Edaphic controls of soil organic carbon in tropical agricultural landscapes.

Predicting soil organic carbon (SOC) is problematic in tropical soils because mechanisms of SOC (de)stabilization are not resolved. We aimed to identify such storage mechanisms in a tropical soil landscape constrained by 100 years of similar soil inputs and agricultural disturbance under the production of sugarcane, a C4 grass and bioenergy feedstock. We measured soil physicochemical parameters, SOC concentration, and SOC dynamics by soil horizon to one meter to identify soil parameters that can predict SOC outcomes. Applying correlative analyses, linear mixed model (LMM) regression, model selection by AICc, and hierarchical clustering we found that slow moving SOC was related to many soil parameters, while the fastest moving SOC was only related to soil surface charge. Our models explained 78-79%, 51-57%, 7-8% of variance in SOC concentration, slow pool decay, and fast pool decay, respectively. Top SOC predictors were roots, the ratio of organo-complexed iron (Fe) to aluminum (Al), water stable aggregates (WSagg), and cation exchange capacity (CEC). Using hierarchical clustering we also assessed SOC predictors across gradients of depth and rainfall with strong reductions in Roots, SOC, and slow pool decay associated with increasing depth, while increased rainfall was associated with increased Clay and WSagg and reduced CEC in surface soils. Increased negative surface charge, water stable aggregation, organo-Fe complexation, and root inputs were key SOC protection mechanisms despite high soil disturbance. Further development of these relationships is expected to improve understanding of SOC storage mechanisms and outcomes in similar tropical agricultural soils globally.

Hot water pretreatment of lignocellulosic biomass: Modeling the effects of temperature, enzyme and biomass loadings on sugar yield.

Experimental conditions of liquid hot water (LHW) pretreatment were tested for two dedicated energy crops, Napiergrass (Pennisetum purpureum) and Energycane (Saccharum officinarum × Saccharum robustum). Both crops showed differential resistance to temperature during pretreatment and differences in response to biomass and enzyme loadings during subsequent enzymatic hydrolysis. Sugar response surfaces, for both glucose release per g pretreated biomass and as percent yield of glucose present in the initial biomass, were estimated using a General Additive Model (GAM) in R to compare non-linear sugar release as temperature, and biomass and enzyme loadings were manipulated. Compared to Napiergrass, more structural glucose is estimated to be recovered from Energycane per g of pretreated biomass under relatively less harsh pretreatment conditions, however, Napiergrass had the highest measured glucose yield. Sugar degradation products (furfural and hydroxymethylfurfural), pH, and biomass recovery differed significantly between crops across pretreatment temperatures, which could adversely affect downstream biochemical processes.

Intra-abdominal Kaposiform hemangioendothelioma and the benefits of laparoscopic surveillance.

We report a case of a neonate presenting with the rare vascular tumor, Kaposiform hemangioendothelioma. She had a lesion arising from the left ovary with multiple intraperitoneal metastases causing small bowel obstruction. We managed this case with primary surgical resection followed by laparoscopic surveillance of the peritoneal cavity and metastectomy. The child is fit and well and free of tumor after 32 months. Neither this presentation of this tumor nor this management approach has been previously described in the literature.