Mature Stands Research Articles

Exploring Effects of Nutrient Availability, Species Composition, Stand Age, and Mesofaunal Exclusion on Leaf Litter Decomposition in Northern Hardwood Forests

In northern hardwood forests, litter decomposition might be affected by nutrient availability, species composition, stand age, or access by decomposers. We investigated these factors at the Bartlett Experimental Forest in New Hampshire. Leaf litter of early and late successional species was collected from four stands that had full factorial nitrogen and phosphorus additions to the soil and were deployed in bags of two mesh sizes (63 µm and 2 mm) in two young and two mature stands. Litter bags were collected three times over the next 2 years, and mass loss was described as an exponential function of time represented by a thermal sum. Litter from young stands had higher initial N and P concentrations and decomposed more quickly than litter from mature stands (p = 0.005), regardless of where it was deployed. Litter decomposed more quickly in fine mesh bags that excluded mesofauna (p < 0.001), which might be explained by the greater rigidity of the large mesh material making poor contact with the soil. Neither nutrient addition (p = 0.94 for N, p = 0.26 for P) nor the age of the stand in which bags were deployed (p = 0.36) had a detectable effect on rates of litter decomposition.

Attenuated asymmetry of above- versus belowground stoichiometry to a decadal nitrogen addition during stand development.

Deciphering the linkage between ecological stoichiometry and ecosystem functioning under anthropogenic nitrogen (N) deposition is critical for understanding the impact of afforestation on terrestrial carbon (C) sequestration. However, the specific changes in above- versus belowground stoichiometric asymmetry with stand age in response to long-term N addition remain poorly understood. In this study, we investigated changes in stoichiometry following a decadal addition of three levels of N (control, no N addition; low N addition, 20 kg N ha-1 year-1; high N addition, 50 kg N ha-1 year-1) in young, intermediate, and mature stands in three temperate larch plantations (Larix principis-rupprechtii) in North China. We found that low N addition had no impact on both above- (leaf and litter) and belowground (soil and microbe) stoichiometry. In contrast, high N addition resulted in significant asymmetry in above- versus belowground stoichiometry, which then diminished during stand development. Following 10 years of N inputs, the young and intermediate plantations transitioned from a state of relative N limitation to co-limitation by both N and phosphorus (P), whereas the mature plantation continued to experience relative N limitation. Conversely, soil microorganisms exhibited relative P limitation in all three plantations. Broader niche differentiation (N limitation for trees, but P limitation for microorganisms) under long-term N input may have been responsible for the faster attainment of stoichiometric homeostasis in mature plantations than in young plantations. Our findings provide stoichiometric-based insight into the operating mechanisms of large C sinks in young forests, particularly above- versus belowground C stock asymmetry, and highlight the need to consider the role of flexible stoichiometry when forecasting future forest C sinks.

The stoichiometric characteristics of carbon, nitrogen, and phosphorus in soil aggregates of Cryptomeria japonica plantation with stand ages in the Rainy Area of Western China.

Understanding the variations in soil aggregate composition, as well as the contents and stoichiometry of organic carbon (C), total nitrogen (N) and total phosphorus (P), in the surface layer of Cryptomeria japonica plantations with different stand ages can provide a theoretical basis for the optimized management of plantations and the improvement of soil fertility in the Rainy Area of West China. With the dry-sieving method, we measured the contents of soil aggregates with different sizes in the 0-15 and 15-30 cm soil layers across C. japonica plantations with five distinct developmental stages at Hongya Forestry Farm, Sichuan Province, including young stands (7 years old), middle-aged stands (13 years old), nearly mature stands (24 years old), mature stands (33 years old), and over-mature stands (53 years old). We further analyzed the C, N and P contents and ecological stoichiometric characteristics of soil aggregates. The results showed that the particle size composition of soil aggregates in C. japonica plantations varied among stand ages. The nearly mature and mature stands had higher proportion of large aggregates (0.5-1 and 1-2 mm), whereas the nearly mature stand had a lower proportion of micro-aggregates (0.053-0.25 mm) and the silt-plus-clay fraction (<0.053 mm). Moreover, the C, N and P contents and stoichiometric ratios in soil aggregate showed a unimodal pattern, which increased initially and then decreased with stand age, with peak values in the nearly mature and mature plantations. Furthermore, the C, N and P contents in aggregates in 0-15 cm soil layer were higher than that in the 15-30 cm soil layer. The highest C and N contents were found in the aggregates with particle sizes of 0.5-1 and 0.25-0.5 mm. In conclusion, the near-mature and mature stands of C. japonica plantations have higher nutrient content in soil aggregate, underscoring these stages was critical for maintaining soil fertility and advancing sustainable management practices.

