Studies on the Dynamic Changes in Plant Nutrients Organs and Underground Vegetation of Chinese Fir
Plantations
Yun-Ye Deng, Xian-Jun Yang*,
Xiao-Yi Xing, Fei Ni, Li-Xia He and Ying-Hui Li
Department of City Construction,
Shaoyang University, Shaoyang 422004, Hunan Province, China
*For
correspondence: 29785074@qq.com
Contributed equally to the work and are co-first
authors
Received 20 April 2020;
Accepted 15 May 2020; Published 10 December 2020
Abstract
Determination of nutrient contents is important as it provides
theoretical and technical support for tending of the Chinese Fir plantation. In
this study, dynamic changes in plant nutrient content in Chinese fir [Cunninghamia
lanceolata (Lamb.) Hook]
plantations at different ages were studied. Data on continuous
positioning were obtained from a Shangpuzi Woodland Ridge in Suining, Hunan
province, China. The results showed that at the same age, different organs of
Chinese fir possessed different nutrient content in the following order: needle
> twig > bark > root > trunk. The order of each nutrient element
was Ca > N > K > Mg > P in bark and root, N > Mg > Ca > K
> P in trunk, and Ca > K > N > Mg > P in twig. The nutrient
content of plant organs was highest in fast-growing (7 to 12-year old) period,
and began to decline when entering the trunk wood stage, though the downward
trend differed. The nutrient content in the same organs differed amongst plants
of different ages. The variation in nutrient content in the undergrowth
vegetation with forest age was comparable to that in the tree layer, whilst the
content in the organs exceeded that of the corresponding organs of the tree
layer. Upon comparison to the living tree layer, the nutrient content in plant
tissues at different growth stages were determined not only by the genetic and
physiological characteristics of the plant itself, but further influenced by
temperature, precipitation and other habitat conditions.
© 2021 Friends Science Publishers
Keywords: Chinese fir plantations; Continuous positioning;
Growth stages; Nutrient contents
Introduction
Plant growth is
dependent on nutrient content and balance (Alban 1973). Trees exhibit higher
yields when their nutrient composition and distribution are in good balance.
Nutrient contents therefore directly determine the productivity of the forest.
Moreover, nutrient content can reflect the influence of the surrounding
environment on plant growth.
As early as the 1950s, the content of plant nutrient
elements were under study (Hou et al.
1959). Studies on nutrient content and their distribution in plants increased
rapidly in China. For example, significant differences in the nutrient content
of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook] were observed in different regions (Pan et al. 1979; Feng et al. 1985). A study on both nutrient content and their
distribution in Chinese fir during the fast-growing stages has been conducted
(Xiang et al. 2002). Similar studies on nutrient content of Cathaya
argyrophylla (Wang et al. 1983; Shen et al. 1985), Eucalyptus
urophylla (Dong et al. 1986) and Acacia mangium are also
reported (Lin et al. 2002). These studies have important practical and
theoretical significance for the protection and utilization of forests.
In the
past, although the nutrient content of different plant organs has been
measured, an in-depth analysis of the underlying mechanisms has not been known
yet. Nutrient content had been assessed as a measurement parameter, with
studies on the accumulation and distribution of nutrients in the trees,
nutrient absorption, storage and cycling processes assessed. The dynamics of
nutrient content in specific organs at different growth stages had also been
assessed (He et al. 2007) using the
space-for-time method. However, due to the heterogeneity of space the
environmental conditions differ, leading to uncertainty in the data. In this
study, the nutrient content of different organs of
Chinese fir at different ages were studied, based on measurement data from 20
years of continuous positioning from a Shangpuzi Woodland Ridge in Suining,
Hunan province, China. The data provide important information for nutrient
cycling research and nutritional diagnosis for Chinese fir, and provide a basis
for the cultivation and management of plantations.
Materials and Methods
Experimental site
This study assessed the
artificial fir forest in Shangpuzi Woodland Ridge in Suining, Hunan province.
