Can mixed pine forests conserve understory richness by improving the establishment of understory species typical of native oak forests?

Abstract

& Key message A positive effect of mixed pine forests (Pinus sylvestris L. and Pinus pinaster Ait.) on the understory richness and tree regeneration was observed with respect to monospecific stands. Understory species typical of the native Pyrenean oak forests in the Iberian Peninsula contribute to maintaining high understory richness in such mixed pine forests. & Context The influence of stands characteristics on the understory in mixtures that combine coniferous tree species of the same genus deserves more study since they are frequent in Spain. & Aims To assess the effect of mixed versus monospecific stands of Pinus sylvestris L. and Pinus pinaster Ait. on the main tree species regeneration and understory species composition. & Methods Tree regeneration and understory species composition were inventoried in eighteen forest plots (6 triplets) in North-Central Spain. Each triplet consisted of two plots dominated either by Scots pine or Maritime pine and one mixed plot that contained both species. & Results The basal area (%) of both Pinus species was the only characteristic of the stands that significantly influenced the understory composition and tree regeneration. Characteristic species of humid and temperate zones, including P. sylvestris regeneration, dominated in Scots pine stands, and typical species of well-drained Mediterranean areas, including P. pinaster regeneration, dominated in Maritime pine stands. In mixed stands, the highest regeneration of the native Pyrenean oak with respect to monospecific stands was accompanied by understory species typical of native oak forests that share the same regeneration niche. & Conclusion Mixed pine forests allow the development of understory species better than monospecific forests.

Testing the effect of restoration‐focused silviculture on oak regeneration and groundlayer plant communities in urban–exurban oak woodlands

“…Seedling survival was strongly predicted by a combination of light availability and groundlayer cover, with greater groundlayer cover related to lower seedling survival rate. Groundlayer vegetation often represents direct competition for young seedlings (Lorimer et al 1994), can limit light availability at the groundlayer (Miller et al 2016), but can also mediate environmental conditions in the understory (López‐Marcos et al 2020). The response of shrub and herbaceous layer to overstory removal, therefore, can limit the positive effect of canopy thinning on seedling survival and growth (Montgomery 2004; Kern et al 2006), but may also facilitate establishment under some conditions (Torroba‐Balmori et al 2015; Alday et al 2016).…”

Characterization of mixed and monospecific stands of Scots pine and Maritime pine: soil profile, physiography, climate and vegetation cover data

“…Triplets belong to the network of permanent plots of the Sustainable Forest Management Research Institute UVa-INIA (iuFOR). In this network, the mixture effect has been analysed on growth efficiency (Riofrío et al 2017b;Cattaneo et al 2020), crown morphology (Cattaneo et al 2020), carbon stocks and exchangeable cations along the soil profile (López-Marcos et al 2018), understory response to overstory (López-Marcos et al 2019), understory richness and forest regeneration (López-Marcos et al 2020a), height diameter and basal area increment (Riofrío et al 2019) and changes in structural heterogeneity and stand productivity (Riofrío et al 2017a).…”

“…In mixed stands, the highest regeneration of the native Pyrenean oak (Quercus pyrenaica Willd.) was accompanied by typical species that share the same regeneration niche (López-Marcos et al 2020a).…”

“…in Spain. Soil characterization allowed to describe fertility and carbon dynamic along soil profile (López-Marcos et al 2018), and the study of the understory and overstory features provided information about biodiversity functioning (López-Marcos et al 2020a) and its relationship with soil properties (López-Marcos et al 2019).…”

“…in Spain. Soil characterization allowed to describe fertility and carbon dynamic along soil profile (López-Marcos et al 2018), and the study of the understory and overstory features provided information about biodiversity functioning (López-Marcos et al 2020a) and its relationship with soil properties (López-Marcos et al 2019).The essay, located in North-Central Spain, consists of eighteen forest plots divided in six triplets. Each triplet includes three circular plots of 15-m radius located less than 1 km from each other: two monospecific plots dominated by P. sylvestris or P. pinaster, and one mixed plot of both species.…”