集约经营毛竹林土壤活性有机碳库研究

为了解毛竹林集约经营后土壤有机碳库发生的变化,采集了集约经营历史5～10年竹林的土壤样品进行分析,并与粗放经营毛竹林进行比较。研究结果表明:毛竹林集约经营后土壤总有机碳、水溶性有机碳和微生物量碳含量都明显减少,与粗放经营毛竹林之间有显著差异(P<0.05),并且微生物量碳占总有机碳比例也显著降低,水溶性有机物质的分子量也明显变小。集约经营后竹林土壤矿化态碳数量及其占总有机碳比例增强,说明毛竹集约经营使土壤有机物质稳定性变差,矿化率增加。毛竹林土壤总有机碳、水溶性碳、微生物量碳及矿化态碳两两之间相关性均达极显著水平(P<0.01),土壤各类有机碳含量与土壤全氮、水解氮含量间相关性也达显著或极显著水平。毛竹集约经营未改变各类有机碳的剖面变化特征。     

不同类型人工毛竹林土壤碳氮含量及转化特征

对浙江省建德市集约经营、杉-竹混交和一般经营3种人工经营类型毛竹林土壤0-80 cm剖面碳氮含量及转化速率进行测定和分析.结果表明:3种竹林土壤碳氮含量及转化特征存在显著差异.3种类型竹林土壤有机碳含量都随土壤深度增加而下降,一般经营毛竹林土壤有机碳含量显著高于集约经营竹林与杉-竹混交林;3种竹林土壤呼吸速率则表现为一般经营＞集约经营＞杉-竹混交林,但不同竹林剖面变化趋势不同;毛竹纯林土壤呼吸速率与有机碳含量呈显著正相关,表现为随土层增加逐渐下降,而混交林土壤表层0-10 cm呼吸速率最高,随后在10-20 cm显著下降,随后在20-60 cm又逐渐增高,表明混交林根系呼吸在土壤总呼吸中贡献率较高.3种竹林土壤剖面全氮含量差异不大,集约经营竹林氮素投入对当前氮素总量没产生较大影响,但导致土壤氮素组分发生变化.杉-竹混交林无机氮含量最低,土壤硝化速率也显著低于毛竹纯林,表明混交林土壤氮素周转率,具有较好的氮素利用效率;集约经营竹林土壤硝化速率与一般经营竹林差异不大,但存在氮素的反硝化损失风险.     

长期集约经营对雷竹林土壤碳氮磷库特征的影响

为了研究长期集约经营对雷竹林土壤碳库与养分库的影响,在浙江省临安市三口镇选择了两块相邻的集约经营雷竹林样地（经营时间分别为1a和15a）采样,分析测定了土壤不同形态碳、氮和磷,并利用核磁共振方法分析了土壤总有机碳的波谱特征。结果表明：与集约经营1a雷竹林比较,15a集约经营雷竹林土壤总有机碳、水溶性有机碳、热水溶性有机碳和易氧化碳含量分别增加了249%、197%、81.8%和116%,但微生物生物量碳含量下降了17.6%。土壤有机碳的固态核磁共振结果表明,雷竹林土壤有机碳以烷基碳和烷氧碳为主。与1a集约经营的比较,15a集约经营后,土壤烷基碳和烷基碳/烷氧碳比（A/O-A）显著增加（p < 0.05）、芳香碳和芳香度显著下降（p < 0.05）,而烷氧碳和羧基碳没有显著变化。与集约经营1a雷竹林比较,15a集约经营雷竹林土壤水溶性有机氮、NH4 -N、NO3--N、有效磷和有机磷含量显著增加（p < 0.05）,但微生物生物量氮和微生物生物量磷含量分别下降了36.5%和22.7%。综上所述,长期集约经营导致雷竹林土壤碳库和氮磷养分库的贮量显著增加,而土壤微生物活性和土壤有机碳库的稳定性却显著下降。     