The region is characterized by a mid-subtropical humid monsoon climate, with an
elevation of 190460 m, an annual average temperature of 16.7°C, and an annual
average precipitation of 1320 mm. No temperature extremes occur in either
summer or winter. However, the temperature fluctuates between day and night and
variations in the climate and vegetation amongst vertical positions are
observed. The forest soil was yellow with medium organic matter, and the
thickness of the soil layer was ≥ 80 cm. The content of humus in the
surface soil was 33.6241.53 g/kg, whilst the content of total nitrogen (N),
phosphorus (P) and potassium (K) were 14.0221.65, 0.470.66 and 14.2621.83
g/kg, respectively. The forest stand represented a Chinese fir plantation built
in reclamation area of the broad-leaved secondary forest in 1990. The
afforestation density was 23802560 trees/hm2. In the first 3 years
following afforestation, the plantation only thinned during spring and autumn.
Abundant undergrowth vegetation was observed for Maesa
japonica, Ilex chinensis, Pinus
albicaulis, Litsea cuheha, Urena procumbens, Herba
agrimoniae, Woodwardia japornica and Houttuynia cordata.
Sample collection
Sample plots were
established for biomass determination (667 m2) for seven years after
building the plantation. Biomass was measured in the plots using the methods
proposed by Pan Weijun when the growth stage reached 7, 12, 15, 18, 21 and 25
years (Pan et al. 1978).
To
guarantee a true representation of the tree samples, we excavated intact
standard trees (according to the average tree factor in the plot) with roots,
and sampled equal-weight tree trunks per meter, which were uniformly mixed in
all sub-samples to obtain an ultimate trunk sample. The sampling methods of
twigs, needles, and bark samples were comparable to those of trunk samples. The
roots were divided into four components; fine roots (root diameter < 0.2
cm), coarse roots (0.2 cm ≤ root diameter < 1 cm), large roots (root
diameter ≥ 1 cm) and root tips. Mixed roots were sampled according their
relative weight in the root biomass.
Undergrowth
vegetation and litter in the plots were simultaneously collected. Subplots (2 m
Χ 2 m) were established at each of the four corners (~1 m from the boundary of
the plot) and at the center. All the undergrowth vegetation in the subplots was
collected including leaves, twigs (with small stem also) and root samples.
Whole litter in the subplots was also collected, and divided into three
components, namely leaves, twigs and debris. The fresh weight of these three
components was measured in situ, and mixed according to their relative weight
in the fresh litter. In addition, dead root samples in the soil were obtained
when the standard trees were excavated.
Determination of nutrient content
Total N and P were
measured using the semimicro-Kjeldahl method and molybdenum-blue colorimetry,
respectively. Total K, Ca and Mg were determined by atomic absorption
spectrophotometer. Measurements were performed five times and mean values
calculated. Data were processed on Excel software, and statistical analysis was
performed using SPSS 13.0. One-way and two-way ANOVA were used to evaluate the
variation amongst different treatments. Duncan Multiple Range test was used to
identify significant differences between the treatments.
Results
Nutrient content in the plant organs of Chinese fir
The nutrient content of
different organs showed comparable regularity regardless of the fir age in the
order: needle > twig > bark > root > trunk (p< 0.05; Table 1).
The contents of each nutrient element differed in the same plant organ at the
same growth stage. The content of nutrient elements was Ca>N>K>Mg>P
in bark and roots, N>Mg>Ca>K>P in the trunk,
Ca>K>N>Mg>P in the twigs and N>Ca>K>Mg>P in the
needles. Duncan tests showed that the differences were significant (P<0.05),
excluding the content of Mg and Ca in the trunk that did not differ (P>0.05)
in the fir forest at age of 15, 18, 21 and 25 years. Regardless of the age of
the fir, the content of N in each organ were in the order needle > bark >
twig > root > trunk; P, K, Ca were needle > twig > bark > root
> trunk; whilst those for Mg were in the order needle > twig > root
> bark > trunk.
