Ayten Karaca

Soil Enzymes as Indication of Soil Quality

Soil, water and air are natural resources as well as pollution reservoirs. Soil quality can be changed by pollution, ecological perturbations and agricultural practices. Soil quality can be defined as, “the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation”(Karlen et al. 1997). Preserving soil quality should be needed for sustaining of life and human nutrition. Soil enzymes are used as soil quality indicators for quick response of changes for environmental stress, pollution and agricultural practices much more sooner (1–2 year) than other soil properties (organic matter); easy to measure (relatively simple procedure), having relations with plant productivity, soil quality parameters (organic matter, soil physical properties, microbial activity, and microbial biomass), and biogeochemical cycle; and being integrative. This chapter mainly covers three distinct effects for changes in soils: (1) pollution (heavy metals, pesticides, industrial amendments or contaminants, hydrocarbons, acid precipitations, industrial air pollutants, sewage sludge, and waste usage), (2) ecological perturbations(land use, devegetation and revegetation, changing climatic conditions, and forest fires), and (3) agricultural practices (irrigation, fertilizers, amendments, different management and farming systems, crop rotation, and tillage).

Effects of Heavy Metals on Soil Enzyme Activities

The pollution of the soil with heavy metals is one of the worst legacies of our intensive agricultural–industrial activities, and it negatively affects various characteristics of the soil, including soil enzyme activities. Soil enzymes are natural molecules that catalyze soil microbial reactions and mainly originate from microorganisms and plants. Since enzyme activities play fundamental roles in soil chemical and biological reactions, their inhibition by heavy metals has received considerable attention and has been well documented by many researchers over the last few decades. The activities of soil enzymes have often been proposed as sensitive indicators of important microbial reactions involved in nutrient cycles and they respond to changes in the soil caused by natural or anthropogenic factors. In this regard, soil enzyme activities are often used to evaluate the impact of human activity on soil life. The purpose of this chapter is thus to emphasis some facts, hypotheses, and probabilities, as well as the results of research into the relationships between soil enzymes and heavy metals.

Biology of Earthworms

Earthworms, which belong to the order Oligochaeta, comprise roughly 3,000 species grouped into five families. Earthworms have been called ‘ecosystem engineers’; much like human engineers, they change the structure of their environments. Earthworms are very versatile and are found in nearly all terrestrial ecosystems. They play an important role in forest and agricultural ecosystems. This Soil Biology volume describes the various facets of earthworms, such as their role in soil improvement, soil structure, and the biocontrol of soil-borne plant fungal diseases. Reviews discuss earthworms’ innate immune system, molecular markers to address various issues of earthworm ecology, earthworm population dynamics, and the influences of organic farming systems and tillage. Further topics include the characteristics of vermicompost, relationships between soil earthworms and enzymes, the role of spermathecae, copulatory behavior, and adjustment of the donated sperm volume.

Earthworm Interactions with Soil Enzymes

As one of the dominant members of soil fauna, earthworms fulfill significant tasks in the soil ecosystem by participating in the physico-chemical processes of the soil, such as organic matter cycles, nutrient transformations, and modifications in soil structure. These processes are also directed by the activities and amounts of the enzymes produced by soil microorganisms that inhabit a wide range of soil environments including intestine systems, excretions, casts, and burrow linings of the earthworms. Therefore, microbial activity and the enzymes produced are considered to be closely related with earthworm life in soil. The purpose of this chapter is to describe the interactions between soil enzymes and earthworms at different levels in soil.

The Prospects of the Impact of Desertification on Turkey, Lebanon, Syria and Iraq

The prospective study area is 1.413.232 sq km and geographic coordinates are 30-42 latitude, 26-48 longitude, and includes Turkey, Lebanon, Syria and, Iraq (Mesopotamia). The relevant area is in arid, semi-arid and sub- humid areas (Black sea region).

Effects of Earthworms on the Availability and Removal of Heavy Metals in Soil

Earthworms originally evolved in aquatic ecosystems and began to colonize terrestrial ecosystems 600 million years ago. Over the past few decades, research into earthworms has revealed that they stimulate the physical, chemical, and biological properties of soil and hence enhance soil fertility. Recent works have revealed that earthworms are able to direct the fates of heavy metals by passing and accumulating toxic metals through and in their body tissues, and that this distinctive phenomenon is influenced by various factors.

Role of Plant Growth Promoting Bacteria and Fungi in Heavy Metal Detoxification

Heavy metals are found in nature and are the main component of a variety of enzymes, transcription factors, and other proteins. Excessive level of heavy metal is considered as a pollutant agent. Soil-heavy metals cannot be degraded biologically; they can only be transformed to organic complexes. Remediation techniques have high costs and low efficiency, whereas an alternative technique, phytoremediation has low cost and is environmentally friendly. To stimulate phytoremediation, fast-growing plants with high metal uptake and rapid and high biomass are required. Alternatively, soil microorganisms such as fungi and bacteria are used in heavy metal detoxification. This chapter reviews some recent advances in effect and significance of fungi and rhizobacteria in heavy metal detoxification.

Detoxification of Heavy Metals Using Earthworms

The number of different earthworm species living in a certain soil environment can be three or five and occasionally more than ten. Earthworms substantially enhance physical, chemical, and biological characteristics of soil through their feeding, casting, and burrowing activities. The factors affecting earthworm populations and activities in soil are climate, soil characteristics, plant vegetation, and biological relationships. The influences of earthworms on soil characteristics are mainly driven by their feeding, casting, and burrowing activities. Earthworms can affect either available or total metal concentrations in soil in that they have capability to accumulate heavy metals in their tissues and hence reduce their involvement in soil food chain. During their feeding activities, earthworms can change either available or total metal concentrations in soil in that they are capable to accumulate heavy metals in their tissues. The accumulation of heavy metals by earthworms is mainly associated with the factors such as type of mineral soil, organic matter content, and metal concentrations of their living environment and it should be kept in mind that earthworm–heavy metal relationships are mostly driven by soil characteristics and their ecological category.