Variations in litterfall dynamics, root biomass, and sediment accretion in restored and recolonized mangroves in Leyte, Philippines

Litterfall production and decay, root biomass, and sediment accretion dynamics were investigated from restored ‘planted’ (R5, R8, R15, and R30 stands) and recolonized stands (C5, C12, and C20 stands) to investigate patterns in primary productivity, belowground biomass, and sediment accretion dynamics. Litterfall data was collected using litter traps over 12 months, while decay kinetics was investigated using a litterbag experiment. Root biomass and sediment accretion data were collected using makeshift acrylic corers. Litterfall production increased as stands aged, and tended to stabilize as it matured in restored (R8: 10.05 Mg/ha/yr; R30: 6.1 Mg/ha/yr) and recolonized stands (C5: 18.75 Mg/ha/yr; C20: 9.05 Mg/ha/yr). Leaf litter decay rates (K/d) showed no pattern with stand age, although the recolonized stands (range: 0.059–0.113 K/d) had lower decay rates compared to the restored (range: 0.073–0.123 K/d) and natural stands (range: 0.064–0.123 K/d). Root biomass declined with age in restored stands (R5: 67.16 Mg/ha, R30: 49.67 Mg/ha), but increased in recolonized stands (C5: 5.41 Mg/ha, C20: 19.50 Mg/ha). Very high rates of sediment accretion were found in younger restored (R5: 10.1 cm/yr) and recolonized stands (C5: 8.1 cm/yr) than mature stands (R30: 6.3 cm/yr; C20: 4.3 cm/yr). Our results showed disparities of patterns in mangrove vegetation growth in recolonized stands and huge potential contribution on mangrove productivity when these areas are effectively restored.

Bark Thickness of Forest-forming Species: Modeling and Comparative Analysis

The need to assess the carbon-depositing capacity of a stand, an individual tree and its components is constantly emphasized in the world literature, since mitigation of the effects of climate change has become the highest priority. Since the carbon concentration differs in different tree species and in different components of the tree, including in the stem wood and bark, it is necessary to develop species-specific mathematical models for estimating the proportion of bark in trunks to improve the accuracy of knowledge about the carbon balance of forests. The relationship of bark thickness with both age and diameter of the tree trunk is known, but with respect to its regional variability, the data are contradictory. According to the actual data from 1100 model trees of five forest-forming species, allometric models of a mixed type have been developed. They include as independent variables the age and diameter of the trunk, as well as a binary variable characterising the influence of the growing area itself on the bark thickness of Scots pine, silver birch and Siberian larch, as well as the difference in the thickness of the bark between Siberian spruce and Siberian fir in case of joint growth in mature stands of the taiga zone. At a statistically significant level, it was found that the bark thickness of Scots pine and silver birch trees in the steppe zone is significantly greater compared to the taiga zone, and the bark thickness of Siberian larch trees in the forest-tundra is significantly greater compared to the steppe zone. The bark thickness of Siberian spruce trees is significantly less than that of Siberian fir trees. The ranking of species by bark thickness is included in the paper.

Mixed stands of black spruce (Picea mariana) and tamarack (Larix laricina) offer high secondary growth in eastern boreal forests of Canada

The Canadian boreal forest is still lacking investigation into compatible species mixtures that can lead to higher growth rates than monospecific or pure stands. The effect of species mixtures on stand productivity can vary with stem density, species proportion, site characteristics, and climate variation. We investigated mixed stands of black spruce (Picea mariana) and tamarack (Larix laricina) in eastern Canadian boreal forests. Using modern forest survey data, we analyzed stand basal area variation in 756 mature stands exclusively composed of these two species over a study area spanning 535,000 km². We generated a linear relationship between mixed stand basal area and stem density, and the residual of this relation was used as response variable named ‘residual basal area’. Positive and negative deviations of residual basal area were analysed with generalized additive models and quantile regressions with tamarack basal area, climate, and site characteristics as explanatory variables. The selected model included tamarack basal area, mean seasonal precipitation, degree days, mean annual temperature, stand age, latitude, longitude, and the type of surficial deposit. Tamarack exhibited a linear positive effect on predicted residual basal area. The most significant effect was observed from the interaction between tamarack basal area and stand age, predicting positive residual basal area of 16 m² ha−1 when stand aged was 150 years old and tamarack basal area was between 12 and 17 m² ha−1. Quantile regressions revealed that tamarack could enhance basal area while increasing black spruce stem size and density. Landscape managers may consider the establishment of mixed black spruce and tamarack stands to favor secondary growth in eastern Canadian boreal forests.

