温带森林生态系统粗死木质物动态研究——以中美两个温带天然林生态系统为例

通过对我国长白山自然保护区红松针阔混交林和美国Andrews试验林异叶铁杉林的林木死亡量、粗死木质物(CWD)贮量、分解速率和它们在生态系统养分循环等方面动态研究表明,CWD是温带天然林生态系统的重要组成部分,它们在生态系统功能方面的重要性,因森林类型的不同而不尽相同,CWD在针叶林中比针阔混交林中更为重要。CWD在生态系统养分循环中的一个重要作用,很可能在于系统遭受重大外界扰动后,起到贮藏养分,增加系统稳定性的作用。未来全球森林凋落物C贮量估测时,应该包括CWD,否则将低估全球森林凋落物C贮量2.0—16×10~(13)kg,系统相对误差达2—10％。     

Characteristics in coarse woody debris mediated by forest developmental stage and latest disturbances in a natural secondary forest of Pinus tabulaeformis

Coarse woody debris (CWD) characteristics are expected to reflect forest stand features. Few studies evaluated logging-induced stand characteristics of secondary coniferous forests by quantifying the quality and quantity in CWD. After selective logging, the form of secondary forest of Pinus tabulaeformis in the Qinling Mountains is inferior and the regeneration is poor. We measured the CWD characteristics of the forest which had an average CWD biomass amount of 12.56 t hm⁻², and was predominated by abundant logs (65.68%), followed by snags (33.13%). The CWD biomass of P. tabulaeformis and Toxicodendron vernicifluum was significantly higher than that of other species, which took up 85.51% of the total. Although there was no significant difference among different diameter sizes (P > 0.05), the CWD biomass of diameter 30–40 cm occupied 46.26% of the total (5.81 t hm⁻²). Similarly, the CWD biomass of decay class I and II accounted for 39.89% (5.01 t hm⁻²) and 33.04% (4.15 t hm⁻²) of the total CWD biomass respectively, despite no significant difference among those 5 decay classes (P > 0.05). The results indicated that the combination of young forest developmental stage caused by past selective logging and natural and anthropogenic disturbances such as strong wind, tapping lacquer, firewood collection, and illegal tree felling played a crucial role in distribution characteristics of CWD in this secondary forest of P. tabulaeformis.     

Response of tree biomass and wood litter to disturbance in a Central Amazon forest

We developed an individual-based stochastic-empirical model to simulate the carbon dynamics of live and dead trees in a Central Amazon forest near Manaus, Brazil. The model is based on analyses of extensive field studies carried out on permanent forest inventory plots, and syntheses of published studies. New analyses included: (1) growth suppression of small trees, (2) maximum size (trunk base diameter) for 220 tree species, (3) the relationship between growth rate and wood density, and (4) the growth response of surviving trees to catastrophic mortality (from logging). The model simulates a forest inventory plot, and tracks recruitment, growth, and mortality of live trees, decomposition of dead trees (coarse litter), and how these processes vary with changing environmental conditions. Model predictions were tested against aggregated field data, and also compared with independent measurements including maximum tree age and coarse litter standing stocks. Spatial analyses demonstrated that a plot size of ~10 ha was required to accurately measure wood (live and dead) carbon balance. With the model accurately predicting relevant pools and fluxes, a number of model experiments were performed to predict forest carbon balance response to perturbations including: (1) increased productivity due to CO₂ fertilization, (2) a single semi-catastrophic (10%) mortality event, (3) increased recruitment and mortality (turnover) rates, and (4) the combined effects of increased turnover, increased tree growth rates, and decreased mean wood density of new recruits. Results demonstrated that carbon accumulation over the past few decades observed on tropical forest inventory plots (~0.5 Mg C ha^–1 year^–1) is not likely caused by CO₂ fertilization. A maximum 25% increase in woody tissue productivity with a doubling of atmospheric CO₂ only resulted in an accumulation rate of 0.05 Mg C ha^–1 year^–1 for the period 1980–2020 for a Central Amazon forest, or an order of magnitude less than observed on the inventory plots. In contrast, model parameterization based on extensive data from a logging experiment demonstrated a rapid increase in tree growth following disturbance, which could be misinterpreted as carbon sequestration if changes in coarse litter stocks were not considered. Combined results demonstrated that predictions of changes in forest carbon balance during the twenty-first century are highly dependent on assumptions of tree response to various perturbations, and underscores the importance of a close coupling of model and field investigations.     

