Early Growth Comparison of the Fast-Growing Tree
Species in Mixed-Species Plantation Planted with Agroforestry and Biofertilization
Dede J. Sudrajat1*, Yulianti1,
Evayusvita Rustam1, Nurin Widyani1, Kurniawati P. Putri1,
Ratna Uli Damayanti1, Nurhasybi1, Eliya Suita1,
YMM Anita Nugraheni1 and Vivi Yuskianti2
1Research Center for Applied
Botany, National Research and Innovation Agency, Jl. Raya Jakarta-Bogor Km. 46,
Cibinong, Bogor, West Java, Indonesia
2Research Center for Ecology and Ethnobiology, National Research and Innovation
Agency, Jl. Raya Jakarta-Bogor Km. 46, Cibinong, Bogor, West Java, Indonesia
*For
correspondence: djsudrajatbtp@yahoo.com
Received 17 November 2023;
Accepted 14 February 2024; Published 18 March 2024
Abstract
This field study was conducted to evaluate the growth of mixed-tree
species plantation (Neolamarckia macrophylla, N. cadamba and Nauclea
orientalis) grown with different competitive ratio and land
equivalent ratio (LER) under different agroforestry
and biofertilization at Parungpanjang, Bogor, West Java and Indonesia. The
establishment of the mixed-tree species plantation used a randomized factorial
design with two factors, i.e., tree
species and agroforestry with biofertilization planted in 4 blocks. The results
showed the agroforestry using arbuscular mycorrhizal fungi (AMF) and compost
fertilization resulted the best tree growth of all tested three species.
However, the N. cadamba observed the highest plant height, diameter, volume
and crown width followed by N. orientalis and N. macrophylla. The
height of N. cadamba at the age of 3 years reached 10.87 m (84% higher
than the control) with the diameter of 13.43 cm (45% higher than the control),
followed by N. orientalis with the height of 9.27 m (69% higher than the
control) with the diameter of 12.71 cm (67% higher than the control) and N.
macrophylla with the height of 8.15 m (103% higher than the control) with
the diameter of 10.31 cm (100% higher than control). The competitive ability of
N. cadamba was higher than N. orientalis and N. macrophylla.
The sum of the partial LER of mixed-tree species plantation and partial LER of A.
galanga, had a value of >1 in all agroforestry and biofertilization.
This LER value showed that the mixed-tree species plantations with agroforestry
seemed a viable option to get higher profit. © 2024 Friends Science Publishers
Keywords: Agroforestry; Arbuscular mycorrhizal fungi; Inoculation; Competitive ratio; Tree growth
Introduction
Balancing demand for forest products and managing sustainable forest
ecosystems is one of the main problems currently faced by the forest sector
worldwide. Efficient plantation forest management and intensive silvicultural
practices are urgently needed to increase the success and productivity of
plantation forests (Alan 2020). In addition, forests must also
have ecological and social functions that allow them to go hand in hand. The
development of a mixed-tree species plantation with an agroforestry pattern
makes it possible to create tree stands with high diversity and productivity
and social functions for communities around the forest area. Several studies
showed the advantages of mixed-tree species plantation compared to pure
(monoculture) stands in terms of biomass production (Marron and Epron 2019),
soil fertility (Danise et al. 2020), nutrient cycling (Pardos et al.
2020) and carbon sequestration (Molina-Valero et al. 2021). Mixed-tree
species plantations are thus considered to be better than monocultures for
maintaining timber production while improving soil quality (Danise et al.
2021). Forests that are developed by involving high genetic variation both
within and among species can improve the stability of forest ecosystems and
increase their potential adaptation to global climate change (Hamrick 2004).
Establishment of a mixed-tree
species plantation is certainly more difficult than monoculture, especially in
site matching, species selection, and inter-specific competition (Manson et
al. 2013; Trogisch et al. 2021; Vanclay et al. 2022) with
management which are more complex (Dickinson et al. 2008), so that
operationally in the development of industrial plantation forests it is still
rarely carried out (Nichols et al. 2006; Vanclay et al. 2022).
Some experts recommend mixed-tree species plantations to be applied in the
development of community forestry (Chechina and Hamann 2015) and forest and
landscape restoration (Temperton et al. 2019). In this study, three fast
growing species from the Rubiaceae family were selected, i.e., Neolamarckia cadamba (Roxb.) Bosser, Neolamarckia
macrophylla (Roxb.) Bosser and Nauclea orientalis L. These three
species are native Indonesian species which are widely planted both on a large
scale (plantation) and on a small scale in the form of community forests
(Sarjono et al. 2017; Riany et al. 2018; Yuniarti et al.
