Carbon dioxide sequestration capability of an unmanaged old-growth broadleaf deciduous forest in a Strict Nature Reserve

The seasonal trend of plant carbon dioxide (CO₂) sequestration is related to the photosynthetic activity, which in turn changes in response to environmental conditions. Great interest has turned to the CO₂ sequestration (CS) potential of temperate forests which play an important role in global carbon (C) cycle contributing to the lowering of atmospheric CO₂ concentration. In such context, the CS of an unmanaged old broad-leaf deciduous forest developing inside a Strict Nature Reserve, and its variations during the year were analyzed considering the monthly variations of leaf area index (LAI) and net photosynthetic rates (N_P). Overall, the total yearly CS of the forest was 141 Mg CO₂ ha^?1 year^?1 with the highest CS value monitored in June (405 Mg CO₂ month^?1) due to the highest LAI (5.0 ± 0.8 m² m^?2) and a high N_P in all the broadleaf species. The first CS decline was observed in August due to the more stressful climatic conditions that constrained N_P rates. Overall, the total CS of the forest reflects the good ecological health of the ecosystem due to its conservative management.     

Allelopathic effect of larch leaching on ash growth in mixed forest

lntroductionConcerningthemechanismoftheinteractionbe-tWeentreespeciesinthelarch(LafisgmelinI)-ash(PraxiPusmandShuFbe)mixedforest,wehavestudiedtheaIIelopathiceff6ctsoftheIarchvolatilematter,litterandrootsecretion.onthegroWthofash.TheobtainedresultsshowedclearIythatthelarchvoIatiIematt6rplayedaninhibitivepart,andboththeIarchIitt6randrootsecretionpIayedanobviousfystimuIatingpaFtontheashgroWth(Wu2oooa,2ooob,2oooc).Thispapermakesastudyofanotherallelo-pathicway(Ieaching)betWeenlarchandash.T…     

燕山北部山地人工落叶松林与天然次生林物种多样性的比较

为了解燕山北部山地华北落叶松人工林植被物种多样性维持功能的高低,选取13a和30a生人工落叶松林,以13a和28a生天然次生杨桦林作为对照,对两种林分的植被多样性进行调查和分析,并研究了间伐对人工落叶松林植被物种多样性的影响。结果表明,林龄相同或相近的两种林分类型相比,无论是乔木层、灌木层或是草本层,人工落叶松林丰富度、Simpson指数、Shannon—Weiner指数均表现出相当或略高于天然次生杨桦林（30a生人工落叶松林乔木层多样性指数除外）;间伐对人工落叶松林植被物种多样性的短期影响主要体现在乔木层,对林下灌木层和草本层无明显影响。燕山北部山地人工落叶松林具有较高的植物多样性维持功能,没有导致物种多样性的降低。     

TMS天目丝增抗剂在落叶松育苗中的应用

应用2000,1000,500,250,125,62mLL-1TMS天目丝增抗剂对200株长白落叶松苗进行6小时浸根,在生长季节(5月30日至10月20日)对经过天目丝增抗剂处理的造林苗每隔15天测定一次苗木的高生长、地径、主根长度,侧根数。实验结果表明,天目丝增抗剂处理可以极大地促进长白山落叶松苗木生长并能提高苗木质量。500mLL-1TMS处理的苗木生长效果最好,与常规育苗相比,高生长平均增加42.5%,地径生长平均增加30.7%,主根长平均增加14.0%,侧根数平均增加31.6%;Ⅰ级苗和Ⅱ级苗各占一半,没有Ⅲ级苗,显著地提高了经济效益。表3参8。     

Influence of typhoon disturbances on the understory light regime and stand dynamics of a subtropical rain forest in northeastern Taiwan