The response of forest floor vegetation and tree regeneration to deer exclusion and disturbance in a riparian deciduous forest,central Japan

The response of forest floor vegetation and regeneration of major treespecies to deer exclusion in a riparian forest were studied for 3 years withtheinteractive effects of natural disturbances. At the start of this study, deerdensity had quickly increased to a fairly high level (29–31 individualskm^–2) during the last decade and had severely reduced theamount of forest floor vegetation in the study area. Dwarf bamboos, which weredominant before, had almost diminished from the forest floor. During the studyperiod, aboveground biomass increased steadily but species diversity did notchange much in the exclosures. Outside the exclosures, the seedlings of alltreespecies were damaged greatly by deer browsing, especially the taller ones. Deerbrowsing had little effect on the emergence of tree seedlings, but deertrampling might have accelerated emergence indirectly by disturbing the soilsurface for some species. Differences in plant responses were also observed fordeer browsing and the presence of dwarf bamboo that strongly inhibits therecruitment of tree seedlings. The nine major species were classified intothreegroups according to the response of seedlings to deer browsing and disturbance.Group 1 consists of the species whose seedling survival is affected bybrowsing,but seldom by disturbances (Phellodendron amurense,Kalopanax pictus, Quercus crispulaandMalus toringo). Groups 2 and 3 consist of species adaptedto tree-fall disturbance (Betula spp.) and ripariandisturbance (Alnus hirsuta var.sibirica, Ulmus davidiana var.japonica, Populus maximowiczii andSalix sachalinensis), respectively, and seedling survivalof these two groups is principally affected by light conditions. The effect ofdeer browsing on seedling survival and growth was greater for Group 2 than forGroup 3.     

Post‐clearcut dynamics of carbon,water and energy exchanges in a midlatitude temperate,deciduous broadleaf forest environment

Clearcutting and other forest disturbances perturb carbon, water, and energy balances in significant ways, with corresponding influences on Earth's climate system through biogeochemical and biogeophysical effects. Observations are needed to quantify the precise changes in these balances as they vary across diverse disturbances of different types, severities, and in various climate and ecosystem type settings. This study combines eddy covariance and micrometeorological measurements of surface‐atmosphere exchanges with vegetation inventories and chamber‐based estimates of soil respiration to quantify how carbon, water, and energy fluxes changed during the first 3 years following forest clearing in a temperate forest environment of the northeastern US. We observed rapid recovery with sustained increases in gross ecosystem productivity (GEP) over the first three growing seasons post‐clearing, coincident with large and relatively stable net emission of CO₂ because of overwhelmingly large ecosystem respiration. The rise in GEP was attributed to vegetation changes not environmental conditions (e.g., weather), but attribution to the expansion of leaf area vs. changes in vegetation composition remains unclear. Soil respiration was estimated to contribute 44% of total ecosystem respiration during summer months and coarse woody debris accounted for another 18%. Evapotranspiration also recovered rapidly and continued to rise across years with a corresponding decrease in sensible heat flux. Gross short‐wave and long‐wave radiative fluxes were stable across years except for strong wintertime dependence on snow covered conditions and corresponding variation in albedo. Overall, these findings underscore the highly dynamic nature of carbon and water exchanges and vegetation composition during the regrowth following a severe forest disturbance, and sheds light on both the magnitude of such changes and the underlying mechanisms with a unique example from a temperate, deciduous broadleaf forest.     