2023) and is suitable for development with agroforestry patterns (Indrajaya and
Siarudin 2015; Saravanan 2019). However, mixed plantation forests with more
intensive silviculture between these three species have never been studied,
including their inter-specific competition.
In addition, intensive
silviculture has been applied to the establishment of industrial plantation
forests through soil preparation, use of high-quality seedlings, fertilization,
thinning, and pest and disease management (Alan 2020). Most of the fertilizers
used are chemical fertilizers. The application of biofertilizers such as
mycorrhiza on an operational scale for nurseries and silviculture for forest
tree species in Indonesia is still limited. In fact, mycorrhizae such as
arbuscular mycorrhizal fungi (AMF) have the ability to increase nutrient
uptake, produce phytohormones, and resistance to abiotic stresses, such as
drought, extreme temperatures, metals and salinity (Boyer et al. 2014;
Amiri et al. 2017; Ahammed and Hajiboland 2024). AMF inoculation on the
tree seedlings in the nursery can improve seedling vigor so that they are able
to adapt when planted in the field (Navarro-Garcia et al. 2011; Kumar et
al. 2017).
Thus, the development of
mixed-tree species plantations with agroforestry and biofertilization
treatments is expected to provide more effective land use values. One measure
to assess the land use value is the land equivalent ratio (LER) which is an
important tool used for evaluating agroforestry or polyculture systems (Dariush
et al. 2006; Mohammed 2012). LER is defined as the relative area of land
required by a single crop (monoculture) to produce the same yield when planted
with an agroforestry or polyculture system (Mohammed 2012). The hypothesis in
the research seeks to ensure that mixed-tree species plantations with
agroforestry using biofertilizer can be implemented and is profitable, so the
purpose of this study was to: (1) examine the growth of mixed-tree species
plantation (N. cadamba, N. macrophylla and N. orientalis),
(2) assess the competitive ratio of the plantation and (3) calculate the LER in
different agroforestry with biofertilization (AMF and compost) at Parungpanjang,
Bogor, West Java and Indonesia.
Materials and Methods
Materials
The study was carried out at the mixed-tree species plantation stand at
Parungpanjang, Bogor, West Java, Indonesia. The stand was established using
three species from Rubiaceae family, i.e.,
N. macrophylla, N. cadamba and N. orientalis. The seeds were
collected from Luwu Timur-South Sulawesi (3ş15’22” S, 120°12’48” E) for N. macrophylla,
Pomalaa-Southeast Sulawesi (4°00’94” S, 121°30’09” E) for N. cadamba,
and Parungpanjang-Bogor (6°23’09” S, 106°31’14” E) for N. orientalis. The seeds were processed at the Seed
Testing Laboratory, Center for Standard and Instrument Implementation of
Forestry and Environment, Bogor.
AMF preparation
The AMF strains were explored from nature forest in PT. Tanjung Redeb
Hutani, East Kalimantan (02°10'20" N, 117°28'15" E) and isolated in
Laboratory of PT. Inagro, Bogor, West Java (https://inagro.co.id). AMF spores
were extracted from 100 g of rhizosphere soil of trees with the best and
healthy phenotypes using the wet filter pour and centrifugation method
(Brundrett et al. 2008). The number of each type of spore that was
successfully extracted from each type of host was calculated. The spores chosen
for identification are spores with complete structures. Identification
was carried out based on the identification key of Schenck and Perez (1990) in
genus level. Making a single spore culture refers to the method used by
Mansur (2000), i.e., the Petridish
Observation Chamber (PDOC) with modifications. Culture propagation is carried out
by planting a propagation medium (zeolite) with a cover crop (Pueraria
javanica) so that sufficient pure culture is obtained to test the
effectiveness of several types of desired plants. If the results obtained show
a positive trend, the isolate will be multiplied for production. The AMF used in this study was a mixture of several AMF strains (Glomus
sp.-1, Glomus sp.-2, Acaulospora sp. and Gigaspora sp.
number of spores 626 per gram).
Seedling preparation and planting design
Seedlings were raised in the nursery at Nagrak Research Station, Bogor
(06°6'74'' S, 106°51'27'' E). Seeds were sown in mixed media of compost, sand,
and charcoal (3: 5: 1, by volume). After two months of age, seedlings with a
pair of leaves that grow normally are transferred to polybags with mixed media
of topsoil, rice husks, and compost (3:2:1, by volume) (Sudrajat et al.
2016; Sudrajat et al. 2019). AMF inoculation was carried out when
transplanting seedlings from the germination box into polybags containing the
media by adding 5 g of AMF to each seedling. Seedlings are maintained in the
nursery for 4 months and are ready to be planted in the field test. The results
of the analysis of the percentage of inoculation on the seedlings showed that
the inoculation level on N. macrophylla seedlings ranged from 36.7–43.3%,
N. cadamba ranged from 40.0–50.0% and N. orientalis ranged from
46.7–63.3%.
