Palynological perspectives on vegetation survey: a critical step for model-based reconstruction of Quaternary land cover

Abstract

Pollen dispersal and deposition models Pollen surface sample PrenticeeSugita model of pollen dispersal and deposition Remote sensing data Sutton model Vegetation data processing a b s t r a c t 1. Quantitative reconstruction of past vegetation distribution and abundance from sedimentary pollen records provides an important baseline for understanding long term ecosystem dynamics and for the calibration of earth system process models such as regional-scale climate models, widely used to predict future environmental change. Most current approaches assume that the amount of pollen produced by each vegetation type, usually expressed as a relative pollen productivity term, is constant in space and time.2. Estimates of relative pollen productivity can be extracted from extended R-value analysis (Parsons and Prentice, 1981) using comparisons between pollen assemblages deposited into sedimentary contexts, such as moss polsters, and measurements of the present day vegetation cover around the sampled location. Vegetation survey method has been shown to have a profound effect on estimates of model parameters (Bunting and Hjelle, 2010), therefore a standard method is an essential pre-requisite for testing some of the key assumptions of pollen-based reconstruction of past vegetation; such as the assumption that relative pollen productivity is effectively constant in space and time within a region or biome.3. This paper systematically reviews the assumptions and methodology underlying current models of pollen dispersal and deposition, and thereby identifies the key characteristics of an effective vegetation survey method for estimating relative pollen productivity in a range of landscape contexts.4. It then presents the methodology used in a current research project, developed during a practitioner workshop. The method selected is pragmatic, designed to be replicable by different research groups, usable in a wide range of habitats, and requiring minimum effort to collect adequate data for model calibration rather than representing some ideal or required approach. Using this common methodology will allow project members to collect multiple measurements of relative pollen productivity for major plant taxa from several northern European locations in order to test the assumption of uniformity of these values within the climatic range of the main taxa recorded in pollen records from the region.

Replicability of data collected for empirical estimation of relative pollen productivity

“…The vegetation in the area beyond 100 m (zone C) is quantified from existing data sources, such as published maps, aerial photography or remotely sensed data; the distribution of communities is digitised, then community composition defined where possible by extrapolation from the mapped zone B communities, by additional field recording, or from existing studies or databases. Bunting et al (2013) present an empirical test of the effects of different recording methods within zone A, which confirms that the array chosen produces statistically identical results to a more time-consuming complete survey using the 'ring method' (e.g. Broström et al, 2004), but did not investigate replicability of zones B and C. This paper presents a smallscale investigation of the possible effects of the timing of fieldwork on the datasets generated for zones A and B.…”

“…In the proposed standard protocol, a single moss polster is collected and defines the central point of the vegetation survey (Bunting et al, 2013).…”

“…To allow the assumption of constant RPP to be tested, Bunting et al (2013) presented a vegetation survey and moss collection protocol for RPP analysis which was developed through a practitioner workshop, and represented an agreed compromise between existing…”

California's Historic Legacy For Landscape Change, the Wieslander Vegetation Type Maps

“…Basal area rather than abundance was used to infer community level dominance, facilitating comparisons with historic changes in the abundances of these genera based on the palynological record. Pollen data at least coarsely reflect tree basal area on the landscape due to size-dependence of fecundity, and should track basal area better than stem density, which may be driven by small nonreproductive individuals (57,58). To investigate patterns of oak and pine abundance in relation to CWD, we regressed the ratio of oak to pine basal area with CWD from 10 arc-minute grids within each time period and used ANCOVA to determine if the relationship varied across time periods.…”

Pollen signals of ground flora in managed woodlands

“…grazed pastures Mazier, et al 2008), hay meadows (e.g. Hjelle, 1998) and woodlands (this study); such a study in northwest Europe is being carried out by the Crackles Project (see Bunting, et al 2013;forthcoming).…”