Effects of wood-ash application on potential carbon and nitrogen mineralisation at two forest sites with different tree species,climate and N status

In the future it may become common practice to return wood-ash to forest ecosystems in order to replenish nutrients removed when brash has been extracted as a source of bioenergy. Wood-ash contains most of the nutrients that are present in the brash before its removal and burning, with the important exception of nitrogen (N). In the present paper we report measurements of CO₂ emissions and net N mineralisation in the humus layer and the upper 5 cm of mineral soil 12 years after the application of wood-ash to two study sites, representing different tree species, climatic conditions and N deposition histories. We hypothesized that application of wood-ash would increase both carbon (C) and net N mineralisation rates at Torup, an N-rich site with Norway spruce (Picea abies (L.) Karst.) in the south, whereas the net N mineralisation rates would not be affected at Vindeln, an N-poor site with Scots pine (Pinus sylvestris L.) in the north, where a possible N-limitation would restrict any N mineralisation. The treatments, comprising additions of 0, 1, 3 or 6 Mg of granulated wood-ash ha⁻¹, were applied in a randomised block design, replicated three times. Wood-ash from the same batch was used for all treatments at both sites. All factors were measured under laboratory conditions with controlled temperature and moisture levels. The potential CO₂ emissions (kg ha⁻¹ year⁻¹ of CO₂–C) at Torup were significantly higher in the 3 and 6 Mg ha⁻¹ treatments than in the control treatment, and the highest application resulted in an extra loss of 0.5 Mg ha⁻¹ of soil C annually as compared to the control. No such differences were detected at Vindeln. The results suggest that wood-ash application can deplete soil organic C at locations with similar characteristics (N-rich soil, spruce dominated, warm climate) as at Torup in this study.     

杉木、马尾松等不同树种组碳储量与碳密度研究

以新化县森林资源为研究对象,基于2014年新化县森林资源二类调查数据,借助Arcgis空间分析,利用生物量转换因子连续函数法计算出不同树种组的碳储量以及碳密度。结果表明:(1)各树种组碳储量的大小排序为:杉木组马尾松组竹木组柏木组慢生阔叶树组中生阔叶树组灌木组国外松组果树组速生阔叶树组食用原料树种组药用树种组杨树组林化原料树种组;(2)各树种组碳密度的大小排序为:中生阔叶树组速生阔叶树组柏木国外松组竹木组杨树组杉木组慢生阔叶树组马尾松组果树组=食用原料树种组=林化原料树种组灌木组药用树种组。     

Radiation-use efficiency of a forest exposed to elevated concentrations of atmospheric carbon dioxide

We compared radiation-use efficiency of growth (epsilon;), defined as rate of biomass accumulation per unit of absorbed photosynthetically active radiation, of forest plots exposed to ambient (approximately 360 micro l l-1) or elevated (approximately 560 micro l l-1) atmospheric CO2 concentration ([CO2]). Large plots (30-m diameter) in a loblolly pine (Pinus taeda L.) plantation, which contained several hardwood species in the understory, were fumigated with a free-air CO2 enrichment system. Biomass accumulation of the dominant loblolly pines was calculated from monthly measurements of tree growth and site-specific allometric equations. Depending on the species, leaf area index (L*) was estimated by three methods: optical, allometric and litterfall. Based on the relationship between tree height and diameter during the first 3 years of exposure, we conclude that elevated [CO2] did not alter the pattern of aboveground biomass allocation in loblolly pine. There was considerable variation in L* estimates by the different methods; total L* was 18-42% lower when estimated by the optical method compared with estimates from allometric calculations, and this discrepancy was reduced when optical measurements were corrected for the non-random distribution of loblolly pine foliage. The allometric + litterfall approach revealed a seasonal maximum total L* of 6.2-7.1 with about 1/3 of the total from hardwood foliage. Elevated [CO2] had only a slight effect on L* in the first 3 years of this study. Mean epsilon; (+/- SD), calculated for loblolly pine only, was 0.49 +/- 0.05 and 0.62 +/- 0.04 g MJ-1 for trees in the ambient and elevated [CO2] plots, respectively. The 27% increase in epsilon; in response to CO2 enrichment was caused primarily by the stimulation of biomass increment, as there was only a small effect of elevated [CO2] on L* during the initial years of fumigation. Long-term increases in atmospheric [CO2] can increase epsilon; in closed-canopy forests but the absolute magnitude and duration of this increase remain uncertain.     

