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Plantations in degraded forest areas in arid and semi-arid regions play a vital role in restoring ecosystems, controlling erosion, and supporting local livelihoods. However, little is known about how exotic and native tree species influence nutrient dynamics in soil and foliage, particularly regarding nutrient retranslocation. This study evaluated seasonal variation in leaf nutrient concentrations and nutrient retranslocation patterns over a 6-month period (early April to late September) in 30-year-old plantations of two exotic needleleaf species ( Cupressus arizonica , Pinus eldarica ) and two indigenous broadleaf species ( Amygdalus scoparia , Quercus brantii ). The findings revealed significant differences among species groups. Broadleaf species generally exhibited higher concentrations of leaf nutrients (such as nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) and lower C: N ratios than needleleaf species. Seasonal effects were evident, with leaf nutrient content generally higher in spring than in summer. The order of nutrient retranslocation was as follows: Ca < C < K < Mg < N < P. Further analysis using principal components highlighted the differences between broadleaf and needleleaf plantations in terms of soil and leaf nutrient status. These findings suggest that, due to its native status and greater contribution to soil fertility, Q. brantii is a suitable choice for reforestation in similarly degraded environments.

In this research, three afforested stands of mesquite at the ages 15, 27, and 34 years were selected in a dry climate region in Iran. In each of the stands, two density classes (180 and 250 trees per ha) were located and 4 square sample plots (40 × 40 m) were randomly selected. After measuring the tree height, crown height, collar diameter and crown area, aboveground biomass was calculated using experimental and semi-empirical allometric equations. The soil quality index was determined at two depths based on the measured physical, chemical and biological characteristics of the soil samples. The results showed that stand age, stand density and their interaction significantly affected stem number, crown height growth and soil quality index. The average number of stems was the highest in the 15-year-old stand and the lowest in the 34-year-old stand. Height, collar diameter, basal area growth, biomass, and competition between trees were significantly affected by stand age and its interaction with stand density (p < 0.01). The average annual growth of tree collar diameter and height with age was lowest (4.1 mm per year and 17.7 cm per year, respectively) in the 34-year-old stand, compared to average annual growth rates of 7.2 mm and 31 cm for collar diameter and height, respectively, in the 15-year-old stand. In general, high density mesquite afforestation plantings in this dry and desert area improves soil quality and increase vegetative and productivity characteristics of mesquite, especially as stands age.

Oak cover types comprise half of the forestlands in the eastern United States. There is a great desire to sustain these highly valued forests. Unfortunately, reports of the successional replacement of oak are all too common, as they are throughout the world. Sustaining the oak resource requires the ability to both regenerate and recruit oak into the overstory as dominant mature trees. Too often these two critical processes are disconnected in oak management, thwarting the best of intentions to sustain oak. Restoring and sustaining oak forests require active management and long-term commitment. Climate change, high deer populations, invasive species, and social constraints can complicate oak management. Despite these challenges, we have sufficient knowledge to be successful in our efforts despite an uncertain future. Forest landscapes are too homogeneous today and may cause a bottleneck in oak regeneration as mature forests become old-growth. Management is needed to diversify the landscape and create a more balanced age structure that has the capacity to naturally regenerate oak. Landscape diversity is also desired to combat the myriad of forest threats and future uncertainty. Getting private landowners and public managers to manage for oak is key to changing landscapes and ensuring a quality oak resource.

Increasingly detailed records of long‐term fire regime characteristics are needed to test ecological concepts and inform natural resource management and policymaking. We reconstructed and analyzed twelve 350+ yr‐long fire scar records developed from 2612 tree‐ring dated fire scars on 432 living and dead pine (Pinus pungens, Pinus rigida, Pinus resinosa, Pinus echinata) trees from across central Pennsylvania. We used multiple spatial and time series analysis methods to quantify fire regime characteristics (frequency, seasonality, percentages of trees scarred, extent) and fire–climate–human associations. Prior to the 20th‐century fire suppression, fire regimes at the majority of sites consisted of frequent, low‐to‐moderate severity, dormant season fires. Fires were often regionally synchronous when preceded by significantly dry years. Using documentary archives, we provide the first description of a “wave of fire”—an anthropogenic signal in fire frequency that progressively moved across the region. This “wave of fire” reflects a changing progression of anthropogenic fire regimes from Native American occupation and depopulation, to Euro‐American settlement, to industrialization and declining fire use up to the 20th century era of fire suppression. The wave of fire provides a new perspective on historical and modern fire regime dynamics and identifies socio‐ecological impacts since North American colonization. Because the anthropogenic wave of fire exists at sites across North America, we emphasize the need for a broader determination of its geographic prevalence and variability as such determinations could influence historical ecology interpretations and perspectives on past and future roles of humans in managing ecosystems with fire.

