1. How much does it take to be old? Modelling the time since the last harvesting to infer the distribution of overmature forests in France
- Author
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Frédéric Bray, Vallet P, Thompson L, Yoan Paillet, Nicolas Debaive, Eugénie Cateau, André Torre, Laboratoire des EcoSystèmes et des Sociétés en Montagne (UR LESSEM), Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), and Réserves Naturelles de France
- Subjects
0106 biological sciences ,Mixed model ,010504 meteorology & atmospheric sciences ,old growth ,Forest management ,Distribution (economics) ,time since the last harvesting ,010603 evolutionary biology ,01 natural sciences ,Basal area ,distribution ,stand structure ,0105 earth and related environmental sciences ,Estimation ,forests ,business.industry ,Temperate forest ,Forestry ,15. Life on land ,Maturity (finance) ,Metropolitan France ,Geography ,[SDE]Environmental Sciences ,proportion ,business ,maturity - Abstract
Aim : The global knowledge of the distribution and proportion of forests with high conservation values such as mature forests in metropolitan France is scarce, focuses only on a few specific well-known sites, and has never been tackled countrywide and evaluated with a robust multivariate statistical approach. Here, we modelled French forest reserves9 time since the last harvesting operation, then inferred the current statistical distribution of mature forests (i.e. forests over 50 years without harvesting) in metropolitan France. Location : Metropolitan France Methods : We used inventories of forest stand structure issued from forest reserves and managed forests to calibrate a generalised linear mixed model explaining the time since the last harvesting with selected stand structure attributes of maturity, combined with environmental variables. We chose the time since the last harvesting as a proxy for forest maturity, assuming older unmanaged plots to host older trees. We then projected this model on an independent nation-wide dataset issued from the National Forest Inventory. Thus, we obtained an updated estimation of the proportion and a rough distribution of mature forest stands (i.e. abandoned for over 50 years) in metropolitan France. Results : We found that the structural variables that best characterized the time since the last harvesting were high basal area of very large trees, high volumes of both standing and downed deadwood, high diversity of tree-related microhabitats and more marginally diversity of decay stages. Variables translating legacy of past forest management also characterised more mature plots, which displayed lower volumes of stumps and high density of coppices. Our projection gave an estimated 3% of French forests over 50 years without harvesting and a promising proportion of French forests that could reach interesting levels of maturity in the near future. Main conclusions : Our model showed that the time since the last harvesting is a good proxy for forest maturity in French temperate forest. It highlighted the stand structure attributes that are key in characterising those forests with high conservation values. We found that forests with higher levels of maturity seem to be located in more inaccessible places notably mountainous areas. Our projection gives the first robust statistical estimate of the proportion of mature forests in metropolitan France and may serve to report on the status of mature forests.
- Published
- 2021
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