四种人工林枯落物持水特性

为了解木荷等4种人工林的枯落物水文特性,在广东省佛山市云勇林场,以木荷、杉木、藜蒴和火力楠人工林为研究对象,通过枯落物储存量调查和浸泡实验,分析枯落物持水特性,建立了枯落物持水量、吸水速率与浸泡时间的相互关系。结果表明：4种人工林林分枯落物总储存量介于2．82～10．92t／hm2,杉木林最大（10．92t／hm2）,火力楠林最小（2．82t／hm2）;最大持水量依次为：杉木林〉藜蒴林〉木荷林〉火力楠林;最大拦蓄量介于4．16—12．93t／hm2;有效拦蓄量介于2．46～8．92t／hm2,依次是杉木林〉藜蒴林〉火力楠林〉木荷林。枯落物浸泡实验表明：枯落物持水量与浸泡时间存在对数曲线关系,而吸水速率与浸泡时间则是幂函数关系。4种人工林枯落物持水率和吸水速率随时间的动态变化规律基本相似。随浸泡时间的延长,枯落物持水率呈增加趋势,在浸泡10—12h后,持水率增幅趋于平缓;枯落物吸水速率在前2h内变化最快,之后逐渐变缓,24h时吸水基本停止。     

施氮方式和灌水量对甘蔗农艺性状、 养分累积及产量的影响

[目的]探讨不同施氮方式和灌水量对甘蔗生长、养分累积及产量的影响,为合理利用水肥资源实现甘蔗高产高效栽培提供参考依据.[方法]以新台糖22号(ROC22)为试验材料,设不施氮肥、不灌水(CK),氮肥作基肥一次性施用、灌水750 mm(T1),氮肥作基施一次性施用、灌水1000 mm(T2),氮肥作基施一次性施用、灌水1250 mm(T3),氮肥分3次施用(基肥30%、分蘖肥30%、攻茎肥40%)、灌水750 mm(T4),氮肥分3次施用、灌水1000 mm(T5)和氮肥分3次施用、灌水1250 mm(T6)7个处理,测定各处理甘蔗农艺性状、各部位养分含量、产量和蔗汁锤度等指标,研究不同施氮方式和灌水量对甘蔗生长与产量的影响.[结果]中、高灌水量(1000和1250 mm,下同)时,分3次施氮处理甘蔗的株高高于一次性施氮处理,在5~7月差异显著(P<0.05).在甘蔗成熟期,茎干重表现为T1>T2>T3、T6>T4>T5、T1>T4、T2>T5和T3T4、T2>T5和T3T2>T3、T6>T4>T5、T1>T4、T2>T5和T3T1>T2、T4>T6>T5、T1相似文献   

广西喀斯特次生林地表碳库和养分库特征及季节动态

以自然保护区原生林为对照,调查了广西喀斯特区处于同一次生演替序列中的灌丛、藤刺灌丛、乔灌丛3个群落的地表凋落物存量,同时对凋落物层和土壤表层(0-5 cm)的有机碳,全氮、磷、钾等养分元素的含量、贮量状态及其雨季前后的变化进行了研究.结果表明:地表凋落物存量及有机碳、全氮贮量随演替阶段上升均呈增高趋势;除全磷外,土壤的有机碳和养分元素含量与凋落物层贮量相关性显著(p<0.05);雨季期间,凋落物迅速分解,地表凋落物的分解量要大于当季凋落量,并且次生林的凋落物分解与养分释放量显著高于原生林;雨季后,各群落有机碳和养分的凋落物层贮量以及土壤含量均有所降低.其中凋落物层贮量下降显著的是藤刺灌丛与乔灌丛.土壤养分含量则在灌丛与原生林阶段下降更为明显.在从灌丛向顶级群落演替的进程中,森林的自养能力可能存在一个先增高再降低的过程.     

