林下植被多样性、生物量及养分作用研究进展

林下植被是森林生态系统的重要组成部分,对森林生态系统的稳定性、生产力及养分循环具有重要影响,因此研究林下植被具有重要意义。但是以往由于研究方法、研究时限以及研究尺度等方面存在许多缺陷,对林下植被的认识还不统一,研究结论不够深刻。如何正确测定林下植被多样性及其生物量,合理评价林下植被对森林生态系统的作用,科学制定林下植被的管理措施,这些问题都值得进一步深入研究。文中对林下植被多样性、生物量及其养分作用3个方面的研究进行了分析总结,以期为今后林下植被研究、林下植被管理和森林可持续经营提供参考。     

我国的森林生物量研究

论述了我国森林生物量的研究内容及方法,对乔木层、林下植被、凋落物、粗木质残体、根系以及区域尺度的生物量研究进行了总结,概述了直接收获法、回归模型、平均换算因子法等常见的森林生物量估测方法.最后提出当前我国在研究重点分布、基础数据采集以及空间尺度转换等方面存在的一些问题,指出森林生物量研究在遥感监测等方面的发展趋势.     

杉木林林下植被及其生物量的研究

近年来的一些研究表明,杉木人工林地力衰退日趋严重,维护和提高杉木林地地力已成为杉木人工林发展的重要课题。林下植被是人工林生态系统的一个重要组成部分,在促进人工林养分循环和维护林地地力中起不可忽视的作用。研究林下植被生物量的积累与分配规律及与立地、林分的关系,是研究并利用林下植被的重要前提。有关林下植被生物量的研究,始见于20世纪中叶,但鲜见有关林下植被生物量的专题研究报道,杉木林下植被生物量的测定也只局限于杉木人工林养分循环的系列研究。本文对杉木人工林林下植被生物量的系统研究丰富了上述系列研究的内容,同时也为利用林下植被来维护和提高林地地力提供科学的依据。     

杉木林下植被生物量与盖度的关系

测定林下植被生物量是研究林下植被功能的重要前提,然而林下植被生物量的测定是一项十分繁重的劳动。根据聚类分析结果,将江西省分宜县大岗山实验局山下林场杉木林下植被大致分为5种植被类型,分别不同类型研究林下植被生物量与盖度的关系,可以找到一条测定林下植被生物量的简易途径。     

火力楠人工林森林生物量和林分碳储量研究

火力楠是原生于我国南部、生长迅速、用途广泛的优良乔木树种。试验以生长10年的火力楠人工林为材料采集乔木各器官及乔灌草凋各层样本,采用相对生长法以胸径为变量与树木各器官结合,建立标准木主干、枝条、叶和根四种器官生物量的异速生长模型,通过换算干重比的方法估算生物量并加以比较;乘以对应的含碳系数换算成碳储量,再加和估算林分总碳储量。火力楠人工林乔木层生物量为21.60 t·hm^-2;总森林生物量为25.96t·hm^-2;林分总碳储量为12.60 t·hm^-2。试验地火力楠人工林的郁闭度较大,林下植被较少,乔木层碳储量占比很高,反映出火力楠是较好的碳汇树种。     

马尾松水保林的最适经营密度

本文通过研究长江中上游马尾松水保林的枝叶生物量、林下植被生物量及枯落物重量与林分密度的相关关系，提出了马尾松水保林的最适经营密度，编制了马尾松水保林的最适经营密度表。     

不同措施对川西亚高山桦木天然次生林群落演替进程的影响及综合效益评价

本研究以不同强度疏伐、不同密度补植云杉的桦木天然次生林为研究对象,通过典型抽样法、收获法和模型模拟法等方法获取和分析了不同处理措施下补植苗木成活情况,桦木林林分的生物量,灌、草生物多样性和林地水源涵养能力等指标,研究不同处理措施对川西亚高山桦木天然次生林正向演替进程的影响,并利用隶属函数的方法开展评价。结果表明,与对照措施相比,疏伐和云杉补植措施均在不同程度上改善了林下更新和灌草的生物多样性,也对以乔木为主的林分生物量产生了促进作用,但对林地水源涵养功能的改变不显著。而从1年的短期效应看,S2+B3措施,即按照蓄积量伐除林分20%桦木,且在林下按照2 000株·hm~(-2)的密度进行云杉苗木补植的处理措施对桦木次生林群落的演替进程促进效果最佳。     

