Peatlands of Southeast Asia store large pools of carbon but the mechanisms of peat accumulation in tropical forests remain to be resolved. Patch dynamics and forest disturbance have seldom been considered as drivers that can amplify or dampen rates of peat accumulation. Here we used a modified piston corer, noninvasive geophysical measurements, and geochemical and paleobotanical techniques to establish the effect of tree fall on carbon accumulation rates in a peat swamp forest dominated by Shorea albida in Brunei (Borneo). Carbon initially accumulated in a mangrove forest at over 300 g C m À2 yr À1 but declined to less than 50 g C m À2 yr À1 with the establishment of a peat swamp forest. A rapid accumulation pulse of 720-960 g C m À2 yr À1 occurred around 1080 years ago as a tip-up pool infilled. Tip-up pools are common in the peatlands of northwest Borneo where windthrow and lightning strikes produce tree falls at a rate of 4 trees ha À1 every decade. A simulation model indicates that tip-up pools, which are formed across the entire forested peat dome, produce local discontinuities in the peat deposit, when peat is removed to create a pool that is rapidly filled with younger material. The resulting discontinuities in peat age at the base and sides of pool deposits obscure linkages between carbon accumulation rates and climate and require new approaches for paleoenvironmental reconstructions. Our results suggest that carbon accumulation in tropical peat swamps may be based on fundamentally different peat-forming processes than those of northern peatlands.

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An error probability analysis is performed for a communications link with convolutional coding and soft-decision Viterbi decodin implemented (FFH/BFSK) spread spectrum system. The generated signal is transmitted throu h a frequency nonjamming and additive white Gaussian noise. To reduce the effects of partial-band jamming, ratiostatistic combining is introduced at the receiver before the soft decision Viterbi decoding. With the use of convolutional coding and soft decision Viterbi decoding, the performance of the receiver is improved dramatically when the EblNj is greater than about 12 dB, and multiple hops per bit are not required in order to force the jammer to move from a partial-band to a full-band jamming strategy. on a fast frequency-hopped binary f requency-shift selective, slowly fading channe P with partial-band

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