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2005 Vol.3 No.4
Published 2005-12-31
Articles
1
LIU Geng-Ling
Agriculture and soil conservation in China
More than 2000 years history of agriculture in China has demonstrated that the grain yield could be sustained and the soil productivity could be maintained and gradually improved through recycling the organic manure. The input of non-agricultural fertilizers is in a most effective way to increase the crop yield. But there is a tendency in some regions that the farmers prefer only chemical fertilizer. The long-term application of chemical fertilizers will cause main soil problems and exert a bad influence on crop quality and human health. Particular attention should be given to the application of the organic manures so as to improve soil properties and to develop sustainable agriculture. Human creates agriculture and agriculture fosters the humankind. In order to make the resources and environments get into the right track of circulation, human is one component of nature, not the opposite. Based on the long-term experiments on red soil in hilly area in the southern part of Hunan province, the restoration of natural vegetation was extremely important for soil and water conservation. Also in the area of Yinshan in the northern part of China, the same results had been observed.
2005 Vol. 3 (4): 1-5 [
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6
WANG Gao-；Yang-Ai-Min-；Zhou-Jie-Hao-；Yan-De-Hua
Studies on effect of soil and water conservation on hydrology and water resources based on Distributed Hydrological Model
Soil and water conservation benefits method and hydrological method are adopted in the previous studies on effect of soil and water conservation on hydrological and water resources. Because of water resources with narrow sense as assessment basis both of them can not systematically bring to light the physical mechanism of effect of soil and water conservation on hydrological cycle, so that the research achievements can not really reveal the effect of soil and water conservation on hydrological and water resources. Distributed hydrological model based on physical mechanism taking narrow and broad sense water resources as assessment basis can overcome their serious shortcomings. The research progress of distributed hydrological model is reviewed. Using the distributed hydrological model based on physical mechanism (WEP-L) , taking the key area of soil erosion control in the Yellow River basin, the area between Hekou and Longmen towns as a case, the effect of soil and water conservation on hydrological and water resources is quantitatively studied. The research results indicated that soil and water conservation enables absolute and relative amount of broad sense water resources increase by 7.26 billion m and 27.1 % respectively, and makes absolute and relative amount of narrow sense water resources to decrease by 0.90 billion m and 14.4% respectively. Soil and water conservation changes the composition of narrow sense water resources, that is amount of surface water resources decreased, amount of unrepeated water resources and water ground water resources increased.
2005 Vol. 3 (4): 6-10 [
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1516
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11
HUANG Zhi-Lin-；Fu-Ba-Jie-；Chen-Li-Ding
Differentiation of soil erosion by different slope, land use pattern and variation of precipitation in loess hilly region
The loess hilly region is characterized topographically by steep slopes and highly dissected terrain, with sharp ridges and deep gullies. Population growth and growing food demand led to increasing pressure on the limited agricultural land, which caused conversion of grassland into agricultural land in the steep-hill slope; there is a growing need to assess conservation effectiveness of agriculture and grassland especially in semiarid loess hilly region. The study has been carried out in the Anjiagou small watershed, Dingxi County, Gansu province. At plot scale, an experiment investigated upon soil erosion of cultivated land and grassland on gentle-hill slope (10-20°) was performed over a period of 1986-1999. The results showed that the magnitude of soil erosion of cultivated land increases with rising of the slope, and there are significant differences among three slope plots; the annual soil erosion amount from plots of grassland varies with slope too, however, there is not a significance difference between plots. A considerable variation in soil erosion among plots indicates that cultivated land differed significantly in response to slope; there is significant difference in runoff and soil sediment between the cultivated land and grassland. Grassland provided good protection against surface runoff (which was consistently less than 2% of rainfall) and soil erosion (less than 27 g·m-2 per year), cultivated land caused twice increase in runoff and 14 times increase in soil erosion. The heavy soil erosion occurred in plots of cultivated land were mainly contributed to a few storm or rainfall events, therefore, there are not direct correlation between yearly runoff, soil erosion and yearly precipitation (total precipitation and runoff-generation rainfall) , whereas, in the plots of grassland, there is a strong correlation between annual runoff, soil erosion with runoff-generation rainfall and yearly precipitation, respectively. The relative contributions to surface runoff and soil erosion among rainfall variable were compared, examined that the precipitation (
