Recovery of ecosystem properties during tallgrass prairie restoration

Background/Question/Methods

Restoring tallgrass prairie drives recovery of ecosystem properties. Disturbance by tillage and compaction degrades soil structure. Restoring perennial plants to agriculturally disturbed lands promotes root development, providing organic matter input to a growing microbial biomass. Greater understanding of correlated changes in soil properties during restoration will allow for more holistic assessment of restoration. Recovery of soil structure and ecosystem properties of soil bulk density, belowground plant biomass, and plant species composition were measured across a 36-y chronosequence of restored prairies, a continuously cultivated field and remnant prairie co-located at the Konza Prairie LTER site. Two intact soil cores were removed from each of four plots within each field. Each core was crumbled along planes of weakness until passed through an 8-mm sieve. Roots were hand-picked from each core and bulk density was determined from gravimetric water content.  A subsample of soil was wet-sieved to determine mean weight diameter (MWD) based on the proportional mass of four size fractions. Percent cover of all plants was determined in two 1 m² quadrats in each plot. Changes in ecosystem properties across the chronosequence were analyzed using exponential rise to maximum models and relationships among ecosystem properties were analyzed using Pearson’s correlation procedure. 

Results/Conclusions

Recovery of ecosystem properties was evident across the restoration chronosequence. Aggregate MWD and belowground plant biomass increased with age of restoration until 26 years, with little change after 26 years (P<0.01). Total plant cover increased exponentially with increasing restoration age until 20 years, and then began to decrease (P<0.01). Both grass (P<0.01) and prairie forb (P=0.04) cover increased, with grass cover stabilizing after 7 years and prairie forb cover stabilizing after 26 years. Aggregate MWD was inversely related to bulk density (P<0.01) and positively correlated with belowground plant biomass (P<0.01).  Similar to other studies, results suggest soil structure and root biomass recover on a decadal time scale, coinciding with rapid establishment of perennial grasses and to a lesser extent, prairie forbs.