酸雨与凋落物复合作用对柳杉叶片色素和反射光谱的影响

采用盆栽3年生柳杉Cryptomeria fortunei幼苗研究了酸雨(pH 4.0,Tr1),柳杉凋落物(60 g,Tr2)以及酸雨和柳杉凋落物复合作用(Tr3)对其叶片色素质量分数和反射光谱的影响,并对柳杉叶片色素质量分数与光谱反射率、一阶微分光谱和反射光谱参数的相关性进行了分析。结果表明:①Tr1,Tr2和Tr3处理下,柳杉叶片叶绿素a质量分数比对照分别降低了11.6%,26.1%和39.1%,说明酸雨增强了凋落物化感作用对柳杉叶绿素a质量分数的抑制作用,加快了其降解速度。②Tr1和Tr2处理均显著减小了光谱参数反射率倒数、改良的归一化差值指数和反射光谱比值指数a等(P<0.05)。Tr3处理的柳杉反射光谱参数均对照有极显著差异(P<0.01)。③叶绿素质量分数与柳杉反射和一阶微分光谱呈极显著相关(P<0.01),可见光和近红外区域是酸雨与凋落物复合作用下柳杉幼苗反射光谱和微分光谱的敏感区域。④反射率倒数、归一化差值指数和蓝边位置等11个反射光谱参数与叶绿素a,叶绿素b质量分数和叶绿素a/b之间的相关性达到显著水平(P<0.05),其中反射率倒数、蓝边幅值、蓝边面积、黄边幅值、黄边面积、红边幅值和红边面积与柳杉叶绿素a,叶绿素b质量分数和叶绿素a/b之间的相关性高于或接近0.8,说明酸雨与凋落物作用下柳杉幼苗反射光谱特征及其参数可用来估算叶绿素质量分数,并为利用反射光谱监测柳杉胁迫提供了可能。

Pigment content and reflectance spectrum of Cryptomeria fortunei with acid rain and litter treatments

 To understand the combined effects of acid rain and litter on Cryptomeria fortunei seedlings， pigment content and reflectance spectra in 3-year-old C. fortunei seedlings were tested with treatments of the control（ck）， acid rain stress （pH 4.0， Tr1）， litter addition （60 g， Tr2） and their combination （Tr3）， which then compared with a correlation analysis. Results showed that compared to the control， chlorophyll content decreased 11.6% in Tr1， 26.1% in Tr2， and 39.1% in Tr3. Acid rain also decreased the reflectance spectral parameters （SR₆₈₀, NDVI, PSNDa, PSNDb, RARSc, and SIPI） but increased mSR₇₀₅ and RARSa（P＜0.05）. For Tr2, some reflectance spectral parameters（RR, SR₆₈₀, mSR₇₀₅, NDVI, and PRI） were significantly less than the control（P＜0.05）, and Tr3 made highly difference compared to the control（P＜0.01）. Reflectance between 514-629 nm and 690-1 000 nm had a highly significant correlation（0.80＜r＜0.98），which was near 0.98,  with the chlorophyll content and chlorophyll a/b. In addition, r between chlorophyll content and the first derivative of reflectance spectra was highly significant within 424-486 nm, 552-682 nm, 698-755 nm, and 762-772 nm, that maximum r was near 0.96. The reflectance spectrum parameters, such as RR, RARSa and λ_red, were significantly correlated（P＜0.05） with pigment content. The correlation coefficients between reflectance spectral parameters （R_R, D_λblue, S_blue, D_λyellow, S_yellow, D_λred, and S_red） and chlorophyll a, chlorophyll b, and chlorophyll a/b were near 0.8. Therefore, acid rain enhanced the allelopathic effect in litter on chlorophyll a by increasing chlorophyll a degradation; visible light and the near infrared region were the sensitive areas of reflectance and first derivative in the leaves of C. fortunei; and reflectance spectral parameters RR, D_λblue, S_blue, D_λyellow, S_yellow, D_λred, and S_red could be used to evaluate chlorophyll a, chlorophyll b, and chlorophyll a/b. ［Ch, 4 fig. 5 tab. 41 ref.］