Structure of Ground Vegetation and Natural Regeneration of Tree Species in 12- to 15-Year-Old Bilberry Pine Forest-Clear-cut Complex of Middle Taiga Subzone.

Logging in mature stands where part of the forest is harvested in one or several cuts and part is retained (clearcutting and alternate strip cutting) results in the formation of an ecotone complex (EC), which includes a forest (F) zone, a forest edge (FE) as a transition from the forest to the clear-cut under the canopy, a clear-cut edge (CE) as a transition from the forest to the clear-cut outside of the canopy, and the clear-cut proper (C). The composition and structure of ground vegetation and natural regeneration of woody species (Pinus sylvestris L., Picea abies (L.) H. Karst., Betula sp., Populus tremula L., Sorbus aucuparia L., and Juniperus communis L.) were studied in a bilberry pine forest-clear-cut ecotone complex 12-15 years after stand removal. Specific structural features of ground vegetation and undergrowth (including tree regeneration) were observed in each of the four zones of the ecotone complex formed after logging of the mature forest. Atypical forest habitat (zone F) showed a minimum number of young regeneration of Pinus sylvestris, Picea abies, Betula sp., Populus tremula, and Sorbus aucuparia and the highest abundance of the lingonberry V. vitis-idaea L. and bilberry Vaccinium myrtillus L. with a maximum height and a maximum yield of bilberry plants. The amount of tree regeneration in the FE zone was much the same as in the F zone. The projective cover, maximum shoot height, and yield of bilberry and the maximum shoot height of lingonberry in the FE zone were significantly lower than in the F zone. The transitional zone on the clear-cut side (CE) and the clear-cut proper (C) strikingly differed from the forest (F and FE) zones of the ecotone complex by a greater number of deciduous and pine regeneration and a low abundance of dwarf shrubs. The clear-cut proper (C) differed from the CE zone by a higher abundance of grasses and forbs and an established tree regeneration layer composed of pine, birch, and aspen.

Nitrogen availability and its related enzyme activities affect microbial residue nitrogen accumulation during Chinese fir plantation development

Microbial growth, metabolism, and reproductive activities have a significant role in the generation, transformation, and storage of soil nitrogen (N). However, the time-integrated effect of microorganisms on long-term N sequestration in plantation forests remains poorly understood. We investigated the microbial residue N (MRN) and its contribution to soil total N (TN) among the young (8-year), middle (16-year), near-mature (24-year), mature (34-year), and over-mature (106-year) stands of Chinese fir plantation (CFP) in subtropical China. The soil TN content showed a general pattern of increasing with stand age, ranging from 2.61 to 3.42 g kg−1, and was higher in the over-mature and mature stands than in the other three stands (p < 0.001). In addition, soil carbon (C), N, phosphorus (P), and hydrolase stoichiometric ratios indicated that P limitation was widespread during all stages of CFP development. The average ratio of soil fungal residue N (FRN) to bacterial residue N (BRN) was 3.64:1. The MRN content and its contribution to soil TN exhibited a falling and then rising pattern from young to over-mature stands, ranging from 1.24 to 1.70 g kg−1 and 38.8 % to 57.5 %, respectively. Soil N fraction contents and hydrolase activities were higher in the 0–5 cm soil layer than in the 5–30 cm soil layer (p < 0.05). Regression analysis showed that soil MRN content increased with soil N fraction contents, C-N-P stoichiometric ratios, and hydrolase activities (p < 0.001). Redundancy analysis and partial least squares path modeling revealed that soil available N (AN) and N hydrolase were the main factors affecting MRN accumulation. These parameters may partially indicate the dynamics of MRN accumulation. Our study discovered that the long-term development of CFP promotes soil N sequestration, with microbial residues playing a significant role in contributing to N pools.

Four decades of data indicate that planted mangroves stored up to 75% of the carbon stocks found in intact mature stands.