毛竹林地土壤团聚体稳定性及其对碳贮量影响研究

通过对集约经营毛竹林地土壤团聚体的测定,结果表明毛竹林地3个土壤层次各粒径团聚体分布特征为>5 mm的含量在土壤团粒结构中占主导地位,占总团聚体的比例为26.39%~42.38%;其次为1~5 mm含量,占14%~18%;<0.25 mm的含量最小,占2.31%~6.73%。毛竹林土壤团聚体平均重量直径平均值为0.90 mm,并且随着土壤层次的增加有逐渐增加的趋势。毛竹林地土壤总有机碳的积累与0.25~3.15 mm土壤团聚体中有机碳含量呈显著相关,与>3.15 mm和<0.25 mm团聚体有机碳含量相关不显著。毛竹林地0~20 cm土壤层中,分布在>5 mm和3.15~5 mm粒径土壤团聚体中的有机碳比例分别为14.86%和11.26%,低于20~40 cm和40~60 cm土壤。这也说明,长期集约经营毛竹林后,林地土壤有机碳含量下降的主要原因可能是>5 mm粒径土壤团聚体有机碳含量下降。     

不同森林植被下土壤水溶性有机碳研究

在我国亚热带采集了常绿阔叶林、马尾松林、杉木林和毛竹林土壤,分析了土壤总有机碳和水溶性有机碳含量。结果表明:土壤总有机碳含量常绿阔叶林和毛竹林显著高于杉木林和马尾松林。土壤水溶性有机碳含量毛竹林显著高于杉木林,极显著高于马尾松林,阔叶林和杉木林也显著高于马尾松林。水溶性有机碳占总有机碳比率以杉木林最高,达1 26%(25℃)和1 82%(100℃),马尾松林最低,仅0 78%(25℃)和1 30%(100℃)。马尾松林、杉木林和毛竹林土壤水溶性有机碳与土壤总有机碳含量间的相关性均达显著水平,相关系数分别为0 5106 (100℃提取),0 4739 (25℃提取)和0 4752 (25℃提取)。     

毛竹林土壤有机碳及微生物量碳特征研究

通过对湖南会同林区集约经营毛竹林地土壤有机碳和微生物量碳进行测定,结果表明,毛竹林地土壤(0-60 cm)有机碳和微生物量碳含量平均值分别为1.727%和551.84 mg/kg,不同土壤层次有机碳和微生物量碳含量差异极显著,其中,0-20 cm土层有机碳含量平均值为2.607%,分别是20-40 cm和40-60 cm土层有机碳含量的1.67倍和2.57倍;0-20 cm土层的微生物量碳占土壤总微生物量碳的58.9%,分别是20-40 cm和40-60 cm土层的2.69倍和3.08倍。不同季节间土壤微生物量碳有明显变化规律,即土壤微生物量碳含量1-7月份呈上升的趋势,7月达到最大值,8-12月份呈逐渐下降趋势;不同季节间有机碳含量差异不显著。毛竹林地土壤表层土壤微生物量熵为1.118 6%,与40-60 cm土壤层相当,略高于20-40 cm土壤层,说明毛竹林不同土壤层次有机碳积累强度相当。     

杭州湾南岸不同围垦年限农田土壤有机碳及其活性组分变化

采集杭州湾南岸围垦农田土壤样品(0-10,10-20,20-30,30-40,40-50cm),分析不同围垦时期(10,40,60,120a以上)农田土壤有机碳、水溶性有机碳、易氧化碳和轻组有机质的变化特征。结果表明:各有机碳活性组分变化规律总体上与土壤有机碳相近但亦有不同之处。随围垦时间增加,土壤有机碳及其活性组分呈增加趋势,但围垦40a以上,其含量均趋于相对稳定水平;其中0-10cm土层,土壤有机碳、水溶性有机碳、易氧化碳和轻组有机质含量增幅依次为40.43%,14.23%,25.47%,13.68%。土壤有机碳及其活性组分含量主要分布在0-20cm土层,但水溶性有机碳略有差别。水溶性有机碳分配比例随围垦年限增加而减小,易氧化碳则相反。土壤有机碳与其活性组分之间均显著正相关,各组分与土壤全氮、土壤含水量呈显著正相关。综上表明,随围垦年限延长土壤有机碳含量增加但其稳定性有所下降,有机碳活性组分能够敏感地反映土壤有机碳动态特征。     

