Evolution of Plant Biopolymer Chemistry of Above and Below Ground Input in a ýThorn Woodland Chronosequence

Encroachment of thorn woodlands into the grasslands of South Texas over the last 150-ýý200 years has resulted in greater above- and belowground biomass as well as greater ýoverall soil organic carbon (SOC) stocks. With the advancing age of woody clusters ýfrom initial mesquite occupation a variety of shrub and tree species become established in ýthe under story and often overtake the initial mesquite. This shift within clusters has ýimplications for the mass as well as chemistry of both above ground and below ground ýplant input to soils. Because this ecosystem shift results in an increased apportionment of ýcarbon to non aggregated, fast cycling SOC, the shifting biopolymer chemistry of plant ýinput may dramatically impact the microbial recalcitrance and residence time of SOC. ýWe document the specific plant contributors to a chronosequence (~90 years) of woody ýcluster encroachment and relate this to measured changes in litter chemistry, overall leaf ýand woody tissue input, and projected shifts in the chemistry to the soil as a result. ý