不同年限毛竹-白及复合系统土壤微生物群落多样性特点

为了揭示毛竹-白及复合经营系统中植物-土壤间的互作关系,在安徽省广德市邱村镇选择3个不同套种年限(1、3和4年)的毛竹-白及复合林分为研究对象,采用Biolog-ECO微平板技术,结合主成分分析对培养72 h土壤微生物群落功能多样性及其碳代谢特征进行分析.结果 表明,毛竹-白及复合林分的土壤微生物碳源平均颜色变化率、S...     

Soil microbial functional diversity under intensively managed bamboo plantations in southern China

Background, aim, and scope

Bamboo (Phyllostachy pubescens Mazel ex Lehaie), a unique fast-growing tree species, is an important forest resource in southern China. Because of its high economic value and short rotation period, intensive management practices such as fertilization, weeding, and deep tilling are extensively utilized. These practices significantly increase the production of mature timber and young shoots. In this paper, bamboo stands under intensive management with short-term (STIP) and long-term (LTIP) practices were compared with those managed conventionally (CON) to study the effects of intensive management practices on soil biological properties.

Materials and methods

We measured the soil microbial biomass carbon (MBC), basal respiration carbon (BRC), and the specific ability of soil microbiota to consume a range of carbon (C) substrates, measured by Biolog ECO MicroPlate.

Results

Intensive management practice significantly decreased (P?<?0.05) soil MBC (in the order of CON > STIP > LTIP), but increased soil BRC (in the order of STIP ≈ LTIP > CON). Under intensive management practices, soil microbial activity, and diversity of C sources utilized by microbial communities decreased (P?<?0.05), as characterized by average well color development (AWCD). Shannon and McIntosh indexes tended to decline with intensive management practices. Intensive management practice also caused much lower (P?<?0.05) utilization of 2-hydroxy benzoic acid and a-cyclodextrin.

Discussion

Soil biological properties were proved to be sensitive indicators of soil quality in response to the intensive management practices, with decreases in soil MBC, microbial activity, and diversity of C sources utilized by microbial communities under the continuing intensive management practices in bamboo stands. This indicates that the intensive management practices had resulted in the negative effect on the soil microbial activities.

Conclusions

Intensive management practices generally had a negative influence on the soil biological properties. This would have important implications for the sustainable management of bamboo production systems in southern China.

Recommendations and perspectives

To minimize the detrimental effect on soil microbial communities, an improved intensive management practice with reducing amounts of mineral fertilizer and increasing organic fertilizer applications are recommended annually so that both high bamboo yield and soil quality can be sustained over a long period.     

Linkage between soil organic carbon and the utilization of soil microbial carbon under plastic film mulching in a semi-arid agroecosystem in China

ABSTRACT

Studying changes in soil organic carbon (SOC) pools and soil microbial C substrate utilization under plastic mulching in different seasons is of great significance for improving soil fertility and sustainable agricultural development. Based on a 2-year plastic film mulching experiment in northeastern China, we investigated the SOC, labile SOC fractions under three treatments: non-mulching (NM), autumn mulching (AM) and spring mulching (SM). The results showed that SOC decreased with soil depth under the AM and SM treatments compared with the NM treatment. The microbial biomass carbon (MBC) and dissolved organic carbon (DOC) under the AM treatment increased significantly in the 0–10 cm soil layer, by 31.2% and 27.2% (p < 0.05), respectively. The AM treatment significantly increased the utilization of amino acids and carbohydrate C sources. Redundancy analysis (RDA) indicated that MBC was the main factor influencing microbial metabolic functional diversity and accounted for the largest variation in the 0–10 cm layer. Pearson’s correlation analysis illustrated that MBC was strongly correlated with the utilization of the microbial C substrate. We suggest that AM may be an effective and sustainable management practice for improving soil quality and maintaining microbial functional diversity in semi-arid agroecosystems in this area.     

Improved nutrient status affects soil microbial biomass,respiration, and functional diversity in a Lei bamboo plantation under intensive management

Purpose

Intensive management, such as fertilization and organic mulching, is applied frequently in Lei bamboo (Phyllostachys praecox) plantations to achieve higher production in subtropical China. However, responses as well as key impact factors of soil microbial properties under such management remain uncertain. We analyzed the relationships between nutrient changes and microbial properties and assessed the main factors determining microbial biomass, activity, and functional diversity in soils under intensive management in a Lei bamboo plantation.

