Upland Conifer Forest Research Articles

Refuge-yeah or refuge-nah? Predicting locations of forest resistance and recruitment in a fiery world.

Climate warming, land use change, and altered fire regimes are driving ecological transformations that can have critical effects on Earth's biota. Fire refugia-locations that are burned less frequently or severely than their surroundings-may act as sites of relative stability during this period of rapid change by being resistant to fire and supporting post-fire recovery in adjacent areas. Because of their value to forest ecosystem persistence, there is an urgent need to anticipate where refugia are most likely to be found and where they align with environmental conditions that support post-fire tree recruitment. Using biophysical predictors and patterns of burn severity from 1180 recent fire events, we mapped the locations of potential fire refugia across upland conifer forests in the southwestern United States (US) (99,428 km2 of forest area), a region that is highly vulnerable to fire-driven transformation. We found that low pre-fire forest cover, flat slopes or topographic concavities, moderate weather conditions, spring-season burning, and areas affected by low- to moderate-severity fire within the previous 15 years were most commonly associated with refugia. Based on current (i.e., 2021) conditions, we predicted that 67.6% and 18.1% of conifer forests in our study area would contain refugia under moderate and extreme fire weather, respectively. However, potential refugia were 36.4% (moderate weather) and 31.2% (extreme weather) more common across forests that experienced recent fires, supporting the increased use of prescribed and resource objective fires during moderate weather conditions to promote fire-resistant landscapes. When overlaid with models of tree recruitment, 23.2% (moderate weather) and 6.4% (extreme weather) of forests were classified as refugia with a high potential to support post-fire recruitment in the surrounding landscape. These locations may be disproportionately valuable for ecosystem sustainability, providing habitat for fire-sensitive species and maintaining forest persistence in an increasingly fire-prone world.

Microsite Habitat, Species Associations, and Habitat Suitability Model of a Globally Imperiled Shrub

Miller's witch-alder (Fothergilla milleri, Hamamelidaceae) is a newly described globally imperiled shrub that is known from disjunct populations in coastal Alabama, the panhandle of Florida, and one location in Georgia. Little is currently known about the natural history or ecology of the species. We conducted inventories of three populations of F. milleri in Alabama and Florida. A total of 3060 ramets were found; 45% were in one subpopulation ≤0.5 ha in area and 79% were in one population within an area of 4.5 ha. Low ramet counts in few locations makes the species particularly vulnerable to extinction due to stochastic events. Also, all seed capsules found within the surveys were infected by an aphid, which is possibly preventing sexual reproduction within the populations. Microsite habitat data indicated F. milleri grows in a unique transitional habitat between upland conifer forest and wetlands. The sites where extant populations of F. milleri inhabit tend to have acidic and well-drained soils with a high sand content. Further, many populations were under thick midstory vegetation. Thus, fire or other forms of removal may be needed to release those subpopulations before they may become shaded out. Lastly, a habitat suitability model was developed to better facilitate conservation efforts. However, only 0.5% of the study area was within the highest level of suitability. Fothergilla milleri is facing multiple threats that could lead to its extirpation from the wild, and direct and intense conservation action may be necessary to ensure F. milleri remains on the landscape.

A NEW SPECIES OF JUNIPEROXYLON FROM THE EARLY MIOCENE OF NORTHWESTERN TURKEY

Many different Cupressaceae species were described from the early Miocene of Turkey. Particularly, Glyptostroboxylon Conventz, 1885 and Taxodioxylon Hartig, 1848 from Cupressaceae are the most common genera. With the present study, a new fossil Juniperoxylon (Houlbert, 1910) Kräusel, 1949 species from early Miocene of north-western Turkey was described as Juniperoxylon acarcaea Akkemik sp. nov. The new species has diffuse and zonate axial parenchyma, 2-3 (5) cupressoid pits per cross-field, sometimes presence of crassulae, uniseriate to biseriate, opposite, frequent, contiguous and sometimes spaced radial wall pits, even uniseriate and irregularly or alternately biseriate pits on tangential walls, horizontal walls of rays smooth and/or pitted, ray width uniseriate and rarely partly biseriate, and end walls of axial parenchyma nodular and smooth. The new species is the first Juniperoxylon species description from Turkey. According to the vegetation units (VU), this fossil species may indicate the forest was likely well-drained lowland and/or upland conifer forest (VU7).

Comparison and validation of three versions of a forest wind risk model

Predicting the probability of wind damage in both natural and managed forests is important for understanding forest ecosystem functioning, the environmental impact of storms and for forest risk management. We undertook a thorough validation of three versions of the hybrid-mechanistic wind risk model, ForestGALES, and a statistical logistic regression model, against observed damage in a Scottish upland conifer forest following a major storm. Statistical analysis demonstrated that increasing tree height and local wind speed during the storm were the main factors associated with increased damage levels. All models provided acceptable discrimination between damaged and undamaged forest stands but there were trade-offs between the accuracy of the mechanistic models and model bias. The two versions of the mechanistic model with the lowest bias gave very comparable overall results at the forest scale and could form part of a decision support system for managing forest wind damage risk.

