New procedure for the simulation of belowground competition can improve the performance of forest simulation models

The major part of existing models of belowground competition in mixed forest stands is limited in explaining the spatial distribution of roots as a response to competitive pressure from neighbours and heterogeneity of soil properties. We are presenting a new spatially explicit and multi-layered discrete model of belowground competition, RootInt (ROOTs INTake). It describes spatial distribution of belowground biomass and allows simulation of competition between trees for soil nutrients. The tree-specific area of root zone is calculated on the basis of stem diameter, with site-specific modifiers to account for the effect of soil fertility and moisture. The shape of root zone is dependent on the amount of available nitrogen in the current cell, distance between this cell and the stem base, and the mass of roots of other plants. RootInt was incorporated into ecosystem model EFIMOD to refine the existing description of belowground competition in forest stands with multiple cohorts and tree species. The results of simulation showed that bringing more complexity into structure of stand (including initial spatial locations of trees, species composition and age structure, vertical structure of canopy) resulted in higher spatial variation in competition intensity, as well as in higher rates of resource uptake. This indicates that stands with complex canopy structure had high plasticity in their root systems and were adapted to intensive competition for soil resources.201

Maternal and neonatal outcomes after caesarean delivery in the African Surgical Outcomes Study: a 7-day prospective observational cohort study.

BACKGROUND: Maternal and neonatal mortality is high in Africa, but few large, prospective studies have been done to investigate the risk factors associated with these poor maternal and neonatal outcomes. METHODS: A 7-day, international, prospective, observational cohort study was done in patients having caesarean delivery in 183 hospitals across 22 countries in Africa. The inclusion criteria were all consecutive patients (aged ≥18 years) admitted to participating centres having elective and non-elective caesarean delivery during the 7-day study cohort period. To ensure a representative sample, each hospital had to provide data for 90% of the eligible patients during the recruitment week. The primary outcome was in-hospital maternal mortality and complications, which were assessed by local investigators. The study was registered on the South African National Health Research Database, number KZ_2015RP7_22, and on ClinicalTrials.gov, number NCT03044899. FINDINGS: Between February, 2016, and May, 2016, 3792 patients were recruited from hospitals across Africa. 3685 were included in the postoperative complications analysis (107 missing data) and 3684 were included in the maternal mortality analysis (108 missing data). These hospitals had a combined number of specialist surgeons, obstetricians, and anaesthetists totalling 0·7 per 100 000 population (IQR 0·2-2·0). Maternal mortality was 20 (0·5%) of 3684 patients (95% CI 0·3-0·8). Complications occurred in 633 (17·4%) of 3636 mothers (16·2-18·6), which were predominantly severe intraoperative and postoperative bleeding (136 [3·8%] of 3612 mothers). Maternal mortality was independently associated with a preoperative presentation of placenta praevia, placental abruption, ruptured uterus, antepartum haemorrhage (odds ratio 4·47 [95% CI 1·46-13·65]), and perioperative severe obstetric haemorrhage (5·87 [1·99-17·34]) or anaesthesia complications (11·47 (1·20-109·20]). Neonatal mortality was 153 (4·4%) of 3506 infants (95% CI 3·7-5·0). INTERPRETATION: Maternal mortality after caesarean delivery in Africa is 50 times higher than that of high-income countries and is driven by peripartum haemorrhage and anaesthesia complications. Neonatal mortality is double the global average. Early identification and appropriate management of mothers at risk of peripartum haemorrhage might improve maternal and neonatal outcomes in Africa. FUNDING: Medical Research Council of South Africa.Medical Research Council of South Africa