Karst Ecological System of Jinfo
Mountain of Chongqing

Kuang Mingsheng1 Cao Jianhua2 Xie Shiyou1 Li Linli1 Dai Yanan1
Fong Shaoguo1Zeng Yan1 Zhou Bei1 Lu Honghai1 Jia Yanan1
(1 School of Environment and Resources ofSouthwest Normal University, Beipei, Chongqing and 2 Karst Dynamics Laboratory, MLRC, Guilin)

1. Environmental background of karst ecosystem in Jinfo Mountain
1.1 Introduction

Jinfo Mountain lies in the south of Chongqing. Its coordinate is 28o25'-29o20'N and 107o-107o20'E. It's in the subtropical humid monsoon zone. Jinfo Mt. area became a key scenic spot and historical site of China in 1988, and ranked the national forest garden of China in 1991. The area of the main scenic spots occupied 441km2(Fig.1). It is in the charge of Nanchuan city of Chongqing.
Jinfo Mt. is located in the southeast of Sichuan Basin. The elevation of the highest peak, Fengchui peak, is 2251.1m asl. Its relative height is 1300m-1500m. In Jinfo Mt. area, because of the influence of limestone distribution and vertical climate, the karst ecosystem can be group into two types: A. subtropical karst ecosystem in the low part of Jinfo Mt.; and B. temperate karst ecosystem on the surface of plateau.
A. Subtropical karst ecosystem in the low part of Jinfo Mt.
The limestone and dolomite of Cambrian and Ordovician are composed of the material basis of the karst development in the low part. Lots of large springs, stalactites inside or outside caves and the tufa deposit near the spring outlets indicate the karst process in low part is stronger under the good condition of water and heat than that on the surface of plateau. In the meanwhile, large number of the small- and microforms(karren and grike, for example) can be often found on the rock surface.
B. Temperate karst ecosystem on the surface of plateau
The material basis of karst development in the upper of Jinfo Mt. is Permian limestone. On account of the high elevation and low temperature, the modern karst development is poor. The table1 shows the difference of air temperature/water temperature/HCO3 concentration and pH value of spring water between the both karst systems.

Fig.1 Distribution of the scenic spots and historical sites of Jinfo Mt.
Serial No. shows the stops which will be viewed in the excursion
Seen from the Tab.1, all of the air T./water T./HCO3 concentration of spring water A is higher than those of B. This is suggested that the stronger biological activity of A could result in more CO2 to drive the karst process and accelerate the carbonate rock erosion. Comparatively, the low HCO3 concentration (1.5mmol/l) and poor erosion result from the weak biological activity and low soil CO2 content of B. And near the outlets of springs, tufa couldn't be found.

 Table.1 The chemical character of the Karst water at different height of the Jinfo Mountain

Position

Spring

Air T(oC)

Water T(oC)

HCO3

(mmol)

pH value

Low part

Bitan Spring

22.8

14.6

3.1

7.91

Xilai Temple Spring 1

 

13.0

2.61

7.68

Xilai Temple Spring 2

 

