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Compared to moderate to high-intensity crown fires, the effects of low-intensity surface fires on soil characteristics have received relatively less research. The study was done in the Kota range of Ramnagar forest division situated in Ramnagar 55 km far from Nainital in Uttarakhand. A week after the fire and seven months later, in March 2021, soil samples were collected from burnt and unburned locations at two depths, 0-15 and 15-30 cm, respectively. The samples were examined to ascertain some soil chemical characteristics, including pH, total nitrogen, available phosphorus, and potassium. We used a two-way ANOVA analysis to examine the effects of fire and soil depth on each variable. Overall, the results showed that, except for a few variables that did not significantly vary with depth, soil chemical characteristics (pH, N, P, and K) significantly alter following surface fires in the research region. We concluded that surface fires significantly alter the characteristics of the soil but we also found out that if the soil is only affected by small-scale surface fire then some of the altered properties regain their normal values in some time. This work adds to our understanding of how fire affects soil characteristics in surface-fire ecosystems.

To study the forest soil properties that are most affected by surface fires.

Numerous studies, such as those by Schoch and Binkley (1986) and Fisher and Binkley (2000), claimed that although low-intensity fires can reduce the amount of nutrient pools, they can also boost soil fertility because they chemically transform nutrients trapped in dead plant matter.

Carter and Foster (2003) discovered that the impact of fire on nutrient productivity is related to fire intensity. They reported that while high-intensity fires (which are also more likely to be of high severity) tend to decrease site productivity, low-intensity fires can increase site productivity because the chemical nutrients from the burned vegetation are released, potentially creating an environment that is favourable for growth.

Other scientists and researchers also found the same conclusion as above when a fire affects a forest. From the above point of view, the soil properties are affected by fires whether it’s low or high-intensity fires

Study Area

Figure 1. Location of Kota range in Ramnagar Forest Division
Methodology
For the study of this paper, a random sampling method was carried out for determining the soil’s chemical properties (pH, Nitrogen, Phosphorous, and Potassium). A total of 20 samples were collected from the burnt site and unburnt site via two methods, zig-zag pattern and square box pattern. In a zig-zag pattern, we follow a zig-zag path and randomly collect samples, in the square box method a burnt and unburnt site has been chosen and then an imaginary square is formed. 4 samples were collected from all four corners and one sample is collected from the middle part.


These samples were collected after one week of fire (month of March 2021) and again after seven months in October 2021. Samples were analyzed in the district soil testing laboratory situated in Bhimtal, District Nainital, (Uttarakhand). The properties which were studied in the lab were soil pH, available Nitrogen, Phosphorous, and Potassium.

Soil pH was recorded by using pH meter adjusting pH = 4, pH = 7, pH = 10 by using buffer solution. Available Nitrogen was determined through the Potassium Permagnet method (Subbiah and Asija). Total phosphorus content was calculated by the method of Bray and Kurtz (Ülgen & Ateşalp, 1972). Potassium was calculated using an Automatic Absorption Spectrophotometer (AAS).

Mean values of top and lower soil properties are shown under the following tables and variations among the seasons are shown in charts.

Table 1. pH values recorded

Chart 1. pH values showing variation
Table 2. Available Nitrogen values 


Chart 2. Available Nitrogen Values showing variation
Table 3. Phosphorous values 


Chart 3. Phosphorous values showing variation
Table 4. Potassium values


Chart 4. Potassium values showing variation
According to ANOVA results of soil samples, surface fire affects all properties which were pH, Nitrogen, Phosphorous, and Potassium in top soil i.e. 0-6 cm below in a significant manner. While some properties were not significantly affected or not affected by the fire while we go down the soil depth i.e. 6-12 cm.
Table 5. The summary of two-way ANOVAs on the effect of fire and soil depth on chemical properties of soil. F values are shown for each factor for each analysis, and statistical significance of each factor in the model is given (ns, not significant; * P < 0.05; ** P < 0.01; *** P < 0.001, **** P < 0.0001)

According to the result analysis, we found out that there is a significant increase in the pH of soil after a fire. With pH, other properties which were studied are available Nitrogen, Phosphorous, and potassium. Study results indicated that soil Nitrogen and Potassium values are decreased but not in a very significant manner with depth. While Phosphorous is also decreased and showed significant changes like pH on topsoil.
 After the monsoon when second samples were collected from the same site, the values of some properties are recovered while some didn’t. Soil pH was recovered and came back to its slightly normal values. That may be because water content from rainfall help to reduce the alkalinity of the soil. Other properties like Nitrogen and Potassium were not changed even after the fire. While soil Phosphorous was not recovered fully from the fire. This may be because, during a fire, Phosphorous which is an organic matter may have been lost as gas or liberated as phosphate salts that are hardly soluble in the soil (Fisher and Binkley, 2000). 

In conclusion, we can say that surface fires are not severe but have significant effects on soil properties. Because surface fires may cause significant damage to the soil but these changes revert in one monsoon and soil regain its properties. This study showed that these types of fires may reduce or increase the soil properties but in a way they are beneficial to forest regeneration. The present research has some management considerations for surface-fire ecosystems like the mixed forests in our study region. First, in these ecosystems, prescribed fires can be utilized successfully without causing any soil damage to allow for the natural regeneration of dominant tree species or to lower fire danger by reducing fuel accumulation. Second, these fires destroy the top layer of flora at the moment of the incident but after regenerative growth, it is also beneficial for the fauna of the area too as it sometimes increases the soil fertility and helps to grow much more herbaceous vegetation. Third, since soil characteristics in these ecosystems do not significantly alter after a fire, management choices shouldn't involve human involvement on the burnt forest floor.

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