Twenty-seven surface soil samples were collected from four landscape sites in Shanghai, and seven soil profile samples were gathered from the two older sites for evaluation of horizontal and vertical distribution of soil properties to reveal their relationship with plant roots. Results indicated that urban soil had significant heterogeneities. Soil total nitrogen was significantly correlated with organic matter and total potassium was more abundant than total phosphorus. The available contents of iron, manganese, zinc and copper were higher than the standards for plant growth established by Soltanpour. pH and electrical conductivity increased with increasing soil vertical depth, possibly due to leaching, while the nutrients limiting plant growth such as nitrogen, phosphorus, potassium, iron, copper and zinc had more shallow distributions due to absorption by plant roots. However, with the increasing of soil depth, contents of magnesium, sodium, sulfur and chloride increased due to leaching and bio-cycling, which was further shown by the correlation analysis.
Urban soils are the basis of landscape planting and have a great effect on plant growth. Without desirable concentrations of appropriate nutrients, plant growth is adversely affected. Moreover, since urban landscape soils are generally recognized as being highly disturbed and heterogeneous, many soils have systematic patterns and obviously differ, even in the same area. Therefore, many studies have been conducted on the physical and chemical properties of urban green space soils in major cities of China [
There have been numerous studies on horizontal or vertical distribution of soil nutrients; however, traditional sampling methods with fixed interval depths of 20 or 10 cm have generally been applied to test vertical distribution of soil physical and chemical properties, which did not conform to the distribution of plant roots and ignored soil between the sampling positions. Consequently any correlation between plant roots and soil nutrients could not be accurately determined [
Soil-amending and soil fertility practices such as plant cover systems and organic and inorganic inputs strongly influence all soil components [
Shanghai is located at 121˚29' and E 31˚41'N, in the east of China, and has a total area of about 6341 km2. Shanghai is one of the most important cultural, commercial, financial, industrial and communication centers in China. The investigation areas included Zhongshan Park, Expo Park, Century Park and Chenshan Botanical Garden. Zhongshan Park was built in 1914 in Changning District with a total area of over 21.42 ha, half of which is for landscape planting. EXPO Park is green land in the city center and was built in 2010. Century Park is the biggest urban park in the inner ring road of Shanghai, situated in Pudong new district and built in 1997. Chenshan Botanical Garden, built in 2007 in Songjiang district, has a total area of 207 ha and highly diverse plant species.
Soil samples were collected from the four parks on 19-21 April 2011. Sampling depth was according to the distribution of plant roots of the sampling location. Three to four depths were sampled for arbor trees, large and medium shrubs based on the distribution of number of plant roots. Each soil sample consisted of five sub-sam- ples which were collected from the surrounding area of each site. A total of 27 surface soil samples were collected: nine samples from Zhongshan Park, five from EXPO Park, nine from Century Park and four from Chenshan Botanical Garden. In addition, a soil profile was excavated in Zhongshan Park and Century Park. Soil samples were gathered from the profile according to the distribution of plant roots, and total of seven soil samples were collected. Details of the sampling record are presented in
The samples were taken to the laboratory, dried at ambient room temperature and ground to pass a 2-mm sieve before analysis. Half of each sieved soil sample was further ground to pass through a 1-mm mesh screen for the determination of soil moisture coefficient, and others were passed through a 0.149-mm mesh and stored
Zones | Number of surface soil samples | Profile soil samples (distribution of plant roots) | Plants |
---|---|---|---|
Zhongshan Park | 9 | 0 - 18 cm (developed root system) 18 - 28 cm (lots of roots) 28 - 52 cm (a few roots) 52 - 94 cm (dead roots) | Pittosporum, Cedar, Cinnamomun camphora, Ligustrum lucidum, Cherry tree, Elaeagnus pungens thumb |
Expo Park | 5 | - | Loquat, Cedar, Hu shaddock, Lawn |
Century Park | 9 | 0 - 27 cm (developed root system ) 27 - 39 cm (lots of roots) 39 - 78 cm (a few roots and dead roots) | Camellia sasanqua, Buxus sinica, Acer palmatum, Slash pine, Mei flower tree |
Chenshan Botanical Garden | 4 | - | Crabapple tree, Photinia, Rosa chinensis, Hemerocallis |
Note: “-” represent that soil profile that was harvested.
in clean polyethylene bags for the determination of soil OM and TN. The 2-mm soil samples were used for the saturated extraction and the determination of elements extracted by AB-DTPA (ammonium bicarbonate-diethy- lenetriamine pentaacetic acid) method [
Soil water content was determined gravimetrically after heating in an oven at 105˚C for 8 h; all results are presented on an oven dry basis. Soil OM was determined using the potassium dichromate oxidation procedure [
The quality of chemical analysis was validated by repeated measurements of blanks and reference samples. Chemical analyses were repeated until a precision of ±5% and an accuracy of 95% - 105% was achieved; while prepared blanks were always below instrumental detection limits.
