The main mechanism and types of the formation and succession and spatial distribution pattern of agricultural ecosystem are discussed in this paper. It suggests that the formation and succession of agricultural ecosys...The main mechanism and types of the formation and succession and spatial distribution pattern of agricultural ecosystem are discussed in this paper. It suggests that the formation and succession of agricultural ecosystem is co-influenced by the natural environmental conditions, natural resources, economic development level, market background, science and technology, policy systems,and social and cultural customs. But in different areas, the formation mechanism of the agroecosystem is also different. There are some main types such as the closed environment-induced, cultures and customs-induced, economy and technique-induced, resource-restricted, policy-induced types. Because of the interaction of above induced factors, agroecosystems often have following spatial distribution pattern, including gradient distribution, random inlaid distribution, island-like distribution and line or strip distribution.展开更多
A mini-plot field experiment was conducted on a loamy clay Oxisol to compare and evaluate P absorption and transfer in plant organs and P movement in soil profile at three P application depths under the soybean-citrus...A mini-plot field experiment was conducted on a loamy clay Oxisol to compare and evaluate P absorption and transfer in plant organs and P movement in soil profile at three P application depths under the soybean-citrus intercropping versus the monoculture using a ^32p tracer technique. Total P absorption （Pt） by soybean and P accumulation （Pa） in soybean organs decreased significantly （P 〈 0.05） under the intercropping in contrast to the monoculture. With intercropping, when ^32p was applied in topsoil （15 cm soil layer）, total ^32p absorption （^32pt） in soybeans was significantly lower （P 〈 0.05）, but when ^32p was applied to deeper soil layers （35 or 55 cm soil layer）, ^32pt in soybeans was significantly greater （P 〈 0.05）. The percentage of P in leaves to total P （Pa/Pt） and 32p in leaves to total ^32p （^32pa/^32pt） for soybean were ≥ 25% and those of root ≥ 12%. When P was applied ia topsoil and 55 cm soil layer, no significant differences were found between intercropping and monoculture for Pt of citrus. The P absorbed by citrus was transferred rapidly to the growing organs of aboveground during the experiment, and the speed of transferring to the growing organs slowed when P was applied to the deeper soil layers. In intercropping, P mobility was heightened in the soil profile, and P in deeper soil layers moved up to topsoil more rapidly.展开更多
文摘The main mechanism and types of the formation and succession and spatial distribution pattern of agricultural ecosystem are discussed in this paper. It suggests that the formation and succession of agricultural ecosystem is co-influenced by the natural environmental conditions, natural resources, economic development level, market background, science and technology, policy systems,and social and cultural customs. But in different areas, the formation mechanism of the agroecosystem is also different. There are some main types such as the closed environment-induced, cultures and customs-induced, economy and technique-induced, resource-restricted, policy-induced types. Because of the interaction of above induced factors, agroecosystems often have following spatial distribution pattern, including gradient distribution, random inlaid distribution, island-like distribution and line or strip distribution.
基金Project supported by the Knowledge Innovation Programme of the Chinese Academy of Sciences (No. KZCX2-407).
文摘A mini-plot field experiment was conducted on a loamy clay Oxisol to compare and evaluate P absorption and transfer in plant organs and P movement in soil profile at three P application depths under the soybean-citrus intercropping versus the monoculture using a ^32p tracer technique. Total P absorption （Pt） by soybean and P accumulation （Pa） in soybean organs decreased significantly （P 〈 0.05） under the intercropping in contrast to the monoculture. With intercropping, when ^32p was applied in topsoil （15 cm soil layer）, total ^32p absorption （^32pt） in soybeans was significantly lower （P 〈 0.05）, but when ^32p was applied to deeper soil layers （35 or 55 cm soil layer）, ^32pt in soybeans was significantly greater （P 〈 0.05）. The percentage of P in leaves to total P （Pa/Pt） and 32p in leaves to total ^32p （^32pa/^32pt） for soybean were ≥ 25% and those of root ≥ 12%. When P was applied ia topsoil and 55 cm soil layer, no significant differences were found between intercropping and monoculture for Pt of citrus. The P absorbed by citrus was transferred rapidly to the growing organs of aboveground during the experiment, and the speed of transferring to the growing organs slowed when P was applied to the deeper soil layers. In intercropping, P mobility was heightened in the soil profile, and P in deeper soil layers moved up to topsoil more rapidly.
