Response characteristics of photosynthesis to light intensity of three non-wood forests tree species in karst habitat

【Objective】 The photosynthetic physiological responses of leaves of three non-wood forests tree species in karst habitat to light intensity were analyzed to provide theoretical basis for selection and breeding of ecological restoration plants in the karst rocky desertification area.【Method】 Used the Li-6800 portable photosynthesis meter to determine the photosynthesis-light response and chlorophyⅡ fluorescence response characteristics of Zanthoxylum bungeanum, Eriobotrya japonica and Juglans regia under the same habitat conditions,as well as the dark fluorescence parameters,One-way ANOVA using SPSS 25.0 for the light response fitting parameters,and then compared the differences in karst plateau valley photosynthetic capacity of non-wood forests tree species.【Result】 The net photosynthetic rate(P_n),transpiration rate (T_r), stomatal conductance (G_s), and electron transfer rate (ETR)light response curves of J. regia leaves were significantly different from those of E. japonica and Z. bungeanum leaves to light intensity(P<0.05, the same below),they all rose sharply at first,and then tended to be stable. The curve of E. japonica and Z. bungeanum rose significantly higher than J. regia,while E. japonica leaves still had a rising trend under high light intensity;the intercellular CO₂ concentration (C_i), stomatal limit value(L_s)and water use efficiency(WUE)of the three had no significant difference to light intensity (P>0.05),and the overall increase/decrease range was Z. bungeanum>E. japonica>J. regia. The maximum net photosynthetic rate(P_nmax)of the three non-wood forests was 2.89-8.80 μmol/(m²·s),and the apparent quantum efficiency(AQY) was 0.055 to 0.067 μmol/(m²·s). The light saturation point(LSP)was 866.06-2283.86 μmol/(m²·s),and the light compensation point(LCP)was 13.29-49.90 μmol/(m²·s). The photosynthetic performance of Z. bungeanum was the best, while E. japonica had the highest photosynthetic potential. The initial fluorescence(F_o),maximum fluorescence(F_m), and PSII photochemical efficiency(F_v/F_m)of J. regia leaves were significantly lower than those of E. japonica and Z. bungeanum.【Conclusion】 The photosynthetic physiological characteristics of E. japonica and Z. bungeanum show obvious response to light intensity. Z. bungeanum has the strongest photosynthetic capacity,while E. japonica has the best ecological adap-tability. In the future planting,it can be considered to increase the soil nutrients of E. japonica to improve its photosynthe-tic capacity,thereby increasing plant productivity. J. regia is prone to photoinhibition,and it is recommended to plant them in areas with lower maximum light intensity. In summary, Z. bungeanum and E. japonica are more suitable economic tree species for rockey desertification control in karst plateau valley area.