亚高山暗针叶林凋落物的分解过程

凋落物是森林生态系统的重要组成部分,其分解过程是森林生态系统养分循环的重要环节。准确测定凋落物的分解动态,对研究森林生态系统的格局和过程非常重要。本文的工作在贡嘎山高山生态系统观测试验站开展,对海拔3 000 m的峨眉冷杉(Abies fabri)林进行定位观测,并对峨眉冷杉林凋落物分解过程进行了长期测定。研究结果表明:(1)凋落物的分解速率是阔叶>针叶>枯枝,峨眉冷杉林的阔叶、针叶和枯枝等凋落物分解一半所需要的时间分别为6.8年、10.5年和14.5年,分解95%所需时间分别为29.3年、45.6年和63.1年;(2)无论阔叶还是针叶、枯枝,其有机碳含量均随着时间的推移而下降,而有机碳分解率均随着时间而增高;利用指数衰减模型,获得凋落物有机碳的分解系数是阔叶>针叶>枯枝;(3)在每年凋落物输入峨眉冷杉林林地时,其中的阔叶、针叶和枯枝已经开始分解,当年可释放的有机碳分别为52.18 kg·hm^-2、4.32 kg·hm^-2和0.67 kg·hm^-2,各类凋落物每年有机碳释放总量为61.13 kg·hm^-2,占凋落时有机碳量的6.58%。     

森林生态系统中凋落物的分解、积累与归还的模型计算

本文在森林生态系统生物量增长遵循Mitscherlich 模型的结果这一假定下,推导的模型对森林生态系统凋落物的年凋落量、年分解量及累积量进行了推算,并得到了很好的验证。该模型给出了林地凋落物贮量—年凋落量—年分解率三者是森林凋落物动态、养分循环的三要素的生物学意义,它们组成一个紧密联系的动态系统,若已知其中的任何二者,都可以推算出第三者。同时提出了用林地死根总量以及根系的分解速率来推算森林生态系统根系的年死量,为计算森林生态系统根系的生产力提供可靠方法。     

全球变暖对森林凋落物的影响

凋落物是森林生态系统中养分归还的主要形式,其分解决定着土壤有机物质的存储与周转。随着全球变暖日趋明显,气候变暖对森林凋落物的影响引起了人们的极大关注,取得了较多研究成果,但部分研究结果仍存在争议,研究亟待加强。文中分别从凋落物产量、结构和组成、分解速率等方面综述全球变暖对森林凋落物影响的研究进展,比较了全球变暖不同模拟研究方法的优缺点,提出统一研究方法、加强长期动态观测、强化森林凋落物对环境变化的适应机制研究等建议,以期为全面精准评估全球变暖对森林凋落物的影响提供科学参考。     

森林碳固定能力计算方法及长株潭区域碳年固定量估算

根据森林生态系统碳(CO2)平衡原理方程式[Fc=Nc(植物年净C)+Dc(凋落物C)+Mc(微生物C)+Ec(土壤动物及其它有机物C)-Rs(土壤放出C)],建立了森林生态系统碳(CO2)年固定量计算式:Fc=∑m∑nBEFcij·Xcij·11λi·Mkij·113-0.6Rij·Sij式中:Xcij———森林植物年净生产量;3+113Dcij+∑Hk=1j=1i=1Dcij———凋落物碳(CO2)固定量;Mkij———微生物自身碳素量;Rij———土壤呼吸放出CO2量;Sij———面积;i———森林类型序号;j———地域或土类序号。求算出长株潭地区森林生态系统年CO2固定量为3945.3×104t,是长株潭三市2000年工业燃料燃烧排放CO2总量的2.38倍。森林生态系统碳(CO2)固定能力,变幅在6.784～54.163t/(hm2·a-1)之间,大小排序为毛竹林>国外松林>阔叶林>四旁林>柏木林>马尾松林>杉木林>灌丛疏林>经济林。     

