| The rapid growth of the population leads to increasing of the intensity of development and utilization of land resources, especially in Southwest. The traditional extensive agricultural production led to irrational use of land and soil erosion, and agro-ecosystem is very fragile. Therefore, it is the strategic choice of modern agriculture and rural economic development that changing agricultural production reasonably, developing ecological agriculture which forms of agro-forestry complex, agriculture-forest-animal husbandry complex and so on, and searching methods to integrate economic and ecological effectively. In this paper, the micro-ecological environment characteristics and photosynthesis of citrus in Jiangjin were studied by using field experiment. Besides, the economic and ecological benefits of citrus-crops complex ecosystems were described. The main results are as follows:1,The micro-ecological environment characteristics of citrus-crops intercropping ecosystems.Compared with CO (Monoculutral Citrus ecosystem), the micro-environment was improved in Citrus-crops intercropping ecosystems. The CS (Citrus-soybean intercropping ecosystem) showed the significant cooling effect which temperature and leaf temperature were all lowest in six systems. The temperature was highest in CCh (Citrus-Chinese cabbage intercropping ecosystem), while the leaf temperature was highest in CT (Citrus-trifolium repens intercropping ecosystem). The air relative humidity in all systems performed a "U-curve". The observations of CS in each observation time were higher than that of C0, but which were simlar to C0 in other ecosystems. The CO2 concentration of CT, CI (Citrus-ipomoea batata intercropping ecosystem), CCh and C0 all showed a moderate "U-curve", and the values were closed to each other, fluctuation did not exceed 2%. But the environmental CO2 concentrations of CS and CC (Citrus-cucumber intercropping ecosystem) proformed a "V-curve", and the values at 12:00 were 8.33% and 3.88% lower than that of C0. Intercropping could reduce soil bulk density, improved soil porosity and moisture content, thereby improved the soil physical properties. Citrus interplanted with trifolium repens, ipomoea batata and Chinese cabbage could reduce soil bulk dencisy for 3.72%-9.84% and add porosity for 3.15%-8.28% combind with C0. Water content of all intercropping ecosystems was higher than C0, especially in CT and CI. Intercropping could improve the function on drought resisting in summer, the soil moisture content present a increasing trend in August. Intercropping increased soil organic content, while the difference was not significant. The available nutrients reduced with the soil depth's increasing. The availability N was higher in 0-45cm in complex ecosystems, especially in CS. In 0-15cm, the availability P of CCh is highest, but in 15-60cm, the availability P of CT is highest, and the availability P of CI and CC in all layers was lower than that of C0. The availability K of all ecosystems was lower than C0. Potash fertilizer was needed becouse of the competing between crops. Intercropping increased the soil microorganism quantity and improved the enzyme activity, especially in CCh.2. Impacts from citrus-crops intercropping ecosystems to photosynthetic property of citrus.The diurnal variation of citrus leaves'net photosynthetic rate (Pn) was unsymmetric twin-peaked curve in CS, while single-peaked curves in the others; daily averaged Pn in CT, CS and CI were all higher than that inC0, and the differences were significant (p<0.05), while those inCC and CCh were lower, with a weaker capacity of assimilating CO2. Transpiration rates (Tr) in all treatments were twin-peaked curves except CC; daily averaged Tr represented the following result:CC> CCh> CS> C0> CI> CT. Stomatal conductances (Gs) in C0, CT and CS were slight twin-peaked curves, while single-peaked curves in CI, CC and CCh; the differences were not significant with intercropping crops having less impacts on citrus leaves' Gs. In every system, diurnal variation of photosynthetic active radiation(PAR) had a single-peaked variation trend. The values in each time of intercropping ecosystems are higher than in C0 except the oppositing result in CC. Light utilization efficiency (LUE) showed an single-peaked curves in all treatments, while diurnal variation of water utilizing efficiency (WUE) emerged as three types: single-peaked trend in C0, CT, CI and CCh; twin-peaked trend in CS; highest in early moring and decreasing in the daytime in CC. Daily averaged of LUE and WUE in CT, CS and CI are higher than that in C0, but in CC and CCh, both of them were lower. Correlations between Pr and environmental factors might be changed after intercropping other crops, but the impact on interactions between environmental factors was not significant. Principal component analysis and Cluster analysis displayed that, citrus's photosynthetic property was best in CS, better in CT and CI and general in CC and CCh.3. Ecological and economic benefits of differents citrus-crops intercropping ecosystems.Intercropping improved quality of citrus except CC, whose sugar content was so low. The citrus yield in CS which was 20kg/667m2 more than C0, while 1.06%-22.98% less in other treatments which fortunately the income could increase by the output of companioncrops. Intercopping had better ecological benefits that the micro-ecological environment and the soil fertility and the level of carbon fixation and oxygen produdion were improved and the soil erosion of hills was reduced.Cucumber was not unfit for intercropping with citrus becase it might affect the growing of citrus and reduce the quality of fruits by frequent tillage and shading. As a result of high investment at once and low profit, Chinese cabbage was better in small plots than largely plantation. Trifolium repens and ipomoea batata was more suitable for hillside lands or using in complex systems with animal husbandry. Soybean was the best variety because of its higher ecological and economic benefits when intercropping with citrus. |
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