Soil carbon dioxide fluxes of a typical broad-leaved/Korean pine mixed forest in Changbai Mountain, China

The forest ecosystem plays an important role in the global carbon cycling. A study was conducted to evaluate soil CO2 flux and its seasonal and diurnal variation with the air and soil temperatures by using static closed chamber technique in a typical broad-leaved/Korean pine mixed forest area on the northern slope of Changbai Mountain, Jilin Province, China. The experiment was carried out through the day and night in the growing season (from June to September) in situ and sample gas was analyzed by a gas chromatograph. Results showed that the forest floor was a large net source of carbon, and soil CO2 fluxes had an obvi-ous law of seasonal and diel variation. The soil CO2 flux of broad-leaved/Korean pine mixed forest was in the range of 0.302.42 mmol穖-2穝-1 with the mean value of 0.98 mmol穖-2穝-1. An examination on the seasonal pattern of soil CO2 emission suggested that the variability in soil CO2 flux could be correlated with variations in soil temperature, and the maximum of mean CO2 flux occurred in July ((1.27±23%) mmol穖-2穝-1) and the minimum was in September ((0.50±28%) mmol穖-2穝-1). The fluctuations in diel soil CO2 flux were also correlated with changes in soil temperature; however, there existed a factor for a time lag. Soil CO2 flux from the forest floor was strongly related to soil temperature and had the highest correlation with temperature at 6-cm depth of soil. Q10 values based on air temperature and soil temperature of different soil depths were at the ranges of 2.09–3.40.

Effect of thinning intensity on understory herbaceous diversity and biomass in mixed coniferous and broad-leaved forests of Changbai Mountain

Background:Herbs are an important part of the forest ecosystem,and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances.Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone,this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning.Results:The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity,they were mainly determined by seasonal changes.Across the entire growing season,the species with the highest importance values in thinning treatments included Carex pilosa,Aegopodium alpestre,Meehania urticifolia,and Filipendula palmata,which dominated the herb layer of the coniferous and broad-leaved mixed forest.The number of species,Margalef index,Shannon-Wiener index and Simpson index all had their highest values in May,and gradually decreased with months.Pielou index was roughly inverted“N”throughout the growing season.Thinning did not increase the species diversity.Thinning can promote the total biomass,above-and below-ground biomass.The number of plants per unit area and coverage were related to the total biomass,above-and below-ground biomass.The average height had a significantly positive correlation with herb biomass in May but not in July.However,it exerted a significantly negative correlation with herb biomass in September.The biomass in the same month increased with increasing thinning intensity.Total herb biomass,above-and below-ground biomass showed positive correlations with Shannon-Winner index,Simpson index and Pielou evenness index in May.Conclusions:Thinning mainly changed the light environment in the forest,which would improve the plant diversity and biomass of herb layer in a short time.And different thinning intensity had different effects on the diversity of understory herb layer.The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.

Dynamics of nitrogen nutrition of coexisting dominant trees in mixed broad-leaved/Korean pine forest

Chemical analysis of ammonium, nitrate and total nitrogen in tree leaves and roots and anin-vivo bioassay for nitrate reductase activity (NRA) were used to monitor the seasonal variations in nitrogen assimilation among four coexisting dominant tree species, includingPinus koraiensis, Tilia amurensis, Fraxinus mandshurica andAcer mono, in a virgin mixed broad-leaved/Korean pine (Pinus koraiensis) forest. The soil study included individual horizons of L+F (0–5 cm), Ah (5–11 cm) and Aw (11–25 cm). All four species had nitrate and ammonium in their roots and leaves, and also NRA in leaves. This indicated that these coexisting species were adapted to ammonium + nitrate nutrition. A negative correlation existed between nitrate use and ammonium use. Ammonium concentration was higher than that of nitrate in tree leaves and roots, and also in soils, which indicated climax woody species had a relative preference for ammonium nutrition. There was a positive relationship between tree nitrogen nutrition use and soil nitrogen nutrient supply. Utilization of ammonium and nitrate as well as the seasonal patterns differed significantly between the species. Peaks of ammonium, nitrate, NRA and total nitrogen in one species were therefore not necessarily synchronous with peaks in other species, and which indicated a species-specific seasonal use of nitrogen. The species-specific temporal differentiation in nitrogen use might reduce the competition between co-existing species and may be an important mechanism promoting stability of virgin mixed broad-leaved//Korean pine forest.