Materials and methods

Soil samples of treatments of no fertilization (control), chemical fertilization (CF), and chemical and organic fertilization combined with organic mulching (CFOM + M) were taken before mulching. The soil organic carbon (SOC), dissolved organic carbon, and total and available nitrogen (N), phosphorus (P), and potassium (K) were measured. Microbial biomass carbon (MBC), basal respiration, and mineralization were also analyzed. Community level of physiological profile (CLPP) of microorganisms was analyzed by BIOLOG method to estimate the functional diversity and carbon (C) source utilization patterns of microbes. Principal component analysis (PCA), principal response curve (PRC), correlation analysis, regression analysis, and redundancy analysis (RDA) were performed to clarify changes in variables and determine the factors influencing microbial properties.

Results and discussion

SOC and total and available N, P, and K increased as follows: CFOM + M > CF > control. However, C/P and N/P ratios showed an opposite trend. MBC and respiration were not affected, but microbial quotient and metabolic quotient declined under intensive management. McIntosh diversity index was much higher in CFOM + M. The PCA showed that microorganisms in CFOM + M had a stronger ability to use most C sources. Weaker utilization of serine indicated an alleviation of nutrient deficiency in CFOM + M. PRC of CLPP showed a significant treatment effect and that utilization of serine sensitively responded to nutrient status over the whole incubation time. RDA showed that total and available N, total K, and C/P were the main factors influencing utilization of C sources by microbial communities.

Conclusions

Fertilization combined with organic mulching increased soil nutrients, microbial biomass, and respiration in a Lei bamboo plantation. Abundant nutrients also increased C source use efficiency of microorganisms under intensive management. Changes of N and K and C/P might have led to a shift in microorganisms toward a different life strategy and determined the change in C source utilization patterns of microbial communities.

     

No‐tillage with half‐amount residue retention enhances microbial functional diversity,enzyme activity and glomalin‐related soil protein content within soil aggregates

A 3‐year field tillage and residue management experiment established in North China was used to analyse topsoil (0–15 cm) aggregation, and microbial functional diversity, enzyme activity and glomalin‐related soil protein (GRSP) content within aggregates. Compared with conventional tillage (CT), no‐tillage (NT) alone significantly (P < 0.05) increased organic C contents in 50–250 and <2 μm aggregates and decreased the proportion of C accumulated by 2–50 μm aggregates and microbial functional diversity indices in <2 μm aggregates. Regardless of tillage practice, both half‐amount (C50) and full (C100) residue retention tended to increase organic C and GRSP contents, or dehydrogenase and invertase activities, in certain aggregates. Under CT, a poorer performance of C50 than C100 was observed in maintaining Shannon index (H′) and Simpson index (D) in >250 and <2 μm aggregates, and also McIntosh index (U) in <2 μm aggregates, owing to insufficient residue and possible decreases in the distribution of decomposer micro‐organisms. Under NT, however, C50 was more effective than C100 in maintaining/elevating H′, D and U in all soil aggregates except for 50–250 μm, suggesting that surplus residue may induce worse soil conditions, decreasing heterotrophic microbial activities. Thus, NT with half‐amount residue retention improved soil physical–chemical–biological properties and could be a useful management practice in North China.     

不同干扰强度下农业生态系统土壤微生物生物量和活性的分异

Different management practices in six agroecosystems located near Goldsboro, NC, USA were conducted including a successional field (SU), a plantation woodlot (WO), an integrated cropping system with animals (IN), an organic farming system (OR), and two cash-grain cropping systems employing; either tillage (CT) or no-tillage (NT) to examine if and how microbial biomass and activity differ in response to alterations in disturbance intensity from six land management strategies. Results showed that soil microbial biomass and activity differed, with microbial activity in intermediately disturbed ecosystems (NT, OR, IN) being significantly higher (P < 0.01) than systems with either high or low disturbance intensities. There was also a significant and a highly significant ecosystem effect from the treatments on microbial biomass C (MBC) (P < 0.05) and on microbial activity (respiration) (P < 0.01), respectively. Multiple comparisons of mean respiration rates distinctly separated the six ecosystem types into three groups: CT < NT, SU and WO < OR and IN. Thus, for detecting microbial response to disturbance changes these results indicated that the active component of the soil microbial community was a better indicator than total biomass.     

