The effects of plant litter on vegetation: a meta‐analysis

Summary 1 We used data from 35 independently published studies world‐wide to analyse the effects of plant litter on the germination, establishment, species richness and above‐ground biomass of plants. Overall, the short‐term effects of litter on vegetation were mostly negative, although their magnitude varied with vegetation variable, study method, experimental duration, latitude, habitat, type and quantity of litter and target species. 2 Species richness was more affected than above‐ground biomass by litter, suggesting that litter may play a direct role in structuring plant communities as well as influencing competition in productive habitats. Litter had a stronger overall effect on plant germination than on establishment, suggesting that a litter‐reducing disturbance will have more effect early in the growth season. 3 On average, vegetation was more affected by litter in field than in glasshouse studies and during 2‐year than during 1‐year studies. The effect on biomass switched from negative after 1 year to positive after 3 years. 4 The absolute effects of litter on germination and establishment decreased and the absolute effects on above‐ground biomass increased with latitude. Ecosystem type also influenced the effects significantly. 5 Vegetation was generally more depressed by higher litter quantities. Litter composed of forbs and tree leaves had a stronger effect on vegetation than grass litter. The impact of a certain type of litter may therefore be related to its decomposition rate. 6 Tree species were more affected than forbs and grasses by litter, at least at the colonization stage.