Action: Add organic matter after tree planting
- Two replicated, randomized, controlled studies in the USA found that adding leaf litter or wood-chips before restoration planting increased seedling biomass, but decreased seedling emergence and survival.
Adding wood residuals to the ground increases soil nutrient content and soil moisture. It can also stimulate increases in microbial populations that can stabilize the soil structure. That may help the establishment of planted trees.
Supporting evidence from individual studies
A randomized, replicated, controlled study in 1989–1990 in a former arable field in New Jersey, USA (Facelli 1994) found that adding leaf litter to plots reduced tree of heaven Ailanthus altissima seedling emergence and survival, but increased their biomass if competing herbs were present. Plots with added leaf litter had lower seedling emergence than those without (litter: approx. 6; no litter: approx. 9 seedlings/plot). Seedling mortality in plots with litter was higher (approx. 31%) than in plots without (approx. 7%). Where competing herbs were present, seedling biomass was higher in plots with litter (no data provided). Where competing herbs were absent, biomass was similar with and without litter (no data provided). Sixteen plots (0.8 × 1 m) received dried, cleaned leaf litter from white oak Quercus alba at 150 g/m2, held in place by chicken wire mesh. The remaining 16 plots received no leaf litter. In all plots, 20 seeds had been planted to ensure regeneration.
A replicated, randomized, controlled study in 1991-1995 in a degraded temperate coniferous forest in Idaho, USA (Walsh & Redente 2011) found that addition of wood-chips before restoration planting decreased the survival rate of planted western white pine Pinus monticola seedlings. Survival rate was lower with wood-chips (10-15%) than in untreated plots (72-75%). Untreated and wood-chip addition (at 90,000 kg/ha) treatments were applied in 1991 to eight plots (3 × 10 m) at each of two hilltop sites. All sites were fertilized with nitrogen, phosphorus and potassium at 112, 56 and 90 kg/ha respectively and were planted with western white pine trees, along with shrubs and grasses, before treatments in 1991. Data were collected in 1995.
- Facelli J. (1994) Multiple indirect effects of plant litter affect the establishment of woody seedlings in old fields. Ecology, 75, 1727-1735
- Walsh J.R. & Redente E.F. (2011) Comparison of Reclamation Techniques to Re‐establish Western White Pine on Smelter‐impacted Hillsides in Idaho. Restoration Ecology, 19, 141-150