Mangroves' ability to store carbon (C) has long been recognized, but little is known about whether planted mangroves can store C as efficiently as naturally established (i.e., intact) stands and in which time frame. Through Bayesian logistic models compiled from 40 years of data and built from 684 planted mangrove stands worldwide, we found that biomass C stock culminated at 71 to 73% to that of intact stands ~20 years after planting. Furthermore, prioritizing mixed-species planting including Rhizophora spp. would maximize C accumulation within the biomass compared to monospecific planting. Despite a 25% increase in the first 5 years following planting, no notable change was observed in the soil C stocks thereafter, which remains at a constant value of 75% to that of intact soil C stock, suggesting that planting effectively prevents further C losses due to land use change. These results have strong implications for mangrove restoration planning and serve as a baseline for future C buildup assessments.

Investigating hydrological recovery in regenerating coniferous stands in snow‐dominated watersheds using simultaneous localization and mapping‐enabled mobile terrestrial LiDAR

AbstractThe return of snow accumulation and ablation processes in regenerating forests to pre‐disturbance conditions, collectively referred to as hydrological recovery, has been investigated in past decades through manual snow surveys in adjacent open, juvenile, and mature stands. The outcomes of such studies provide a general understanding of hydrological recovery but lack transferability to areas where stand structure and terrain conditions differ from the reference sites. The application of mobile terrestrial LiDAR to investigate peak snow water equivalent (SWE) and ablation rates beneath regenerating trees in a space‐for‐time substitution study design provides new insights on the process of hydrological recovery in snowmelt forests of British Columbia, Canada. Outcomes of this study better quantify the influence of tree growth on peak SWE and ablation rate at both the tree and stand level for north aspect mixed conifer stands. Recovery of these two processes differ with recovery of Peak SWE beginning when the trees in a stand reach 3 m in height and recovery of ablation rates beginning once trees reach 5 m in height. Additionally, the process of negative ablation recovery in early juvenile stands reported in previous studies is herein clearly observed, providing an improved understanding of forest canopy effects on hydrological recovery in juvenile stands. The methods used in this study, which are internationally applicable, increase transferability of outcomes to stands where canopy characteristics (i.e., height, crown cover, and heterogeneity) are not represented in reference sites.

Effects of silvicultural release on artificial oak regeneration in bottomland hardwood forests in northern Missouri

In bottomland forests, managing oak regeneration is challenging due to competition with other species. Low understory light levels in mature stands favor more shade-tolerant tree species, whereas harvest often results in release of fast-growing competitors. In the late 1990s, a study was initiated in northeastern Missouri to evaluate the effects of overstory harvests on stand development of bottomland forests, with particular interest in oak regeneration. Canopy removal resulted in rapid growth of undesired soft-mast species without increasing the abundance of oak reproduction. In 2017, bare-rooted pin oak (Quercus palustris Muenchh.) and swamp white oak (Quercus bicolor Willd.) seedlings were planted, to increase the oak component through enrichment planting in the stands that had previously been harvested and underplanting in the stands that had received no regeneration harvest. For all planted seedlings, three levels of midstory release treatments were applied after planting in 2017, including a control (no release), and light release, and a heavy release. This study tested the effects of the original overstory harvests and the subsequent midstory release on survival and development of planted oak advance reproduction over 5 years. Our results suggest that establishing oak advance reproduction prior to overstory harvest is more efficient than enrichment planting after overstory harvest. A prior midstory release is important to develop competitive oak advance reproduction before a later overstory harvest to ensure successful oak regeneration.

A Multi-Criterion Evaluation Process for Determining Cost-Effective Harvesting Systems in Fragmented Boreal Forests

Nordic forests, like those found in Canada, used to consist of large and relatively homogeneous mature stands. Such a spatial pattern allows for harvest operations to be highly concentrated, minimizing procurement costs. However, the growing fragmentation of these forests makes planning difficult and increases the costs of road building and machinery relocation. While operational solutions have been developed in regions with small harvest areas, their transferability to different settings is unknown. Finding the most suitable combination of equipment for a given context is challenging considering the multitude of possibilities. The objective of this study is to identify, from all possible options, a subset of harvest systems expected to perform well in fragmented boreal forests. The results from this research are two-fold. First, a comprehensive review of forest machines and harvest systems is provided. Second, a multi-criteria decision analysis (MCDA) methodology is proposed to evaluate the alternatives. In a boreal forest context, the conventional harvester-forwarder system (CTL) was ranked among the best solutions, along with mild adaptations of the usual configurations. Several whole-tree (WT) system configurations were also highly ranked. While the results are specific to the case studied, the review and selection methodology can serve in different operational contexts.

