关键词: 土壤水分, 遮荫水平, 光合特性, 时空分异, 分析尺度, 景观格局脆弱度, 南四湖湿地, 空间统计学

Abstract: The effects of different soil moistures and shading levels on stomatal conductance(G_s),net photosynthetic rates(P_n),transpiration and leaf water potential (LWP) of cotton (variety Zhongmian No.23) grown in pots from the seedling to flower bud stages in summer noon were evaluated.We designed three shading levels:no-shading(CK),75% shading (DN), 40% shading(SN);and three soil moistures:85～100%(high water,HW),65%～85% (mediun water,MW)and 45%～65%(low water,LW)of field water-bolding capacity.The G_s of DN and SN increased by 16.69% and 28.01% compared with CK at HW,respectively,while the P_n of DN and SN declined by 45.74% and 20.54%,respectively.The G₅ of DN and SN enhanced by 28.86% and 23.28% compareds with CK at MW,respectively,while the P_n of DN and SN decreased by 31.97% and 1.64%,respectively.The G_s of CK,DN and SN did not exhibit significant differences at LW,while P_n of DN and SN reduced by 46.22% and 13.45%,respectively.Significant difference in G_s did not exist between DN and SN at the same soil moisture,but there was significant differnece in P_n between them (except at LW).It was suggested that G_s declined with the increasing of leaf-to-air vapor pressure difference(VPD) and showed weak correlation with P_n by regression.The combined effects of soil moistures and shading levels on LWP and transpiration rate were not significant.There was no significant difference in LWP and transpiration rate among three shading treatments.Contrasted to treatment CK,intercellular CO₂ concentration (C_i) in DN and SN at HW,MW and LW increased significantly,except no arrarent change of C_i in SN at MW.

Key words: Soil moisture, Shading levels, Photosynthetic characteristics, landscape pattern vulnerability, spatial statistics, analysis scale, Nansihu Lake wetland, temporal-spatial differentiation.