Soil microbial activity and biomass is stimulated by leguminous cover crops

The leguminous cover crops Atylosia scarabaeoides (L.) Benth., Centrosema pubescens Benth., and Pueraria phaseoloides (Roxb.) Benth., were grown in the interspaces of a 19 y–old coconut plantation and incorporated into the soil at the end of the monsoon season every year. At the end of the 12th year, soils from different depths were collected and analyzed for various microbial indices and their interrelationships. The objectives were to assess the effects of long‐term cover cropping on microbial biomass and microbial‐community structure successively down the soil profile. In general, total N (TN), organic C (OC), inorganic N, extractable P, and the levels of biological substrates viz., dissolved organic C (DOC) and N (DON), labile organic N (LON), and light‐fraction organic matter (LFOM) C and N decreased with depth at all the sites. Among sites, the cover‐cropped (CC) sites possessed significantly greater levels of TN, OC, DOC, DON, and LON compared to the control. Consequently, microbial biomass C (MBC), N (MBN), and P (MBP), CO₂ evolution, and ATP levels, in general, decreased with depth at all sites and were also significantly higher in the CC sites. Among the ratios of various microbial indices, the ratio of MBC to OC and metabolic quotient (qCO₂) declined with depth. Higher MBC‐to‐OC ratios and large qCO₂ levels in the surface soils could be ascribed to greater levels of readily degradable C content and indicated short turnover times of the microbial biomass. In contrast, the ratios of MBC to MBN and MBC to MBP increased with depth due to low N/P availability and relatively higher C availability in the subsoils. Cover cropping tended to enhance the ratios of MBC to OC, MBC to MBN, MBC to MBP, and ergosterol to MBC and decreased the ATP‐to‐MBC ratio at all depths. The relatively lower ATP‐to‐MBC ratios in the CC site, especially in the subsoil indicated microbial‐community structure possibly dominated by fungi. By converting the ergosterol content to fungal biomass, it was observed that fungi constituted 52%–63% of total biomass C at the CC site, but only 33%–40% of total biomass C at the control site. Overall, the study indicated that leguminous cover crops like P. phaseoloides or A. scarabaeoides significantly enhanced the levels of OC, N and microbial activity in the soils, even down to 50 cm soil depth.     

氯甲基吡啶对滴灌棉田土壤微生物群落功能多样性的影响

已知硝化抑制剂氯甲基吡啶能有效抑制土壤硝化,减少氮的淋洗和硝化-反硝化损失,促进作物对氮素的吸收,但是其对干旱区滴灌条件下土壤微生物群落功能多样性的影响尚不明确。本试验研究了尿素添加氯甲基吡啶(Nitrapyrin)分次随水滴施对干旱区滴灌棉田土壤微生物碳代谢和群落功能多样性的影响。试验采用随机区组设计,设置不施氮肥[CK,0 kg(N)·hm~(-2)]、单施尿素[Urea,225 kg(N)·hm~(-2)]和尿素添加氯甲基吡啶[Urea+nitrapyrin,225 kg(N)·hm~(-2)+2.25 kg(nitrapyrin)·hm~(-2)]3个处理,重复4次,采用Biolog-ECO法进行土壤微生物碳代谢和功能多样性研究。结果表明:与不施氮肥(CK)相比,施用尿素和尿素添加氯甲基吡啶均能显著提高土壤微生物对31种碳源的代谢能力(AWCD)和代谢强度(S)(P0.05),增加土壤微生物多样性和丰富度(Shannon指数、Simpson指数、Mc Intosh指数和Richness指数)以及对各类碳源的利用能力。尿素添加氯甲基吡啶随水滴施后,土壤微生物AWCD值、碳代谢强度、Shannon指数、Simpson指数、Mc Intosh指数以及Richness指数均大于单施尿素处理,且较单施尿素处理分别提高13.83%、9.33%、1.29%、1.34%、11.26%、11.79%(P0.05),均匀度指数则低于单施尿素处理(P0.05)。PCA和聚类分析结果表明,施用尿素和尿素添加氯甲基吡啶对土壤微生物群落功能多样性均产生了显著影响,但尿素添加氯甲基吡啶与单施尿素处理差异不显著;氯甲基吡啶的添加提高了土壤微生物对聚合物、酚酸、羧酸、氨基酸以及胺类的利用,降低了对碳水化合物的利用(P0.05)。上述研究结果得出,在干旱区滴灌棉田,尿素添加氯甲基吡啶分次随水滴施可调控土壤的微生态环境,在一定程度上提高土壤微生物的代谢能力,增加微生物群落功能多样性,缓解因长期施用无机氮肥导致的土壤微生物活性的降低。     