Potential Influence of Forest Management on Regional Carbon Stocks: An Assessment of Alternative Scenarios in the Northern Lake States, USA

Abstract Forest management affects stand age. In consideration of the strong link between stand age and carbon cycling, altering harvesting regimes can influence regional carbon stocks and sequestration. Recent research has quantified ecosystem carbon stocks across stand age in upland conifer and aspen–birch forests of the northern Lake States. This study applied those relationships to assess how forest management could influence carbon stocks in these two forest types. US Forest Service Forest Inventory and Analysis data were used to estimate current regional age structure and management intensity and state Gap Analysis Program data were used to assess forest type abundance. Across the region, current carbon stocks in aspen–birch and upland conifer forests are estimated to be 590 and 367 Tg C, respectively. Ceasing timber harvesting over the next century would increase the prevalence of older stands and increase ecosystem carbon stocks by 54% (31% in 50 years) and 30% (19% in 50 years) in aspen–birch and upland conifer forests, respectively. Harvesting aspen–birch stands would change ecosystem carbon stocks by +4% or −13% under annual harvesting of 1 or 2%, respectively. Harvesting upland conifer stands at a rate of 1 or 2% every year would decrease ecosystem carbon by 3 and 18%, respectively. Carbon from harvested material partly compensates for differences in total carbon stocks between no-harvest and harvest scenarios, suggesting a net positive carbon sequestration in all scenarios within 100 years. These results provide insight into the potential maximum impact of forest management on carbon stocks and sequestration in these two forest types.

Soil greenhouse gas and nutrient dynamics in fertilized western Canadian plantation forests

We explored the impacts of fertilization on soil greenhouse gas fluxes and underlying soil nutrient transformations using short-term (up to 7 months) simulated operational fertilization with urea-nitrogen or nitrogen, phosphorus, potassium, and micronutrients in lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.), western hemlock ( Tsuga heterophylla (Raf.) Sarge.), and Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco) forests in British Columbia. Urea appeared to be rapidly mineralized to ammonium, and nitrification (relative to controls) was only observed at the lodgepole pine site and represented only 0.5% of added nitrogen. All sites were small net sinks for atmospheric methane, and fertilization effects, both stimulatory and inhibitory, were short-lived. Across all sites and treatments, soils were as likely to consume as emit nitrous oxide, and among treatment replicates, rates were never significantly different from 0, with the exception of one efflux rate of 1.5 µg·m–2·h–1on the warmest day in the study. We conclude from this pilot study that in acidic, unpolluted (with regard to nitrogen deposition) upland conifer forest soils in western Canada fertilized once or infrequently with urea, ammonium, or a combination of nutrients, the dynamics of soil greenhouse-gas fluxes are generally not disturbed over the short-term, with soils remaining small sinks for atmospheric methane and neutral with regard to flux of nitrous oxide.

Effects of late summer cattle grazing on the diversity of riparian pasture vegetation in an upland conifer forest

Summary 1. Species‐rich grassland is important for biodiversity in upland forests, particularly within riparian zones. Prior to afforestation, the botanical diversity of these grasslands was maintained by domestic stock grazing, but without active management many will revert to coarse, species‐poor grassland and eventually to scrub. The reintroduction of stock grazing is a potential solution to this problem, but has not been tested in upland forests. Here we present results from 9 years of monitoring the effects of cattle grazing on the diversity and composition of riparian pasture vegetation in an upland conifer forest in northern Scotland. 2. There were two treatments, late summer grazing and ungrazed. The average stocking density in the grazed treatment was 2·25–2·5 cows ha−1. The cattle were free to range over the entirety of the 40‐ha experimental site from early August to late September each year. 3. Assessments of plant species richness and abundance were made in 1988 (prior to the commencement of grazing), 1991 and 1997, in three of the main riparian vegetation types. These were ‘Flush’ vegetation associated with calcareous springs, acid Agrostis capillaris–Festuca ovina grassland (‘Grass’), and Juncus effusus rush pasture (‘Juncus’). Assessments were also made of grazing impacts, cattle usage and water table depths. 4. Grazing had a significant effect on plant species richness, which declined in ungrazed plots and remained static in grazed plots over the 1988–97 period. There were no recorded effects of grazing on species abundance, nor on the frequency of rare sedges and herbs of particular conservation importance. Litter cover (dead plant material) was significantly higher in ungrazed plots, which may be a causal factor in declining richness values. 5. Cattle utilized Grass and Flush vegetation to a significantly greater degree than Juncus vegetation, and this appeared to be related to forage availability rather than wetness as represented by water table depth. 6. Cattle grazing is of potential value as a management tool for species‐rich grasslands in upland forests provided that: areas to be grazed are large enough to minimize localized impacts and allow free ranging of the cattle; the economics and practicalities of stock husbandry are considered; the type of grazing management used is linked clearly to management objectives.