Failed oak regeneration is widely reported in temperate forests and has been linked in part to changed disturbance regimes and land‐use. We investigated if the North American fire–oak hypothesis could be applicable to temperate European oaks (Quercus robur, Quercus petraea) using a replicated field experiment with contrasting canopy openness, protection against ungulate browsing (fencing/no fencing), and low‐intensity surface fire (burn/no burn). Survival, relative height growth (RGRH), browsing damage on naturally regenerated oaks (≤300 cm tall), and changes in competing woody vegetation were monitored over three years. Greater light availability in canopy gaps increased oak RGRH (p = .034) and tended to increase survival (p = .092). There was also a trend that protection from browsing positively affected RGRH (p = .058) and survival (p = .059). Burning reduced survival (p < .001), nonetheless, survival rates were relatively high across treatment combinations at the end of the experiment (54%–92%). Most oaks receiving fire were top‐killed and survived by producing new sprouts; therefore, RGRH in burned plots became strongly negative the first year. Thereafter, RGRH was greater in burned plots (p = .002). Burning altered the patterns of ungulate browsing frequency on oaks. Overall, browsing frequency was greater during winter; however, in recently burned plots summer browsing was prominent. Burning did not change relative density of oaks, but it had a clear effect on competing woody vegetation as it reduced the number of individuals (p < .001) and their heights (p < .001). Our results suggest that young, temperate European oaks may respond similarly to fire as their North American congeners. However, disturbance from a single low‐intensity fire may not be sufficient to ensure a persistent competitive advantage—multiple fires and canopy thinning to increase light availability may be needed. Further research investigating long‐term fire effects on oaks of various ages, species‐specific response of competitors and implications for biodiversity conservation is needed. We investigated if the North American fire–oak hypothesis could be applicable to temperate European oaks. Although a low‐intensity fire reduced oak seedling survival, survival rates were relatively high across treatment combinations (54%–92%) and relative height growth was greater in burned plots after 2 years. Burning did not change relative density of oaks, but it had a clear effect on competing woody vegetation as it reduced the number of individuals and their heights, especially for conifers.

The long history of fire in North America spans millennia and is recognized as an important driver in the widespread and long-term dominance of oak species and oak natural communities. Frequent wildfires from about 1850 to 1950 resulted in much forest damage, and gained fire a negative reputation. The lack of fire for the past nearly 100 years due to suppression programs is now indicted as a major cause of widespread oak regeneration failures and loss of fire-dependent natural communities. The use of prescribed fire is increasing in forest management and ecosystem restoration. An understanding of fire effects on trees can provide the basis for the silviculture of restoring and sustaining oak ecosystems. We present an overview of fire-tree wounding interactions, highlight important determinants of fire injury and damage, and discuss several practical situations where fire can be used to favor oak while minimizing damage and devaluation of the forest. We also identify stages in stand development, regeneration methods, and management objectives for which fire has the potential of causing substantial damage and recommend preferred alternative practices.