7.4

3.0

7.74

Jinlin Hotel Spring

11.3

10.3

2.9

8.33

Upper part

Zhongdui Spring

7.0

9.1

1.3

8.18

Qiaotangheba Sping

7.2

8.0

1.5

8.23

Liutatang Spring

8.5

7.9

0.9

7.77

Heifeng Cave Sping

7.0

7.8

1.3

8.03

Fenghuang Temple Spring

6.7

6.9

0.8

7.74

By the way, the large forms of karst geomorphology can be found in B. The large forms include karst depression, stone forest and cave, underground river. Furthermore, there are 5 cave systems in 12Km2 around the highest peak of Jinfo Mt.---Fengchui Peak. Obviously, these don't correspond with the condition of temperate climate and hydrological condition of B. This is the reasonable explanation of the karst process under humid and warm condition in geological history, and the uplift of the Jinfo Mt. during the new tectonic movement.
On the basis of its characters, Jinfo Mt. has been one of the monitoring spots of karst dynamic system in China. In order to deeply understand the karst ecosystem of Jinfo Mt., the geology, geomorphology, soil, vegetation, climate and karst history will be briefly elaborated as the following.
1.2 Geology and geomorphology
Jinfo Mt. is a syncline mountain. The platform and terrace are composed of Permian limestone (P1) in the upper part with about 2000m a.s.l. In the meanwhile, karst geomorphologies in large scale on the surface or underground are found. The shale and sandstone of Silurian lay in the middle of Jinfo Mt. from 1000m to 1500m asl.. The low part of Jinfo Mt. is supported by the limestone and dolomite of Cambrian and Ordovician. Plenty of small- and microforms of karst are formed in this area. There are many cliffs and gorges in Jinfo Mt., the north slope is steep and the south slope is slight. The geomorphology of the Jinfo Mt. can be divided into two types:
Gorge in the low part of Jinfo Mt. whose elevation is about 800-1200m asl and relative height about 500m. It formed by water down cutting and eroding.
Platform of Mid-mountain distributes the area above 1200m asl of Jinfo Mt., Bozhi Mt. and Qingba Mt.. The relative height is 500-1000m. The way of the mountain extension is identical to the tectonic line. The top of the Mts. is a relic erosional basis.
1.3 Soil and vegetation
The patent rocks of the soil in Jinfo Mt. area are limestone, siltstone and shale. Under the influence of the vertical climate, the distribution of soil also exhibits in vertical zones. From the foot to the top, the soil is yellow soil, dark yellow soil, yellow brown soil and brown soil, respectively. And the altitude of their spatial distribution is 600m-1200m, 1200m-1700m, 1700m-1800m and above 1800m asl, (Fig.2).