岷江上游干旱河谷区灌丛植被土壤有机碳稳定性特征

灌丛在岷江上游分布广泛,是干旱河谷区重要的物种,砍伐、开垦和过度放牧是导致其退化的根本驱动力。通过选取灌丛植被下土壤剖面,并以其被开垦后的农地（50a）及退耕荒坡（10a）为参照,对其土壤有机碳、重组有机碳及易氧化碳含量进行分析比较。结果表明：灌丛植被各层土壤总有机碳及重组有机碳均极显著大于对照的,对照间差异不显著,在0-100cm土壤剖面,对照1退耕荒坡及对照2农地土壤有机碳较灌丛植被的最高降幅分别达60.42%,70.92%,重组有机碳最高降幅则分别达76.54%,68.92%,并且灌丛及对照2农地土壤重组碳在0-100cm土层剖面上表现出先升高,然后再降低的分布特征,对照1退耕荒坡则在整个土壤剖面呈递减趋势;灌丛植被土壤易氧化碳均值高于对照的,与退耕荒坡的差异显著,但与农地的差异不显著,在0-100cm土层中,灌丛及对照土壤易氧化碳含量表现出先降低、升高、再降低的分布特征;相关分析表明,总有机碳与重组有机碳和易氧化碳达到极显著相关水平。综上表明灌丛植被保护土壤有机碳稳定能力极显著高于退耕荒坡和农地的,并且农地退耕也有利于土壤有机碳稳定性的提高。     

不同经营强度下毛竹丛枝菌根共生体对氨氧化微生物的影响

利用原位微宇宙试验将丛枝菌根(Arbuscular mycorrhiza,AM)真菌菌丝与根系区分,设置菌根室(RA)和菌丝室(AH)两个分室处理,以粗放经营(extensive management,EM)毛竹林为对照,研究集约经营(Intensive management,IM)条件下毛竹林土壤丛枝菌根共生体对氨氧化微生物群落的影响及其响应机理。结果表明,无论集约经营还是粗放经营AH处理土壤pH均显著降低,且集约经营毛竹林AH处理土壤碱解氮显著降低;不同分室处理对硝化势没有显著影响,但集约经营毛竹林RA处理土壤硝化势显著高于粗放经营;集约经营之后氨氧化古菌(Ammonia-oxidizing archaea,AOA)基因丰度显著降低,而氨氧化细菌(Ammonia-oxidizing bacteria,AOB)基因丰度则在两种经营强度的AH处理中显著降低。不同经营强度和分室处理并未对氨氧化微生物群落组成结构产生显著影响,但网络分析显示集约经营毛竹林氨氧化微生物之间的互作和共生关系优于粗放经营,粗放经营毛竹林氨氧化微生物之间的竞争更为激烈。研究结果为更好地理解毛竹林AM真菌与氨氧化微生物之间的互作关系提供了理论基础。     

缙云山5种植被下土壤活性有机碳及碳库变化特征

为揭示重庆市缙云山不同植被下土壤活性有机碳及碳库分配特征，以该地区5种植被类型：阔叶林、针叶林、混交林、竹林和荒草地为研究对象，分析不同植被类型下各土壤层次中有机碳（Soil organic carbon, SOC）、微生物量碳(Microbial biomass carbon，MBC)、可溶性有机碳(Dissolved organic carbon，DOC)、易氧化有机碳(Readily oxidized organic carbon，ROC)含量及其土壤碳库的变化特征。结果表明：土壤有机碳和各活性有机碳组分含量及分配比例受到植被类型和土层深度的明显影响。土壤有机碳的平均含量在0~100 cm土层表现为竹林（16.74 g/kg）>阔叶林（12.62 g/kg）>草地(11.14 g/kg)>混交林（8.16 g/kg）>针叶林（5.98 g/kg），并随土层深度的增加而减小。竹林和阔叶林的微生物量碳和易氧化有机碳含量均明显高于混交林和针叶林，各植被在剖面上均表现出垂直递减规律，表现出明显的表聚效应。除草地，4种植被的土壤碳库管理指数随土层深度的加深而减小，均表现为表层(0~20 cm土层)最高。不同植被类型间，竹林的可溶性有机碳分配比例在各土壤层次均最小，整个土壤剖面均值仅为0.1%。由相关性分析可知，微生物量碳、易氧化有机碳、土壤总有机碳含量和土壤有机碳储量有着极其显著的相关性。因此，土壤微生物量碳和易氧化有机碳可以作为衡量亚缙云山森林不同植被土壤有机碳库变化的敏感性指标。     

