Long-term management impacts on carbon storage in Lake States forests

We examined carbon storage following 50+ years of forest management in two long-term silvicultural studies in red pine and northern hardwood ecosystems of North America’s Great Lakes region. The studies contrasted various thinning intensities (red pine) or selection cuttings, shelterwoods, and diameter-limit cuttings (northern hardwoods) to unmanaged controls of similar ages, providing a unique opportunity to evaluate long-term management impacts on carbon pools in two major North American forest types. Management resulted in total ecosystem carbon pools of 130-137 Mg ha⁻¹ in thinned red pine and 96-177 Mg ha⁻¹ in managed northern hardwoods compared to 195 Mg ha⁻¹ in unmanaged red pine and 224 Mg ha⁻¹ in unmanaged northern hardwoods. Managed stands had smaller tree and deadwood pools than unmanaged stands in both ecosystems, but management had limited impacts on understory, forest floor, and soil carbon pools. Total carbon storage and storage in individual pools varied little across thinning intensities in red pine. In northern hardwoods, selection cuttings stored more carbon than the diameter-limit treatment, and selection cuttings generally had larger tree carbon pools than the shelterwood or diameter-limit treatments. The proportion of total ecosystem carbon stored in mineral soil tended to increase with increasing treatment intensity in both ecosystems, while the proportion of total ecosystem carbon stored in the tree layer typically decreased with increasing treatment intensity. When carbon storage in harvested wood products was added to total ecosystem carbon, selection cuttings and unmanaged stands stored similar levels of carbon in northern hardwoods, but carbon storage in unmanaged stands was higher than that of thinned stands for red pine even after adding harvested wood product carbon to total ecosystem carbon. Our results indicate long-term management decreased on-site carbon storage in red pine and northern hardwood ecosystems, but thinning intensity had little impact on carbon storage in red pine while increasing management intensity greatly reduced carbon storage in northern hardwoods. These findings suggest thinning to produce different stand structures would have limited impacts on carbon storage in red pine, but selection cuttings likely offer the best carbon management options in northern hardwoods.     

Effects of uneven-aged silviculture on the stand structure,species composition,and economic returns of loblolly pine stands

Uneven-aged silviculture in loblolly pine (Pinus taeda L.) stands has many economic and ecological benefits. Here, the consequences of various uneven-aged management regimes are predicted with the SouthPro simulator. Results indicate that target distributions for pines with residual merchantable basal areas of ≈12.5 m² ha⁻¹, maximum diameters of ca. 40 cm, and q-ratios of 1.2–1.25 for 2.5 cm DBH classes are likely to provide high economic returns on good sites when combined with hardwood control. Increasing this maximum diameter would enhance tree-size diversity, but reduce sawtimber production and profits. Retaining a hardwood component with 1.15–2.3 m² ha⁻¹ of basal area could enhance tree-species diversity, but this too would result in moderate reductions in income. Insisting on maximizing tree-size diversity or tree-species diversity among softwoods, soft hardwood, and hard hardwoods would be quite costly in terms of lost income and production. Results also illustrate how short-term economic incentives can lead to high-grading practices, despite substantial reductions in stand productivity and net returns in the long term.     

The effect of weed control and fertilization on survival and growth of four pine species in the Virginia Piedmont

The growth response of loblolly pine (Pinus taeda L.), shortleaf pine (Pinus echinata Mill.), Virginia pine (Pinus virginiana Mill.), and white pine (Pinus strobus L.) to weed control and fertilization in the Piedmont of Virginia was assessed. Four different silvicultural treatments were evaluated: (1) check (no treatment); (2) weed control; (3) fertilization; (4) weed control plus fertilization. The weed control treatment included a series of herbicide and mechanical treatments to eliminate competing hardwoods. The fertilizer treatments added N, P, K, and S. Survival and growth was measured annually through age 5. There were significant differences in survival and growth among species. Survival was greatest for loblolly pine, lower in shortleaf and Virginia pine, and lowest in white pine. Fertilization without controlling the competing hardwoods decreased survival in all planted pines due to the increased hardwood competition. Loblolly pine was tallest through the 5-year period, shortleaf and Virginia pine were shorter and white pine was shortest. Silvicultural treatments had no impact on tree height but significantly affected DBH. Weed control increased DBH while fertilization did not. When applied in combination with weed control, there was no additional increase in growth of the pines due to fertilization beyond that from weed control only. Fertilization stimulated the growth of the competing hardwoods which were significantly taller in the fertilized plots.     

Caribbean pine in an agroforestry system on the Atherton Tableland in north east Australia

A trial demonstrating an establishment and maintenance technique forPinus caribaea var hondurensis in an agroforestry land use system on the Atherton Tableland, north east Australia, is described. The establishment of the tree component involves mechanical cultivation and the application of herbicides which in combination are technically feasible and acceptable to a landholder who wishes to integrate pine trees and pasture grasses. The cost of establishment and maintenance of the pines up to age 39 months was calculated at $A809 ha^?1 (1986 values). This includes the cost of thinning. The sale of some thinnings for Christmas trees realised a net profit of $A564 from 300 trees ($A188 ha^?1). At age 38 months the stand had a stocking of 254 trees ha^?1, a mean height of 6 m and a mean diameter at breast height of 12.1 cm. The growth compares favourably with other plantation grownPinus caribaea var hondurensis on the Atherton Tableland.     