Fig.2 sketch of the soil distribution in Jinfo Mt.
The yellow soil was formed in the subtropics monsoon climate, and with the cover of the mixed forest of evergreen broad-leaves and deciduous broad-leaves. Its pedogenic process is controlled by the allitic weathering and biological action. The upper layer of this soil is in dark gray or in brown-yellow and the lower layer in yellow.
Dark-yellow soil developed under the warm deciduous broad-leaves forest. Because the biological activity is weak, organic material could be collected in the soil and the organic material of the soil could reach 2-7%.
Brown soil distributes the area above 1800m asl in the Jinfo Mt.. It developed under the deciduous broad-leaves forest. Its pedogenic parent rock is mainly Permian limestone. The yellow-brown soil comes into being at the interaction zone between yellow soil and brown soil. The podzolizaion phenomenon can be gradually found in the subsurface of soil with the elevation rising and air temperature dropping. In the glacis and complanate land, the soil is very thick. There is sparse subalpine meadow soil in the complanate land or depression.
Yellow-brown soil is the soil which is situated the area between dark-yellow soil and brown soil, and its character is also between them.
As the result of the influence of the vertical climate, there are many types of plant communities in Jinfo Mt. area, and their distribution is also of in vertical zone. The plant species, which has identified, is more over 5000, and about 2100 species can be used to produce Chinese medicine. The species of wild animal is more over 500 species. There are 16 plant communities developing in karst area. Their spatial distribution is 8 communities above 1800m asl, 5 communities from 1800m asl to 1500m asl and 3 communities below 1500m asl. The detail data of the structure and spatial distributive map of these communities is shown in appendix1.
1.4 Climate and hydrology
Jinfo Mt. is in subtropical humid monsoon zone with mild air temperature, plentiful rain, short sunshine, more fog, long rainy time and high humidity. The vertical change of climate is notable from the foot to top. In the upper part, its annual average air temperature is 8.5oC and the annual mean rainfall is 1395.5mm. Rainy season is from April to October. In the lower part, the annual air temperature is 16.6oC and the annual mean rainfall is 1286.5mm. The seasonal change of the air temperature and rainfall in the upper part of Jinfo Mt. is shown in figure.3.
Fig.3 Seasonal change of air temperature and rainfall in the upper part of Jinfo Mt.
Jinfo Mt. lies in the axis of the placid syncline. The upper part of it is composed of the Qixia formation limestone of Permian. In south China, the karst development could be strongest in this limestone strata. Therefore, both ground and underground karst hydrogeological system collocate in the upper part of it. The way of water cycle in this system is that rain water enters underground karst aquifer bed through depressions and sinkholes. And then, the underground water smoothly moves in bedding surface, conduit and interface between limestone and sandstone (shale). Finally, the underground water discharges from the outlets of the underground rivers or karst springs which develop on the cliff (figure4).
Fig.4 karst water cycle in the upper part of Jinfo Mt.
The lower limit of karst development don't be controlled by the regional erosional basis, but dominates by the water-resisting layer of Silurian sandstone and shale. As the result of the small recharge area and short water cycle way, the flux of water is limit and its change is quick. In the meanwhile, the high elevation and low temperature result in weak biological activity, low CO2 concentration in soil and low HCO3 concentration in water. This indicates the karst process is slow. Comparatively, in the low part of Jinfo Mt., the chemistry of karst water is impacted by allogenic water from the upper shale and sandstone formation of Silurian. The HCO3 concentration becomes higher and higher with the elevation decreasing and the tufa deposit in the outlets of springs gradually comes out.
1.5 History of karst development
In this area, the sea ingression was over at the late of Triassic, and then the relevant strata increasingly uplift from sea to became land. During the Yanshan Movement, the outline of geomorphology of Jinfo Mt. area formed. The strata of Triassic was weathered when the crust kept stable for a long time after Yanshan movement. And then, the Permian limestone exposed. During the Himalaya Movement, the crust continuously uplift for many times. The earlier karst geomorphology was reconstructed. According to the research, the history of karst development can be briefly divided into 4 phases: 1. Before Quaternary, the terrain of the top of the Mt. above 2100m asl were formed; 2. In early Quaternary, depression/doilne/sinkhole and cave(Gufo cave, for example) were formed; 3. In the middle Quaternary, cliff/conduit in the low layer of cave system and gorge were formed; 4. In the late Quaternary, brook and stone forest were formed.
