Reduce intensity of vegetation harvest: freshwater swamps

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Share Tweet Email

View assessment score

How is the evidence assessed?

Effectiveness

60%
Certainty

30%
Harms

0%

Calculating overall effectiveness category

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.

Study locations

Key messages

One study evaluated the effects, on vegetation, of reducing the intensity of harvest in freshwater swamps (or harvesting at different intensities). The study was in China.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

Herb abundance (1 study): One replicated, controlled study in a freshwater swamp in China reported that overall herb biomass was statistically similar in plots logged at different intensities five years previously.
Tree/shrub abundance (1 study): The same study reported that overall tree biomass was greatest in plots logged at the lowest intensity five years previously. In contrast, overall shrub biomass was greatest in plots logged at medium intensity.
Individual species abundance (1 study): The same study reported that the density of the two most common tree species typically declined with increasing logging intensity.

VEGETATION STRUCTURE

Diameter/perimeter/area (1 study): One replicated, controlled study in a freshwater swamp in China reported that the diameter of the two most common tree species typically declined with increasing logging intensity.
Basal area (1 study): The same study reported that the basal area of the two most common tree species typically declined with increasing logging intensity.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

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
Referenced paper
Mu C., Lu H., Wang B., Bao X. & Cui W. (2013) Short-term effects of harvesting on carbon storage of boreal Larix gmelinii–Carex schmidtii forested wetlands in Daxing’anling, northeast China. Forest Ecology and Management, 293, 140-148.

Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Use low-impact methods to harvest vegetation: brackish/saline swamps Action Link	No evidence found (no assessment)	0	Synopsis Link
Reduce intensity of vegetation harvest: freshwater marshes Action Link	No evidence found (no assessment)	0	Synopsis Link
Change season/timing of vegetation harvest: freshwater marshes Action Link	Likely to be beneficial	3	Synopsis Link