Effects of Waxy Maize Relay Intercropping and Residue Retention on Rhizosphere Microbial Communities and Vegetable Yield in a Continuous Cropping System

Intercropping and residue retention contribute to high yield and quality of crops. However, their coupled effects on rhizospheric microbial communities under a continuous vegetable cropping system have not been adequately addressed. The objective of the present study was to assess the effects on soil microbial community and yields of waxy maize(Zea mays L.) intercropped with or without residue retention in a continuous broccoli(Brassica oleracea L.) cropping system, i.e., relay intercropping of broccoli and waxy maize(B/M-B), relay intercropping of broccoli and waxy maize with residue retention(B/MR-B), and broccoli monoculture(B-B). The biomass yields of spring and autumn vegetables in B/MR-B were 16.3%–32.5% and 30.1%–46.1% higher than those of B-B,respectively. Autumn vegetable economic yields of B/MR-B were 28.2%–40.3% higher than B-B. The average well color development followed the order: B/MR-B B/M-B B-B. The Shannon index, Simpson index, and Mc Intosh index were higher in B/MR-B than under monoculture. A principal component analysis showed that microbial communities of B/MR-B soils differed from those of B/M-B and B-B soils. Carbon(C) sources utilized by the rhizosphere microorganisms were mainly carbohydrates, carboxylic acids, amino acids, and polymers; however, the C sources for the soil microbial community differed between intercropping and monoculture. The communities from B/MR-B preferred amino acids and polymers. Available nitrogen(N), potassium(K), and phosphorus(P) had an obvious impact on soil microbial community. Additionally, the C source utilization by microorganisms was significantly affected by p H and available K and P. Cropping system diversification through relay intercropping and residue retention effectively improved the functional diversity of the soil microbial communities and increased the yields of vegetables.     

Temporal changes in fertility and microbial properties of soil in forest-converted oil palm plantations in Okomu forest reserve,Nigeria

Evidence of the impacts of land-use change on soil biological activities, a determinant of nutrient cycling in soil, will provide a better understanding of soil health and productivity. The study investigates temporal changes in soil chemical and microbial properties in a forest converted to oil palm plantation. Soil samples from four locations: native forest and Elaeis guineensis plantations of 2-, 13- and 14-year were collected. Total carbon C and N were significantly higher (p < 0.05) in the native forest (NF) followed by 14- and 13-year E. guineensis plantations respectively. Microbial biomass carbon (MBC) and nitrogen (MBN) in NF were significantly higher (p < 0.05) than in the E. guineensis plantations. There were no significant differences in the microbial biomass phosphorus (MBP) among the E. guineensis plantation of all ages. The qCO₂ in the 13- and 14-year E. guineensis plantations was higher than in NF and 2-year E. guineensis plantation. There was a positive correlation between MBC, MBN, MBP and pH, P, TC, and TN. These results indicated that conversion of native forest to E. guineensis plantation affected soil nutrient and microbial properties. And there could be a return to healthy soil condition as age of E. guineensis plantation increased.     

