Projected regional forest plant community dynamics evidence centuries‐long effects of habitat turnover

Abstract

Questions Many Western European and North American countries have been experiencing strong reforestation in the last two centuries due to agricultural abandonment. Other land‐use changes, such as urbanization, can simultaneously trigger forest erosion. In this context of habitat turnover, forest understorey plant dynamics depend on the balance between immigration credit in post‐agricultural forest and extinction debt in ancient forest. The transient and final community properties following concomitant habitat creation and destruction are poorly known. In this contribution, we study the projected transient regional forest plant dynamics and identify the determinants of the relaxation duration at both landscape and patch scales. Location Seine‐et‐Marne region, France. Methods Species’ incidences are projected in 9,208 patches of the Seine‐et‐Marne region characterized by strong development of post‐agricultural forests and a moderate erosion of ancient forests during the period 1840–2000. We use a metapopulation model with static biodiversity data and landscape history to project forest plant dynamics. We focus on 33 generalist forest species that are able to colonize both ancient and post‐agricultural forests. Results Our analyses reveal that (1) extinction in ancient forests slows the colonization process, which lasts between 250 and 990 years after habitat turnover, depending on species characteristics; (2) the species incidence in post‐agricultural forests converges towards that in ancient forests long before the overall species incidence stabilizes at the landscape scale (i.e. long before the relaxation time); (3) landscape‐ and patch‐scale relaxation times depend on species colonization ability and patch functional connectivity; (4) the colonization process is rather slow for ancient forest species; and (5) the incidence of ancient forest species becomes larger than the incidence of other species at the end of the colonization dynamics thanks to their strong persistence. Conclusions Ancient forest species may potentially benefit from a large immigration credit but need centuries to use it. On such time scales, many perturbations are likely to jeopardize the realization of this potential credit.

Historical ecology and ancient forests: Progress, conservation issues and scientific prospects, with some examples from the French case

“…Further, a recent modelling approach indicated that AFS have a low turn-over rate in which Petersen (1994), Graae (2000), Graae, Sunde, and Fritzboger (2003) France Dupouey, Sciama, Dambrine, and Rameau (2002), Sciama et al (2009), Bergès et al (2016), Germany Wulf (1997), Schmidt et al (2014) Great Britain Rackham (1980) Hermy et al (1999), Verheyen et al (2003), Hermy and Verheyen (2007) TA B L E 1 Lists of ancient forest species by country or region. Updated information based on Hermy (2015) limited colonization capacity is associated with a low propensity for extinction (Lalechère, Jabot, Archaux, & Deffuant, 2017); this increases their colonization potential (Lalechère et al, 2018).…”

“…colonisation credit Lalechère et al (2018). propose a metapopulation dynamics modelling approach to assess relaxation time following simultaneous ancient forest loss and afforestation on former agricultural lands; they applied this approach to AFS and non-AFS in a large landscape in northern France.…”

“…Relaxation time at the patch and landscape scales depends on species colonization capacity and patch functional connectivity. AFS may benefit from an immigration credit but this could take centuries; however, a new equilibrium is unlikely to happen because land use changes would continue to occur during that time(Lalechère et al, 2018).Despite attempts to consider ecological complexity, one limitation of Lalachère et al's study is that, due to the lack of intermediate maps, the metapopulation dynamics were modelled based on a hypothetical instantaneous landscape change sometime between 1840 and 2000. To improve assessments of relaxation time, appropriate high-quality historical data are needed to evaluate the role played by temporal dynamics during habitat turnover(Essl et al, 2015;Lalechère et al, 2018).…”

Relative importance of landscape and species characteristics on extinction debt, immigration credit and relaxation time after habitat turnover

“…For instance, some observations related a positive correlation between the payment of the extinction debt and patch area but also a negative correlation between these payment and fragmentation degree (Ferraz et al, ; Halley, Iwasa, & Vokou, ). More precisely, Lalechère, Jabot, Archaux, and Deffuant () showed that the relaxation time depends on functional connectivity and that dispersal distance mediates the strength of this relationship. Their results were based on the analyses of contrasted forest plant species (according to dispersal and turnover rates) inventoried in a French region.…”

Importance of climate‐induced tree species composition changes in forecasting the amount of reachable habitat for forest birds

“…Fifth, the equivalent connectivity index compared two static independent landscape graphs (in 2020 and 2050) to provide information about the actual and future need for conservation actions, but did not evaluate metapopulation dynamics over time. We point out that the equivalent connectivity index can be incorporated into discrete time metapopulation models to evaluate species dynamics and the speed of colonization and extinction processes over time (Lalechère et al, 2018).…”