Planting test was carried out at
the Parungpanjang, Bogor, West Java and Indonesia (06°20’42” S, 106°06’15” E, altitude 52 m asl.).
Soil was categorized as podzolic haplic with low pH and low nutrient content
(C-Organic = 1.20–2.31%, N-total = 0.22–0.24%, P = 0.88–13.75 ppm, K = 0.10–0.15
cmol(+) kg-1, Ca = 2.30–4.98 cmol(+) kg-1,
Mg = 1.80–3.47 cmol(+) kg-1,) and pH 4.46–4.61 (Anna et
al. 2020). Planting of mixed-tree species (N. macrophylla, N. cadamba
and N. orientalis) was conducted by spacing of 4 m x 2 m at the planting
hole size of 30 cm x 30 cm x 30 cm. The tree planting path for each species
runs from east to west (Fig. 1). The design used to develop mixed-tree species
plantation was a factorial randomized design with two treatment factors, i.e., tree species (three species) and
agroforestry with biofertilization planted in 4 blocks (replications). The
treatments were: (1) control (no agroforestry and no biofertilization), (2)
agroforestry, (3) agroforestry using the inoculated AMF inoculated seedling,
(4) agroforestry pattern with 3 kg compost fertilization, and (5) agroforestry
using the AMF inoculated seedling and 3 kg compost fertilization.
The compost (manure and rice
husk compost) has the following characteristics and chemical content: pH 8.09, C
organic 22.49%, N 0.84%, P 0.26 ppm, K 0.53 cmol(+) kg-1 and C/N ratio 26.77. Compost fertilization was carried out 3 times, i.e., at the time of out planting as a
basic fertilizer (3 kg), at the age of the trees 12 months after out-planting
(3 kg), and 24 months after out-planting (3 kg). The second and third
fertilization has been done by loosening the soil around the tree with a
diameter of 80–100 cm and adding compost to the area. The annual crop chosen in
this agroforestry pattern was Alpinia galanga with a spacing of 100 cm ×
50 cm (Fig. 1). Planting of A. galanga was carried out after the tree
species. The planting of the three tree and crop species was also carried out
using a monoculture pattern as a comparison for calculating the competition
ratio and land equivalent ratio.
Measurement of growth and competitive ratio
The growth was measured on the tree height and diameter carried out at
the age of trees 1, 2 and 3 years. Height measurement was carried out using a
scaled pole, while diameter measurement (diameter at breast height) was carried
out using a diameter measuring tape. In addition, measurements of crown width
and tree volume were also carried out. Crown width was measured by considering
the widest and narrowest crowns and averaged to obtain the crown width. Tree
volume (Vt) is only measured at the age of 3 years using the following
formula (Saputra et al. 2019):
(1)
Where: Vt = tree volume, p = 3.14; D = diameter at
breast heigh (m); H = total height (m); f = form factor (0.7).
Competitive ratio between tree
species in mix-species plantations based on tree volume at 3 years of age.
Competitive ratio calculation is done by comparing two tree species and each
tree species is compared with a different tree species so that 6 pairs are
formed in comparison to the competitive ratio of the three tree species. The
formula used in calculating the competitive ratio adopts Ceunfin et al.
(2017):
(2)
Dimana: Ya = tree volume of species a in the mix-species
plantation, Yb = tree volume of species b in the mix-species plantation,
Yaa = tree volume of species a in monoculture plantation, Ybb =
tree volume of species b in monoculture plantation, Zb = proportion of
species b in the mix-species plantation, Za = proportion of species a in
the mix-species plantation.
Calculation of LER
Measurement
of agroforestry land productivity between mixed tree (N. macrophylla, N.
cadamba and N. orientalis) stands and crop species (A. galanga)
was carried out by calculating tree volume and crop
production data in planting test demonstration plots and compared with tree
volume and crop production data planted in monoculture. Measurement of A.
galanga production was carried out by weighing the weight of fresh tubers
in each year of production with a total of 25 plants taken at random which were
converted into production per unit of land (ton ha-1). Determination
of tuber production per unit of land (hectare) was done by calculating the
average production per clump multiplied by the number of A. galanga
plant populations for each hectare with a spacing of 100 cm × 50 cm. Meanwhile,
the measurement of the productivity of tree stands was carried out for all
plants (census) in the planting test area. Timber production per unit of land
(hectare) was determined by calculating the average volume per tree multiplied
by the number of trees per hectare and the percentage of survival in each year
of observation. The increase in timber production from tree species was the
difference in the volume of wood per hectare measured at the beginning of the
year and the end of the year (annual volume growth). The LER calculation uses a
formula adopted from Dariush et al. (2006) and Figyantika et al.
