The structural and nutrient chemistry during early-stage decomposition and desiccation of cacti in the Sonoran Desert

Despite the abundance of cacti in the Sonoran Desert, most research focuses on population dynamics and physiology. Relatively little is known about their decomposition dynamics. A better understanding of cactus decomposition is important, considering the number of threatened and endangered cactus species. We measured mass, water, nutrient, and structural chemistry over one year of decomposition of two common cactus species, Opuntia chlorotica and Cylindropuntia acanthocarpa, in the Sonoran Desert of Arizona, U.S.A. Our results demonstrate the contribution of cactus decomposition to carbon and nutrient recycling, with comparable dynamics to woody and herbaceous leaf litter for most elements. We enumerate, however, the particularly important role in calcium dynamics. Despite initial differences, both cacti released nutrients at a statistically equivalent rate, though with altered timing due to temporary mass gain in cholla. The resources released from decaying cacti have a modest influence on underlying soil CO₂ flux, secondary to a dominant influence of soil microclimate. Our data provide a baseline for understanding the decay dynamics of two common cactus species and suggest that, while there is still a lack of information pertaining to cactus decomposition, the similarities with leaf litter will aid our predictions of the consequences of future cactus population changes.