In 1996 and 1997 we examined the effects of typhoon disturbance on the understory light environment and sapling dynamics of the Fu-shan Experimental Forest, a subtropical rain forest in northeastern Taiwan. Mean understory light levels were approximately 30% of those in the open immediately following the two 1996 typhoons which affected the forest, yet in 1997, following two more typhoons, mean understory light levels were 10%–20% of those in the open. The decline of understory light levels to those present prior to the typhoons was more rapid in 1996 than in 1997, even though the two typhoons in 1996 were more intense than those in 1997. This difference might be the result of the timing of the typhoons. In 1996 the typhoons occurred earlier in the growing season, before August 1 rather than the middle and end of August in 1997. The regular defoliation caused by the frequent typhoons that impact Fu-shan (average of 1.4 per year) and the low stature of the forest (mean canopy height of 10.6m), results in much higher light levels beneath the canopy (9%–30% of levels in the open) than those found in most tropical and temperate forests. As a result, understory light levels are not limiting the distribution of canopy tree saplings within the forest and there is no evidence that canopy gaps play an important role in canopy tree regeneration within the Fu-shan Experiment Forest. This is in contrast with the pattern reported for some tropical forests. With frequent typhoons impacting northeastern Taiwan, the forests of this region are perpetually recovering from wind disturbances.     

Direct measurements of carbon exchange at forest disturbance sites: a review of results with the eddy covariance method

ABSTRACT

Boreal and temperate forests cover a large part of the Earth. Forest ecosystems are a key focus for research because of their role in the carbon (C) balance and cycle. Increasing atmospheric temperatures, different disturbances (fire, storm and insects) and forest management (clear-cutting) will change considerably the C status of forest ecosystems. Using the eddy covariance (EC) method, we can define interactions among environmental factors that influence the C-balance and whether a forest ecosystem is functioning as a C-sink or C-source or possibly is C-neutral. In our review of published studies of different disturbances, we found that most of the post-disturbance studies based on EC method focused on the effects of forest fire and clear-cutting, only a few studies studies focused on the effects of storms and insects. Generally a forest is a C-source until several years after disturbance and then a forest is able to absorb C and become a C-sink. Recovery to C-sink status required up to 20 years in clear-cut areas. Recovery following wildfire disturbance was much longer, possibly more than 50 years. Recovery to C-sink status required approximately 5 years after storm and insect outbreak, however we can not predict overall recovery period because of the missing data.     

不同干扰程度对常绿阔叶林迹地群落结构的影响

对常绿阔叶林迹地，选择了微干扰下形成的常绿阔叶林和持续干扰下形成的杉木林进行了比较研究。结果表明，微干扰下形成的常绿阔叶林在高生长，径级生长以及物种多样性方面均优于持续干扰下形成的杉木林，而且在林木生长方面也优于后者。说明在植被恢复过程中，应立足于生态学的思想，从整体出发观察森林，力求利用森林生态系统所发生的自然过程。把生态与经济最合理的结合起来，实现一种近自然的森林经营模式。     

Carbon fluxes and their response to environmental variables in a Dahurian larch forest ecosystem in northeast China

The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 （simplified expression of g （carbon）.m^-2.month^-1） and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 （simplified expression of g （carbon）.m^-2.a^-1） during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit （VPD） and temperature. Under humid conditions （VPD 〈 1.0 kPa）, the gross ecosystem production （GEP） increased with increasing temperature. But the net ecosystem production （NEP） showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment （VPD 〉 1.0 kPa）, the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions （VPD 〈 1.0 kPa）, both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.     

森林火灾后蒙古栎林碳素分布及储量的分析

以黑龙江塔河林业局施业区内的杜香—蒙古栎林和草类—蒙古栎林为对象,对火灾前后碳素的分布和储量进行了研究。结果表明:森林火灾发生后,蒙古栎林地上、地下部分的碳储量均表现为减少。杜香—蒙古栎林碳储量变化量为-33.812 9 t.hm-2,其中:地上部分为-0.499 4 t.hm-2,地下部分为-33.313 5 t.hm-2,贡献率分别为1.5%和98.5%;杜香—蒙古栎林碳储量变化量为-104.944 6 t.hm-2,其中:地上部分为-76.452 7 t.hm-2,地下部分为-28.491 9 t.hm-2,贡献率分别为72.9%和27.1%。蒙古栎林地上、地下火灾前后碳储量的分布与变化同林分类型密切相关。     

Effect of collar insertion on soil respiration in a larch forest measured with a LI-6400 soil CO2 flux system

Little information is available on the effect of root cutting by the collar pre-insertion technique on soil respiration. In this study, we found that soil respiration rates decreased with increasing depth of collar insertion in both the with live roots intact and with live roots severed treatments, but the rate of decrease was substantially higher in the former. The cutting of roots, especially fine roots, may be responsible for this result.     

