间作对桑树和谷子生长和光合日变化的影响

以桑树和谷子为研究材料，探讨了大田条件下，桑树-谷子间作对桑树和谷子的干物质生产、土地利用率和光合日变化的影响.结果表明：桑树-谷子间作条件下，间作桑树的株高、地茎、根长和枝条数分别比单作桑树增加了6.0%、13.7%、6.8%和14.8%，且间作桑树的产叶量比单作桑树增加了31.3%；间作谷子与单作比较，其株高和根长的变化不大.桑树-谷子间作增加了土地当量比，提高了土地利用率.单作、间作桑树和谷子叶片在12:00时均表现出明显的光合午休现象，且单作桑树的光合午休现象比间作桑树严重.桑树-谷子间作提高了中午时桑树叶片气孔导度和水分利用率，增加了桑树光合碳同化能力，抑制了桑树叶片实际光化学效率、电子传递速率和最大光化学效率的下降，从而减缓了桑树的“光合午休”现象.桑树 谷子间作能明显提高桑树叶片的光合生产能力.

Urban ecosystem health assessment of Huzhou, Zhejiang Province of East China based on fractal theory

In view of the deteriorating urban ecosystem,a combination of landscape pattern index,water environment parameters,and socio-economic indicators was adopted to build an urban ecosystem health assessment index system.Based on self-similarity theory and fractal theory,the system fractal dimension was calculated,and the link between the fractal dimension and ecosystem health was set up to quantitatively evaluate the urban ecosystem health status and analyze its dynamic trend at different stages of urbanization.By analyzing and calculating the ecosystem fractal dimension of Huzhou City in 1997,2001,and 2005,the fractal dimensions in the three years were obtained,which were 0.8934,1.1723,and 1.2619,respectively,foreshowing that the urban ecosystem of the City was growing towards an unhealthy condition.This study indicated that the development of Huzhou City’s urbanization had made a negative effect on the urban ecosystem,and thus,more attention should be paid to the ecological and environmental protection during urban planning and construction in the future.