DOI: 10.5285/9947ccc9-7396-4821-b095-c374bd857305
title: Soil, site and tree characteristics for acute oak decline (AOD) symptomatic and non-symptomatic oak in three UK woodlands, southern England, 2016

description: This dataset contains information on tree, site and soil properties from three oak woodland sites in southern England: Writtle Forest, Monks Wood, and Stratfield Brake. Data were collected in 2016 to investigate the relationship between Acute Oak Decline (AOD) symptoms and local environmental factors. The study included 10 symptomatic and 10 asymptomatic trees at each site.

Tree characteristics include latitude and longitude coordinates, species-level classification (based on morphological measurements and genetic SNP analysis confirming identity as Quercus robur, Quercus petraea, or hybrids), tree dimensions (height, diameter at 1.35 m, crown dimensions), crown condition (density reduction), and rooting depth.

Data on the surrounding site context were also collected, including depth to gleying, basal area of surrounding stands (measured at 0-20 m and 20-40 m), compound topographic index, and tree social status (e.g., dominant, codominant, suppressed).

Soil characteristics were analysed to capture both physical and chemical properties. Physical properties included texture and bulk density, while chemical analyses measured organic matter content, pH, total carbon and nitrogen, mineral nitrogen (nitrate and ammonium), 'Olsen' extractable phosphorus, cation exchange capacity, and concentrations of exchangeable cations.

The work was supported by the grant BB/N022831/1 ('PuRpOsE') with additional funding from the Woodland Trust, Bartlett's Tree Experts and The University of Reading.
description: Selection of trees for sampling involved systematic field surveys, targeting symptomatic (stem bleeding cankers) and asymptomatic trees. 

Tree and site characteristics were determined using standardized forest mensuration protocols. Soil samples (taken from 5-15 cm and 40-50 cm depths from randomly-selected positions 1.5-2.0 m away from the stem from each tree) were prepared for analysis of physical and chemical properties using standard laboratory methods (e.g., BaCl2 extractions for exchangeable cations, and the Olsen method for phosphorus). Soil samples were analysed using laboratory equipment such as a Malvern Mastersizer 3000 for particle size analysis, a FLASH CN elemental analyzer for carbon and nitrogen content, and a Perkin Elmer 3000 ICP-OES for cation analysis. A Skalar SAN++ autoanalyzer was used for phosphate, nitrate and ammonium determination.

Variables (units) include tree dimensions (meters, centimetres), soil chemical concentrations (mg/kg), and physical properties such as texture (percentages of clay, silt, and sand). Additional variables include crown density reduction (percentage).
Composite soil samples were prepared by pooling subsamples, and chemical analysis results are normalized to dry soil weight.

Laboratory analyses included technical replication (e.g., three replicates for LOI, five for particle size distribution) and calibration using external standards. Blanks were analysed alongside samples for nutrient and cation extraction procedures.
Data reliability may be influenced by the sampling resolution and the inherent variability in soil properties. Some chemical concentrations were below detection limits and are entered as half the detection limit, following USEPA (2000) guidelines. Observations and samples represent a single time point, limiting temporal insights into soil and tree dynamics.