Mycorrhizae Applications in Sustainable Forestry

*Dayakar Govindu, Anusha Duvva and Srinivas Podeti*

## **Abstract**

Arbuscular mycorrhizal (AM) association is the most common symbiotic association of plants with microbes. AM fungi occur in the majority of natural habitats and they provide a range of important biological services, in particular by improving plant nutrition, abiotic resistance, and soil structure and fertility. AM fungi also interact with most crop varieties and forest plants. The possible benefit of AM fungi in forestry can be achieved through a combination of inoculum methods. The mycorrhizal inoculum levels in the soil and their colonization in different forest plant roots which leads to reduce the fertilizers, pathogen effects and fungicides and to protect topsoil, soil erosion, and water-logging. Currently, several reports were suggested that AM symbiosis can improve the potential for different plant species. Two steps could be used to produce high yielding of different plant biomass that would be both mycorrhizal dependency and suitability for sowing into the field with high inoculum levels Therefore, the wide-scale inoculation of AM fungi on forest trees will become economically important. The successful research is required in the area of mass production of AM fungal inoculum and AM fungi associated with roots which will contribute to sustainable forestry.

**Keywords:** mycorrhizae, sustainable forestry, mycorrhizal dependency, biomass

### **1. Introduction**

Arbuscular mycorrhizal fungi are ubiquitous soil microorganisms. AM fungi have great potential to increase plant growth and soil aggregate formation which improves soil quality and development of plant health [1] AM fungi and microorganisms in the rhizosphere contaminate roots and fabricate rich nutrients condition for plant development [2]. The advantage of AM growths in the field conditions with singular organisms is commonly identified with the rate and degree of mycorrhiza arrangement [3]. Management of AM fungi is required in forestry for high yielding and biomass production to be derived from economic and environmental conditions. Determining the magnitude of benefits from improved AM fungi management the three important factors are required. 1. Mycorrhizal dependency 2. Nutrient status of soil 3. Potential of AM fungal inoculum. The terrestrial plant roots develop AM fungi with natural resources of 80–90% symbiosis [4]. Global occurrence in forest ecosystems and form 50% of microbial biomass in the tropical ecosystem [5]. Among different important functions of the plant-fungal symbiosis, plant growth promotion activity is stimulated by the phosphorus uptake [6]. AMF increase nutrient uptake for the plants, particularly immobile nutrients such as phosphorus (P), copper (Cu), and zinc (Zn) in the soil which are not accessible to plant roots in normal condition due to slow immobility [7].

Moreover, AM fungi support tolerance to the plants from different environmental stresses such as salinity, drought, heat, and pollutants in the rhizosphere soil [8, 9]. Presently, effective management of AM fungi is possible by agronomic practices.

Mycorrhizal dependency (MD) is the most important in developing the management of crop plants and forest trees. Forest plant species derive profit from AM fungi to facilitate equally, another crop species is highly dependent on AM fungi for nutrition, biomass, and growth [10]. The most agricultural plants and forest tree species are hosts of AMF, not all benefit equally. The RFMD (relative field mycorrhizal dependency) proposed by Plenchette et al. [11] expresses the difference in dry biomass between mycorrhizal and non-mycorrhizal treatments as a percentage of the biomass of mycorrhizal treatment. This method is very useful in the ranking of different host plants with an individual experiment but absolutely the values of RFMD will depend on the nutrient status of the soil. Abbot and Robson [12] have suggested the need to assess the importance of AM to a host across a full range of soil P levels by determining the response curves for mycorrhizal and non-mycorrhizal plants.

In some forest soils, the response of some crop species to AM fungi is expressed as N as well as phosphate benefits [13]. AM inoculation did not significantly increase shoot dry matter of rice, but it produced significantly higher in biomass than the non-mycorrhizal ones.

A perusal of the **Table 1** reveals that all the 10 tree saplings have shown mycorrhizal infection. However, the percent of colonization varied with the tree species. Maximum colonization was observed in *Azadirachta indica* followed by *Albizia lebbeck, Gliricidia maculate.* Least colonization was observed in *Tamarindus indica.* The differences in infection are due to edaphic conditions and the age of the plant. With few exceptions, a direct correlation can be observed between the percent of mycorrhizal colonization and phosphorus content of the plants. Although the saplings with a high percent of colonization show high MD, there is no direct correlation between these two parameters. For instance, the *Leucaena leucocephala* with 78 colonization has shown more MD than *Azadirachta indica* with the highest AM fungal colonization. Thus it is obvious


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forests [27].

**2.1 Forest soils**

*Mycorrhizae Applications in Sustainable Forestry DOI: http://dx.doi.org/10.5772/intechopen.94580*

**2. Distribution of AM fungi in forestry**

that the extent of mycorrhizal colonization has no relation with MD. The plants even with moderate infection may also exhibit high Mycorrhizal dependency. Mycorrhizal

Forests play a progressively more crucial role in gathering the demand for timber and ecological protection, nearly 25% (one fourth) of India's total land area is now under forest land and tree cover. The diminishing soil quality is the main warning to sustainable forest management, mostly in planted forests. Microorganisms show significant functions in soil formation, aggregation nutrient cycling, nutrient uptake, and reclamation of ecosystems [15]. The arbuscular mycorrhizal fungi (AMF) form symbiotic associations by the plant roots of more than 80% of plants [16], and they play a crucial role in the successful organization and maintenance of plant communities [17]. AMF hyphae can add phosphorous (P), which cannot be absorbed by root hairs, and the AMF soil mycelial arrangement provides many profits to host plants [18] as well as plant growth promotion [19, 20] and development of plant resistance to abiotic stress and disease [21]. Additionally, AM fungi can be favorable to soil aggregation as the outcome of the activities of hyphae and glomalin protein secretion [22] therefore, the incidence and colonization of AM fungi would be helpful to the survival of forest seedlings and the sustainable managing of forests. Furthermore, the AM fungal species associated with plant species have elucidated different functions to host plants and influences on the distribution, diversity, and restoration of plant community [23]. The diversity of AM fungi is significantly important to forest ecosystems and can be important for plant community and productivity [24, 25]. Though, information about the diversity of AMF associated with tree species in forest plants is inadequate. It is a known fact the AM fungi are extensive in different ecosystems, and their colonization and spore propagules are also affected by soil physicochemical characteristics [26]. The abiotic

dependency of *Acacia nilotica* lowers as the P-level in soil was increased [14].

factors could influence on root colonization and fungal spore population.

