Canadian intersite decomposition experiment (CIDET)

The Canadian Intersite Decomposition Experiment is a cooperative study of 20 researchers from the Canadian Forest Service, universities and provincial ministries investigating the long-term rates of litter decomposition and nutrient mineralization over a broad range of forested ecoclimatic regions in Canada.

• Introduction
• Research results: Measures of litter quality
• Research results: Comparison of 3rd-year results and model predictions
• Research results: Controls on litter decomposition
• Research results: Effects of climate change on litter decomposition
• CIDET Publications and Presentations
• CIDET working group

---

Introduction

Increasing concern is being expressed on the effects of the predicted changes in climate on forest carbon budgets and how forest practices should be adapted to cope with these changes. Canadian forests contain large amounts of carbon stored in trees, soils and decaying plant litter and may prove especially sensitive to climate changes, specifically global warming, predicted for northern latitudes. Changes to the forested land area and the balance between the uptake of carbon from the atmosphere by plants through photosythesis and release of carbon through fire, respiration, and decay, would affect levels of atmospheric carbon dioxide. Carbon dioxide is an important greenhouse gas and increases in its level have been linked to global warming. Warmer temperatures would increase decay rates, releasing carbon stored in soils and litter and thus have the potential to accelerate the rise in atmospheric carbon dioxide levels.

Currently, several projects are underway to quantitatively model the current and potential changes in the carbon budgets of Canadian forests to climate change. Information is limited for many of the processes being modeled, particularly those related to soil processes. Of major importance is the rate of litter decomposition which is lacking in extent and length for most forest ecosystems. To overcome this data deficiency a group of researchers from across Canada have been assembled to conduct a long-term decomposition experiment.

Objectives

The Canadian Intersite Decomposition Experiment (CIDET), is a cooperative study of 20 researchers from the Canadian Forest Service, universities and provincial ministries investigating the long-term rates of litter decomposition and nutrient mineralization over a broad range of forested ecoclimatic regions in Canada.

The experiment has the following objectives:

1. Provide data on the long-term rates of litter decomposition and nutrient mineralization for a range of forested ecoclimatic regions in Canada
2. Examine the role substrate quality and climate have on long-term decomposition rates
3. Examine the relative importance of site factors and microclimate on decay rates
4. Test the influence that site moisture regimes have on decay rates
5. Test specific hypotheses on the patterns of litter decay

Experimental Design

The study established in 1992, involves the preparation and placement of close to 11,000 litterbags comprised of 10 sets of 12 litter types (Table 1) in each of four replicate plots at each of 21 sites. Each year for ten years, one set of bags is removed per plot and analyzed for weight for weight loss and carbon, nitrogen and phosphorous content.

Relationships between decay rates, substrate quality, and climate will be established using regression techniques. Information on an array of site factors, soils and, where possible, microclimate from each site will be used in a multivariate analysis to test for site and microclimate effects. Moisture effects will be studied by comparing decay rates at two spatial levels:

1. at the macrosite level by comparing decay rates in the 3 paired lowand- wetland boreal forest sites
2. at the microsite level by comparing effects of placement, above- or below ground, of wood blocks

Table 1: Litter type and species used in CIDET

Litter type and species used in CIDET

Code *	Common Name	Binomial	Collector
Leaves
Dpt	Trembling Aspen	Populus tremuloides	Visser
Dba	American Beech	Fagus grandifolia	Fyles
Cdc	Douglas-fir	Pseudotsuga menziesii	Trofymow
Csb	Black spruce	Picea mariana	Titus
Cll	Tamarack	Larix laricina	Zoltai
Fbf	Bracken fern	Pteridium aquilinum	Duchesne
Gfh	Plains rough fescue	Festuca hallii	Monreal
Ctp	Western redcedar	Thuja plicata	Prescott
Cpj	Jack pine	Pinus banksiana	Weber
Dbw	White birch	Betula papyrifera	Titus
Wood
Whw	Western hemlock	Tsuga heterophylla	Trofymow

---