卷荚相思林分凋落物产量与林分生长相关性研究——林地自肥能力与森林生产力相关性研究

文章通过对卷荚相思试验林凋落物产量的收集与分析,试验林每年生长量的测定与计算,综合分析表明:①2～5a卷荚相思试验林在2003～2005年3a中,回归林地的凋落物产量为12208 kg/hm2,平均每月回归1017kg/hm2。②以整年计,3～5a生卷荚相思林分全年凋落物(枯叶)产量最高月份都出现在10月份,最低月份都出现在3月份。2003年最高月份凋落物产量为1411 kg/hm2,最低凋落物产量为16kg/hm2,全年平均每月凋落物产量为374kg/hm2。2004年最高月份凋落物产量为1216kg/hm2,最低凋落物产量为8kg/hm2,全年平均每月凋落物产量为320.7kg/hm2。2005年最高月份凋落物产量为647.8 kg/hm2,最低凋落物产量为56 kg/hm2,全年平均每月凋落物产量为322.6kg/hm2。而且,随着林龄的增加,凋落物最多的月份的凋落物产量也越来越少。③凋落物年度总产量与林分树高生长量以及胸径生长量相关性:随着林龄的增长,树高、胸径生长由快变慢,而每年每增加1m树高以及1cm胸径所需要的凋落物却是越来越多。④凋落物年度总产量与林分材积生长量相关性:随着林龄的增长,材积生长由快变慢,而每年每增加1m3所需要凋落物产量的是越来越少。从中可以知道凋落物产量的升降虽然对材积有影响,但影响不大。     

喀斯特森林植被自然恢复中凋落物现存量 及其碳库特征演化

采用空间代替时间的方法,研究了茂兰退化喀斯特森林自然恢复中凋落物现存量及其碳库特征.结果表明:随群落恢复凋落物现存量呈减少趋势,早期减幅大,中后期减幅小;随群落恢复凋落物现存量演化受地貌因子、群落生活史、土壤微生物的影响较大,受水热条件的影响较小;凋落物现存量生物量与其分解失重率、表层土壤微生物量碳有较强的负相关关系;凋落物分解失重率与表层土壤微生物量碳呈极强的正相关关系;随群落恢复凋落物现存量含碳率变化不显著,凋落物现存量碳密度变化规律与凋落物现存量变化规律一致,单位面积凋落物碳储量表现为碳源效应,且早期碳源效应较强、固碳能力不稳定,中后期碳源效应较弱、固碳能力稳定;凋落物碳密度(Y)与其现存生物量(x)的关系:Y=b.+b1x(b0、b1为常数).     

林火干扰对广东省2种典型针叶林森林生物碳密度的影响

[目的]定量研究不同林火干扰对森林生物碳库的变化规律,揭示林火干扰对森林生物碳密度的影响机制,为林火干扰后森林生态系统碳汇管理提供参考依据。[方法]以广东省亚热带2种典型针叶林为研究对象,采用相邻样地比较法,以野外调查采样与室内试验分析为主要手段,定量测定不同林火干扰强度对森林生物碳库(植被碳库和凋落物碳库)碳密度与碳分配格局的影响。[结果]林火干扰对亚热带2种典型针叶林的植被和凋落物碳密度有影响,均表现为对照>轻度林火干扰>中度林火干扰>重度林火干扰。轻度林火干扰对植被碳密度的影响差异不显著(P<0.05),而中度和重度林火干扰则显著降低了植被碳密度(P<0.05).相同林火干扰强度下,植被各组分碳密度的变化均表现为乔木最大。乔木碳密度在不同林火干扰强度下均呈现为对照>轻度林火干扰>中度林火干扰>重度林火干扰,而草本碳密度则呈现与乔木碳密度相反的变化趋势。林火干扰显著影响乔木和草本碳密度,亦对灌木碳密度产生了影响。不同林火干扰强度对凋落物碳密度的影响有所差异,但不同林火干扰强度均显著减少了凋落物碳密度(P<0.05),并随林火干扰强度的增加其减少幅度增大。[结论]林火干扰减少了植被和凋落物碳密度,进而对森林生态系统的碳密度产生重要影响。     

湖南省森林生态系统碳汇经济价值初探

通过利用立木蓄积量及森林面积等基本监测数据,对湖南省森林生态系统的碳汇能力及其经济价值进行了初步估算。结果表明:湖南省森林生态系统总贮碳量为2164.95Mt,年固碳量为12.73Mt,其经济价值分别为6603.10亿元和38.84亿元;湖南省森林生态系统平均碳密度为215.42t·hm-2。预计我省森林生态系统固碳增长潜力415.51Mt碳或1524.93MtCO2,由此产生的经济效益平均每年可达60.35亿元。同时还对湖南14个市州的森林碳汇及其经济价值分别进行了估算,并进一步对通过林业建设实现CO2减排进行了探讨。     

