Excerpt
Content
1 The Naban River Watershed National Nature Reserve
1.1 General introduction
1.2 Geology
1.3 Soils and nutrients
2 Material and methods
2.1 Field investigations
2.1.1 Site selection
2.1.2 Soil profile description
2.1.3 Soil sampling
2.2 Laboratory analysis
2.2.1 Bulk density, fine earth density, water content
2.2.2 Texture
2.2.3 pH value
2.2.4 Soil organic carbon (SOC) and total nitrogen (TN)
2.2.5 Nutrients
2.2.6 Cation exchange capacity
3 Results
3.1 World Reference Base
3.2 Soil profile description
3.2.1 Profile
3.2.2 Profile
3.2.3 Profile
3.2.4 Profile
3.2.5 Profile
3.2.6 Profile
3.2.7 Profile
3.2.8 Profile
3.2.9 Profile
3.3 Transect
3.3.1 Depth and fine earth density
3.3.2 Texture
3.3.3 pH value
3.3.4 SOC and TN
3.3.5 Nutrients
3.3.6 Effective CEC and base saturation
3.4 Transect
3.4.1 Depth and fine earth density
3.4.2 Texture
3.4.3 pH value
3.4.4 SOC and TN
3.4.5 Nutrients
3.4.6 Effective CEC and base saturation
4 Literature
5 Annex
List of figures
Figure 1: Location of Xishuangbanna and the counties Menghai, Jinghong, Mengla
Figure 2: Profile P1
Figure 3: Profile P2
Figure 4: Profile P3
Figure 5: Profile P4
Figure 6: Profile P5
Figure 7: Profile P6
Figure 8: Profile P7
Figure 9: Profile P8
Figure 10: Profile P9
Figure 11: Fine earth densities of all horizons of transect 1
Figure 12: Distribution of soil particles in Ah horizons of transect 1
Figure 13: Distribution of soil particles in subsoil horizons of transect 1
Figure 14: pH value of all horizons of transect 1
Figure 15: Contents of a) SOC and b) TN of Ah horizons of transect 1
Figure 16: SOC content of subsoil horizons of transect 1
Figure 17: TN content of subsoil horizons of transect 1
Figure 18: a) ECEC and b) the percentage of cations in Ah horizons of transect 1
Figure 19: ECEC of subsoil horizons of transect 1
Figure 20: Percentage of exchangeable cations of subsoil horizons of transect 1
Figure 21: Fine earth densities all horizons of transect 2
Figure 22: Distribution of soil particles in Ah horizons of transect 2
Figure 23: Distribution of soil particles in subsoil horizons of transect 2
Figure 24: pH value of all horizons of transect 2
Figure 25: Contents of a) SOC and b) TN of Ah horizons of transect 2
Figure 26: SOC content of subsoil horizons of transect 2
Figure 27: TN content of subsoil horizons of transect 2
Figure 28: a) ECEC and b) the percentage of cations in Ah horizons of transect 2
Figure 29: ECEC of subsoil horizons of transect 2
Figure 30: Percentage of exchangeable cations of subsoil horizons of transect 1
List of tables
Table 1: Red soils in China (Source: SHI et al. 20061; HE et al. 2004a2)
Table 2: Nutrients distribution of red soils in China (Source: HE et al. 2004a)
Table 3: Soil properties of P1
Table 4: Soil properties of P2
Table 5: Soil properties of P3
Table 6: Soil properties of P4
Table 7: Soil properties of P5
Table 8: Soil properties of P6
Table 9: Soil properties of P7
Table 10: Soil properties of P8
Table 11: Soil properties of P9
Table 12: Total contents of nutrients of all profiles of transect
Table 13: Total contents of nutrients of all profiles of transect
Table A 1: Coordinates of the profiles
Table A 2: Data of profile 1 (Hui Lao Xin Zhai)
Table A 3 Data of profile 2 (Gei Yang Gong Di)
Table A 4: Data of profile 3 (Beng Gang Lahu)
Table A 5: Data of profile 4 (Beng Gang Hani)
Table A 6: Data of profile 5 (Cha Chang)
Table A 7 Data of profile 6 (Na Ban, rubber old)
Table A 8: Data of profile 7 (Na Ban, paddy field)
Table A 9: Data of profile 8 (Man Dian)
Table A 10: Data of profile 9 (Jiang Bian Zhan)
The Naban River Watershed National Nature Reserve
1.1 General introduction
The Naban River Watershed National Nature Reserve (NNNR) is one of several nature reserves in the Dai Autonomous Prefecture of Xishuangbanna in the south of Yunnan province. The prefecture is located between 21°8`N to 22°36`N and 99°56`E to 101°50`E covering an area of 19.223 km2. In the southwest and south east Xishuangbanna borders Myanmar and Laos (Fig.1).