Land use changes the soil carbon stocks,microbial biomass and fatty acid methyl ester (FAME) in Brazilian semiarid area

Land use affect soil C and microbial structure, especially in tropical dry areas. The objective of this study was to evaluate the effects of the land use on physical, chemical, and microbiological attributes of soils from Brazilian semiarid. We analyzed soil physical, chemical, total carbon stocks (TCS), water-soluble carbon (WSC), microbial biomass carbon (MBC) and microbial structure of soil from forest, no irrigation maize, succession areas (Anadenanthera falcate and Tabebuia alba) and secondary shrubby vegetation. The use of soil influences C stock. The forest soil showed higher TCS and MBC. The conversion in T. alba reduced in 9% soil total bacteria. The multivariate analysis showed that TCS, MBC and FAMEs contributed to separation of natural forest and other areas in the superficial layer. This study indicates that the conversion of forest into successional areas can decrease by up to 44% TCS and 68% MBC. The present study provided alarming data concerning the impact of land use on quality of soil in a tropical dry region in Northeastern Brazil. Our results provide an alternative tool for the management of deforested dry areas that could serve as guideline for management plan to sustainability for agricultural impacted dry areas.     

Influence of vegetation types and soil properties on microbial biomass carbon and metabolic quotients in temperate volcanic and tropical forest soils

Abstract

There is limited knowledge about the differences in carbon availability and metabolic quotients in temperate volcanic and tropical forest soils, and associated key influencing factors. Forest soils at various depths were sampled under a tropical rainforest and adjacent tea garden after clear-cutting, and under three temperate forests developed on a volcanic soil (e.g. Betula ermanii and Picea jezoensis, and Pinus koraiensis mainly mixed with Tilia amurensis, Fraxinus mandshurica and Quercus mongolica), to study soil microbial biomass carbon (MBC) concentration and metabolic quotients (qCO₂, CO₂-C/biomass-C). Soil MBC concentration and CO₂ evolution were measured over 7-day and 21-day incubation periods, respectively, along with the main properties of the soils. On the basis of soil total C, both CO₂ evolution and MBC concentrations appeared to decrease with increasing soil depth. There was a maximal qCO₂ in the 0–2.5 cm soil under each forest stand. Neither incubation period affected the CO₂ evolution rates, but incubation period did induce a significant difference in MBC concentration and qCO₂ in tea soil and Picea jezoensis forest soil. The conversion of a tropical rainforest to a tea garden reduced the CO₂ evolution and increased the qCO₂ in soil. Comparing temperate and tropical forests, the results show that both Pinus koraiensis mixed with hardwoods and rainforest soil at less than 20 cm depth had a larger MBC concentration relative to soil total C and a lower qCO₂ during both incubation periods, suggesting that microbial communities in both soils were more efficient in carbon use than communities in the other soils. Factor and regression analysis indicated that the 85% variation of the qCO₂ in forest soils could be explained by soil properties such as the C:N ratio and the concentration of water soluble organic C and exchangeable Al (P < 0.001). The qCO₂ values in forest soils, particularly in temperate volcanic forest soils, decreased with an increasing Al/C ratio in water-soluble organic matter. Soil properties, such as exchangeable Ca, Mg and Al and water-soluble organic C:N ratio, were associated with the variation of MBC. Thus, MBC concentrations and qCO₂ of the soils are useful soil parameters for studying soil C availability and microbial utilization efficiency under temperate and tropical forests.     

放牧干扰对岷江上游山地森林-干旱河谷交错带土壤微生物量及呼吸熵的影响

选择岷江上游理县山地森林/干旱河谷交错带地区人工刺槐林、人工杨柳林、草地和锥花小檗灌丛这4种植被类型为研究对象,对4种植被下的土壤微生物量及呼吸熵对放牧干扰的响应进行了研究。以距牧道距离远近的不同设置了3种放牧干扰强度处理,分别对各植被类型3种放牧干扰强度的土壤进行了分析。结果表明,在各植被类型下,土壤有机碳(SOC)和土壤微生物量碳(MBC)含量随放牧干扰强度的增加而降低。各植被类型下表层土壤呼吸熵值(qCO2)值随放牧压力的增加而增大(除灌丛中度干扰外),增加幅度为15.14%~100.54%,说明放牧干扰使微生物体的周转率加快,对SOC的利用率降低,释放的CO2增多,土壤碳保存率降低。     