Atmospheric carbon dioxide enrichment reduces carbohydrate and nitrogen reserves in overwintering Picea mariana

Abstract

Elevated levels of atmospheric carbon dioxide (CO₂) can directly affect the cold hardening process in evergreens through their effect on the accumulation of carbon and nitrogen reserves. This study investigated the biochemical responses of black spruce [Picea mariana (Mill.) B.S.P.] seedlings to CO₂ enrichment during growth, cold hardening and dehardening. Seedlings were grown under 350 (ambient) or 710 (elevated) ppm of CO₂ for 12 months in eight mini-greenhouses. Photoperiod and temperature were gradually lowered in autumn to induce cold hardening, and the conditions were reversed in spring to promote dehardening. At regular intervals, cold tolerance was assessed and sugars, starch and amino acid concentrations were measured. The freezing tolerance differed between the two treatments only in early autumn, with seedlings growing under high CO₂ being more tolerant. The northern ecotype was more cold tolerant with concomitant higher concentrations of sucrose, fructose, pinitol, glucose and total soluble sugars. The concentration of soluble sugars increased in needles and roots of black spruce along with cold hardening, and the concentrations of the cryoprotective sugars sucrose and raffinose were lower under elevated CO₂. Amino acid concentrations were also lower under elevated than under ambient CO_2. The lower level of reserve did not translate into a lower level of freezing tolerance.     

Carbon dioxide exchange in Norway spruce at the shoot, tree and ecosystem scale

Net CO2 exchange in a 35-year-old boreal Norway spruce (Picea abies (L.) Karst.) forest in northern Sweden was measured at the shoot (NSE), tree (NTE) and ecosystem levels (NEE) by means of shoot cuvettes, whole-tree chambers and the eddy covariance technique, respectively. We compared the dynamics of gross primary production (GPP) at the three levels during the course of a single week. The diurnal dynamics of GPP at each level were estimated by subtracting half-hourly or hourly model-estimated values of total respiration (excluding light-dependent respiration) from net CO(2) exchange. The relationship between temperature and total respiration at each level was derived from nighttime measurements of NSE, NTE and NEE over the course of 1 month. There was a strong linear relationship (r2 = 0.93) between the hourly estimates of GPP at the shoot and tree levels, but the correlation between shoot- and ecosystem-level GPP was weaker (r2 = 0.69). However, the correlation between shoot- and ecosystem-level GPP was improved (r2 = 0.88) if eddy covariance measurements were restricted to periods when friction velocity was > or = 0.5 m s(-1). Daily means were less dependent on friction velocity, giving an r2 value of 0.94 between shoot- and ecosystem-level GPP. The correlation between shoot and tree levels also increased when daily means were compared (r2 = 0.98). Most of the measured variation in carbon exchange rate among the shoot, tree and ecosystem levels was the result of periodic low coupling between vegetation and the atmosphere at the ecosystem level. The results validate the use of measurements at the shoot and tree level for analyzing the contribution of different compartments to net ecosystem CO2 exchange.     

Photosynthetic responses of forest understory tree species to long-term exposure to elevated carbon dioxide concentration at the Duke Forest FACE experiment

We examined the photosynthetic responses of four species of saplings growing in the understory of the Duke Forest FACE experiment during the seventh year of exposure to elevated CO2 concentration ([CO2]). Saplings of these same species were measured in the first year of the Duke Forest FACE experiment and at that time showed only seasonal fluctuations in acclimation of photosynthesis to elevated [CO2]. Based on observations from the Duke Forest FACE experiment, we hypothesized that after seven years of exposure to elevated [CO2] significant photosynthetic down-regulation would be observed in these tree species. To test our hypothesis, photosynthetic CO2-response and light-response curves, along with chlorophyll fluorescence, chlorophyll concentration and foliar N were measured twice during the summer of 2003. Exposure to elevated [CO2] continued to increase photosynthesis in all species measured after seven years of treatment with the greatest photosynthetic increase observed near saturating irradiances. In all species, elevated [CO2] increased electron transport efficiency but did not significantly alter carboxylation efficiency. Quantum yield estimated by light curves, chlorophyll concentration, and foliar nitrogen concentrations were unaffected by elevated [CO2]. Contrary to our hypothesis, there is little evidence of progressive N limitation of leaf-level processes in these understory tree species after seven years of exposure to elevated [CO2] in the Duke Forest FACE experiment.     

