The decomposition of deadwood plays a key role in forest carbon emissions. Most pieces of downed deadwood are partially suspended above the forest floor, but how this suspension affects decomposition rates is typically ignored and remains largely unexplored. Here, we combine field observations and experimental manipulations to explore how partial suspension of downed wood (that is, wood debris in contact with the ground) influences decomposer communities and patterns of decomposition in a lowland tropical forest. Experimental manipulations of wood sticks showed that small-scale suspension above the forest floor (ca. 5 cm) slowed decomposition and altered microbial community assembly, regardless of whether the suspended section was connected to a piece of downed wood. Across a 41-year chronosequence of dead trees, the average percent of wood volume suspended above the forest floor decreased during the initial 10 years post-death, but this trend reversed after 10 years, with the oldest logs being the most suspended. Among downed woody pieces sampled in situ, sections suspended above the forest floor had less moisture, fewer macrofungi, and more photosynthetic growth (for example, moss, algae, and so on) than downed sections of the same bole. Surprisingly, wood density, termite presence, and mass-specific respiration did not differ with ground contact. Combined, these data suggest that suspension within downed wood reduces moisture content, influences decomposer community assembly, and contributes to the strong variability in decomposition rates. The strong effect of partial suspension within downed wood pieces heightens concerns about the accuracy and applicability of experiments and surveys focused on down deadwood, which are the foundation of our understanding of wood decomposition and associated carbon losses.

枯木的分解在森林碳排放中起着关键作用。大多数倒下的枯木都部分悬浮在森林地面上方，但这种悬浮如何影响分解率通常被忽视，并且在很大程度上仍未被探索。在这里，我们结合实地观察和实验操作来探索倒下的木材（即与地面接触的木材碎片）的部分悬浮如何影响低地热带森林中的分解者群落和分解模式。对木棍的实验操作表明，无论悬挂的部分是否与一块倒下的木头相连，森林地面（约 5 厘米）上方的小规模悬浮物都会减缓分解并改变微生物群落的组装。纵观 41 年枯死树木的时间顺序，在死亡后的最初 10 年内，悬浮在森林地面上方的木材体积的平均百分比有所下降，但这种趋势在 10 年后发生逆转，最古老的原木悬浮最多。在原位取样的倒下木质碎片中，悬挂在森林地​​面上方的部分比同一树干的倒下部分水分更少，大型真菌更少，并且光合作用生长更多（例如苔藓、藻类等）。令人惊讶的是，木材密度、白蚁存在和质量特异性呼吸并没有因地面接触而发生变化。综合起来，这些数据表明，倒下的木材中的悬浮物降低了水分含量，影响分解者群落的组装，并导致分解率的强烈变化。