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Figure 1: Location of Xishuangbanna and the counties Menghai, Jinghong, Mengla
Yunnan is shaped by the southern part of the Hengduan Mountains (APEL, 1996; YUNNAN SOCIETY OF ECOLOGICAL ECONOMICS et al., 1992). Approximately 95 % of the province consists of mountains and hills, only 5 % are flat plains and river basins (WANG, 2000, with elevations ranging between 420 and 2,400 m asl.
In Xishuangbanna typical land formations are mountainous and hilly areas combined with plains. Large valleys can also be found here, which are mainly surrounded by hilly areas or single hills (ACHILLES, 1997; YUNNAN SOCIETY OF ECOLOGICAL ECONOMICS et al., 1992).
The major river of the area is the Mekong River or Lancang Jiang with its headwaters in Tibet. The Mekong catchment is characterized by several tributaries, such as the rivers Luoso, Nanla and Liusha. In total, 2,762 rivers are influencing the variety of landscapes in Xishuangbanna (WU & OU, 1995; YUNNAN SOCIETY OF ECOLOGICAL ECONOMICS et al., 1992; ZHANG, 1986).
The nature reserve covers an area of 267 km² and is located 20 km northwest of Jinghong City, the prefecture capital of Xishuangbanna. It extends between 22°04`N to 22°17`N and 100°32` to 100°44`E. The reserve encompasses an altitude range of 539 m to 2,304 m a.s.l., with an estimated 90% of the area situated between 600 m and 1500 m a.s.l. The western and central parts of the reserve belong to the Naban River watershed, whereas the eastern slopes drain directly into the Mekong River.
1.2 Geology
Geologically, the reserve can be divided into two parts. The western part is dominated by granite as the main parent material, while the eastern part mainly shows phyllites.
1.3 Soils and nutrients
The investigated area is located in the so called Red Soil Region of China. With an area of 2.6 Mio km2 this region accounts for nearly 20 % of China`s total area (WILSON et al. 2004) and is mainly distributed in the subtropics and tropics of China.
Chinese Red Soils build up four groups: Latosols, Lateritic red earths, Red earths and Yellow earths. Table 1 gives an overview of the groups and their equivalences according to the World Reference Base for Soil Resources (WRB) (FAO/UNESCO 1998).
Table 1: Red soils in China (Source: FAO/UNESCO 19981; SHI et al. 20062;
HE et al. 2004a2)
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Chinese red soils are subtropical and tropical soils which are strongly weathered, thus showing strong leaching of nutrients. The soils are characterised by high contents of so-called low active clays as well as accumulation of Al and Fe oxides and hydroxides. A commonly low content of organic substances (OS) can lead to a lack of total nitrogen (TN). Red soils often show a deficiency of plant available P, due to the high content of Al and Fe oxides as well as kaolinite causing a strong adsorption of P (He et al. 2004b). As a result of the already mentioned strong weathering and leaching the soils have low cation exchange capacity (CEC) and low base saturation (BS) as well as low water-holding capacity (WHC) (HE et al. 2004a, WILSON et al. 2004).