Responses of soil Collembolans to vegetation restoration in temperate coniferous and broad-leaved mixed forests

A total of 900 soil samples were collected from five habitats,including primary coniferous broad-leaved mixed forests,secondary coniferous broad-leaved mixed forests,secondary broad-leaved forests,secondary shrub forests,and cutover lands in spring,summer,and autumn to quantify responses of soil Collembolans(springtails)to the restoration of vegetation of temperate coniferous and broad-leaved mixed forests.The results reveal that the taxonomic composition of Collembolans varied in the different stages of vegetation restoration.Seasonal variations were in regard to their abundance and richness.High similarities existed in Collembola communities at different stages of vegetation restoration,and distribution patterns of Collembola taxa displayed an evenness throughout all habitats.Soil Collembolans tended to gather on litter layers and soil surface;the highest abundance was found in the upper 5 cm soil layer during the initial stages of vegetation recovery.Tomocerus,Proisotoma,and Folsomia genera responded positively to the restoration of vegetation.However,responses of Ceratophysella and Parisotoma genera were negative.In addition,the Onychiuridae family did not respond to the vegetation restoration process.It was concluded that restoration of vegetative cover can increase the abundance of soil Collembolans,but different genera respond differently.

NITROGEN NUTRIENT MECHANISM IN SECONDARY SUCCESSION PROCESS OF THE MIXED BROAD-LEAVED/ KOREAN PINE (PINUS KORAIENSIS) FOREST

Chemical and biochemical analysis methods were used to monitor the vedations of nitrogen nutrient among the dominance trees species in secondary succession process of the mixed broad - leaved/Korean pine forest on Changbai Mountains, Northeast China. Amounts of total nitrogen, anunonium and NRA in soils of virgin broad-leaved/Korean pine forest which is in climax were higher than those of secondary birch forests those are in succession Stage. The amount of nitrate was in the other hand. In climax, dominance trees species are tolerant mesophytic trees such as Pinus Koraiensis, Tilia amurensis, Acer mono and also Fraxinus mandshurica, they are all ammonium + nitrate adapted species, but they show a preference for the anunonium rather than those of the pioneer trees species in secondary birch forest, such as Populus davidiava and Betula platyphylla. Because they have more ammonium in their leaves and roots, especially Pinus koraiensis. Populus davidvana and Betula plaaphlla are intolerant trees, amounts of nitrate and total nitrogen is higher in their leaves and roots and also NRA in their leaves, so they preference for the nitrate rather than the others.In secondary birch forest, the regeneration trees species adapt their nitroggn nutrient to the variation of nitrogen nutrient situation in soil, finally they could survival well and the secondary birch forest would succession to climax. In climax, dominance trees species adapt their Nitrogen nutrient to the situation in soil and there are not strong competition in nitrogen nutrient among them, so they can coexist well and keep the climax as stable vegetation.

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

Recovery of species diversity after catastrophic disturbance was influenced by a few factors, such as intensity of disturbance, availability of propagules, and the environmental conditions, In this paper, we examined pattems of species development after nearly 60a succession in bumed broad-leaved Korean pine mixed forest on northem slope of ChangbaiMountain. We aasessed the recovery of plant species diversity in 3 types of forests under the contition with gradient of soil moisture. Results revealed that recovery of plant species (liversity varied greatly under different environmental conditions.Species richness of secondary forests greatly related to the site condition. Secondary birch forest on mesic site had the greatest number of plant species and the following was poplar-birch forest and larch-birch forest.Most of characteristic taxa couldbe found in birch forest after 60a succession. For larch-birch forest on hydra site, most of climax species were still not able to invade, so it had the lowest species diversity.

Meteorological control on CO_2 flux above broad-leaved Korean pine mixed forest in Changbai Mountains

The impacts of temperature, photosynthetic active radiation (PAR) and vapor pressure deficit (VPD) on CO2 flux above broad-leaved Korean pine mixed forest in the Changbai Mountains were studied based on eddy covariance and meteorological factors measurements.The results showed that, daytime CO2 flux was mainly controlled by PAR and they fit Michaelis-Menten equation. Meanwhile VPD also had an influence on the daytime flux. Drier air reduced the CO2 assimilation of the ecosystem, the drier the air, the more the reduction of the assimilation. And the forest was more sensitive to VPD in June than that in July and August. The respiration of the ecosystem was mainly controlled by soil temperature and they fit exponential equation. It was found that this relationship was also correlated with seasons; respiration from April to July was higher than that from August to November under the same temperature. Daily net carbon exchange of the ecosystem and the daily mean air temperature fit exponential equation. It was also found that seasonal trend of net carbon exchange was the result of comprehensive impacts of temperature and PAR and so on. These resulted in the biggest CO2 uptake in June and those in July and August were next. Annual carbon uptake of the forest ecosystem in 2003 was -184 gC. m-2.