(2020) as follows:
(3)
Notes: Pa
= yield of galangal (A. galanga) tubers cultivated by agroforestry
pattern, Pb = production (tree volume) of N. macrophylla grown by
polyculture, Pc = production (tree volume) of N. cadamba grown by
polyculture, Pd = production (tree volume) of N. orientalis grown
by polyculture, Ma = yield of galangal (A. galanga) tubers
cultivated by monoculture, Mb = production (tree volume) of N.
macrophylla grown by monoculture, Mc = production (tree volume) of N.
cadamba grown by monoculture, Md = production (tree volume) of N.
orientalis grown by monoculture, n = plant or tree age.
Fig. 1: Planting design of
mixed-tree species plantation with agroforestry Alpinia galanga and
biofertilizer treatments (a), and
tree growth performance at 1 year old age (b).
Notes: N c = Neomarckia cadamba, N o = Nauclea orientalis, N m = Neolamarckia
macrophylla
Table 1: Recapitulation of analysis of variance of influences of species and
silvicultural treatment on survival, height, diameter at breast height, volume,
and crown width of N. macrophylla, N. cadamba and N. orientalis
at 3 years of age
Sources of variation |
DF |
Survival (%) |
Height (m) |
Diameter (cm) |
Volume (m3) |
Crown width (m) |
Block (B) |
2 |
- |
2.38ns |
2.77ns |
1.49ns |
19.31** |
Species (S) |
2 |
65.51** |
135.86** |
110.03** |
86.67** |
70.68** |
Block (B)*Species (S) |
4 |
- |
0.84ns |
1.68ns |
0.89ns |
8.75** |
Silviculture treatment (ST) |
4 |
30.20** |
204.46** |
89.16** |
68.44** |
275.89** |
B*ST |
8 |
- |
1.24ns |
0.15ns |
0.12ns |
5.79** |
S*ST |
8 |
2.71 * |
8.86** |
6.44** |
5.22** |
29.83** |
B*S*ST |
16 |
- |
0.60ns |
0.76ns |
0.44ns |
4.07** |
Notes: ** = significant at 99% confidence level, * = significant at 95%
confidence level, ns = not significant at 95% confidence level
Fig. 2: Tree survival of N. cadamba, N.
macrophylla and N. orientalis in the agroforestry using AMF
inoculated seedling and compost fertilization treatment. Notes: ST-1 = non
agroforestry, ST-2 = agroforestry, ST-3 = agroforestry using AMF inoculated
seedling, ST-4 = agroforestry with 3 kg of compost per year, ST-4 =
agroforestry using AMF inoculated seedling and fertilization of 3 kg of compost
per year
Data analysis
Data were analyzed using analysis of variance to examine the effect of
different treatments (tree species and agroforestry with biofertilization) on
the growth of tree height, diameter and volume. Duncan's multiple range test
was carried out if the results of the analysis of variance of a treatment or
its interaction have a significant effect on an observed parameter. Competitive
ratio and land equivalent ratio data are tabulated and described to obtain an
overview of the treatment with the highest ratio.
Results
Growth performance
Species, agroforestry with biofertilization, and their interactions had
a significant effect on tree survival up to 3 years old. The interaction
between species and agroforestry with biofertilization had a significant effect
on tree height, diameter, volume, and crown width. Most of the block effects
had no significant effect on the growth of the three tree species tested,
except for the crown width parameter (Table 1). This shows that the planting
test blocks are relatively uniform.
The agroforestry
and AMF
inoculated seedling and 3 kg compost per year until 2 years of tree
age gave the highest survival rate for the three tree species tested (Fig. 2).
In general, N. orientalis had the highest survival. In the best
treatment, agroforestry and AMF inoculated seedling
and fertilization with 3 kg compost per year, N. orientalis had the
highest survival (98.3%), followed by N. cadamba (96.6%), and N.
macrophylla had the lowest survival (78.3%). In areas that did not apply an
agroforestry system, the survival of N. macrophylla also gave the lowest
value (46.6%) compared to the other two species. The highest mortality rate
occurred in the first year or during the adaptation phase of the seedlings. The
treatment of agroforestry and biofertilization with AMF inoculated seedling and
3 kg of compost per year also gave the best height and diameter growth for all
species. N. cadamba had higher growth in height and diameter compared to
other species, while N. macrophylla has the lowest growth. The N.
cadamba height of a 3-year-old planted with an agroforestry using AMF
inoculated seedling and 3 kg of compost per year reached the tree height of
10.87 m (84% higher than control) with the tree diameter of 13.43 cm (45%
higher than control), followed by N. orientalis with the height of 9.27
m (69% higher than control) with the tree diameter of 12.71 cm (67% higher than
control), and lastly N. macrophylla with the tree height of 8.15 m (103%
higher than control) with the diameter of 10.31 cm (100% higher than control) (Fig.
