Carbon and nutrient contents in the miscellaneous fraction of litterfall under different thinning intensities in a semiarid Pinus halepensis afforestation

Abstract: Litterfall evaluation and the effects caused by forestry practices provide valuable information on nutrient-cycle dynamics in managed forests. So far, most of the studies have focused on leaf-fall, omitting other litterfall fractions that can be also relevant for forest and soil modelling in a global change context. With this aim the miscellaneous fraction was quantified in a Pinus halepensis afforestation in the semiarid SE of Spain five years after four different thinning regimes were applied (T75: 75% of mean basal area removed; T60: 60%; T48: 48%; and T0: no thinning). Concentrations and pools (kg ha-1) of carbon and nutrients in the miscellanea fraction were monthly analysed for C and N (June 2010-May 2013), and for P, K, Na, Ca, Mg, Fe, Zn, and Mn (June 2011-May 2013). No differences in concentrations of carbon and nutrients were found among treatments with the exception of N, which showed significant differences between T75 and T60 plots. For pools, a high variability was found over time with maximum C and N pools found during spring, likely reflecting the influence of Thaumetopoea pityocampa attacks. Thinning affected C, N, Mn, and Zn pools in 2011-2012 period, and P, K, Ca, Mg, Mn, Fe, and Zn pools in 2012-2013. Significant differences were mainly found between the most intensive treatment (T75) and unthinned plots (T0). The percentage of annual mean C and nutrient pools in miscellanea showed the importance of its monitoring, with pools that represented from 43.0% to 57.9% of the total litterfall for C (278.81-746.01 kg ha-1 yr-1), N (4.18-10.44 kg ha-1 yr-1), and P (0.37-1.43 kg ha-1 yr-1). Our results stress the high relevance of miscellany monitoring in order to gain a better understanding of nutrient cycles in forest ecosystems.