Multimodel simulations of forest harvesting effects on long‐term productivity and CN cycling in aspen forests.

The effects of forest management on soil carbon (C) and nitrogen (N) dynamics vary by harvest type and species. We simulated long-term effects of bole-only harvesting of aspen (Populus tremuloides) on stand productivity and interaction of CN cycles with a multiple model approach. Five models, Biome-BGC, CENTURY, FORECAST, LANDIS-II with Century-based soil dynamics, and PnET-CN, were run for 350 yr with seven harvesting events on nutrient-poor, sandy soils representing northwestern Wisconsin, United States.

Estimating the carbon budget and maximizing future carbon uptake for a temperate forest region in the U.S.

Background: Forests of the Midwest U.S. provide numerous ecosystem services.

Ecosystem warming does not affect photosynthesis or aboveground autotrophic respiration for boreal black spruce.

We measured light-saturated photosynthesis (A(net)), foliage respiration (R(fol)) and stem respiration (R(stem)) of black spruce (Picea mariana (Mill.) B.S.

Fire as the dominant driver of central Canadian boreal forest carbon balance.

Changes in climate, atmospheric carbon dioxide concentration and fire regimes have been occurring for decades in the global boreal forest, with future climate change likely to increase fire frequency--the primary disturbance agent in most boreal forests. Previous attempts to assess quantitatively the effect of changing environmental conditions on the net boreal forest carbon balance have not taken into account the competition between different vegetation types on a large scale. Here we use a process model with three competing vascular and non-vascular vegetation types to examine the effects of climate, carbon dioxide concentrations and fire disturbance on net biome production, net primary production and vegetation dominance in 100 Mha of Canadian boreal forest.

Measurement of CO2 exchange between Boreal forest and the atmosphere.

The Boreal forest is the world's second largest forested biome occupying the circumpolar region between 50 degrees N and 70 degrees N. This heterogeneous biome stores about 25% of all terrestrial carbon. We have reviewed EC measurements of CO2 exchange between the atmosphere and Boreal forests, and assessed progress in understanding the controlling processes.

Improved simulation of poorly drained forests using Biome-BGC.

Forested wetlands and peatlands are important in boreal and terrestrial biogeochemical cycling, but most general-purpose forest process models are designed and parameterized for upland systems. We describe changes made to Biome-BGC, an ecophysiological process model, that improve its ability to simulate poorly drained forests. Model changes allowed for: (1) lateral water inflow from a surrounding watershed, and variable surface and subsurface drainage; (2) adverse effects of anoxic soil on decomposition and nutrient mineralization; (3) closure of leaf stomata in flooded soils; and (4) growth of nonvascular plants (i.

Estimation of stand-level leaf area for boreal bryophytes.

Bryophytes dominate the carbon and nitrogen cycling of many poorly drained terrestrial ecosystems and are important in the vegetation-atmosphere exchange of carbon and water, yet few studies have estimated their leaf area at the stand scale. This study quantified the bryophyte-specific leaf area (SLA) and leaf area index (LAI) in a group of different-aged boreal forest stands in well and poorly drained soils. Species-specific SLA (for three feather mosses, four Sphagnum spp.

Reimplementation of the Biome-BGC model to simulate successional change.

Biogeochemical process models are increasingly employed to simulate current and future forest dynamics, but most simulate only a single canopy type. This limitation means that mixed stands, canopy succession and understory dynamics cannot be modeled, severe handicaps in many forests. The goals of this study were to develop a version of Biome-BGC that supported multiple, interacting vegetation types, and to assess its performance and limitations by comparing modeled results to published data from a 150-year boreal black spruce (Picea mariana (Mill.

Contribution of root respiration to soil surface CO2 flux in a boreal black spruce chronosequence.

We quantified the contributions of root respiration (RC) and heterotrophic respiration to soil surface CO2 flux (RS) by comparing trenched and untrenched plots in well-drained and poorly drained stands of a black spruce (Picea mariana (Mill.) BSP) fire chronosequence in northern Manitoba, Canada. Our objectives were to: (1) test different equations for modeling RS as a function of soil temperature; and (2) model annual RS and RC for the chronosequence from continuous soil temperature measurements.