Carbon dioxide exchange of a larch forest after a typhoon disturbance

A typhoon event catastrophically destroyed a 45-year-old Japanese larch plantation in southern Hokkaido, northern Japan in September 2004, and about 90% of trees were blown down. Vegetation was measured to investigate its regeneration process and CO₂ flux, or net ecosystem production (NEP), was measured in 2006–2008 using an automated chamber system to investigate the effects of typhoon disturbance on the ecosystem carbon balance. Annual maximum aboveground biomass (AGB) increased from 2.7 Mg ha⁻¹ in 2006 to 4.0 Mg ha⁻¹ in 2007, whereas no change occurred in annual maximum leaf area index (LAI), which was 3.7 m² m⁻² in 2006 and 3.9 m² m⁻² in 2007. Red raspberry (Rubus idaeus) had become dominant within 2 years after the typhoon disturbance, and came to account for about 60% and 50% of AGB and LAI, respectively. In comparison with CO₂ fluxes measured by the eddy covariance technique in 2001–2003, for 4.5 months during the growing season, the sum of gross primary production (GPP) decreased on average by 739 gC m⁻² (64%) after the disturbance, whereas ecosystem respiration (RE) decreased by 501 gC m⁻² (51%). As a result, NEP decreased from 159 ± 57 gC m⁻² to −80 ± 30 gC m⁻², which shows that the ecosystem shifted from a carbon sink to a source. Seasonal variation in RE was strongly correlated to soil temperature. The interannual variation in the seasonal trend of RE was small. Light-saturated GPP (P_max) decreased from 30–45 μmol m⁻² s⁻¹ to 8–12 μmol m⁻² s⁻¹ during the summer season through the disturbance because of large reduction in LAI.     

Photosynthetic responses to understory shade and elevated carbon dioxide concentration in four northern hardwood tree species

Seedling responses to elevated atmospheric CO(2) concentration ([CO(2)]) and solar irradiance were measured over two growing seasons in shade-tolerant Acer saccharum Marsh. and Fagus grandifolia J.F. Ehrh. and shade-intolerant Prunus serotina, a J.F. Ehrh. and Betula papyrifera Marsh. Seedlings were exposed to a factorial combination of [CO2] (ambient and elevated (658 micromol mol-1)) and understory shade (deep and moderate) in open-top chambers placed in a forest understory. The elevated [CO(2)] treatment increased mean light-saturated net photosynthetic rate by 63% in the shade-tolerant species and 67% in the shade-intolerant species. However, when measured at the elevated [CO(2)], long-term enhancement of photosynthesis was 10% lower than the instantaneous enhancement seen in ambient-[CO(2)]-grown plants (P < 0.021). Overall, growth light environment affected long-term photosynthetic enhancement by elevated [CO(2)]: as the growth irradiance increased, proportional enhancement due to elevated [CO(2)] decreased from 97% for plants grown in deep shade to 47% for plants grown in moderate shade. Results suggest that in N-limited northern temperate forests, trees grown in deep shade may display greater photosynthetic gains from a CO(2)-enriched atmosphere than trees growing in more moderate shade, because of greater downregulation in the latter environment. If photosynthetic gains by deep-shade-grown plants in response to elevated [CO(2)] translate into improved growth and survival of shade-intolerant species, it could alter the future composition and dynamics of successional forest communities.     

Projections of regional changes in forest net primary productivity for different tree species in Europe driven by climate change and carbon dioxide

? Context

Projecting changes in forest productivity in Europe is crucial for adapting forest management to changing environmental conditions.

? Aims

The objective of this paper is to project forest productivity changes under different climate change scenarios at a large number of sites in Europe with a stand-scale process-based model.

? Methods

We applied the process-based forest growth model 4C at 132 typical forest sites of important European tree species in ten environmental zones using climate change scenarios from three different climate models and two different assumptions about CO₂ effects on productivity.

