Impacts of selective logging on insectivorous birds in Borneo: The importance of trophic position, body size and foraging height

Habitat destruction and degradation are major drivers of biodiversity loss and attention is increasingly focused on how different traits of species affect their vulnerability. Dietary traits are critical in this respect, and are typically examined by assigning species to different feeding and foraging guilds. However, such guilds may mask large variation in species' trophic interactions, limiting our understanding of species' responses. Here we use stable isotopes to quantify trophic positions within a Family of insectivorous understory birds, the Timaliidae (babblers), within Bornean rainforests. We then relate changes in species' abundances following intensive selective logging of forest to their trophic positions, body sizes and foraging heights. We found that trophic positions within this single feeding guild spanned more than an entire trophic level. Moreover, changes in abundance following logging were significantly and independently related to mean trophic position in primary forest, body size and foraging height: large ground-feeding species occupying high trophic positions were more adversely affected than small understory-feeders with lower trophic positions. These three variables together explained 81% of the variance in species' responses to logging. The single most important predictor, however, was a species' mean trophic position. Species recorded in both habitats also had significantly higher trophic positions in logged forest. These data provide critical new understanding of species' responses to disturbance. They also indicate previously unrecognised functional changes to species assemblages following logging, highlighting the importance of numerical assessments of trophic position within individual feeding guilds

The impact of the Cretaceous–Paleogene (K–Pg) mass extinction event on the global sulfur cycle: Evidence from Seymour Island, Antarctica

The Cretaceous–Paleogene (K–Pg) mass extinction event 66 million years ago led to large changes to the global carbon cycle, primarily via a decrease in primary or export productivity of the oceans. However, the effects of this event and longer-term environmental changes during the Late Cretaceous on the global sulfur cycle are not well understood. We report new carbonate associated sulfate (CAS) sulfur isotope data derived from marine macrofossil shell material from a highly expanded high latitude Maastrichtian to Danian (69–65.5 Ma) succession located on Seymour Island, Antarctica. These data represent the highest resolution seawater sulfate record ever generated for this time interval, and are broadly in agreement with previous low-resolution estimates for the latest Cretaceous and Paleocene. A vigorous assessment of CAS preservation using sulfate oxygen, carbonate carbon and oxygen isotopes and trace element data, suggests factors affecting preservation of primary seawater CAS isotopes in ancient biogenic samples are complex, and not necessarily linked to the preservation of original carbonate mineralogy or chemistry. Primary data indicate a generally stable sulfur cycle in the early-mid Maastrichtian (69 Ma), with some fluctuations that could be related to increased pyrite burial during the ‘mid-Maastrichtian Event’. This is followed by an enigmatic +4‰ increase in δ³⁴SCAS during the late Maastrichtian (68–66 Ma), culminating in a peak in values in the immediate aftermath of the K–Pg extinction which may be related to temporary development of oceanic anoxia in the aftermath of the Chicxulub bolide impact. There is no evidence of the direct influence of Deccan volcanism on the seawater sulfate isotopic record during the late Maastrichtian, nor of a direct influence by the Chicxulub impact itself. During the early Paleocene (magnetochron C29R) a prominent negative excursion in seawater δ³⁴S of 3–4‰ suggests that a global decline in organic carbon burial related to collapse in export productivity, also impacted the sulfur cycle via a significant drop in pyrite burial. Box modelling suggests that to achieve an excursion of this magnitude, pyrite burial must be reduced by >15%, with a possible role for a short term increase in global weathering rates. Recovery of the sulfur cycle to pre-extinction values occurs at the same time (∼320 kyrs) as initial carbon cycle recovery globally. These recoveries are also contemporaneous with an initial increase in local alpha diversity of marine macrofossil faunas, suggesting biosphere-geosphere links during recovery from the mass extinction. Modelling further indicates that concentrations of sulfate in the oceans must have been 2 mM, lower than previous estimates for the Late Cretaceous and Paleocene and an order of magnitude lower than today

Numerical Simulation of Spring Hydrograph Recession Curves for East Yorkshire Chalk Aquifer, UK