赤水河流域毛竹林下植被生物量变化及乌骨鸡养殖技术研究

采用野外样地调查和企业(专业合作社)调研相结合的方法,研究了赤水河流域毛竹林下植被生物量变化及竹乡乌骨鸡养殖技术。结果表明:1)毛竹母竹林、丰产林、低产林和社区林的林下植被生物量分别为68.35 t/hm~2、67.90 t/hm~2、20.81 t/hm~2和56.18 t/hm~2,分别是地上植被生物量的45.39%、37.26%、10.84%和36.03%,其中灌木、草本及枯物层植物生物量所占比重分别为57.21%~74.68%、4.28%~10.24%和19.83%~32.54%;不同类型毛竹林林下植被生物量组成指标、林分结构和植物多样性指标差异显著。2)林下植被生物量受毛竹林植被一土壤系统的综合影响,与部分表层土壤理化指标、林分结构及植物多样性指标呈显著相关,林下植被生物量增加有利于毛竹林地土壤综合肥力提高,林下养殖竹乡乌骨鸡除减少林下植被生物量外,还可能增加表层土壤扰动、减少生物多样性和导致地力衰退。3)毛竹林下养殖竹乡乌骨鸡成倍增加林地产值,适宜750~1500只/hm~2、每年1~2轮的养殖模式。     

经营模式对马尾松天然次生林林下植被生物量及其分布格局的影响

以不同森林经营模式下马尾松天然次生林为研究对象,对经营1年后其林下植被生物量的分布特征进行研究。结果表明:不同经营模式下,马尾松天然次生林下活地被生物量均以灌木层生物量为主,枯落物层生物量对林下植被总生物量的贡献亦大。经营模式为保留密度900株/hm2的马尾松林下植被总生物量最高,而保留密度为2 100株/hm2的马尾松林下植被总生物量最低。保留密度过大或过小林下植被生物量都不高,说明适宜的保留密度才有利于提高马尾松天然次生林下植被的生物量。     

多伦县退耕还林地林下植被地上生物量年变化及影响因子研究

根据内蒙古多伦县2005-2010年6年退耕还林地林下植被地上生物量与气候观测资料,对不同年际林下植被地上生物量变化以及与植被盖度、密度、高度、全年降水量等因子相关分析,建立了影响因子对林下植被地上生物量回归模型并进行预测分析.结果表明:不同年际退耕还林地林下植被地上生物量差异显著,生物量的变化随着退耕还林工程期的延长...     

闽南福建柏人工林生物量结构的研究

在福建柏人工林生物量中 ,乔木层占主要部分 (90 %以上 ) ,其次是枯枝落叶层 ,下木活地被物层最小 ;林分总生物量、乔木层、凋落物层生物量随年龄的增大而增大 ,下木活地被物层随郁闭度的增加而减少。不同龄级的福建柏林分生产力差异明显 ,以Ⅵ龄级的林分生产力最大 ,生产力的总趋势随龄级的增加而增大 ,至Ⅵ龄级后又减少。福建柏人工林胸径与枝叶重、干重、枝重、叶重呈极显著相关 ,结合树高因子 ,可建立相关方程W =aDbHc。     

Understorey fuel load estimation along two post-fire chronosequences of Pinus halepensis Mill. forests in Central Greece

Pinus halepensis forests are among the forest ecosystems in the Mediterranean Basin most affected by fire. Their distribution across lowland areas, in particular along the wildland–urban interface, increases the need to understand their ecology and responses to fire regime for their effective management. Apart from the extremely flammable tree layer, in several stands of these forests there is an increased fuel load attributed to the well-developed understorey of evergreen sclerophyllous shrubs. Taking into consideration that, in contrast with the long period required for full development of post-fire-regenerating pines, these shrubs resprout vigorously within the first post-fire weeks, it is important to explore the temporal trend of fuel accumulation to determine the risk of a second fire across a burned landscape. Two post-fire chronosequences of, in total, 12 P. halepensis stands were considered for sampling in Central Greece. The first chronosequence corresponds to pine stands characterized by the dominance of evergreen sclerophyllous shrubs in the understorey (Type 1) whereas the second chronosequence corresponds to pine stands where the cover of such shrubs was lower (Type 2). This study helps in understanding the fuel dynamics according to the type of P. halepensis forest stand and to anticipate future biomass growth. The proposed equations are simple tools, enabling land managers to estimate understorey total fuel load easily by visually recording the cover and height of the evergreen sclerophyllous shrub component, to justify understorey fuel reduction measures.     