? Results

This paper shows that future forest productivity will be affected by climate change and that these effects depend strongly on the climate scenario used and the persistence of CO₂ effects. We find that productivity increases in Northern Europe, increases or decreases in Central Europe, and decreases in Southern Europe. This geographical pattern is mirrored by the responses of the individual tree species. The productivity of Scots pine and Norway spruce, mostly located in central and northern Europe, increases while the productivity of Common beech and oak in southern regions decreases. It is important to note that we consider the physiological response to climate change excluding disturbances or management.

? Conclusions

Different climate change scenarios and assumptions about the persistence of CO₂ effects lead to uncertain projections of future forest productivity. These uncertainties need to be integrated into forest management planning and adaptation of forest management to climate change using adaptive management frameworks.     

Carbon stock estimation for tree species of Sem Mukhem sacred forest in Garhwal Himalaya, India

Carbon stock estimation was conducted in tree species of Sem Mukhem sacred forest in district Tehri of Garhwal Himalaya, Uttarakhand, India. This forest is dedicated to Nagraj Devta and is dominated by tree species, including Quercus floribunda, Quercus semecarpifolia and Rhododendron arboreum. The highest values of below ground biomass density, total biomass density and total carbon density were (34.81±1.68) Mg·ha^?1, (168.26±9.04) Mg·ha^?1 and (84.13±4.18) Mg·ha^?1 for Pinus wallichiana. Overall values of total biomass density and total carbon density calculated were 1549.704 Mg·ha^?1 and 774.77 Mg·ha^?1 respectively. Total value of growing stock volume density for all species was 732.56 m³·ha^?1 and ranged from (144.97±11.98) m³·ha^?1 for Pinus wallichiana to (7.78±1.78) m³·ha^?1 for Benthamidia capitata.     

Influence of tree species on carbon and nitrogen transformation patterns in forest floor profiles

• Background   

Among forest management practices, forest tree species substitution influences biogeochemical cycles and soil interactions rapidly (decades) and significantly.     

湖南省现有森林植被主要树种的碳含量

探讨了湖南省现有森林植被17种树种(杉木、马尾松、湿地松、柏木、乐昌含笑、红花木莲、樟树、桢楠、甜槠、青冈栎、木荷、杜英、山矾、枫香、拟赤杨、杨树、毛竹)各器官的碳含量及其各器官碳含量的算术平均值。结果表明:同一树种不同器官碳含量差异不显著,不同树种各器官碳含量由高至低的排序不完全一致,不同树种同一器官或同一树种不同器官碳含量算术平均值存在一定的差异;针叶树、常绿阔叶树、落叶阔叶树和毛竹各器官碳含量(g·g-1)的变化范围分别为0.491~0.566,0.421~0.549,0.449~0.550,0.470~0.496,各树种种内各器官碳含量算术平均值在0.486~0.551 g·g-1之间变化,柏木最高,毛竹最低;针叶树碳含量高于阔叶树、毛竹,各树种树干碳含量普遍较高于其它各器官,变化范围在0.493~0.556 g·g-1之间,地上部分碳含量普遍高于相应树种的地下部分;17种树种各器官碳含量的算术平均值为0.504 g·g-1。     

Carbon and nitrogen in forest floor and mineral soil under six common European tree species

The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades after planting the six tree species had different profiles in terms of litterfall, forest floor and mineral soil C and N attributes. Three groups were identified: (1) ash, maple and lime, (2) beech and oak, and (3) spruce. There were significant differences in forest floor and soil C and N contents and C/N ratios, also among the five deciduous tree species. The influence of tree species was most pronounced in the forest floor, where C and N contents increased in the order ash = lime = maple < oak = beech ? spruce. Tree species influenced mineral soil only in some of the sampled soil layers within 30 cm depth. Species with low forest floor C and N content had more C and N in the mineral soil. This opposite trend probably offset the differences in forest floor C and N with no significant difference between tree species in C and N contents of the whole soil profile. The effect of tree species on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N, and mineral soil N status. Forest floor and litterfall C/N ratios were not related, whereas the C/N ratio of mineral soil (0–30 cm) better indicated N status under deciduous species on rich soil. The results suggest that European deciduous tree species differ in C and N sequestration rates within forest floor and mineral soil, respectively, but there is little evidence of major differences in the combined forest floor and mineral soil after three decades.     