**Table 2** reveals that AM fungal spore population was found highest in Kothagudem soil of *Albizia lebbeck*, while it was lowest in Godavarikhani soils of *Acacia nilotica*. The AM fungal spore population range was varying in the rhizosphere soils of Kothagudem followed by Yellendu, Bhopalpally, and Kothagudem. On other hand, rhizosphere soil showed a great variation in the incidence of different AM fungi both qualitatively and quantitatively. *Glomus* species was dominating in all the rhizosphere soils, followed by *Gigaspora* species was recorded highest in the rhizosphere of *Acacia nilotica* of Bhopalpally soil and it was least in Kothagudem. Similarly, *Sclerocystis* species was found highest in Kothagudem soil of *Acacia nilotica*, while it was least in Godavarikhani soil of *Acacia nilotica*. *Acaulospora* species was recorded highest in Bhupalpally and it was lowest in Godavarikhani soil. No *Acaulospora* species was observed in Godavarikhani and Yellandu the soils of *Albizia lebbeck*. *Scutellospora* was least in Godavarikhani and Bhupalpally soils. In the rhizosphere soils of the analyzed tree species, bountiful spore numbers, and high

decent varieties of AMF species were found (**Figure 1**) [28].

The AM fungi colonization and spore commune compositions in the rhizosphere of the tree species were estimated. The outcome of this study would provide close on the utilization and supervision of AM fungi to keep sustainable management of

#### **Table 1.**

*Mycorrhizal dependency of some foresty tree species saplings.*

*Mycorrhizal Fungi - Utilization in Agriculture and Forestry*

than the non-mycorrhizal ones.

**S. No. Plant species % of** 

4 *Hardiwikia* 

5 *Gliricidia* 

6 *Leucaena* 

7 *Acacia* 

8 *Azadirachta* 

9 *Tamarindus* 

*binata*

*macula*

*leucocephala*

*melanoxylon*

*indica*

*indica*

*Mycorrhizal dependency of some foresty tree species saplings.*

**colonization**

Moreover, AM fungi support tolerance to the plants from different environmental stresses such as salinity, drought, heat, and pollutants in the rhizosphere soil [8, 9]. Presently, effective management of AM fungi is possible by agronomic practices.

as N as well as phosphate benefits [13]. AM inoculation did not significantly increase shoot dry matter of rice, but it produced significantly higher in biomass

A perusal of the **Table 1** reveals that all the 10 tree saplings have shown mycorrhizal infection. However, the percent of colonization varied with the tree species. Maximum colonization was observed in *Azadirachta indica* followed by *Albizia lebbeck, Gliricidia maculate.* Least colonization was observed in *Tamarindus indica.* The differences in infection are due to edaphic conditions and the age of the plant. With few exceptions, a direct correlation can be observed between the percent of mycorrhizal colonization and phosphorus content of the plants. Although the saplings with a high percent of colonization show high MD, there is no direct correlation between these two parameters. For instance, the *Leucaena leucocephala* with 78 colonization has shown more MD than *Azadirachta indica* with the highest AM fungal colonization. Thus it is obvious

1 *Acacia nilotica* 67 0.20 0.30 0.12 0.20 170 2 *Albizia lebbeck* 88 0.80 0.90 0.60 0.70 240 3 *Albizia procera* 72 0.70 0.90 0.50 0.60 210

10 *Tectona grandis* 78 0.60 0.80 0.70 0.83 212

**P content (%) Mycorrhizal** 

**(MD) Mycorrhizal Non-mycorrhizal**

**Shoot Root Shoot Root**

76 0.50 0.70 0.23 0.28 196

80 0.70 0.80 0.30 0.40 215

78 0.60 0.80 0.31 0.70 213

71 0.40 0.40 0.20 0.26 183

90 0.90 0.90 0.71 0.80 253

54 0.10 0.10 0.09 0.12 104

**Dependency**

Mycorrhizal dependency (MD) is the most important in developing the management of crop plants and forest trees. Forest plant species derive profit from AM fungi to facilitate equally, another crop species is highly dependent on AM fungi for nutrition, biomass, and growth [10]. The most agricultural plants and forest tree species are hosts of AMF, not all benefit equally. The RFMD (relative field mycorrhizal dependency) proposed by Plenchette et al. [11] expresses the difference in dry biomass between mycorrhizal and non-mycorrhizal treatments as a percentage of the biomass of mycorrhizal treatment. This method is very useful in the ranking of different host plants with an individual experiment but absolutely the values of RFMD will depend on the nutrient status of the soil. Abbot and Robson [12] have suggested the need to assess the importance of AM to a host across a full range of soil P levels by determining the response curves for mycorrhizal and non-mycorrhizal plants. In some forest soils, the response of some crop species to AM fungi is expressed

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**Table 1.**

that the extent of mycorrhizal colonization has no relation with MD. The plants even with moderate infection may also exhibit high Mycorrhizal dependency. Mycorrhizal dependency of *Acacia nilotica* lowers as the P-level in soil was increased [14].
