海南沿海木麻黄人工林林下植被生物量

采用样地调查法,对海南沿海木麻黄人工林林下植被进行调查、并测定其生物量。结果表明:木麻黄人工林林下灌木层地上部分生物量大于地下部分生物量,草本层地下部分生物量大于地上部分生物量;灌木层各器官的生物量分配规律为干(3.41 t·hm-2)根(3.19 t·hm-2)叶(2.10 t·hm-2)枝(1.41 t·hm-2),干和根的生物量比例较大;灌木层、草本层生物量与总生物量均呈正相关关系,灌木层生物量与草本层生物量则呈负相关关系,说明灌木层与草本层存在竞争。     

14年生观光木人工林生物量初步研究

为了填补观光木在生物量方面研究的空白,提高人们对广西珍贵树种的认识,对广西南宁良凤江国家森林公园于1 983年种植的观光木人工林的生物量进行了测定研究,分析了观光木人工林不同径阶平均单株生物量变化及其分配规律、林分生物量、生产力,并研究了林木各器官之间的相关关系.结果表明:观光木人工林林分的生物量为72.05t·hm_2,乔木层的生物量为59.01t·hm_2,比重很大,达到了81.90％,其次是根系,占22.55％.林下灌木层、草本层及腐殖质层生物量分别为8.86t·hm-2、1.99t·hm-2、2.19t·hm_2.林分内各部分生物量大小排序依次为:乔木层＞灌木层＞腐殖质层＞草本层.为观光木人工林研究提供理论科学依据.     

楠木人工林生态系统生物量、碳含量、碳贮量及其分布

对32年生楠木人工林生物量、碳含量、碳贮量及其空间分布进行测定.结果表明;楠木林分平均生物量为174.33 t·hm-2,其中乔木层为166.73 t·hm-2,占林分生物量的95.6%;楠木林分生态系统各组分碳含量为树干0.576 9 gC·8-1,树皮0.465 4 gC·g-1,树枝0.523 2 gC·g-1,树叶0.495 8 gC·g-1,树根0.493 1 gC·g-1,灌木层0.498 9gC·g-1,草本层0.473 3 gC·g-1,苔藓层0.414 3 gC·g-1,枯落物层0.388 2 gC·g-1;土壤碳含量平均值为0.013 9gC·g-1,随土层深度增加各层次土壤碳含量逐渐减少;楠木林分生态系统总碳贮量为227.59 t·hm-2,其中乔木层91.33 t·hm-1,占楠木林分生态系统总碳贮量的40.13%,灌木层0.38 t·hm-2,只占0.17%,草本层1.71 t·hm-2,占0.76%,苔藓层0.63 t·hm-2,占0.28%,枯落物层0.66 t·hm-2,占0.29%,林地土壤(0～80 cm)碳贮量为 132.88t·hm-2,占58.40%;其碳库空间分布序列为土壤(0～80 cm)＞乔木层＞草本层＞枯落物层＞苔藓层＞灌木层;楠木林分净生产量为8.570 6 t·hm-2a-1,其中乔木层净生产量为6.669 1 t·hm-2a-1,占林分总量的77.82%.楠木林分碳素年固定量4.253 6 t·hm-2a-1,其中乔木层碳素年固定量3.573 6 t·hm-2a-1,占林分总量的84.01%.     

南亚热带不同树种人工林生物量及其分配格局

通过收获法和建立的单木相对生长方程研究了南亚热带5种树种人工林乔、灌、草不同组分的生物量及其分配。结果表明:在立地条件相似,林龄和经营管理措施相同的情况下,不同树种人工林生物量有较大差异,表现为米老排林(404.95 t·hm-2)火力楠林(376.61 t·hm-2)马尾松林(239.94 t·hm-2)红椎林(231.01 t·hm-2)铁力木林(181.06 t·hm-2)。林分生物量空间分布格局以乔木层为主,占总生物量的87.71%97.86%;其次为地表凋落物层,占1.96%10.90%;灌木层和草本层最低,仅占0.02%1.09%。林分乔木层各器官的生物量分配格局总体呈树干生物量所占比例最大,根或枝所占比例次之,再其次是干皮,叶生物量最低。林下灌木层、草本层和地表凋落物层生物量在不同林分间的差异均较大,其中,灌木层生物量以红椎林和马尾松林较高,火力楠林和米老排林较低,铁力木林最低;草本层和地表凋落物层表现出相似的规律,即马尾松林最高,红椎林其次,米老排林、火力楠林和铁力木林较低。     