Seasonal soil CO2 efflux dynamics after land use change from a natural forest to Moso bamboo plantations in subtropical China

Moso bamboo plantations (Phyllostachys pubescens) are one of the most important forest types in southern China, but there is little information on the effects of their establishment and silvicultural practices on soil CO₂ efflux. The objectives of this study were to evaluate the effect of land use change from a natural broadleaf evergreen forest to Moso bamboo plantations and their management practices on soil CO₂ efflux in a subtropical region of China using static closed chamber method. Regardless of the land uses or management practices, the effluxes over a 12-month period had a seasonal pattern, with the maximum effluxes observed in summer and the minimum in winter. Whereas there was no significant difference in the total annual soil CO₂ efflux between the natural broadleaf evergreen forest (BL) and the conventionally managed bamboo forests (CM), soil CO₂ efflux in the intensively managed bamboo forest (IM) was significantly higher. Soil temperature was the most important environmental factor affecting soil CO₂ efflux rates for all three land uses. Soil moisture also had a significant positive correlation with soil CO₂ efflux rates. Soil temperature and moisture had greater influence on soil CO₂ efflux rate in the IM than the CM and BL forests. Soil dissolved organic C had a positive correlation with soil CO₂ efflux rate in the CM, but had no significant correlation with that in the IM or the BL forests. Our study for the first time demonstrated that conversion of the natural subtropical broadleaf evergreen forest to Moso bamboo does not increase soil CO₂ efflux. However, when bamboo forests are under intensive management with regular tillage, fertiliser application and weeding, significantly more soil CO₂ emission occurs. Therefore, best management practices should be developed to reduce soil CO₂ efflux in Moso bamboo plantations in the subtropical regions of China.     

Carbon density and accumulation in woody species of tropical dry forest in India

We studied the carbon density and accumulation in trees at five sites in a tropical dry forest (TDF) to address the questions: how is the TDF structured in terms of tree and carbon density in different DBH (diameter at breast height) classes? What are the levels of carbon density and accumulation in the woody species of TDF? Is the vegetation carbon density evenly distributed across the forest? Does carbon stored in the soil reflect the pattern of aboveground vegetation carbon density? Which species in the forest have a high potential for carbon accumulation? The WSG among species ranged from 0.39 to 0.78 g cm⁻³. Our study indicated that most of the carbon resides in the old-growth (high DBH) trees; 88-97% carbon occurred in individuals ?19.1 cm DBH, and therefore extra care is required to protect such trees in the dry forest. Acacia catechu, Buchanania lanzan, Hardwickia binata, Shorea robusta and Terminalia tomentosa accounted for more than 10 t ha⁻¹ carbon density, warranting extra efforts for their protection. Species also differed in their capacity to accumulate carbon indicating variable suitability for afforestation. Annually, the forest accumulated 5.3 t-C ha⁻¹ yr⁻¹ on the most productive, wettest Hathinala site to 0.05 t-C ha⁻¹ yr⁻¹ on the least productive, driest Kotwa site. This study indicated a marked patchy distribution of carbon density (151 t-C ha⁻¹ on the Hathinala site to 15.6 t-C ha⁻¹ on the Kotwa site); the maximum value was more than nine times the minimum value. These findings suggest that there is a substantial scope to increase the carbon density and accumulation in this forest through management strategies focused on the protection, from deforestation and fire, of the high carbon density sites and the old-growth trees, and increasing the stocking density of the forest by planting species with high potential for carbon accumulation.     

Timber harvesting as ongoing disturbance in a landscape of diverse ownership

Although the northeastern US includes extensive areas of aggrading forest, uncertainty regarding the intensity and pattern of forest harvesting hampers an understanding of important ecological processes and characteristics such as carbon and nitrogen storage, habitat quality, and forest dynamics, and impedes regional conservation and management planning. Due to the complex ownership pattern dominated by thousands of non-industrial private forest (NIPF) owners and the difficulty of detecting selective logging using remote sensing, details of the harvesting regime remain largely unknown to the scientific and policy communities. To examine the value of statewide regulatory data for Massachusetts as a unique source of this critical information, we analyzed 17 years of timber harvest data gathered for regulatory purposes for a 168,000 ha forested landscape in Massachusetts that is the focus of concerted conservation planning and intensive study of landscape and ecosystem pattern and process. The North Quabbin Region is heavily wooded with a complicated ownership pattern dominated by over 2500 NIPF owners, three state agencies, and diverse conservation and municipal holdings.

