Variation Of Soil Fauna Community In Eucalyptus Grandis Plantation Before And After The Cutting Disturbance

Previous studies have obtained a general conclusion that soil fauna is an important component in the eucalypt (Eucalyptus grandis) plantation and plays a crucial role in mass cycle and energy transfer. To understand the impacts of forest management on soil fauna is essential to achieve sustainable forest management and conservation of biodiversity. However, the structure and function of soil fauna is influenced by soil moisture and temperature caused by human disturbance. As yet, little information is available on the response of soil fauna to harvesting disturbance in the eucalypt (Eucalyptus grandis) plantation. Therefore, an investigation on soil fauna was carried out in the eucalypt (Eucalyptus grandis) plantation which was planted in 1997 and harvested in August 2006 in order to obtain an understanding of the response of soil animal community to harvesting disturbance and evaluate the ecological effect of the eucalypt plantation. Soil macro-fauna were picked up by hand. Nematodes and mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively. The aim of this research was to study the effect of harvesting on soil fauna dynamics and composition associated in the eucalypt (Eucalyptus grandis) plantation.1) 16571 individuals of soil fauna (excepting soil protozoa), belonging to 6 phyla, 14 classes and 30 orders were collected before and after cutting disturbance. 4168 and 4784 individuals of soil fauna were collected in plot 1 and plot 2 after cutting disturbance, and 355 and 978 individuals of soil fauna were more than that after cutting disturbance, respectively.2) Omnivores and saprozoic soil fauna were the main guilds in the eucalypt plantation regardless of the cutting, and two guilds accounted for more than 89% of the total. 6899 individuals of omnivores were collected before cutting, and 1183 individuals were more than that after cutting disturbance. 1456 individuals of saprozoic were collected before cutting, and 371 individuals were more than that after cutting disturbance. Other guilds accounted for 2.63% before cutting disturbance and 10.70% after cutting disturbance.3) The individuals of soil fauna had the highest in autumn and lowest in spring before cutting disturbance, however, the highest individuals in winter and lowest in summer after cutting disturbance. Fluctuations of individuals were easier affected by cutting disturbance in comparison with the groups.4) Shannon-Wiener index (H') and Pielou (J) index had same trends corresponding with season changing regardless of cutting, and the value of Pielou before cutting was higher than that after cutting disturbance. The density-group index (DG) had the opposite trend compared with the results before cutting disturbance, Simpson index (C) decreased with the time passing after cutting disturbance.5) The average soil fauna density of 4 seasons in litter layer, 5～10 cm and 10～15 cm soil layers before cutting was higher than that after cutting disturbance, however, the density of 0～5 cm soil layer before cutting was lower than that after cutting. The litter layer soil fauna (collected by Tullgren) density before cutting disturbance was higher than that after cutting disturbance in each season (except Winter), 0～5 cm soil layer had the higher density than that after cutting in each season (except Summer), but 5～10 cm soil layer was lower than that after cutting (except Summer), 10～15 cm soil layer had the higher density compared with that after cutting. The soil fauna (collected by Baermann) density of 0～5 cm(except Spring and summer), 5～10 cm (except Spring), 10～15 cm(except Spring) before cutting disturbance had the higher density than that after cutting in each season.6) The soil macro-fauna had the higher individual number than that after cutting (except Winter), groups was lower than that (except Spring). Meso-micro soil fauna had the lowest individual number in spring, and the highest in autumn before cutting, however, lowest individual number in summer, and the highest in winter after cutting.7) There were 16 groups increase after cutting, and collembolan individual number counted for 70.85% of the total, and hemiptera, gastropoda, tardigrada, harpacticoida and pauropoda weren't collected after cutting disturbance, which counted for 0.19% of the total. 13 groups individual number decreased, acarina counted for 79.98% of the total.8) The total soil fauna individual number, acarina and collembolan had positive correlations with soil temperature, but nematode had negative correlation before cutting, and all studied items had positive correlations with soil water content and organic matter content. All studied items had negative correlation with soil temperature after cutting, and had positive correlation with soil water content. All studied items had negative correlation with organic matter content except nematode.9) The result showed that soil fauna individual number of eucalypt (Eucalyptus grandis) plantation decreased with the harvesting time passing, its seasonal dynamics of groups fluctuated, therefore, we can get the conclusion that eucalypt (Eucalyptus grandis) plantation provided the necessary food and place to soil fauna, and eucalypt (Eucalyptus grandis) plantation can keep soil fauna diversity and stabilization. Only primary effects of cutting disturbance on soil fauna community were studied in this paper, the further researches on the effects of secondary succession of eucalypt (Eucalyptus grandis) plantation on soil fauna need further study.