The
specific nutrient elements and total nutrients in all plant organs increased
from year 7 to year 12-year, but declined at year 15 with differing trends
(Table 1). The nutrient content in the plant trunk and bark continued to decline
until year 25, whilst that of needles, twigs, and roots declined only to year
21, but augmented at year 25.
Nutrient contents in undergrowth vegetation
Table 1:
Nutrient content of Chinese fir plantations at different growth stages (g/kg)
Growth stage |
Nutrient element |
Trunk |
Bark |
Twig |
Needle |
Root |
7-year old |
N |
0.92±0.066aA |
3.58±0.1968bA |
3.54±0.20cA |
11.86±0.94dA |
2.84±0.18eA |
P |
0.12±0.016aM |
0.37±0.028bM |
0.40±0.03cM |
1.09±0.07dM |
0.33±0.03eM |
|
K |
0.34±0.036aW |
3.61±0.218bW |
3.92±0.17cW |
9.18±0.51dW |
2.73±0.16eW |
|
Ca |
0.63±0. 046aP |
5.80±0.338bP |
6.08±0.31cP |
10.87±0.62dP |
3.62±0.20eP |
|
Mg |
0.68±0.416aN |
0.72±0.388bN |
1.75±0.09cN |
2.78±0.14dN |
1.05±0.07eN |
|
Sum |
2.96a |
14.18b |
15.72c |
33.07d |
10.57e |
|
12-year old |
N |
1.19±0.076aA |
4.12±0.238bA |
3.97±0.21cA |
15.92±0.19dA |
3.19±0.17eA |
P |
0.18±0. 016aM |
0.44±0.038bM |
0.62±0.04cM |
1.22±0.07dM |
0.43±0.02eM |
|
K |
0.37±0.036aW |
3.67±0.208bW |
4.16±0.23cW |
9.63±0.51dW |
2.94±0.16eW |
|
Ca |
0.66±0.046aP |
6.80±0.398bP |
6.84±0.39cP |
11.79±0.61dP |
3.76±0.21eP |
|
Mg |
0.78±0.046aN |
0.98±0.068bN |
2.21±0.13cN |
2.89±0.15dN |
1.28±0.07eN |
|
Sum |
3.16 a |
15.91 b |
17.90 c |
41.40 d |
11.50 e |
|
15-year old |
N |
1.10±0.586aA |
4.01±0.238bA |
3.75±0.20cA |
15.40±0.18dA |
3.10±0.17eA |
P |
0.15±0.016aM |
0.41±0028bM |
0.59±0.03cM |
1.18±0.07dM |
0.41±0.03eM |
|
K |
0.32±0.026aW |
3.53±0.218bW |
3.89±0.20cW |
9.27±0.51dW |
2.84±0.17eW |
|
Ca |
0.64±0.046aP |
6.92±0.368bP |
6.80±0.38cP |
11.81±0.59dP |
3.79±0.20eP |
|
Mg |
0.70±0.046aN |
0.92±0.058bN |
2.09±0.12cN |
2.86±0.19dN |
1.20±0.64eN |
|
Sum |
2.91 a |
15.79 b |
17.12 c |
40.52 d |
11.34 e |
|
18-year old |
N |
1.05±0.546aA |
3.98±0.388bA |
3.44±0.17cA |
14.89±0.17dA |
2.95±0.17eA |
P |
0.13±0.016aM |
0.40±0.028bM |
0.57±0.03cM |
1.17±0.07dM |
0.40±0.02eM |
|
K |
0.34±0.026aW |
3.54±0.208bW |
3.92±0.36cW |
9.29±0.47dW |
2.85±0.16eW |
|
Ca |
0.65±0.046aP |
6.93±0.358bP |
6.81±0.38cP |
11.88±0.54dP |
3.81±0.21eP |
|
Mg |
0.71±0.046aN |
0.91±0.058bN |
1.98±0.10cN |
2.85±0.17dN |
1.22±0.14eN |
|
Sum |
2.84 a |
15.76 b |
16.72 c |
40.08 d |
11.23 e |
|
21-year old |
N |
0.98±0.066aA |
3.88±0.218bA |
3.26±0.20cA |
13.94±0.74dA |
2.89±0.16eA |
P |
0.12±0.016aM |
0.41±0.028bM |
0.58±0.03cM |
1.18±0.07dM |
0.41±0.03eM |
|
K |
0.35±0.026aW |
3.55±0.198bW |
3.93±0.20cW |
9.31±0.50dW |
2.86±0.16eW |
|
Ca |
0.68±0. 046aP |
6.97±0.388bP |
6.83±0.38cP |
11.90±0.59dP |
3.85±0.20eP |
|
Mg |
0.69±0.046aN |
0.92±0.068bN |
1.97±0.10cN |
2.87±0.16dN |
1.19±0.07eN |
|
Sum |
2.82 a |
15.73 b |
