Introduction : Management practices are essential for maintaining forest ecological functions under increasing diseases and pest disasters. The effects of nitrogen fertilization (NF) and clear-cutting (CC) on the soil microbial community structure and greenhouse gases emission were investigated of pinewood nematodes ( Bursaphelenchus xylophilus )-infected Masson pine ( Pinus massoniana ) plantations. Outcomes : CC increased the soil microbial biomass carbon (SMBC) and soil microbial biomass nitrogen (SMBN) contents relative to the control (CK). NF increased the SMBN but had no significant effect on the SMBC content. The total fungal and bacterial abundances increased in the CC treatment compared with the CK, but there was no significant difference between the NF and CK. The cumulative soil CO 2 emission (2.35 t C·hm −2 ) was higher than that of CK (1.65 t C·hm −2 ) in summer, and the cumulative annual N 2 O emission (16.90 kg N·hm −2 yr −1 ) of NF was approximately 47 times of CK (0.36 t N·hm −2 ·yr −1 ). CC increased the CO 2 flux (2.21 t C·hm −2 ) in summer but have no significantly effects on N 2 O emission. Conclusion : These results indicated that NF and CC practices changed forest soil microbial community structure and affected soil greenhouse gas emissions in pinewood nematodes -infected Masson pine plantations. The CO 2 emission rates increased in the NF and CC treatments, which reduced the carbon sequestration function of forests and had a negative impact on climate change.

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A general solution for dynamic stability of the fluttered mode of damped, fluttered systems subjected to parametric random excitations is presented in this paper. First, the system equations are pairwisely uncoupled by a modal analysis based on normal modes of the system at the onset of fluttering. The stochastic averaging method is then applied to obtain Ito's equation governing the amplitude of the fluttered mode. Finally, the Lyapunov exponent of the fluttered mode is derived, from which the criterion for asymptotic sample stability of the mode is determined. A cantilevered beam acted upon by a static follower force and a white noise parametric excitation at the free end, and a skew panel subjected to an aerodynamic force in the chordwise direction and a white noise excitation in the spanwise direction are demonstrated as examples. Numerical results show that, although the static follower force or the aerodynamic force exceeds the flutter load, the fluttered mode of the beam or the panel may remain stable in the sense of asymptotic sample stability due to the presence of the white noise excitation.

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