Trees In Old-growth Forest Research Articles

Latitudinal variation and driving factors of above-ground carbon proportion of large trees in old-growth forests across China

Large trees play a vital role in forest carbon stocks, dominating the distribution of community biomass. However, climate change and deforestation are reducing large trees globally, resulting in regional differences in their contribution to carbon stocks. Here, we examined the latitudinal change pattern and drivers of large trees' contributions to stand carbon stocks. Above-ground carbon storage was calculated for 530 plots in old-growth forests across China. Linear regression was used to calculate latitudinal variation in the proportion of above-ground carbon in large trees (i.e., AGC proportion). Variance partitioning and multiple linear regression were used to calculate the relative importance of species diversity, stand structure, functional traits, and environmental factors to AGC proportion. The study found that AGC proportion decreased with increasing latitude, averaging at 64.44 %. Stand structure, particularly the coefficient of variation of DBH, was identified as the key drivers of the AGC proportion. The number of common species (Hill's 1D) had no direct effect on the AGC proportion, while wood density, maximum tree height, and leaf nitrogen-to‑phosphorus ratio showed negative effects. The mass-ratio effects on AGC proportion were stronger than diversity effects. Climate variables primarily affected the AGC proportion through stand variables. These results indicate that simultaneously managing high diversity and AGC proportion may pose challenges. Moreover, considering the substantial contribution of large trees to carbon stocks, their storage capacity and sensitivity to environmental changes exert significant control over forest carbon cycles. Therefore, preserving and enhancing the carbon sink function of old-growth forests in the face of climate change and disturbance may depend primarily on protecting existing large trees and soon-to-be large-diameter trees.

Variations in leaf water status and drought tolerance of dominant tree species growing in multi-aged tropical forests in Thailand

Large-scale abandoned agricultural areas in Southeast Asia resulted in patches of forests of multiple successions and characteristics, challenging the study of their responses to environmental changes, especially under climatic water stress. Here, we investigated seasonal variation in leaf water status and drought tolerance of dominant tree species in three multi-aged tropical forests, ranging from 5 to > 200 years old, with contrasting soil moisture in Thailand. Seasonal variation in leaf water status differed among the forests with trees in young and intermediate sites demonstrating larger differences between seasons than the old-growth forest. Although vulnerability to embolism curves revealed that trees in old-growth forest were potentially more sensitive to declining leaf water status than others, they were predicted to lose < 5% of their hydraulic capacity as opposed to 13% for the trees in the younger sites. Our results suggest that the responses to water stress of tree species in different forest ages greatly vary with a tendency of trees in younger sites to be more resilience than those in older sites. Such information would benefit the selection of tree species that could adapt well to specific environments, thus improving the strategies for managing forests of different ages under a warmer future.

Genetic Diversity, Structure and Effective Population Size of Old-Growth vs. Second-Growth Populations of Keystone and Long-Lived Conifer, Eastern White Pine (Pinus strobus): Conservation Value and Climate Adaptation Potential.

Whether old-growth (OG) forests have higher genetic diversity and effective population size, consequently higher conservation value and climate adaptive potential than second-growth (SG) forests, remain an unresolved issue. We have tested the hypothesis that old-growth forest tree populations have higher genetic diversity, effective population size (NE), climate adaptive potential and conservation value and lower genetic differentiation than second-growth forest tree populations, employing a keystone and long-lived conifer, eastern white pine (EWP; Pinus strobus). Genetic diversity and population structure of old-growth and second-growth populations of eastern white pine (EWP) were examined using microsatellites of the nuclear and chloroplast genomes and single nucleotide polymorphisms (SNPs) in candidate nuclear genes putatively involved in adaptive responses to climate and underlying multilocus genetic architecture of local adaptation to climate in EWP. Old-growth and second-growth EWP populations had statistically similar genetic diversity, inbreeding coefficient and inter-population genetic differentiation based on nuclear microsatellites (nSSRs) and SNPs. However, old-growth populations had significantly higher chloroplast microsatellites (cpSSRs) haploid diversity than second-growth populations. Old-growth EWP populations had significantly higher coalescence-based historical long-term NE than second-growth EWP populations, but the linkage disequilibrium (LD)-based contemporary NE estimates were statistically similar between the old-growth and second-growth EWP populations. Analyses of population genetic structure and inter-population genetic relationships revealed some genetic constitution differences between the old-growth and second-growth EWP populations. Overall, our results suggest that old-growth and second-growth EWP populations have similar genetic resource conservation value. Because old-growth and second-growth EWP populations have similar levels of genetic diversity in genes putatively involved in adaptive responses to climate, old-growth, and second-growth populations may have similar adaptive potential under climate change. Our results could potentially be generalized across most of the boreal and temperate conifer forest trees. Our study contributes to address a long-standing issue, advances research field and knowledge about conservation and ecological and climate adaptation of forest trees.

