【作者】 文仕知；

【导师】 田大伦；

【作者基本信息】 中南林业科技大学 ， 生态学， 2010， 博士

【摘要】 本文研究了5年、8年、14年生桤木人工林生态系统的生物产量、碳贮量、养分积累与分布及水文学过程等生态功能,揭示桤木人工林生态系统的结构与功能过程,为研究森林生态系统对全球气候变化响应和反馈提供基础数据,为制定区域森林生态系统经营模式提供科学依据。研究结果如下：5年生、8年生和14年生桤木人工林乔木层生物量分别为51.23 t·hm2、73.05 t·hm2和95.31 t·hm2,地上生物量分别占林分总生物量的85.69%、82.36%和88.18%。树干、树枝的生物量随年龄的增大所占比例有所增加。各组分生物量的大小排序：树干>树冠>树根。林分的净生产力随年龄的增加而增加,分别为13.02、13.09和15.03t-hm-2·a-1。5年生桤木人工林根系总根长度变化趋势呈现出：细根>大根>粗根。根系比根长(SRL)变化为细根SRL>粗根SRL>大根SRL。桤木人上林大根RLD根长密度(RLD)沿沿水平方向上,大根呈递减趋势,粗根、细根RLD随着距树干距离的增大先减少再增加再减少的变化趋势；沿垂直方向上,大根和粗跟RLD在0-30cm内逐渐增加,随后开始逐步减小；细根随上层的加深而逐步减小。桤木根系分布良好的相范围为固相率38.5-54.5%,液相率21-36.5%,气相率12.5-35.5%,在此之外的根系牛长都呈现不良状态。桤木人工林生态系统生物量随年龄的增加而增加,5、8、14年生桤木生态系统生物量分别为54.65、76.50、103.23t-hm-2,活地被物生物量分别占系统总生物量的3.18%、1.71%和3.75%,林下死地被物层生物量分别占系统总牛物量的3.07%、2.91%和3.91%。桤木各器官的碳密度算术平均值随年龄的增长而增加,5年生、8年生和14年生的分别为0.4788、0.4857和0.4958 gC·g’,变异系数在0.25%-9.58%之间,不同器官C密度由高至低排序大致为：树干>树枝>树叶>树根>树皮,林下植被各组分和死地被物的碳密度随着林龄的变化规律不明显,土壤层(0-60 cm)平均碳密度也随着林龄的增长逐渐增加,且在垂直分布上随着土层深度的增加而逐渐下降。林木不同器官的碳贮量与其生物量成正比例关系,随着林龄增长,乔木层碳贮量的优势逐渐增强,从5年生的25.88 t·hm-2增加到14年牛的49.63 t-hm-2。桤木人工林生态系统碳库主要由植被层、死地被物层和土壤层组成,按其碳库大小顺序排列为：上壤层>植被层>死地被物层。5年生、8年生和14年生桤木林生态系统中的碳贮量分别为95.89、122.12和130.75 t·hm-2,土壤碳贮量占整个生态系统碳贮量的59.42%以上。随着林龄增长,地上部分与地下部分碳贮量之比有逐渐下降的趋势。5年生、8年生和14年生桤木年净固定碳量分别6.51、6.26和7.82 t·hm2·a1。湖南省现有桤木林植被层碳贮量为2.8034×106t,为其潜在C库的47.51%。桤木叶片中营养元素的含量相对较高,枝条中各营养元素的含量变化与叶基本一致;干材中N、P、K、Ca元索含量均在春季达到最低值；树皮中营养元素季节变化规律不明显。N的含量以叶片中最高,而Ca的含量则以树皮中最高,这与各器官的生理功能不同而密切相关。林下植被和枯落物与乔木层相比,养分含量相对较高；桤木叶中N、P、K浓度明显高于枯落物,而Ca则相反。5年、8年和14年生桤木林乔木层、活地被物层大量元素含量的排序均为：N>Ca>K>Mg>P。随着年龄的增加N的含量增加；而K的含量则随着年龄的增加而降低。林下活地被物层大量元素的含量排序依次为：8年生>14年生>5年生。死地被物大量元素养分含量的排序为：N>Ca>Mg>K>P。桤木林生态系统中土壤各层养分含量顺序均为：K>Mg>N>P>Ca,养分积累量为166046.23 kg·hm-2；乔木层养分积累量为754.77 kg·hm-2,各组分养分积累量排列顺序为：树叶>树枝>树干>树根>树皮；林下植被层的养分积累量为154.83 kg·hm-2,枯落物层的养分积累量为99.21 kg·hm-2,二者的养分积累量为254.04 kg·hm-2,占整个生态系统的0.15%。生态系统养分总积累量达167809.80 kg·hm-2,绝大部分由土壤层贡献所得。桤木每生产1t干物质,需要营养元素12.516 kg。四川桤木和台湾桤木林穿透雨量、林冠截留量和树干径流量与大气降雨量有显著关系,分别呈直线关系、指数函数关系和二次函数关系。四川桤木木人工林的穿透雨量、林冠截留量、树干径流量分别占大气降雨量的78.21%、16.51%、5.28%；台湾桤木人工林的穿透雨量、林冠截留量、树干径流量分别占大气降雨量的80.77%、15.03%、4.20%。四川桤木和台湾桤木人工林穿透水中养分元素含量排列顺序分别为：Ca>K>Mg>NH4+-N>NO3--N>Mn>Fe>Cu;Ca>K>NH4+-N>Mg>NO3--N>Fe>Mn>Cu。其中NH4+-N含量穿透水较林外降水降低了60%以上,且在穿透水和树干径流中含量呈现为先减后增,而K、Fe、Cu均呈增大趋势。四川桤木林降水过程以K元素增幅最大,从2.010mg·L-1增加至10.461mg·L-1。5年生四川桤木和台湾桤木的林冠截留率分别为：16.51%和15.03%,茎流率分别为5.28%和4.20%。四川桤木人工林有效持水量较高,为17.0t·hm-2,台湾桤木林为16.2t·hm-2。灌木草本层的持水速度与浸水时间呈指数函数关系变化,浸水时间越长,持水速度越小,在浸水3h后基本处于饱和状态。枯落物有效持水量排序为四川桤木人工林(1.70mm)>台湾桤木人工林(1.62mm)>宜林地(0.13mm)。桤木林地枯落物总量和未分解层枯落物储量随季节变化逐渐增加,半分解层枯落物随季节的变化基本呈现增加趋势。枯落物总量和未分解层储量均是四川桤木林>台湾桤木林,半分解层枯落物和枯落物层含水率均是台湾桤木林>四川桤木林,而未分解层枯落物含水率是四川桤木林最大。各层次枯落物含水率与土壤水分呈正相关关系。0-75cm土层范围内土壤水分随土层的加深其含量逐渐增大,土壤平均含水量排序为：四川桤木林(19.86%)>台湾桤木林(17.59%)>宜林地(17.18%)。30-75cm层土壤,各分层次含水量都是四川桤木林>台湾桤木林>宜林地。土壤含水量变异系数随土层加深逐渐减小。桤木林地30cm以下土壤含水量与降雨量相关性不显著；日平均气温对四川桤木林和台湾桤木林各层土壤含水量无显著(p>0.05)影响；日平均相对湿度对四川桤木林各层次土壤含水量影响不显著,对台湾桤木林0-75cm层有显著性正相关影响。更多还原