3).
The trend of tree volume at 3
years of age followed the growth trend in height and diameter with the
treatment that produced the highest tree volume obtained from the agroforestry
pattern using AMF inoculated seedling and 3 kg compost per year. In this
treatment, N. cadamba produced a tree volume of 0.1126 m3,
followed by N. orientalis with a tree volume of 0.0881 m3,
and finally N. macrophylla with a tree volume of 0.0501 m3.
Statistically, for several parameters such as tree height, diameter, and volume
of N. cadamba and N. orientalis, the treatment of agroforestry
using AMF inoculated seedling and 3 kg compost per year using the agroforestry pattern was not significantly
different from the treatment of agroforestry with fertilization of 3 kg compost
per tree per year. For crown width, the best treatment for each species was
obtained by agroforestry pattern using AMF inoculated seedling and 3 kg of
compost per year using an agroforestry pattern. In this treatment, the crown
width of N. cadamba, N. macrophylla and N. orientalis were 10.52
m, 7.98 m and 6.89 m, respectively (Table 2). Visually, the crowns of N.
orientalis tend to be heavier and denser.
In mix-tree species plantations,
there is inter-specific competition which is planted in intermittent row
patterns. Based on the competitive ratio, N. cadamba has a better
competition value than N. macrophylla. The same thing was shown by N.
orientalis which had a higher competition ratio than N. macrophylla.
When comparing N. cadamba and N. orientalis, N. cadamba
has competitive advantages in control, agroforestry, and agroforestry using AMF inoculated seedling. In more intensive conditions, the treatment of
agroforestry with the fertilization of compost 3 Table 2: Tree volume and crown width of N.
cadamba, N. macrophylla and N. orientalis on the agroforestry using
AMF inoculated seedling and compost fertilization treatment at Parungpanjang,
Bogor
Species |
Agroforestry and biofertilization treatments |
Tree volume (m3) |
Crown width (m) |
N. macrophylla |
ST-1 |
0.0115 g |
3.20 g |
ST-2 |
0.0230 fg |
4.22 ef |
|
ST-3 |
0.0337 def |
4.98 de |
|
ST-4 |
0.0473 cde |
4.37 e |
|
ST-5 |
0.0501 cd |
7.98 b |
|
N. cadamba |
ST-1 |
0.0313 defg |
4.38 e |
ST-2 |
0.0611 c |
4.83 de |
|
ST-3 |
0.0858 b |
6.61 c |
|
ST-4 |
0.1108 a |
8.44 b |
|
ST-5 |
0.1126 a |
10.52 a |
|
N. orientalis |
ST-1 |
0.0113 g |
3.57 fg |
ST-2 |
0.0215 fg |
6.35 c |
|
ST-3 |
0.0219 efg |
5.16 d |
|
ST-4 |
0.0820 b |
5.34 d |
|
ST-5 |
0.0881 b |
6.89 c |
Notes: ST-1 = non agroforestry, ST-2 = agroforestry, ST-3 = Agroforestry
using AMF inoculated seedling, ST-4 = agroforestry with fertilization of
compost 3 kg per year, ST-4 = agroforestry using AMF
inoculated seedling and compost fertilization treatment
Table 3: Competitive ratio between N. cadamba, N. macrophylla and N.