P
), maximum 30 minutes rainfall intensity (
I
30
) and
PI
30
are major factors and have positive correlation with runoff and soil erosion of rainfall events. The compound index (
PI
30
) and
I
30
was used o quantify the relation of rainfall versus runoff and erosion, which can be predicted the runoff and erosion yield by the regression equation. The results of the study led us to the following conclusion: all plots of grassland were significantly lower in water and soil loss and more efficient in soil conservation compared with cultivated land, suggesting that reclamation of grassland performed much worse in conserving soil and water resource, overall, the slope did affect soil erosion of cultivated land. Some of their primary tillage in the fall greatly increases the erosion risk on sloping fields. To reduce such risks from fall tillage, some form of residue management should be applied, and tillage should be performed along the slope contours. In particular, the grassland acts as a buffer against fluctuations in runoff and soil erosion associated with rainfall events, agriculture use of cleared land does result in increased erosion, this study has demonstrated the major effects of slope on soil erosion and has found clear evidence that the rate of soil erosion and runoff has increased with slope. Most of these changes have occurred on land which is marginally suitable for cultivation, increasing the risk of soil erosion, accelerated water loss and further land degradation. As a result of the study, it is strongly recommended to protect the grassland, and the cultivated within steep-hill slope be limited to cultivation at a plot scale, considerable protection is offered to both the soil and water resource by grassland.
2005 Vol. 3 (4): 11-18 [
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19
WANG Yun-Qi-；Wang-Yu-Jie-；Shu-Jin-Zhao-；Ji-Shi
Responses of slope runoff generation to rainstorm with different land use types in Jinyun mountain in Chongqing city
To provide basis for vegetation construction of water control and flood regulating in Three Gorges Reservior Area, response of runoff generation amount, runoff duration and runoff generation process to rainstorm was studied based on the slope runoff plots of 5 typical land use types ( mixed forest, broadleaf forest, bamboo forest, shrub forest and framland) in Jinyun mountainous region in Chongqing city, Three Gorges Reservoir Area. The results show that, in the same rainstorm condition, the surface runoff depth of bamboo forest is as 2.7 times as that of mixed forest, as 3.7 times as that of shrubs, as 4.5 times as that of farmland, and as 5.7 times as that of broadleaf forest, and the order of magnitude of underground runoff depth of mixed forest and broadleaf is greater than other land use types, and the depth is 8-10 times as deep as that of other land use types. The longest extended duration of the slope runoff generation is 248 min in the mixed forest, and the shortest is 33 min in farmland. And the longest xtented duration of the underground runoff generation is 59 h in the mixed forest, 50 h in the broadleaf forest, and the shortest is about 11 h in farmland. The peak value of surface runoff is about twice as much as that of mixed forest and shrubs, and is about 3 times as much as that of broadleaf forest and farmland. And the peak value of underground runoff generation is two grade greater than that of bamboo forest, and one greater than that of shrub forest and farmland. Therefore, the mixed forest and broadleaf forest has the greatest function of water control and flood regulation, and the func- tion of the bamboo forest is the worst.
2005 Vol. 3 (4): 19-26 [
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27
GAO Feng-；Mu-Xin-Min
Comparative experiment of soil infiltration of different land use patterns in loess hilly region
The soil moisture infiltration process of forest, grassland and farmland in Yan' er-Gou basin has been compared by means of the double-rings method and the rainfall-simulator method respectively. The results show that double-rings method can reflect infiltration process of water to soil, but the rainfall-simulator method can reflect infiltration of rainwater to soil in natural rainfall. The two methods have obvious differences mainly about the variation course of soil moisture infiltration rate. Adopting double-rings method, the soil moisture infiltration rate mainly depends on the physical properties of the soil, while using the rainfall-simulator method, it depends on not only physical properties of the soil but also the rainfall intensity. Under short-time storm simulated , infiltration rates of forest and barren slope grassland have the same tendency that it is more and more higher with the increase of rainfall intensity. Infiltration rate of farmland, however, has the opposite tendency.