Table 2: Nutrients distribution of red soils in China (Source: HE et al. 2004a)
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According to ANONYMUS (1987, in APEL, 1996) five major soil types were found in Xishuangbanna, which can be classified as three zonal (dependent on altitude) and two azonal types. The zonal soil types are „brick-red soils“ at altitudes of 600 to 900 m a.s.l., „yellow-red soils“ or „red soils“ between 900 to 1.600 m a.s.l., and „red mountain soil“ above 1.600 m a.s.l.. Applying the FAO-Classification all three soil types are Ferralsols with different contents of iron oxides (APEL, 1996).
APEL (1996) states that azonal soil types are calcaric soils and purple soils. Purple soils are according to WRB Regolsols derived from devonian clay shale and show high contents of mangan. The non zonal soils show only very small distributions in Xishuangbanna. Next to the named soil types also alluvial soils as well as Gleysols and Planosols can be found in valleys and depressions (BRUENIG et al., 1986).
2 Material and methods
2.1 Field investigations
Field investigation and soil sampling were conducted in November 2009.
2.1.1 Site selection
The aim of the investigation was to characterize typical soil types in dependence of the geomorphology (altitudes, geology) and selected land use types (forest, rubber plantation, paddy field, waste land) in the NRWNNR. As forests are a target land use type investigated in the LILAC project the influence of geomorphology was mainly assessed under forests of different altitudes by setting up a transect 1 in the western part of NRWNNR from Hui Lao Xin Zhai (approx. 1000 m a.s.l.) to Beng Gang Ha Ni (approx. 1700 m a.s.l.). Whereas the influence of land use types were investigated in the eastern part of NRWNNR by analysing a transect 2 around the villages Na Ban and Man Dian. Here all profiles were located at altitudes between 660 to 703 m a.s.l..
2.1.2 Soil profile description
After establishing the soil profiles all characteristics were noted and the profiles were described by following the WRB guidelines of soil description (FAO, 2006a) as well as the German soil description guidelines KA5 (Ad hoc AG Boden, 2005).
2.1.3 Soil sampling
After determining the horizons at each profile three mineral soil samples were taken at each horizon by using three soil corers with a volume of 100 cm3. The three samples were then given into a plastic bag and thoroughly homogenized to a mixed sample. After weighing all fresh samples, the plastic bags were opened and stored at the research station in Naban village for air drying before transportation to the laboratory for following analysis. Here the samples were then oven-dried for 48 h at 40 °C.
2.2 Laboratory analysis
2.2.1 Bulk density, fine earth density, water content
The bulk density (BD) was determined by weighing the field-wet samples and calculated by using the known volume of the soil corers:
fresh weight (g)
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BD = (1)
volume (cm3)
After drying the samples were passed through a 2 mm sieve to remove roots and gravels >2 mm. The fine material was weighed in order to calculate the fine earth density (BDf) with:
air dried weight (g)
BDf = (2)
volume (cm3)
The soil water content (WC) is is the ratio of the mass of water in the soil samples to the mass of dried soil. It is determined by drying method by 105 °C and calculated as follows:
Mw - Md
WC (%) = x 100 (3)
Mw
with WC = Gravimetric water content (%)
Mw = Mass of the air-dried soil sample (g)
Md = Mass of the soil samples dried with 105 °C (g)
2.2.2 Texture
By using the combined sieving and pipetting method (DIN ISO 11277) the particle size fractions of the soil samples were determined. Therefore, organic matter was dissolved with 30 % H2O2 with a following dispersion with Na4P2O7 solution. Dissolving of the CaCO3 contents were not applied because of the insignificant quantities of carbonate (＜ 2 %).
2.2.3 pH value
The pH value was measured with a glass electrode. The soil was thoroughly mixed with deionized water with a ratio of 1:2.5.
2.2.4 Soil organic carbon (SOC) and total nitrogen (TN)
For determining the contents of total carbon (TC) and total nitrogen (TN) the soil samples were dried at 40 °C and milled before applying a complete dry combustion with a CNS analyzer (Vario EL III / elementar, Heraeus). According to the measured ph values it was assumed that the content of carbonates could be neglected. To verify this assumption the carbonate contents of randomly chosen samples showing pH values above 5 were measured. Here all contents were below 2 %, confirming our presumption. Thus, the total carbon content (TC) corresponds to the content of soil organic carbon (SOC).