CO_2 flux evaluation over the evergreen coniferous and broad-leaved mixed forest in Dinghushan, China

The Dinghushan flux observation site, as one of the four forest sites of ChinaFLUX, aims to acquire long-term measurements of CO2 flux over a typical southern subtropical evergreen coniferous and broad-leaved mixed forest ecosystem using the open path eddy covariance method. Based on two years of data from 2003 to 2004, the characteristics of temporal variation in CO2 flux and its response to environmental factors in the forest ecosystem are analyzed. Provided two-dimensional coordinate rotation, WPL correction and quality control, poor energy-balance and underestimation of ecosystem respiration during nighttime implied that there could be a CO2 leak during the nighttime at the site. Using daytime (PAR > 1.0μmol-1·m-2·s-1) flux data during windy conditions (u* > 0.2 m·s-1), monthly ecosystem respiration (Reco) was derived through the Michaelis-Menten equation modeling the relationship between net ecosystem CO2 exchange (NEE) and photosynthetically active radiation (PAR). Exponential function was employed to describe the relationship between Reco and soil temperature at 5 cm depth (Ts05), then Reco of both daytime and nighttime was calculated respectively by the function. The major results are: (i) Derived from the Michaelis-Menten equation, the apparent quantum yield (α) was 0.0027±0.0011 mgCO2·μmol-1 photons, and the maximum photosynthetic assimilation rate (Amax) was 1.102±0.288 mgCO2·m-2·s-1. Indistinctive seasonal variation of o or Amax was consistent with weak seasonal dynamics of leaf area index (LAI) in such a lower subtropical evergreen mixed forest. (ii) Monthly accumulated Reco was estimated as 95.3±21.1 gC·m-2 mon-1, accounting for about 68% of the gross primary product (GPP). Monthly accumulated NEE was estimated as -43.2±29.6 gC·m-2·mon-1. The forest ecosystem acted as carbon sink all year round without any seasonal carbon efflux period. Annual NEE of 2003 and 2004 was estimated as -563.0 and -441.2 gC·m-2·a-1 respectively, accounting for about 32% of GPP.

Community Dynamics of Seed Rain in Mixed Evergreen Broad-leaved and Deciduous Forests in a Subtropical Mountain of Central China

Seed dispersal is a key process within community dynamics. The spatial and temporal variations of seed dispersal and the interspecific differences are crucial for understanding species coexistence and community dynamics. This might also hold for the mixed evergreen broadleaved and deciduous forests in the mountains of subtropical China, but until now little existing knowledge is available for this question. In 2001, we chose to monitor the seed rain process of our mixed evergreen broad-leaved and deciduous forest communities in Mount Dalaoling National Forest Park, Yichang, Hubei Province, China. The preliminary analyses show obvious variations in seed rain density, species compositions and timing of seed rain among four communities. The average seed rain densities of the four communities are 2.43 ± 5.15, 54.13 ±182.75, 10.05 ±19.30 and 24.91 ± 58.86 inds/m^2, respectively; about one tenth the values in other studies in subtropical forests of China. in each community, the seed production is dominated by a limited number of species, and the contributions from the others are generally minor. Fecundity of evergreen broadleaved tree species is weaker than deciduous species. The seed rain of four communities begins earlier than September, and stops before December, peaking from early September to late October. The beginning date, ending date and peak times of seed rain are extensively varied among the species, indicating different types of dispersal strategies. According to the existing data, the timing of seed rain is not determined by the climate conditions in the same period, while the density of seed rain may be affected by the disturbances of weather variations at a finer temporal resolution.

毛竹林与珍贵楠木混交造林试验研究

研究通过毛竹林与浙江楠、刨花楠混交造林试验,提出毛竹与楠木混交造林的营建方法和途径。结果表明:珍贵楠木在竹林中套种,刨花楠的成活率在93.3%以上,浙江楠的成活率在86.7%以上,说明毛竹林地进行楠木混交造林具有可行性,能够改善林分结构。做到以短养长,以林养林,增加收入。

Changes in Soil Carbon Pools Induced by Substitution of Plantation for Native Forest