The Cretaceous Chalk aquifer is the most important in the UK for the provision of water to public supply and agriculture. The Chalk has both matrix and fracture porosity and is thus best considered as a dual porosity aquifer system. Although the matrix porosity is large, typically around 0.35 in the study area of East Yorkshire, UK (ESI, 2010), pore diameters are typically very small, and the water contained in them is virtually immobile. The high permeability fracture network is responsible for the ability of water to drain; spatial variations in fracture network properties mean conventional approaches to aquifer characterization such as borehole pumping tests are of limited utility. Hence this study attempts to better understand the flow system and characterise aquifer properties from the recession response seen at springs during the spring/summer period when recharge is minimal. This approach has the advantage that spring hydrographs represent the sum of the response from entire catchments. This paper reports numerical modeling for simulating aquifer and spring responses during hydrological recession. Firstly, available geological and hydrogeological information for the study area was used to develop hydrogeological conceptual models. Four different numerical models have been constructed representing four possible scenarios that could represent the aquifer in the selected area. These are: single reservoir aquifer, double reservoir aquifer, single reservoir aquifer with highly permeable vertical zone intersecting the spring location and single reservoir aquifer containing tunnel shaped highly permeable zone at the spring elevation respectively. The sensitivity of spring recession response to various external and internal parameter values was investigated, to understand relations between spring recession, hydrological inputs (recharge) and aquifer structure. Spring hydrographs from the real aquifer were compared with the hydrographs generated from models, in order to estimate aquifer properties. The work aims to identify the utility of spring hydrographs in eliciting aquifer permeability structure, as well as identifying the conceptual scenario which best represents the Chalk Aquifer in East Yorkshire, UK

δ34SCAS and δ18OCAS records during the Frasnian-Famennian (Late Devonian) transition and their bearing on mass extinction models

Many proposed extinction mechanisms for the Late Devonian (Frasnian–Famennian boundary — FFB) mass extinction event include the spread of anoxia in bottom waters during the two Kellwasser anoxic events, which have in turn been linked to changes in continental weathering, volcanic/hydrothermal fluxes, sea-level and climate change. Although there is strong evidence for bottom water anoxia in epicontinental seas at tropical/equatorial palaeolatitudes, the global extent of these changes is poorly understood, largely due to the lack of an oceanic and high-latitude record. In this study, marine δ34Ssulphate and δ18Osulphate records, derived from the analysis of carbonate-associated sulphate (CAS), were constructed from FFB sections in Belgium and Poland in order to examine the effect of the postulated changes in ocean redox conditions on the global sulphur cycle. The results reveal no overall changes in seawater δ34Ssulphate and δ18Osulphate over the FFB interval suggesting that any changes in sulphur cycling, namely relating to rates of pyrite burial and weathering, were not significant on a global scale. This supports the idea that the Kellwasser events were not oceanic phenomena and that they were restricted to epicontinental seas at low latitudes. The exception to the stability of the FFB δ34Ssulphate record is a brief negative excursion during the mass extinction interval in the linguiformis Zone, albeit based on one datapoint at this level in two different sections. This may be attributable to short, sharp marine regression and an increased flux of light sulphur from weathered pyrite

Deep groundwater flow and geochemical processes in limestone aquifers: evidence from thermal waters in Derbyshire, England, UK

Thermal waters potentially provide information on geochemical processes acting deep within aquifers. New isotopic data on groundwater sulphate, inorganic carbon and strontium in thermal and non-thermal waters of a major limestone aquifer system in Derbyshire, England, UK, are used to constrain sulphate sources and groundwater evolution. Shallow groundwaters gain sulphate from oxidation of sulphide minerals and have relatively 13C-depleted dissolved inorganic carbon (DIC). Thermal waters have relatively high Sr/Ca and more 13C-enriched DIC as a result of increased water–rock interaction. In other respects, the thermal waters define two distinct groups. Thermal waters rising at Buxton have higher Mg, Mn and 87Sr/86Sr and lower Ca and SO4, indicating flow from deep sandstone aquifers via a high permeability pathway in the limestone. By contrast, Matlock-type waters (97% of the thermal flux) have elevated sulphate concentrations derived from interaction with buried evaporites, with no chemical evidence for flow below the limestone. About 5% of the limestone area's groundwater flows to the Matlock group springs via deep regional flow and the remainder flows via local shallow paths to many non-thermal springs. Gypsum dissolution has produced significant tertiary porosity and tertiary permeability in the carbonate aquifer and this is an essential precursor to the development of karstic drainage