Litter load mainly affects the probability of forest fire occurrence and spread to disaster. The analysis of the degradation effect of Acrophialophora yunnanensis on litter with different moisture content is of great significance for fire prevention through biological fire prevention.

Coniferous and broad-leaved litters were treated with fermentation broth, purified crude enzyme and living fungi of P. yunnanensis to degrade respectively, then the weight loss rate was determined, and the degradation effects of three treatments on the two types of litters with different moisture content were analyzed.

Purified crude enzyme of P. yunnanensis could degrade broad-leaved and coniferous litter, and the weight loss rate of broad-leaved and coniferous litter was 10.52% and 6.27% at 10 days, respectively. For broad-leaved litter, the litter with 50%-150% moisture content was significantly degraded by fermentation broth and purified crude enzyme, while the litter with 25%-150% moisture content was significantly degraded by living fungi. For coniferous litter, the degradation effect of the litter increased with the increase of litter moisture content. The degradation effect of fermentation broth and purified crude enzyme no longer increased after the litter moisture content reached 150%, while the degradation effect of living fungi no longer increased after the litter moisture content reached 100%.

Purified crude enzyme of P. yunnanensis could degrade broad-leaved and coniferous litter obviously, and had better degradation effect on broad-leaved litter. The moisture content of litter affected degradation of litter, a certain moisture content of litter was helpful to degradation of litter, and degradation of coniferous litter was more affected by moisture content of litter than that of broad-leaved litter, while degradation effect of litter was less affected by moisture content of litter when litter was degraded by living fungi. The results will provide some reference for the study of forest fuel load regulation.

As the igniter of forest fire, the loading of fine dead fuel on the forest surface determines a series of fire behaviors and the risk degree of fire occurrence. It is of great significance for forest fire risk prediction and scientific forest fire management to quickly and accurately obtain the loading value of fine dead fuels on the surface.

In this study, the fine dead fuel on the surface of 6 typical forests (Pinus massoniana Lamb. forest, Cupressus funebris Endl. forest, Soft broad forest, Cunninghamia lanceolata forest, Broadleaf mixed forest and shrub forest) in Dalou Mountain in the southwest forest region were taken as the research object. Through field investigation and indoor drying, the forest characteristics and loading values were measured to obtain the influencing factors of the fine dead fuel on the surface, and a prediction model was established.

1) The fine dead fuel loading of different forest types was significantly different, and that of Pinus massoniana Lamb. and Broadleaf mixed forest was significantly higher than that of other forests. The difference in carrying capacities between different standard plots of Pinus massoniana Lamb. forest and broadleaf mixed forest was significant, and there was no significant difference in carrying capacities among different standard plots of other stands; 2) Except for Cunninghamia lanceolata forest and shrub forest, the surface fine dead fuel loading of other forests had a significant correlation with some forest characteristic factors (forest age, canopy density, mean diameter at breast height, mean tree height, mean diameter at ground level, slope and elevation). The forest density and average crown width had no significant impact on the surface fine dead fuel loading of the study area; 3) The prediction model of the surface fine dead fuel loading of Pinus massoniana Lamb. forest, Cupressus funebris Endl. forest, soft broad forest and Broadleaf mixed forest was established. The prediction effect of Cupressus funebris Endl. forest was the best, with an error of only 3.6%. The prediction error of Pinus massoniana Lamb. forest was as high as 27.4%, which could not be applied in practice.

Through this study, the basic data of the surface fine dead fuel loading of typical forest stands in Dalou Mountain and the influencing factors and prediction models have been obtained, which is of great significance for the study of the regional loading and scientific forest fire management.

The characteristics and relationship of soil aggregate distribution, stability and nutrient content were analyzed in Pinus massoniana plantation of age groups in fragile ecological area of Guizhou.

3 middle-age forest, 5 near-mature forest and 3 over-mature forest plots were set up in Fenggang county, Zunyi city, Guizhou province. Soil aggregates of different particle sizes were obtained by wet sieve method, and their mass fraction, mean mass diameter (MWD), geometric mean diameter (GMD) and soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) contents were calculated.

1) The soil aggregate mass fraction reduced with the decrease of particle size in P. massoniana plantation of different age groups (P < 0.05), while MWD and GMD were not significantly different among 3 age groups (P > 0.05). 2) With the increase of age group of P. massoniana plantation, SOC content of soil aggregates decreased first and then increased (P < 0.05). TN content gradually accumulated, and the TN content in near-mature forest and over-mature forest was significantly higher than that of middle-age forest (P < 0.05). TP content decreased gradually, and the TP content in middle-age forest and was significantly higher than that of near-mature forest and over-mature forest(P < 0.05); As the particle size of soil aggregates decreases, SOC content of aggregates increases gradually, while the TN content decreased gradually. The SOC contents in clay particles and microaggregates were significantly higher than that in macroaggregates(P < 0.05), and the TN content in macroaggregates was significantly higher than that in clay particles (P < 0.05). 3) The SOC content in macroaggregates and TP content in microaggregates were significantly positively correlated with the macroaggregates distribution, clay particle distribution, MWD and GMD (P < 0.05); The SOC content of microaggregates was negatively correlated with the macroaggregates distribution, clay particle distribution, MWD and GMD (P < 0.05).

The change of age groups of P. massoniana plantation affected the distribution of soil aggregates and the changes of aggregate nutrients, and there was a significant correlation between aggregate nutrients and the distribution and stability of aggregates. The basic data of aggregate distribution, stability and nutrients of P. massoniana plantation can be obtained, which is of great significance for evaluation of soil structure and erosion resistance and forest management of the plantation at fragile ecological area of Guizhou.