Seedling biomass allocation and vital rates of cloud forest tree species: Responses to light in shade house conditions

Patterns of above- and below-ground biomass allocation in seedlings of nine common cloud forest (CF) tree species of western Mexico were examined under varying controlled light conditions using artificial shade houses. We analysed the relationships between vital rates (growth and survival) and four morphological traits (SLA, biomass allocation to stems, leaves and roots). We hypothesised that these traits represent differentiation axes in the way seedlings face the heterogeneous light regime typical of the CF understorey. For all species, traits between the different light levels, i.e. allocation to leaves, roots and stems differed among light levels. Five species had the largest SLA in the lowest light levels at the end of the experiment (Citharexylum, Dendropanax, Fraxinus, Quercus and Magnolia). Juglans was the only species with a large SLA at the highest light level (377.47 cm² g⁻¹). In contrast, light levels did not cause any significant variation in SLA of Persea and Simplococarpon at the end of the experiment. The relative height growth rates (RHGR) of the seedlings of five species were significantly different between light levels (P < 0.05). Overall, all species grew better in the highest light levels. The RHGR of three species were correlated positively with SLA. In turn, allocation to stem, leaves and root biomass were strongly correlated with the RHGR of five species (e.g. Citharexylum, Dendropanax and Fraxinus). Survival did not vary significantly between treatments in any species, only in the case of Simplococarpon (P < 0.05) and was correlated with all morphological variables. For this species, Peto and Peto's test showed a significantly larger survival of seedlings in the highest light level. The mean responses of these species based on all traits to the controlled light variation did not differed significantly. Our results show that these species display a wide range of resource allocation patterns when exposed to the varying light conditions that may be found in the forest understorey and highlight the role of morphological traits in this variation.     

Patterns of root respiration rates and morphological traits in 13 tree species in a tropical forest

The root systems of forest trees are composed of different diameters and heterogeneous physiological traits. However, the pattern of root respiration rates from finer and coarser roots across various tropical species remains unknown. To clarify how respiration is related to the morphological traits of roots, we evaluated specific root respiration and its relationships to mean root diameter (D) of various diameter and root tissue density (RTD; root mass per unit root volume; gcm(-3)) and specific root length (SRL; root length per unit root mass; mg(-1)) of the fine roots among and within 14 trees of 13 species from a primary tropical rainforest in the Pasoh Forest Reserve in Peninsular Malaysia. Coarse root (2-269mm) respiration rates increased with decreasing D, resulting in significant relationships between root respiration and diameter across species. A model based on a radial gradient of respiration rates of coarse roots simulated the exponential decrease in respiration with diameter. The respiration rate of fine roots (<2mm) was much higher and more variable than those of larger diameter roots. For fine roots, the mean respiration rates for each species increased with decreasing D. The respiration rates of fine roots declined markedly with increasing RTD and increased with increasing SRL, which explained a significant portion of the variation in the respiration among the 14 trees from 13 species examined. Our results indicate that coarse root respiration in tree species follows a basic relationship with D across species and that most of the variation in fine root respiration among species is explained by D, RTD and SRL. We found that the relationship between root respiration and morphological traits provides a quantitative basis for separating fine roots from coarse roots and that the pattern holds across different species.     

Variation in wood density and carbon content of tropical plantation tree species from Ghana

Most research on carbon content of trees has focused on temperate species, with less information existing for tropical trees and very little for tropical plantations. This study investigated factors affecting the carbon content of nineteen tropical plantation tree species of ages seven to twelve and compared carbon content of Khaya species from two ecozones in Ghana. For all sample trees, volume of the main stem, wood density, wood carbon (C) concentration and C content were determined. Estimated stem volume for the 12-year-old trees varied widely among species, from 0.01 to 1.04 m³, with main stem C content ranging from 3 to 205 kg. Wood density among species varied from 0.27 to 0.76 g cm^?3, with faster growing species exhibiting lower density. Significant differences in wood density also occurred with position along the main stem. Carbon concentration also differed among tree species, ranging from 458 to 498 g kg^?1. Differences among species in main stem C content largely reflected differences among species in estimated main stem volume, with values modified somewhat by wood density and C concentration. The use of species-specific wood density values was more important for ensuring accurate conversion of estimated stem volumes to C content than was the use of species-specific C concentrations. Significant differences in wood density did exist between Khaya species from the wet and moist semi-deciduous ecozones, suggesting climatic and site factors may also need to be considered. Wood densities for these plantation grown trees were lower than literature values reported for the same species in natural forests, suggesting that the application of data derived from natural forests could result in overestimation of the biomass and C content of trees of the same species grown in plantations.     