【Abstract】 In this paper, the stand biomass, carbon storage, accumulation and distribution of nutrient, hydrological processes and ecological function were investigated in the forest ecosystem of Alnus cremaslogyne at stand age 5,8 and 14 respectively, to study the structure and functional process of Alnus cremastogyne forest ecosystem. So as to reveal the response and feedback to global climate change of forest ecosystem, and to provide data bases and reference for formulating management mode of regional forest ecosystem in the world. The results showed as followings:The stratum biomass of Alnus cremaslogyne plantation with trees of 5-year-old, 8-year-old and 14-year-old were 51.23 t·hm-2,73.05 t·hm-2, and 95.31 t·hm-2 separately. The above ground biomass accounted for 85.69%,82.36% and 88.18% of the total biomass separately. The proportion of trunk, branches and leaves increased with the tree age increase. The biomass of each component was ranked as:trunk>crown>roots. The spatial distribution of root biomass changes was:big roots>middle root>small roots> fine roots. The net productivity of stand increased with tree age increase, the average annual net productivity were 13.02,13.09 and 15.03 t·hm-2·a-1 respectively。The total length of different specific roots of 5 year-old Alnus cremastogyne plantation planted in Miluo ordered as:fine root>large root>coarse root. The specific root length (SRL) to total root length was ranked as fine root SRL>coarse root SRL> large root SRL. Root length density (RLD) showed decrease trends along the vertical direction of the roots; along the horizontal direction, RLD of big root decreased with the increase of distance away from the trunk. Good distribution range of Alnus cremastogyne root in three-phase were solid fraction38.5-54.5%, liquid fraction21～36.5%, gas 12.5～35.5%, and roots would not grow well enough outside those ranges.The biomass of a whole plantation ecosystem of Alnus cremastogyne increased with the stand age, biomass of 5,8,14-year-old alder ecosystems were 54.65,76.50,103.23 t·hm-2 respectively, the living ground cover in the ecosystem accounted for 3.18%,1.71% and 3.75% respectively, dead ground cover accounted for 3.07%,2.91% and 3.91% of the entire ecosystem biomass respectively.The arithmetic average carbon density of different organs of alder was 0.4788 gC·g-1 for the 5-year-old plantation,0.4857 gC·g-1 for the 8-year-old stand and 0.4958 gC·g-1 for the 14 year-old plantation, which increased with the stand age, and the variation coefficient ranged form 0.25% to 9.58%. The carbon densities of different organs varied in the following order:stems> branches> leaves> roots> bark. The change of carbon densities in different groups of under-storey of plants or the duff layer was not evident as the forest age increased. The carbon density of soil layer between 0 and 60cm increased along with the stands age of Alnus cremastogyne and declined with the soil depth. The carbon storage in different oranges was positively related to the biomass of corresponding organs. Superiority of carbon storage in the trees gradually increased as the forest stands aged, carbon storage of the trees had grown up from 25.88 t-hm 2 for the 5-year-old to 49.63 