山核桃集约经营过程中土壤微生物量碳氮的变化

[目的]研究不同集约经营历史山核桃林的土壤微生物量碳氮的演变规律,为山核桃林地土壤管理提供科学依据。[方法]在浙江省临安市分别采集并分析了经营历史为5,10,15,20a的山核桃林土壤样品,并与天然混交林(0a)进行比较。[结果]天然混交林改造为山核桃纯林并经集约经营后,林地土壤微生物量碳(MBC)、微生物量氮(MBN)、MBC/MBN,MBC/SOC均表现出先下降而后上升的趋势,经过10a经营后降到最低水平,与0a相比,0—10cm土层MBC,MBN和MBC/SOC分别降低了52.1%,32.0%和31.0%。经营10a的林地土壤MBC/MBN显著低于前期经营林地,而MBN/TN在经营过程中的差异并不显著。[结论]山核桃集约经营后,林地土壤微生物量碳氮含量显著下降。     

Organic mulch and fertilization affect soil carbon pools and forms under intensively managed bamboo (<Emphasis Type="Italic">Phyllostachys praecox</Emphasis>) forests in southeast China

Purpose  

Phyllostachys praecox is one of the bamboo species used for the production of fine edible bamboo shoots and is widely distributed in Southern China. To maintain or increase the productivity of bamboo shoots, P. praecox forests are intensively managed through heavy fertilization and surface mulch of organic residues such as rice husk to increase soil temperature in the winter. Such management techniques can markedly influence soil quality and the dynamics of soil carbon (C). The objectives of this study were to investigate the long-term impact of intensive management practices on carbon pools and forms in the soil of bamboo forests and explore relationships between different soil organic C fractions, as little such information is currently available.     

集约经营雷竹林土壤微生物的演变

Phyllostachys praecox C. D. Chu et C. S. Chao, a favored bamboo shoot species, has been widely planted in recent years. Four stands with different historical management practices were selected for this study to understand the evolution of soil microbial ecology by determining the effects of a new mulching and heavy fertilization practice on soil quality using microbiological parameters. Compared with the traditional practice (index 1), microbial biomass carbon (MBC) and soil microbial respiration carbon (MRC) with the new management practice significantly decreased (P < 0.01 and P < 0.05, respectively) with 1--2 years of mulching (index 2) and then for continued mulching significantly increased (P < 0.05). The ratios of MBC/TOC (total organic carbon) and MRC/TOC also significantly diminished (P < 0.05) with mulching. The average well color development (AWCD) and Shannon index decreased with mulching time, and the significant decrease (P < 0.05) in Shannon index occurred from index 2 to index 3. The results from a principal components analysis (PCA) showed that the scores of the first principal component for indexes 1 and 2 were significantly larger (P < 0.05) than soils mulched 3--4 years or 5--6 years. Also, the second principal component scores for index 1 were larger than those for index 2, suggesting that the ability of soil microorganisms to utilize soil carbon was decreasing with longer use of the new management practice and causing a deterioration of soil biological properties.     

退化马尾松林恢复过程中芒萁覆盖对土壤微生物生物量碳氮及其周转的影响

为探究侵蚀退化红壤马尾松林恢复过程中林下芒萁对土壤微生物生物量碳氮月动态及其周转的影响,以不同恢复年限的马尾松林为研究对象,对比分析马尾松林恢复过程中林下保留芒萁、去除芒萁处理和林下裸地土壤中12个月的土壤微生物生物量碳(MBC)和微生物量氮(MBN)含量及其周转速率、周转时间和流通量,并分析其与土壤理化性状的关系。结果表明:(1)保留芒萁覆盖处理的MBC和MBN平均含量分布比林下裸地提高26.99%~277.31%和13.54%~173.39%,而去除芒萁处理分布比保留芒萁处理降低12.29%~27.01%和5.02%~28.45%,差异均随恢复年限呈先降低后增加的趋势。(2)所有处理的土壤微生物量碳氮季节动态均表现为春夏季较高,秋冬季较低的趋势,进入生长季前的土壤微生物量碳氮含量更能反映该地区的平均水平。(3)在退化马尾松林恢复过程中,芒萁覆盖降低土壤微生物生物量碳氮周转速率,增加周转时间,提高土壤微生物生物量碳氮含量和流通量,促进土壤有机质的积累和养分释放。相关分析和逐步回归分析表明,MBC、MBN流通量分别与DOC、DON呈显著正相关,周转速率分别与铵态氮(NH₄⁺-N)和TN呈显著负相关,表明土壤碳和氮及其有效性是影响土壤微生物量周转的关键因素。     