orientalis on the mix-tree species plantation at the 3 years old age at Parungpanjang,
Bogor
Treatments |
Nm to Nc |
Nm to No |
Nc to Nm |
Nc to No |
No to Nm |
No to Nc |
Control |
0.57 |
0.71 |
1.75 |
1.24 |
1.41 |
0.81 |
Agroforestry |
0.82 |
1.00 |
1.22 |
1.22 |
1.00 |
0.82 |
Agroforestry using AMF inoculated seedling |
0.53 |
0.76 |
1.87 |
1.43 |
1.31 |
0.70 |
Agroforestry with
compost fertilization treatment |
0.65 |
0.51 |
1.53 |
0.78 |
1.97 |
1.29 |
Agroforestry using AMF
inoculated seedling and compost fertilization treatment |
0.83 |
0.64 |
1.20 |
0.77 |
1.56 |
1.30 |
Notes: Nm = Neolamarckia macrophylla, Nc = Neolamarckia
cadamba, No = Nauclea orientalis
Table 4: Land equivalent ration (LER) of mixed-tree species plantation with
agroforestry using Alpinia galanga at the tree age of 1, 2 and 3 years
Tree age |
Treatments |
Partial LER of mix-tree
species plantation |
Partial LER of Alpinia galanga |
LER total |
1 year |
Agroforestry |
0.62 |
0.86 |
1.48 |
Agroforestry
using AMF inoculated seedling |
0.72 |
1.58 |
||
Agroforestry
with compost fertilization treatment |
1.34 |
2.20 |
||
Agroforestry
using AMF inoculated seedling and compost fertilization treatment |
1.82 |
2.68 |
||
2 years |
Agroforestry |
1.09 |
0.75 |
1.92 |
Agroforestry
using AMF inoculated seedling |
1.03 |
1.85 |
||
Agroforestry
with compost fertilization treatment |
1.66 |
2.53 |
||
Agroforestry
using AMF inoculated seedling and compost fertilization treatment |
2.10 |
2.98 |
||
3 years |
Agroforestry |
1.29 |
0.59 |
1.87 |
Agroforestry
using AMF inoculated seedling |
2.15 |
2.72 |
||
Agroforestry
with compost fertilization treatment |
3.35 |
3.90 |
||
Agroforestry
using AMF inoculated seedling and compost fertilization treatment |
3.87 |
4.41 |
kg, and agroforestry using AMF
inoculated seedling and fertilization of compost 3 kg, N. orientalis has
a higher competitive ratio than N. cadamba (Table 3).
Land equivalent ratio (LER)
Total LER, which is the sum of the partial LER of mix-tree species
plantation and partial LER of A. galanga, had a value of >1 in all agroforestry
and biofertilization (Table 4). The range of LER values for trees aged 1, 2,
and 3 years were 1.48–2.68, 1.92–2.98 and 1.87–4.41, respectively. At the age
of 1 year, the partial LER of mix-tree species had a value of >1 in the
compost fertilization (1.34) and the AMF inoculated seedling and compost
fertilization treatment (1.82), while at the age of 2 and 3 years, the partial
LER of mix-tree species plantation had LER> 1 in all agroforestry and
biofertilization, with a range of 1.03–3.87. The partial LER of A. galanga
tends to decrease with increasing tree age. The highest total LER value was
obtained by treatment with AMF inoculated seedling and compost fertilization (3
kg per year) with LER values in years 1, 2 and 3 were 2.68, 2.98 and 4.41,
respectively.
Discussion
Growth performance (tree survival, height, diameter, stem volume, and
crown width) of the three species was strongly influenced by agroforestry and
biofertilization treatments. The application of agroforestry and
biofertilization can improve tree survival and growth. The growth of the three
species, i.e., N. macrophylla, N. cadamba and N. orientalis,
increased with increasing biofertilization. The agroforestry using AMF inoculated seedling and 3 kg compost
fertilization gave the highest of tree survival, height, diameter and the
biggest of tree volume and crown width. In several previous studies, the
application of agroforestry was able to improve tree growth, as reported by
Supriono and Setyaningsih (2012) on T. grandis, Lucena et al.
(2023) on Khaya ivorensis and Souza et al. (2023) on Bertholletia
excelsa. Studies on the effectiveness of AMF inoculation on increasing
growth and adaptation of seedlings have been reported in several plant species,
especially agricultural plants. AMF can increase nutrient and water absorption,
as well as produce phytohormones, such as auxin, which can stimulate plant
growth and development (Ahammed and Hajiboland 2024). AMF can assist host
plants in improving tolerance mechanisms and preventing downregulation of key
metabolic systems (Begum et al. 2019). In this study, the use of a
mixture of AMF strains was quite suitable and effective in associating with the
root systems of the three species tested, as indicated by the high average
percentage of colonization, i.e., N.
macrophylla 41.1%, N. orientalis 54.4% and N. cadamda 44.4%.
O'Connor et al. (2001) stated that the colonization percentage reaches a
high level if damage is > 30%. Likewise, the adaptability (survival) and
growth of the three trees showed that the trees originating from AMF inoculated
seedlings were relatively better than the control. The use of mixed AMF species
has also been reported by Jansa et al. (2008); Wehner et al.
(2010) and Shukla et al. (2014) is more effective compared to
applications using individual AMF species.
Some study also reported the
positive effect of fertilization on the tree growth (Subedi et al. 2015;
Tumushime et al. 2019; Anwar et al. 2020). Jaquetti and Gonçalves
(2021) stated that fertilization is fundamental during the early growth (stage)
of forest plantation development. According to Lucena et al. (2023), a
combination of agroforestry systems with silvicultural interventions
(biofertilizer treatment) can increase the ecological and economic values of
the tree plantation.
