Reflectance spectroscopy in near-IR and medium-IR (NIRS-MIRS)& chemical analysis

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Historical context of “Lorraine” communal forests

Most of the communal forests in Lorraine are divided into compartments inherited from the former supervision of the State. During the 16th century, deforestation pressure had led royal order to require the imposition of a third woodland area being kept in reserve in 1561 and then a quarter in 1573. Is in 1669 thanks to the Colbert’s reformation that reserve quarter notion is generalized: local communities will have to save a forest quarter for extraordinary cuts while the remainder of the forest was exploited for firewood (Figure 2) (Husson, 1991; Rochel, 2013). At that time, Lorraine was not yet part of the France kingdom. However, in the 18th century, the Dukes of Lorraine adopted the measure of the reserve and applied it to the woodlands of the duchy (Dupouey et al., 2014). Former registers specify that the “quart de reserve” had to be located far from forest edges and villages, to avoid any pillaging (Degron, 1999 a). Spatial organisation of communal forests was often accompanied by a first forest surveying and mapping (See Annex 1:“Survey maps” 1740 – 1790). The forestry code reformation of 1827 has not changed the reserve quarter regulation but during the 19th century extraordinary cut permissions increased considerably (Degron, 1999 b). From 1880, QR was divided caused by repetition of extraordinary cut (See Annex 1: Subdivision plan for the “quart de reserve”). In the early 20th century, the coppice and coppice with standards, are accused of producing low-quality wood and be expensive in labour. High forest conversion has been established to ensure the demand of timber and the effective division between QR/CA disappeared. It’s in 1969 that QR obligations disappear by a public finance law.

Hypotheses raised in the present study

As seen previously, short term impacts from high biomass exportation are well known: to cause a soil fertility loss and to foster species which are opportunistic in open and disturbed areas. Nowadays, reserve quarter regulation represents past ecological footprint from high biomass exportation period. Using the opportunity of this documented historical situation, we tested the following hypotheses:
H1: High wood extraction in “coupes affouagères” has resulted in loss of mineral (cations, acidity) and organic fertility (soil carbon and nitrogen content).
H2: Disturbances, more frequent in “coupes affouagères”, resulted in colonization by species of disturbed habitats (nitrophilous and heliophilous).

Soil analysis: Reflectance spectroscopy in near-IR and medium-IR (NIRS-MIRS) & chemical analysis

Since first results have showed a significant difference for the soil carbon content between CA and QR, we were used a rapid and cheap method (NIRS-MIRS) which has proven its efficiency to discriminate among functional SOM fractions (Cecillon et al., 2010). Near and medium –infrared spectra depend on the number and type of chemical bonds in the material being analysed. The wide variety of these bonds gives rise to ‘fingerprints’ of soil samples (Ertlen et al., 2010). So our purpose was to compare the NIR & MIR spectra of soils from QR treatment with those of soils from CA treatment. For the physico-chemical analyses, soil samples will be sent to the Arras INRA centre and results should be received not before September 2014.
In this study, all data (soil, floristic and dendrometric) are analysed to test whether differences exist between “coupes affouagères” and “quart de reserve” modalities.
For univariate analyses, a paired t test was used to compare means according to each treatment. Each sample observation is linked to a homologous observation of a second sample. For multivariate analyses, linear models were built: the explanatory variable is the historical management (QR vs CA) treated as fixed effect, covariates are site (random effect) and study (2010 vs 2014, fixed effect). For this model, we supposed that residues follow a normal distribution of same variance. Then, analyses of  variance analyse the amount of variance that is contributed to a sample by different factors.

