| Decay of live standing trees is a general problem in forest management, and damages both economic and ecological benefits of forest, which must be controlled. It was not difficult, in forest land survey, to find that the decay of live standing trees was localized; some research also showed decay took place in a obviously higher or lower frequency in some certain environment, which indicated that site conditions had great effects on the occurrence and development of decay, so it will provide theoretical basis and new thoughts for the decay prevention and cure to investigate the effects of site conditions on decay. Korean Pine, which is one of dominant and precious tree species in northeast forest region, China and is protected by the country, has a high research value. The Korean Pine live standing trees in mixed broadleaf-conifer forest of Xiaoxinganling Mountains was taken as the research object, in which non-destructive testing technologies in the field and laboratory analysis methods were applied to make an accurate estimation and quantitative describe of decay conditons inside trunks of trees, then on this basis the effects of site conditions on degree of tree trunk decay were studied in order to protect the tree species from the harm of decay and reduce relevant losses.The main research contents include:①Quantative detection of degree of decay. Resistograph, estimating weight loss ratios of wooden cores, near infrared and infrared spectroscopic analysis were employed to estimate and quantitatively describe the inner decay of Korean Pine trunks. The degree of decay obtained from weight loss ratios of wooden cores were regarded as the truth value, based on which the other methods’ results were analyzed and evaluated, and the reliable methods with consistent results with the truth values were selected to establish quantative detection methods for degree of decay. ②Effects of site conditons on degree of decay in Korean Pine trunks. Site conditions including soil physical-chemical properties (pH, organic matter content and so forth,12 in total), topographic conditons (elevation, gradient, slope aspect and slope position), microclimate (surface temperature, air temperature, humidity and illumination intensity) and conditions of live standing trees theirselves (sap-and heart-wood moisture contents and diameters at the breast height) were studied in categories for their effects on degree of decay.③Comprehensive analysis. Site condition indexes those had a relative strong correlation with degree of decay were chosen and transformed into a few factors with factor analysis method, and then correlations between the degree of decay and factors were analyzed. Eventually the relationship between various site condition indexes was studied with correlation coefficients.Research results showed that Resistograph detection was able to make an accurate estimation for the degree of decay in Korean Pine trunks and truthfully reflected decay conditions inside trunks, while near infrared spectroscopic analysis could only approximately estimate degree of trunks decay, and was inferior to the Resistograph detection on accuracy and reliability. Degree of decay determined by Resistograph (Ez) related with truth value of degree of decay (ES.determined by estimating weight loss ratios of wooden cores) significantly (r=0.905, P<0.01). and the two kinds of results could be transformed to each other. The correlation coefficient of spectra and truth values of degree of decay (ES) in near infrared spectra prediction model was 0.697.Soil physical-chemical propertiy indicators showed strong correlations with degrees of decay in Korean Pine trunks only when the soil sample was collected near trunks among all the three different sampling positons (near trunks,5 meters away from trunks at the upper/lower parts of slopes) under trees. Moisture contents (r=0.642. P<0.01) and organic matter contents (r=0.639, P<0.01) of soil near trunks most strongly related with degree of decay, followed by soil total N contents (r=0.576. P<0.01) and C/N ratio (r=0.512.P<0.01). Soil pH. bulk density, available P and hydrolyzed N contents all related with the degree of decay significantly (P< 0.01 or P<0.05) as well, but the degree of correlation was lower.Only did slope aspect and slope position among topographic conditions (elevation, gradient, slope aspect and slope position) have obvious influence on degrees of decay in Korean Pine trunks. Decay occurrence rate was the highest at the north slope, which was due to the fact that the north slope was nightside and therefore the humidity there was high. The degree of sample trees decay at the middle part of slopes was significantly higher (P=0.018<0.05) than that at the upper part of slopes, which was because that soil moisture contents at the middle part of slope were significantly higher (P=0.016>0.05) than that at the upper part of slope.Microclimate factors at different time intervals (7 observations between 8:00-16:00 in a day) related with the degree of sample tree decay to different extents. The daily average values of microclimate factors showed the strongest correlation with degree of decay (determination coefficient R2=0.612 in principal component regression, similarly hereinafter), followed by the observation values of microclimate factors at 8:00 (R2=0.459) and 14:00 (R2=0.546). Surface temperatures and illumination intensity both had a significantly negative correlation with degree of decay at all the observing sessions, while only at a part of observing sessions did air temperature and air relative humidity both significantly relate with degree of decay (negatively and positively, respectively). The surface temperature, air humidity and illumination intensity under healthy sample trees were significantly higher (P<0.01) than that under decayed sample trees, while air relative humidity was just the opposite (P<0.01), which suggested that Korean Pine live standing trees were more vulnerable to the decay by fungi in the microclimate of weak illumination, lower temperature and high humidity.Degrees of decay in sample trees related negatively and significantly with moisture contents of sap-and heart-wood (correlation coefficient r equals-0.715 and -0.749, respectively), and moisture contents of sap-wood (at 0.01 level) and heart-wood (at 0.05 level) in healthy sample trees were significantly higher than that in decayed sample trees, which suggested that moisture inside live standing trees were reduced because of decay and the decreasement rose with increasing degrees of decay.Site condition indexes could be classified into 5 categories, which were the factor of illumination intensity and temperature, factor of soil nutrients, factor of soil moisture contents and pH, factor of slope positions and factor of soil bulk density. The factor of illumination intensity and temperature showed the strongest correlation with degrees of decay (r=0.488, P<0.05), followed by the factor of slope positions (r=-0.400, P<0.05) and the factor of soil moisture contents and pH (r=0.385, P<0.05). The factor of soil nutrients and the factor of soil bulk density both didn’t correlate with the degrees of decay significantly.There were significant correlations between most site condition indicators, among which soil organic matter content had a significant effect on other soil physical-chemical indicators (moisture content, pH, total N content, C/N ratio, available P content and bulk density), so did the surface temperature and illumination intensity on the soil moisture content and other soil property indicators 7 in total (the other six indicators were organic matter content, pH, total N content, C/N, available P content and bulk density) and so did slope position on the soil moisture content, soil bulk density and C/N ratio. |
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