In this research, a mix-tree
species plantation with three fast growing tree species from the Rubiaceae
family had different adaptations and growth. In the best treatment
(agroforestry using AMF inoculated seedling and 3 kg compost fertilization), N.
orientalis had the highest tree survival, followed by N. cadamba and
N. macrophylla with the lowest tree survival. For its growth, N.
cadamba had the highest height, diameter, stem volume, and crown width.
When viewed from its natural distribution pattern, N. orientalis has a
wide natural distribution (Riany et al. 2018), as well as N. cadamba
which has a wide distribution and is found throughout the major islands of
Indonesia (Sudrajat 2016). The broad description of natural seismicity is
thought to be related to its adaptability. In contrast to N. macrophylla
which is only found in eastern Indonesia, i.e., Sulawesi, the Maluku Islands
and Papua (Halawane et al. 2011; Yuniarti et al. 2023), it is
thought that its adaptability is relatively lower. In addition, the diversity of
N. cadamba is thought to be wider than that of N. macrophylla.
Several studies showed that N. macrophylla had low to moderate genetic
diversity, with values of He = 0.05–0.42 and Gst = 0.083
(Andriani 2017; Larekeng et al. 2018; Arif et al. 2019), while N.
cadamba showed relatively wider genetic diversity, with He = 0.2756
(0.1489–0.3339) and Gst = 0.2707 (Sudrajat et al. 2015). The
wider natural distribution and genetic diversity is thought to be related to
the adaptability of each species, especially on marginal lands such as in this
research location (Parungpanjang, Bogor). This adaptability also affected its
performance in the form of mixed-tree species plantations.
Mixed-tree species plantations
planted using an agroforestry pattern have several advantages such as providing
a variety of products (biodiversity, timber, and non-timber) compared to
pure-species plantations (Montagnini et al. 2003), being more adaptive
to local site conditions and being more beneficial for ecological balance, and
can mitigate the risk of natural hazards (Griess and Knoke 2011), has higher market and social value for local
communities (Ball et al. 1995). However, on an operational scale for
commercial or industry, mixed-tree species plantations are still rarely
practiced because management is more difficult (Nichols et al. 2006),
potential production benefits are not always realized (Kelty 2006), and little
is known about interactions and competition between species, especially for
tropical native tree species.
In this study, the competition
ratio (CR) for each species has different values. CR is an estimate of the
relative competitive ability of a tree species against other tree species. CR
is related to the ability of each species to obtain resources both vertically
and horizontally (Paulus 2005; Ceunfin et al. 2017). In this study, the
CR of N. cadamba against N. macrophylla had a higher value
compared to the opposite CR value (N. macrophylla against N. cadamba).
This indicated that the competitiveness of N. cadamba was higher than
that of N. macrophylla. Likewise with N. orientalis against N. macrophylla
which has a high CR. N. cadamba also had
a higher CR than N. macrophylla in the control treatment, agroforestry
patterns, and agroforestry patterns with NPK fertilization, so that the highest
adaptability was N. cadamba, N. orientalis, and N. macrophylla, respectively.
However, in the treatment of the agroforestry with compost fertilization and
the agroforestry using AMF inoculated seedling and compost fertilization, the
CR values for N. orientalis showed higher results, so that the order of
competence in these conditions was N. orientalis, N. cadamba and N.
macrophylla.
To compare the effectiveness of
land use in an agroforestry (mixed cropping pattern) with a monoculture pattern,
the LER was calculated based on the productivity of each commodity species (Dariush
et al. 2006; Figyantika et al. 2020). The LER value is equal to 1
(one) indicating that there is no difference in results between the
intercropping or polyculture system and the monoculture system. Meanwhile,
every LER more than 1 (one) will show the benefits of an
intercropping/polyculture management system and every LER below 1 (one) shows
the benefits of monoculture system management (Lehmann et al. 2020). The
interaction between plants planted using an agroforestry pattern on a land has
a positive impact on each of its components, and this will affect plant
productivity. Productivity measurement for mix-tree species plantations was
based on growth shown in the tree stand volume value, while for crop species it
was calculated based on the production of tubers. The total LER values for
mixed-tree species plantation aged 1, 2 and 3 years showed a range of 1.48–2.68,
1.92–2.98, and 1.87–4.41, respectively, with the highest total LER values
produced by the agroforestry using AMF inoculated seedling and 3 kg compost
fertilization. The data showed that a mixed crop pattern combined with crop
species provides higher productivity than if planted in monoculture. Similar
research result was reported by Narendra and Nandini (2013), who stated that
the productivity of a species will increase if it is planted in polyculture or
agroforestry with fertilizer treatment, such as teak (T. grandis) which
is planted in agroforestry with corn and peanuts. In this study, LER partial
mix-tree plantation species tended to increase with fertilizer treatment and
increasing tree age. Studies on other species planted using agroforestry show
that the combination of orange, patchouli and papaya in an agroforestry pattern
has a total LER value of 1.783 (Setiawan and Himawan 2018). This illustrates
that the application of agroforestry provides better growth in good growth,
especially for woody plants or trees and provides higher land use efficiency.