华北落叶松人工林生物生产力研究

以华北落叶松人工林为研究对象,选择18a、22a、38a等3个不同林龄的林分,每个林龄林分设置15块样地。通过样地调查,对华北落叶松人工林的林分生物量、林下植被层生物量、林分净生产力进行研究,以揭示其生物生产力。结果表明：华北落叶松人工林林分生物量随着林龄的增加而增加,18a、22a、38a的林分生物量分别为94．58t／hm2、101．19t／hm2、216．25t／hm2。各器官的生物量分配,以干材所占的比例最大,达到51．36％以上;华北落叶松人工林林下植被层中凋落物层与灌木、草本层的生物量也随着林龄的增加而不断积累;华北落叶松森林净生产力表现为乔木层的净第一生产力、不同林龄阶段的华北落叶松人工林植被净生产力均较高,达到4．60t／（hm2·a）以上,其中干材的净生产力积累最快,为2．36～3．20t／（hm2·a）。     

会同第二代杉木人工林林下植被生物量分布及动态

对会同第2代杉木人工林速生阶段林下地被物生物量进行了2a的定位研究,探讨了杉木林林下灌木层、草本层的生物量动态变化。结合幼林期林下地被物生物量的特征,分析了第2代杉木林林下活地被物生物量的动态变化特征。结果表明:13年生林分中灌木层生物量为521 89kg·hm-2,草本层为1429 71kg·hm-2;14年生林分中灌木层生物量为372 69kg·hm-2,草本层为897 10kg·hm-2,2a中,灌木层各组分生物量大小顺序都为根>茎>叶;草本层生物量的大小顺序为地下部分>地上部分。在杉木14a的生长过程中,林分5年生时,活地被物生物量最大,为3089 62kg·hm-2,14年生时最小,为1269 79kg·hm-2。     

豫南35年生马尾松林生态系统碳库特征及其分配

对豫南35年生马尾松林生态系统的生物量、碳贮量及其空间分布特征进行研究。采用分层切割法和相对生长方程计算乔木层生物量和林下植被生物量,C、N元素分析仪测定碳含量。研究结果表明:35年生马尾松林生态系统的总生物量平均为228.6 t.hm-2,其中乔木层生物量占88.9%,灌木层占7.7%,草本层占0.1%,凋落物层占2.7%;马尾松林生态系统总碳库为218.11 t.hm-2,其中植被总碳贮量为127.69 t.hm-2,土壤有机碳库为90.42 t.hm-2;乔木层碳库(115.52 t.hm-2)占生态系统碳库的52.96%,灌木层占3.80%,草本层占0.28%,现存凋落物层占1.50%,矿质土壤层碳库占生态系统碳库的41.46%。     

杉木林林下植被生物量影响因素

通过收集杉木林林下植被生物量数据,分析杉木林林下植被生物量与年平均温度、年降水量、林分年龄、林分密度、乔木层生物量、灌木层生物量、草本层生物量、枯枝落叶层现存量等8个因子的相关关系。结果表明,林下植被生物量与林龄、乔木层生物量、灌木层生物量、草本层生物量、枯枝落叶层现存量呈显著正相关,其中以与草本层生物量相关性最大,与林分密度呈负相关,而与年均温、年降水量无显著相关。多元线性回归分析表明,林龄、林分密度、草本生物量可解释枯枝落叶现存量变化的90.6%。     

三峡库区主要植被生物量与生产力分配特征

在调查104块样地的基础上,利用95株标准木的树干解析数据,选择主要生物量生长模型,对三峡库区主要植被生物量和生产力的分配规律进行研究.结果表明:1)在各树种生物量组成中,干材生物量最大,占总生物量的44.46%～63.07%,而皮、枝和根生物量比例间的大小关系因树种不同而有所差异;2)所有树种干生物量比例与枝和叶生物量比例存在显著的线性负相关,而枝和叶生物量之间存在明显的正相关,随着单株林木生物量增加,针叶树种干和皮生物量比例会随之增加,但枝、叶和根的生物量比例则有所下降;3)各林分生物量为75.38～191.82t·hm-2,乔木层(67.57～179.00 t·hm-2)>枯落物层(3.95～11.61 t·hm-2)>灌木层(2.40～8.35 t·hm-2),乔木层和枯落物层生物量低,有利于灌木层生物量的生长;4)各林分生产力为4.78～11.07 t·hm-2a-1,常绿阔叶林最高,柏木林最低,混交林的生产力高于纯林,其中针阔混交林的生产力又高于针叶混交林.     