16.57 c |
39.20 d |
11.20 e |
|
25-year old |
N |
0.90±0.056aA |
3.81±0.218bA |
3.28±0.22cA |
14.11±0.79dA |
2.85±0.17eA |
P |
0.12±0.016aM |
0.41±0.238bM |
0.57±0.04cM |
1.17±0.06dM |
0.41±0.02eM |
|
K |
0.37±0.026aW |
3.57±0.208bW |
3.95±0.19cW |
9.34±0.45dW |
2.89±0.15eW |
|
Ca |
0.70±0.036aP |
6.99±0.348bP |
6.86±0.38cP |
11.93±0.58dP |
3.89±0.09eP |
|
Mg |
0.70±0.036aN |
0.91±0.068bN |
1.98±0.09cN |
2.86±0.16dN |
1.20±0.07eN |
|
Sum |
2.79 a |
15.69 b |
16.66 c |
39.41 d |
11.24 e |
Different lowercase
letters within rows indicate significant difference amongst the five organs of
in terms of each nutrient element (p<0.05). Different capital letters
within columns indicate significant differences amongst the five elements in
the same organ (p<0.05)
Nutrient content in the undergrowth vegetation was more abundant than that of the tree layer (Table 2). The nutrient
content in the leaves was highest, followed by twigs, whilst the lowest value
was observed in the roots. Meanwhile, the nutrient content in each undergrowth
vegetation organ differed, being N>K>Ca>Mg>P in leaf, K>N>Ca>Mg>P in twigs (including small
stems), compared to N>Ca>K>Mg>P in the roots. Significant
differences in the content of each element were also observed across the
different undergrowth vegetation organs at the same growth stages (p<0.05).
There
were significant differences in the N, Ca and Mg content of the same tissues
across the growth stages (Table 2). Nevertheless, the P content showed no
significant differences across the growth stages, except for 7-year olds, which
were significantly lower (p<0.05). There were significant differences in K
content across the various growth stages except for K content in the leaves
between 15 and 18 year olds, and between 21 and 25 year olds, the twigs between
18, 21, and 25 year olds, and K content in the roots between 12, 21 and 25 year
olds.
Nutrient content in the litter and dead roots
The nutrient content was higher in the litter
than that in the dead roots at the same growth stages, and the content of each
element significantly (P<0.05) differed between the litter and dead roots (Table 3). The relationship between nutrient content whether in the litter or dead roots and growth
stages showed the same tendency as the tree layer.
The N,
K, and Ca content of the litter and dead roots significantly differed across
the various growth stages (P<0. 05) (Table 3). The P content of the litter
also significantly differed across the growth stages, but not in the dead
roots. The variation of Mg content with each growth stage was more complex.
There were no significant differences in the Mg content of the litter amongst
the growth stages except for at 12-years. In contrast, the dead roots differed
across all growth stages except for between 12 and 15 years, and 21 and 25
years.