Characterization of radiation regimes in nonrandom forest canopies: theory, measurements, and a simplified modeling approach.

We used field measurements and Monte Carlo simulations of canopy gap-size distribution and gap fraction to examine how beam radiation interacts with clumped boreal forest canopies of aspen (Populus tremuloides Michx.), black spruce (Picea mariana (Mill.) B.

Environmental controls on carbon dioxide flux from black spruce coarse woody debris.

Carbon dioxide flux from coarse woody debris (CWD) is an important source of CO in forests with moderate to large amounts of CWD. A process-based understanding of environmental controls on CWD CO flux (R ) is needed to accurately model carbon exchange between forests and the atmosphere. The objectives of this study were to: (1) use a laboratory incubation factorial experiment to quantify the effect of temperature (T ), water content (W ), decay status, and their interactions on R for black spruce [Picea mariana (Mill.

Environmental controls on ground cover species composition and productivity in a boreal black spruce forest.

Boreal black spruce forests typically have a dense ground cover of bryophytes. The two main bryophyte groups in boreal black spruce forests, feathermoss and Sphagnum, have ecophysiological characteristics that influence the biogeochemical cycles of black spruce forests differently. The objective of this study was to examine the environmental controls of ground cover composition and net primary production (NPP) of feathermoss and Sphagnum in a boreal black spruce forest in central Saskatchewan.

Foliar carbon isotope discrimination in Larix species and sympatric evergreen conifers: a global comparison.

Larches (Larix spp.), deciduous conifers, occur in the northern hemisphere in cold-temperate and boreal climates - an environment normally thought to favor evergreen tree species. We compare foliar carbon isotope discrimination (Δ), instantaneous water use efficiency, total foliar nitrogen concentration, and specific leaf area (for a subset of sites) between Larix spp.

Root mass, net primary production and turnover in aspen, jack pine and black spruce forests in Saskatchewan and Manitoba, Canada.

Root biomass, net primary production and turnover were studied in aspen, jack pine and black spruce forests in two contrasting climates. The climate of the Southern Study Area (SSA) near Prince Albert, Saskatchewan is warmer and drier in the summer and milder in the winter than the Northern Study Area (NSA) near Thompson, Manitoba, Canada. Ingrowth soil cores and minirhizotrons were used to quantify fine root net primary production (NPPFR).

Woody tissue maintenance respiration of four conifers in contrasting climates.

We estimate maintenance respiration for boles of four temperate conifers (ponderosa pine, western hemlock, red pine, and slash pine) from CO efflux measurements in autumn, when construction respiration is low or negligible. Maintenance respiration of stems was linearly related to sapwood volume for all species; at 10°C, respiration per unit sapwood volume ranged from 4.8 to 8.

FOREST-BGC, A general model of forest ecosystem processes for regional applications. II. Dynamic carbon allocation and nitrogen budgets.

A new version of the ecosystem process model FOREST-BGC is presented that uses stand water and nitrogen limitations to alter the leaf/root/stem carbon allocation fraction dynamically at each annual iteration. Water deficit is defined by integrating a daily soil water deficit fraction annually. Current nitrogen limitation is defined relative to a hypothetical optimum foliar N pool, computed as maximum leaf area index multiplied by maximum leaf nitrogen concentration.

Estimation of leaf area index in fourteen southern Wisconsin forest stands using a portable radiometer.

Projected leaf area index (LAI) and Beer-Lambert Law extinction coefficients (K) were estimated for 28-year-old Picea abies (L.) Karst., Larix decidua Mill.

Effects of nutrient amendments on fine root biomass in a primary successional forest in Hawai'i.

We determined the effect of fertilization treatments (control (C), complete nutrient amendment without nitrogen (PT), nitrogen only (N) and a complete nutrient amendment (NPT)) on fine root biomass in a tropical montane forest in Hawai'i. Fertilization significantly decreased root biomass; live fine root mass (<2 mm diameter) for the C, PT, N and NPT treatments were 335, 145, 110 and 105 g·m, respectively. Nutrient availability appears to control fine root mass in this primary successional forest.