand, which was attributed to lower quality root systems, more improved soil structure, and larger microbial biomass. Thus, the potential for restored agricultural lands to mitigate CO 2 emissions over the short term cannot be generalized across all soils. Lastly, the low restorative potential of cultivated loamy fine sand soil through grassland restoration within two decades (relevant to many conservation programs) underscores the need to prioritize preservation of remnant sand prairies.

Toward an Era of Restoration in Ecology: Successes, Failures, and Opportunities Ahead

“…Several studies suggest that this is a common pattern in restoration (Fagan et al 2008, Prach 2003, Pywell et al 2002, Seabloom & van der Valk 2003. This scenario may indicate that some restoration sites need additional attention to abiotic conditions, such as reducing nutrient loads or increasing flooding frequency, or that some sites have lower restorative potential than others (e.g., prairies in loamy versus sandy soil; Baer et al 2010). Variability could also indicate additional dispersal constraints or propagule pressure owing to landscape location (Matthews et al 2009a).…”

Physiological shifts in the microbial community drive changes in enzyme activity in a perennial agroecosystem

“…Perennial cropping systems, such as those proposed for cellulosic bioenergy production, may promote plant-microbial linkages because of their extensive root networks and allocation of belowground C. The development of perennial root systems during grassland restoration represents a significant source of C inputs to soils that stimulates microbial biomass and activity and can change community composition Bach et al 2010;Baer et al 2010;Barrett and Burke 2000;Camill et al 2004;McKinley et al 2005). Carbon additions from perennial root systems may also affect microbial communities in cultivated soils.…”

Soil carbon and nitrogen recovery on semiarid Conservation Reserve Program lands

“…Soil physical characteristics had an important influence on the abundance of SOC and N. A large percentage of total SOC and N was associated with clay in CRP fields due to the physical and chemical stability provided by mineral organic binding (Baer et al, 2010). Bulk density was also associated with SOC and N. Two-year old CRP fields had higher than expected total SOC and N because there was a greater mass of surface soil (0e5 cm) at these compacted sites.…”