广西猫儿山水青冈天然林凋落物的持水特性

采用野外调查和室内浸泡法对猫儿山水青冈(Fagus longipetiolata)天然林不同分解层凋落物的储量、持水量、持水率和吸水速率进行研究。结果表明,未分解层、半分解层和全分解层的干凋落物储量分别为1.02、1.07、2.28 t/hm2。不同分解层凋落物的持水量和吸水速率在整个浸泡试验过程中均表现为全分解层半分解层未分解层;持水率表现为半分解层未分解层全分解层。方程拟合结果表明,不同分解层的凋落物持水量、持水率与浸泡时间呈对数关系;凋落物吸水速率与浸泡时间呈幂指数关系。     

马尾松两种林型土壤养分特征及其与凋落物质量的关系

【目的】研究土壤养分和地被层凋落物养分含量的差异,为马尾松人工林营林措施及地力维持提供科学依据。【方法】以鼎湖山两种典型林型(马尾松纯林和马尾松-黧蒴混交林)为研究对象,对比分析0~60 cm土层的土壤养分含量及地被层凋落物养分含量的差异,探索凋落物质量如何影响土壤养分。【结果】1)林型对土壤有机质、全氮和硫酸根含量有显著影响(P<0.05),对土壤全磷、交换性K+、Ca2+和Mg2+有极显著影响(P<0.01),混交林土壤养分含量(除硝态氮含量和交换性H+含量以外)均高于纯林。2)相同林型不同土层间土壤养分含量差异极显著(P<0.01),其中,土壤有机质和全氮含量随土层的加深而递减,且主要聚集在0~10 cm土层,表聚效应十分明显。3)纯林凋落物有机碳、全氮、C/N和全磷等含量高于混交林;相同林型不同分解层凋落物有机碳、全钙和全镁含量有显著差异(P<0.05),均表现为未分解层>半分解层>腐殖质层。4)土壤养分与地被层凋落物质量的RDA分析表明,0~10 cm土层土壤养分与腐殖质层有机碳呈极显著负相关(P<0.01),与腐殖质层C/N呈显著负相关(P<0.05);在10~20 cm土层,土壤养分与腐殖质层有机碳呈极显著负相关(P<0.05)。【结论】纯林的土壤养分低于混交林的主要原因是纯林凋落物具有较高的C/N和有机碳含量。     

亚热带不同植被恢复林地凋落物层碳、氮、磷化学计量特征

【目的】探究不同植被恢复阶段林地凋落物层现存量及其碳(C)、氮(N)、磷(P)化学计量的差异,为亚热带地区退化林地的植被恢复和管理提供科学依据。【方法】采用空间代替时间的方法,在位于亚热带丘陵区的湖南省长沙县选取地域相邻、环境条件基本一致的4种处于不同植被恢复阶段林地:檵木-南烛-杜鹃灌草丛(LVR)、檵木-杉木-白栎灌木林(LCQ)、马尾松-柯(又名石栎)-檵木针阔混交林(PLL)、柯-红淡比-青冈常绿阔叶林(LAG)作为一个恢复序列,设置固定样地,按未分解层、半分解层和已分解层采集凋落物层分析样品,测定凋落物层现存量以及不同分解层凋落物C、N、P含量及其化学计量比。【结果】1)凋落物层及其各分解层凋落物的现存量总体上随着植被恢复而增加,同一林地不同分解层表现为:已分解层>半分解层>未分解层,不同分解层之间的差异随着植被恢复而增大。2)凋落物层C含量以PLL最高,LCQ最低,而N、P含量总体上随着植被恢复而增高;C、N、P含量随着凋落物的分解而下降。3)无论是整个凋落物层C储量还是各分解层凋落物C储量,均以PLL最高,其次是LAG,LVR最低,而N、P储量随着植被恢复而增高。4)整个凋落物层以及各分解层凋落物的C/N比值均表现为:PLL>LVR>LCQ>LAG,而C/P、N/P比值总体上随着植被恢复呈下降趋势;C/N、C/P、N/P比值基本上随着凋落物的分解而下降。【结论】随着植被恢复,凋落物层现存量及其N、P含量增加,C/N、C/P、N/P比值下降,体现了生态系统物质循环随着植被恢复逐渐优化。     