Rooting patterns and fine root biomass of Pinus pinaster assessed by trench wall and core methods

Variability of fine root (diameter < 2 mm) distribution was investigated in four 55 to 56-year-old Maritime pine (Pinus pinaster) stands using a combination of trench wall observations and destructive sampling. Our objectives were to assess patterns of fine root distribution, to estimate tree fine root biomass and to explore interactions with understorey vegetation in a gradient of relevant site conditions. Results showed that root density decreased with soil depth in all stands, and variability appeared to be highest in litter and subsoil layers especially where compacted soil layers occurred. Roots were clustered in patches in the top 0–50 cm of the soil or were present as root channels at greater depths. Cluster number, cluster size and number of root channels were comparable in all four stands. Overall fine root biomass at depths of 0–120 cm ranged from 2.7 to 7.2 Mg ha⁻¹ and was highest for the two driest stands. The use of trench wall records made it possible to reduce the variability of these estimates. Understorey species represented as much as 90% of the total number of fine roots in the upper layers, and the understorey formed a considerable proportion of the total ecosystem biomass, suggesting that understorey species are likely competitors for nutrients in this ecosystem. Further studies should focus on the interaction of the understorey and pine roots and the ecological significance of clustered roots and nutrient distributions.     

基于主成分、聚类与SVR组合算法的森林生物量估算方法研究

以孟家岗林场二类清查数据为基础,对1371个小班的11项指标进行主成分分析,并采用系统聚类法对小班进行分类,进而利用支持向量回归算法分别进行生物量模型训练.结果表明：7个主成分指标可反映87.995％的生物量信息;1371个小班可分为5类,各类训练模型的预测精度均在89％以上,且均以v-SVR模型为最优.在得到的5类生物量训练模型基础上估算林场森林乔木层生物量,无需分起源、树种、立地类型,能够在保证生物量估算精度的同时,大大减少工作量,可为区域生物量的估算提供一种新的方法.     

人工林林下植被的研究现状

本文从林下植被的演替时序及其与干扰的关系、林下植被与土层林木的关系及林下植被作用研究等3个重要侧面,系统总结了近20年来林下植被的研究现状与热点问题。在没有外界因子干扰的情况下,林下植被的演替将随着时间的推移与林分的发育同时进行,总体上呈现出发育－萎缩－发育的阶段。当受到外界的干扰后,林下植被的特征会发生改变,表现在生物量、数量、高度、盖度等方面的变化,而变化的幅度与干扰的类型和强度有密切相关;林下植被对上木的影响分为促进和竞争两个方面;目前对于林下植被的指示作用、地力维持与改良有着比较系统的研究,但对其水文效益、增加物种多样性与效益评价的研究有待深入。     

Carbon concentrations of tree components,forest floor and understorey in young Pinus sylvestris stands in north-western Turkey

Abstract

This study examines the carbon concentrations of various above-ground biomass components (stem, bark, living branch, dead branch, needle and above-ground biomass), the forest floor and understorey. The research was carried out on Scots pine (Pinus sylvestris L.) stands in north-western Turkey. Sample trees were cut, and forest floor and understorey samples were collected from the 13 sampling areas in the 31-year-old Scots pine stands. Carbon contents of these samples were determined. Carbon concentrations of all tree components were found to be higher than 50%. This value is referred to as the general carbon conversion factor (CF). The weighted mean carbon concentration was found to be 51.96%. Consequently, if the CF for a single tree is taken to be 50%, carbon storage in the above-ground parts of the tree would have been underestimated by 3.77%. Carbon concentration, which was 53.02% in needles, was reduced to 50.08% in the litter plus fermentation layer of the forest floor and to 40.08% in the humus layer owing to decomposition. In the understorey, carbon concentration was determined to be 47.64%. There was a significant difference between the carbon concentrations of the tree components, forest floor and understorey.     