One-year effects of stand age, pre-fire treatments, and hillslope aspect on recovery of plant diversity and soil properties in a Mediterranean forest burnt by a severe wildfire

Although several management options are adopted to redirect post-fire forest ecosystems towards less vulnerable and more resilient and functional communities, little is known about the interactions among tree stand age, pre-fire forest management, and slope aspects, and their consequences for plant species and soil properties recovery immediately after severe wildfires. To address this knowledge need, this study evaluates the post-fire changes in species richness and diversity (with a specific focus on regeneration mechanisms and life forms) of regenerating plants as well as the main physico-chemical and biological properties of burned soils with the reciprocal relations. Plant cover and diversity, and many soil properties have been monitored in forests of southeast Spain with mature, middle and young stands, presence of pre-fire treatments or not, and north and south hillslopes about one year after the fire. To this aim, the reciprocal relationships among soil properties and plants were evaluated adopting a combination of statistical techniques (PERMANOVA, Non-metric Multi-Dimensional Scaling, Distance-based Linear Modelling, Distance-based Redundancy Analysis, and Spearman correlation analysis). The damage to soil and vegetation was so high that both plants and pre-fire soil properties slowly recovered. Only a few life forms of vegetation (geophytes and herbaceous chamaephytes) were influenced by the stand age. If combined with soil aspect, stand age resulted in significantly lower germinating species in mature stands and lower resprouters in young stands, both on south hillslopes. Plant diversity was high, and the post-fire regeneration did not change the species richness and evenness. The post-fire changes in soil properties were limited, and only slight small differences in pH and betaglucosidase among stands of different age were found. No evident associations between soil properties and plant diversity were revealed by the low correlation coefficient. The low variance in plant cover and diversity, as well as in soil properties, resulted in a low accuracy of the dbRDA model to reproduce its variability among sites with different pre-fire characteristics.

Diminishing mangrove forest structures in Davao City, Philippines

The decline of mangrove coverage across the Philippines to 50% of its original coverage in present years has, led to significant reductions of ecological functions to fisheries and benefits to man. The mangrove forest in Davao City was assessed for its taxonomic list, Importance Value Index, abundance and distribution of mangrove regenerations, forest structure, and species diversity status. The study was conducted in Barangay Bunawan, Lasang, Panacan, Matina Aplaya, 76-A, and Bago Aplaya. All data were gathered by establishing sampling plots (10m x 10m) using the modified transect-plot method. Overall, a total of 34 mangrove species were listed, of which 21 were identified as true mangroves and 13 as mangrove associates. The 21 mangrove species were very low in species richness (54%). Importance Value Index showed that Avicennia marina, Rhizophora apiculata, and Sonneratia alba, respectively, as dominant mangrove species. The mangrove regenerations were in poor condition (&lt;0.50) while relative abundances of growth stages consisted of mature stands at 46.04%, saplings with 27.78%, and seedlings with 26.18%. General diversity indices obtained a low value on the Shannon-Wiener diversity index (H'=1.42) and an average value on the species evenness index (E=0.61), all indicating stressful and unstable mangrove forests. Thus, the mangrove forest ecosystem has imbalances and eventually, only certain species would survive.

Carbon Sequestration Dynamics in Peri-Urban Forests: Comparing Secondary Succession and Mature Stands under Varied Forest Management Practices

This study examines the impact of silvicultural and land-use management practices on carbon sequestration in peri-urban forest ecosystems, with a particular focus on human-induced carbon dynamics. The study area’s complex profile spans from a compact native forest to varying degrees of fragmentation. This included areas undergoing secondary succession forest without silvicultural interventions (No-SI) alongside sites subjected to high-intensity (High-SI) and low-intensity silvicultural interventions (Low-SI). The research assessed carbon stocks and sequestration in different carbon pools (living biomass, dead organic matter and soil) using field data, allometric equations and laboratory analysis. Findings reveal a significant correlation between the intensity of anthropogenic interventions and variations in carbon stocks. The CASMOFOR model facilitated the reconstruction of carbon stock and carbon-stock change dynamics over four decades (1980–2022), showing disparities in carbon storage capabilities linked to the structural characteristics of the sites. The Low-SI site had the highest carbon stock in all carbon pools (378 tonnes C ha−1), which is more than double compared to High-SI (161 tonnes C ha−1) or No-SI sites (134 tonnes C ha−1). However, the secondary succession forest (No-SI) demonstrated the highest annual carbon stock change (4.4 tonnes C ha−1 year−1), two times higher than the Low-SI mature stand (2.2 tonnes C ha−1 year−1), emphasising the resilience of forest ecosystems to recover and sustain carbon sequestration capacities after harvesting if forest land use remains unchanged. The study underscores the significant importance of anthropogenic interventions on carbon dynamics, especially for living tree biomass, which has consequences in enhancing carbon sequestration and contributing to emission reduction targets.