Effects of logging and coarse woody debris harvest on lepidopteran communities in the eastern deciduous forest of North America

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Study on canopy disturbance regime and mechanism of tree species diversity maintenance in the lower subtropical evergreen broad-leaved forest,South China

ABSTRACT

The canopy disturbance, the gap environment, gap regeneration and maintenance of tree species diversity in the lower subtropical evergreen broad-leaved forest (LSEBF) of South China were studied in this paper. The most common manner of gap formation in the forest was by stem breakage. Most gaps were formed by two gap makers. The sizes of most expanded gaps (EG) and canopy gaps (CG) were in the range of 100 – 300 m² and 50 – 100 m², respectively. The ecological factors in gaps were analysed on the basis of contrasting measurement of the microclimatic regimes in gaps of different sizes and in non-gap stands. Tree species in the LSEBF were classified into 5 ecological species groups on the bases of their changes in order of importance values in gaps and in non-gap stands. Most of the species reached their peak of regeneration density around the gap sizes of 100 m² and 500 m². The curves of regeneration density vs. gap age for major species revealed two types. Regeneration densities of most species, and species diversity indices in gaps were greater than those in non-gap stands.     

Community dynamics of Ogawa Forest Reserve,a species rich deciduous forest,central Japan

Forest community dynamics were studied for 4 years in a 6 ha permanent plot of species rich, old-growth, temperate deciduous forest in Ogawa Forest Reserve, central Japan. The gap formation rate, recruitment, mortality, gain and loss rate in basal area during 4 years were 42 m2 ha^–1 yr^–1, 1.74% yr^–1, 1.19% yr^–1, 1.12% yr^–1 and 0.88% yr^–1, respectively. The turnover time calculated from them ranged from 58 to 240 years. Both the mortality and mortality factors were size dependent; trees in middle size class had smallest mortality, and the proportion of the trees killed by disturbances increased with size. Gap creations were concentrated in a particular year, suggesting a large heterogeneity in time. Spatial distribution of recruited trees were biassed to the old gaps (older than 4 years), especially that of the species with Bell-shaped dbh distribution (shade intolerant) strongly associated with the gaps. Recruitment in tree stems and the loss of basal area, thus had the larger variability than mortality of stems and this forest, and the species with L-shaped dbh distribution seemed to going to increase the importance in the future if the present trend continues to be held. The turnover time of population is positively correlated with the maximum dbh size of the species, indicating the slow change of the population of large sized species.     

Leaching of dissolved organic carbon,dissolved organic nitrogen,and other solutes from coarse woody debris and litter in a mixed forest in New York State

Coarse woody debris (CWD) may play a role in nutrient cycling in temperate forests through the leaching of solutes, including dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), to the underlying soil. These fluxes need to be considered in element budget calculations, and have the potential to influence microbial activity, soil development, and other processes in the underlying soil, but studies on leaching from CWD are rare. In this study, we collected throughfall, litter leachate, and CWD leachate in situ at a young mixed lowland forest in NY State, USA over one year. We measured the concentrations of DOC, DON, NH₄⁺, NO₃⁻, dissolved organic sulfur, SO₄²⁻, Cl⁻, Al, Ca, K, Mg, Na, and P, estimated the flux of these solutes in throughfall, and measured the cover of CWD to gain some insight into possible fluxes from CWD. Concentrations of DOC were much higher in CWD leachate than in throughfall or litter leachate (15 vs. 0.7 and 1.6 mM, respectively), and greater than reported values for other leachates from within forested ecosystems. Other solutes showed a similar pattern, with inorganic N being an exception. Our results suggest that microsite scale fluxes of DOC from CWD may be An high relative to throughfall and litter leaching fluxes, but since CWD covered a relatively small fraction (2%) of the forest floor in our study, ecosystem scale fluxes from CWD may be negligible for this site. Soil directly beneath CWD may be influenced by CWD leaching, in terms of soil organic matter, microbial activity, and N availability. Concentrations of some metals showed correlations to DOC concentrations, highlighting the possibility of complexation by DOM. Several solute concentrations in throughfall, including DOC, showed positive correlations to mean air temperature, and fewer showed positive correlations in litter leachate, while negative correlations were observed to precipitation, suggesting both biological and hydrologic control of solute concentrations.     