Soil properties of the four urban parks are presented in
EC of soils reflects the concentrations of dissolved salts in soil moisture. The EC value of soil samples collected were within the range of 0.3 - 3.3 with an average of 1.0 ± 1.3 mS/cm for Zhongshan Park, 0.9 - 1.6 with average of 1.2 ± 0.3 mS/cm for Expo Park, 0.4 - 1.9 with average of 0.9 ± 0.6 mS/cm for Century Park and 1.1 - 2.8 with average of 1.9 ± 0.8 mS/cm for Chenshan Botanical Garden (
Parameter | Zhongshan Park (n = 9) | Expo Park (n = 5) | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mean | Min | Max | SD | CV (%) | Mean | Min | Max | SD | CV (%) | |||||
pH | 7.4 | 7.0 | 7.8 | 0.4 | 5.7 | 7.7 | 7.3 | 8.0 | 0.3 | 3.9 | ||||
EC (mS/cm) | 1.0 | 0.3 | 3.3 | 1.3 | 120.6 | 1.2 | 0.9 | 1.6 | 0.3 | 25.7 | ||||
Cl (mg/L) | 126.4 | 7.0 | 536.0 | 229.3 | 181.4 | 132.0 | 98.0 | 172.0 | 33.8 | 25.6 | ||||
Organic matter (g/kg) | 31.7 | 16.0 | 45.1 | 13.5 | 42.5 | 18.8 | 8.4 | 29.0 | 9.4 | 49.9 | ||||
Total nitrogen (g/kg) | 1.5 | 0.9 | 2.1 | 0.6 | 38.0 | 0.9 | 0.4 | 1.3 | 0.4 | 50.8 | ||||
Available P (mg/kg) | 5.8 | 1.7 | 11.4 | 3.8 | 65.1 | 24.0 | 13.4 | 51.2 | 18.2 | 75.9 | ||||
Available K (mg/kg) | 177.3 | 110.6 | 323.5 | 85.4 | 48.1 | 211.4 | 68.0 | 378.9 | 130.5 | 61.7 | ||||
Available Fe (mg/kg) | 47.7 | 28.6 | 81.3 | 21.2 | 44.4 | 62.8 | 43.5 | 79.0 | 16.7 | 26.6 | ||||
Available Mn (mg/kg) | 2.2 | 1.8 | 2.5 | 0.3 | 13.2 | 3.3 | 2.9 | 3.7 | 0.4 | 11.4 | ||||
Available Zn (mg/kg) | 21.5 | 7.9 | 32.6 | 12.2 | 56.5 | 7.3 | 4.1 | 9.8 | 2.5 | 34.0 | ||||
Available Cu (mg/kg) | 11.4 | 4.6 | 18.4 | 6.5 | 57.1 | 3.5 | 0.8 | 6.0 | 2.1 | 61.3 | ||||
Available Mg (mg/kg) | 194.3 | 101.6 | 271.5 | 77.5 | 39.9 | 156.8 | 51.4 | 248.7 | 101.4 | 64.7 | ||||
Available Na (mg/kg) | 26.1 | 10.8 | 64.0 | 21.6 | 82.9 | 97.0 | 75.9 | 141.5 | 30.9 | 31.8 | ||||
Available S (mg/kg) | 35.3 | 7.2 | 105.0 | 39.8 | 112.7 | 62.0 | 34.8 | 101.7 | 29.9 | 48.2 | ||||
Parameter | Century Park (n = 9) | Chenshan Botanical Garden (n = 4) | ||||||||||||
Mean | Min | Max | SD | CV (%) | Mean | Min | Max | SD | CV (%) | |||||
pH | 7.5 | 7.2 | 7.7 | 0.2 | 2.0 | 7.6 | 7.2 | 7.9 | 0.3 | 3.4 | ||||
EC (mS/cm) | 0.9 | 0.4 | 1.9 | 0.6 | 63.2 | 1.9 | 1.1 | 2.8 | 0.8 | 42.5 | ||||
Cl (mg/L) | 135.0 | 21.0 | 571.0 | 198.5 | 147.1 | 119.4 | 67.0 | 190.0 | 51.9 | 43.5 | ||||
Organic matter (g/kg) | 33.0 | 13.9 | 71.2 | 21.4 | 65.0 | 42.7 | 18.5 | 102.6 | 34.2 | 80.0 | ||||