黄土高原半干旱地区撂荒地次生植被演替过程中土壤微生物活性研究

To show the vegetation succession interaction with soil properties, microbial biomass, basal respiration, and enzyme activities in different soil layers (0--60 cm) were determined in six lands, i.e., 2-, 7-, 11-, 20-, 43-year-old abandoned lands and one native grassland, in a semiarid hilly area of the Loess Plateau. The results indicated that the successional time and soil depths affected soil microbiological parameters significantly. In 20-cm soil layer, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), MBC/MBN, MBC to soil organic carbon ratio (MBC/SOC), and soil basal respiration tended to increase with successional stages but decrease with soil depths. In contrast, metabolic quotient (qCO2) tended to decrease with successional stages but increase with soil depths. In addition, the activities of urease, catalase, neutral phosphatase, β-fructofuranosidase, and carboxymethyl cellulose (CMC) enzyme increased with successional stages and soil depths. They were significantly positively correlated with microbial biomass and SOC (P < 0.05), whereas no obvious trend was observed for the polyphenoloxidase activity. The results indicated that natural vegetation succession could improve soil quality and promote ecosystem restoration, but it needed a long time under local climate conditions.     

Interrelationship of Carbon Sequestration,Soil Fertility,and Microbial Indices as Influenced by Long-Term Land Uses in Lower Himalayan Region,India

The study was conducted to determine the long-term impact of different land uses on carbon sequestration, soil fertility, and microbial indices and to establish their interrelationship in a light-textured hyperthermic Udic Ustochrept. Soil samples were collected from existing land-use systems of (1) Eucalyptus tereticornis, (2) Terminalia chebula, (3) Acacia nilotica, (4) Leucaena leucocephala, (5) Embilica officinalis, (6) Zizyphus spp., and (7) maize–wheat rotation from depths of 0–15, 15–30, and 30–45 cm and examined for pH; organic carbon (OC); electrical conductivity (EC); available nitrogen (N), phosphorus (P), and potassium (K); micronutrients; microbial biomass carbon (MBC); microbial biomass nitrogen (MBN); and microbial biomass phosphorus (MBP). High-density plantations of Eucalyptus teriticornis had a greater potential in sequestering aboveground carbon (472.37 Mg ha^?1), compared to widely spaced trees of Acacia nilotica (376.05 Mg ha^?1). Eucalyptus teriticornis exhibited the greatest impact in increasing soil OC in all depths, followed by Acaccia nilotica and Terminalia chebula, and the lowest was in agriculture (0.778, 0.749, 0.590, and 0.471%, respectively, in surface soil). Available zinc and iron contents were greatest under Eucalyptus tereticornis, followed by Acacia nilotica, Zizyphus mauritiana, Embilica officinalis, Terminalia chebula, and Leucaena leucocephala. The MBC and MBN were greatest in Eucalyptus tereticornis, followed by Acacia nilotica, and lowest in agriculture. Correlation matrix revealed significant and positive relationships between carbon sequestered with OC, MBC, MBN, and MBP.     

冀北辽河源油松天然林土壤微生物碳代谢特征研究

本文以冀北辽河源地区不同林龄油松天然林为研究对象,研究其土壤微生物生物量碳、微生物呼吸及微生物代谢熵随油松林龄的变化趋势。结果表明:随着油松天然林林龄的增加,土壤微生物生物量碳逐渐增加;而土壤微生物呼吸则呈现出先减小后增加的趋势;微生物代谢熵表现为随油松林林龄的增加而降低。相关性分析表明,土壤微生物生物量碳、微生物呼吸分别与微生物代谢熵之间呈现高度的极显著线性负相关。微生物生物量碳与微生物呼吸呈极显著正相关,但线性相关程度较弱。土壤微生物生物量碳和微生物呼吸与土壤温度和含水量均呈极显著正相关,而土壤微生物代谢熵则与土壤温度、土壤含水量呈极显著负相关。上述结果表明,在冀北辽河源地区,土壤微生物生物量碳、微生物呼吸、微生物代谢熵与油松天然林林龄密切相关。随着油松天然林林龄的增加,其土壤微生物活性增强,碳代谢效率增加,土壤质量及可持续利用潜力更高,土壤生态体系更加成熟。