2005 Vol. 3 (4): 27-31 [
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32
LIU Gang-Cai-；Li-Lan-；Zhou-Zhong-Gao-；Zhang-Jian-Hui
Influence and its benefits evaluation of removal lands from cultivation to afforestation and grassland in slope farmland on soil erosion in hilly region of purple soil
It' s important to understand the influence of removal lands from cultivation to afforestation and grassland on soil erosion for farmland use structure adjustment and benefits evaluation of soil and water conservation of those lands. The soil erosion of four types of farmland plot of planting crops (wheat-corn), grasses (ryegrass), fruit trees(loquat), and fruit trees + grasses, were investigated for two years (2003-2004) at Yanting purple soil agriculture experimental station of Chinese Academy of Sciences, and its comprehensive evaluation of soil and water conservation was also made by hierarchy analysis process. The observation results showed that the removal slope farmland used as types of fruit trees and grasses significantly decreased soil erosion by over 30% comparing with crop type, and especially as type of "fruit trees + grasses" by over 60% . Besides, the amount of soil erosion of only planting fruit trees was more than that of planting crops. Therefore, one of key countermeasures of controlling soil erosion is to increase the land coverage. Benefits analysis results showed the rank of its comprehensive benefits is " fruit trees + grasses' type > grasses type > crops type > fruit trees type.
2005 Vol. 3 (4): 32-36 [
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37
HAN Jian-Gang-；Li-Tie-Bin
Response of soil loss to different land use types in small watersheds of purple soil
Soil erosion characteristics of small watersheds not only reflect land use and management condition of watersheds, but also determine the safety of water body environment and water conservancy establishment in the lower reaches of river. Three small watersheds with different catchments area, physical characteristics and land use type were employed to investigate the responding characteristics of soil erosion under different storm types and land use types from 1999 to 2000 in the purple soil area. Results showed that the sediment transport modulus over the woodland-dominated watershed is the least under the erosion of ML-type precipitation and IM-type precipitation. The average modulus is 866 kg·hm
-2
. In contrast, the modulus over the farmland - dominated watershed is the highest with a mean modulus of 5 550 kg·hm
-2
. In addition, the total rainfall erosive factor and the total peak flow amount were proved to be the main influential factors of the variation of the sediment transport modulus for watersheds with various landscape structures and farmland-dominated landscapes, and woodland - dominated watersheds, respectively.
2005 Vol. 3 (4): 37-41 [
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1513
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42
MAI Ke-·Bi-Shi-Te
Importance of biological soil crusts for rehabilitation of degraded arid and semi-arid ecosystems
Biological soil crusts are built up by cyanobacteria, green algae, soil lichens, mosses and fungi. They are important communities in arid and semi-arid ecosystems and influence the ecosystem mosaic and processes. In addition to the influence on the hydrological conditions, the biological crust also stabilises the topsoil, reduces soil erosion, and enhances the nitrogen pools by nitrogen fixation. The crusts are important for the rehabilitation of desertified arid and semi-arid lands and provide a natural protective soil surface cover.
2005 Vol. 3 (4): 42-47 [
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48
CHEN Ai-Ba-；Cun-Yu-Kang-；Wang-Li-Min-；Wang-Ke-Qi-；Liu-Wen-Cheng-；Cao-Zi-Lin
Effect of eco-restoration for soil and water conservation in northwest plateau of Yunnan province in upper reaches of Jinsha river
To investigate the effect of effect of eco-restoration for soil and water conservation in the northwest plateau of Yunnan province in upper reaches of Jinsha river, based on surveying vegetation community structure , analyzing soil chemical and physical properties, and observing runoff and soil loss in plots, effects of eco-restoration are researched. Results show that degraded eco-systems formed by manmade interference can be formed in a manmade ecosystem of perfect function in short time by manmade induction. The obviously vertical structure and positively successive ecosystem already formed in the ecosystem types of shrub, natural secondary forest and artificial mixed forest. The Shannon-Wiener variety indexes of wild grass, shrub, artificial mixed forest and natural secondary forest respectively are 2.29, 2.58, 2.04 and 2.03, and the Pielou homogeneity index JH respectively are 0.80, 0.81, 0.67 and 0.65 . The shrub type is the best eco-system on soil chemical and physical property, whose total soil porosity in 0-30 cm soil layer is 8.7% , 24.7% , 45.9% and 14.3% respectively higher than that of slope farmland, wild grass, natural secondary forest and artificial mixed forest, while the soil organic content is 19.3% , 15.9% , 276.8% and 50.9% higher respectively. The soil property of the natural secondary forest is the worst because of the bad natural environmental conditions. The artificial young forest and natural secondary forest can protect the soil from erosion very well, whose soil erosion amount respectively are 38.0% and 52.3% less than that of slope land and 25.0% and 42.3% less than that of wild grass land.
