J.Y. Zhuang

Spatial Variability of Soil Erodibility (K Factor) at a Catchment Scale in Nanjing, China

We conducted a study to examine the spatial variability and vertical characteristics of soil erodibility (the K factor) and its relationship to vegetation types, based on a case of study on Dengxia catchment, Jiangsu Province, China. Using traditional statistical and geostatistical methods, the K factor was calculated by the EPIC model. The results showed the following: (1) the K value on the studied area was highly spatially variable, with a range from 0.15 to 0.50, a mean of 0.13, and a coefficient of variance of 22.11%; (2) the overall spatial distribution of the K values presented a clear belt shape and was higher in the northwest than in the southeast, with several high K-value centers clustered in the central and southern parts of the region. The results showed that the K factor of the areas covered by forest, mainly in the northern part, was greater than that of farmland and human residential areas in the central and southern part of the region. (3) The vertical (soil depth) variability of the K value by vegetation type followed the order K(0–20 cm) tea garden land > farmland > grassland > broadleaf forestland > bamboo shrub land > coniferous forestland > bamboo forestland.

Ecological and Environmental Characteristics in the Hilly Region of Middle and Lower Yangtze River

The Yangtze River is one of the most important rivers in the world. Its middle and lower reaches lie in the subtropical monsoon area of east Asia, which has a warm and moist climate with clear distinction between the four seasons. The vegetation in the middle and lower reaches of Yangtze River takes on conspicuous vertical zoning characteristics. From low to high elevation, the vegetation makes a transition from evergreen broadleaf forest to mixed evergreen broadleaf and deciduous forest. The species diversity of forest plantations in the middle and lower reaches of the Yangtze River has very important status in China. The present problems of soil erosion are based mainly on the following factors: (1) plentiful precipitation provides strong force for water erosion; (2) the inhomogeneities in the temporal and spatial distributions of precipitation result in both frequent flood and drought calamities; (3) simple forest structure and monocultures of trees cause fragility of the forest ecosystem; (4) the sharp increase of population has made the forest destruction more serious and has caused flooding. Because water and soil loss has constrained the development of eastern China, the control of soil loss has been deemed as of primary importance in reforestation.

Calculation of Water and Sediment Discharge Using an Integral Calculus Method

In order to improve the accuracy of the calculation of the amount of water discharge, a new integration equation method was developed and applied. In this study, field observation of runoff with a weir was carried out at the outlet of the Shangshe catchments and sub-catchments of four types of land use within the catchment in Yuexi prefecture, Anhui Province. Each weir was equipped with a float-type, water level recorder. In this research, the water level hydrograph of each rainfall–runoff event was divided into periods at 10-min intervals. In each period, a water level versus time linear function was established. Then, the water level versus flux relationship was transferred into a function between flux and time in each period, which could be integrated over time. Thus a new integral equation method was developed to calculate the amount of water discharge in sub-catchments and catchments. The result showed that the new integral equation method can improve the accuracy of annual water and sediment discharge by 8.7–17.1% at five monitoring sites using the field observation data in the year 2000. Compared to the instant flux coefficient method, it improves accuracy greatly and is suitable for the calculation of the amount of water and sediment discharge at weirs under various conditions of water level variation.

Application of a GIS-Based Revised FER-USLE Model in the Shangshe Catchment

To support policy decisions, the greatest need is for models that can produce robust results using readily available data. The ER-USLE model was tested at the sub-catchment scale in a sub-catchment of cultivated land by comparing observed specific sediment discharge (SSD) at the outlet of sub-catchment with predicted SSD using ER-USLE model. The FUSLE model was tested from the USLE plot to the sub-catchment scale in sub-catchments of pine forest, Chinese fir forest, and tea garden by comparing observed SSD with predicted SSD using FUSLE model. Integrating the ER-USLE model for soil loss prediction in cultivated land and the FUSLE model for soil loss prediction in forest, the FER-USLE model was developed for soil loss prediction in both cultivated land and forest. The FER-USLE model was tested in the Shangshe catchment by comparing its predictions with observed SSD at the river outlet, showing robust results. Results show that it is useful for prediction of annual soil loss for various types of land use in the Dabie Mountains, China. FER-USLE model is available to many users and policy makers in the Dabie Mountains, China.

Model of Forest Hydrology Based on Wavelet Analysis

This investigation proposes a new approach for establishing the relationship between rainfall and runoff, as a function of forest coverage by wavelet-based analysis. First, the Db4 discrete wavelet transform is used to decompose the rainfall and runoff time series to obtain wavelet coefficients at multi-resolution level. The results show that trends of rainfall and runoff were similar. However, runoff did not always follow the trend of rainfall, as it was also influenced by other factors. Second, these wavelet coefficients are applied to model. The results show that potential impacts of forest coverage on hydrological response are of significant importance in Lao Shi-Kan watershed. Runoff decreases as vegetation coverage increases.

A Study on Plant Roots and Soil Anti-scourability in the Shangshe Catchment, Dabie Mountains of Anhui Province, China

The distribution of root biomass was studied in different layers (0–10, 10–20, 20–30, and 30–40 cm) of soil depth with the plot method in different types of plants in the Shangshe catchments in the Dabie Mountains of Anhui Province. Samples of root system were taken to the lab to measure their quantity and length. In each plot, soil anti-scourability in corresponding soil layer was measured with a C.C. Suoboliev anti-scourability instrument. The results showed the following. (1) The root system was mainly distributed in the 0–40-cm layer of soil, and the root quantity was the greatest in the surface layer of soil. The fine roots smaller than 1 mm in diameter were absolutely predominant in root length. (2) In the same section, the values of the anti-scourability index of surface layer were larger than those of other layers in different types of plants. The tree root system, especially the fine roots less than 1 mm in diameter, had powerful function on soil loss control. The correlated coefficients between the length, the quantity, and the density of fine roots and the anti-scourability index were 0.817, 0.716, and 0.643, respectively. The mean length of fine roots was a key factor to soil anti-scourability index. The anti-scourability index was closely correlated with non-capillary porosity of each different type of soil, indicating that forest had a soil stability function because their root system improved soil physical properties and finally created a biosoil system with anti-scourability.