A predictive equation for estimating fire frequency was developed from theories and data in physical chemistry, ecosystem ecology, and climatology. We refer to this equation as the Physical Chemistry Fire Frequency Model (PC2FM). The equation was calibrated and validated with North American fire data (170 sites) prior to widespread industrial influences (before ~1850 CE) related to land use, fire suppression, and recent climate change to minimize non-climatic effects. We derived and validated the empirically based PC2FM for the purpose of estimating mean fire intervals (MFIs) from proxies of mean maximum temperature, precipitation, their interaction, and estimated reactant concentrations. Parameterization of the model uses reaction rate equations based on the concentration and physical chemistry of fuels and climate. The model was then calibrated and validated using centuries of empirical fire history data. An application of the PC2FM regression equation is presented and used to estimate historic MFI as controlled by climate. We discuss the effects of temperature, precipitation, and their interactions on fire frequency using the PC2FM concept and results. The exclusion of topographic, vegetation, and ignition variables from the PC2FM increased error at fine spatial scales, but allowed for the prediction of complex climate effects at broader temporal and spatial scales. The PC2FM equation is used to map coarse-scale historic fire frequency and assess climate impacts on landscapescale fire regimes.

Guidelines for managing sugar maple-dominated forests by the single-tree selection method are well established and widely adopted. The forests of the Menominee Tribe in Wisconsin provide an opportunity to validate current guidelines by testing tree value and size/age relationships in forests that have substantially older and larger high-quality trees than can be found through the northern region. We harvested grade 1 sugar maple trees across a wide spectrum of ages and diameters, which we then manufactured into veneer, sawlogs, cants, and hardwood/pulpwood bolts to determine tree value. Tree value continued to increase with increasing dbh, but when the effect of tree age on value was discounted, the value of trees older than 100 years dropped precipitously toward zero. Thus, managing trees to maximize diameter and quality within genetic and site potential and harvesting at about 100 years will produce high-value grade 1 trees in the range of 24 to 30 in. dbh.

Variability in historic fire regimes in eastern North America resulted in an array of oak natural communities that were dominant across the region. In the past century, savannas and woodlands have become scarce because of conversion to agriculture or development of forest structure in the absence of fire. Their restoration is a primary goal for public agencies and conservation organizations. Although they can be restored with a long-term regimen of prescribed burning, a combination of fire, timber harvesting, and forest thinning produces the desired structure and composition more efficiently. Prescribed fire is useful for sustaining oak savannas and woodlands, but it must be used judiciously to minimize timber damage and decreases in value. Integrating fire within a modified shelterwood approach promotes competitive oak reproduction and is flexible enough to produce savannas or woodlands. Sustaining these communities requires the replacement of the overstory during periods of no fire.

In Wisconsin, as in other states, management goals sometimes include restoration of historical forest conditions, which may prepare forests to be more compatible with future climates, disturbances such as drought and fire, and forest health threats. We quantified historical (1830–1866) composition and structure to develop historical reference conditions for restoration and documented changes based on current (2005–2009) forest surveys in Wisconsin. We provided structural metrics, functional group composition, and forest types for 186 ecological land types, and we also summarized trends in composition and structure. Wisconsin forests historically were comprised of 46% oak or pine savanna or woodland, 6% pine forest, and 48% forests primarily consisting of late-successional eastern broadleaf forest species and early-successional northern mixed forest species; densities of these forest types ranged from 60 to 460 trees/ha. In the Eastern Broadleaf Forest ecological division, increased composition of the early-successional and mid-successional eastern broadleaf forest groups (from 10 to 40%) and (planted) pine group (8–23%) occurred along with decreased fire-tolerant oak composition (from 65 to 23%). Density increased in current forests compared to historical forests by a factor of 2.2; despite increased density, basal area increased only slightly due to the presence of larger diameter trees in historical tree surveys. In the Northern Mixed Forest ecological division, increased composition of the mid-successional eastern broadleaf forest group (from 12 to 24%) and late-successional northern mixed forest group (from 10 to 17%) occurred due to decreased composition of the fire-tolerant pine group (from 17 to 9%) and late-successional eastern broadleaf forest group (from 30 to 20%). Density remained similar in current forests compared to historical forests but current basal area was 50% of historical basal area. The transition from open fire-tolerant oak and pine forests, with rarity of early-successional tree species, to closed forests composed of a variety of early- and mid-successional tree species parallels results from other research. Replacement of open oak or pine forest ecosystems by dense forests has moved Wisconsin outside of the historical range of variability, likely reducing plant and wildlife species associated with open oak and pine ecosystems.