Decoupling of soil nutrient cycles as a function of aridity in global drylands

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. We find a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems

Infective Endocarditis After Transcatheter Versus Surgical Aortic Valve Replacement

Abstract Background Scarce data are available comparing infective endocarditis (IE) following surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR). This study aimed to compare the clinical presentation, microbiological profile, management, and outcomes of IE after SAVR versus TAVR. Methods Data were collected from the “Infectious Endocarditis after TAVR International” (enrollment from 2005 to 2020) and the “International Collaboration on Endocarditis” (enrollment from 2000 to 2012) registries. Only patients with an IE affecting the aortic valve prosthesis were included. A 1:1 paired matching approach was used to compare patients with TAVR and SAVR. Results A total of 1688 patients were included. Of them, 602 (35.7%) had a surgical bioprosthesis (SB), 666 (39.5%) a mechanical prosthesis, 70 (4.2%) a homograft, and 350 (20.7%) a transcatheter heart valve. In the SAVR versus TAVR matched population, the rate of new moderate or severe aortic regurgitation was higher in the SB group (43.4% vs 13.5%; P < .001), and fewer vegetations were diagnosed in the SB group (62.5% vs 82%; P < .001). Patients with an SB had a higher rate of perivalvular extension (47.9% vs 27%; P < .001) and Staphylococcus aureus was less common in this group (13.4% vs 22%; P = .033). Despite a higher rate of surgery in patients with SB (44.4% vs 27.3%; P < .001), 1-year mortality was similar (SB: 46.5%; TAVR: 44.8%; log-rank P = .697). Conclusions Clinical presentation, type of causative microorganism, and treatment differed between patients with an IE located on SB compared with TAVR. Despite these differences, both groups exhibited high and similar mortality at 1-year follow-up