不同经营措施对毛竹林土壤有机碳含量及季节动态的影响

Soil samples for conventional management （CM） and intensive management （IM） practices were taken over a year at 2-month intervals to determine the effect of management practices on soil organic carbon （SOC） and to quantify seasonal dynamics in SOC for bamboo （Phyllostachys pubescens Mazel ex H. de Lehaie） stands. The results with IM compared to CM showed large decreases in total organic carbon （TOC）, microbial biomass carbon （MBC）, water-soluble organic carbon （WSOC）, and the MBC/TOC ratio in the soils. With all IM plots in the 0-20 cm depth across sampling periods, average decreases compared with CM were： TOC, 12.1%; MBC, 26.1%; WSOC, 29.3%; the MBC/TOC ratio, 16.1%; and the WSOC/TOC ratio, 20.0%. Due to seasonal changes of climate, seasonal variations were observed in MBC and WSOC. Soil MBC in the 0-20 cm depth in September compared to May were 122.9% greater for CM and 57.6% greater for IM. However, due primarily to soil temperature, soil MBC was higher during the July to November period, whereas because of soil moisture, WSOC was lower in July and January. This study revealed that intensive management in bamboo plantations depleted the soil C pool; therefore, soil quality with IM should be improved through application of organic manures.     

不同土地利用类型对伊犁地区土壤活性有机碳库和碳库管理指数的影响

土壤碳库管理指数（CPMI）可以比较准确地发现人为因素对土地利用的干扰情况。以伊犁河谷不同土地利用类型（耕地、林地、草地和荒地）为研究对象,分析了不同土地利用类型土壤有机碳（SOC）含量、活性有机碳含量及其在SOC中的分配情况,各类有机碳含量之间的相关性、CPMI。研究表明:（1）不同土地利用类型SOC含量和水溶性有机碳（WSOC）含量有显著差异,SOC含量为草地 > 林地 > 耕地 > 荒地;WSOC含量为耕地（最高） > 荒地（最低）;易氧化碳（ROC）含量为草地最低;在0—20 cm和20—40 cm土层,微生物量碳（MBC）含量为草地（最高） > 林地（最低）;ROC含量为荒地高于草地。不同土地利用类型SOC含量均随土层深度增加而降低;ROC含量均随土层深度增加而升高;除林地外,其他样地MBC含量均随土层深度增加呈先升高后降低趋势,而WSOC含量均随土层深度增加而逐渐降低。（2）不同土地利用类型下ROC,MBC和WSOC所占SOC比例各不相同,且碳库的活度主要取决于ROC所占比例,ROC所占比例为荒地 > 耕地 > 林地 > 草地;MBC所占比例为荒地 > 耕地 > 草地 > 林地;WSOC所占比例为耕地 > 林地 > 荒地 > 草地。同一土地利用类型各活性有机碳所占比例情况为ROC > MBC > WSOC。（3）不考虑土层深度影响,耕地ROC含量与MBC含量呈极显著线性负相关;林地SOC含量与ROC含量呈显著线性负相关;荒地SOC含量与WSOC含量呈极显著线性正相关。不同土地利用类型下SOC,ROC,MBC,WSOC含量之间线性相关程度总体偏低。（4）同一土地利用类型,CPMI均随土层深度的加深先增大后减小;0—20 cm土层的CPMI为林地 > 荒地（100） > 耕地 > 草地。土地利用类型由荒地、草地、耕地转变为林地,有利于CPMI的提高,有利于土壤培肥,促进碳循环。     