2.2.5 Nutrients
Aliquots of all soil samples were dried at 105°C. Subsequently HNO3 (65 %), HF (40 %) and HClO4 (70 %) were added for using the microwave decomposition before determination of element contents at an ICP AES (Spectro Ciros).
2.2.6 Cation exchange capacity
The effective cation exchange capacity (ECEC) has been measured by exchanging the cations with 0.5 M NH4Cl solution and subsequent filtration through a 0.45 μm membrane filter. The extract has been analysed with the ICP AES Spectro Ciros equipment to determine the ECEC as the sum of the hydrogen (H+) and the positively charged elements (K+, Na+, Ca2+, Mg2+, Mn2+, Al3+ and Fe3+) per g soil. The base saturation (BS) is the sum of the percentages of the base cations (K+, Na+, Ca2+ and Mg2+) (SCHEFFER and SCHACHTSCHABEL, 1998).
3 Results
3.1 World Reference Base
The World Reference Base for Soil Resources (WRB) is the successor to the International Reference Base for Soil Classification (IRB). Its task is to apply the IRB principles of definition and linkages to the existing classes of the Revised FAO-Unesco Soil Map of the World Legend (FAO/UNESCO, 1988) (SPAARGAREN and DECKERS, 1998).
The main objective of the World Reference Base for Soil Resources is to provide scientific depth and background to the Revised Legend, so that it incorporates the latest knowledge relating to global soil resources and interrelationship. Specially the following objectives (SPAARGAREN and DECKERS, 1998):
- to develop an internationally acceptable framework for soil resources, to which national classification systems can be related and through which the national systems can be linked;
- to enable the international use of pedological data, not only by soil scientists, but also by other users, such as geologists, botanists, agronomists, ecologists, foresters, farmers, etc.;
- to acknowledge important lateral relationship of soils and soil horizons as characterized by topo- and chronosequences; and
- to emphasize the morphological characterization of soils rather than to follow an approach purely based on laboratory analyses.
In the WRB soil characteristics, properties and layers, which are in combination, are used to describe and define the reference soil groups and soil units. Soil characteristics are parameters, observed or measured either in the field or the laboratory, including color, texture of soils, features of biological activity, voids, mottles as well as analytical measuring (pH, particle distribution, exchangeable cations, exchangeable cation capacity, …) (SPAARGAREN and DECKERS, 1998).
Soil properties are combinations of soil characteristics and considered to be indicative of soil forming processes (e.g. vertic properties are a combination of heavy texture, smectitic mineralogy, gilgai, slickenside, hard consistence when dry, sticky consistence when wet, shrinking when dry and swelling when wet) (SPAARGAREN and DECKERS, 1998).
Soil horizons are certain depths, which are characterized by one or several properties with a certain degree of expression. The thickness of each horizon is varied, ranging from a few centimeters to several meters, and the boundaries of horizons are diffuse, gradual, clear or abrupt (SPAARGAREN and DECKERS, 1998).
Reference soil groups (RSG) are defined by a vertical combination of horizons within a certain depth. In the WRB 30 reference soil groups were firstly proposed in 1998, namely Histosols, Cryosols, Anthrosols, Leptosols, Vertisols, Fluvisols, Solonchaks, Gleysols, Andosols, Podzols, Plinthosols, Ferralsols, Planosols, Solonetz, Chernozems, Kastanozems, Phaeozems, Gypsisols, Durisols, Calcisols, Albeluvisols, Alisols, Nitisols, Acrisols, Lixisols, Umbrisols, Cambisols, Arenosols and Regosols (SPAARGAREN and DECKERS, 1998).
3.2
Soil profile description
3.2.1 Profile 1
P1: Hui Lao Xin Zhai
Ferralic Cambisol (sodic, humic, eutric, chromic)
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According to WRB (FAO, 2006) a cambic horizon was defined as diagnostic horizon. As prefix ferralic was chosen because of a very low ECEC. Sodic and eutric were identified as suffixes indicating a higher percentage of Na and Mg on the exchange complex and a base saturation > 50 %.
Figure 2: Profile P1
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