2005 Vol. 3 (4): 48-53 [
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54
FAN Jian-You-；Ding-Guo-Dong-；Guan-Bo-Yuan-；Wang-Xian-；Li-Su-Yan-；Yang-Ting-Ting
Monitoring Remote Sensing of dynamic change of vegetation coverage in Zhenglan Banner
To reveal the variation law of Otindag sand vegetation, remote sensing quantitative model of vegetation coverage in the Zhenglan Banner under TM is images established based on NDVI and a sub-pixel vegetation coverage model. The dynamic variation of vegetation coverage in Zhenglan Banner in 1987 and 2001 are studied on the basis of above approaches, and the results indicate that the vegetation coverage in Zhenglan Banner mainly has been made up of the medium and high cover degree vegetation which accounted for 94.46 % of the total land area in 1987 and 88.92% in 2001. The area of high cover degree vegetation has decreased by 45.92% heavily while the area of low cover degree vegetation and farmland has remarkably increased from 1987 to 2001. The transformation of vegetation coverage type focuses on vegetation degrading, which is 85.17% of the area that has experienced the transformation of vegetation coverage type. The tendency of vegetation cover transformation in Zhenglan Banner speaks serious deterioration of its ecological environment.
2005 Vol. 3 (4): 54-59 [
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60
YANG Chi-Tian-；Dong-Hui-Yang-；Shan-Shi-Chi-Cheng
On effect of soil hardness on development of seeded and planted seedling root system
Effects of soil hardness on the growth of seeded and planted Pinus densiflora Sieb. et Zucc. seedlings were investigated. Soil hardness was managed for 5 levels (10, 15, 20, 25 and 30 mm of soil hardness index for Yamanaka Type) , and P. densiflora was planted and seeded in each treatment. The root length, the state of root system, stem height, stem basal diameter, biomass of above- and below-ground were investigated . The planted seedling had thinner and shorter roots and the number of roots was more than that of the seeded plant. The main root of the planted plant disappeared in each soil hardness treatment, but the seeded plant remained the main root in every treatment. The ratio of root length to stem height in the seeded plant increased with the soil hardness increasing (2.1, 3.3 and 5.8 when soil hardness was 10 mm, 25 mm and 30 mm, respectively). On the other hand, the ratio of root length to stem height in the planted plant decreased when soil hardness became harder (4.0, 2.5 and 2.4 when soil hardness was 10 mm, 25 mm and 30 mm, respectively) . This means that the root of the seeded plant grow more preferentially than the growth of stem under hard soil conditions. When the plant was planted in the soil harder than 25mm, seedlings could not extend their roots beyond the planting holes and the root system became twisted. These differences between seeded and planted seedlings will effect plant growth, stability of trees, soil conservation ability and the tolerance to the consequence of variation of climate such as dryness. Thus, when we restore forest in degraded lands, soil modifying and the choice of restoring strategy of seeding will be important and necessary to facilitate forest succession and develop balanced forest population.
