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Agroforestry systems promote ecological,social and economic benefits in comparison with traditional forestry systems.Agroforestry systems provide various products for household including but not limited to,food and medicinal products for humans and animals,timber for construction,fuelwood for domestic use and income for the household.They also contribute to environmental sustainability and can act as a buffer to climate extremes.In order to study the physioecological characteristics of soybeans and salvia grown in agroforestry systems,the photosynthetic characteristics and parameters of chlorophyll fluorescence were examined.The study sites were located in Shanghe village(latitude 33°50′19″N,longitude 109°53′38″E,elevation 451m a.s.l.),Shangluo,Shaanxi Province.The total extent of the study site is 8 hectares.In this study,soybeans(Glycine max L.Merr.) Qindou 8,and medical plant salvia(Radin salviae Miltiorrhizae) were selected as agricultural crops.Within the study site,best areas were selected to implement the two treatment combinations,walnut-soybeans and walnut-salvia,replicated 3 times.In addition,areas without walnut trees were also selected for control measurements.The walnut trees were planted in 2004 at a within row spacing of 3m and between row spacing of 5m.The tree rows were oriented north-south.Twelve sample locations around each tree were assigned in the following manner: 1) perpendicular to the tree trunk at 1m and 2.5 m east and west(4 locations),2) and at the same distances(1m and 2.5m east and west) from the tree row at 1 m north(4 locations) and 1 m south(4 locations) of the tree trunk.At each time of sampling,a single leaf from the upper crop canopy was selected at the above indicated locations.The results indicated that photosynthetic active radiation(PAR) was reduced significantly from full daylight at 1m from the walnut tree rows.The diurnal variations of photosynthetic rate(Pn),stomata conductance(Gs) and transpiration rate(Tr) of soybean were also lower close to the tree rows.The diurnal variations of photosynthetic rate in salvia at different distances from the tree row were different,and there was a "lunch break" phenomenon observed.The photosynthetic parameters for both crops were lower in the agroforestry system compared to the rates measured in the control treatment.The total chlorophyll and apparent quantum yield(Ф) for both crops increased,whereas the light compensation point(LCP) and light saturation point(LSP) decreased with increasing degree of shade.Meanwhile,the Fv / Fm,ФPSⅡ and qP were significantly higher than those quantified in the control treatment for both crops,But,qNP decreased with increasing degree of shade,indicating that soybean and salvia have strong adaptability to low irradiance.The research area is located in the ShangLuo Mountain area,and the regional economic development is very slow,and land natural resources is also in short supply.Therefore,based on the results from this study,it appears that agroforestry systems can potentially restore these disturbed lands and contribute to the development of the economy in the hilly region in Shangluo. |
