IJERD – International Journal of Environmental and Rural Development (2023) 14-2

Research article
erdInfluence of Native Trees on Soil Fertility at a
Rainforestation Site in Mailhi, Baybay City, Leyte,
Philippines
LORRAINE CRISTY E. CENIZA
Visayas State University, Baybay City, Philippines

JIMMY O. POGOSA
Visayas State University, Baybay City, Philippines

MARLITO M. BANDE
Visayas State University, Baybay City, Philippines

VICTOR B. ASIO*
Visayas State University, Baybay City, Philippines
Email: vbasio@vsu.edu.phReceived 23 May 2023

Accepted 20 August 2023(*Corresponding Author)

Abstract The Philippines is one of the few countries in the world which was originally andthoroughly covered by rain forest. The conversion of natural forests to agricultural land uses
has led to land degradation. Soil is a vital resource for human survival in that it is the medium
in which most plants grow, it cleans and stores water, detoxifies pollutants, and plays a keyrole in the regulation of the Earth’s temperature. One of the intentions of rainforestation
farming (planting of native tree species) is to regenerate soil fertility. However, the effect ofnative forest trees on soil fertility is still poorly understood. Hence, this study was conducted
to evaluate the influence of native trees on the fertility status of the soil in Mailhi, Baybay
City, Leyte, Philippines. Two adjacent sites were evaluated and sampled. These were the 22year-old rainforestation farm and the nearby coconut plantation. At each site, a 20 m x 20 m
plot for sampling purposes was established which was divided into four parts. In each part,four (4) composite soil surface samples were collected from a soil depth of 0-20 cm using asoil auger. Each of the four composite samples came from three (3) subsamples. The
subsamples were mixed, and one-half kilogram was placed in properly labelled plastic bags
and brought for processing and laboratory analysis. Results revealed that the rainforestation
farm did not have an effect on water holding capacity and soil pH but significantly increased
the organic matter and total N contents of the soil, when compared with the nearby coconut
plantation. On the other hand, available P and exchangeable K were lower in the soil undernative tree species compared to the coconut plantation. The results indicate that indeed, thenative trees in the rainforestation site have caused important changes to the fertility status of
the soils.
Keywords rainforestation, native trees, soil fertility

INTRODUCTION
The Philippines is one of the few countries in the world that was originally and thoroughly coveredby rainforests (Schulte, 2002). In the past decades, forests were considered one of the most importantresources of Leyte Island. But after the conversion of part of Leyte's original forest vegetation tosecondary forest due to logging operations, kaingin or slash-and-burn cultivation, forest fire, andother natural phenomena such as pest diseases, and natural calamities, large parts of the upland areas
were colonized by farmers (Contreras-Hermosilla, 2000). The conversion of natural forests toagricultural land uses has led to land degradation.
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Asio et al. (2009) explained that soil is a vital resource for human survival in that it is themedium in which most plants grow, it cleans and stores water, detoxifies pollutants, and plays a keyrole in the regulation of the Earth’s temperature. Soil is also the habitat of a multitude of soilorganisms necessary for the cycling of elements and for keeping a healthy environment for humanbeings (Blum, 2007). Worldwide, soil resources are degraded at an unprecedented rate due to various
human activities. Soil degradation means the deterioration of soil properties to the extent that the soil
is no longer productive (Fullen and Catt, 2004).
The Philippines as one of the most severely deforested countries worldwide (Kummer andTurner, 994 as cited by Marohn, 2007), has officially adopted Rainforest Farming for its natural
governing program. As defined in the Memorandum Circular No. 2004-06 issued by the Departmentof Environmental and Natural Resources (DENR), rainforestation farming is a concept in forest
restoration, wherein only indigenous and endemic tree species are used as planting materials which
include but are not limited to dipterocarp species, premium tree species, etc. It is a kind ofreforestation whose aim is to preserve biodiversity expand Philippine forests and simultaneously
sustain human food production. One of the intentions of rainforestation farming is to regenerate soil
fertility. Asio and Milan (2002) reported that rainforestation farming is a helpful strategy to improvesoil quality.
Therefore, this study was conducted to focus on the effects of native trees as rainforestation
species on the nutrient status of the soil. Likewise, the study validated the hypothesis thatrainforestation farming improves the soil nutrient status.
OBJECTIVE
The objective of this study is to evaluate the influence of native trees as rainforestation species on
the fertility status of the soil and to determine the soil properties affected by planting native trees in
the marginal upland site in Mailhi, Baybay City, Leyte, Philippines.
METHODOLOGY
Sampling Site Selection
The field study was conducted in 2016 in the rainforestation site in Mailhi, Baybay City, Leyte (Fig.
1) about 23 km southwest of Baybay at 351 m asl elevation. A preliminary field survey was done toassess and select the sampling area. The rainforestation site was established twenty-two (22) years
ago in 1995.