2005 Vol. 3 (4): 60-64 [
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65
JI Qing-；Li-Chuan-Rong-；Hu-Jing-Wei-；Wang-Gui-Xia
Effects of environment factors on soil respiration rate in coastal protective forests
The effects of environment factors on soil respiration rate in coastal protection forest have been studied . The results indicate that the daily soil respiration rate of the mixed plantation and shrub forest varied with a regular single apex rhythm, and the soil respiration of the latter is higher than that of the former. The surface temperature is the most important influencing factor on soil respiration rate, which has clear prominent positive and the obvious positive correlation with the soil respiration rate of the mixed plantation and shrub forest respectively, the air relative humidity at 1.5m above the surface ground has a negatively prominent influence on the soil respiration rate of the mixed plantation, and so as the influence of the wind speed on the soil respiration of shrub forest. Through the methods of main components analysis and multiple linear regressions, the main environment factors were found and two multiple linear regression models between the soil respiration rate and environment factors were set up.
2005 Vol. 3 (4): 65-69 [
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70
DANG Xiao-Hu-；Liu-Guo-Ban-；Zhang-An-Jun-；Ma-Ru-Ling
Analysis on eco-economic process of small watershed comprehensive management in loess hilly region: A case study on Litaiping small watershed in Longde county of Ningxia
From the point of eco-economic system analysis, the eco-economic system structure and succession process are analyzed to evaluate eco-economic benefits in small watershed management. The land utilization structure as well as suitability, industry structure, consumption structure and the balance between supply and demand for forage were analyzed by comparison in small watershed eco-economic system. And the land utilization structure was optimically simulated by using linear model. The stability of economic system was described with the diversity index of ecological system stability, and the economical benfits was evaluated adopting static and dynamic models. The results showed that the ratio of cropland, woodland and pasture land was changed from 6.2∶2.0∶1.0 in 1990 to 1.9∶1.4∶1.0 in 2003. The proportion of agricultural production decreased from 79.6% to 54.8% , and the proportion of forest and husbandry as well as sideline production increased from 9.6%, 9.6% and 1.1%, to 22.7%, 15.1% and 7.4% respectively. The diversity index of the income tended to increase. The consumption structure tended to rationalization, and the balance between the supply and demand of forage was kept. All indexes in economic evaluation showed that economic benefits was remarkable . All results indicated that the eco-economic structure of the watershed was obviously favorable for progressive succession, which tended to stability with significant eco-economic benefits.
2005 Vol. 3 (4): 70-76 [
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77
CHEN Dong-Li-；Tu-Xin-Xiao
Relationship between adjustment of watershed landscape pattern and benefits of runoff and sediment reduction on loess hilly-gully region
Watershed landscape pattern is regulated by small watershed unit, which is an important approach and method to research the distribution pattern of measures of soil and water conservation and to evaluate benefit of soil erosion control. A case study of Lv' ergou watershed is located the loess hilly-gully region of Gansu province. Digital Elevation Model (DEM) was made using GIS and slope and aspect was superimposed. To test the benefits of runoff and sediment reduction after regulating on watershed landscape pattern, the benefits norm of soil and water conservation measures is used. When the land use shift to preferable pattern, the benefits of runoff and sediment reduction by measures of soil and water conservation taken in the research watershed have increased by 20.36% and 21.55% respectively.
2005 Vol. 3 (4): 77-80 [
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81
XIANG Wu-Sheng-；Li-Xian-Kun-；Lv-Shi-Hong-；Ou-Jie-Lan-；Liu-Shu-Hua-；Qin-Jia-Ke-；Wang-Xiao-Yang-；Xie-Wen-Pei
Differences of environmental factors of different vegetation communities in erosion region of red soil in upper reaches of Lijiang river
In order to provide scientific theoretic basis for vegetation restoration and rehabilitation in the eroded red soil region in the Lijiang basin, the differences of microclimatic environmental factors in the communities of primary vegetation types in the eroded red soil region in the upper reaches of Lijiang basin were compared and studied, and the variations of the main environmental factors in the process of vegetation degradation were also analyzed adopting method of time feature deduced by spatial feature. The results showed that the main microclimatic environmental factors have obvious changes in the process of vegetation degradation because of the degradation of vegetation community structure and species components, which is mainly showed in that. The vertical difference and time variation of light intensity in coniferous and broadleaf mixed forest and evergreen broadleaf forest were smaller than those in grass mass and shrub mass. Light intensity increased with height increasing. In above 150 cm, time variation of light intensity is obvious. The air temperature in coniferous and broadleaf mixed forest and evergreen broadleaf forest had 0-0. 5 ℃ of vertical differences and about 2 ℃ of time variations scale in the monitoring time, and the greater vertical difference and time variation of air temperature occurred in grass mass and shrub mass, and the greatest vertical variation scale was 6 ℃. The vertical variation of relative humidity in coniferous and broadleaf mixed forest and evergreen broadleaf forest was less obvious; whose variation scale was less than 5 % as well as that of soil inner temperature was less than 0.5 ℃. In contrast, those were greater in grass mass and shrub mass, and the greatest variation scale of relative humidity reached 25 % as well as the greatest scale of soil inner temperature reached 8 ℃. In general, the light intensity, the air temperature, the soil temperature and difference of our soil temperature increased continually in the process of vegetation degradation, while the air humidity decreased gradually, and their time and space fluctuant degrees were greater by greater.