A. galanga cultivation planted in stands of mixed-tree species from the Rubiaceae
family (N. cadamba, N. macrophylla and N. orientalis) showed a
decrease in LER from 1 year to 3 years of age. The partial LER values of A.
galanga at 1, 2, and 3 years of age were 0.86, 0.75, and 0.59,
respectively. This value shows that the productivity of A. galanga
tubers decreased after the main plants (N. cadamba, N. macrophylla and N.
orientalis) increased in size. The decrease in productivity of A.
galanga tubers was not optimal because the shade from the tree crown or
canopy widens with age. The range of crown widths for the three tree species in
all treatments at 3 years of age was 3.20–7.98 m (N. macrophylla), 4.38–10.52
m (N. cadamba), and 3.57–6.89 m (N. orientalis). The wide canopy
causes obstruction of sunlight received by A. galanga, so that the
production of A. galanga tubers was less than optimal. Similar results
were reported by Sudrajat et al. (2023) on arrowroot (Maranta
arundinacea) planted under tree stands of Falcataria molucana aged
1, 2 and 3 years, the biomass of the tubers tended to decrease as the age of
the trees increased. Figyantika et al. (2020) also reported on
agroforestry patterns between Acacia auriculiformis with soybeans and
corn in the Gunung Kidul (Indonesia) which stated that the larger the A.
auriculiformis, the LER value of the crop species (soybeans and corn)
decreased. The decrease in light received by crop species as well as
competition for water and nutrient absorption is the cause of the decline in
crop plant productivity (Figyantika et al. 2020). In this study, the
decrease in light intensity under mixed-tree species plantation at 1, 2 and 3
years was 59.61, 34.53 and 25.17%, respectively. In general, the agroforestry
pattern between mixed-tree species and A. galanga in this study showed
an LER value of > 1. This shows that the agroforestry system is very
suitable and applicable. According to Desmiwati et al. (2021), the
contribution of crop species (A. galanga) to farmers' income in the same
location, i.e., Parungpanjang, Bogor
reached 15.8% of their total income per year. In addition, LER > 1 indicates
that a monoculture crop system requires a larger area of land compared to an
agroforestry pattern, so that the agroforestry system can be declared more
efficient in land use (Ceunfin et al. 2017).
Conclusion
The growth of the three species, i.e.,
N. macrophylla, N. cadamba and N. orientalis increased with
increasing fertilization intensity. The agroforestry using AMF inoculated
seedling and 3 kg compost fertilization gave the highest of tree survival,
height, diameter, and the biggest tree volume and crown width. The competitive
ratio of the three species in plantation conditions without agroforestry, with
agroforestry, and agroforestry using AMF inoculated seedling was N. cadamba >
N. macrophylla > N. orientalis. In more intensive conditions, i.e., agroforestry with compost
fertilization and agroforestry using AMF inoculated seedling and 3 kg compost
fertilization, the competition ability of the three species was N.
orientalis > N. cadamba > N. macrophylla. The range of
LER values (sum of the partial LER of mixed-tree species plantation and partial
LER of A. galanga) for trees aged 1, 2 and 3 years were 1.48–2.68, 1.92–2.98
and 1.87–4.41, respectively. This LER value >1 showed that the agroforestry
system in mixed-tree species plantations was more effective in land use.
Acknowledgements
The authors wish to acknowledge BRIN and LPDP (Lembaga Pengelola Dana Pendidikan)-Ministry of Finance, Indonesia for their financial assistance under the RIIM (Riset dan Inovasi untuk Indonesia Maju) Batch 2 Research Grant 2022–2023.
Author Contributions
Each
author (DJS, Y, ER, NW, KPP, RUD, N, ES, D, YMMAN,
and VY) equally contributed as main contributors to the design and
conceptualization of the manuscript, performed the analysis, prepared the
initial draft, and revised and finalized the manuscript. All authors have read
and agreed to the published version of the manuscript.
Conflicts
of Interest
All authors declare no conflict of interest.
Data Availability
Data presented in this study will be available on
a fair request to the corresponding author.
Ethics Approval
Not applicable to this paper.
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