The Relationship Between Chlorophyll And SPAD And The Related Factors For Major Broadleaved Tree Species In Northeast China

Chlorophyll content is the basic, and vital physiological parameter in the research of forest ecology. An indirect, timely and nondestructive detection of leaf chlorophyll status is of great importance for the immediate assessment of forest condition for managing and conserving forest ecosystems. The eight main broadleaved tree species in northeast China were chosen for this study included Mongolian oak (Quercus mongolica Fisch.), white birch (Betula platyphylla Suk), Amur cork-tree (Phellodendron amurense Rupr), Manchurian walnut (Juglans mandshurica Maxim), Manchurian ash (Fraxinus mandshurica Rupr), maple (Acer mono Maxim), Amur linden (Tilia amurensis Rupr) and elm (Ulmus propinqua Koidz.-U. japonica Sarg). The sampling time was divided into three periods-spring, summer, autumn. Dimethyl sulfoxide (DMSO)was used to extract pigment, SPAD-502 meter was used to measured SPAD value. Measuring the characteristics of the chlorophyll, carotenoid, SPAD value in different seasons.The optimal model of photosynthetic pigment and the SPAD value were set up, and analysis of related factors affected the accuracy of estimates of chlorophyll. The main results are as follows:(1)The maximum value of Chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, SPAD appeared in summer of the eight tree species, and the minimum appeared in spring or autumn. However, the maximum of a/b was found in spring or summer, the minimum in autumn. The leaf traits also existed certain differences in different seasons. The maximum value of LMA and LT appeared in summer. But the maximum of LD value in autumn or summer and the minimum in spring. On the contrary, the maximum value of LMC was found in spring, minimum in autumn or summer. The difference of pigment index and leaf traits between tree species have a different results in different seasons.(2)The result indicates that the correlation between the SPAD value and total chlorophyll, Chlorophyll a, chlorophyll b, carotenoids is significant that accounted 99%,99%,95.5%,94% respectively in different seasons and total of different species. The optimal relationship model mostly is power between SPAD values and Chlorophyll a, chlorophyll b, total chlorophyll of eight species in different seasons and total, a few is quadratic and exponential, occasionally have a logarithmic. However, the optimal model between SPAD values and carotenoids 50% is quadratic, the remaining is exponential or power. Eight species merger in different seasons the optimal relationship model is power between SPAD values and Chlorophyll a, chlorophyll b, total chlorophyll except SPAD-Chia in summer, but the optimal relationship model have a variety results between SPAD values and carotenoids. The combine of eight species and three seasons the optimal models between SPAD values and Chlorophyll a, chlorophyll b, total chlorophyll were power, but quadratic in SPAD values and carotenoids. Thus, the main relationship model between SPAD values and Chlorophyll a, chlorophyll b, total chlorophyll is power for eight species, but the main relationship model is quadratic between SPAD and carotenoids.(3)The coefficient of determination R2 of optimal relationship model between SPAD and Chlorophyll a, chlorophyll b, total chlorophyll on per unit area were higher than on unit mass. But the R2 have no significant differences in two units of SPAD and carotenoids. The order of R2 of SPAD and various indicators all is SPAD-Chltot?>SPAD-Chla>SPAD-Cglb>SPAD-Car in different units. The comparative result between the two kinds of model:Power function R2 were greater than the homographic, the gap between 0-0.1. But the RMSE comparing results is different, higher or lower, the gap between 0-0.54 except white birch. Two model R2 and RMSE difference is smaller. So homographic can be as a prediction model of chlorophyll for eight main broad leaved tree species in northeast China.(4)The diurnal maximum SPAD values mostly occurred between 12:00 to 18:00, and minimum values in 4:00-6:00, with the variation in the range of 2-17% in clear days during the growing season. Maximum estimation error were -20～-10% for eight tree species, occurring in 4:00-6:00. while error was within ±9% during the other measurement time period except for the Spring of Q. mongolica. So, it’s advised that the SPAD measurement should be avoided the 4:00-6:00 in northeast China.The correlation between leaf SPAD and PPFD (photosynthetic photon flux density), LMA (leaf mass area), and LWC (leaf water content) was not consistent within tree species and measurement period. Leaf traits contributions are small for the model basis on per unit area, however, LT and LMA have larger contributions for the model basis on unit mass(0.02～0.22), LMC and LD have small contributions for the model basis on unit mass(0.01～0.11).So with chlorophyll per unit area for fitting model is more accurate and convenient.