Changes in soil carbon pools under Chinese fir (Cunninghamia lanceolata) andbamboo (Phyllostachys pubescens) plantations substituted for a native forest (Quercus acutissima,Cyclobalanopsis glauca, Cas-tanopsis sclerophylla, Platycarya strobilacea, Lithocarpus glaber) werestudied on the hills with acid parent rock and soils classified as red soils (Ferrisols) in Huzhou,Zhejiang Province of east China. It was found that total soil organic carbon (TSOC), easilyoxidisable carbon (EOC) and water-soluble organic carbon (WSOC) under bamboo plantation wereincreased, but microbial biomass carbon (MBC) was decreased. On the contrary, Chinese fir induceddeclines of all fractions of C including TSOC, EOC, WSOC and MBC. The percentages of the activefractions of soil C (EOC and WSOC) were increased in the plantations as compared to the nativebroad-leaved forest, but proportions of soil organic C as MBC were decreased. It could be concludedthat bamboo plantation had a great ability of not only fixing C but also accelerating soil C poolcycle, improving nutrient and microorganism activity; therefore, it is a good ecosystem and could berecommended for wide development. Chinese fir would shrink the soil C pool and deteriorate soilbiological fertility, so it did not benefit CO2 fixing and land sustainable utilization.

竹茶混交模式对表层土壤有机碳储量及组分的影响

为探究毛竹林下种植茶树对土壤有机碳储量与碳组分的影响,该研究以毛竹纯林、竹茶混交林和常绿阔叶林为研究对象,采集这3种林分类型的表层(0~10 cm)土壤,测定土壤有机碳(SOC)、碳组分、生物与非生物因素指标。结果表明:(1)竹茶混交林林下植物多样性相较于毛竹纯林显著降低,但其土壤有机碳密度(22.54±2.09) t·hm^(-2)、碳组分与毛竹纯林无显著差异(P>0.05)。竹茶混交林的矿物结合态有机碳(MOC)为(20.13±1.83) g·kg^(-1),占总有机碳的92.66%。常绿阔叶林土壤有机碳密度比竹茶混交林和毛竹纯林高土壤有机碳密度分别高41.15%和41.00%(P<0.05)。(2)3种林分类型土壤微生物量碳(MBC)含量范围为0.58~3.08 g·kg^(-1),土壤16S rRNA丰度范围为2.18×10^(10 )~5.65×10^(10)copies·g^(-1),固碳基因cbbL丰度范围为0.37×10~8~1.10×10~8 copies·g^(-1),土壤微生物碳利用效率范围为0.03~0.28;3种林分类型之间微生物相关指标不存在显著差异(P>0.05)。(3)3种林分类型SOC与土壤pH、砂粒含量和地上凋落物生物量呈显著负相关,与土壤黏粒含量、粉粒含量、总氮、C∶N、总磷和铵态氮含量呈显著正相关(P<0.05)。(4)就不同碳组分而言,颗粒有机碳(POC)和MOC均与土壤pH、砂粒含量和根系生物量呈显著负相关,与土壤含水量、黏粒含量、粉粒含量、总氮、C∶N、总磷和铵态氮含量呈显著正相关(P<0.05)。综上表明,竹茶混交改造会造成原生毛竹纯林林下植被多样性下降,但并未造成土壤碳储量下降;而相较于常绿阔叶林,毛竹经营措施需要改进,以提升其碳汇效益。

竹木混生林中观光木的空间结构及竞争力比较

于2020年3—5月,在福建省明溪县夏阳乡的竹木混生林中,采用3种择伐方式(HW、HE、JW处理),以不间伐的林分作为对照(CK),选择观光木为对象木,与观光木相邻的4株林木作为竞争木,测定混交度(M_(i))、角尺度(W_(i))、密集度(C_(i))等主要空间结构指标,并采用Hegyi竞争模型计算观光木竞争指数,对其空间结构及竞争力进行综合评价。结果表明,对照(保留竹木混生林原有状态)中,观光木的M_(i)、W_(i)、C_(i)分别为1.0、0.6667、0.7083,属极重度混交,呈团状、密集分布;同一高度级林木竞争指数基本上高于择伐处理,由于空间结构不合理,观光木受到以毛竹为主的竞争木上层遮盖和侧方挤压程度大,竞争力较低。择伐处理中,以HE处理(以对象木为中心,砍伐半径2 m范围内所有竞争木)效果最好,观光木的M_(i)、W_(i)、C_(i)分别为1.0、0.3125、0.2500,混交度仍属极重度混交,但分布格局呈均匀、开阔分布,同一高度级竞争指数较大幅度降低,观光木竞争力增强;不同高度级观光木的平均竞争指数存在差异,小于10~12 m高度级观光木的平均竞争指数基本大于0.5;大于10~12 m高度级的观光木竞争指数在0.1280~0.4870之间,竞争指数较大幅度降低,趋于平稳,观光木竞争力增强。在观光木树高达到10 m之前,采取人工干预是必要且关键的技术措施。

