Many common agronomic practices affect weed seed dormancy and germination by influencing the microenvironmental and edaphic conditions surrounding seeds in soil. Factors such as light penetration, soil water content, soil fertility, and temperature are modified by tillage, planting, harvesting, and other production practices, resulting in enhanced or depressed weed seed germination. Changes in these environmental factors may also indirectly lead to alterations in phytohormone concentrations during seed development, which can subsequently affect dormancy status of the mature seed. Integrated approaches that place priority on depleting weed seed banks through interfering with dormancy or germination requirements have strong potential to enhance weed management aspects of agricultural systems.

We studied the vegetation and soil properties of a dry forest that had once been disturbed in central Myanmar using 30 quadrats (20 × 20 m) established in 2012. For 30 species, the overall density was 706 individuals ha−1, and the basal area was 2.92 m2 ha−1. The forest was a mosaic of six community types, each of which was dominated by a single species. Dominant species that were capable of resprouting accounted for 47–78% of the total density and 56–83% of the basal area of the communities. We related seven soil properties to the vegetation patterns using canonical correspondence analysis (CCA). The CCA results highlighted remarkable associations of species such as Acacia catechu, Dalbergia paniculata, Terminalia oliveri and Millettia multiflora with soil texture. Acacia inopinata was associated with a high soil pH (i.e. 9–10), and Terminalia tomentosa was associated with soil hardness. Our results indicate that secondary succession of a dry forest is not initially led by pioneer species, but instead, by superior competitors capable of resprouting, and that species distributions are primarily determined by the filtering effects of edaphic conditions. We believe that the dry-forest species retain their soil–species relationships despite heavy disturbances.

The spatial distribution of two rain forest tree species, Carapa procera (Meliaceae) and Vouacapoua americana (Caesalpiniaceae) was analysed within and between plots of different sizes (6.25 and 25 ha) at Paracou, French Guiana. The L(d) function was used to characterize spatial patterns, and the Lij(d) intertype to study independancy between young and adult trees. Although both species are known to be dispersed by caviomorph rodents within short distances (c. 10–20 m and up to 50 m) of parent tree crowns, the analysis of tree positions led to different spatial patterns between species depending on soil drainage characteristics. Overall, while V. americana showed a strongly aggregated spatial distribution, C. procera had a weaker propensity to depart from complete spatial randomness (CSR). A complex distribution, sometimes clustered in areas with hydromorphic soils (swamps and around streams) and sometimes very near CSR outside these areas characterized the C. procera population. When C. procera tree aggregation occurred, there was a slight attraction between juveniles and adults. The aggregation of V. americana trees was evidenced at different levels depending on the scale of investigation. Within small plots (6.25 ha), a first level of aggregation with short distance radii of c. 10–25 m giving small clusters, and a second level which is composed of small clusters aggregated at c. 40–50 m distance radius, were observed. A third level of aggregation was suggested by analysing the tree population at the larger scale (25 ha) whose boundaries outside the plot were not delimited. Aggregation of V. americana trees at all levels was enhanced by a strong attraction between juveniles and adults. These results were discussed in light of seed and seedling ecology, especially with regard to seedling and sapling gap-dependence and soil drainage, which likely affected the recruitment of juvenile trees, and henceforth final tree spatial pattern.