北亚热带6种森林类型凋落物分解过程中有机碳动态变化

运用凋落物野外分解模拟实验的方法,对北亚热带地区6种主要森林类型凋落物分解过程中有机碳的变化进行了研究,结果表明:(1)6种土地利用类型森林凋落物分解过程中,有机碳相对含量在分解初始阶段都呈现增加的趋势,表现为凋落物有机碳相对含量的积累过程;分解开始的第3～4个月后,凋落物有机碳相对含量下降;经过1 a的分解周期以后,粗放经营毛竹林凋落物有机碳相对含量变化最大,下降11.7%;(2)集约经营毛竹林凋落物有机碳数量从分解开始就减少,而其它几种类型分解初期有机碳数量都表现一个净积累的过程,然后才逐步释放;经过1 a分解周期以后,粗放经营毛竹林凋落物53.8%的有机碳净释放;凋落物有机碳释放速率由高到低的顺序为:粗放经营毛竹林、早竹林、杉木林、天然次生林、集约经营毛竹林、马尾松林;(3)6种土地利用类型森林凋落物在分解过程中,有机碳剩余率随时间变化的模型都极其显著地符合分解指数模型,因此都可以用指数方程表达;(4)影响凋落物分解的环境因子所发挥的作用不尽相同,凋落物的分解速率和温度之间呈现显著的正相关关系.     

我国森林凋落物分解研究进展

森林凋落物是指森林生态系统中,由地上植物部分产生并归还到地表面,作为分解者的物质和能量来源,借以维持生态系统功能的全部有机质的总称。文章综述了森林凋落物的概念、构成、分解的研究方法和模型、影响分解因素以及全球变化对凋落物分解的影响。凋落物分解是森林生态系统重要过程之一,受气候、凋落物性质、微生物等生物和非生物因子的影响。森林生态系统是陆地上最大的碳储库和最经济的吸碳器,而森林凋落物的分解对大气二氧化碳浓度增高、气候变暖和降水变化的反应,对深入理解森林生态系统土壤有机物形成和固氮能力十分重要。     

不同海拔岷江冷杉林凋落物量及其季节动态变化研究

本文对四川王朗国家自然保护区不同海拔岷江冷杉森林群落内的凋落物总量、各凋落物组分随海拔的变化及其季节动态进行了研究,结果显示,各凋落物组分和总凋落物的年产量在不同海拔间均无显著性差异,年总凋落物量在3 537.18~4 761.84 kg.hm-2.a-1,高于同一地区的相似群落,表明在该区域岷江冷杉林具有相对较高的生...     

Patterns of litterfall and return of nutrients across anthropogenic disturbance gradients in three subalpine forests of west Himalaya, India

The study was conducted to improve our understanding of the effects of forest disturbance on litterfall and patterns of nutrient return in three subalpine forest ecosystems (i.e. Betula utilis-dominated, Abies pindrow-dominated, and Acer mixed broadleaf) of Indian west Himalaya. Total litterfall (t ha⁻¹ yr⁻¹) ranged between 2.6–3.6 and 2.1–2.6 for pristine and degraded stands, respectively. Whereas total litterfall decrease from pristine to degraded stand was about 25–30% in B. utilis and Acer mixed-broadleaf forests, the level of disturbance did not affect total litterfall in A. pindrow (coniferous) forest. Nutrient (N, P, and K) concentrations in litter components of the forests studied also varied across forest types and disturbance intensities. For pristine stands, among all the forests, return of total nutrients via litterfall was higher. The study revealed that patterns of litterfall and nutrient return in the forests studied were sensitive to intensity of disturbance, although sensitivity varied among forest types and nutrient contents. Increased intensity of disturbance greatly affected the total annual amount of nutrient return in broadleaf forests. Maximum impact was recorded in B. utilis forest with a significant decline in nutrient return from pristine to degraded stands (i.e. 64% for N, 38% for P, and 67% for K). Corresponding values for decline in Acer mixed forest were 17, 13, and 33% for N, P, and K, respectively, whereas in A. Pindrow forest N return was 15% higher and P return was 33% lower. This study indicates that the litterfall and litter nutrient concentrations in these forests are sensitive to the intensity of disturbance, which affects the amount of nutrient return. This will have a strong bearing on forest nutrient cycling.     