思茅松人工林凋落物量及其分解状况研究

经对普洱市清水河5种不同密度6年生思茅松人工林的凋落物量及分解动态进行研究,结果表明:思茅松人工林年凋落物量随密度增大而递增;5种思茅松人工林月凋落规律相似,呈单峰型变化,在全年间,3~4月的凋落物量占全年的68.31%~73.51%,其余各月比较低;思茅松人工林凋落物归还养分的多少与凋落物量密切相关,人工林全N的归还量最高,全Mg的归还量最低,5种大量元素归还量的顺序为:N>P>Ca>K>Mg;思茅松人工林凋落物分解分两个阶段,旱季凋落物分解速度相对较慢,雨季凋落物快速分解,整个分解阶段呈现"由慢到快"的规律,年分解率受当地气温和降水的影响较大。     

滇中亚高山森林林下植被和凋落物生态化学计量特征

[目的 ]了解磨盘山区域森林生态系统典型林分林下植被层和凋落物层各组分的C、N、P化学计量比格局,探究物种与器官对林下植被层和凋落物层C、N、P化学计量特征的影响,以期为森林生态系统养分再分配提供理论参考。[方法 ]选取滇中亚高山5种典型森林为研究对象,通过野外采集不同森林林下植被和凋落物样品,对其林下植被层各器官和凋落物层各组分C、N、P生态化学计量特征进行研究。[结果 ]5种林分的林下植被层(灌木叶、茎和根,草本地上和地下部分)和凋落物层(未分解层、半分解层、完全分解层)的C含量变幅分别为410.17～561.08、81.47～625.80 mg·g~(-1),N含量分别为3.07～15.89、9.87～17.50 mg·g~(-1),P含量分别为0.35～0.90、0.37～0.93 mg·g~(-1)。灌木层C、N、P含量除云南松林外均表现为叶根茎,草本层的C、P表现为地下部分地上部分,N含量则相反;凋落物层N、P含量表现为完全分解层半分解层未分解层,C含量与之相反。[结论 ]滇中亚高山典型森林中5种林分林下植被层生长比较缓慢,受到N和P的同时限制;凋落物分解速率偏慢,养分循环能力较低。因此,在森林抚育措施中,可考虑适当保护林下植被,提高土壤肥力,维持其长期稳定生产力。     

不同立地条件下华北落叶松叶凋落物的分解特性

采用凋落袋法,研究2种立地条件下不同林分密度华北落叶松人工林叶凋落物基质质量、分解速率的差异。结果表明:海拔与坡度是造成2种立地(地位级Ⅲ,Ⅳ)差异的主要因子,华北落叶松叶凋落物季节失质量率均表现出双峰曲线,且在秋季失质量率最高。2种立地条件下,叶凋落物半衰期分别为2.57,2.67年,完全分解分别需要11.09,11.24年。叶凋落物年平均失质量率、分解速率及初始无机养分含量均表现出立地Ⅲ高于立地Ⅳ。与立地Ⅳ相比,在立地Ⅲ下,C/N均值、木质素含量均值更有利于凋落物分解。经t检验分析,2种立地条件下叶凋落物初始无机养分含量之间并无显著差异性,而有机养分中木质素含量、有机碳含量之间差异显著(P<0.05)。相关分析表明:凋落物分解速率与全碳、C/N、凋落物层厚度呈极显著负相关,相关系数分别为-0.735,-0.569,-0.758。叶凋落物质量指标表明:在立地Ⅲ条件下,林分密度为1675株·hm-2最为有利于凋落物分解;在立地Ⅳ条件下,则以林分密度1300株·hm-2最为有利于叶凋落物分解。     