小兴安岭谷地云冷杉林粗木质残体碳密度特征

以小兴安岭谷地云冷杉林9.12 hm~2固定样地为研究对象,分析粗木质残体(CWD)碳密度的基础特征,揭示其与林分因子和物种多样性的关系。结果表明:(1)谷地云冷杉林CWD碳密度为13.25 t C/hm~2,其中云杉(Picea spp.)、冷杉(Abies nephrolepis)、兴安落叶松(Larix gmelinii)和未知种的CWD碳密度分别为3.59、2.61、3.06和2.85 t C/hm~2。(2)不同腐烂等级下CWD碳密度呈近正态分布,多集中在Ⅱ和Ⅲ等级,分别占总量的42.7%和35.4%。不同径级的CWD碳密度也呈近正态分布,主要分布在30—40 cm和40—50 cm径级上。干中折断、拔根倒、枯立木和干基折断为谷地云冷杉林CWD碳密度的主要存在方式。腐烂等级为Ⅰ和Ⅴ的CWD中,拔根倒的碳密度最高,其他腐烂等级中均为干中折断的碳密度最高。(3)CWD碳密度表现出较强的空间异质性,其随着林分平均胸径、最大胸径和胸高断面积的增加而下降,呈显著负相关关系(P0.05);而与林分密度、多样性指数和均匀度指数均无显著相关性(P0.05)。     

Composition,structure and diversity of cove forest stands in the Great Smoky Mountains: a patch dynamics perspective

Abstract. Cove forests of the Great Smoky Mountains are North American examples of old-growth temperate forest. Ecological attributes of seven stands were studied using one 0.6 - 1.0 ha plot per stand. Stand basal area (39 - 55 m²/ha) and biomass (326 - 471 Mg/ha) were high for temperate deciduous forest. Density ranged from 577 to 1075 stems/ha. All stands had a mixture of deciduous canopy species. Only rarely did a single species comprise more than half of the stand by density, basal area or biomass. Shade-intolerant species were present at low levels (1 - 5 % of total stand density). A wide range of stem diameters was characteristic of most species. However, some species lacked small stems, indicating discontinuous regeneration. Stands tended to have 10 - 20 tree species per ha and at least five species had biomass levels > 10 Mg/ha, indicating high evenness. Canopy gaps covered 10 % of the total area (2 - 21 % by stand). Gaps and conspecific patches of canopy trees > 0.05 ha in size were infrequent. Spatial analyses revealed a variety of patterns among species at inter-tree distances of 1 to 25 m. When all species were combined, juveniles showed aggregation, and adults were often hyperdispersed. Analyses for individual species confirmed that the mosaic of canopy species is influenced by non-random spatial processes. Adults of several species were aggregated at distances > 10 m. Juveniles of all major species exhibited aggregation. Several species exhibited regeneration near conspecific adults. This pattern suggested limited mobility for such species within the shifting mosaic. A diverse patchwork resulted despite the fact that many species did not exhibit segregation of adults and juveniles. Further understanding of patch dynamics and the potential for compositional steady state in cove forests requires long-term study with spatial data.     

Population structure and spatial patterns for trees in a temperate old-growth evergreen broad-leaved forest in Japan

The population structure and spatial pattern of major tree species in a warm-temperate old-growth evergreen broad-leaved forest in the Tatera Forest Reserve of Japan were investigated. All stems 5 cm in diameter at breast height (DBH) were mapped on a 4 ha plot and analyses were made of population structure and the spatial distribution and spatial association of stems in different vertical layers for nine species. This was done in the context of scale dependency. The plot was located on a very gentle slope and 17.1% of its canopy layer was in gaps. It contained 45 woody plant species and 4570 living stems with a basal area of 63.9 m² ha^–1. Castanopsis cuspidata var. sieboldii, the most dominant species for the basal area, had the maximum DBH among the species present, fewer smaller stems and a lower coefficient of statistical skewness of the DBH distribution. The second most dominant species, Dystilium racemosum, had the highest stem density (410 ha^–1), more abundant smaller stems and a relatively higher coefficient of skewness. Most stems in different vertical layers showed a weakly aggregated distribution with loose colonies as basic units. Gap dependency for the occurrence of stems under the canopy layer was weak. Maximum slope degree of the plot also weakly affected the occurrence of stems. Spatial associations varied among intra- and interspecific cohorts in the different layers and spatial scales examined, and positive associations among cohorts were found more frequently as the scales examined became larger. This tendency suggests that key factors forming observed spatial associations might vary with the spatial scales.     

