Understanding plant residue decomposition in shrubland ecosystem

Litter decomposition is a key component in ecosystem C and nutrient cycling. Shrubland litter decomposition is not well understood, even though shrublands cover a significant proportion of earth surface. This project aims to investigate the decomposition of shrubland plant residue (Cistus monspeliensis L.). The first and second experimental chapters of this thesis present the data about root chemistry, C and N mineralisation from the decomposing roots. Root tissue chemistry varies significantly with age, younger roots consist of higher relative amounts of N, P, K, soluble compounds, conversely Ca, hemicellulose, cellulose concentrations are higher in older roots. Faster short-term C, and N mineralisation rates were observed in senescing younger roots compared to the older roots under our experimental conditions. The third experimental chapter is about leaf litter decomposition study using litter bag technique. Accumulated mass loss from the decomposing leaf litter is a biphasic process where initial rapid mass loss followed by relatively slower phase. Among the various leaf litter decomposition parameters lignin: N best explained the accumulated mass loss. Fourth experimental chapter is an attempt to understand the 14C mineralisation process from decomposing soluble and insoluble components of above and below ground plant parts. Soluble components have shown faster 14C mineralisation compared to the insoluble fractions of above (stem and leaf) and belowground (roots) plant components. Belowground plant components have shown a distinctive 14C mineralisation pattern with more % 14C entering in to microbial biomass pool compared to the aboveground components which will have consequences on whole ecosystem C cycle. Results from final experimental chapter indicate that C sourced by hyphal biomass reside longer duration even after death thereby contribute significant amounts of C to the belowground. However, further long-term studies that includes multi plant species under filed conditions are needed before these results extrapolate to the shrubland ecosystem