Evaluating humus forms variation in an unmanaged mixed beech forest using two different classification methods

Abstract

© iForest -Biogeosciences and Forestry IntroductionDecomposition of organic matter plays a vital role in nutrient cycling, driving the mineralization of organically bound nutrients, and making them available for plant uptake. In infertile soils the role of decomposition processes becomes even more significant in nutrient cycling, since almost all plant available nutrients in these ecosystems originate from plant debris (Sluiter & Smit 2001). Different types of humus forms develop within the top-soil throughout the process of biotransformation of dead organic matter. Climatic conditions, soil characteristics and vegetation types are among the main factors affecting this process (Green et al. 1993). Humus forms have been considered as one of the principal components of terrestrial ecosystems ). Since humus forms develop at shorter time scales than soil types, they have to be classified independently (Graefe & Beylich 2006). Humus forms are indicators of ecosystem functioning and characteristics, providing useful information on site conditions such as availability of moisture, soil acidity, nutrient status (Van Delft et al. 2006) and decomposition rates (Ampe & Langhor 2003). Humus represents the complex organic substances resulted from the decomposition of plant and animal fragments. These materials are more stable, colloidal, and mostly in connection with the mineral component of the soil. Humus forms commonly are comprised of organic and organic-enriched mineral horizons at the soil surface, and are considered as natural bodies such as the underlying soils (Green et al. 1993). The morphological study of humus forms has begun since the 19 th century (Ponge 1999) and until now many morphological methods of classification have been developed worldwide (Babel 1971, Green et al. 1993, Brethes et al. 1995, Van Delft et al. 2006, Zanella et al. 2009, 2011. The morphological study of humus forms, in comparison to chemical methods, is inexpensive, easier to manage on the field and can easily be instructed to forest staffs.Hyrcanian forests, covering about 1.9 million ha, are broad-leaved deciduous forests forming a green belt along southern and south-western coasts of the Caspian Sea. They are unique in genetic variation, biodiversity, commercial productions and many other environmental services (Sagheb-Talebi et al. 2004, Poorzady & Bakhtiari 2009, Pourmajidian & Rahmani 2009, Behjou et al. 2009). The first morphological study on humus forms in Hyrcanian forests was done by Sajedi et al. (2004). They classified the humus forms in a pure beech forest using a Canadian grid by Green et al. (1993). Their results showed that Moder was the dominant humus form in the studied stands. In a second report, Waez-Mousavi (2010) applied a European humus classification method (Zanella et al. 2009) to the study of humus forms in some mixed beech stands of Hyrcanian forests. The author found that humus forms belonging to the Mull group were dominant in this area. The present study aimed to compare the two morphological methods of class...

Assessment of Variability among Humus Forms and Soil Properties in Relation to Tree Species and Forest Operations in the Kheyrud Forest, Nowshahr

“…This may be related to a decrease in pH under the influence of pure beech litter and a higher litter decomposition rate of mixed beech stand [35,36]. The amount of organic carbon in the humus layers is an important reason for the accumulation and increase in litter thickness in amphi humus under pure beech litter compared to the mull with a low thickness of organic matter under high-quality mixed beech litter [4,17,33]. In this regard, Zanella et al [6] stated that the C/N ratio in the organic layers of mull humus was lower than the amphi layers, so the C/N ratio is a very important indicator to show the speed of decomposition in different forms of humus.…”

“…The review of previous literature confirmed that the type of forest management is one of the factors affecting the variations in humus form [8,10,16,17]. Morphological studies have investigated humus forms and forest floor characteristics under the influence of different tree stands along elevation changes [4,17], but so far it has not been investigated in the forest area with a close focus on forest operations.…”

“…The review of previous literature confirmed that the type of forest management is one of the factors affecting the variations in humus form [8,10,16,17]. Morphological studies have investigated humus forms and forest floor characteristics under the influence of different tree stands along elevation changes [4,17], but so far it has not been investigated in the forest area with a close focus on forest operations. In this study, the humus morphology was investigated in relation to the physical and chemical properties of the soil under the influence of the litter of different tree species (three stands of beech, beech-hornbeam, and mixed beech) on skid trails in different time intervals after harvesting operations.…”

Humus forms in a Mediterranean area (Castelporziano Reserve, Rome, Italy): classification, functioning and organic carbon storage

“…Amphi forms are common in Apennine forests (Andreetta et al, 2011), very common in Alpine forests, especially on the East of the chain (the most consistent group of humus forms, Garlato et al, 2009b), mostly on calcareous substrates (Sartori et al, 2007;Garlato et al, 2009ab) and the thickness of organic layers positively correlated with the percentage of rock fragments in the A horizon (Ponge et al 2014). This form is well known in Germany (Graefe, 2007), and in France (Jabiol, 2009) and covers the soil of a large part of broadleaved deciduous Hyrcanian forests, along the southern and southwestern coasts of the Caspian Sea (Waez-Mousavi and Habashi, 2012). Graefe (2007) supposed that this humus form arrived in Germany only a few years ago and could be used as an indicator of warming climate change, because it is easy to survey thanks to the evident concomitant presence of OH and A horizons made respectively by small animals (arthropods and enchytraeids) and large earthworms (anecic and endogeic).…”