Moso bamboo expansion into a broadleaved forest alters the dominant soil organic carbon source

Both microbes and plants contribute to soil organic carbon (SOC) formation and retention, but their roles in controlling SOC dynamics in forest soils under Moso bamboo (Phyllostachys edulis) expansion remain unclear. Here, amino sugars and lignin monomers were measured to represent microbial necromass and plant-derived components, respectively. The observed decline in both amino sugars and lignin monomers during Moso bamboo expansion indicates a reduction in microbial necromass and recalcitrant plant contributions to SOC composition. This could be attributed to a limitation of microbial substrates and proliferation caused by the reduced litter inputs resulting from the expansion. The proportion of microbial necromass contributing to the SOC pool increased, but that of lignin monomers decreased, as SOC content decreased with Moso bamboo expansion. This suggests that the decrease of SOC during bamboo expansion was mainly due to the reduction of lignin, while the increased contribution of microbial-derived carbon to SOC may serve to improve SOC stability. Our study sheds light on the altered SOC source inputs resulting from Moso bamboo expansion and emphasizes the need for sustainable forestry management practices that differentiate between microbial- and plant-derived carbon pools.     

The carbon storage in moso bamboo plantation and its spatial variation in Anji County of southeastern China

Purpose

Forest ecosystems play an important role in sequestering carbon in their biomass and soils. Moso bamboo plantations, as a special forest type, are mainly distributed in southern China. There is little information about the carbon storage in moso bamboo plantations, it is now important to better understand the moso bamboo’s carbon sequestration. The main objectives of this study were to investigate the spatial variation of aboveground biomass carbon (AGC) and soil organic carbon (SOC) in moso bamboo plantations and to compare carbon storage in moso bamboo plantations under different management options.

Materials and methods

A total of 73 moso bamboo plots were selected in Anji County, which is a famous “bamboo town” in northwest Zhejiang province, China. The diameter at breast height and the age of each moso bamboo in the selected plots were measured in order to calculate the AGC. SOC was analyzed using sulfuric acid–potassium dichromate solution. One-way ANOVA was applied to analyze the significant difference of AGC and SOC under different management options. Geostatistics and geographical information were used to study the spatial dependence characteristics of AGC and SOC.

Results and discussion

The AGC values were very variable, ranging from 9.92 to 38.70 Mg?ha^?1, with an average of 20.85 Mg?ha^?1. The SOC values were from 34.8 to 176.17 Mg?ha^?1. Both the AGC and SOC values were followed normal distributions. Moso bamboo plantations contributed about 16.5 % of total forest biomass carbon in Zhejiang Province, indicating its important influence on regional carbon budget. Geostatistical analysis revealed that the AGC had moderate spatial autocorrelation. A nested model (a spherical model with a Gaussian model) was chosen to describe the variogram. Spatial patterns for AGC were found in Anji County, with relatively high AGC values were found in the southwestern part of Anji County, and low values were located in the eastern and central parts of the county. While no clear spatial autocorrelation trend was observed in the semivariogram of SOC, indicating a random distribution pattern for SOC in the study area. Meanwhile, the Pearson’s correlation between AGC and SOC in bamboo plantation was weak (r?=?0.064, p?=?0.496), due to moso bamboo’s special growth process and different management options by human beings.

Conclusions

In this study, moderate spatial dependency was found for AGC, while the spatial autocorrelation of SOC was poor. In moso bamboo forest ecosystem, SOC was mainly stored at the top 40 cm layer. Management options were proved to be an important factor for carbon sequestration. Extensive management is an efficient way to increase carbon stock, compared to moderate and intensive management. With the rapid increase of plantation area, moso bamboo ecosystem will continue to play an important role in regional carbon budget.     