The extent and intensity of harvesting were surprising, with an annual disturbance rate of 1.5% and a mean intensity of 44.7 m³ ha⁻¹ (approximately one-fourth of average stand volume). The predominant form of harvesting was selective removal of commercially valuable tree sizes, grades and species (e.g., Quercus rubra and Pinus strobus). The spatial pattern of logging was random with regards to major physical, biological, or cultural factors. However, logging was strongly related to landowner class. NIPF owners control 60% of the forest area and were responsible for 64.1% of harvest area, but the highest logging intensity (volume per area harvested; 69.3 m³ ha⁻¹) among major landowners was conducted by the state agency responsible for managing southern New England’s largest conservation property, the watershed of Boston’s drinking reservoir.

This regime of chronic disturbance is occurring over the entire landscape and exerting a major influence on forest composition, dynamics, and habitat quality. However, dispersed selective harvesting is largely unnoticed by residents, is routinely overlooked by ecologists and conservationists, and would remain unrecognized in the absence of this previously unused regulatory data. These results identify the value of regional regulatory spatial information to estimate ecological trends and to assist in conservation planning. Given similarities among ownership and forest patterns for much of the northeastern US, we expect that the broad findings of this study to have regional application.     

Effects of a severe typhoon on forest dynamics in a warm-temperate evergreen broad-leaved forest in southwestern Japan

The effects of a typhoon on forest dynamics and the response of major tree species were studied in a warm-temperate evergreen broad-leaved forest in southwestern Japan. The strongest typhoon on record (T9313) passed through this region in 1993. Return periods of typhoons over 30 ms⁻¹ in instantaneous wind velocity and T9313 were estimated to be 2.2 and 104.5 years, respectively. Approximately 10% of all stems suffered some damage from T9313 and annual stem mortality rose from 1.3 to 2.7%. The estimated period that the number of stems would fall below 10% of the initial was four years shorter with T9313-class typhoons than without them. Thus, the disturbance by T9313 was not catastrophic at the site although T9313 was an episodic typhoon. The short-term responses of major tree species to T9313 were classified into four types: 1) blunt-response type with little decrease and recruitment of stems in the DBH ≥ 5 cm class (Distylium racemosum), 2) retreat type with larger decrease than recruitment (e.g. Quercus acuta), 3) sharp-response type with a large decrease and much recruitment (e.g. Cinnamomum japonicum), and 4) advance type with less decrease than recruitment (Eurya japonica). Among the four regeneration types classified by previous studies (climax, light-demanding, subcanopy, and few-sapling), the climax and few-sapling types each showed a specific short-term response, the blunt-response and retreat types, respectively, that explains one aspect of the regeneration strategies of each type. On the other hand, the light-demanding or sub-canopy type showed multiple short-term responses, indicating that each regeneration type contains species with various regeneration strategies. In this paper, I analyzed data from the database that was compiled by the Aya Research Team.     

Recovery of species diversity after disturbance of broad-leaved Korean pine mixed forest in Changbai Mountain

IntroductionMorerecently,Thehumanl1asshowedagreatinterestli1studiesonpatternsofchangesinspeciesdiversityduriI1gprocessofsuccession,ThedistuIbal1ceofI1umanactivitiesornaturedisastershasagreatbopactonspeciesdiversity.PlantsPeciescomprisingapost-disturbancecommunityderhefromavarietyofsources-winddispersedseed,buriedpropagulesandresproutingsurvivorsl1'l.TheirulthatecontributiontotheserialflorarenectSacomplexinteractionofinitialabundance,includingdistuthanceintCnsity,proPagatCavailability,andc…     

Potential impacts of a climate change on forest ecosystems

Review of literature indicates that many uncertainties and assumptions exist in predicting the impacts of a climate change on forest ecosystems. However, current knowledge is sufficient to encourage any measures that are combating climate change, that is to reduce first and foremost the release of harmful substances to the atmosphere, lithosphere and biosphere.     