Recruitment and growth dynamics of a temperate forest understorey species following wildfire in southeast Australia

In southeast Australia, fire regimes are changing. Conserving species into the future under these changing fire regimes will require understanding their recruitment and growth dynamics following historical fires. Where monitoring is absent, dendroecology provides a tool for reconstructing and quantifying these dynamics. The use of dendroecology in southeast Australia has been limited due to presumptions that many of the species do not produce annual growth rings. In this study, we determined the dendroecological potential of a fire-sensitive understorey tree species, Pomaderris aspera, as a case study species, to explore the potential to use of understorey species to provide insights into past fire history. We used growth patterns of this species to understand the role of resource limitation on growth and senescence. We found that P. aspera had distinct growth rings and high within tree correlation when cross-dated.Recruitment events of this species aligned with three known fire events. We found that the impacts of historical fire on tree canopy cover could be estimated. P. aspera grew rapidly post fire and then become suppressed within 9–15 years. Cycles of growth release and suppression were found with increasing incidence of suppression occurring over time. Increased suppression and reduced growth rates aligned with patterns of recorded senescence over time in the understories of a maturing.Eucalyptus canopy. Our results highlight the potential to use dendroecology to confirm past fire extents and amount of canopy disturbances and the impacts that these events have on the recruitment and growth dynamics of understorey species in southeast Australia.     

Species diversity,susceptibility to disturbance and tree population dynamics in tropical rain forest

Abstract. In 1964 a census of all trees > 9.7 cm diameter at breast height (DBH) was conducted on 22 plots totalling 13.2 ha in lowland tropical evergreen rain forest on Kolombangara, Solomon Islands. Over the following 30 yr (1964–1994), populations of all individuals > 4.85 cm DBH of the 12 most common tree species and amounts of disturbance have been monitored on a declining number of these plots (in 1994, nine plots totalling 5.4 ha were still being recorded). Between November 1967 and April 1970, Kolombangara was struck by four cyclones, although only two of these caused substantial amounts of damage to the canopy structure. Multivariate analysis has identified six forest types on Kolombangara (Greig-Smith et al. 1967). The species richness and diversity of trees in the 1964 census, turnover rates of the populations monitored over 1964–1975, and the amount of disturbance sustained during a cyclone in 1970, were all positively correlated across five of the forest types. The sixth forest type was a consistent outlier in these analyses and is believed to have been seriously disturbed by humans about a century ago. The floristics, turnover and disturbance data support Connell's intermediate disturbance hypothesis. The most species-rich forest types contained a higher proportion of fast-growing individuals and species that are early-successional and which have low density timber. Properties of these species rendered them more susceptible to damage when struck by the 1970 cyclone. They showed higher turnover rates because disturbance-dependent species are also characterised by higher mortality and recruitment rates. Thus, periodic cyclones appear to favour the maintenance of differences in species diversity and composition between forest types.     

Effects of position, understorey vegetation and coarse woody debris on tree regeneration in two environmentally contrasting forests of north-western Patagonia: a manipulative approach