Total nitrogen (g/kg) | 1.8 | 0.9 | 3.0 | 0.8 | 44.8 | 2.3 | 1.1 | 5.5 | 1.8 | 79.7 | ||||
Available P (mg/kg) | 56.0 | 2.7 | 186.3 | 68.8 | 122.8 | 64.6 | 33.4 | 151.4 | 49.0 | 75.9 | ||||
Available K (mg/kg) | 347.2 | 170.8 | 788.9 | 224.9 | 64.8 | 426.2 | 330.6 | 543.3 | 88.4 | 20.7 | ||||
Available Fe (mg/kg) | 39.5 | 27.3 | 66.0 | 13.4 | 34.0 | 152.4 | 82.8 | 299.5 | 90.3 | 59.2 | ||||
Available Mn (mg/kg) | 4.6 | 1.4 | 14.5 | 4.6 | 99.5 | 5.2 | 1.9 | 10.5 | 4.0 | 77.0 | ||||
Available Zn (mg/kg) | 12.3 | 3.1 | 34.5 | 11.3 | 91.9 | 6.7 | 2.6 | 11.9 | 3.4 | 50.0 | ||||
Available Cu (mg/kg) | 5.2 | 3.0 | 10.2 | 2.5 | 47.8 | 9.1 | 4.2 | 16.1 | 4.6 | 50.1 | ||||
Available Mg (mg/kg) | 189.6 | 103.4 | 271.5 | 54.9 | 29.0 | 320.4 | 205.1 | 407.0 | 74.2 | 23.2 | ||||
Available Na (mg/kg) | 59.5 | 13.5 | 233.1 | 79.1 | 132.9 | 109.4 | 42.1 | 184.1 | 55.5 | 50.8 | ||||
Available S (mg/kg) | 60.6 | 12.7 | 159.0 | 52.4 | 86.4 | 212.2 | 70.7 | 528.0 | 190.5 | 89.8 | ||||
Park were in the range that adversely affects growth of moderately saline-sensitive plants (2 - 4 mS/cm). Of samples from Chenshan Botanical Garden, 40.5% had salinity that exceeded the standard for growth of saline-sensitive plants but met the standard for moderately sensitive plants. Moreover, the CV of EC varied greatly among the parks, indicating heterogeneities of soil [
As the vital aggregating agent, soil OM can influence soil structural formation and maintenance. The amount of soil OM differed among the four parks (
For TN, 28.6% of soil samples were extremely high, 19.0% were high, 33.3% were moderate to high, 9.5% were low to moderate, 4.8% were low and 4.8% were extremely low. The TN contents of soils were significantly correlated with OM, consistent with results of Jim [
As the two major macro-nutrients for plants, levels of P and K should be studied. The contents of available P and available K in soils were near to those of earlier reports that showed K was more abundant in soil than P [
The contents of available Na and S also had a large range in CV. Available Na ranged from 10.8 (Zhongshan Park) to 233.1 mg/kg (Century Park), and available S from 7.2 (Zhongshan Park) to 528.0 mg/kg (Chenshan Botanical Garden). The contents of available Na and S in surface soil decreased with the increasing age of parks, which may be ascribed to leaching and application of fertilizer, and this hypothesis will be further tested in following studies.
