Soil chemistry and microbial activity after a surface fire in a mixed temperate forest

10.31195/ejejfs.451884 Eurasian Journal of Forest Science 2018 6(4): 1-13 http://dergipark.gov.tr/ejejfs Soil chemistry and microbial activity after a surface fire in a mixed temperate forest Aliye Sepken Kaptanoğlu*1, Çağatay Tavşanoğlu2, Oğuz Can Turgay3 Research Institute for Forest Soil and Ecology, Eskişehir, Turkey Division of Ecology, Department of Biology, Hacettepe University, Beytepe 06800, Ankara, Turkey 3 Department of Soil Science and Plant Nutrition, Faculty of Agriculture, Ankara University, Dışkapı, Ankara, Turkey *1 2 Corresponding author: Abstract Fire-affected soils have recently received more attention in soil science because some of the atmospheric CO2 emissions have directly been driven from soils during fires and climate change has increased fire frequency in many ecosystems of Earth. However, low-intensity surface fires and their effects on soil properties have been relatively less studied in comparison to moderate to high-intensity crown fires. In this study, the effect of a surface fire on the chemical and biological properties of soil with a thick organic layer was investigated in a mixed forest stand dominated by Castanea sativa, Fagus orientalis and Pinus nigra ssp. pallasiana in Bursa Province, Turkey. Soil samples were taken from burned and unburned (control) sites in three periods: December 2011, July 2012, and November 2013. Samples were analyzed to determine some chemical and biological properties in the soil. We tested the effect of fire and period on each variable by two-way ANOVA analysis. The results indicated that Nt and OM were not affected by fire, while C / N ratio decreased. The difference between the periods was significant as regards OM and acid phosphatase enzyme activity. Fire resulted in a significant increase in soil pH, Ca, Mg and no significant change in P2O5. Although we found that surface fires limited the effect on soil properties, we concluded that there might be positive interactions between increased available nutrients in the soil and the burning of soil with relatively low severity. Prescribed fire can be proposed as a management tool to mitigate fire risks and short-time enrichment of available soil nutrients in these ecosystems. Key words: C / N ratio, enzyme activities, forest, soil nutrients, and surface fire. Inroduction Soil holds vast reserves of carbon, which is two times more than the one held by the atmosphere, and provides food and fresh water security besides hosting biodiversity; therefore, it deserves much greater attention as the biggest environmental matter from the perspective of both climate change and human health (Mol and Keesstra 2012, Keesstra et al. 2016.) The effects of fire on soil are substantially caused by changes in nutrient amounts and cycles (Giardina et al. 2000, Knoepp et al. 2004). Temperate forest soils usually have low nutrient availability while the most limiting nutrient is Nitrogen (N) (Knoepp et al. 2004). Maintenance of plant growth depends on the internal cycling of nutrients in native forests (Perala and Alban 1982, Cole 1995). Due to the consumption and/or 1 Eurasian Journal of Forest Science – Soil chemistry and microbial activity – Kaptanoğlu et al. 2018 6(4) alteration of forest floor and woody fuels through prescribed burning or wildfire, both the quantity of nutrient-containing materials and the patterns of nutrient release change, and this process may indirectly affect soil nutrients (Knoepp et al. 2004). The release of available nutrients through the combustion of organic matter may be a significant natural source of plant growth (Kara and Bolat 2009). In fact, the decomposition rates on forest-floor may increase after burning, releasing NH4+ and other nutrients (Schoch and Binkley 1986, Khanna et al. 1994, Raison et al. 1990, Boydak et al. 1996). Decreasing decomposition rates due to the limited available organic matter after fire may eliminate this response in time (Raison et al. 1990). Since burning alters the nutrient status of soil; some other components of burning such as ash and debris nutrient content and quantity, nutrient loss with ash, amount of non-plant available nutrients’ conversion into mineral forms due to thermal transformation, microbial biomass and activity (Giardina et al. 2000) (i.e. microbial enzyme activity, C and N mineralization rates) depend on nutrient status and they also deteriorate because of fire. Many studies have been conducted on the effects of wildfire or prescribed fire on the physical and chemical (Eron 1977, Eron and Gürbüzer 1988, Neyişçi 1989, Neyişçi et al. 2002, Kantarcı et al. 1986, Kutiel and Shaviv 1992, Boydak et al. 1996, Esquilin et al. 2008, Gürlevik et al. 2009, Tavşanoğlu and Gürkan 2010, Yıldız et al. 2010) and biological (Akburak et al. 2017, Acea and Carballas 1996, Hernandez 1997, Villar et al. 2004, Kara and Bolat 2009) properties of soil in coniferous forests of Mediterranean and temperate zones, where crown fire regimes are dominant. Many ecosystems that are not exposed to frequent crown fires such as tropical and temperate broadleaved rainforests were also studied to explore the effects of fire on soil properties (Turgay et al. 2002, Barreiro et al. 2015). However, relatively less attention has been given to post-fire changes in soil’s physical, chemical and microbial properties in mixed temperate forests where surface fire regimes prevail (see Knoepp et al. 2004, Swallow 2009). There is a lack of information especially about the changes in enzyme activity as an early and sensitive indicator (Taşkın anda Kızılkaya, 2006) and its relation with nutrient mineralization in the soil after burning of the forest floor following surface fires. Temperate deciduous forests are among the most threatened ecosystems on Earth. Fire is one of the major disturbances affecting forests of temperate zone (Frelich 2002), whereas high-intensity crown fire is rare in these ecosystems (Matlack 2013). Therefore, fire return intervals are more than 800 years for crown fires, while decreasing as short as 21 years for surface fires (Brown et al. 1999). The aim of this study was to assess the effects of surface fire on the chemical and biological properties of soil in a mixed temperate forest. Due to the low-intensity of surface fires in temperate forest ecosystems (Matlack 2013), we hypothesized that fire had a little effect on soil properties in these forests and, if any, post-fire regeneration would occur in a very short time. To test these hypotheses, we collected and analyzed soil samples for two years after fire in a burned mixed deciduous-coniferous forest in the northwest of Turkey, and we determined the changes in the chemical and biological properties of the soils. 1. Materials and methods 2.1. Study area The study was conducted in a mixed broadleaved-coniferous forest in Uludağ, Bursa, northwest Turkey (40°09'27'' N, 29°10'01'' E, 630-870 m). 2 Eurasian Journal of Forest Science – Soil chemistry and micro (...truncated)