Возрастная динамика биомассы ольхи серой в древостоях Архангельской области

The assessment of forest productivity in forestry and forest ecology has a long tradition, but in recent decades there has been a paradigm shift: the target function of forestry, consisting in wood cultivation, has shifted towards the biosphere-stabilizing function and the assessment of biomass and carbon sequestration capacity of forests. Equations and tables for assessing biomass at the stand level have an advantage as they can be used to characterize both the biomass of individual stands and their totality, as well as (when combined with the state forest inventory data) the situations in the forests throughout the country. The complexity of the work on assessing biomass of trees and stands has prompted researchers to use the existing tables of growth progress when compiling the tables of biological productivity of the stands using the recursive method. For the conditions of the northern and middle taiga of the Arkhangelsk Region, there are no tables of growth progress for gray alder biomass. The aim of this research is to study the growth progress of gray alder biomass in the stands of the Arkhangelsk Region. A series of sample plots has been laid to assess the above-ground biomass of the trees of this species. Based on the actual data from 50 model trees from 30 sample plots, the allometric models of the dependence of biomass fractions on the stem volume have been developed. The obtained models have been combined with the tables of growth progress for gray alder by quality class and the table of biological productivity of the species for the conditions of the Arkhangelsk Region has been drawn up. The results have been compared with the data on the biological productivity of gray alder in Belarus, Lithuania and Latvia. It has been shown that the biomass of the mature stands of gray alder of the 1st and 2nd quality classes in the Arkhangelsk Region is 3–9 % less than in Belarus and Lithuania. For the stands of the third and fourth classes, this difference increases to 29–48 %. Such differences in the biomasses of the compared regions can be explained by different zonal site conditions.

Trade‐offs among management objectives in mature Douglas‐fir forests of the Pacific Northwest

AbstractMature conifer‐dominated forests are an important component of the Pacific Northwest landscape, and the conservation of species associated with late‐successional forests has been a primary management focus in these forests for decades. Increasingly, these forests are also valued as carbon stores, with considerable climate change mitigation potential. However, there are also increasing concerns about the effects of climate change, particularly drought, on late‐successional forests. Despite the complexity of balancing these diverse management concerns, few studies have examined the compatibility of biodiversity conservation, carbon storage, and drought adaptation. We used a spatially and temporally synchronous empirical dataset from mature Douglas‐fir (Pseudotsuga menziesii) stands representing three alternative management strategies, passive management (“unmanaged”), thinning, and retention harvest, to examine trade‐offs among management objectives related to drought adaptation, carbon storage, and the conservation of early‐successional and late‐successional forest songbirds. Although previous studies have evaluated drought adaptation in Douglas‐fir, none have focused on mature stands. Therefore, we also examined tree resistance and resilience to the 2001 drought. Trees in retention harvest stands displayed significantly higher drought resistance and resilience than trees in thinned or unmanaged stands, but no differences were observed between trees in the latter two management conditions, potentially due to the long (average of 22 years) period between treatment and drought in our thinned stands. Despite this, thinned stands provided a better multiobjective compromise than unmanaged or retention harvest stands in our trade‐off analysis. Across all mature stands, trade‐offs were largest for objective combinations that involved early‐ or late‐successional forest birds. While our analysis supports the consistency of managing late‐successional forest birds and carbon storage, trade‐offs between early‐successional birds and carbon storage were much larger. Given projected changes in climate, the substantial trade‐offs that we observed between drought adaptation and late‐successional forest birds are notable and imply that achieving these two objectives will be challenging at the stand scale. Our results suggest that a diversity of management approaches, incorporating both active management and reserve‐based strategies, may be necessary to foster a combination of drought adaptation, carbon storage, and biodiversity conservation goals in these forests.

Influence of microclimate and forest management on bat species faced with global change.