Generally speaking, the mechanisms affecting the vertical distribution of soil nutrients can be classified into at least four major processes: weathering, atmospheric deposition, leaching and biological cycling [
CI is an easily mobile element in soil and is not likely to constrain plant growth with adequate leaching [
Contents of P and K tended to decrease with increased soil depth, which differed to CI, and might be ascribed to the plant cycling and management practices. P and K are not readily mobile in soil and generally remain in the soil profile to which they have been applied. On one hand, it may be generally recognized that P and K are the main nutrients limiting plant growth, and have shallower distributions than nutrients that are less limiting [
Fe, Mn, Cu and Zn are essential micro-nutrients for plant growth and important for gene expression and biosynthesis of proteins [
Fe, Mn, Cu and Zn are the most bio-available at lower pH, and their cationic forms may be changed to insoluble forms such as hydroxides and oxides in less acidic soil [
The levels of Mg, Na and S tended to be low in the soil surface, which was in contrast with all other elements. Previous studies indicated that nutrients that are rarely required by plants (such as Na) have shallower distributions in soils [
The relationships between nutrient elements and soil properties were studied, and the results are presented in
EC values were positively and significantly correlated with the content of chlorine and available Mg and S; moreover, the chlorine concentration was positively correlated with available K, Mn, Zn and Na (
Urban ecological environments can have a large impact on sustainable economic development, and can be influenced to a large extent by the amount of green space available to the public. Growth of vegetation also has a useful ecological function and is strongly affected by soil quality. Therefore, it is essential that the content of various nutrient elements in soils of green spaces are investigated. The horizontal and vertical distributions of
Parameters | pH | EC | Chlorine | OM | TN | P | K | Fe | Mn | Zn | Cu | Mg | Na | S |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
pH | 1 | −0.398 | −0.324 | −0.534* | −0.503* | −0.060 | −0.095 | 0.133 | −0.058 | −0.652** | −0.513* | −0.241 | 0.259 | 0.028 |
EC | 1 | 0.462* | 0.382 | 0.391 | −0.074 | 0.150 | 0.327 | 0.082 | −0.070 | 0.161 | 0.488* | 0.196 | 0.507* | |
Cl | 1 | 0.429 | 0.280 | 0.427 | 0.449* | −0.028 | 0.520* | 0.476* | 0.056 | 0.210 | 0.610** | 0.319 | ||
OM | 1 | 0.972** | 0.438* | 0.708** | 0.023 | 0.555** | 0.510* | 0.306 | 0.627** | 0.183 | 0.109 | |||
TN | 1 | 0.351 | 0.676** | 0.011 | 0.490* | 0.372 | 0.261 | 0.630** | 0.076 | 0.105 | ||||
P | 1 | 0.782** | 0.097 | 0.569** | 0.285 | 0.000 | 0.311 | 0.561** | 0.176 | |||||
K | 1 | 0.207 | 0.668** | 0.280 | 0.152 | 0.547* | 0.626** | 0.368 | ||||||
Fe | 1 | 0.335 | −0.184 | 0.400 | 0.347 | 0.338 | 0.693** | |||||||
Mn | 1 | 0.282 | 0.008 | 0.138 | 0.517* | 0.257 | ||||||||
Zn | 1 | 0.625** | 0.143 | 0.059 | −0.101 | |||||||||
Cu | 1 | 0.411 | −0.040 | 0.393 | ||||||||||
Mg | 1 | 0.311 | 0.362 | |||||||||||
Na | 1 | 0.558** | ||||||||||||
S | 1 |
soil nutrients in Zhongshan Park, EXPO Park, Century Park and Chenshan Botanical Garden in Shanghai confirmed that urban soils had a heterogeneous spatial distribution. The CVs of various soil qualities except for pH varied greatly between and even within parks. For example, the mean pH of soils from Zhongshan Park, Expo Park, Century Park and Chenshan Botanical Garden was 7.4, 7.7, 7.5 and 7.6, respectively, and the CVs of soil pH from different parks was <5.7%, indicating a slightly alkaline nature of these urban park soils. pH and EC values increased with increasing soil depth likely due to leaching, and nutrients limiting for plants (such as N, P, K, Fe, Cu and Zn) had more shallow distributions due to absorption by plant roots. However, Mg, Na, S and chlorine decreased possibly due to the contribution of leaching and bio-cycling.
We thank the special program of Shanghai Landscaping Administration Bureau (Project G102402) for financial support.
The authors declare none.
JingLiang,HailanFang,GuanjunHao, (2016) Effect of Plant Roots on Soil Nutrient Distributions in Shanghai Urban Landscapes. American Journal of Plant Sciences,07,296-305. doi: 10.4236/ajps.2016.72029
USDA class | Electrical conductivity range (mS/cm) | Crop salt tolerance | Example Crop |
---|---|---|---|
A | 0 - 2 | Sensitive | Bean, strawberry, carrot, onion, citrus |
B | 2 - 4 | Moderately sensitive | Corn, cucumber, tomato |
C | 4 - 8 | Moderately tolerant | Wheat |
D | 8 - 16 | Tolerant | Barley |
Class | Extremely high | High | Moderate to high | Low to moderate | Low | Extremely low |
---|---|---|---|---|---|---|
Organic matter | >40 | 30 - 40 | 20 - 30 | 10 - 20 | 6 - 10 | <6 |
Total nitrogen | >2 | 1.5 - 2 | 1 - 1.5 | 0.75 - 1 | 0.5 - 0.75 | <0.5 |
Micro-nutrients | Content (mg/kg) | ||
---|---|---|---|
Low | Medium | High | |
Iron | <3.0 | 3.0 - 5.0 | >5.0 |
Copper | <0.3 | 0.3 - 0.5 | >0.5 |
Zinc | <0.9 | 0.9 - 1.5 | >1.5 |
Manganese | <0.6 | 0.6 - 1.0 | >1.0 |