2 Field excursion route of karst ecosystem
2.1 Geological and geomorpholgical introduction from Chongqing to Nanchuan
Beibei-Nanchuan area is located in the parallel broom-like fold belt in the east of Sichuan Province. The climate in this area belongs to subtropical climate. The major vegetation is subtropical evergreen broad-leaved forest. Sichuan tectonic movement contributed to the formation of a group of northeast-toward folds in the east of Sichuan, which comprises about 20 parallel anticline mountain ridges and syncline valleys. The elevation of these mountains varies from 700m to 1000m a.s.l. The rocks of these mountains are composed of limestone and sandstone of Mesozoic. When the sandstone was eroded, the limestone was exposed and formed trough valleys by karst processes with small well-developed karst landforms. Between Anticline Mountains there are parallel syncline valleys containing hills and terrace with elevation ranging from 180 to 250m a.s.l., the strata is composed of sandstone and shale of Silurian (Fig.5) Yangtze River and Jialing River flow through the syncline rocks to form strathes and flow through anticline to form gorges(Photo II-1, 2). The route from Beibei to Nanchuan is divided into two sections: one is from Beibei to Fuling and the other is from Fuling to Nanchuan.
A. Beibei-Fuling
The region is situated in the typical parallel mountain and hill belts. We will visit Zhongliangshan, Tongluoshan, Mingyueshan, Huangcaoshan, Baiyanshan anticlines successively. The rocks of these anticline mountains are sandstone of Xujiahe formation, dolomitical limestone of Leikoupo formation, limestone of Jialingjiang formation and marlite of Feixianguan formation of Triassic system. The rocks of syncline valleys among the anticline mountains are purplish red mudstone and siltstone of Shaximiao Formation of Jurassic (Fig.6). The hilly land is in the syncline valley.
Fig.5 Sketch of geomorphology from Beipei to Nanchuan
Fig.6 The profile of geology and geomorphology from Beipei to Fuling
B. Fuling-Nanchuan
The section is in a valley. The wel-developed vegetations on both sides of highway are pine, cypress and linden. The exposed dominant rock exposed is shale and sandstone of Jurassic. The carbonate rock of Trassic emerges near the Fuling and the carbonate of Cambrian and Ordovician exposed between Nanchuan and Jinfo Mt.. In karst area, the depression, sinkhole, cave and hill-peak develops well. (Fig.7).
2.2 Wolongtan Gorge(Stop 1 in Fig.1)
Wolongtan Gorge (photo II-3) is located in the northern foot of the Jinfo Mt. (Sanquan Town). It is formed by long-term water erosion and down cutting of Longhuxi River. In the gorge, marvelous karst landscapes, such as "a gleam of sky", strange stones, dangerous shoals are found. The gorge is composed of the limestone of Cambrian and Ordovician. The typical giant curtain tufa develops on the rock wall, and the plant community is the subtropical evergreen broad leaves, Besides, subtropical animals such as "Hou'er Slope" and Andnas davidianus can be seen in the gorge. The whole length is 3km, and now the length permitted to visit is about 1.2km (Fig.8).
2.2.1 Biologicalcommunity features
Influenced by Indian Ocean and Pacific Ocean monsoon climate, the karst vegetation in the gorge is characterized by subtropical plant community. The community is composed of arbor Sloanea sinensis
Phoebe nanmuFicus tsiangii , herb dominant species of Urticaeae and a lot of fern. Some of them have features of tropical plants: for example, there are many white villus growing on the back of the leaves of Phoebe nanmu; the flowers and fruits of Ficus tsiangii grow on the stems (photo II-5). The fruits of the Coffea arabical of Rubiaceae can also produce on the stems.
Besides the karst vegetation, the main kinds of wild animals in the gorge are butterflies, monkeys, wild goats and deer.
2.2.2 Giant salamander pond
Giant salamander belongs to Amphibia class, Urodela order, Cryptobranchidea family, Megalobactoachus genus. Giant salamander (Andnas davidianus) mainly distribute in ravine with an elevation about 1000m a.s.l where there is little human trace. It gets its Chinese name (Wawayu), which means "infant fish", for its infant-like cry and feet. It likes dark places in pure spring and afraid of light and noise. Therefore, it hides in cave in the day, looks for foods at night. Its main foods include fogs, fish, snakes and mice. "infant fish" fed in the pond is 52 years old and its total length is1.32m, total weight is 25kg. (Photo II-4)

