华山松、油松不同叶龄针叶光合特性对林窗式疏伐的响应

目的]通过对比研究华山松和油松不同叶龄针叶形态、光合速率、叶绿素和叶氮含量对林窗式疏伐的响应,探讨林窗大小、叶龄和树种对林窗式疏伐后叶光合特性响应的影响。方法]2008年在30年生华山松和油松混交人工林中,设置对照、小林窗(80 m2)和中林窗(110 m2)处理,2013年以对照样地内和林窗边缘华山松和油松为研究对象,测定其当年生、1年生和2年生叶比叶重(LMA)、单位叶面积叶绿素a(Chl a)、叶绿素b含量(Chl b)、氮含量(N)、最大净光合速率(Amax)、光合氮利用效率(PNUE)等指标。结果]小林窗和中林窗疏伐对叶光合特性影响一致,均对当年生叶影响不显著,但显著改变了1年生和2年生叶绿素含量、N和PNUE,提高了其Amax。华山松叶LMA、叶绿素含量、N、Amax均低于油松,两树种多年生叶对林窗式疏伐的响应也明显不同:林窗边缘华山松1年生和2年生叶LMA和N与对照差异不显著,但叶绿素含量低于对照,PNUE和Amax显著高于对照;林窗边缘油松1年生和2年生叶LMA和PNUE与对照差异不显著,但N和Amax显著高于对照。结论]80 110 m2林窗疏伐显著改变叶光合特性,提高其光合潜力;林窗疏伐影响1年生和2年生叶光合特性,对当年生叶影响不显著;华山松和油松对林窗式疏伐的响应特征存在差异。

Differential Responses of Age-related Leaf Photosynthetic Characteristics of Pinus armandii and Pinus tabuliformis to Gap-model Thinning

Objective] To study the responses of age-related leaf morphology, photosynthetic rate, photosynthetic pigments, and leaf nitrogen of Pinus armandii and P. tabuliformis to gap-model thinning, intending to explore the influences of gap size, leaf age, and species on leaf characteristics after thinning.Method] The small gaps (80 m²), intermediate gaps (110 m²) and a control were set in a 30-year-old mixed P. tabuliformis and P. armandii plantation in 2008. The P. armandii and P. tabuliformis in control plots and gap-edged pines were chosen as test materials, and the leaf mass per area (LMA), area-based chlorophyll a, chlorophyll b, nitrogen content (N), maximum photosynthetic rate (A_max), and photosynthetic nitrogen use efficiency (PNUE) of current year, one-year-old, and two-year-old leaves were measured in 2013.Result] Small and intermediate gaps had no significant influences on current-year leaves of P. armandii and P. tabuliformis, while significantly altered chlorophyll,N content, and PNUE, enhanced A_max of one-year-old and two-year-old leaves. P. armandii had lower LMA, chlorophyll content, N, and A_max. Moreover, older leaves of P. armandii and P. tabuliformis showed differentiated responses to gap-model thinning:gap-edged P. armandii showed lower chlorophyll content, higher A_max and PNUE than the control, while the LMA and N were no significantly different with the control; gap-edged P. tabuliformis had higher A_max and N than the control, while LMA and PNUE had no obvious difference with the control.Conclusion] Gaps in size of 80-110m² can alter the leaf characteristics and improve its photosynthetic capacity. Gap-model thinning has significant influences on the older leaves, while has no influence on current leaves. P. armandii and P. tabuliformis have different responding strategies to gap-model thinning.