Reduce intensity of vegetation harvest: freshwater swamps
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Harvesting vegetation less intensely may increase its capacity to recover. Harvesting a smaller area or removing fewer plants leaves a larger population of plants to grow or spread into harvested gaps. Removing less of each plant might avoid killing them and allow them to regrow. Techniques such as selective harvesting, thinning rather than clear-cutting, and patch retention harvesting are all included within this action. Caution: In some habitats, regular disturbance such as harvesting may be necessary to maintain the composition and diversity of plant and animal communities.
Note that studies comparing areas that remain unharvested to areas that become harvested, at any intensity, are not summarized as evidence for this action.
Related actions: Reduce frequency of vegetation harvest.
Supporting evidence from individual studies
A replicated, controlled study in 2006–2011 in a forested wetland in northeast China (Mu et al. 2013) found that plots harvested at lower intensities typically contained more trees, but that understory shrub biomass peaked at intermediate harvest intensities and herb biomass was not significantly related to harvest intensity. After five years, above-ground tree biomass was greatest in plots harvested at low intensity (low: 129; medium: 100; high: 88 t/ha; statistical significance not assessed). Accordingly, density, diameter and basal area of the two most common tree species typically declined with increasing harvest intensity, and otherwise did not clearly or significantly differ between intensities (see original paper for data). Shrub biomass was greatest in plots harvested at medium intensity (low: 0.6; medium: 4.8; high: 2.0 t/ha). Herb biomass did not significantly differ between harvest intensities (low: 2.2; medium: 3.5; high: 2.6 t/ha). Methods: Nine 20 x 30 m plots were established in a forested wetland. In autumn 2006, trees were mechanically cut and removed from all nine plots: three at low intensity (25% of tree volume removed), three at medium intensity (35% volume removed) and three at high intensity (50% volume removed). Trees were counted and measured in May and October 2011. Vegetation samples were cut in August 2011, then dried and weighed.Study and other actions tested