Monitoring forest dynamics using satellite imagery—a case study in the natural reserve of Changbai Mountain in China

This study intended (1) to develop a quantitative method to describe vegetation succession or change by remote sensing approach, and (2) to test the capability in clarifying the stability or instability of natural forests in landscape scales. With special attention on the coniferous forest, the attempt was conducted on the natural reserve of Changbai mountain in northeast China by using multi-temporal TM images. Two simple parameters were derived to represent succession rate or change extent. One was the mean change of radiance, and another was the number of pixels with changed reflection property. As conclusion, TM imagery is effective for detecting vegetation changes. The results also demonstrated that the so called climax is not a pure stand, which is generally assumed to be exclusively dominated by climax species, but rather a complex of shifting mosaic. The pioneer patches are permanent units in the forest community. This method is considered applicable for assessing the developing status or behavior of plant communities in large scales, like a life zone, under disturbance of global warming, especially for long-time span.     

Effects of disturbance history and environmental factors on the diversity and productivity of understory vegetation in a cool-temperate forest in Japan

We assessed the species richness and aboveground productivity of understory plants in nine types of forest stand (116 plots in total) that had different disturbance histories that were combinations of the frequency of plantation (clear-cutting, site preparation, planting), typhoon damage, and selective cutting. We established two 1 m × 1 m quadrats to measure species richness and productivity and one 1 m × 30 m belt to measure species richness in each plot. Canopy leaf area index (LAI), soil NH₄⁺, soil C/N ratio, slope angle, and slope aspect were measured as current environmental factors affecting each plot. The variance in species richness was better explained by disturbance history (69% in quadrats; 86% in the belt) than by current environmental factors. Species richness and the Simpson index decreased as the frequency of plantation increased. In contrast, the variance in productivity was better explained by current environmental factors (82%), especially canopy LAI (45%), than by disturbance history. The relations of species presence and productivity to the explanatory variables differed among species, although there were some common responses within life forms. The effects of disturbance on species diversity remained for 20–80 years. Forest management should therefore take into account the long-term effects of disturbance history to maintain understory plant diversity.     

Carbon balance of a forest ecosystem after stump harvest

Abstract

Stump harvest in forests can cause both reductions of CO₂ emissions through a decrease of decomposable substrate (direct effect) and emission increases as a consequence of deep and extensive soil disturbance (indirect effect). Here, the effects of stump harvest on net ecosystem CO₂ exchange (NEE) in a former Norway spruce stand in mid Sweden are presented. CO₂ exchange was continuously followed by eddy-covariance measurements during the first years after harvest. Differences in NEE from stump harvested and mounded (reference) plots were determined by soil-surface respiration measurements. Respiration from decaying stumps was estimated by a decomposition model. Fluxes indicated a direct effect (decreased efflux) during the first year after harvest that corresponded to the absence of decomposing stumps. During the following years, this emission reduction was increasingly counteracted by an indirect effect (increased efflux) of similar magnitude. This means that the expected emissions caused by extra soil disturbance occur with a certain delay and seem to increase with time. By these emissions, the substitution efficiency of stumps as bioenergy resource is reduced. Furthermore, at a time scale of centuries, instant combustion of stumps leads to a larger contribution to global warming than slow decomposition, because the stump carbon is available earlier in form of greenhouse gas. This is estimated by the time integral of emissions. Thus, despite the surprisingly low initial emissions, the overall substitution efficiency and climate benefits of stump harvest are likely to be small. The long-term consequences of stump harvest for the carbon budget are, however, still uncertain.     

鸡公山自然保护区森林植被生物量及活碳蓄积量研究

运用鸡公山科学考察资料及1999年森林资源清查资料,采用森林材积源生物量推算方法研究了鸡公山森林植被生物量及其活碳蓄积量。结果表明:鸡公山森林植被生物量总值为309 202t,平均森林植被生物量为111.7t／hm2,高于全国平均水平(77.4t／hm2);鸡公山森林植被的总活碳蓄积量为154 601t,平均活碳密度为56MgC／hm2,高于中国森林植被活碳密度的平均水平(38.7 MgC／hm2),但低于全球平均碳密度(86MgC／hm2)。不同林型活碳蓄积密度分析结果表明,马尾松、杉木和栎类林木的活碳蓄积密度分别为30MgC／hm2,39 MgC／hm2和70MgC／hm2,均高于全国同类型森林植物的活碳蓄积密度的平均值,而次生阔叶混交林的碳蓄积密度略低于全国平均水平。鸡公山自然保护区67％的森林为中龄林,27％的森林为幼龄林,在增加碳蓄积方面还有巨大的潜力。