Paweł Horodecki, Andrzej M. Jagodziński, Marcin K. Dyderski
Invasion from the canopy: altered litterfall and nutrient input in European temperate forests
Dendrobiology 2026, vol. 95: 77-95
https://doi.org/10.12657/denbio.095.006
Abstract:
Non-native tree species effects on litterfall production and element inputs remain difficult to generalize, particularly in mature, mixed-species forests under long-term conservation, where structural complexity and species interactions may override simple biomass-driven patterns. Over three consecutive years, we quantified total and leaf-litterfall biomass and associated inputs of major elements (C, N, P, K, Ca, Mg, Mn) across 14 stands differing in species composition and invasion status in Wielkopolska National Park (western Poland). We compared functionally relevant forest types dominated by: (i) invasive Quercus rubra versus native Q. petraea; (ii) invasive Robinia pseudoacacia versus native maples (Acer platanoides and A. pseudoplatanus); and (iii) Pinus sylvestris forests differing in understory composition (with native A. pseudoplatanus, invasive Prunus serotina, or both). These forest types represented habitat-level competition betweennative and non-native species.
Maximum differences in mean annual litterfall among individual plots reached 1821 kg ha−¹ (25%), however, post-hoc comparisons revealed no consistent differences within forest-type groups. Linear mixed-effects models showed no effect of forest type on total litterfall biomass, whereas leaf-litterfall differed significantly among types, the highest in Q. rubra forests (4466±254 kg ha−¹ year−¹) and the lowest in P. sylvestris forests with P. serotina understory (3266±186 kg ha−¹ year−¹). Mean annual inputs of all tested elements differed significantly among forest types. While C input was tightly linked to leaf-litterfall biomass (R²=0.94, p<0.0001), inputs of other elements showed weak or non-significant relationships with litterfall quantity. These results demonstrate that differences in leaf chemical composition among species outweigh differences in litterfall biomass in determining element inputs in mixed forests. Non-native tree species influenced ecosystem functioning not primarily by increasing litterfall quantity, but by altering the chemical quality of litter inputs. Quercus rubra contributed large quantities of chemically recalcitrant litter, whereas R. pseudoacacia and P. serotina supplied smaller amounts of element-rich litter capable of accelerating nutrient turnover. Consequently, the ecological effects of non-native tree species on forest element inputs cannot be inferred from litterfall quantity alone. Instead, species-specific litter chemistry and proportional canopy contributions play a dominant role, weakening simple biomass-element relationships and underscoring the need to integrate litter quality into assessments of non-native species impacts on forest biogeochemical cycling.
Keywords: litterfall, elements cycling, biological invasions, invasive species, tree species effect, carbon,
nitrogen, calcium, potassium, magnesium, phosphorus