2005 Vol. 3 (4): 81-86 [
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87
HONG Wei-Ke-；Zhang-Hui-Chi-；Xu-Fu-Li-；Yuan-Hua-Feng
Analysis on potentiality and benefits of soil moisture conservative irrigation technique in China
To be aimed of the problems of water shortage in agriculture, severe pollution of farmland and decreasing of safe agricultural products as well as that the modern effective water saving technologies are too expensive to extending in a large scale in China, the concept of technological system of soil moisture conservation and irrigation (SMCI) was set up firstly in this study which is a new technological system of water saving formed by combination of soil moisture conservation coverage in the dry farming and water saving irrigation in irrigated agriculture. At the same time, systematic analysis suitability of the saving water, saving fertilizer, ecological and economica benefits of technical system of soil moisture conservation and irrigation. With the extension of technical system of soil moisture conservation and irrigation in half of farmland in China, 19.998 billion m
3
of water may be saved.
2005 Vol. 3 (4): 87-91 [
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92
HU Jian-Zhong-；Zheng-Jia-Li
Floristic characteristics of seed plants in Beichuanhe basin of upper reach of Yellow river
Located in the upper reaches of the Yellow river, the Beichuanhe basin occupies a very important ecological position. There are 74 families, 357 genera and 1006 species of seed plants in the basin. The floris-tic elements are so plentiful, complex and changeable that there are 12 areal types and subtypes of genus of seed plants in the basin, accounting for 80 % and 45.2 % respectively, compared with that in the whole China. The number and ratio of genus of Temperate have the dominant weights of all the types, and the floris-tic elements of North Temperate, which has 117 genera, accounts for 32.8% of the total genus in the basin and 54.9% in the whole country. The basic characteristics in the basin should be determined by North Temperate . The regionalization of flora in the basin should be classified as Tangut region, Qinghai-Tibet subking-dom, Holarctic kingdom. The study of floristic element has supplied sufficient basis for developing, utilizing and preventing the local plant resources, as well as developing plant introduction from other basin or areas.
2005 Vol. 3 (4): 92-101 [
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102
DIAO Xiao-Yang-；Lin-Ji-Zhou
Growth characteristics and its vegetation restoration significant of clonal of three Caragana species
The native leguminous species,
C. licentiana
,
C. opulens
and
C. intermedia
, can produce many ramets by rhizome. They exhibited sympodia branching pattern and "guerilla" architecture and have strong ability to spread at horizontally. The persistent rhizomes formed closely crowed below ground networks for this native species. No ramets induced from root in
C. intermedia
. Authors suggested that vegetative expansion is a regeneration strategy for C. licentiana when seed germination and seedling establishment restricted by relative drought and animal predation. Compared with that in the north-facing sloping hill, the ramet population in the south-facing sloping hill of C. licentiana exhibited significantly more ramets and longer rhizome intemode and greater biomass allocation to rhizome but similar ramet height, which show morphological plasticity for
C. licentiana
.