竹阔混交林混交类型的综合评价

根据生态系统工程的理论和方法 ,应用系统最优综合评价模型 ,对竹阔混交林 5种类型 2 2个指标进行综合评价。阔叶树的比例为 2 5 %～ 35 %的竹阔混交林综合效益最高 。

竹阔混交林的水文效应

对竹阔混交林不同类型的地上部分截留降水能力和土壤贮水性能等水文效应进行了研究。结果表明 ,在各混交类型中 ,随着阔叶树比例的增加 ,上述指标基本上呈增强的趋势。混交比例为 2 5%～ 3 5%类型的各项指标值均较高 ,其土壤贮水能力最强 ,林分的总涵水量最高 。

大岗山四种林型夏秋季土壤呼吸研究

森林类型的转换必然会影响到森林碳循环模式,通过比较亚热带地区4种常见林型即常绿阔叶林、针阔混交林、杉木林、毛竹林在生长季土壤呼吸的差异,揭示林型改变对土壤碳库碳输出过程的影响。研究结果显示,在生长季常绿阔叶林、针阔混交林、杉木林、毛竹林平均土壤呼吸值(CO2)差异显著,分别为4.28,3.51,2.28,5.37μmol/(m2.s)。4种林型土壤呼吸变化动态规律类似,从6月份开始升高,在7月或者8月达到峰值,然后开始下降,10月份土壤温度大幅下降,土壤呼吸也达到一个低谷。4种林型的土壤呼吸日变化均不明显。4种林型的土壤呼吸速率均与土壤温度呈显著相关关系,除杉木林外,另3种林型的土壤呼吸与土壤湿度相关关系不显著。

檫树毛竹混交林中毛竹鞭根的研究

采用固定标准地定位观测法,对新造竹林中栽植檫树后形成的檫树(14～15年)毛竹混交林竹鞭根结构和鞭体养分进行了调查和测定.结果表明,檫树在一定的密度范围内,混交竹林有利于毛竹鞭根结构的优化和鞭体养分的提高.与毛竹纯林相比,檫树密度为420～615株*h m-2的混交竹林,其鞭长、鞭径及其整齐度、新鞭年生长量、壮幼鞭比例、健壮芽数量、鞭根体积等,均在不同程度上高于毛竹纯林中的对应部分.当檫树密度超过735株*hm -2时,混交竹林中的上述指标则低于毛竹纯林中的对应部分,但单位鞭长的分岔次数明显加大.回归分析表明,鞭总长、鞭节长、新鞭生长量、鞭径、鞭径整齐度及单位鞭长分岔次数与檫树密度之间的关系密切(r=0.92956～0.99530).混交竹林中鞭体的N、P、K、Ca、M g养分含量高于纯林中的对应值,其中鞭体中N含量较纯林平均高出7.6%～11.6%.

6种不同沿海防护混交林凋落叶持水性能比较

[目的]了解并比较沿海地区6片木麻黄与竹子防护混交林凋落叶持水性能状况,为沿海防护林树种选择提供理论依据。[方法]通过设置标准地,样方搜集和室内浸水试验,测量凋落叶自然含水率、持水率、吸水速率、失水率和失水速率,比较分析混交林凋落叶持水性能。[结果]木麻黄与花吊丝竹混交林凋落叶的最大持水率较高,其次为吊丝单竹＋木麻黄、勃氏甜龙竹＋木麻黄、绿竹＋木麻黄、麻竹＋木麻黄和大头典竹＋木麻黄;而自然含水率从高到低依次为勃氏甜龙竹＋木麻黄〉花吊丝竹＋木麻黄〉绿竹＋木麻黄〉大头典竹＋木麻黄〉吊丝单竹＋木麻黄〉麻竹＋木麻黄;从凋落叶的吸水和自然风干过程来看,6种混交凋落叶的持水率、吸水速率、失水率和失水速率在浸泡或自然风干的0～2h有一个迅速变化的趋势,2h后凋落叶持水率和吸水速率逐步变缓,16h后逐渐趋于平稳。[结论]回归分析结果表明,持水率和浸泡时间及失水率和风干时间之间的关系均为对数函数关系,而吸水速率与浸泡时间及失水速率与风干时间的关系均为幂函数关系。

毛竹林物种多样性的初步分析

本文调查了福建顺昌的毛竹经营林分和天然竹阔混交林，分析结果表明：经营林分乔木和灌木物种多样性显著低于天然竹阔混交林，草本物种多样性高于天然竹阔混交林；毛竹的生态对策在ｒ－ｋ对策连续统上，经营林分具ｒ－对策倾向，天然竹阔混交林具ｋ－对策倾向．

竹子混交林对林木生长及林分土壤的影响研究

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