Fig. 1 Location of the sampling site in Mailhi, Baybay City, Leyte, Philippines
Note: the location was a marginal upland under the coconut plantation before the rainforestation site was established.

Soil Collection and PreparationⒸ ISERD

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Two adjacent sites were selected. One is inside the rainforestation farm, and the other is under thecoconut plantation which is typical of the area. A 20 m x 20 m plot was measured and then divided
into four parts. In each part, four (4) composite soil surface samples were collected from the 0-20 cm
soil depth using a soil auger. Each of the four composite samples came from three (3) subsamples.
The subsamples were mixed, and one-half kilogram was placed in properly labelled plastic bags andbrought for processing and laboratory analysis.
Laboratory analysis includes soil physical properties such as particle size distribution using thehydrometer method (ISRIC, 1995), water holding capacity (Alef and Nannipieri, 1995), and soil
chemical properties such as soil pH analyzed potentiometrically using the soil-to-water ratio of 1:2.5(ISRIC, 1995), soil organic matter obtained using Loss of Weight on Ignition (Schlichting et. al,(1995), total nitrogen using Micro-Kjeldahl method (ISRIC, 1995), available phosphorus analyzed
using Bray 2 method (Bray and Kurtz, 1945) and exchangeable potassium using Metson method(Metson, 1956).
Data Encoding and Statistical Analysis
All data gathered were collated, encoded, and summarized using an electronic spreadsheet editor,
Microsoft Excel 2013. The data were analysed using the Statistical Package for Social Science (SPSS
version 20). The variability of the mean of soil properties was analysed using the one-way analysis
of variance (ANOVA). Moreover, in a case where significant variations at p≤0.05 were identified,
Tukey and Least Squares Differences (LSD) were carried out to compare means.
RESULTS AND DISCUSSION
Soil Physical Properties
Figure 2 shows the particle size distribution of the two sampling sites. Results revealed that in termsof particle size distribution, the soil in the rainforestation had clay and sand contents of 48.3 ±1.98 %and 35.2 ±1.40 %, respectively, while the soil in the coconut plantation had 31.61 ±1.98 % and 50.78±1.40 %, respectively (Fig. 2). The soil textural class was clay and sandy clay loam, respectively.
Based on the results of the statistical analysis, there was a significant difference (p≤0.05) between
the soils in the rainforestation and coconut plantation in terms of the sand and clay contents but nosignificant difference in the silt.

Note: Values with different superscript letters(a-b)
of particle size within the site are significantly
different at p≤0.05; N=32

Note: Values with a different superscript letter (a-b) of
WHC within the site are significantly different at
p≤0.05; N=32

Fig. 2 Particle size distribution of the soil
in rainforestation farm and coconut
plantation

Fig. 3 Water holding capacity in the soil in
rainforestation farm and coconut
plantation

Clays have a large specific surface, often predominantly negatively charged, that retains waterand nutrients. The clay itself may be a source of plant nutrients when it degrades. On the results,
rainforestation soil had higher clay content which indicates good water and nutrient retention.
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On the other hand, Fig. 3 reveals that the water holding capacity in the coconut plantation andthe rainforestation farm had average values of 93.19 ±3.02 % and 90.21 ±3.02 %, respectively. This
result suggests that the kind of land use has not yet influenced the water-holding capacity of the soil.
Soil Chemical Properties
Figure 4 shows slight variations in the pH of the soil. Results showed that the soils in therainforestation site and the coconut plantation had comparable pH values. This indicates that the kindof land use has not yet caused a significant change in the soil reaction.
Soil properties are usually improved when trees are grown due to the increase in surface soilorganic matter (Huxley, 1999). Organic matter refers to all decomposed, partly decomposed, andundecomposed materials of plant and animal origin (FAO, 2006).
Figure 5 shows that the soil in the rainforestation farm had higher organic matter content than
the soil in the coconut plantation (p≤0.05). The higher amount of OM of the rainforestation farm
could be due to its higher organic material addition in the form of litterfall than in the coconut
plantation. The amount of OM in the soil depends on the litter fall (leaves, twigs, bark, etc.)
contributed by trees as the primary vegetation in the area and the consequent losses through thedecomposition of these materials.