Colonization of plant species of disturbed habitats

The extension of the sampling on marly area allows us to see a significant difference of plant communities between “coupes affouagères” and “quarts de réserve”. The correspondence analysis of the herbaceous strata shows a first axis of inertia defined by a classical gradient of soil acidity and that explains the site effect highly significant on this axis. When this effect is designated cofactor, we see a trend of the silvicultural past effect: “coupes affouagères” include species from disturbed habitats which prefer high nitrogen content and hydrophilic soils, while the “quart de réserve” has species from stable environments associated to slightly acidic soils.
A probability test of relative frequencies of each species according to former forest management has showed that:
– The “coupes affouagères” favour the presence of Carex flacca and Viburnum opulus; these species are heliophilous and neutroclines. These are species that we find in disturbed environments such as edges, roads and logging (Rameau, 1989).
– The “quart de reserve” favours the presence of Ajuga reptans and Rosa arvensis; we do not explain these results since these specie prefer nitrogen-rich environments (Rameau, 1989).
Contrary to what might be expected, species richness is not higher in “coupes affouagères”.
Our second hypothesis is partially validated, repeated cuts in “coupes affouagères” bring about a colonization of forest species subjected to disturbance. Our results confirm what was observed previously by Saur (1951): the old cuts contain herbaceous species in hydrophilic nature. However, we must consider that from the mid-18th century, all communal forests were converted from coppice-with-standard to high forest. Becker (1979) observed a number of species preferentially associated to stands under conversion (Phyteuma spicatum, Cardamine pratensis, Ranonculus auricomus) that they tend to prefer “coupes affouagères” in our flora analyses.

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Preservation of very large wood in the reserve

The role of the “quart de réserve” was to keep a timber capital susceptible to be exploited for extraordinary cuts. Today, we see a historical memory with a trend to have more very large wood (circumference> = 212 cm) in the “quart de reserve” compared to “coupes affouagères”. Comparisons of total basal area by diameter classes or by species show no significant differences between “coupes affouagères” and “quart de reserve”; this is due to criteria selection of our sites. The choice of uniform stands between the two treatments was part of these criteria. In addition, the conversion to high forest of former “coupes affouagères” favoured the presence of large timber and homogenized stand structure on all forests areas.

Limitations of the study

All the results presented above show low impacts on forest ecosystem due to extraction of firewood in “coupes affouagères”. The main limitation of our study of historical ecology is the information source of the old silvicultural treatment. Indeed it has been difficult to find the localisation plans of communal forests in the 18th and 19th centuries to develop our study. But we have no certainty about the rates and frequencies of sampling biomass under both management methods.
According to several studies in historical biogeography, regulation of the “quart de reserve” was not fully respected:
– From 1840 to 1880, the number of authorisations of deemed extraordinary cuts increased significantly in “quarts de reserve”, going from 4 to 20 per year (Degron, 1999).
– A recent study looked at the records of timber hammerings (115 cups) of Lorraine communal forests. First results show that the population of the reserve is rich in large wood but permitted exploitations not leave more than a poor density of high forests (Rochel, 2013).
More, real duration of these silvicultural practices is not known for studied forests.
Regarding floristic surveys, they have often been made in poor habitats in our study. This does not favour the appearance of a difference in species richness between “coupes affouagères” and the “quart de reserve”. Furthermore, aggregation of data flora between the previous study and the present study clearly shows an observervation bias. Several inter-calibration exercises on the quality of observation during floristic surveys indicate differences there are sometimes important between surveys of observers. These differences are mainly due to: inaccuracies allocation to a stratum, problems of determination for herbaceous species and mosses, the number of observers and the survey duration (Camaret et al., 2004).
We could talk about a final classical limit: a number of samples too low (68), increasing repetitions we can more easily highlight the differences between former silvicultural managements. But their extent would remain low.

Table of contents :

LIST OF TABLES
LIST OF FIGURES
LIST OF ANNEXES
LIST OF ABBREVIATIONS
INTERNSHIP PRESENTATION
INTRODUCTION
LITTERATURE SYNTHESIS
Forest ecosystem modification by human actions: state of knowledge
Short term impacts of intensive forest biomass exportation
Long term impacts of past land use
Historical context of “Lorraine” communal forests
First results from a previous study
Hypotheses raised in the present study
MATERIAL AND METHODS
Study area
Sites selection by map analysis and field prospection
Sampling plan
Dendrometric protocol
Floristic protocol
Soil protocol
Humus and soil profile description
Soil sample
Soil analysis: Reflectance spectroscopy in near-IR and medium-IR (NIRS-MIRS)& chemical analysis
Statistical analysis
Stand analysis
Floristic analysis
Soil analysis
RESULTS
Studies aggregation and sites selection
Stand analysis
Flora analysis
Correspondence analysis
Probability test of apparition frequencies for each species
Ellenberg’s and Julve’s coefficients
Soil analysis
Soil properties
Bulk density
NIRS – MIRS analysis
DISCUSSION – CONCLUSION
BIBLIOGRAPHIC LIST.

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