森林凋落物分解研究进展

 森林凋落物分解是森林生态系统养分生物循环的重要环节,而分解过程中所释放的CO2是全球碳素收支的重要组分,开展森林凋落物分解研究是充分认识森林生态系统结构和功能的基础。研究认为:凋落物分解的预测指标可分为3类,即环境指标(如实际蒸散量)、凋落物物理质量(如叶抗张强度)和化学质量指标(如C/N比、木质素/N比和C/P比等);凋落物分解过程中养分释放机制极其复杂,养分动态模式主要有淋溶—释放、淋溶—富集—释放和富集—释放3种,并因凋落物种类、分解阶段和元素本身性质的不同而异;凋落物混合分解并非单一树种分解的简单叠加,因树种组成和比例不同,基质的化学组成会发生变化,从而影响分解者的多样性、丰富度和生理活性,进而直接和间接地影响其分解速率;凋落物混合分解中可能存在无效应、促进效应和抑制效应;现有的研究结果显示,凋落物混合分解的适宜比例应与群落中不同树种的种群比例相一致;CO2浓度升高不仅影响凋落物的化学性质,而且与分解环境中土壤的生物活性密切相关,但CO2浓度升高并不改变凋落物质量与分解速率之间的关系;越来越多的研究显示,CO2浓度升高的环境下,植物群落的物种组成会产生变化,这种变化对养分循环速率的影响远大于单纯大气CO2浓度变化的影响。     

大兴安岭北方森林凋落物真菌及其抗菌化合物

为了研究大兴安岭森林凋落物真菌的抗菌活性,首先利用颗粒涂布平板法分离真菌,通过扩增与比对内部转录间隔区序列初步鉴定分离到的真菌.采用双平板打孔药剂扩散法检测抗菌活性,使用层析法分离目标菌株单体化合物.通过波谱学分析确定其化学结构,使用96孔板液体稀释法检测单体化合物的最低抑菌浓度.共分离得到88株真菌,其隶属于57个属...     

Conversion of a tropical forest into agroforest alters the fine root-related carbon flux to the soil

Large areas of remaining tropical forests are affected by anthropogenic disturbances of various intensities. These disturbances alter the structure of the forest ecosystem and consequently its carbon budget. We analysed the role of fine root dynamics in the soil carbon budget of tropical moist forests in South-east Asia along a gradient of increasing disturbance intensity. Fine root production, fine root turnover, and the associated carbon fluxes from the fine root system to the soil were estimated with three different approaches in five stands ranging from an old growth forest with negligible anthropogenic disturbance to a cacao agroforestry system with planted shade trees. Annual fine root production and mortality in three natural forest sites with increasing canopy openness decreased continuously with increasing forest disturbance, with a reduction of more than 45% between the undisturbed forest and the forest with large timber extraction. Cacao agroforestry stands had higher fine root production and mortality rates than forest with large timber extraction but less than undisturbed forest. The amount of carbon annually transferred to the soil carbon pool through fine root mortality was highest in the undisturbed forest and generally decreased with increasing forest use intensity. However, root-related C flux was also relatively high in the plantation with planted shading trees. In contrast, the relative importance of C transfer from root death in the total above- and below-ground C input to the soil increased with increasing forest use intensity and was even similar to the C input via leaf litter fall in the more intensively managed agroforest. We conclude that moderate to heavy disturbance in South-east Asian tropical moist forests has a profound impact on fine root turnover and the related carbon transfer to the soil.     

遮荫下2种热带树苗叶片光合特性和抗氧化酶系统对自然降温的响应

选取 2种遮荫条件下 (8%、2 5 %全光照 )西双版纳地区热带雨林上层树种滇南红厚壳和中层树种玉蕊的幼苗 ,测定了雨季末自然降温过程中 2种植物叶片光合特性、抗氧化酶 (SOD、CAT、APX)活性、丙二醛 (MDA)含量的变化。研究结果表明 :低温使 2种植物单位面积叶绿素含量和净光合速率明显下降 ,生长在中等光强下的幼苗比低光强下的幼苗下降的比率大 ,滇南红厚壳比玉蕊下降的比率大。在降温初期 ,即从 10月到 12月初 ,2种光强下 2种植物SOD和APX活性上升 ,CAT活性出现波动 ,黎明光化学效率和MDA含量基本没有变化 ,光合机构没有受到氧化破坏。 12月末 ,中等光强下滇南红厚壳黎明光化学效率降低 ,SOD和APX活性有所下降 ,MDA含量显著上升 ;而低光强下的滇南红厚壳和 2种光强下玉蕊SOD和APX活性仍在上升 ,MDA含量变化较小。这表明 ,2种光强下 2种热带树苗是以不同的方式响应自然降温 ,低温对中等光强下的植物比低光强下的影响大 ,上层树种滇南红厚壳受到的影响比中层树种玉蕊大。同时 ,根据降温过程中抗氧化酶活性和MDA含量的变化 ,大致可将西双版纳热带雨林幼苗对低温的响应分为 2个阶段 ,即第 1阶段为低温适应阶段 ,抗氧化酶活性上升 ,光合机构没有受到明显的氧化破坏 ;第 2阶段 ,中等光强下滇南红厚壳抗氧化酶     

