Effects of Land Use Changes on the Soil Physicochemical Properties in South-Western Algeria

This study shows the impact of the reforestation program by some tree species (Pinus halepensis, Cupressus sempervirens and Eucalyptus camaldulensis) on the soil physicochemical parameters in south-western Algeria steppe. The study was realized on soil samples from the Touadjeur site. One hundred soil samples were taken from the field, followed by physicochemical analyses in the laboratory. A comparison of the soil elements between reforested and unreforested sites considered as a control was carried out. The results show that there are differences in the physicochemical parameters of the soil between the reforestation and the non-reforestation ones constituted by a steppe vegetation. The ANOVA one way test shows a highly significant difference change in soil physical parameters, moisture, holding capacity and saturated hydraulic conductivity, but no change in apparent density, actual density and color. Also, from a chemical point of view, the differences concern the organic matter, organic carbon, pH and certain soil contents. The main differences in soil properties between the reforestation sites and the control site, reflect the consequences of forest management adopted by the forest services, most probably the choice of reforestation species.

Potential of Birch (Betula pendula Roth and B. pubescens Ehrh.) for Forestry and Forest-Based Industry Sector within the Changing Climatic and Socio-Economic Context of Western Europe

Five commercial tree species comprise nearly 80% of the forest standing stock volume in Western Europe. Nowadays, there is a strong need to consider a wider diversity of tree species, as evidenced by the impact of climate change and the forest health crises over the past decades. In this context, this study focuses on the potential of birch (Betula pendula Roth and Betula pubescens Ehrh.), a neglected indigenous species, for forestry and the forest-based industry sector. We have therefore compiled, analyzed, and discussed literature regarding the strengths and weaknesses of the species and the opportunities and threats of its use for this purpose. Among the strengths, birch tolerates various climates and sites, and high genetic variability promotes its adaptability. Birch improves forest resilience by colonizing forest gaps and quickly increasing soil functioning and biodiversity. Birch is also remarkably resistant to game overpopulation-associated damage. Large-sized logs are produced within relatively short periods with proper silvicultural treatment, and the wood characteristics allow versatile and valuable uses, as shown in Northern Europe. However, its weaknesses include high sensitivity to crown competition and to wood rot as challenges for silviculture. Among the opportunities, birch is well-suited to the global changes with its adaptability to climate change and its possible integration in diverse productive mixed tree stands. In the context of societal evolutions and customer perceptions, birch wood could play an increasing role in the building and furniture sectors, and among non-wood forest products. In Western Europe, the main obstacle to birch development is the lack of information on the wood uses and, consequently, the lack of interest among forest managers and wood processing professionals, which have led to a poor quality of the resource and to insufficient demand for its wood. Moreover, its fast height growth can affect the vitality of other species in mixed stands. Our analysis highlighted the potential of birch in the Western European forestry considering societal, ecological, and economic purposes in a changing climatic and socio-economic context and the need to (i) develop opportunities for industrial uses of birch wood, (ii) inform forest owners, managers, and industrial professionals about the potential value of birch, and (iii) define silvicultural guidelines.

ECOLOGICAL CONSEQUENCES OF CARBON SUBSTRATE IDENTITY AND DIVERSITY IN A LABORATORY STUDY

Plants return a wide range of carbon (C) substrates to the soil system. The decomposition rate of these substrates is determined by their chemical nature, yet few studies have examined the relative ecological role of specific substrates (i.e., substrate identity) or mixtures of substrates. Carbon substrate identity and diversity may alter soil chemistry and soil community composition, resulting in changes in belowground ecosystem functions such as decomposition and nutrient transfer, creating feedbacks that may affect plant growth and the aboveground community. A laboratory experiment was set up in which eight C substrates of varying chemical complexity were added to a base soil singly, in pairs, fours, or with all eight together every four days over a 92-day period. After 92 days these soils were analyzed for changes in chemistry, microbial community structure, and components of ecosystem functioning. The identity of the added C substrates significantly affected soil chemistry, microbial basal and substrate-induced respiration, and soil microbial community structure measured by either the catabolic response profile (CRP) technique or phospholipid fatty acid composition. These belowground changes strongly affected the ability of the soil microflora to decompose cellulose paper, probably because of differential effects of the C substrates on soil energy supplies and enzyme activities. The addition of C substrates to soils also reduced plant growth compared to the unamended control soil, but less so in soils amended with a tannin than those amended with other substrates. Carbon substrate diversity effects saturated at low diversity levels, tended to have neutral or negative effects on ecosystem functions, and depended strongly on which C substrates were added. It increased CRP compound use but had little effect on other measures of the soil microbial community. Overall, results showed that the chemical nature of C substrates added to soil, and sometimes their diversity, can affect the soil microbial community and soil chemistry, which subsequently affect other ecosystem processes such as decomposition and plant growth. The identity and diversity of substrates that plants add to soil may therefore have important consequences for both above- and belowground ecosystem functions.