Aim To investigate the differential effects of position within gaps, coarse woody debris and understorey cover on tree seedling survival in canopy gaps in two old‐growth Nothofagus pumilio (Poepp. & Endl.) Krasser forests and the response of this species to gaps in two forests located at opposite extremes of a steep rainfall gradient. Location Nahuel Huapi National Park, at 41° S in north‐western Patagonia, Argentina. Methods In both study sites, seedlings were transplanted to experimental plots in gaps in three different positions, with two types of substrate (coarse woody debris or forest floor), and with and without removal of understorey vegetation. Survival of seedlings was monitored during two growing seasons. Soil moisture and direct solar radiation were measured once in mid‐summer. Seedling aerial biomass was estimated at the end of the experiment. Results Mid‐summer soil water potential was lowest in the centre of gaps, in plots where the understorey had been removed, and highest at the northern edges of gaps. Direct incoming radiation was highest in gap centres and southern edges, and lowest at northern edges. Seedling mortality was highest in gap centres, in both sites. Coarse woody debris had a positive effect on seedling survival during summer in the mesic forest and during winter in the xeric forest. The removal of understorey cover had negative effects in gap centres during summer. Seedling final aerial biomass was positively affected by understorey removal and by soil substrate in both sites. In the dry forest gaps, seedling growth was highest in northern edges, whereas it was highest in gap centres in the mesic forest. Overall growth was positively related to survival in the xeric forest, and negatively related in the mesic forest. Main conclusions Survival and growth were facilitated by the shade of gap‐surrounding trees only in the xeric forest. Understorey vegetation of both forests facilitated seedling survival in exposed microsites but competed with seedling growth. Nurse logs were an important substrate for seedling establishment in both forests; however, causes of this pattern differed between forests. Water availability positively controls seedling survival and growth in the xeric forest while in the mesic forest, survival and growth are differentially controlled by water and light availability, respectively. These two contrasting old‐growth forests, separated by a relatively short distance along a steep rainfall gradient, had different yet unexpected microenvironmental controls on N. pumilio seedling survival and growth. These results underscore the importance of defining microscale limiting factors of tree recruitment in the context of large‐scale spatial variation in resources.     

Biomass,production and woody detritus in an old coast redwood (<Emphasis Type="Italic">Sequoia sempervirens</Emphasis>) forest

We examined aboveground biomass dynamics, aboveground net primary production (ANPP), and woody detritus input in an old Sequoia sempervirens stand over a three-decade period. Our estimates of aboveground biomass ranged from 3300 to 5800 Mg ha⁻¹. Stem biomass estimates ranged from 3000 to 5200 Mg ha⁻¹. Stem biomass declined 7% over the study interval. Biomass dynamics were patchy, with marked declines in recent tree-fall patches <0.05 ha in size. Larger tree-fall patches approaching 0.2 ha in size were observed outside the study plot. Our estimates of ANPP ranged from 6 to 14 Mg ha⁻¹yr⁻¹. Estimates of 7 to 10 Mg ha⁻¹yr⁻¹ were considered to be relatively accurate. Thus, our estimates based on long-term data corroborated the findings of earlier short-term studies. ANPP of old, pure stands of Sequoia was not above average for temperate forests. Even though production was potentially high on a per stem basis, it was moderate at the stand level. We obtained values of 797 m³ ha⁻¹ and 262 Mg ha⁻¹ for coarse woody detritus volume and mass, respectively. Fine woody detritus volume and mass were estimated at 16 m³ ha⁻¹ and 5 Mg ha⁻¹, respectively. Standing dead trees (or snags) comprised 7% of the total coarse detritus volume and 8% of the total mass. Coarse detritus input averaged 5.7 to 6.9 Mg ha⁻¹yr⁻¹. Assuming steady-state input and pool of coarse detritus, we obtained a decay rate constant of 0.022 to 0.026. The old-growth stand of Sequoia studied had extremely high biomass, but ANPP was moderate and the amount of woody detritus was not exceptionally large. Biomass accretion and loss were not rapid in this stand partly because of the slow population dynamics and low canopy turnover rate of Sequoia at the old-growth stage. Nomenclature: Hickman (1993).     

Beta-diversity of lepidopteran larval communities in a Japanese temperate forest: effects of phenology and tree species

The specialization of herbivores among tree species is poorly understood despite its fundamental importance as a factor regulating diversity. To examine the effect of tree species on larval community structure, the larval communities in 10 temperate deciduous tree species that differed in leaf emergence pattern (flush- vs. intermediate-type) were seasonally surveyed. The newly developed soft, nitrogen-rich leaves of all species became tough and nitrogen-poor as the season progressed. Following the changes in leaf quality, two distinct seasonal lepidopteran larval communities emerged, with a marked turnover in early July. The beta diversity, or dissimilarity, of species composition in the larval communities among tree species was higher in summer than in spring. These results imply that the lepidopteran larval communities as a whole were supported by alpha diversity in spring and by beta diversity in summer, demonstrating that the plant diversity of this forest could support a caterpillar community. We examined the importance of spatio-temporal variations in leaf quality within and among tree species in promoting herbivore diversity, although other factors, such as tree species phylogeny and predators, may also have a large effect on lepidopteran larval communities.     