Note: Values with different superscript letters (a-b)
of soil pH within the site are significantly differentat p≤0.05; N=32

Note: Values with a different superscript letters (a-b)
OM within the site are significantly different at p≤0.05;
N=32

Fig. 4 Soil pH values of rainforestation
farm and coconut plantation

Fig. 5 Soil organic matter contents ofthe soils under rainforestation
farm and coconut plantation

Soil Nutrient Status
Figure 6 shows higher soil nitrogen content in the rainforestation farm than in the coconut plantation(p≤0.05). It agrees with the study of Atup (2016) where total N contents of the soils under coconut
plantation were low. Bande (2004) reported that during his study the soil in the rainforestation had
0.17% nitrogen content according to Landon (1991) the sufficiency ranges in soil, soils with values
within the range between 0.1-.20 classified as low, while the nitrogen content in the current study
had 0.24 ±.01 % classified as medium in sufficiency ranges in soil. The nitrogen content in the soilof rainforestation significantly improves. Apart from the application of N fertilizers, the main sourceof N in soils is the breakdown and humification of organic matter. The results on total N can therefore
be attributed to the higher OM content of the rainforestation farm compared to the coconut plantation.
The soil in the coconut plantation had a higher available P level compared to the soil in therainforestation farm (Fig. 7). The difference is significant at p≤0.05. This level of available P cannot
easily be explained since P fertilizer application is not being practiced by the coconut owner (Fig. 7).
This may be explained by the periodic burning that occurs in the coconut plantation. It is also possiblethat the cycling of P is faster in the coconut plantation. As coconut is burned, it produces ash whichⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2023) 14-2

is a residual material produced when it is burned for energy production. According to Erich (1991),
ashes were found to be more similar to conventional P fertilizer materials and the addition of coconut
ashes to the surface soil in the coconut can increase the availability of P.
As can be seen in Figure 7, available phosphorus in rainforestation farms is 6.97 ±1.08 mg kg-1
while, in coconut plantations, it is 11.66 ±1.08 mg kg-1. According to Landon (1991), the sufficiency
ranges in soil, soils with values within the range between 5-9 mg kg-1 are classified as low. However,the presently available phosphorus in the soil of the rainforestation is higher than the previous result
reported by Bande (2004) 3.4 mg kg-1 values range <5 classified as very low. This indicates animprovement in the availability of P due to the native trees.

Note: Values with different superscript letters (a-b)
of N within the site are significantly different at
p≤0.05; N=32

Note: Values with a different superscript letter (ab) of P within the site are significantly different at
p≤0.05; N=32

Fig. 6 Total N (%) of soils in therainforestation farm andunder coconut plantation

Fig. 7 Available P of the soil in therainforestation farm and undercoconut plantation

Note: Values with the different superscript letter a of K
within the site are significantly different at p≤0.05; N=32

Fig. 8 Exchangeable K of soils in the rainforestation farm and under coconut plantation
Figure 8 shows the average value of exchangeable potassium in the soils in the rainforestation
farm which is 30.57 ±36.74 mg kg-1. It is classified as very low available potassium in the soil basedon Landon (1991). On the other hand, the average value of exchangeable K in the soil under coconut
which is 104.16 ±36.74 mg kg-1 classified as medium in the sufficiency ranges in soil according toLandon (1991). In addition, Bande (2004) reported that the soil in the rainforestation during his study
had 130.5 mg kg-1 which is higher than the current available potassium. This may be explained thatduring the current study, some potassium is still in the leaves and the uptake of the potassium is slow,
while in the soil in the coconut plantation, the possible reason could be the periodic burning of thecoconut husk. Coconut husk ash will never totally replace K fertilizer; however, it can recycle a
substantial proportion of nutrients in a coconut plantation.
CONCLUSIONⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2023) 14-2

Planting native trees as rainforestation species has changed the fertility status of the soil after twentytwo (22) years from its establishment.
The results also revealed that the rainforestation farm when compared with the nearby coconut
plantation did not have an effect on water holding capacity and soil pH but significantly increased
the organic matter and total N contents of the soil. On the other hand, available P and exchangeable
K were lower in the soil under native tree species compared to the coconut plantation. However,based on the previous results of Bande (2004) rainforestation increased total nitrogen and available
P but decreased the exchangeable K of the soil.
ACKNOWLEDGEMENTS
We extend our gratitude to the Institute of Tropical Ecology and Environmental Management andthe Department of Soil Science, Visayas State University, Baybay City, Leyte, for the support forthis study. The authors would also express their sincere thanks to Professor Dr. Barry Noller and theInstitute of Environmental Rehabilitation and Conservation (ERECON) for financial support to thisstudy.
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