天然檫木混交林的生物量及营养元素分布——Ⅱ.营养元素的空间分布

对沅陵县保留擦木较多的天然混交林的营养元素空间分布进行分析测定,结果表明,擦木个体的营养元素含量因组织器官不同而发生变化,其中枝的养分含量随枝龄的增大而明显减少,根的养分含量表现为细根>粗根>大根>根头。其他主要混交树种,也表现为与擦木大体相一致的规律,在各混交类型中,林木生存空间的养分元素总贮量为1.9～3.8t/10~4m~2,其中乔木层为1.2～2.8t/10~4m~2,占林分总贮量的65～80%;下木层和草本层为0.2～0.5t/10~4m~2,占8～15%;枯枝落叶层为0.3～0.6t/10~4m~2,占10～24%。这些数据,为培育人工檫木混交林提供了可比的生产模式。     

毛乌素沙地人工固沙灌木林凋落物分解及改良土壤的研究

通过对毛乌素沙地沙柳、柠条、杨柴三种灌木林地凋落物的数量、分解速度、土壤养分积累、土壤物理性质等的测定,探讨了人工固沙灌木林改良土壤的过程。研究结果表明:树种不同,凋落物生物量存在着较大的差异,其中沙柳最多,其次为杨柴,柠条最少;凋落物的分解受树种和环境因素两方面的影响,各处理失重率表现为埋置处理地表淋溶地表无淋溶,相同处理下柠条失重率显著高于杨柴,杨柴显著高于沙柳;沙柳、杨柴、柠条灌木林地均显著增加了土壤有机质、全氮、全磷含量,且增加主要表现在0~25 cm土层;灌木林较流动沙丘显著降低了土壤容重,增加了土壤孔隙度。毛乌素沙地人工固沙灌木林地通过凋落物的产生及分解,使土壤有机质、全氮、全磷养分含量不断提高、土壤容重降低、孔隙度增大、促进了土壤的改良。     

马尾松人工林密度与枯枝落叶量的关系

对14年生马尾松人工林生态系统4个密度林分的枯枝落叶量及养分含量测定表明,林分枯枝落叶的年凋落物量和林地上枯枝落叶层的总贮量均随林分密度增大而增加。在枯枝落叶层中已经分解的物质量及其养分释放量,以密度为3210株/公顷的松林最高。     

海岸带3种林分类型凋落物-土壤-酶活性动态变化

为明晰南亚热带滨海沙地不同林分类型凋落物-土壤-酶活性的特征及其相关关系,揭示滨海森林生态系统养分迁移规律,以高山榕、红鳞蒲桃为优势种的两种典型次生林(高山榕林和红鳞蒲桃林)及马占相思人工林(马占相思林)为研究对象,分析3种林分类型的凋落物分解、土壤养分和土壤酶活性的动态变化规律及其相关关系。结果表明:凋落物分解速率表现为高山榕林>红鳞蒲桃林>马占相思林。土壤养分含量均表现为高山榕林或红鳞蒲桃林最高,马占相思林最低。3种林分类型的同一土壤酶活性的动态变化规律基本一致,最大值出现在8或11月。3种林分类型凋落物损失量与土壤养分及土壤酶活性的相关性存在一定差异。高山榕林和红鳞蒲桃林的土壤蔗糖酶(SUC)活性与全氮(TN)含量分别呈极显著(P<0.01)和显著(P<0.05)正相关;马占相思林的土壤过氧化氢酶(CAT)活性与碱解氮(AN)、全磷(TP)含量分别呈极显著(P<0.01)和显著(P<0.05)正相关。高山榕林和红鳞蒲桃林两种次生林的凋落物分解速率、土壤养分含量及土壤酶活性均显著优于马占相思人工林,因此在滨海地力的恢复和维持过程中,应优先保护天然...     

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。     

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.     

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.