Estimation of biomass,net primary production and net ecosystem production of China's forests based on the 1999–2003 National Forest Inventory

Abstract

The National Forest Inventory (NFI) is an important resource for estimating the national carbon (C) balance. Based on the volume, biomass, annual biomass increment and litterfall of different forest types and the 6th NFI in China, the hyperbolic relationships between them were established and net primary production (NPP) and net ecosystem production (NEP) were estimated accordingly. The results showed that the total biomass, NPP and NEP of China's forests were 5.06 Pg C, 0.68 Pg C year^?1 and 0.21 Pg C year^?1, respectively. The area-weighted mean biomass, NPP and NEP were 35.43 Mg C ha^?1, 4.76 Mg C ha^?1 year^?1 and 1.47 Mg C ha^?1 year^?1 and varied from 13.36 to 79.89 Mg C ha^?1, from 2.13 to 9.15 Mg C ha^?1 year^?1 and from ?0.16 to 5.80 Mg C ha^?1 year^?1, respectively. The carbon sequestration was composed mainly of Betula and Populus forest, subtropical evergreen broadleaved forest and subtropical mixed evergreen–deciduous broadleaved forest, whereas Pinus massoniana forest and P. tabulaeformis forest were carbon sources. This study provides a method to calculate the biomass, NPP and NEP of forest ecosystems using the NFI, and may be useful for evaluating terrestrial carbon balance at regional and global levels.     

Phosphorus cycling in primary and secondary seasonally dry tropical forests in Mexico

? Primary forests in the seasonally dry tropical regions of Mexico are disappearing under land-use pressure, creating a mosaic of secondary forests of different ages.

? In this study we measured the aboveground litterfall phosphorus (P) fluxes, litter-layer and soil P pools to compare the P cycles in primary and secondary seasonally dry tropical forests. Our hypothesis was that the previous agricultural land use of secondary forests would bring about a lower P flux in the litterfall, lower soil P pool, and higher nutrient resorption proficiency than in primary forests, as well as an increase of relative amounts of available P provided by the soil with forest aging.

? The expected litterfall P flux increase in the secondary forest following a previous agricultural land use did not occur. Phosphorus return to the soil by aboveground litterfall was unaffected by the succession stage of the forest. In addition, the total soil P pool did not change with forest age. However, available soil P (bicarbonate P-inorganic and P-organic pools) and hydroxide inorganic P pools were higher in primary than in secondary forest soils. Phosphorus concentration in litterfall increased significantly with forest age, suggesting that P is cycled more efficiently (by a higher nutrient resorption proficiency) when soil available P is less abundant. Despite these differences among forests, the results of our study gave evidence that P requirements by plants in primary and secondary forests are sufficiently met by the accumulation of dissolved (water extractable) P in the forest floor during the dry season and by soil bicarbonate-P pools.

? Our study on the effects of land cover change on P cycling, following the discontinuation of agricultural practices, leads to the conclusion that this ecosystem P dynamics will vary depending on the successional stage of the forests, and is strongly influenced by the seasonal rainfall pattern which determines plant-available P.

     

杉木、观光木混交林凋落物能量归还量初步研究(英文)

通过对杉木、观光木混交林及杉木纯林群落凋落物的能量年归还量及能流的季节变化进行研究 ,结果表明 ,混交林凋落物的能流量达 12 .6 4 8× 10 6J·m-2 ,比纯林的高 4 .2 % ;在各目的树种凋落物组成中 ,落叶能流量均占大部分 ;混交林和纯林群落太阳能进入凋落物的转化效率分别为 0 5 6 %和0 5 4 % .混交林和纯林中杉木凋落物能流一年中分别在 3,8和 12月出现 3个高峰 ,其中落叶、落枝、落花和落果能流的月变化与之相似 ,这与杉木的小枝整体凋落方式有关 ;混交林中观光木凋落物能流在1,5和 8月出现高峰 ,其中落叶和落枝能流月变化与之相似 ,但落花能流仅出现在 3～ 5月 ,而落果仅发生在 1月和 3月 .各群落凋落物能流月变化模式与其中杉木凋落物能流变化模式基本一致 .混交林和纯林凋落物能流的季节变化为春季 >冬季 >夏季 >秋季 ,但混交林凋落物能流量季节间变动小于纯林的 .     