Climate warming predispose sessile oak forests to drought-induced tree mortality regardless of management legacies

Climate warming-related drought could become a major driver of large-scale forest dieback. However, little is known about how past management legacies modulate the climate-growth responses during recent dieback episodes in central European oak forests. Here, we examine the role played by past management –unmanaged old-growth vs. managed forests– in recent tree mortality events occurring in Quercus petraea (Matt.) Liebl. stands across large areas of western Romania. We analyze how stand structure (tree size, competition) and climatic factors (drought, temperature and precipitation) drive tree radial growth patterns in neighboring standing dead and living trees. We analyzed basal area increments (BAI) trends, past management legacies and climate- and drought-growth relationships during the 20th century to distinguish the roles and interactions on recent warming-induced dieback. We observed that temperature rises and changes in atmospheric water demand during growing season let to increasing drought stress during the late 20th century affecting both managed and unmanaged forests. Dead trees from old-growth and managed forests showed lower growth than living trees after dieback onset. In both forests, dead and living trees displayed divergent growth patterns after dry 1980s, indicating that dieback was triggered by severe extreme conditions. Dead trees from managed stands experienced significant stronger growth reductions after 1980s though they experienced less tree-to-tree competition than dead trees in old-growth forest. High stand density negatively drove growth and enhanced climate sensitivity in old-growth stands. Competition acted synergistically with climate warming and drought causing tree mortality regardless of the management legacies in of Q. petraea forests. Our retrospective assessment of growth rates in relation with climate and structure changes offers valuable information for further forest conservation and management decisions of Q. petraea forests. These findings highlight the importance of past uses legacies driving recent forest dieback in temperate oak forests, making them more vulnerable under forecasted climate-warming related droughts in central Europe.

Bacidiaalbogranulosa (Ramalinaceae, lichenized Ascomycota), a new sorediate lichen from European old-growth forests.

A sterile sorediate member of the genus Bacidia s.str., B.albogranulosa, is described here as a new species. It is characterised by its very thin, pale grey thallus, white, farinose to granular soredia, the production of atranorin and the absence of ascomata and pycnidia. It grows on slightly acidic to subneutral bark of broad-leaved trees in old-growth forests in the Czech Republic, Poland, Ukraine and Russia (European part of the Caucasus). The new species is well characterised by its morphology, secondary chemistry and molecular (nrITS, mtSSU) traits. It is closely related to other atranorin-containing species in the genus, Bacidiadiffracta, B.polychroa and B.suffusa.

Spatial aspects of tree mortality strongly differ between young and old-growth forests.

Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially autocorrelated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a three-decade record of tree mortality from replicated mapped permanent plots located in young (< 60-year-old) and old-growth (> 300-year-old) Abies amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strongly density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatially aggregated, but was density independent and did not change the spatial pattern of surviving trees. These results extend current theory by demonstrating that density-dependent competitive mortality leading to increasingly uniform tree spacing in young forests ultimately transitions late in succession to a more diverse tree mortality regime that maintains spatial heterogeneity through time.

Conservation of tropical forest tree species in a native timber plantation landscape

Tropical terrestrial environments are becoming dominated by anthropogenic land-uses, making retention of biodiversity in production landscapes of critical conservation importance. Native timber plantations may represent a land-use capable of balancing production and conservation by potentially supporting understorey plant and tree species otherwise restricted to old-growth forests, with little impact on yield. In this study we investigated the conservation value of native plantation forests in the lowlands of New Britain, Papua New Guinea. We compared the composition of tree species (⩾10cm DBH) of unlogged forest to those of different aged native Eucalyptus deglupta plantations and intervening (historically logged) secondary forests. We found a high capacity for biodiversity conservation within plantations, with 70% of forest tree species persisting in mature plantations (13–15years old). However, compositional analyses revealed lower numbers of large individuals (⩾10cm DBH) in both late-successional and non-vertebrate-dispersed species in the plantations, indicating the difficulty of retaining mature old-growth forest trees in production land-uses. Secondary forest protected by conservation reserves was compositionally indistinct to unlogged forest. Our results demonstrate the potential for tropical native timber plantations to contribute to the retention of biodiversity. However, appropriate management is required to ensure the persistence of source populations of old-growth forest tree species. With careful planning a balance between production and conservation can be achieved in lowland tropical regions.

Is randomized branch sampling suitable to assess wood volume of temperate broadleaved old-growth forests?