t·hm-2 for the 14-year-old plantation. The carbon stock of Alnus cremastogyne plantation ecosystem was mainly consisted of three sections, that was the trees, the litter and the soil, and the order of whose carbon stock could be ranked as follow:the soil>the trees>the litter. Carbon stock of Alnus cremastogyne plantation was 95.89 t·hm-2 at 5-year-old,122.12 t·hm-2 at 8-year-old and 130.75 t·hm-2 at 14-year-old. Carbon storage in forestlands soil layer (0～60 cm) accounted for more than 59.42% of that in the whole ecosystem, the ratio of carbon storage of aboveground to that of underground deceased along with growing age of the Alnus cremastogyne forest. The annual carbon fixation of the 5-year-old, the 8-year-old and the 14-year-old Alnus cremastogyne plantation was respectively 6.51,6.26 and 7.82 t·hm 2·a 1. Extant carbon storage of Alnus cremastogyne plantation in Hunan province was up to 2.8034×106t, accounting for 47.51% of its potential carbon storage.Nutrient content of Alnus cremastogyne leaves was relatively high, same change of nutrient content was found in branch as that in leaf of Alnus cremastogyne. N, P, K, Ca element in the dry wood reached their lowest concentration in spring. Seasonal variation of nutrient in bark was not evident. The highest nutrient content in leaves was N, while that of Ca in the bark, which should be the consequence of different physiological functions of various organs.Floor vegetation had relatively higher nutrient content comparied with that in ground litter and tree layer. N, P, K concentration in Alnus cremastogyne leaves were significantly higher than that in the ground litter while Ca was contrary.The order of macro element concentration of the 5 years,8 years and 14 years old Alnus cremastogyne forest tree layer and living ground cover were:N>Ca>K>Mg>P. By the tree age increasing, concentration of N also increased; but concentration of K was decreased with age increase. The order of macro element concentration of living ground cover was 8-year-old>14-year-old>5-year-old. Order of macro element concentration of dead litter was:N>Ca>Mg>K>P.Nutrient concentration in soil layer of Alnus cremastogyne forest ecosystem ordered as:K>Mg>N>P>Ca, nutrient accumulation was166046.23 kg·hm-2; total elements accumulated were 754.77 kg·hm-2, the amount of nutrient accumulation of each component arranged in the following order:leaves> branch> trunk> root> bark. Nutrient accumulation of ground cover was 154.83 kg·hm-2, litter layer nutrient accumulated for 99.21 kg·hm-2, total amount was 254.04 kg·hm-2, accounted for the entire ecosystem of 0.15%. Alnus cremastogyne plantation accumulated an annual amounts of 167809.80 kg·hm-2 nutrient, most of it contributed by the soil layers.12.516 kg nutrient was needed to produce It dry matter for Alnus cremastogyne.Throughfall, canopy interception and trunk runoff of Sichuan alder and Taiwan alder had significant relationship with atmospheric rainfall; they were linear relationship, exponential relationship and quadratic relationship