Distribution patterns of tree,understorey, and detritus biomass in coniferous and broad-leaved forests of Western Himalaya,India

Forest biomass pools are the major reservoirs of atmospheric carbon in both coniferous and broad-leaved forest ecosystems and thus play an important role in regulating the regional and global carbon cycle. In this study, we measured the biomass of trees, understorey, and detritus in temperate (coniferous and broad-leaved) forests of Kashmir Himalaya. Total ecosystem dry biomass averaged 234.2 t/ha (ranging from 99.5 to 305.2 t/ha) across all the forest stands, of which 223 t/ha (91.9–283.2 t/ha) were stored in above- and below-ground biomass of trees, 1.3 t/ha (0.18–3.3 t/ha) in understorey vegetation (shrubs and herbaceous), and 9.9 t/ha (4.8–20.9 t/ha) in detritus (including standing and fallen dead trees, and forest floor litter). Among all the forests, the highest tree, understorey, and detritus biomass were observed in mid-altitude Abies pindrow and Pinus wallichiana coniferous forests, whereas the lowest were observed in high-altitude Betula utilis broad-leaved forests. Basal area has showed significant positive relationship with biomass (R² = 0.84–0.97, P < 0.001) and density (R² = 0.49–0.87). The present study will improve our understanding of distribution of biomass (trees, understorey, and detritus) in coniferous and broad-leaved forests and can be used in forest management activities to enhance C sequestration.     

基于不同立地质量的杉木生物量遥感估测

[目的]研究不同立地质量对杉木生物量遥感估测精度的影响,为进一步提高和完善森林生物量遥感监测体系提供一种新的思路和方法。[方法]以2007年建德市森林资源二类调查数据和TM影像为研究材料,采用蓄积量—生物量换算因子连续函数法计算杉木林生物量和地位级法评价立地质量等级,比较杉木立地质量好、中等、差和不分地位等级4种生物量遥感估测模型,并进行精度检验。[结果]表明:(1)以TM遥感影像主成分分析中第一主成分为自变量的模型拟合效果最好,决定系数R2均在0.69以上,最高0.855。(2)利用预留独立样本对模型精度进行验证,不分地位级总体估测精度为87.78%,分立地质量等级好、中、差3种类型总体估测精度分别为97.37%、95.82%、98.23%。分不同立地质量类型可以提高杉木生物量遥感估测精度。[结论]研究结果为森林生物量遥感估测提供一种改进的思路,且为提高森林生物量和碳储量遥感估测精度提供一种参考方法。     

The estimation of aboveground biomass and nutrient pools of understorey plants in closed Norway spruce forests and on clearcuts

The estimation model PhytoCalc allows a non-destructive quantification of dry weight and nutrient pools of understorey plants in forests by using the relationship between species biomass, cover and mean shoot length. The model has been validated with independent samples in several German forest types and can be a useful tool in forest monitoring. However, in open areas within forests (e.g. clearcuts), the current model version underestimates biomass and produces unreliable nutrient pool estimations. Thus, tissue density, as approximated by leaf dry matter content (LDMC), is systematically higher under high light compared to low light conditions. We demonstrate that the ratio of LDMC under clearcut conditions to LDMC under forest conditions can be used to adjust the PhytoCalc model to clearcut conditions. We investigated the LDMC ratio of five exemplary species commonly occurring on clearcuts. Integrating the square of the ratio as a correction factor improved estimates of biomass to more than 70% fit between observations and predictions. Results also suggest this ratio can be used to correct nutrient concentrations modelled in PhytoCalc, which tend to be overestimated in clearcuts. As morphological groups of plant species exhibit significantly different ratios, we advise using group-specific correction factors for clearcut adjustments in the future.     

Using cover measurements to estimate aboveground understorey biomass in Maritime pine stands

? Understorey plays a major role in forest fluxes and stocks balances, however this compartment is generally poorly quantified. Our objectives were to establish models to estimate understorey biomass using vegetation cover measurements and to investigate upscaling methodologies from stand to regional level.

? Understorey aboveground biomass measurements were undertaken in Maritime pine stands of mesohygric, mesic and dry moorlands in South West France.

? Average biomass stock in this compartment was estimated to 3.50 t DM ha^?1. The more abundant species groups varied with moorland types, with a higher relative contribution of herbaceous species (23.3%), bracken (59.2%) and mosses (31.6%) for mesohygric, mesic and dry moorlands, respectively. For each species group, we established significant relationships to estimate biomass using a volumetric index, based on cover and height measurements. No relationship between stand characteristics and understorey biomass was founded. We investigated the upscaling of these estimations to a several thousands hectare area using understorey cover measurements done along a regular spatial grid. The only significant correlation linked one satellite vegetation index to understorey biomass.

? We successfully developed empirical relationships to estimate the understorey biomass at the stand level. Further investigations could focus on the analysis of understorey variability over a finer space grid and the potential use of satellite vegetation indexes.