Old-growth forests are characterized by the presence of large and very large trees. The estimation of their wood volume and biomass is essential in order to monitor the ecological processes in these stands and their contribution to carbon cycle. However, conventional wood volume estimation techniques based on mensuration of stem diameter at breast height and tree height is most often unfeasible for large and very large trees in old-growth forests because volume models or tables are usually elaborated from trees of smaller size grown up in regularly managed forest stands. Random Branch Sampling (RBS) is often proposed as a possible estimation alternative under such conditions. Starting from the ground level some of the parts of the main trunk and of the branches are sampled and measured to estimate the overall wood volume (or other biophysical variables). The application of RBS in old-growth forests, where tree cutting is usually forbidden or very difficult, requires that the crown of the tree can physically be reached to measure the sampled parts. We argue that under such conditions it is usually preferable to fully measure all the components of the tree crown because RBS estimates are not precise if based on only one sampling path and that, on the other hand, measuring the main trunk and all the branches by tree-climbing consumes the same time as replicating several RBS paths on the same tree. To demonstrate our hypothesis we selected 16 large beech trees located in the old-growth forest of Mount Cimini in Central Italy. Using a modern tree-climbing approach the main trunk and all the branches were measured and recorded in the field. The database was used to simulate RBS paths. Real values from volume census were contrasted with estimates based on RBS. On the whole, RBS estimates based on one single path prove to be highly imprecise. Even for trees characterized by a rather regular form, at least three RBS paths should be repeated on the same tree to maintain the relative standard error under or near 15%. This paper introduces the problem and describes the experimental test. The results are discussed under the perspective of standardized application of the proposed methodology.

Genetic succession and spatial genetic structure in a natural old growth Cryptomeria japonica forest revealed by nuclear and chloroplast microsatellite markers

Spatial genetic structure and diversity of Cryptomeria japonica trees in old growth forest but selectively logged in approximately 300 years ago were analyzed using seven nuclear microsatellite markers and one chloroplast microsatellite marker. The individuals were sampled from a 4-ha natural forest plot (200 m × 200 m), which are consisted of three size classes including newly regenerated individuals such as regenerated individuals (REG class; stem diameter at breast height (DBH), 5–110 cm), remaining individuals (REM class; DBH ≥ 110 cm), and old stumps. Genetic diversity was similar between the three groups. These results suggest that genes from the old growth forest may have been passed on to the next generation (i.e., the current forest). DNA extraction and analysis from old stumps was partly successful and we could compare the genetic diversity between old stumps and living trees using four microsatellite loci. Patterns of spatial genetic structure detected by analyses of the nuclear and chloroplast markers differed substantially; all nuclear markers showed significant positive autocorrelation ( P < 0.05) over short distances, but the chloroplast marker showed no significant autocorrelation over any distance. We concluded that Moran's I spatial autocorrelation pattern for the chloroplast microsatellite may have been influenced by the extensive pollen flow characteristic of this species, because chloroplast DNA of C. japonica is paternally inherited through pollen and is a wind-pollinated species that produces abundant pollen every few years. In contrast, Moran's I spatial autocorrelation pattern for nuclear microsatellites may reflect limited seed dispersal in gaps where the forest has regenerated and low levels of seed shadow overlap due to past logging. The average seed dispersal distance was 86.0 m at the study site and about 34.0% of the seeds were from the outside of the site, which revealed by parentage analysis. The individuals remaining after logging, and the extensive pollen flow from outside our study plot, may play important roles in maintaining the forests on this island. Gaps created by the selective logging activities appear to have been important for the regeneration of this species in the past but in the present time, natural disturbances such as typhoon and landslide are also important for gap creation.

Forest Fires and Old-Growth Forest Abundance in Wet, Cold, Engelmann Spruce – Subalpine Fir Forests of British Columbia, Canada

The amounts of old-growth forest present under current and pre-harvesting era disturbance regimes in the dominant higher elevation (900–2300 m) forests in eastern British Columbia (B.C.) – wet cold Engelmann spruce (Picea engelmannii Parry ex Engelm.) - subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forests (ESSFwc), and one important group of ESSFwc forests, the Northern Monashee (ESSFwc2) biogeoclimatic variant – were quantified using a GIS forest age database, with the assumption that oldgrowth forests were forests >140 years old. This was done in order to inform natural disturbance based management in this part of British Columbia. Database constraints restricted the analysis to the post 1800 period only and resulted in estimation of a range of old growth for any time period. The oldest trees in old-growth forests do not necessarily indicate when the forests were last disturbed by fire, as 14C dating of charcoal indicated that, for two of five 210- to 320-year old stands sampled, the most recent fire event probably occurred over 1000 years ago. The amount of old growth in both ESSFwc and ESSFwc2 forests, since 1800, decreased to a minimum in the mid to late 1800s, then increased. In the case of the ESSFwc2, this increase occurred until the 1960s before the amount of old growth decreased again. Amounts of old growth in 2003 (58–59% of the forested area) were within the pre-harvesting era range of 30–60% in ESSFwc2 forests, but may be above the range of 20–50% in ESSFwc forests. Old-growth forests have dominated most subalpine landscapes in eastern B.C. for at least the last several decades. If management of ESSFwc forests is to emulate historical disturbance regimes, greater protection of old-growth ESSFwc forests than at present will be necessary.