Discussion
Table 2: Nutrient content in the
undergrowth vegetation of Chinese Fir Plantations at different growth stages
(g/kg)
Growth stage |
Leaf |
Twig (including
small stem) |
Root |
||||||||||||
N |
P |
K |
Ca |
Mg |
N |
P |
K |
Ca |
Mg |
N |
P |
K |
Ca |
Mg |
|
7-year old |
13.27aA |
1.53bA |
11.27cA |
8.14dA |
2.24eA |
4.21fA |
0.52mA |
5.21nA |
4.12hA |
1.18kA |
3.68tA |
0.50yA |
2.70wA |
3.31sA |
0.82rA |
12-year old |
15.87aB |
159bB |
11.96cB |
8.25dB |
2.67eB |
4.55fB |
0.64mB |
5.99nB |
4.24hB |
1.59kB |
3.91tB |
0.60yB |
2.54wD |
3.47sB |
1.09rB |
15-year old |
15.72aC |
1.58bB |
11.03cC |
8.37dC |
2.59eC |
4.42fC |
0.62mB |
6.04nC |
4.59hC |
1.52kC |
3.82tC |
0.58yB |
2.83wC |
3.64sC |
1.02rC |
18-year old |
15.44aD |
1.57bB |
10.99cC |
8.43cD |
2.54eD |
4.35fD |
0.60mB |
5.87nD |
4.62hD |
1.47kD |
3.73tD |
0.57yB |
2.66wE |
3.72sD |
0.91rD |
21-year old |
15.36aE |
1.58bB |
10.84cD |
8.48dE |
2.48eE |
4.29fE |
0.60mB |
5.85nD |
4.69hE |
1.41kE |
3.64tE |
0.55yB |
2.57wD |
3.82sE |
0.84rE |
25-year old |
15.22aF |
1.56bB |
10.81cD |
5.53dF |
2.43eF |
4.22fF |
0.59mB |
5.82nD |
4.74hF |
1.34kF |
3.50tF |
0.55yB |
2.53wD |
3.92sF |
0.75rF |
Different lowercase
letters within rows indicate significant differences (p<0.05).
Different capital letters within columns indicate significant differences (p<0.05)
Table 3: Nutrient content of the litter
and dead roots of Chinese Fir Plantation at different growth stages (g/kg)
Growth stage |
Litter |
Dead root |
||||||||
N |
P |
K |
Ca |
Mg |
N |
P |
K |
Ca |
Mg |
|
7 years old |
5.80±0.23aA |
0.86±0.05bA |
0.55±0.03cA |
9.98±0.58dA |
1.28±0.77eA |
2.42±0.16fA |
0.32±0.02mA |
0.40±0.03nA |
3.32±0.17hA |
0.77±0.05kA |
12 years old |
6.29±0.38aB |
0.93±0.05bB |
0.64±0.04cB |
10.37±0.59dB |
1.35±0.73eB |
2.58±0.17fB |
0.34±0.02mA |
0.57±0.03nB |
3.44±0.18hB |
1.01±0.06kB |
15 years old |
6.12±0.32aC |
0.87±0.05bC |
0.58±0.03cC |
10.59±0.61dC |
1.27±0.68eA |
2.53±0.15fC |
0.32±0.02mA |
0.50±0.02nC |
3.52±0.17hC |
0.99±0.05kB |
18 years old |
5.94±0.29aD |
0.76±0.04bD |
0.49±0.03cD |
11.07±0.57dD |
1.28±0.65eA |
2..47±0.16fD |
0.33±0.02mA |
0.43±0.03nD |
3.61±0.18hD |
0.96±0.05kC |
21 years old |
5.82±0.29aE |
0.71±0.05bE |
0.43±0.02cE |
11.65±0.63dE |
1.29±0.59eA |
2.42±0.14fE |
0.34±0.02mA |
0.38±0.02nE |
3.75±0.20hE |
0.91±0.06kD |
25 years old |
5.75±0.30aF |
0.69±0.04bF |
0.36±0.03cF |
11.87±0.66dF |
1.30±0.67eA |
2.36±0.13fF |
0.33±0.02mA |
0.32±0.02nF |
3.84±0.21hF |
0.93±0.05kD |
Different lowercase
letters within rows indicate significant differences (p<0.05).