A comparison of lidar,radar, and field measurements of canopy height in pine and hardwood forests of southeastern North America

Forest canopy height is essential information for many forest management activities and is a critical parameter in models of ecosystem processes. Several methods are available to measure canopy height from single-tree to regional and global scales, but the methods vary widely in their sensitivities, leading to different height estimates even for identical stands. We compare four technologies for estimating canopy height in pine and hardwood forests of the Piedmont region of North Carolina, USA: (1) digital elevation data from the global Shuttle Radar Topography Mission (SRTM) C-band radar interferometry, (2) X- and P-band radar interferometry from the recently developed airborne Geographic Synthetic Aperture Radar (GeoSAR) sensor, (3) small footprint lidar measurements (in pine only), and (4) field measurements acquired by in situ forest mensuration. Differences between measurements were smaller in pine than in hardwood forests, with biases ranging from 5.13 to 12.17 m in pine (1.60–13.77 m for lidar) compared to 6.60–15.28 m in hardwoods and RMSE from 8.40 to 14.21 m in pine (4.73–14.92 m for lidar) compared to 9.54–16.84 in hardwood. GeoSAR measurements of canopy height were among the most comparable measurements overall and showed potential for successful calibration, with R² = 0.87 in pine canopies and R² = 0.38 in hardwood canopies from simple linear regression. An improved calibration based on differential canopy penetration is presented and applied to SRTM measurements, resulting in canopy height estimates in pine forests with RMSE and standard error <4.00 m. Each of the remotely sensed methods studied produces reasonable and consistent depictions of canopy height that can be compared with data of similar provenance, but due to differences in underlying sensitivities between the methods, comparisons between measurements from various sources require cross-calibration and will be most useful at broad scales.     

Conversion of conifer plantations to native hardwoods: influences of overstory and fertilization on artificial regeneration

Forest tree species in the eastern US such as American chestnut (Castanea dentata (Marsh.) Borkh) and oaks (Quercus spp.) have been negatively impacted by forest changes over the past century. Many mature, introduced pine (Pinus spp.) plantations exist in the Midwest US following establishment 50–60 years ago yet have little economic and ecological value. As oak and chestnut have similar site preferences to pines, these stands may be ideal sites for hardwood restoration plantings. We sought to determine optimal management strategies for converting pine plantations by manipulating their canopies. We underplanted hybrid American chestnut and northern red oak (Quercus rubra L.) seedlings into three canopy treatments (control, shelterwood, clearcut) and included an open field treatment. For each of two growing seasons, 0, 30, or 60 g 19N–6P–12K of controlled-release fertilizer (CRF) were also applied to seedlings. Soil chemical parameters and leaf nutrients were analyzed throughout the study. Chestnut and oak seedlings had significantly greater height after two growing seasons in the clearcut and shelterwood than the control and open field, and chestnut had significantly greater diameter as well. Chestnut height and RCD growth were threefold that of oak after two growing seasons. In general, fertilization increased seedling growth more in the clearcut and open field than shelterwood and control for both species. Soils had significantly higher pH, K, and S in the open field than in pine stands. Results suggest that pine plantations may serve as target sites for restoration of these hardwood species. Shelterwoods and clearcuts are both favorable conversion options for oak and chestnut, and addition of CRF may augment further growth increase, especially in open environments.     

Atmospheric nutrient inputs to three forest types in East Texas

The effect of forest type on atmospheric nutrient inputs to the forest ecosystem was measured for individual storm events for 1 year in three East Texas forest types: beechmagnolia, pine-mixed hardwoods and loblolly pine plantation. Total annual bulk precipitation inputs (kg/ha) for Ca, Mg, N, K and Na were, respectively: 5.0, 1.1, 4.1, 3.3 and 9.9. Total througfall inputs were increased by forest type, but the magnitude differed with each nutrient. Over $\text{3}\text{4}$ of the total K and $\text{1}\text{2}$ the total Mg throughfall input were due to the forest canopy. However $\text{2}\text{3}$ of the Ca and most of the Na throughfall input resulted from bulk precipitation. Although stemflow nutrient concentrations (ppm) were higher than throughfall and bulk precipitation, total annual stemflow nutrient inputs were only a minor component of the loblolly pine plantation ecosystem.     

Comparing morphology and physiology of southeastern US <Emphasis Type="Italic">Pinus</Emphasis> seedlings: implications for adaptation to surface fire regimes

Key message

The suite of traits expressed as seedlings by coastal and mountain longleaf pine and south Florida slash pine suggest they can survive fire in the seedling stage. In contrast, loblolly pine and typical slash pine tolerate fire when mature but do not exhibit traits that allow them to survive fire when young, representing a different strategy for survival in frequently burned communities.

Context

Fire is an important driver in the distribution and abundance of southern US pine species, and seedling fire tolerance often determines individual survival under frequent fire regimes.

Aims

We investigated seedling growth, biomass allocation, needle distribution, bark thickness, and total non-structural carbohydrate (TNC) storage in taproots and related them to the expression of fire-tolerance for five species or types, including loblolly pine (Pinus taeda L.), two longleaf pine (P. palustris Mill.) types representing two distinct ecological communities (coastal and mountain) and two slash pine (P. elliottii Englem.) varieties.

Methods

We analyzed the relationship of seedling growth, biomass characteristics, and total non-structural carbohydrate storage between species by using analysis of variance.

Results

Both coastal and mountain longleaf pines had thick bark, long, densely arranged needles, and a grass-stage. South Florida slash pine shared the same suite of traits but, contrary to previous reports, displayed reduced height growth rather than a grass-stage. In contrast, loblolly pine and typical slash pine had faster height growth, more branching, lower needle density, and thinner bark. Both longleaf pines and south Florida slash pine also had higher TNC storage in taproots than either loblolly or typical slash pines.

Conclusion

The relative strength of expression of these fire-adaptation traits among the five species types generally matches the fire-return intervals associated with each species’ habitat, suggesting the importance of fire regimes in determining the distribution and abundance of the studied species.