Geological atlas of western and central Europe

We upscaled FLUXNET observations of carbon dioxide, water, and energy fluxes to the global scale using the machine learning technique, model tree ensembles (MTE). We trained MTE to predict site-level gross primary productivity (GPP), terrestrial ecosystem respiration (TER), net ecosystem exchange (NEE), latent energy (LE), and sensible heat (H) based on remote sensing indices, climate and meteorological data, and information on land use. We applied the trained MTEs to generate global flux fields at a 0.5 degrees x 0.5 degrees spatial resolution and a monthly temporal resolution from 1982 to 2008. Cross-validation analyses revealed good performance of MTE in predicting among-site flux variability with modeling efficiencies (MEf) between 0.64 and 0.84, except for NEE (MEf = 0.32). Performance was also good for predicting seasonal patterns (MEf between 0.84 and 0.89, except for NEE (0.64)). By comparison, predictions of monthly anomalies were not as strong (MEf between 0.29 and 0.52). Improved accounting of disturbance and lagged environmental effects, along with improved characterization of errors in the training data set, would contribute most to further reducing uncertainties. Our global estimates of LE (158 +/- 7 J x 10(18) yr(-1)), H (164 +/- 15 J x 10(18) yr(-1)), and GPP (119 +/- 6 Pg C yr(-1)) were similar to independent estimates. Our global TER estimate (96 +/- 6 Pg C yr(-1)) was likely underestimated by 5-10%. Hot spot regions of interannual variability in carbon fluxes occurred in semiarid to semihumid regions and were controlled by moisture supply. Overall, GPP was more important to interannual variability in NEE than TER. Our empirically derived fluxes may be used for calibration and evaluation of land surface process models and for exploratory and diagnostic assessments of the biosphere.

Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations

Cretaceous eustasy revisited

The aftermath of the great end-Permian period mass extinction 252 Myr ago shows how life can recover from the loss of >90% species globally. The crisis was triggered by a number of physical environmental shocks (global warming, acid rain, ocean acidification and ocean anoxia), and some of these were repeated over the next 5-6 Myr. Ammonoids and some other groups diversified rapidly, within 1-3 Myr, but extinctions continued through the Early Triassic period. Triassic ecosystems were rebuilt stepwise from low to high trophic levels through the Early to Middle Triassic, and a stable, complex ecosystem did not re-emerge until the beginning of the Middle Triassic, 8-9 Myr after the crisis. A positive aspect of the recovery was the emergence of entirely new groups, such as marine reptiles and decapod crustaceans, as well as new tetrapods on land, including — eventually — dinosaurs. The stepwise recovery of life in the Triassic could have been delayed either by biotic drivers (complex multispecies interactions) or physical perturbations, or a combination of both. This is an example of the wider debate about the relative roles of intrinsic and extrinsic drivers of large-scale evolution. from a much more devastated planet and biota than the others. With only some 10% of species surviving, the EPME was much harsher than the other mass extinctions, during which global species diversity reduced to only about 50% of the pre-extinction total 1,2,24-26 . This means that the Triassic recovery has two profound implications: first, it may show qualitative, as well as quantitative, differences from the other post-extinction recoveries; and, second, it can act as an exemplar of what to expect, at its most extreme, when global biodiversity is pushed to the brink. There are obvious implications for current concerns about biodiversity loss and recovery resulting from human impacts 27,28 . In the past ten years, attention has focused on the sedimentary successions in south China. These are enormously laterally extensive, with some formations extending more than 2,000 km from the Zhejiang to Yunnan provinces. The huge exposures, length of the sections and improving dating open up the opportunity to explore physical environmental and biotic changes through the extinction and recovery times in varied marine habitats, and compare these with patterns elsewhere in the world (Fig. 1). A fine- scale, forensic analysis of this extraordinary time in Earth's history now becomes possible. The end-Permian mass extinction The EPME killed 80-96% of marine animal species and 70% of terrestrial vertebrate species

The timing and pattern of biotic recovery following the end-Permian mass extinction

It remains unclear whether biodiversity buffers ecosystems against climate extremes, which are becoming increasingly frequent worldwide. Early results suggested that the ecosystem productivity of diverse grassland plant communities was more resistant, changing less during drought, and more resilient, recovering more quickly after drought, than that of depauperate communities. However, subsequent experimental tests produced mixed results. Here we use data from 46 experiments that manipulated grassland plant diversity to test whether biodiversity provides resistance during and resilience after climate events. We show that biodiversity increased ecosystem resistance for a broad range of climate events, including wet or dry, moderate or extreme, and brief or prolonged events. Across all studies and climate events, the productivity of low-diversity communities with one or two species changed by approximately 50% during climate events, whereas that of high-diversity communities with 16–32 species was more resistant, changing by only approximately 25%. By a year after each climate event, ecosystem productivity had often fully recovered, or overshot, normal levels of productivity in both high- and low-diversity communities, leading to no detectable dependence of ecosystem resilience on biodiversity. Our results suggest that biodiversity mainly stabilizes ecosystem productivity, and productivity-dependent ecosystem services, by increasing resistance to climate events. Anthropogenic environmental changes that drive biodiversity loss thus seem likely to decrease ecosystem stability, and restoration of biodiversity to increase it, mainly by changing the resistance of ecosystem productivity to climate events.

Biodiversity increases the resistance of ecosystem productivity to climate extremes

Chapter 27 – Cretaceous

Extreme hydrologic events such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRMsoft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-flux exhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Nino-Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere-oceanic circulation driven by solar activity.

https://www.pnas.org/content/pnas/114/5/852.full.pdf

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Astronomical tuning of the end-Permian extinction and the Early Triassic Epoch of South China and Germany

Pacing of the Toarcian Oceanic Anoxic Event (Early Jurassic) from astronomical correlation of marine sections

A high-resolution grayscale series of the pelagic Fucoid Marls (Piobbico core, central Italy) shows strong, pervasive lithological rhythms throughout the Aptian interval. A hierarchy of centimeter- to meter-scale cycles characterizes the rhythms; when calibrating ~1 m cycles to Earth’s 405 k.y. orbital eccentricity cycle, these rhythms correspond to the periods of the eccentricity, obliquity, and precession index. Tuning to orbital eccentricity cycles provides a high-resolution time scale for the Aptian. Correlation to the Cismon core (northern Italy) extends the tuning to the Aptian-Barremian boundary. The tuning indicates a minimum duration of 13.42 m.y. for the Aptian Stage, where previous estimates range from 6.4 to 13.8 m.y. The combined Aptian–Albian astronomical tuning of the entire 77-m-long Piobbico core (and part of the Cismon core) provides a 25.85-m.y.-long astronomically calibrated time scale for Earth history.

Chunju Huang

Papers

Chapter 27 – Cretaceous

Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

Astronomical tuning of the end-Permian extinction and the Early Triassic Epoch of South China and Germany

Pacing of the Toarcian Oceanic Anoxic Event (Early Jurassic) from astronomical correlation of marine sections

Astronomical tuning of the Aptian Stage from Italian reference sections