The effect of climate on the phenology, acorn crop and radial increment of pedunculate oak (Quercus robur) in the middle Volga region, Tatarstan, Russia

Our data, collected in the extreme east of Europe, show that a significant biological effect of climate change has been experienced even in territories where temperature increase has been the lowest. This study documents the climatic response of pedunculate oak (Quercus robur) growing near its north-eastern limits in Europe. It demonstrates the potential of oak trees in old-growth forest to act as proxy climate indicators. Many factors may influence the temporal stability of the growth-climate, acorn crop-climate and first leafing-climate relationships. Climate data, climatic fluctuations, reproduction, genetics and tree-age may relate to this instability. Our results stress that an increase in climate variability or climatic warming resulting from warmer winters or summers could affect the oak population in eastern Europe in a similar way to that in western Europe. These findings, from remnants of oak forest in the middle Volga region of Russia, allow a further understanding of how species could be affected by future climates.

Density-dependent mortality versus spatial segregation in early life stages of Abies densa and Rhododendron hodgsonii in Central Bhutan

In order to improve the understanding on the coexistence of rhododendron species and canopy trees in old growth forests with less anthropogenic influence, we studied the role of spatial segregation versus density-dependent mortality of regeneration of Abies densa and Rhododendron hodgsonii in Central Bhutan. The spatial patterns and the microsite preferences of A. densa and R. hodgsonii were studied on 12 permanent sample plots in 1996 and 2001 in Central Bhutan. We characterized survival of the two species on different microsites and tested for deviations of random mortality. Intraspecific spatial correlations were highly positive for individuals of both species in adjacent size classes. Higher positive intraspecific as compared to interspecific correlations suggested spatial segregation of patches of different species and of plants in different size classes. For A. densa seedlings, we detected density-independent mortality as a response to environmental heterogeneity. Spatial distribution of A. densa trees was random or overdispersed showing that in later life stages competition gets stronger. Seedlings of R. hodgsonii showed higher densities than seedlings of A. densa. Density-dependent mortality started at earlier life stages, when density in clumps was high. We found seedlings of both species on all microsites; temporal changes of percentages of seedlings on different microsites showed a similar trend with increases of seedlings on bryophyte mats and decreases on all other microsites. Decreases on litter and nurse logs, however, were much stronger for A. densa than for R. hodgsonii. R. hodgsonii was more frequent on nurse logs and showed better survival on this microsite. Survival of A. densa on nurse logs was low; nurse logs do not play an important role as safe site for A. densa in stands with an understory of R. hodgsonii. Percentages of R. hodgsonii established on litter showed only small decreases and were still higher than its spatial coverage. A. densa had seedlings in a seedling and sapling bank. Survival in a storage stage allows A. densa to outweigh the limitations of narrower regeneration niches and may, in combination with spatial segregation in early life stages, contribute to the coexistence of the two species.

Densities of large living and dead trees in old-growth temperate and boreal forests

We recorded and reviewed densities and basal areas of large living and dead trees in old-growth forest in Europe. Recorded densities were similar to those reported from old-growth forests in eastern North America, but lower than in northwestern North America. Based on our results we suggest that, 10–20 living trees per ha with dbh>70 cm may have been typical values for many central European and south Scandinavian virgin forests. In boreal forests, it was probably common with at least 20 living trees per ha with dbh>40 cm. Basal areas of living trees in mixed old-growth forests in central Europe and southern Sweden were 34–40 m 2 per ha on dry ground and about 60 m 2 per ha in wet alder–ash–spruce forests. Densities of large trees (dbh>40 cm) were twice as high in the latter forest type than on dry ground in Białowieża forest, Poland. Based on our results, we propose the following generalizations to be further tested in other old-growth temperate and boreal forests: 1. Among all standing trunks (including high stumps) about 10% are dead, but this proportion increases for the largest trees. The proportion of standing trees that are dead seem to be independent of total basal areas. Based on this, we suggest that the volume of dead wood is directly proportional to the productivity of old-growth forests. 2. Standing dead trees (snags) are on average larger than downed dead trees. Trees with dbh>40 cm often dominate the basal area and volume of standing dead trees and living trees. 3. About 30% (20–40%) of the basal area and volume of dead trees is standing in old-growth forests. This proportion seems to be independent of total volume of dead wood. Large disturbances by fire, strong winds and insects may temporarily change these proportions considerably in individual stands.