China’s Forests and Their Impact on Global Carbon Cycle

Forests have multiple benefits and functions, including mitigation of climate change. The impacts of forests on the global carbon cycle include forests as carbon sinks, wood-based products as carbon sinks, bio-energy, and production and use of non-timber products. In the past decades, forest cover of China has increased from 8.6% to 18.21% by large-scale afforestation and conversion of cropland into forests. Forest biomass carbon (C) stock increased from 4.3 Pg C (1 Pg C = 1 015 g C) in the early 1980s to 5...     

Forest carbon sequestration in China and its benefits

Carbon sequestration is important in studying global carbon cycle and budget. Here, we used the National Forest Resource Inventory data for China collected from 2004 to 2008 and forest biomass and soil carbon storage data obtained from direct field measurements to estimate carbon (C) sequestration rate and benefit keeping C out of the atmosphere in forest ecosystems and their spatial distributions. Between 2004 and 2008, forests sequestered on average 0.36 Pg C yr^?1 (1 Pg = 10¹⁵g), with 0.30 Pg C yr^?1 in vegetation and 0.06 Pg C yr^?1 in 0–1 meter soil. Under the different forest categories, total C sequestration rate ranged from 0.02 in bamboo forest to 0.11 Pg C yr^?1 in broadleaf forest. The southwest region had highest C sequestration rate, 30% of total C sequestration, followed by the northeast and south central regions. The C sequestration in the forest ecosystem could offset about 21% of the annual C emissions in China over the same period, especially in provinces of Tibet, Guangxi, and Yunnan, and the benefit was similar to most Annex I countries. These results show that forests play an important role in reducing the increase in atmospheric carbon dioxide in China, and forest C sequestration are closely related to forest area, tree species composition, and site conditions.     

Comparison of litterfall production in three forest types in Jeju Island,South Korea

Litterfall, which is influenced by physical and biological factors, is a major pathway for carbon and nutrient cycling in forest ecosystems. The purpose of this study was to investigate monthly litterfall production in three forests in Jeju Island differentiated by forest composition and precipitation: Cheongsu(Quercus glauca as the dominant species;low precipitation), Seonheulb(Q. glauca as the dominant species;high precipitation), and Seonheulm(Q. glauca and Pinus thunbergii as the dominant species;high precipitation). Litterfall was collected monthly from April to December 2015 and divided into leaf litter, twig, bark, seeds, and unidentified materials.Seasonal patterns of litterfall production varied across stands according to their species composition. However,the amount of leaf litterfall and total litterfall were comparable among stands, ranging from 362 to 375 g m-2 for leaf litter and 524 g m-2 to 580 g m-2 for total litterfall.Oak leaf litter in May was the highest in all stands, while needle litter was the highest in December in Seonheulm.High twig litterfall in July may be attributable to high rainfall with strong winds and storms during the rainy season. Although forest type and climate factor had no influence on litterfall amounts in this study, the pattern of litterfall production was species dependent, suggesting diverse effects on carbon and nutrient cycling in these forests.     

Litterfall production in forests located at the Pre-delta area of the Paraná River (Argentina)

? The objectives of this study were to measure litterfall production of the four floodplain forest types and to analyze the relationship between litterfall (forest type, dominant species, and organic fractions) and flood pulses.

? Litterfall production was measured in two mono-specific stands of Salix humboldtiana or Tessaria integrifolia, respectively, and two mixed forests dominated by A. inundata or Nectandra angustifolia, during 1998 and the 2000–2002 periods.

? Mono-specific stands presented similar productivities (6.8 and 6.5 Mg dry matter ha^?1 y^?1, respectively), but differed significantly from the two other. The highest litterfall production was obtained during the large flood that occurred during 1998, decreasing later throughout the study period. Leaves were the dominant fraction of litterfall, followed by branches, flowers, and fruits.

? Only S. humboldtiana, T. integrifolia and A. inundata forests showed distinct patterns of litterfall production, depending on the flooding pulse. N. angustifolia did not show a distinctive litterfall pattern.

? The forests studied here presented patterns of litter production associated with the flood pulse according to its location along a topographic gradient, that controls the litter productivity of these forests.