Different capital letters within columns indicate significant differences (p<0.05)
The nutrient content of
the fir organs varied with growth stage in the Suining forest, Hunan Province,
resulting in significant differences in nutrient content in same fir organs at
different growth stages. Regarding nutrient content in the different organs at
the same growth stages, the trends were determined by the genetic and
physiological characteristics of the Chinese fir, which was similar for Taoyuan
(Feng et al. 1985) in the Hunan
Province. The order and value of the various nutrients in the same organs at
the same growth stages showed some differences. Taking the nutrient content in
the needles at the 12-year old fir forest stage as an example, the content of N, Ca, K, Mg and P were 15.92, 11.97, 9.63,
2.94 and 1.22 g/kg in Suining, and 15.22,
11.60, 9.80, 2.80, 0.90 g/kg in Huitong, respectively, showing the same trend
as N>Ca>K>Mg>P. However, the order of the above elements
represented N>K>Ca>Mg>P, for
which the contents were 10.22, 79.13,
5.10, 2.42 and 0.62 g/kg, respectively. Although the three sample areas were
all located in the mid-subtropical zone, the microclimate conditions of Zhuting
and the other two areas (which were adjacent) still differed. The soil
thickness and N, P and K content were lower in Zhuting than that of Suining and
Huitong (Feng et al. 1985).
Differences in the micro-environmental conditions and soil fertility levels
could lead to these differences in the plant body (Chen et al. 1999).
Firstly,
the nutrient content of the different forest trees differed. For example, the
order of nutrient content in the same organs at each growth stage of Chinese
fir were needles> twigs > bark > roots > trunk, compared to needle
> bark > twigs > roots > trunk of A. mangium (He et al. 2007) and P. tabulaeformis (Shen et al. 1985). The nutrient content in
the plant organs of Chinese fir were related to organ function. Needles were
the main photosynthesis organ that provided the biomass. Fir had a shorter
growth period and required higher levels of nutrients for its growth and
metabolism, and as such, a greater nutrient content were required compared to
other organs. Physiological and biochemical activities were weakest in the
plant trunk, and as such, nutrients were easily consumed or transferred,
resulting in a lower nutrient content. Plant twigs and barks were the transport
organs, and specific nutrients were required to satisfy their functions,
leading to a higher nutrient content. In addition, plant twigs and bark had supporting
functions, so that Ca content was higher than other nutrient elements. The
roots were responsible
for the absorption of nutrients and water, and supported the plant body. As
such, the Ca content was higher than
other nutrients. In addition, the roots were located closer to soil water and
were protected and fed by adjacent soils, requiring lower levels of nutrients,
resulting in a lower nutrient content. An array of factors led to changes in
nutrient content in the plant tissues during the growth stage. Firstly, the
levels of nutrients in plant tissues of different growth stages were determined
by the genetic and physiological characteristics of the plants. The nutrient
requirements for the production of 1 ton dry biomass declined at increasing
growth stages when the Chinese fir entered the trunk wood stage (Tian and Xiang
2002), meaning the nutrient content in the plant tissue decreased with the
development of the growth stages. Secondly, ambient climate factors also
influenced the nutrient content of plant tissue. There were obvious variations
in the precipitation and temperature across the years, which induced changes in
the nutrient content of the plant tissue (Nie 1991). Finally, the organic
components of plant tissue may have altered across the growth stages, for
example, increases were observed in the degree of signification of the plant
tissue. This may represent an important reason for the increase in Ca content
in Chinese fir organs at increasing growth stages.
