Observed increase in local cooling effect of deforestation at higher latitudes

Deforestation in mid- to high latitudes is hypothesized to have the potential to cool the Earth's surface by altering biophysical processes. In climate models of continental-scale land clearing, the cooling is triggered by increases in surface albedo and is reinforced by a land albedo-sea ice feedback. This feedback is crucial in the model predictions; without it other biophysical processes may overwhelm the albedo effect to generate warming instead. Ongoing land-use activities, such as land management for climate mitigation, are occurring at local scales (hectares) presumably too small to generate the feedback, and it is not known whether the intrinsic biophysical mechanism on its own can change the surface temperature in a consistent manner. Nor has the effect of deforestation on climate been demonstrated over large areas from direct observations. Here we show that surface air temperature is lower in open land than in nearby forested land. The effect is 0.85 ± 0.44 K (mean ± one standard deviation) northwards of 45° N and 0.21 ± 0.53 K southwards. Below 35° N there is weak evidence that deforestation leads to warming. Results are based on comparisons of temperature at forested eddy covariance towers in the USA and Canada and, as a proxy for small areas of cleared land, nearby surface weather stations. Night-time temperature changes unrelated to changes in surface albedo are an important contributor to the overall cooling effect. The observed latitudinal dependence is consistent with theoretical expectation of changes in energy loss from convection and radiation across latitudes in both the daytime and night-time phase of the diurnal cycle, the latter of which remains uncertain in climate models.     

The Amazon basin in transition

Agricultural expansion and climate variability have become important agents of disturbance in the Amazon basin. Recent studies have demonstrated considerable resilience of Amazonian forests to moderate annual drought, but they also show that interactions between deforestation, fire and drought potentially lead to losses of carbon storage and changes in regional precipitation patterns and river discharge. Although the basin-wide impacts of land use and drought may not yet surpass the magnitude of natural variability of hydrologic and biogeochemical cycles, there are some signs of a transition to a disturbance-dominated regime. These signs include changing energy and water cycles in the southern and eastern portions of the Amazon basin.     

Effect of temperature on brood relocation in Pogonomyrmex salinus (Hymenopteria: Formicidae)

Brood movement in response to temperature by Pogonomyrmex salinus (seed-harvester ant) nurse workers was examined in the sagebrush steppe of southeast Idaho. Shading the mound surface of P. salinus colonies at dawn caused a decrease in mound temperature and led to significantly less brood accumulation near the surface. In a related experiment, a lab colony of P. salinus was offered an artificial thermal gradient during the cool/dark portion of the daily cycle. Nurse workers removed brood from the 21° --22° C range to soils with temperatures between 29° C and 36° C. Daily brood relocation by P. salinus nurse workers is a highly flexible behavior, capable of immediate response to temperature, and does not appear to follow a strict endogenous rhythm.     

IDH1(R132H) mutation increases murine haematopoietic progenitors and alters epigenetics

Mutations in the IDH1 and IDH2 genes encoding isocitrate dehydrogenases are frequently found in human glioblastomas and cytogenetically normal acute myeloid leukaemias (AML). These alterations are gain-of-function mutations in that they drive the synthesis of the ‘oncometabolite’ R-2-hydroxyglutarate (2HG). It remains unclear how IDH1 and IDH2 mutations modify myeloid cell development and promote leukaemogenesis. Here we report the characterization of conditional knock-in (KI) mice in which the most common IDH1 mutation, IDH1(R132H), is inserted into the endogenous murine Idh1 locus and is expressed in all haematopoietic cells (Vav-KI mice) or specifically in cells of the myeloid lineage (LysM-KI mice). These mutants show increased numbers of early haematopoietic progenitors and develop splenomegaly and anaemia with extramedullary haematopoiesis, suggesting a dysfunctional bone marrow niche. Furthermore, LysM-KI cells have hypermethylated histones and changes to DNA methylation similar to those observed in human IDH1- or IDH2-mutant AML. To our knowledge, our study is the first to describe the generation and characterization of conditional IDH1(R132H)-KI mice, and also the first report to demonstrate the induction of a leukaemic DNA methylation signature in a mouse model. Our report thus sheds light on the mechanistic links between IDH1 mutation and human AML.     

Whipworm ( Trichuris dipodomys ) infection in kangaroo rats ( Dipodomys spp.): effects on digestive efficiency

To determine whether infections by whipworms ( Trichuris dipodomys [Nematoda: Trichurata: Trichuridae]) might affect digestive efficiency and therefore energy budgets of two species of kangaroo rats ( Dipodomys microps and Dipodomys ordii [Rodentia: Heteromyidae]), we compared the apparent dry matter digestibility of tree groups of hosts: those naturally infected with whipworms, those naturally uninfected with whipworm, and those originally naturally infected but later deinfected by treatment with the anthelminthic Ivermectin. Prevalence of T. dipodomys was higher in D. microps (53%) than in D. ordii (14%). Apparent dry matter digestibility was reduced by whipworm infection in D. microps but not in D. ordii . Although a statistically significant effect was shown, its small magnitude indicates that whipworm infection is unlikely to have a biologically significant impact on the energy budgets of host kangaroo rats.     

Trichromatic fluorescent vital labeling of bone in the fetal macaque

Summary Mineralizing tissue was labeled in the macaque fetus by administering sequential vital bone labels to the pregnant female. The 3 labels used (DCAF, xylenol orange and minocycline) fluoresce different colors, thereby facilitating identification of discrete lines in the rapidly growing bone and a quantitatige analysis of bone deposition in utero.This work was supported by grants DE02918 and RR00166 from the National Institutes of Health. We thank Dr B.A. Rahn for his helpful suggestions during the initiation of this study.