David D. Reed

Modeling canopy structure and heterogeneity across scales: From crowns to canopy

Abstract Canopy studies have been limited in ecological investigations due to problems of canopy accessibility, and the lack of efficient sampling and modeling methods. The primary objective of this study was to develop an efficient modeling approach to describe the 3-dimensional, hierarchical structure of individual crown shells within stands and corresponding canopy patches. Crown shells were modeled based on crown ratio, maximum cardinal radius, vertical position, and shape. Canopies were represented by adding unique crowns to simulated point patterns of trees of known aggregation as measured by Pielous index of nonrandomness. Canopy patches were delineated at multiple horizontal and vertical scales using the ARC INFO geographic information system (GIS). The patterns of canopy patches are clearly variable and scale dependent. Canopy patterns become more diverse at broader horizontal scales, and change greatly from the lower to the upper canopies. The modeling approach used in this study has general utility in characterizing 3-dimensional canopies of many types of forests.

Historical Changes in the Forests of the Luce District of the Upper Peninsula of Michigan

Abstract General Land Office (GLO) survey notes (1840–1856), current land cover generated from Landsat TM Imagery (1991) and the Forest Inventory and Analysis plots (1991–1992, US Forest Service) were used to examine changes in forests of the Luce District in Upper Michigan over the past 150 y. Historical changes in two subdistricts, Grand Marais and Seney, were also analyzed. Interpretation of GLO notes showed that the presettlement landscape was a mixed conifer matrix (39% of total area), interspersed primarily with northern hardwoods (29%), wetlands (14%) and fire-susceptible pinelands (13%). Estimates of pre-European settlement stand density ranged from 81 trees/ha in open lands to 408 trees/ha in northern white cedar stands (Thuja occidentalis), and estimates of basal area ranged from 3.5 m2/ha in wetlands to 27.7 m2/ha in mixed hardwood/conifer forests. Notable changes in species composition over the last 150 y are the increase of red maple (Acer rubrum; +14%) and the decline of tamarack (Larix laricina; −11%), hemlock (Tsuga canadensis; −7%), white pine (Pinus strobus; −6%), beech (Fagus grandifolia; −5%) and yellow birch (Betula alleghaniensis; −5%). Contrasts between the two subdistricts, Grand Marais and Seney, reflect the influence of the integration of climate, physiography and disturbance regime. Overall presettlement vs. present-day tree diameter distributions differed between the two time periods. Differences in the diameter distributions among individual tree species are related to their growth rates and life expectancies. The diameter distributions of short-lived species are similar between the two time periods. Most species have diameter distributions with more small trees today than in presettlement forests, especially long-lived taxa such as hemlock and white pine.

Total aboveground biomass and net dry matter accumulation by plant component in young Eucalyptus globulus in response to irrigation

A system of equations describing total aboveground biomass, the proportion of total aboveground biomass accumulated by different plant components, and instantaneous net dry matter accumulation fraction is developed as a function of tree diameter, height, and the growth rates of diameter and height. This system is utilized in the analysis of a Eucalyptus globulus fertilization/irrigation experiment in central Portugal. The data were from the period prior to competition-induced mortality in the stands, but previous analyses had reported apparent changes in tree growth rates due to intraspecific competition in the experimental stands. The irrigation treatments affected the relationship between tree dimensions and total aboveground biomass as well as the accumulation of biomass by different aboveground plant components (p≤0.05). There were no differences in these relationships due to fertilization (p=0.05), in spite of previously reported increases in biomass production in response to fertilization. Even though irrigation affects dimensional biomass relationships in E. globulus, analyses demonstrate that previously reported differences in biomass production and accumulation by the various aboveground plant components are, to a much greater extent, due to changes in the growth rates of diameter and height among the treatments rather than to the changes in structural relationships due to the experimental treatments.

Changes in microclimate after stand conversion in two northern hardwood stands

Abstract Changes in air temperature, soil temperature, and soil moisture were monitored for 5 years in two northern hardwood stands after whole-tree harvesting and conversion to red pine ( Pinus resinosa Ait.) plantations. Soil temperatures at a depth of 5 cm and maximum air temperatures 2 m above the soil surface were increased 5–25% after stand conversion. Soil moisture content at a depth of 5 cm was increased by 10–20% in one stand but not in the other. Differences in stand, soil, and topographical characteristics between the two stands did not have any apparent effect on the magnitude of air or soil temperature changes after stand conversion. However, higher initial stand density and soil water holding capacity appeared to be related to increased soil moisture content at one of the sites. The increased soil temperatures after conversion were not only a result of the removal of the northern hardwood canopy but also the removal and redistribution of the forest floor caused by whole-tree harvesting. Five years after stand conversion air temperature, soil temperature, and soil moisture showed no evidence of recovering from initial post-harvest levels.