Restoring tropical forests on lands mined for bauxite: Examples from the Brazilian Amazon

Restoring self-sustaining tropical forest ecosystems on surface mined sites is a formidable challenge that requires the integration of proven reclamation techniques and reforestation strategies appropriate to specific site conditions, including landscape biodiversity patterns. Restorationists working in most tropical settings are usually hampered by lack of basic information on the wide variety of native tree species that characterize the pre-disturbance forests, as well as insufficient understanding of the ecology of disturbance and natural recovery to design effective restoration programs. A notable exception to this is the forest restoration program developed since the early 1980s by a Brazilian bauxite mining company operating at Trombetas in Pará State in central Amazonia. A systematic nursery and field research strategy was used to develop a reforestation program based on mixed plantings of more than 70 native old-growth forest tree species. This technique has been used to replant about 100 ha of deforested minelands each year over the past 15 years. Research in recent years has evaluated this approach and other, generally simpler, reforestation methods used at a smaller scale at this site. Post-plantation biodiversity development and other indicators of restoration success or sustainability were recorded. The results of these studies have shown the overwhelming importance of careful site preparation and topsoil handling/replacement practices in determining both future productivity and biodiversity of the redeveloping forests, irrespective of the complexity of the planting design used. The inclusion of a wide variety of forest species, particularly later successional species, was very important for long-range restoration owing to limitations on natural recovery processes that inhibit seed dispersal and subsequent colonization of many old-growth forest species. Many of the lessons learned at this site are applicable to improve the design of mineland rehabilitation and forest restoration programs worldwide.

Epiphyte Flora and Diversity on Basal Trunks of Six Old-Growth Forest Tree Species in Southern and Middle Boreal Finland

Epiphytic lichen and bryophyte species composition, richness and diversity were surveyed on basal trunks of six common old-growth forest tree species, Picea abies, Pinus sylvestris, Betula pendula, Alnus incana, Salix caprea and Populus tremula, in two old-growth forest areas, one in southern and one in middle boreal Finland. The average species numbers per tree ranged from 18 (Picea) to 27 (Salix) in the southern and from 20 (Populus) to 31 (Salix) in the middle boreal area. A few widespread habitat-generalist species, such as the foliose lichens Hypogymnia physodes and Platismatia glauca, were most abundant on all the tree species, except Populus. Most other epiphyte species showed at least a slight preference for one or two tree species. Populus proved to have the most distinct flora characterized by the abundance of certain, rather specialized crustose lichens and bryophytes. The number of species that occurred on only one tree species was highest on Populus (9) in the southern and on Alnus (18) in the middle boreal area. Differences in bark acidity and structure were the most likely explanations for the differences between tree species in the epiphytic flora and diversity. Salix and Populus were the most important of the tree species studied for the conservation of epiphyte diversity in the boreal forests of Finland.

EPIPHYTE FLORA AND DIVERSITY ON BASAL TRUNKS OF SIX OLD-GROWTH FOREST TREE SPECIES IN SOUTHERN AND MIDDLE BOREAL FINLAND

Epiphytic lichen and bryophyte species composition, richness and diversity were surveyed on basal trunks of six common old-growth forest tree species, Picea abies, Pinus sylvestris, Betula pendula, Alnus incana, Salix capreaand Populus tremula, in two old-growth forest areas, one in southern and one in middle boreal Finland. The average species numbers per tree ranged from 18 ( Picea) to 27 ( Salix) in the southern and from 20 ( Populus) to 31 ( Salix) in the middle boreal area. A few widespread habitat-generalist species, such as the foliose lichens Hypogymnia physodesand Platismatia glauca, were most abundant on all the tree species, except Populus. Most other epiphyte species showed at least a slight preference for one or two tree species. Populusproved to have the most distinct flora characterized by the abundance of certain, rather specialized crustose lichens and bryophytes. The number of species that occurred on only one tree species was highest on Populus(9) in the southern and on Alnus(18) in the middle boreal area. Differences in bark acidity and structure were the most likely explanations for the differences between tree species in the epiphytic flora and diversity. Salixand Populuswere the most important of the tree species studied for the conservation of epiphyte diversity in the boreal forests of Finland.