Response of understorey plant communities and traits to past land use and coniferous plantation

Abstract

NomenclatureFrench BDTFX flora nomenclature and European BDNBE bryophyte nomenclature Abstract Questions: How did past land use and conifer plantation affect understorey plant communities? What plant traits explain understorey vegetation response to agricultural past land use and coniferous plantation?Location: Forest of Orl eans (50 000 ha), Loiret, north-central France.Methods: Canopy cover, herb layer composition, litter and soil properties were measured in 80 100 m 2 plots sampled in plantations of Pinus sylvestris or P. nigra vs natural regenerations of Quercus petraea and Q. robur along a gradient of forest continuity (using historical maps and aerial photos from 1840, 1949 and 2006). We related 15 plant traits to past land use and tree species using RLQ and fourth-corner analyses.Results: The magnitude of past land use effect largely exceeded that of coniferous plantation. Post-agricultural forests, even 150 yr after afforestation, differed from ancient forests in soil properties (thinner humus layer, higher P content, higher pH and lower C/N ratio) and plant traits. Ancient forests hosted more forest core species, stress-tolerant, competitive species and bryophytes, but fewer ruderals, annuals/biennials, shrubs and trees and nutrient-demanding species, and had lower SLA and higher LDMC. Conifer plantations had a thicker humus layer, lower pH and higher C/N ratio than deciduous forests, and hosted more light-demanding species but less forest core species. Importantly, differences in soil and plant traits between conifer plantations and naturally regenerated deciduous stands were discernible in both recent and ancient forests, indicating that tree species lastingly influence ecosystem functioning.Conclusions: Past land use and coniferous plantation resulted in different understorey plant communities and traits under pine plantations and naturally regenerated oak stands. These differences were driven through soil acidification, litter decomposition rate, light conditions, canopy development, soil disturbance, stand management and dispersal and recruitment limitations. Coniferous plantations slowed down the recovery of post-agricultural forests to ancient deciduous forest conditions. Applying natural regeneration and favouring native deciduous tree species thus helps recreate or maintain ancient forest plant communities.

Land use legacies on forest understory vegetation and soils in the Mediterranean region: Should we use historical maps or in situ land use remnants?

“…The higher species richness we detected in recent forests could result from (1) the succession process, which involves an overlap of species assemblages of different forest successional stages in recent forests, as demonstrated in Mediterranean forests by Amici et al (2013) and 2 relationship between soil fertility and species richness, soils on former terrace being the deepest, and thus the most fertile (Grime, 1973;Aarssen, 2001). Understory plant species richness and composition slightly varied among map-based PLUs, in accordance with previous results conducted in temperate forests (Hermy and Verheyen, 2007;Dyer, 2010;Brudvig et al, 2013;Bergès et al, 2017). However, the magnitude of the effect was rather low.…”

Historical ecology of Mediterranean forests: Land use legacies on current understorey plants differ with time since abandonment and former agricultural use

“…We tested the relationship between traits and historical variables using RLQ and fourth-corner analysis (Bergès et al, 2017;Dray et al, 2014). We tested the significance of the RLQ with a randtest function and tested the significance of each trait versus each historical variable with a fourth-corner analysis using the function fourthcorner.rlq (Dray et al, 2014).…”

“…In former studies, the effect of forest temporal continuity and past land use mostly concerned soil physico-chemical properties and vegetation (Bergès et al, 2017;Hermy & Verheyen, 2007), but now focuses more and more on other species groups with low dispersal abilities, such as saproxylic beetles, snails, collembola, etc. (Janssen, 2016;Janssen et al, 2018;Vrignaud, 2016).…”

Natural and human-impacted diversity of bryophytes along an elevational gradient on an oceanic island (La Palma, Canarias)

“…Specifically, certain groups, strictly depending on undisturbed shady regimes in natural forests (e.g., liverworts and perennial species, [42]) are the first to disappear, especially when the canopy is opened and microhabitats lose balanced humid and shady conditions [43]. Changes in species composition after different land use changes depending on light exposure has been also observed for bryophytes [44] and vascular plants [45]. With these trends, colonist species are able to expand their (elevational and thus ecological) distributional ranges as narrow-ranged species as Exsertotheca intermedia , Homalothecium mandonii or Leptodon longisetus , which are also macaronesian endemics, decreases (see S1 Table).…”