Soil Biological Changes for a Natural Forest and Two Plantations in Subtropical China

Conversion of natural forests into pure plantation forests is a common management practice in subtropical China.To evaluate the effects of forest conversion on soil fertility, microbe numbers and enzyme activities in topsoils (0-10 cm)were quantified in two 33-year-old monoculture plantations of Castanopsis kawakamii Hayata (CK) and Cunninghamia lanceolata Lamb. (Chinese fir) (CF), and compared to a neighboring relict natural C. kawakamii forest (NF), in Sanming,Fujian. Five soil samples were collected once each in January, April, July, September and November in 2000 in each forest for laboratory analysis. Over the sampling year, there were significant differences for bacteria, fungi and actinomycetes between forests and between seasons (P ＜ 0.05). The largest bacteria and fungi populations were in NF, while CF contained the greatest number of actinomycetes. There were also significant differences (P ＜ 0.05) with microbial respiration for forests and seasons. Additionally, compared with NF, urease and acid phosphatase were significantly lower (P ＜ 0.05)in CK and CF. Also, the correlations of soil hydrolysable N and available P to soil microbial and enzymatic activities were highly significant (P ＜ 0.01). Thus, to alter the traditional Chinese fir monoculture so as to mimic the natural forest conditions, managing mixed stands of Chinese fir and broadleaf trees or conducting crop rotation of conifers and broadleaf trees as well as minimizing forest disturbances like clear-cutting, slash burning and soil preparing, could be utilized.

Impact of Continuous Chinese Fir Monoculture on Soil

Soil properties were investigated in sites where three succeeding generations of Chinese fir (Cunninghamia lanceolata (Lambert) Hooker) in Nanping, Fujian, China, were cultivated in order to show the impact of a repeated monoculture on site productivity. Compared with the first generation (FG) stand the soil structure deteriorated in the second generation (SG) and the third generation (TG) stands. For instance,the destruction rate of the peds increased by 55%-115% in the SG and the TG stands compared to the FG stand. Soil nutrient storage and nutrient availability also decreased in the SG and the TG stands. For surface soils of 0-20 cm, the organic matter content, total N and P, and available N and P decreased by 3%-20% relative to those in the FG stand. For many soil parameters, the differences between the FG stand and the SG and the TG stands were statistically significant (LSD test, P ＜ 0.05). Furthermore, with each succeeding generation of Chinese fir, the total number of soil microbes declined, the soil enzyme activity weakened, and the soil biological activity decreased. In order to maintain sustainable site productivity, new silvicultural practices need to be developed for management of Chinese fir plantations.

Occurrence and Culture of Mycorrhizal Fungi Associated with Oaks in Dandong Region, Liaoning Province

With both field investigation and pure culture experiments, the occurrence and optimal essential growth of mycorrhizal fungi with oaks in Dandong Region of Liaoning Province, China were investigated from 1997-2002. A total of 36 species of mycorrhizal fungi associated with oaks were observed. The results showed that the occurrence of mycorrhizal fungi was related to tree species, tree ages, and months of the year, with at least 20 fungi species being associated with more than two oak species. The highest Simpson index (SI) and Shannon index (H') values, 0.95 and 4.44 respectively, were found in the 15-25 year-old age group. The optimum month for fungal occurrence was August, when the SI and H' values were 0.97 and 5.16, respectively. Additionally, the cultivated mycorrhizal fungus grew best at temperature of 25-30 ℃ and at pH of 5-6. The results also indicated that the association between mycorrhizal fungi and oaks was common.

Collapse-type shrinkage characteristics in plantation-grown eucalypts： I . Correlations of basic density and some structural indices with shrinkage and collapse properties

Collapse-type shrinkage is one of highly refractory drying defects in low-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD), microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP), unit cell wall shrinkage, total shrinkage and residual collapse, which are associated with collapse-type shrinkage characteristics, were investigated by using simple regression method for three species of collapse-susceptible Eucalyptus urophyll, E. grandis and E.urophyllaxE.grandis, planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that : unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strong positive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA; total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but not able to be predicted ideally by any examined factors alone owing to lower R^2 value (R^2≤0.5712); residual collapse was negatively correlated with BD and DWT, linearly positively correlated with MFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used as single factor (R^2≥0.9412) to predicate unit cell wall shrinkage and RP is the relatively sound indicator for predicting residual

FRAME DESIGN OF REMOTE SENSING MONITORINGFOR VOLCANIC ACTIVITIES IN CHANGBAI MOUNTAINS

Volcanic eruption is one of the most serious geological disasters,however,a host of facts have proven that the Changbai Mountains volcano is a modern dormant one and has ever erupted disastrously. With the rapid development of remote sensing technology,space monitoring of volcanic activities has already become possible,particularly in the application of thermal infrared remote sensing. The paper,through the detailed analysis of geothermal anomaly factors such as heat radiation,heat conduction and convection,depicts the monitoring principles by which volcano activities would be monitored efficiently and effectively. Reasons for abrupt geothermal anomaly are mainly analyzed,and transmission mechanism of geothermal anomaly in the volcanic regions is explained. Also,a variety of noises disturbing the transmission of normal geothermal anomaly are presented. Finally,some clues are given based on discussing thermal infrared remote sensing monitoring mechanism toward the volcanic areas.

Succession Rules of Various Types of Soil Phosphorus in Larch Plantations

By the method of comparison and analysis, the succession pattern of total P, available phosphorus,organic P types and inorganic P types in rhizosphere and non-rhizosphere soil at different developmentstages in Larch (Larix olgensis) plantations was revealed. The result showed: when stand age increased, thecontent of available phosphorus, O-P, total P and organic P in rhizosphere soil decreased greatly or significantly,the content of inorganic P, Ca-P and Fe-P in rhizosphere soil in rhizosphere soil increased greatly orsignificantly. The content of Ca-P in non-rhizosphere soil increased with stand growing. The content of Fe-P in half-mature stand, available P and Fe-P in near mature stand, available P and Ca-P in mature stand in non-rhizosphere soil was more than that in rhizosphere soil.