Reduce intensity of vegetation harvest: freshwater swamps

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Source countries

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

  1. A replicated, controlled study in 2006–2011 in a forested wetland in northeast China (1 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
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?

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Marsh and Swamp Conservation

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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