Fig.7 The geological profile of Fuling-Jinfo Mountain, Nanchun
Fig.8 The geologic and geomorphological of sectional map from
Wolongtan gorge to the top of Jinfo Mt.
2.2.3 Giant Curtain tufa
A large area of calcareous tufa is developed in the gorge (Photo Ⅱ-6). It is stalactite-like and grows on cliff. Therefore, it is sometimes called outside-cave stalactite. Some elements, such as climate, photosynthesis, and the variation of CO2 content in the water are closely related with this kind of stalactite formation. It formed more easily and grows evidently in the warm and humid condition with heavy forest. In this gorge, the geological bed rocks are limestone of Cambrian and Ordovician; The luxuviant plant, plenty water, powerful photosynthesis, will help the tufa to form, and high CO2 concentration in water.The pH values and HCO3- concentration of karst water here is 8.36 and 3.6mmol/L, respectively. This is the reason why calcareous tufa is so evident.
2.2.4 A gleam of sky
"A gleam of sky" is the result of water down cutting and eroding with the crust continual uplift. You can see a gleam of sky when you look up. Plenty of vegetation on both sides and many strange stones enrich the beauty and peace of the gorge.
2.2.5 The rehabilitation of karst ecosystem (Stop 2 in Fig.1)
The north slope of Jinfo Mt. is very steep. Destroyed forest has caused a series of environment problem, such as collapse, water and soil erosion. Since the environment of this area is very fragile, it is very difficult to recover. In the movement of Development of West China, the government carried out a policy that tilled fields over steeper 25o must be restored to forests. "Providing Work as a Form of Relief" has been put into practice for rebuild the environment according to the condition of the Jinfo Mt.. "Providing Work as a Form of Relief" is a plan of rehabiliting the forest in which the government pays and peasants plant. The government pays 350 kg food supplies and 50
per acre for 5 years. Peasants take share of the plants and make use of and manage the land. This is an effective measure; it may not only solve the living problem of the peasants, but also turn the peasants into protector of the forest.
2.2.6 Huangcao Ping (Stop 3 in Fig.1)
Huangcaoping is well knonw for Schefflera octophylla (Photo II-7), which is a precious arbor plant. It is named for its goose's palm, on account of its leaf like goose's foot. It is considered an evidence of the continental drift theory and living fossil. At present it is a protection plant with the second degree and a relic species. There are only two species on the earth, which occurred in China and North America. Chinese tulip tree likes warm environment, the altitude of the Schefflera octophylla distribution is 1200m to 1800m in Jinfo Mountain area, the optimum altitude is between 1500m and 1600m.
2.3 The Gufo (Old Buddha) Cave (Stop 4 in Fig.1)
The Gufo Cave couples with Xiannu (fairy maiden) Cave to form a cave system with 3777.7m long (figure 9). The projective area of the cave ground occupys 50000m2. The cave system has 6 entrances, 3 of them are large on the cliff, with the largest one of 74m wide and 14.5m high. The other three entrances are small passages which are in the mid-slope of depression. The traveling entrance is under the Fengchui (windy) Mountain with the altitude of 2120m asl. It is the highest cave in south China. After the 72 turns through the small passage, you may enter a big hall with 10-60m wide and 5-19m high(Photo II-8). The air temperature of the cave is 6.2-8.6oC, the relative humidity is 80-90% and the CO2 concentration of cave air is 490-620×10-6. Some minerals of sulphate(CaSO4.H2O, MgSO4.7H2O, Na2SO4.10H2O) are found in the cave speleothem. These attribute to the oxidation of the FeS2 in coal layer which exists in the upper bed of Permian. Under catalysis of the sulfur bacteria, the reaction was accelerated.
4FeS2
15O214H2O--- 4Fe(OH)38H2SO4
8H2SO4
8CaCO3.H2O--- 8CaSO4.2H2O8CO2
Fig.9 Plan map of Gufo-Xiannu cave system(from Zhang Ren, et al, 1998)
2.4 Subalpine meadow (Stop 5 in Fig.1)
There is thick soil in the karst depression in the upper part of Jinfo Mt. above 1950m asl. The subalpine meadow develops on the soil. The dominant species is Sasa nubigena. The species of Anaphalispterocanlon, Seneciocacaliaefolius and Geranum yezaense are also commonly found in the community. And many of them are Chinese medicine.
2.5 Karst depression (Stop no.5 in Fig.1)
The top of the Jinfo Mountain is an ancient erosional basin. There are a lot of karst land forms on the plain. Karst depression is one of the typical karst forms. Yaochiba, for example, is a large depression which is of a big flat plain. Meanwhile, sinkholes can be found at the bottom of the depression. (figure.12)
2.6 Ecological stone forest (Stop 6 in Fig.1)
The formation of karst stone forest is the result that the limestone with gentle occurrence and many vertical joints was eroded on the surface and under the soil by the rainwater, soil solution with CO2 and the action of microorganism. The stone forest under the soil came into being when the upper soil was washed out. Many stone forests have been attractive traveling spots. The stone forest of Jinfo Mt. is on the top of Jinfo Mt.. It obviously does't correspond with the modern climate of the top of Jinfo Mt. The formation of stone forest was before or at the beginning of the Jinfo Mt. uplift. The stone forest was rebuilt and plant community developed after the rising of Jinfo Mt.. This is absolutely different from the case of Yunan Stone Forest, which will be visited later.
The prosperous plants cover the stone forest. The predominant species of the community are B.sinica (Rehd.et Wils) Cheng, Rhododendron spinuliferum, R.decorum, Quercus engliana and so on. In this community, there are many special species of Rhododendron which are only found in Jinfo Mt.. Furthermore, there is a ancient relic species Taxus shinensis in this community. The flourishing moss grows on the surface inside the forest. The moss could absorb moisture from air and keep the rock surface wetting. Moreover, the moss, on one hand, accelerates the limestone weathering, on the other hand, provides nutrient components for tree growing. This is the reason of the ecological stone forest formation.