respectively. The redistribution of atmospheric precipitation input by throughfall, canopy interception and trunk runoff of Sichuan alder plantation accounting for 78.21%,16.51%,5.28% of atmospheric rainfall respectively; for Taiwan alder plantations the values were 80.77%,15.03%,4.20% respectively.Nutrient element concentrations of throughfall of Sichuan and Taiwan alder plantation ranked as:Ca>K>Mg>NH4+-N>NO3-N>Mn>Fe>Cu; Ca>K>NH4+-N>Mg >NO3-N>Fe>Mn>Cu, where NH4+-N concentration was reduced more than 60% in throughfall compared with that in the rainfall outside the forest, NH4+-N concentration in the throughfall and trunk runoff first decreased then increased. K, Fe, Cu of throughfall and trunk runoff increased in Sichuan and Taiwan alder forest. Elements K in Sichuan alder plantation has a maximal increase from 2.010mg·L-1 to 10.461 mg·L-1 during precipitation.Sichuan, and Taiwan alder’s canopy interception rates were 16.51% and 15.03% respectively, stem flow rate was 5.28% and 4.20% respectively. Alder plantation of Sichuan had higher effective water-holding capacity of 17.0 t·hm-2, while that of Taiwan alder plantation was smaller, which was 16.2 t·hm-2.Soak time and water retention time of shrub and herb layer had exponential relationship, the longer time the water soak, the smaller holding rate, saturation after 3h soak. Effective water-holding capacity of ground litter ordered as Sichuan alder plantation (1.70mm)>Taiwan alder plantation (1.62mm)> suitable afforestation land(0.13mm).Reservation of ground litter layer and non-decomposed layer of Alder forest increased with seasonal change, a gradual increase was found in semi-decomposed litter layer with seasonal change. Reservation amount of ground litter and non-decomposed layer were Sichuan alder plantation> Taiwan alder plantation, while moisture of semi-decomposed and ground litter layer was Taiwan alder>Sichuan alder, highest moisture content was found in non-decomposed litter layer of Sichuan alder. Ground litter biomass had a negative correlation with soil moisture; moisture content in all layers of ground litter and soil moisture were positively correlated.Moisture in 0-75cm soil layer increased with the increasing depth, the average water content were Sichuan alder (19.86%)>Taiwan alder (17.59%)>suitable afforestation land (17.18%). Within 30-75cm soil layer, regardless sub-levels, the water content of soil was always the Sichuan alder>Alnus alder>suitable afforestation land. Coefficient of variation of soil moisture gradually decreased with the soil depth.No significant correlation was found between rainfall and water content in the soil that deeper than 30cm below the ground; daily average temperature had no significant effect on soil moisture (p>0.05) in both Sichuan alder and Taiwan alder plantation; daily average relative humidity in Sichuan alder plantation has no significant effect on moisture content at all soil layers, however that had significant positive relationship with 0-75cm soil layer of Taiwan alder plantation.更多还原