Transformation to irregular structure of an upland conifer forest

The Glentress Trial was established by M.L. Anderson in 1952 as a demonstration of transformation to irregular structure of an upland conifer forest in southern Scotland. The trial area (117 ha) is one of the longest continuously-studied forest research areas in Britain. The dominant tree species are Sitka spruce, European larch, Scots pine and Douglas-fir. The most important silvicultural system is group selection, with group size varying from 0.1 to 0.2 ha. Groups are restocked by planting or natural regeneration. Interim results point to the development of an irregular forest structure, although the transformation will not be complete until 2033. The trial demonstrates the value of continuous cover forests in meeting multiple forest management objectives, and is a resource of increasing importance for silviculture education and long-term research. Key words: transformation, irregular structure, uneven-aged management, Sitka spruce, Douglas-fir, long-term silviculture research

Species composition of old-growth and riparian Sitka spruce–western hemlock forests in southeastern Alaska

We studied six 1.2-ha stands, two each of three types of forest: (1) old-growth, riparian floodplain forest, (2) old-growth, upland forest, and (3) 40-year-old, red alder (Alnusrubra Bong.) riparian forest originating after clear-cut logging of floodplain forest. Sitka spruce (Piceasitchensis (Bong.) Carrière) dominated the old-growth riparian stands and shared dominance with western hemlock (Tsugaheterophylla (Raf.) Sarg.) in the uplands. Regeneration was predominantly spruce in the alder riparian, spruce and hemlock in the old-growth riparian, and hemlock in the upland stands. Total understory biomass and ground cover did not differ significantly between forest types, but species-specific biomasses did differ (P < 0.05). Understory of the upland forest was dominated by early blueberry (Vacciniumovalifolium Sm.) and Alaska blueberry (Vacciniumalaskensis How.), while that of both riparian types was dominated by devilsclub (Oplopanaxhorridum (Sm.) Miq.). Other species-specific differences occurred in forbs (three species) and mosses (three species). Contrary to typical stand age–understory relations in upland conifer forests of the region, the understory of the 40-year-old red alder stands was very species rich and productive.

Management units and their use for identification, mapping and management of major vegetation types in upland conifer forests: J. E. G. Good, H. L. Wallace & T. G. Williams, Forestry, 66(3), 1993, pp 261–290

Management units and their use for identification, mapping and management of major vegetation types in upland conifer forests: J. E. G. Good, H. L. Wallace & T. G. Williams, Forestry, 66(3), 1993, pp 261–290

Management Units and their Use for Identification, Mapping and Management of Major Vegetation Types in Upland Conifer Forests

Management Units were developed for Kielder Forest based on physiographic features and dominant vegetation types, for use by foresters in identification, mapping and management of plant communities in new and existing forests. The National Vegetation Classification was used to characterize the plant communities occurring in unplanted areas thus providing a framework for assessing changes caused by afforestation (notably effects of ploughing and draining and reduced grazing) and subsequent crop growth (increased shade, reduced soil moisture). To enable foresters to make similar comparisons elsewhere, a dichotomous key was devised to assist identification of NVC communities within upland forests. However, most plant communities in conifer crops with well-developed canopies are transitional between NVC communities and some of them appear stable and recognizable as conifer plantation communities. Forest Management Units provide a useful broad classification system above the National Vegetation Classification, offering a sound basis for the creation of vegetation conservation inventories at the regional, forest district or individual forest scales. Management Units can also aid the definition of broad conservation objectives and the drawing up of management prescriptions and could provide a basis for determining non-crop (amenity, recreation, wildlife) values of forests. They are not intended to provide information at a scale allowing specific plant communities to be mapped, nor to provide the more detailed prescriptions required for the conservation of such communities.

A radio tracking study of post‐fledging mortality and movements of Tawny Owls in Argyll

The post‐fledging mortality and behaviour of Tawny Owls was investigated in an upland conifer forest in Argyll, in a year of poor food supply. Twelve unsexed juvenile and 6 adult female owls were fitted with back‐mounted radios. Eleven (91.7%) of the juveniles died between fledging and independence. Deaths occurred in two peaks, initially in the period immediately following fledging when they were vulnerable to mammalian predators, and later on when they died mostly of starvation. While dependent on their parents the corrected home range size of the juveniles varied from 0.8 to 3.5 ha. Two broods showed sudden movements of 400–500 m from coniferous habitat around the nest site to predominantly broadleaved areas. The one juvenile that successfully left its parents territory did so 81–86 days after fledging. These results are discussed in relation to the method of radio tracking used.

Natural features in the management of upland conifer forests

SynopsisUpland conifer afforestation has been a major factor in environmental change, and there is every prospect that further afforestation will take place. How can we best develop the existing forests as wildlife habitats? And, if afforestation is to continue, where should further plantations be placed? This paper considers some general aspects of forest habitat design, using the structure and dynamics of natural boreal-temperate conifer forests as its primary reference point.