长期施肥下黑土活性有机碳变化特征

观测分析了黑土长期不同施肥30年后不同形态的活性有机碳含量(易氧化有机碳>轻组有机碳>微生物量碳>水溶性有机碳)的变化特征。结果表明,长期施用氮、氮磷和氮磷钾化肥对土壤活性有机碳无显著影响;长期施用有机肥以及有机肥配施化肥均显著提高了土壤活性有机碳含量,与不施有机肥相比,有机肥区组中土壤轻组有机碳和水溶性有机碳含量增幅较大,分别在122%～258%和237%～351%之间,而土壤易氧化有机碳和微生物量碳含量增幅分别在72%～98%和83%～112%。黑土不同形态活性有机碳对施肥的响应灵敏度为,轻组有机碳>水溶性有机碳>微生物量碳≈易氧化有机碳。因此,轻组有机碳是指示土壤有机碳变化的较好指标。     

阔叶林改种毛竹(Phyllostachys pubescens)后土壤固氮细菌 nifH 基因多样性的变化

【目的】毛竹是喜氮植物,土壤氮素水平对毛竹生长至关重要。生物固氮是土壤氮素的重要来源,因此,探索阔叶林改种毛竹后土壤固氮细菌和土壤氮素的变化具有重要意义。【方法】选择立地条件相近的毛竹林(100多年前由阔叶林改种而来)和阔叶林,每种林地在东北坡向位置随机选择4个10 m×10 m标准样地,每个标准样地选取5个采样点,分层采集0—20 cm(表层)和20—40 cm(次表层)土壤样品,分析了土壤pH、有机碳、碱解氮、有效磷、速效钾和含水量等常规理化性质; 采用引物对AQER和PolF,以土壤总DNA为模板扩增了固氮细菌功能基因(nifH )片段,应用变性梯度凝胶电泳(DGGE)和实时荧光定量PCR(Real-time PCR),分析了固氮细菌群落结构、多样性以及丰度(nifH 基因拷贝数)变化; 通过基因克隆测序对土壤固氮细菌进行初步鉴定。【结果】阔叶林改种毛竹后土壤pH显著(P0.05)提高; 毛竹林土壤的含水量、碱解氮以及表层土壤的速效钾显著高于(P0.05)同层的阔叶林土壤,而有效磷则显著(P0.05)低于同层的阔叶林土壤。总体来说,阔叶林改种毛竹后土壤养分含量明显提高; 阔叶林土壤固氮细菌DGGE条带数以及多样性指数(Shannon-Wiener index)都高于毛竹林; 基于DGGE条带信息的聚类分析和主成分分析(PCA)结果表明,阔叶林和毛竹林区分为2个类群,而同一林分的不同土层之间差异较小; 实时荧光定量PCR结果显示,毛竹林土壤的固氮细菌 nifH 基因丰度显著(P0.05)高于阔叶林土壤; 通过克隆测序,14个阳性克隆分别属于2个不同的菌属,其中13个均为Bradyrhizobium,1个为Azohydromonas lata,条带序列与已知序列的相似度为93%~98%。【结论】阔叶林改种毛竹后土壤固氮细菌的种类减少,而功能基因丰度却明显增加; 土壤氮素水平明显提高,这可能是土壤固氮能力增强的结果。     

Effects of Inorganic and Organic Fertilizers on Soil CO2 Efflux and Labile Organic Carbon Pools in an Intensively Managed Moso Bamboo (Phyllostachys pubescens) Plantation in Subtropical China

Impact of combined application of inorganic and organic fertilizers on soil carbon dioxide (CO₂) emission is poorly understood. We investigated the effects of inorganic fertilizer (IF), organic fertilizer (OF), and a mixture of organic and inorganic fertilizers (OIF) applications on the dynamics of soil CO₂ efflux in intensively managed Moso bamboo plantations. Soil CO₂ efflux and concentrations of water soluble organic C (WSOC) and microbial biomass C (MBC) in the IF treatment were higher than those in the control but lower than those in the OF and OIF treatments. Both OF and OIF treatments increased the SOC stock. Strong exponential relationships (p < 0.01) between soil temperature and CO₂ efflux were observed in all treatments. Soil CO₂ efflux in all four treatments was correlated with WSOC (p < 0.05) but not with MBC. We concluded the combined approach can possibly contribute to increasing the level of SOC stock in intensively managed plantations.