Long‐term effects of climate change on carbon storage and tree species composition in a dry deciduous forest

Forest vegetation and soils have been suggested as potentially important sinks for carbon (C) with appropriate management and thus are implicated as effective tools in stabilizing climate even with increasing anthropogenic release of CO₂. Drought, however, which is often predicted to increase in models of future climate change, may limit net primary productio (NPP) of dry forest types, with unknown effects on soil C storage. We studied C dynamics of a deciduous temperate forest of Hungary that has been subject to significant decreases in precipitation and increases in temperature in recent decades. We resampled plots that were established in 1972 and repeated the full C inventory by analyzing more than 4 decades of data on the number of living trees, biomass of trees and shrubs, and soil C content. Our analyses show that the decline in number and biomass of oaks started around the end of the 1970s with a 71% reduction in the number of sessile oak stems by 2014. Projected growth in this forest, based on the yield table's data for Hungary, was 4.6 kg C/m². Although new species emerged, this new growth and small increases in oak biomass resulted in only 1.9 kg C/m² increase over 41 years. The death of oaks increased inputs of coarse woody debris to the surface of the soil, much of which is still identifiable, and caused an increase of 15.5%, or 2.6 kg C/m², in the top 1 m of soil. Stability of this fresh organic matter input to surface soil is unknown, but is likely to be low based on the results of a colocated woody litter decomposition study. The effects of a warmer and drier climate on the C balance of forests in this region will be felt for decades to come as woody litter inputs decay, and forest growth remains impeded.     

Gap-phase dynamics and coexistence of a long-lived pioneer and shade-tolerant tree species in the canopy of an old-growth coastal temperate rain forest of Chiloé Island, Chile

Aim A major question with regard to the ecology of temperate rain forests in south‐central Chile is how pioneer and shade‐tolerant tree species coexist in old‐growth forests. We explored the correspondence between tree regeneration dynamics and life‐history traits to explain the coexistence of these two functional types in stands apparently representing a non‐equilibrium mixture. Location This study was conducted in northern Chiloé Island, Chile (41.6° S, 73.9° W) in a temperate coastal rain forest with no evidence of stand disruption by human impact. Methods We assessed stand structure by sampling all stems within two 50 × 20 m and four 5 × 100 m plots. A 600‐m long transect, with 20 uniformly spaced sampling points, was used to quantify seedling and sapling densities, obtain increment cores, and randomly select 10 tree‐fall gaps. We used tree‐ring analysis to assess establishment periods and to relate the influences of disturbances to the regeneration dynamics of the main canopy species. Results Canopy emergent tree species were the long‐lived pioneer Eucryphia cordifolia and the shade‐tolerant Aextoxicon punctatum. Shade‐tolerant species such as Laureliopsis philippiana and several species of Myrtaceae occupied the main canopy. The stem diameter distribution for E. cordifolia was distinctly unimodal, while for A. punctatum it was multi‐modal, with all age classes represented. Myrtaceae accounted for most of the small trees. Most tree seedlings and saplings occurred beneath canopy gaps. Based on tree‐ring counts, the largest individuals of A. punctatum and E. cordifolia had minimum ages estimated to be > 350 years and > 286 years, respectively. Shade‐tolerant Myrtaceae species and L. philippiana had shorter life spans (< 200 years). Most growth releases, regardless of tree species, were moderate and have occurred continuously since 1750. Main conclusions We suggest that this coastal forest has remained largely free of stand‐disrupting disturbances for at least 450 years, without substantial changes in canopy composition. Release patterns are consistent with this hypothesis and suggest that the disturbance regime is dominated by individual tree‐fall gaps, with sporadic multiple tree falls. Long life spans, maximum height and differences in shade tolerance provide a basis for understanding the long‐term coexistence of pioneer and shade‐tolerant tree species in this coastal, old‐growth rain forest, despite the rarity of major disturbances.