Can we characterise ‘openness’ in the Holocene palaeoenvironmental record? Modern analogue studies of insect faunas and pollen spectra from Dunham Massey deer park and Epping Forest, England

This paper examines the degree to which tree-associated Coleoptera (beetles) and pollen could be used to predict the degree of ‘openness’ in woodland. The results from two modern insect and pollen analogue studies from ponds at Dunham Massey, Cheshire and Epping Forest, Greater London are presented. We explore the reliability of modern pollen rain and sub-fossil beetle assemblages to represent varying degrees of canopy cover for up to 1000m from a sampling site. Modern woodland canopy structure around the study sites has been assessed using GIS-based mapping at increasing radial distances as an independent check on the modern insect and pollen data sets. These preliminary results suggest that it is possible to use tree-associated Coleoptera to assess the degree of local vegetation openness. Additionally, it appears that insect remains may indicate the relative intensity of land use by grazing animals. Our results also suggest most insects are collected from within a 100m to 200m radius of the sampling site. The pollen results suggest that local vegetation and density of woodland in the immediate area of the sampling site can have a strong role in determining the pollen signal.

Constraining the age of Lateglacial and early Holocene pollen zones and tephra horizons in southern Sweden with Bayesian probability methods

The sediment sequence from Hasseldala port in southeastern Sweden provides a unique Lateglacial/early Holocene record that contains five different tephra layers. Three of these have been geochemically identified as the Borrobol Tephra, the Hasseldalen Tephra and the 10-ka Askja Tephra. Twenty-eight high-resolution C-14 measurements have been obtained and three different age models based on Bayesian statistics are employed to provide age estimates for the five different tephra layers. The chrono- and pollen stratigraphic framework supports the stratigraphic position of the Borrobol Tephra as found in Sweden at the very end of the Older Dryas pollen zone and provides the first age estimates for the Askja and Hasseldalen tephras. Our results, however, highlight the limitations that arise in attempting to establish a robust, chronologically independent lacustrine sequence that can be correlated in great detail to ice core or marine records. Radiocarbon samples are prone to error and sedimentation rates in lake basins may vary considerably due to a number of factors. Any type of valid and 'realistic' age model, therefore, has to take these limitations into account and needs to include this information in its prior assumptions. As a result, the age ranges for the specific horizons at Hasseldala port are large and calendar year estimates differ according to the assumptions of the age-model. Not only do these results provide a cautionary note for overdependence on one age-model for the derivation of age estimates for specific horizons, but they also demonstrate that precise correlations to other palaeoarchives to detect leads or lags is problematic. Given the uncertainties associated with establishing age-depth models for sedimentary sequences spanning the Lateglacial period, however, this exercise employing Bayesian probability methods represents the best possible approach and provides the most statistically significant age estimates for the pollen zone boundaries and tephra horizons. Copyright (C) 2006 John Wiley & Sons, Ltd.

The vegetation and climate history of the last glacial cycle in a new pollen record from Lake Fimon (southern Alpine foreland, N-Italy)

The sediments of Like Fimon N Italy contain the first continuous archive of the Late Pleistocene environmental and climate history of the southern Alpine foreland We present here the detailed palynological record of the interval between Termination II and the List Glacial Maximum The age-depth model is obtained by radiocarbon dating in the uppermost part of the record Downward we con elated major forest expansion and contraction events to isotopic events in the Greenland Ice core records via a stepping-stone approach involving intermediate correlation to isotopic events dated by TIMS U/Th in Alpine and Apennine stalagmites and to pollen records from mime cores of the Iberian margin Modelled ages obtained by Bayesian analysis of deposition are thoroughly consistent with actual ages with maximum offset of +/- 1700 years Sharp expansion of broad-leaved temperate forest and of sudden water table rise mark the onset of the Last Interglacial after a treeless steppe phase at the end of penultimate glaciation This event is actually a two-step process which matches the two step rise observed in the isotopic record of the nearby Antro del Corchia stalagmite respectively dated to 132 5 +/- 2 5 and 129 +/- 1 5 ka At the interglacial decline mixed oak forests were replaced by oceanic mixed forests the latter persisting further for 7 ka till the end of the Eemian succession Warm-temperate woody species are still abundant at the Eemian end corroborating a steep gradient between central Europe and the Alpine divide at the inception of the last glacial After a stadial phase marked by moderate forest decline a new expansion of warm broad leaved forests interrupted by minor events and followed by mixed oceanic forests can be identified with the north-alpine Saint Germain I The spread of beech during the oceanic phase is a valuable circumalpine marker The subsequent stadial-interstadial succession lacking the telocratic oceanic phase is also consistent with the evidence at the north alpine foreland The Middle Wurmian (full glacial) is marked by persistence of mixed forests dominated by conifers but with significant lime and other broad leaved species A major Arboreal Pollen decrease is observed at modelled age of 38 7 +/- 0 5 ka (larch expansion and last occurrence of lime) which his been related to Heinrich Event 4 The evidence of afforestation persisting south of the Alps throughout most of MIS 3 contrasts with a boreal and continental landscape known for the northern alpine foreland pointing to a sharp rainfall boundary at the Alpine divide and to southern air circulation This is in agreement with the Alpine paleoglaciological record and is supported by the pressure and rainfall patterns designed by mesoscale paleoclimate simulations Strenghtening the continental high pressure during the full glacial triggered cyclogenesis in the middle latitude eastern Europe and orographic rainfall in the eastern Alps and the Balkanic mountains thus allowing forests development at current sea level altitudes (C) 2010 Elsevier Ltd All rights reserved

