[Evaluating the growth status and threatened factors for old trees in China]. / æˆ‘å›½å¤æ ‘èµ„æºçš„ç”Ÿå­˜çŽ°çŠ¶è¯„ä¼°åŠå¨èƒå› ç´ åˆ†æž.

Old trees are critical components of ecosystems, with important ecological function and high genetic diversity. To strengthen the protection and management of old trees, we analyzed the distribution, survival and protection status of old trees and their threatened factors in China. The results showed there were a total of 10.66 million old trees in China. The Inner Mongolia Autonomous Region and Yunnan Province had more than one million trees, respectively. For 440000 old trees in 102 counties, 94.3% grew normally, 5.5% in a weak or endangered status, and 0.2% had been dead. The main factors threatened to old trees included natural disasters (e.g., elevated temperature, drought, fire), urbanization, land use, pests and diseases, and cutting and stealing. Among those factors, damage from pests and diseases was the most serious, which was found in 83 counties (81.4%). The second important threatened factor was natural disasters, which occurred in 68 regions (66.7%). In addition, most of the old trees (around 89%) grew in remote countryside, lacking of enough protection. Modern technologies should be used to protect old trees, such as using unmanned aerial vehicles to monitor the growth status of old trees, strengthening pest and disease control, and avoiding natural disasters. Establishing a database of old tree resources is important to update and share information timely to avoid stealing and felling old trees.

[Determination of chlorophyll a and b using absorption spectrum].

Chlorophyll a and chlorophyll b play a significant role in the plant growth process. Precise determination of its content could provide the scientific basis for the corps growth state, the plant pathology diagnosis and so on, and is the key point of implementing accurate agriculture. The authors transfered the absorption spectrum experiment data of chlorophyll a and chlorophyll b determined by predecessor into a transmission spectrum. Observing the transmission spectrum using human eyes, the color of chlorophyll a and chlorophyll b was obtained. Thus, according to the predecessor's experiment curve of absorption spectrum of chlorophyll a and chlorophyll b, combining the three primary color principles of colorimetry, and choosing a standard light source with spectrum power distribution similar to D65 as the illumination, the authors determined their chromaticity coordinates in the 1931CIE-x, y chromaticity diagram: Chlorophyll a is (0.198 1, 0.334 1), which falls in the cyan color region; Chlorophyll b is (0. 270 4, 0. 566 3), which falls in the yellowish green region. The main point of above processing is: reducing the spectrum curves of chlorophyll a and the chlorophyll b to coordinates on the chromaticity diagram, and the result could offer the essential theoretical support for a new non-contact, long-distance and non-damage technology to determine the pigment content in single leaf or mass.