Forest productivity recovery or collapse? Model-data integration insights on drought-induced tipping points.

More frequent and severe droughts are driving increased forest mortality around the globe. We urgently need to describe and predict how drought affects forest carbon cycling and identify thresholds of environmental stress that trigger ecosystem collapse. Quantifying the effects of drought at an ecosystem level is complex because dynamic climate-plant relationships can cause rapid and/or prolonged shifts in carbon balance. We employ the CARbon DAta MOdel fraMework (CARDAMOM) to investigate legacy effects of drought on forest carbon pools and fluxes. Our Bayesian model-data fusion approach uses tower observed meteorological forcing and carbon fluxes to determine the response and sensitivity of aboveground and belowground ecological processes associated with the 2012-2015 California drought. Our study area is a mid-montane mixed conifer forest in the Southern Sierras. CARDAMOM constrained with gross primary productivity (GPP) estimates covering 2011-2017 show a ~75% reduction in GPP, compared to negligible GPP change when constrained with 2011 only. Precipitation across 2012-2015 was 45% (474 mm) lower than the historical average and drove a cascading depletion in soil moisture and carbon pools (foliar, labile, roots, and litter). Adding 157 mm during an especially stressful year (2014, annual rainfall = 293 mm) led to a smaller depletion of water and carbon pools, steering the ecosystem away from a state of GPP tipping-point collapse to recovery. We present novel process-driven insights that demonstrate the sensitivity of GPP collapse to ecosystem foliar carbon and soil moisture states-showing that the full extent of GPP response takes several years to arise. Thus, long-term changes in soil moisture and carbon pools can provide a mechanistic link between drought and forest mortality. Our study provides an example for how key precipitation threshold ranges can influence forest productivity, making them useful for monitoring and predicting forest mortality events.

Contrasting Regional Carbon Cycle Responses to Seasonal Climate Anomalies Across the East-West Divide of Temperate North America.

Across temperate North America, interannual variability (IAV) in gross primary production (GPP) and net ecosystem exchange (NEE) and their relationship with environmental drivers are poorly understood. Here, we examine IAV in GPP and NEE and their relationship to environmental drivers using two state-of-the-science flux products: NEE constrained by surface and space-based atmospheric CO2 measurements over 2010-2015 and satellite up-scaled GPP from FluxSat over 2001-2017. We show that the arid western half of temperate North America provides a larger contribution to IAV in GPP (104% of east) and NEE (127% of east) than the eastern half, in spite of smaller magnitude of annual mean GPP and NEE. This occurs because anomalies in western ecosystems are temporally coherent across the growing season leading to an amplification of GPP and NEE. In contrast, IAV in GPP and NEE in eastern ecosystems is dominated by seasonal compensation effects, associated with opposite responses to temperature anomalies in spring and summer. Terrestrial biosphere models in the MsTMIP ensemble generally capture these differences between eastern and western temperate North America, although there is considerable spread between models.

Spectrum of ischemic colitis in cocaine users.

Ischemic enterocolitis is a well-recognized entity occurring in cocaine users. Diagnosis is based on the presence of rectal bleeding, abdominal pain, a history of cocaine use, supportive endoscopic and histopathologic findings, and the absence of other etiologic mechanisms of ischemic colitis. In this study, we evaluated endoscopic and histopathologic findings in seven patients with cocaine colitis. Lesions seen by endoscopy, which were restricted to the left colon, included hemorrhagic edematous mucosa, pseudopolyps, and ulcerations. Rectal involvement, not a common feature of ischemic colitis, was seen in five patients. In two patients histologic lesions were classified acute/subacute, and in three patients as subacute/chronic. In the remaining two patients lesions were combined acute/subacute and chronic. The presence of subacute/chronic lesions suggested recurrent ischemic episodes and could reflect repeated use of cocaine. Future studies will be needed to define the long-term clinical and histopathologic significance of these subacute/chronic lesions.

Additive impact of in-hospital cardiac arrest on the functioning of children with heart disease.

OBJECTIVE: This study examined the impact of a sudden cardiac arrest (CA) on the neurodevelopmental and adaptive functioning of young children with congenital heart disease (CHD). METHODOLOGY: Sixteen children with CHD who had sustained an in-hospital CA were compared with a medically similar group of children with CHD who had not incurred a CA. The contribution of CA, disease severity, and family socioeconomic status on the prediction of developmental outcome variables was evaluated. RESULTS: Children in the CA group displayed more impairments in general cognitive, motor, and adaptive behavior functioning as well as greater disease severity as measured by a cumulative medical risk index. With respect to all children in the study, a higher socioeconomic status was related to higher scores on cognitive functioning, lower levels of child maladjustment, and lower levels of stress within the parent-child relationship. Although the occurrence of a CA alone did not contribute to the prediction of outcome measures, a significant interactional effect between CA and cumulative medical risk index was found. Specifically, among children who had incurred a CA, as disease severity increased, decrements in abilities were observed. Few significant correlations between specific CA-related variables (eg, length of CA) and outcome indices were found. CONCLUSIONS: Results from this study indicate that the impact of cardiac arrest on neuropsychological functioning may be mediated by the child's overall disease severity. These findings have implications for the identification of CA survivors at greatest risk for developmental difficulties.

Markedly elevated creatinine phosphokinase, cotton wool spots, and pericarditis in a patient with leptospirosis.

We are reporting a patient with acute leptospirosis whose creatinine phosphokinase was markedly elevated secondary to an associated myositis. In patients presenting with acute hepatitis, an elevated creatinine phosphokinase should suggest the diagnosis of leptospirosis. Our patient's course of illness was made unusual by the appearance of cotton wool spots, previously unreported in leptospirosis as well as by pericarditis in the absence of uremia. This illustrates our ever widening recognition of the clinical manifestations of leptospirosis.