Variation in the chemical composition of green leaves and leaf litters from three deciduous tree species growing on different soil types

The chemical composition of green leaves and leaf litters of sweet chestnut (Castanea sativa), oak (Quercus robur) and beech (Fagus sylvatica) were determined for 26 sites grouped into high fertility (HF) and low fertility (LF) soils according to base saturation and N-mineralization potentials. Measurements were made of total carbon, acid detergent fibre (ADF), Klason lignin, holo-cellulose, sugar constituents of hemicellulose and phenylpropanoid derivatives of lignin, and nutrient concentrations (N, Ca, P, Mg, K and Mn). Leaf and litter constituents varied within and between species according to soil groups, but beech showed contrasting responses to oak and chestnut. Beech leaves had lower ADF, lignin and cellulose on HF soils than LF soils, whereas oak and chestnut leaves had higher ADF, lignin and cellulose on HF than the LF soils. Conversely, the same constituents in beech leaf litter were higher on HF soils than LF soils, but lower in oak and chestnut leaf litter on HF soils than LF soils. The phenylpropanoid derivatives of lignin and sugar constituents of hemicellulose also showed similar variations in relation to soil groups with contrasting patterns for in leaves and litters. Re-absorption of N from leaves before litter fall was negatively correlated with soil N mineralization potential for beech (highest on LF soils) but showed an unexpected, positive relationship for oak and chestnut (highest on HF soils). These intra-specific differences of leaf and litter chemistry in relation to soil fertility status are unprecedented and largely unexplained. The observed patterns reflect phenotypic responses to soil type that result in continuum of litter quality, within and between tree species, that have been shown in related studies to significantly influence litter decomposition rates.     

玉/豆和玉/薯模式下玉米氮素吸收利用差异及氮肥调控效应

研究西南地区玉米主要2种套作模式下氮素吸收利用差异及氮肥调控效应, 为氮素高效利用提供科学依据。在四川2个玉米主产区, 通过连续4年的大田试验, 对比研究了玉/豆和玉/薯模式下玉米氮素吸收利用差异和不同供氮水平对玉米氮素吸收的调控效应。结果表明, 玉/豆模式下玉米收获期植株中的氮素积累2个试验点平均较玉/薯模式增加7.11%, 氮收获指数增加2.00%左右, 氮素吸收效率增加7.83%, 成熟期籽粒中氮素的分配比例增加1.76%, 而叶、茎鞘中氮素的分配比例分别减少5.85%和2.75%。分带轮作后, 由于不同前茬对土壤养分影响不同, 再加上套作优势, 玉/豆模式下玉米在生长前期就表现出明显的优势, 到收获期植株氮素积累2个试验点平均较玉/薯增加11.85%, 氮素吸收效率增加11.84%。在玉米氮素积累关键时期, 玉/豆模式在低氮处理下玉米植株氮素的积累量显著高于玉/薯模式相同施氮处理, 而在高氮处理下2种模式间差异不大或者表现相反, 氮肥偏生产力、氮素农艺效率和氮肥利用率也有相似的结果; 玉/豆模式在180 kg hm^-2施氮量下较其他处理显著提高了玉米氮素农学利用率、氮素吸收利用率和籽粒中氮素的分配量, 玉/薯模式下玉米氮素农学利用率和氮肥利用效率, 在180~270 kg hm^-2施氮量处理下较高; 花后氮素同化量玉/豆模式显著高于玉/薯; 2种模式均以施纯氮180~270 kg hm^-2处理有利于氮素转运和花后氮素同化量积累。     

氮、磷、钾对油研10号油菜产量和品质的影响

采用三元二次通用正交旋转组合设计,研究了直播栽培方式下氮、磷、钾与油研10号油菜品种产量、产油量、含油率、芥酸、硫甙、饼粕蛋白质含量之间的关系.结果表明,在试验设计水平范围内,随着施氮量的增加,产量、产油量、芥酸呈逐渐降低趋势,含油率和饼粕蛋白质含量呈逐渐增加趋势.芥酸、含油率、饼粕蛋白质含量与施磷量间呈开口向上的抛物线关系,呈现出高-低-高的变化趋势.同时获得产量200kg·667m-2和产油量85kg·667m-2的优化农艺措施方案分别为纯氮6.46～7.59kg·667m-2、P2O5(磷肥)6.58～8.42kg·667m-2、K2O(钾肥)10.37～13.63kg·667m-2和纯氮9.06kg·667m-2、P2O5(磷肥)6.20～8.80kg·667m-2、K2O(钾肥)9.69～14.31kg·667m-2.