西藏色季拉山原始冷杉林生物量及其分布规律

采用样地调查及标准样木收获法,研究西藏色季拉山原始冷杉林乔木层、灌木层、草本层、死亡木、凋落物层的生物量及其分配规律.结果表明:冷杉林生态系统总的生物量为424.52 t·hm-2,其中乔木层生物量最高,为300.02 t·hm-2,占总生物量的70.67%,其次是死亡木111.53 t·hm-2,占总生物量的26.27%,灌木层与草本层生物量较低,分别为2.59和0.18 t·hm-2,所占比例分别为0.61%和0.04%.乔木层中,树干、皮、枝、叶与根的生物量分别为194.59、33.96、20.22、12.39与38.48 t·hm-2.随着树木生长,树干生物量所占比例增大,而枝、叶比例减小.     

Armillaria ostoyae in managed coniferous forests in Kastamonu in Turkey

Although several Armillaria species have been reported in Turkey, there is little information about their ecology in Turkish forests. In this study, we investigated five forest stands, approximately 5–74 ha in size, in Kastamonu province in the Black Sea Region of Turkey for the presence of Armillaria species in stumps and logs. The stands were mixed Abies nordmanniana ssp. bornmülleriana and Pinus sylvestris forests managed using a selective cuttings system; the proportion of fir in the total number of stems and stumps ranged from 36 to 98%. Based on sequence analysis of the internal transcribed spacer and intergenic spacer regions of the rDNA, all rhizomorphs sampled from the stumps and logs were of Armillaria ostoyae. The size of the genets was estimated with random amplified microsatellites analysis of the isolates and ranged from single stumps to approximately 450 m². One to seven genets were found in each stand. These results indicate that the genets had arisen from spores and vegetative spread was limited on most sites.     

上海中央公园特大银杏树白蚁防治探讨

通过对上海松江中央公园内65株特大银杏树白蚁为害情况的调查,发现该公园银杏受害率为100%,其中存在活白蚁的银杏占总量的56.9%,采用毒土处理、粉剂疗法、建立白蚁监测点等措施,经过两次灭杀,活白蚁的灭杀率达到92.3%和93.3%,从而使存在活白蚁银杏树的比例从56.9%下降到2.7%,白蚁发生情况明显降低。       

我国食品中农药残留研究进展

随着人们安全健康意识提高,食品中农药残留问题更加受到重视,本文综述了样品预处理研究进展及农药残留快速检测技术研究进展,并简单分析介绍各种方法的优缺点。     

建平半干旱地区石质山地造林技术研究

研究了不同植物在石质山地的造林成活率、土壤化学性质随造林年限的变化和造林措施对土壤化学性质和植物胸径、树高年净生长量的影响。结果表明：不同植物在石质山地的成活率在21%～85%之间,其中白榆和沙打旺的成活率分别为81%和85%,而小叶杨、刺槐、栾树的成活率均在70%左右;植被能明显提高石质山地不同土层的有机质、全N、P2O5含量,但提高程度随土层深度、养分种类和造林年限的不同而不同;在同一土层,生物复合肥料、菌剂和保水剂均显著提高土壤有机质含量（p〈0.01）并显著降低土壤P2O5含量（p〈0.01）;只有保水剂可引起土壤全K含量的明显升高;生物复合肥料、菌剂和保水剂均显著提高白榆、小叶杨、刺槐、栾树树高和胸径的年净生长量,但保水剂的提高程度最高。     

植物DNA甲基化研究进展

植物经常暴露在各种生物和非生物的胁迫之下,这些胁迫会影响植物的生长发育和繁殖并最终导致植物死亡。为了抵御不利的环境条件,植物已经进化出复杂而精细的网络来感知胁迫并激活防御系统。为此,植物激活许多信号转导通路,这些信号转导通路可以改变一些胁迫响应基因的表达,从而引起植物形态、生理和生化的改变以适应逆境。DNA胞嘧啶甲基化是高等真核生物的主要表观遗传机制之一,在维持基因组稳定性和调节基因表达方面起着关键作用。表观遗传变异比遗传变异更为灵活。一旦环境条件发生变化,为了适应新的环境植物都会发生表观遗传的改变。许多研究表明DNA甲基化参与植物的发育和应激反应。基于相关研究对DNA甲基化进行了综述,对植物逆境胁迫有重要意义。     