A process-based growth model for young red pine

Abstract A carbon-balance, process-based growth model was developed to simulate the growth of young red pine ( Pinus resinosa Ait.). The dry weights of current, 1-year-old, 3-year-old needless, stems and branches, and roots of individual trees were considered as state variables. The hourly rate of photosynthesis was calculated with solar radiation, air temperature, leaf water potential, and leaf age as driving variables by assuming that the needles experience the same incident light density. Maintenance respiration rate was assumed to be a function of surrounding temperature. The seasonal allocation of assimilates to each compartment was determined by the activity of each compartment and was regulated by soilwater potential. The translocation of carbohydrate reserves, litter fall, and root turnover were incorporated in the model. The simulated results fit well with observed values from three plantations in the central Upper Peninsula of Michigan.

Soil factors related to dissolved organic carbon concentrations in a Black Spruce Swamp, Michigan

Controls on dissolved organic carbon (DOC) concentrations were examined through field and laboratory measurements of a Typic Haplaquod in Michigan. Average DOC concentration in the soil solution at 30-cm depth was 32 mg/L, and groundwater DOC concentration at 2-m depth was 18 mg/L. Oxidation-reduction (redox) potentials measured in the upper 30 cm of soil ranged from −220 mV to +500 mV, indicating the presence of both reduced and oxidized conditions at the site. Mineral soil organic carbon (SOC) ranged from 0.47% in the Bg horizon to 2.70% in the Bhs horizon. Citrate-dithionite extractable iron (Fe c/d ) ranged from 5.9 μg/g in the E horizon to 85.0 μg/g in the Bhs horizon

Effects of genotype on the response of Populus tremuloides michx. To ozone and nitrogen deposition

Elevated O3 concentrations and N deposition levels co -occur in much of eastern United States. However, very little is known about their combined effects on tree growth. The effects of three O3 treatments: charcoal-filtered air, non-filtered air and O3, added at the rate of 80 ppb for 6 hr d−1 3 d per week), four N deposition levels (0, 10, 20 and 40 kg ha−1 yr−1), and their interactions on growth of two Populus tremuloides clones in open-top chambers at two sites 600 km apart in Michigan were examined. Our results revealed a highly significant fertilization effect of the N treatments, even at the 10 kg ha−1 yr−1 rate. Ozone alone induced foliar injury, but not significant growth reductions. There was an indication that O3 decreased growth at the O N level, but this decrease was reversed in all N treatments by the N fertilization effect. Further study is needed to more fully understand the combined effects of N deposition and O3.

Models of potential height and diameter for Eucalyptus globulus in Portugal

When modeling tree dimensions, it is common in many forest growth models to first predict the potential diameter or height in the absence of resource limitation, and then to modify this downward using functions reflecting the impact of various limiting resources on growth. Most of these models, however, were not parameterized using observations of true potential growth. This study utilizes data from a field trial of Eucalyptus globulus in central Portugal to parameterize models of potential height and diameter of E. globulus in the absence of growth reduction due to moisture or nutrient limitation. The resulting models represent tree height and diameter as functions of a single variable, the growing degree days (5 °C basis) accumulated since the date of planting.

Decomposition of pine-litter organic matter and chemical properties of upper soil layers: transect studies

Abstract The relationship between Scots pine litter decomposition rate and some chemical properties of the upper soil layers and litter (contents of iron, manganese, zinc, copper, lead, mercury, nickel and chromium) was determined. For the metal content in the organic-mineral horizon of soils, the strongest correlation was between needle decomposition and copper (r=0.90), zinc (r=0.90), iron (r=0.83), and nickel (r=0.85) concentrations. For the metal content of litter, the strongest correlations were between needle decomposition and nickel (r=0.89), iron (r=0.83), zinc (r=0.80), and lead (r=0.82) concentrations. For mixed-litter decomposition and litter heavy metal concentrations, the highest correlations were with nickel (r=0.72), iron (r=0.71), zinc (r=0.66), and lead (r=0.68). There were no significant correlations between the rate of decomposition of wood or cones and the litter concentration of metals other than chromium. In some cases, the correlations between decomposition rate and metal concentration were positive. Two out of six significant correlations between needle decomposition and the concentration of metals in litter were positive. For mixed litter decomposition, the five significant correlations included two that were positive. In both cases, decomposition responded positively to the presence of iron and lead. Comparing decomposition rates with the level of soil metal content, all five significant correlations with needle decomposition were positive; for mixed-litter decomposition, only one significant correlation was positive.

Ecological implications of projected climate change scenarios in forest ecosystems in northern Michigan, USA

Changes in seasonal temperature and precipitation, as predicted by several global climate models, were utilized together with a stochastic daily weather stimulation model to evaluate the ecological impacts of projected global climate change scenarios on temperate forest ecosystems in northern Michigan, USA. The model simulated the impacts of these projected changes on ecologically significant weather variables, such as the length of the frost-free period, average growing season temperature, average growing season degree days (4.4° C basis), summer precipitation, potential evaporation during the growing season, and the ratio of precipitation to potential evaporation during July and August. The results indicate that even the lower range of predicted climate changes could lead to ecologically and commercially significant changes in the composition and productivity of these forests. Of particular concern is the possibility of climatically induced regional decline episodes for a number of important commercial species in the northern temperate forests of central North America.