Climate refugia, areas where climate is expected to remain relatively stable, can offer a near-term safe haven for species sensitive to warming temperatures and drought. Understanding the influence of temperature, moisture, and disturbance on sensitive species is critical during this time of rapid climate change. Coastal habitats can serve as important refugia. Many of these areas consist of working forestlands, and there is a growing recognition that conservation efforts worldwide must consider the habitat value of working lands, in addition to protected areas, to effectively manage large landscapes that support biodiversity. The sensitivity of forest bats to climate and habitat disturbance makes them a useful indicator taxon. We tested how microclimate and forest management influence habitat use for 13 species of insectivorous bats in a large climate refugium in a global biodiversity hotspot. We examined whether bat activity during the summer dry season is greater in forests where coastal fog provides moisture and more stable temperatures across both protected mature stands and those regularly logged. Acoustic monitoring was conducted at a landscape scale with 20 study sites, and generalized linear mixed models were used to examine the influence of habitat variables. Six species were positively associated with warmer nighttime temperature, and 5 species had a negative relationship with humidity or a positive relationship with climatic moisture deficit. Our results suggest that these mammals may have greater climate adaptive capacity than expected, and, for now, that habitat use may be more related to optimal foraging conditions than to avoidance of warming temperatures and drought. We also determined that 12 of the 13 regionally present bat species were regularly detected in commercial timberland stands. Because forest bats are highly mobile, forage over long distances, and frequently change roosts, the stewardship of working forests must be addressed to protect these species.

Soil Compaction and Productivity Evolution in a Harvested and Grazed Mediterranean Scots Pine (Pinus sylvestris L.) Forest

The effects of machinery and livestock on forest soil compaction have mostly been studied at short-term and local scales. A better understanding of the long-term effects of compaction in mature stands at the management scale is needed, especially in hot and dry climates. This study aims to analyze (1) soil compaction in a Mediterranean Scots pine (Pinus sylvestris L.) forest subjected to mechanized logging and grazing for more than 50 years and (2) forest productivity trends during these 50 years of disturbance. Soil penetration resistance (0–10 cm and 10–20 cm) and soil moisture (0–12 cm) were measured in 181 randomly selected points affected by “high machinery traffic”, “high cattle traffic” or “low traffic”. Decennial forest inventory data on density, timber volume, and recruitment were collected and analyzed over the five decades preceding soil measurements. Soil penetration resistance exceeded 2500 kPa at a significant portion of the sampled points, although the highest levels of compaction tended to be concentrated in the subsurface layer of the high-traffic areas. Cattle and machinery caused significant compaction in these areas and increased penetration resistance in the range of 350–450 kPa. However, despite the long period of disturbance and the increase in penetration resistance observed, no signs of productivity decline were detected in the forest.

Shifts from an extensive to an intensive root nutrient‐acquisition mode with stand development of three Pinus species

Abstract Plant roots employ diverse strategies to acquire soil nutrients, including direct nutrient uptake through absorptive fine roots and root hairs, scavenging nutrients by forming symbioses with mycorrhizal fungi, and mining nutrients by releasing root exudates. However, whether these three strategies are differently coordinated among phylogenetically closely related tree species and how this coordination shifts with stand development remains largely unclear. To fill these knowledge gaps, we measured 13 root morphological, architectural, physiological and mycorrhizal traits tightly related to nutrient‐acquisition of three Pinus species (P. sylvestris var. mongolica, P. densiflora and P. tabuliformis) at young (20‐year‐old) and mature (50‐year‐old) stages planted in nutrient‐impoverished sandy soils, in Northeast China. We found that young trees had thinner absorptive fine roots and a higher specific root length than mature trees across three Pinus species, indicating that roots become morphologically less efficient in ‘do it yourself’ scavenging nutrients during stand development. Moreover, young stands had greater root length density and root area index, and mature stands had faster root‐exudation rates, suggesting that young stands rely more on expanding soil volumes to scavenge nutrients and mature stands depend more on root exudation to ‘mine’ nutrients. The three Pinus species exhibited different nutrient‐acquisition strategies at the mature stage; P. densiflora had higher root length density and root area index, and the other two Pinus species had greater ectomycorrhizal colonization rates. Synthesis. Our findings highlight that phylogenetically closely related tree species may exhibit different nutrient‐acquisition strategies and suggest a shift from an extensive nutrient‐acquisition mode depending more on absorptive fine roots to an intensive nutrient‐acquisition mode relying more on root exudation during stand development.