Development of the GOIUG Model with a Focus on the Influence of Land Use in the Shangshe Catchment

Sediment management strategies are crucial to developing countries because of the limited resources. Establishment of these strategies is hampered to some extent by the lack of reliable information on catchment sources. This chapter reports the rainfall-sediment response of various types of lands in the Shangshe catchment (528.8 ha) of the Dabie Mountains of Anhui Province, China. Field observation in the year 2000 showed 32 events occurred, among which 18 events produced runoff. Comparison among SISSD (specific instant suspended sediment discharge) hydrographs from the five monitored sites showed that the cultivated land produced the highest level of SISSD, which was 100 times higher than that of the tea garden, Chinese fir forest, or the pine forest, and 10 times higher than that of the river outlet. Integrating the field observation data of SISSD in representative kinds of land use within the catchments with geographic information system (GIS) and a hydro model, the GOIUH (GIS-based observed instantaneous unit hydrograph) model, was constructed to simulate the SISSD hydrograph of the river outlet. The resulting model showed that the calculated SISSD hydrographs compared well with the observed ones at the outlet of the Shangshe catchment, as shown by a coefficient of correlation R 2 of 0.8. The semi-distributed sediment discharge model, with a focus on the influence of land use in the Shangshe catchment, can help to quantitatively understand the source of sediment discharge.

Effect of Afforestation on Soil and Water Conservation

Reforestation of bare land has a good effect upon our environment. It has usually been assumed that reforestation can control erosion. However, in the early years of reforestation, things were complicated. Experiments showed that after the tending of young trees, runoff clearly increased until 2–3 storm events had occurred. Soil loss increased within 1 month after staddle tending and it was especially large during storm events. It was estimated that if there are 250–1500 fish scale pits per hectare for tree planting on sloping land, then 362.5–725 m3 hm–2 year–1 sediments could be conserved in place. The amounts of nutrient elements in the surface runoff were highest in the bare land; the amounts were second highest in Chinese fir (Cunninghamia lanceolata) forest, and those in the level terrace areas were the lowest, indicating that changes in the topography and improvements in vegetation coverage had an important effect on nutrient loss. Second, reforestation can improve biodiversity. The understory plant, physical, chemical, and microbial properties were investigated for several types of forests over 10 years of reforestation at Yiyang County and Taihe County. Before reforestation, there were only shade-intolerant herb species. After reforestation, some shade-loving plants that like a wet, shady environment were found growing well. Third, reforestation has a good effect on micrometeorology. After reforestation the maximum temperature inside the forest in summer was 2.3°C lower than that outside the forest, and the relative humidity increased by 9%. The daily variation amplitude of temperature inside the forest was 2.8°C lower than that outside the forest; the amplitude of variation of humidity increased by 5.5%.

Development and Test of GIS-Based FUSLE Model in Sub-catchments of Chinese Fir Forest and Pine Forest in the Dabie Mountains, China

Land use plays an important role in soil loss and other environmental problems. Correct prediction of soil loss from different types of land use is very important to land use policy making in the Dabie Mountains, China. Field observations of water and soil loss were carried out in the Shangshe catchment on land in four types of use from 1999 to 2007. This chapter reports the study of soil loss in the sub-catchment of Chinese fir forest and the sub-catchment of pine forest. Field observations of water and soil loss were carried out at the micro-plot scale, the USLE (universal soil loss equation)-plot scale, and the sub-catchment scale in the sub-catchment of Chinese fir forest, as well as of pine forest. Analysis of these field observation data shows that litter in forest has an important hydrological function. In the Chinese fir forest and pine forest, the micro-plots without litter and grass produced more than 71 times the soil loss of micro-plots with litter and grass at the same gradient in 2000. By integrating a linear regression method with GIS and USLE, a so-called FUSLE (USLE in forest with a focus on litter) model was developed to predict soil loss in forest. The rain erosivity factor is turned into a modified rain erosivity factor when litter is added as a new factor. These measures are believed more practical for soil loss prediction in forest areas because the litter factor is a key factor in soil loss on forestland. Furthermore, the meter-scale plot method is able to get enough field observation data in a few years for soil loss prediction and it is less expensive.

Social and Economic Benefits of Forest Reconstruction

In this chapter, the social and economic benefits brought about by forestry–agriculture composite management, wasteland afforestation, and management of forest sites with good methods are introduced. Planting economic crops, green manure, and green fodder in orange orchards not only improve the growth conditions for oranges but also improves land utilization ratios, increases the output value per unit area, and generates satisfying economic benefits. In particular, the virtuous cycle model integrated planting and breeding by planting grain amaranth (Amaranthus hypochondriacus), an excellent fodder rich in protein, in the vacant spaces of the orange orchard, feeding livestock and poultry with its stems and leaves, and then collecting animal manure in a biogas digester. The yield of grain amaranth interplanting in orchards was as high as 45 t ha–1, which could be used to feed pigs and poultry, replacing one-third of the concentrated feed and increasing the quality and smell of meat greatly. The biogas produced by biogas digester with raw materials of grain amaranth straw and manure of livestock and poultry could provide domestic energy and illumination for 20 people of four families living on the orchard farm, reducing environmental pollution and saving huge costs of electricity and fuel. With the increasing income, local residents’ awareness of forest reconstruction and environment protection was aroused, and poverty was eliminated.