Secondly,
the order of the various nutrient elements in the same organ at near growth
stages showed differences. For example, the order of various elements in the
needles, twigs, bark and roots for 14-year-old P. massonana were K>N>Ca>Mg>P, and
Ca>K>N>Mg>P in the trunk (Tian et al. 2002), compared to
Ca>N>K>Mg>P in the bark and roots, N>Mg>Ca>K>P in the
trunk, Ca>K>N>Mg>P in the twigs, and N>Ca>K>Mg>P in the
needles of 14-year-old Chinese fir. The nutrient content in the undergrowth
tissue was similar to that of the tree layer, which significantly increased
from 7 to 12-years, and then gradually decreased with increasing growth stages
at the trunk wood stage, except for Ca, which increased across the entire
experiment period. That may be because the trees were small prior to age 7,
with small canopy densities and adequate light under the forest. Heliophilous
plants therefore dominated the undergrowth vegetation. Chinese fir from 7 to
12-years with lush cover limited the light in the understory, resulting in
sciophilous plants being dominant. When the fir entered the trunk wood stage,
the trees were self-pruning, and then improved the light conditions, so that
the undergrowth vegetation was gradually replaced by heliophilous plants.
Studies have shown that heliophilous shrubs possess a higher caloric value and
carbon content than sciophilous shrubs (Wang and Sun 2008). More
information is required to assess whether sciophilous shrubs have a higher
nutrient content than heliophilous shrubs.
Thirdly,
there were extreme differences in nutrient content across the different tree
species in the same organs according to growth stage. For example, the nutrient
content in the trunk, bark, twigs, needles and roots of 7-year old A. mangium were 4.29, 22.22, 13.39,
40.96 and 7.12 g/kg (He et al. 2007), while those in the corresponding
organs were 2.96, 14.18, 15.72, 33.07 and 10.57 g/kg in 7-year old Chinese fir.
As a further example, the nutrient content in these organs were 23.50, 61.42,
57.93, 256.24 and 41.04 g/kg in 25-year old P.
tabulaeformis (Shen et al. 1985), compared to 2.79, 15.96, 16.66,
39.41 and 11.24 g/kg, respectively, in 25-year old Chinese fir. Regarding
differences in the genetic and physiological characteristics of the different
tree species, there were differences in site conditions. The different site
conditions made a contribution to the differences in the nutrient content of
the plant body.
Finally,
consistent with previous studies, the undergrowth vegetation contained a higher
nutrient content than that of the tree layer. This was mediated by the spatial
distribution patterns of the plants (living) as the nutrient content of the
forest ecosystem generally increased from the upper layer to the lower layer,
namely, the tree layer showed the lowest nutrient content, followed by the bush
layer, whilst the grass layer showed the highest nutrient content (Zhang et
al. 2006).
As for
the litter content, the nutrient content was lower than that of living plants,
which was determined by the nutrient biological cycle in the plant body. That
was probably due to the fir and undergrowth vegetation being the source of the
litter and dead roots, and as such, the nutrient content in the former
determined the nutrient content in the latter. Furthermore, the nutrient
content of needles, twigs and bark were higher than that in the roots of
Chinese fir based on previous analysis, which led to the nutrient content in
the litter exceeding that of dead roots. This study showed that the nutrient
content of the litter was lower than that of corresponding living plants
(whether in the tree layers or undergrowth vegetation). This was because some
of the nutrients in the aging tissue had transferred to other living sites
prior to falling.
Conclusion
Nutrient content in the
same organs and site conditions differed amongst the different growth stages of
Chinese fir, suggesting that some deviation exists when only a single growth
stage is used to demonstrate the relationship between the biomass, nutrient
content and nutrient utilization, and the accumulation and circulation of the
entire growth process. We highlight the consistency of the spatial scale and
the continuity of the time scale, which could overcome the heterogeneity of
various site conditions. The defects in "space for time" methods
could therefore be circumvented producing data of more physiological relevance.
These findings provide improved guidance for production practices.
Acknowledgments
The study was funded by
the Shaoyang Science and Technology Project (2018NS25).
Author Contributions
Yun-ye Deng and Xian-jun
Yang carried out the concepts, design, definition of intellectual content,
literature search, data acquisition, data analysis and manuscript preparation.
Xiao-yi Xing and Ying-hui Li provided assistance for data acquisition, data analysis
and statistical analysis. Li-xia He and Fei Ni performed manuscript review. All
authors have read and approved the content of the manuscript.
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