木材碳封存研究进展

碳封存可以分工业封存和生物封存, 工业封存包括地质封存、海洋封存、矿石碳化以及工业循环利用, 这些方法能快速回收CO₂, 但工艺流程技术复杂, 成本较高。木材碳封存是生物碳封存的一种类型, 树木光合作用吸收的碳主要存贮在木材中。运用木材密度、微密度等检测仪器, 通过确定木材密度变化, 结合其含碳率来计量木材的碳封存过程以及封存过程中碳的分配格局, 同时研究其与环境因子的相关性, 可以为研究森林的碳吸收动态提供便捷的方法和科学的依据。     

Tree regeneration in patch cutting in Norway spruce stands in northern Finland

The study focused on the success of regeneration on patch cuts in spruce-dominated stands in terms of stocking and tree height. It was based on an experiment in the Kainuu region in northern Finland. The experimental design included 8 stands with 58 clearcut patches of variable size (0.09–0.37?ha), on which either natural regeneration without site preparation or site preparation and planting of Scots pine was applied. A regeneration survey was conducted 13–15 growing seasons after treatments. Patches without site preparation had been restocked quite well from natural seed sources. The average number of trees was about 11,000?ha^?1, of which 1700?ha^?1 crop trees. With site preparation and planting, the stocking levels were also very high, 25,000 and 2100?ha^?1, respectively. One hundred percent of the planted patches and 75% of the naturally regenerated patches had an acceptable density. Restocking was equally good across the range of patch sizes. Tree growth had been somewhat slower in the smallest patches than in the largest ones in the range. Natural regeneration was capable of yielding good regeneration results in most patches, especially when site preparation was applied. Stocking levels and height development were higher yet in the planted patches.     

Changes in micropores in dry wood with elapsed time in the environment

To investigate the changes in microstructures of wood with elapsed time in the environment, CO₂ adsorption onto dry wood was measured at ice-water temperature (273 K) for samples aged from 0.1 years to over 1000 years. The micropore size distribution was obtained using the Horvath-Kawazoe method. Micropores smaller than 0.6 nm in wood decreased in number with elapsed time in the environment, and a negative correlation was found between cumulative pore volume for pores smaller than 0.6 nm and elapsed time in the environment. Cumulative pore volume in the 1000-year sample was almost half of that in the 0.1- year sample. Micropores smaller than 0.6 nm in wood with a few decades or more of elapsed time increased in number after rewetting and drying. Consequently, microstructures of wood with longer time elapsed in the environment were considered to be more stable, because of longer-term thermal motion and possibly more repeated moisture adsorption and desorption and/or temperature variation in the environment.     

Natural regeneration in patch clear-cutting in Picea abies stands in Southern Finland

Abstract

The success of natural regeneration on patch clear-cuts in Norway spruce stands in Southern Finland was examined in terms of stocking and tree height. The experiment was established in mature spruce stands in the submesic Myrtillus (MT) site type. In each of the eight study sites, three plots were treated with clear-cutting and planting, clear-cutting with partial tree retention and planting, and patch clear-cutting without site preparation, respectively. In three of the study sites, one plot with patch clear-cutting and site preparation was established. Each plot was 1 ha, out of which three patches of 40×40 m were clear-cut in the patch treatments. 10–11 years after cutting, the patches had on average 1316 crop trees ha^–1, of which 91% were spruces. Some 27% of the stands were up to the target stocking level (≥1600 ha^?1), and 36% were at least satisfactory (≥1300 ha^?1). Site preparation did not yield greater stocking levels on patches, but that result is ambiguous due to a difference in initial stocking. The average spruce tree height in the patches (0.76 m) was much smaller than in the case of clear-cutting and planting (2.42 m). In conclusion, the patches had been restocked tolerably well with spruce and birch for practical purposes during the 10- to 11-year period, but the regeneration process had been very slow compared to clear-cutting and planting.