Effect of tree species on carbon stocks in forest floor and mineral soil and implications for soil carbon inventories

Forest soil organic carbon (SOC) and forest floor carbon (FFC) stocks are highly variable. The sampling effort required to assess SOC and FFC stocks is therefore large, resulting in limited sampling and poor estimates of the size, spatial distribution, and changes in SOC and FFC stocks in many countries. Forest SOC and FFC stocks are influenced by tree species. Therefore, quantification of the effect of tree species on carbon stocks combined with spatial information on tree species distribution could improve insight into the spatial distribution of forest carbon stocks.We present a study on the effect of tree species on FFC and SOC stock for a forest in the Netherlands and evaluate how this information could be used for inventory improvement. We assessed FFC and SOC stocks in stands of beech (Fagus sylvatica), Douglas fir (Pseudotsuga menziesii), Scots pine (Pinus sylvestris), oak (Quercus robur) and larch (Larix kaempferi).FFC and SOC stocks differed between a number of species. FFC stocks varied between 11.1 Mg C ha⁻¹ (beech) and 29.6 Mg C ha⁻¹ (larch). SOC stocks varied between 53.3 Mg C ha⁻¹ (beech) and 97.1 Mg C ha⁻¹ (larch). At managed locations, carbon stocks were lower than at unmanaged locations. The Dutch carbon inventory currently overestimates FFC stocks. Differences in carbon stocks between conifer and broadleaf forests were significant enough to consider them relevant for the Dutch system for carbon inventory.     

Carbon dioxide exchange and growth of a pine plantation

The exchange of materials between the atmosphere and terrestrial ecosystems is important to an understanding of the cycling of essential elements, the deposition of materials from the atmosphere and the entrance of pollutants into the forest ecosystems. This paper reports the results of measurements of carbon dioxide exchange in a vigorously growing pine plantation. Measurement data were incorporated into a model used to estimate annual carbon dioxide exchange. The measured annual biomass accumulation in the same plantation was used to determine a carbon dioxide to biomass conversion efficiency. Carbon dioxide exchange was 10.5 t/ha and biomass accumulation was 4.5 t/ha. The conversion efficiency of carbon dioxide to biomass is about 25% less than the theoretical chemical conversion efficiency. Considering the possible errors in both the estimates, this is very good agreement.     

Extent,distribution and origin of non-native forest tree species in Europe

ABSTRACT

The management of non-native tree species in European forests has a long history, but the information on the current number and geographic distribution of these species in European forests is incomplete and scattered across various datasets. This study aims to perform an inventory of the most frequent non-native tree species growing in European forests and analyse their current extent, geographic distribution and geographic origin. Our results show that at least 150 non-native tree species are currently growing in European forests and provenance trials. The genera represented by largest number of species are Eucalyptus, Pinus, Acacia and Abies. Species growing at the largest areas are Robinia pseudoacacia (2.44 million ha), Eucalyptus globulus (1.46 million ha), Picea sitchensis (1.16 million ha) and Pseudotsuga menziesii (0.83 million ha). In total, non-native tree species in Europe are found in an area of approximately 8.54 million ha, or 4.0% of the European forest area, and the five most abundant species account for up to 77% of this area. The largest number of these 150 species were introduced from North America (71), followed by Asia (45) and Australia (20). North American species occupy by far the largest area.     

林木种源试验研究现状与展望

林木种源试验是为不同的立地条件选择最适宜的种源,对林木种源的区划及良种选育具有重要的科学指导意义。文章论述了林木种源试验的定义、分类以及国内外的研究进展,并分析了我国林木种源试验存在问题及对策,提出了我国林木遗传育种研究未来的努力方向。