Response of red blood cell folate to intervention: implications for folate recommendations for the prevention of neural tube defects

Committees worldwide have set almost identical folate recommendations for the prevention of the first occurrence of neural tube defects (NTDs). We evaluate these recommendations by reviewing the results of intervention studies that examined the response of red blood cell folate to altered folate intake. Three options are suggested to achieve the extra 400 mu g folic acid/d being recommended by the official committees: increased intake of folate-rich foods, dietary folic acid supplementation, and folic acid fortification of food. A significant increase in foods naturally rich in folates was shown to be a relatively ineffective means of increasing red blood cell folate status in women compared with equivalent intakes of folic acid-fortified food, presumably because the synthetic form of the vitamin is more stable and more bioavailable. Although folic acid supplements are highly effective in optimizing folate status, supplementation is not an effective strategy for the primary prevention of NTDs because of poor compliance. Thus, food fortification is seen by many as the only option likely to succeed. Mandatory folic acid fortification of grain products was introduced recently in the United States at a level projected to provide an additional mean intake of 100 mu g folic acid/d, but some feel that this policy does not go far enough. A recent clinical trial predicted that the additional intake of folic acid in the United States will reduce NTDs by >20%, whereas 200 mu g/d would be highly protective and is the dose also shown to be optimal in lowering plasma homocysteine, with possible benefits in preventing cardiovascular disease. Thus, an amount lower than the current target of an extra 400 mu g/d may be sufficient to increase red blood cell folate to concentrations associated with the lowest risk of NTDs, but further investigation is warranted to establish the optimal amount.

Fortification with low amounts of folic acid makes a significant difference in folate status in young women: implications for the prevention of neural tube defects

Background: Mandatory fortification of grain products with folic acid was introduced recently in the United States, a policy expected to result in a mean additional intake of 100 mu g/d. One way of predicting the effectiveness of this measure is to determine the effect of removing a similar amount of folic acid as fortified food from the diets of young women who had been electively exposed to chronic fortification.

Objective: The objective was to examine the effect on folate status of foods fortified with low amounts of folic acid.

Design: We investigated the changes in dietary intakes and in red blood cell and serum concentrations of folate in response to removing folic acid-fortified foods for 12 wk from the diets of women who reportedly consumed such foods at least once weekly (consumers).

Results: Consumers (n = 21) had higher total folate intakes (P = 0.002) and red blood cell folate concentrations (P = 0.023) than nonconsumers (women who consumed folic acid-fortified foods less than once weekly; n = 30). Of greater interest, a 12-wk intervention involving the exclusion of these foods resulted in a decrease in folate intake of 78 +/- 56 mu g/d (P < 0.001), which was reflected in a significant reduction in red blood cell folate concentrations (P < 0.05).

Conclusions: Cessation of eating folic acid-fortified foods resulted in removing 78 mu g folic acid/d from the diet. Over 12 wk this resulted in a lowering of red blood cell folate concentrations by 111 nmol/L (49 mu g/L). This magnitude of change in folate status in women can be anticipated as a result of the new US fortification legislation and is predicted to have a significant, although not optimal, effect in preventing neural tube defects.

Effect of increasing dietary folate on red-cell folate: Implications for prevention of neural tube defects

Background Recommendations by the UK Department of Health suggest that protection from neural tube defects (NTD) can be achieved through intakes of an extra 400 mu g daily of folate/folic acid as natural food, foods fortified with folic acid, or supplements. The assumption is that all three routes of intervention would have equal effects on folate status.

Methods We assessed the effectiveness of these suggested routes of intervention in optimising folate status. 62 women were recruited from the University staff and students to take part in a 3-month intervention study. Participants were randomly assigned to one of the following five groups: folic acid supplement (400 mu g/day; I); folic-acid-fortified foods (an additional 400 mu g/day; II); dietary folate (an additional 400 mu g/day; III); dietary advice (IV), and control (V). Responses to intervention were assessed as changes in red-cell folate between preintervention and postintervention values.

Findings 41 women completed the intervention study. Red-cell folate concentrations increased significantly over the 3 months in the groups taking folic acid supplements (group I) or food fortified with folic acid (group II) only (p<0.01 for both groups). By contrast, although aggressive intervention with dietary folate (group III) or dietary advice (group IV) significantly increased intake of food folate (p<0.001 and p<0.05, respectively), there was no significant change in folate status.

Interpretation We have shown that compared with supplements and fortified food, consumption of extra folate as natural food folate is relatively ineffective at increasing folate status. We believe that advice to women to consume folate-rich foods as a means to optimise folate status is misleading.