青藏高原小麦高产原因的农田生态环境因素探讨

青藏高原小麦高产原因的传统解释认为：高原地区太阳辐射强、温差大、光温配合好，小麦光合作用强度高，呼吸消耗小，有利于更多地积累同化产物。而研究表明：在高产条件下，高原小麦日平均干物质累积速率略低于平原地区。传统观点不能对此作出很好解释。事实上，青藏高原ＣＯ２密度低会严重制约小麦的光合作用；但高原太阳辐射强、群体结构有利，这在一定程度上补偿了ＣＯ２的不足，使得其日平均干物质累积速率仅略低于平原地区。高原年均温低导致小麦的生育期远长于平原地区，因此，单季小麦能够更长时间地利用各种生态条件。略低的干物质累积速率和长得多的生长期决定了青藏高原的干物质单产高于平原地区；收获指数高的小麦在高原获得了创记录的高产。

ANALYSIS OF AGRO ECOLOGICAL ENVIRONMENTALFACTORS ON THE CAUSES FOR HIGH YIELD WHEAT IN QINGHAI XIZANG PLATEAU

Qinghai Xizang Plateau is a high yield wheat area, and the highest yield of wheat can reach 15 2t/ha. Reasons accountable for high yield according to traditional concept are: (a)plentiful solar radiation; (b)great temperature range; (c)high intensity of photosynthesis of wheat; and (d)low consumption rate of respiration, which are thoughyt to be favorable for more accumulation of assimilation pro ducts in this area. However, experimental studies show that the mean rate of dry matters accumulation of wheat is a slightly lower than plain areas and traditional points can not explain this explicitly. Actually, because of low CO2 density in the plateau region, the efficiency of wheat leaf photosynthesis is just about 2/3 that of plain areas. Yet the high solar radiation and advantageous wheat community structure can make up deficiency of CO2 to some extent, so the mean rate of accumulation in the plateau region is just a slightly lower than plain areas. On the other hand, the annual average temperature is low in the plateau region which can elongate the duration of wheat growth greatly. So wheat has long time to take advantage of all the agro ecological conditions. The two factors, a slightly lower rate of dry matters accumulation and much longer duration of growing season, decide high product of dry matters in the plateau region. High harvest index wheat in the plateau region can get unusual high yield product.