Fig.12 Distribution of the karst depression on the top of Jinfo Mt.
2.7 Small Salamander Spring nearby the Fenghuang (Phoenix) Temple, Jinfo Mt. (Stop 7 in Fig.1)
Small salamander spring, nearby the Fenghuang temple, is located at the top of Jinfo Mt. with the elevation 2200m asl. The communities of S.sinensis (hemsl) Airy-shaw-R. coeloneurum Fiels - cyclobalanopsis lauca and castanopsis plantycantha - R. chienianun Fang - I.macrathum A.C.Smith, are living surrounding. The soil is mainly yellow-brown soil.
Compared to Shuanglongdong spring, the data (figure.11) based on the results of continual monitoring (July 24--July 25, 2001), indicates the water temperature (9.1-9.9℃) slightly decreases and conductivity (114-118us/cm) greatly decreases, and pH value (7.45-7.56) of the Small Salamander Spring are all lower. This results from the higher elevation of small salamander spring

Fig.11 Variations of water temperature,conductance and pH value of Small Salamander Spring from continual monitoring(July 24-July 25, 2001)
2.8 Cathaya argyrophylla forest (Stop 8 in Fig.1)
Cathaya argyrophylla forest lies in the south slope of Jinfo Mt. from 940m asl to 1870m asl. The attractive phenomenon is a large tree cathaya argyrophylla growing on the remaining limestone block which is more than 30m in height and 20m in breadth. The leaves of the Cathaya argyrophylla is needle-like and there are two white pneumatophores at the back of leaves. This indicates that the Cathaya argyrophylla is a relic species from xerophyte(living in hot and dry climate)(photoⅡ-9).
Cathaya argyraphylla is ancient species. According to the investigation, the Cathaya argyrophylla came into being at the beginning of Cretaceous of Mesozoic. From the Cretaceous of Mesozoic to Tertiary of Cenozoic, Cathaya argyrophylla had spread widely in Northern Hemisphere. Unfortunately, the glacier had developed greatly in Northern Hemisphere since Quaternary, which caused luxuriant forest to be vanished. However, Jinfo Mt. has complex terrain. Furthermore, the Qinling Mt., like a great barrier, located in north of Jinfo Mt.. It could block the attack of the cold air current from north. Therefore, many ancient communities or special species can be protected. And 6 Cathaya communities including Rhododendron spinuliferum,R.decorum, Rhododendron spinuliferum, R.decorum, are still growing in Jinfo Mt. at the present. Cathaya provides the material for studying the origin, development and succession of Chinese vegetation.
Cathaya argyrophylla belongs to the Pine family and Cathaya genus which can only be found find in Jinfo Mt., Chongqing, Baima Mt in Wulong, Chongqing and Huaping, Guangxi. It is a rare species which has become extinction in other places of the world, so it has been considered as the treasure of the world: "living fossil", "pearl in the forest", ''panda of plant". Cathaya argyrophylla becomes a protection species with the first degree in China.
2.9 Nantian Stone Gate (Stop 9 in Fig.1)
It is located in the south slope near the top of Jinfo Mt.. It looks like arc gate. So, local people call it 'Nantianmen'(photo Ⅱ-10). Its formation may attribute to the underground river development, the crust uplift and the cover rock weathering. The stone gate, in fact, is a part of 'old underground river'. The plant community around the stone gate is composed of castanopsis plautycatha, Castanopsis platycantha and Schmaargentes. There are 3 different layers in this community. The up-layer is composed of Castanepsis plauty catha and Schmaargentes. The Castanepsis plauty catha is a tree with its largest crown 10m×8m and uppermost height 16m. Comparatively, the Schmaargentes is a tree with its largest crown 8m×7m. The dominant species of the mid-layer is Rhus sylvestris, Symplocos caudate. The secondary species is Eurya sp., Phoebe chinensis Camellia sp. Qqercus engliana. In the low-layer, the dominant plant is herb, meanwhile, a lot of fern are also found, such as Coniogramme intermedia and Athyrium sp..
2.10 Shuanlongdong Spring (Stop 10 in Fig .1)
Shuanlongdong is located at the south slope in the upper part of Jinfo Mt. with elevation 1500m asl. The Shuanlongdong spring is composed of two small springs flowing out from the wall on both sides of the valley. One is falling down from the cliff about 10m above the ground. The other is out of the interface between limestone of Permian and shale and sandstone of Silurian with the same altitude. The spring looks like two dragons to spray water together. So, local people call it " Shuanlongdong "spring. Its discharge is very large, and has been applied for generating electricity and irrigation. Now it has become the main water source of Toudu water power station.
There luxuriant Chimonobambusa utilis (a kind of baboo) grows around the spring.
The concentration of HCO3- of the spring is about 1.4mmol/l. The results of continual monitoring for 36hrs (July 24-July 26) indicate that the water temperature, almost kept stable, and the pH value of spring water decreased slightly, while the conductivity increased gently (figure10).

Fig.10 Variations of water temperature, conductivity and pH value of Shuanlongdong spring from continual monitoring(July 24-July 25, 2001)
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