Ecological Benefits of Compound Ridge Culture in Hillside Orchard in the Three Gorge Reservoir Area

Based on contour tillage of wide ridge and furrow covering and agro-forestry, this paper sets up a compound ridge culture mode in hillside orchards and introduces a long-term observation to the mode＇s effects on ecological benefits of water and soil conservation. A five-year study shows that compound ridge culture in hillside orchards is effective in water and soil conservation, especially in reducing soil erosion. Compared with the traditional management modes of orchards, compound ridge culture has reduced runoff amount by 41.96%-57.96%, soil erosion amount by 55.47%-67.75%. Compound ridge culture also brings an obvious reduction of soil nutrient loss and of non-point source pollution, which is of great importance for keeping and increasing the productivity of hillside orchards in the Three Gorge Reservoir Area.

Exploiting pattern and sustainable development of marginal lands in the Three Gorge Reservoir Areas

This paper studied the distribution and utilization status, reasonable exploitation patterns and potential productivity, and sustainable development of marginal lands in the Three Gorge Reservoir Areas. It has been pointed that problems of the soil fertility degradation, poor productivity in crop lands, natural disasters and environmental deterioration existed in all the exploited marginal lands. In order to maintain the sustainability of the marginal lands, following measure have been proposed: prohibiting cultivation in the crop lands with a slope more than 25°, restoring vegetation in the slope more than 25°, strengthening the basic agricultural construction, establishing the production base of woody feeds and oils, establishing a multi dimensional management model with reasonable structure and optimum function for forestry, agriculture and fishing.

AN ANALYSIS ON THE STRUCTURE TYPES AND BENEFITS OFSLOPELAND AGROFORESTRY SYSTEMS-Taking the Three Gorge Reservoir Area As An Example

The modem term 'agroforestry system' is derived from agricultural practices. It is an organic combination of agriculture and forestry, ecology and economy, product variation and scientific management. On the basis of analyzing the types and structure of agroforestry system in the Three Gorges Reservoir area,the paper poins out that agroforestry system can be divided into diffend structutal levds. Taking some typical cases as examples, it compares the benefits of four kinds of structures. The result illustrates that the hedge row agroforestry system on slopeland is an effective way to realize coordinate development of ecology and economy.

Compound Planting of Bletilla striata under Forest in the Three Gorges Dam Area

[Objectives] The aim was to study the artificial cultivation of Bletilla striata to realize large scale and standardization planting. [Methods] The comparison tests were conducted on B. striata with different canopy densities of the Magnolia officinalis forests,different compound planting densities and different tending measures and management. [Results] When the stand canopy density was 0. 4-0. 6,the per unit yield of B. striata was 5. 4%,6. 8% higher than that at the canopy density of less than 0. 4 and more than 0. 6,respectively. When the planting density was 30 cm × 30 cm,the per unit yield increased by 16. 1%,12. 0%,13. 1% respectively compared with the planting density of 20 cm × 20 cm,25 cm × 25 cm,35 cm × 35 cm. When B. striata was planted from October to November,the per unit yield was 5. 6% higher than that planted from December to January of the following year,and 21. 3% higher than that from February to March of the second year. When farmyard manure was applied during the cultivation,the per unit yield was 31. 7% and 18. 4% higher than the application of chemical fertilizer and compound fertilizer. When weeding 4 times per year,the per unit yield increased by 240. 1%,137. 0% and 43. 9% respectively from that weeding 1 times,2 times,3 times per year. [Conclusions]When planting B. striata,the stand canopy density of 0. 4-0. 6 could make it receive absolutely shelters and the lighting conditions required for the growth,thereby bringing in high emergence rate,good growth potential and high yield. The best planting effect of B. striata could achieve by planting from October to November with the planting density of 30 cm × 30 cm,which can play the maximum benefit of individual plants. Moreover,weeding 4 times per year combined with the use of farmyard manure can promote the development and growth of tubers,which can greatly improve the yield of B. striata.

3-D NUMERICAL SIMULATION OF TURBULENT FLOW AFFECTED BY THREE GORGE PROJECT UNDER CONSTRUCTION

Because of the construction o f the Three Gorge Project (TGP), the local turbulent flow, compared to the original, h as been changed greatly. In order to analyze the variation of hydrodynamic feat ure in detail, a 3-D mathematical model was established to simulate the turbule nt flow in the corresponding area. The results of computation indicate that grea t changes of flow took placed in the area close to the cofferdam, but the area i s not large. The results are in agreement with that of the obtained.

Nutrient cycling characteristics of Quercus acutisima and Pinus massoniana mixed forest in the Three Gorge Reservoir area, China

The cycling characteristics of nitrogen(N), phosphorus(P) and potassium(K) of the Quercus acutissima and Pinus massoniana mixed forest which is the most common forest type in the Three Gorge Reservoir areas in China, were systematically analyzed. The results showed that N, P and K accumulated in the plant pool and in the litter pool, while total N, P, and K were deficient in the soil pool and in the forest systems. Contents of N in the soil of depth 20—40 cm were the key factor limiting growth of trees. The biological outside cycling coefficients were 878, 725 and 117 times of inside cycling coefficients of N, P and K, respectively. 3392, 1026 and 1588 kg of N, P and K return to the litter pool from branches, leaves and throughfall per year, but, 1431, 132 and 1048 kg of N, P and K return to the soil from litter pool per year respectively. It is clear that 58% of N, 87% of P, and 34% of K are lost by surface runoff per year. 549%, 130%, and 834% of N, P and K withdraw from leaves to branches, 499%, 199% and 730% of N, P and K withdraw from branches to trunks per year, respectively.

Energy of forest systems in the Three Gorge Reservoir area

The energies of three forest ecosystems in the Three Gorge Reservoir area were analyzed. The results showed that the existing energies were 151 2438, 139 2014 and 175 1659 (×10 10 J/hm 2), the annual net fixed energies were 38 8924, 31 2214 and 46 8231 (×10 10 J/hm 2), and the utilization efficiency of light energies were 1 16, 0 99 and 1 40 for the Quercus acutissima forest(Q.A.), the Pinus massoniana forest (P.M.), and the Queresus acutissima and Pinus massoniana mixed forest (Q.P.), respectively. In the Three Gorge Reservoir Area, the energy efficiency of Quercus acutissima and Pinus massoniana mixed forest is the best.