2005 Vol. 3 (4): 102-107 [
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108
CHEN Li-Xin
Soil acidity change of Larch plantations and relation between change and inorganic phosphorus types
In order to manage larch plantations scientifically, improve its soil quality continually and raise stand productivity, soil acidity change of larch plantations at different development stages and their relationship between active acidity (pH value), exchange acidity, hydrolytic acidity and various types of inorganic phosphorus were studied in mountainous area of eastern part of northeastern China. The results showed that, with stand age increasing, active acidity (pH value) in rhizosphere soil decreased continually, but exchange acidity, exchangeable aluminium increased obviously, their correlation coefficient between Ca-P, O-P, and total hydrolytic acidity in rhizosphere soil, respectively, decreased, that between Fe-P, exchange acidity, and exchangeable aluminium respectively increased. The change of active acidity and total hydrolytic acidity in rhizosphere soil greatly influenced Al-P, especially in young stand, near mature stand and mature stand stages, their correlation between active acidity,total hydrolytic acidity, and Al-P respectively, reached significant level or highly significant level. Ca-P change in rhizosphere soil was mainly influenced by active acidity in rhizosphere soil;There was strong correlation between Fe-P and total hydrolytic acidity in rhizosphere soil during various age stages. O-P in rhizosphere soil decreased when exchange acidity and total hydrolytic acidity increased. There was not significant correlation between soil acidity and various forms of inorganic phosphorus in non-rhizosphere soil, respectively.
2005 Vol. 3 (4): 108-114 [
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115
YUAN Zheng-Ke-；Yuan-Sui-Bei-；Tao-Min-；Tian-Yo-Xin-；Liu-Wen-Duan
Law of soil loss at agro-forest ecosystem of
Castanea mollissima
By means of a fixed observation station of runoff plot, soil loss amount at 7 different agro-forest ecosystems were recorded and analyzed successively for 8 years, in order to find out the space-time variation law of soil erosion at different agro-forest ecosystem of
Castanea mollissima
in low hilly region of red soil. The results showed that soil loss amount slowly reduction, sharply reduction and become stable occurred at the following 3 stages respectively, young intercropped
Castanea mollissima
forest, crown fast-growing stage without intercrop, and stand closed stage. The soil loss ranged from 2.25 t/hm
2
to 3.31 t/hm
2
, but from 32.91% to 45% less than that at CK in the current year of intercropped. When the stand became closed (at the third stage), the soil loss was less than 0.05 t/hm
2
. There were much differences of soil loss among the 10 to 70 mm rainfalls daily. Intercropped plant covering surface land is important for erosion control among the 10 to 70mm rainfall daily.
2005 Vol. 3 (4): 115-118 [
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119
FANG Dai-Wei-；Shu-Dong-Wei-；Yang-Fu-Quan
Effects of closing measures on community structure of soil and water conservation forest of
Protruding Eucalyptus
In order to open out effects of closing measures on community structure of
Protruding Eucalyptus
forest, some factors of three plots of soil and water conservation forest community of
Protruding Eucalyptus
under different closing and protective term were investigated, contrasted and analyzed, which include vegetable species, biomass, soil fertility, edaphon and existing amount of withering matter, and those plots located in Xiaoliang soil and water conservation station of Maoming city, Guangdong province. The results showed that with closing measures, existing amount of withering matter under forest and soil fertility increased rapidly, condition of soil moisture and fertility were improved, and development of community structure was accelerated. Existing amount of withering matter of
Protruding Eucalyptus
forest closed 20 years was 1 103.4 g/m
2
, soil organic matter content was 1.871 25% , which was 4.69 times and 4.15 times higher than that of not being closed, and which was 1.04 times and 1.01 times higher than that of being closed 10 years. The
Protruding Eucalyptus
forest closed 20 years had obvious three vertical structures of timber forest, shrub and grass. Timber forest had sub-layer besides
Protruding Eucalyptus
. That closed 10 years had clear shrub and grass layer too. However, The
Protruding Eucalyptus
forest which was not being protected had only single timber layer. The biomass of
Protruding Eucalyptus
forest being closed 20 years was 347.841 kg/m
2
,which was 1.17 times higher than that of being closed 10 years, and 1.53 times higher than that of no being closed.
2005 Vol. 3 (4): 119-123 [
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