Moso bamboo (<Emphasis Type="Italic">Phyllostachys edulis</Emphasis> (Carriere) J. Houzeau) invasion affects soil phosphorus dynamics in adjacent coniferous forests in subtropical China

Key message

The invasion of moso bamboo ( Phyllostachys edulis (Carriere) J. Houzeau) into neighboring Cryptomeria japonica (L. f.) D. Don plantations significantly altered soil P status and dynamics. This alteration in phosphorus dynamics must be considered when assessing the ecological consequence of moso bamboo invasion in subtropical China.

Context

Moso bamboo is a native species that commonly invades into adjacent forests in Asia. Such invasions may significantly alter soil chemical characteristics because moso bamboo has very different traits compared with the tree species it displaces. However, few studies have investigated the effects of moso bamboo invasion on soil phosphorus (P) dynamics.

Aims

The objective of this study was to investigate the effects of moso bamboo invasion on soil P dynamics. Specifically, we quantified soil total P, available P, acid phosphatase activity (APA), and microbial biomass P (MBP) in moso bamboo-invaded coniferous stands and compared them to uninvaded stands and pure moso bamboo stands.

Methods

We compared seasonal dynamics of soil P (e.g., total P, available P, APA, and MBP) over a 24-month period among three stand types at Lushan mountain in subtropical China: Cryptomeria japonica plantation (CR), Cryptomeria japonica plantation invaded by Phyllostachys edulis (PH-CR), and Phyllostachys edulis stand (PH).

Results

Total soil P concentration was significantly lower in PH-CR than in CR and PH stands, but soil available P concentration was significantly lower in CR and PH stands. Soil APA was significantly higher in PH-CR than in CR and PH stands. Similarly, soil MBP concentration was higher in PH-CR than in CR and PH stands. Also, soil total P, available P, APA, and MBP concentrations displayed seasonal fluctuations in PH-CR, but remained relatively stable in CR and PH stands during the 2 years.

Conclusion

The invasion of moso bamboo into adjacent C. japonica stands significantly increased soil available P, acid phosphatase activity, and microbial biomass phosphorus, but decreased soil total P. The implication of these changes to ecosystem composition, structure, and function must be explicitly considered in managing moso bamboo invasion in subtropical China.

     

Seasonal variations in phosphorus fractions in semiarid sandy soils under different vegetation types

We investigated the seasonal patterns of soil phosphorus (P) fractions under five vegetation types – Ulmus macrocarpa savanna, grassland, Pinus sylvestris var. mongolica plantation, Pinus tabulaeformis plantation, and Populus simonii plantation – in the southeastern Keerqin Sandy Lands of China. The measured P fractions (0–20 cm depth) included: soil total P (TP), total organic and inorganic P (TPo and TPi), bicarbonate extractable organic and inorganic P (BPo and BPi), microbial biomass P (MBP), and in situ resin-adsorbed P (resin-P). Soil TP and TPo concentrations in the savanna and grassland were significantly lower in summer than in spring and autumn. However, they were relatively stable in three forest plantations. Soil labile P fractions showed a significant seasonal pattern under all vegetation types with the peak in summer, except soil MBP that was constant in the savanna and grassland and BPo that decreased over time in the savanna. This pattern of labile P fractions was attributed to a combination of seasonal climatic changes, low P availability, as well as the biological controls of soil P transformation in the study area. Litter decomposition played a key role in soil P availability. The monthly resin-P released from litter decomposition in summer was 2.6–7.4 times greater than in other seasons, and was 1.7–3.4 times of that in the 10 cm depth soil. Concentrations of soil P fractions were obviously affected by vegetation type. The savanna had the highest total P and MBP concentrations and the P. tabulaeformis plantation had the highest BPi and resin-P among all vegetation types. Among forest plantations, P. simonii plantation had the highest total P and MBP. These results suggest that U. macrocarpa savanna is the best system conserving soil nutrient (particularly P) stocks and microbial activity, followed by the grassland and P. simonii plantation, while the pine plantations are the worst.     

Relationships between larch growth and forest site factors

Dahurian larch (Larix gmelinii Rupr.) Rupr is one of the dominant species in both natural and man-made forests in northeast China. Effects of site factors, including topography, soil properties and nutrient elements (P, Ca, K, Mg, Mn, Zn, Cu, Ag, Co and Ni) on the growth of larch were analyzed in detail, qualitatively and quantitatively. The ordination technique was used to group the site factors and to classify sites for larch. Analysis indicated that height growth, diameter (DBH) and volume of the larch varied among site types and this will be of theoretical and practical significance in developing larch plantations.     

Distribution of carabid beetles among 40-year-old regenerating plantations and 100-year-old naturally regenerated forests in Southwestern China

Effects of reforestation by native tree species on species assemblages of carabid beetles were studied between 40-year-old regenerating plantations and 100-year naturally regenerated forests in Southwestern China. Two old naturally regenerated forest types (ca.100 years old) were chosen: hemlock-spruce forests (Tsuga chinensis and Picea brachytyla) and birch forests (Betula albo-sinensis). Three young regenerating forest types (ca. 40 years old), including spruce plantations (P. brachytyla), larch plantations (Larix kaempferi and Larix mastersian), and natural broad-leaved forests, were established after the logging of the old naturally regenerated forests. Using pitfall traps, we compared the distribution of carabid beetles in the five forest types. Three replicated plots for each forest type were chosen, and each plot was investigated with four trap sites twice each month during the growing season (May to October) in 2004. Our results showed that species richness and abundance were significantly higher in the young regenerating forests than in the old naturally regenerated forests. Analysis of complementarity in carabid species lists across the forest ages and types showed that the old naturally regenerated birch forests had the lowest similarity with the young regenerating larch plantations, and the highest similarity was shown between the two young regenerating plantations. Although PCoA ordination grouped the carabid assemblages according to forest type and forest age, the overall similarity among all forest types was high. Moreover, quantitative character species analysis did not detect significant species associated with forest types and ages. Based on the specificity and fidelity, most carabid species were abundant in all habitats, and only a few species were restricted in one or two forest types. Multiple linear regression between the species richness, abundance and Shannon diversity of carabids and of five environmental variables showed that the cover of canopy and herbaceous layer, and the depth of leaf litter had significant effects in determining richness, abundance and diversity of carabid beetles. Thus, the young regenerating forests at the mature stage could provide an appropriate habitat for most forest species of carabids survived in adjacent old naturally regenerated forests and might replace the role in part of the old-growth forests in sustaining the diversity of carabid assemblages. But some species are still restricted in old naturally regenerated forests, so in order to protect the diversity of carabid assemblages, it is necessary to sustain the intact old naturally regenerated forests when reforesting with some native tree species following natural succession.     

The effect of understory removal on microclimate and soil properties in two subtropical lumber plantations

Understory vegetation is an important component in forest ecosystems. However, the effects of understory on soil properties in subtropical forests are not fully understood. We thus conducted an experimental manipulative study in two young fast-growing plantations—Eucalyptus urophylla and Acacia crassicarpa—in southern China, by removing understory vegetation in both plantations, to estimate the effects of understory vegetation on microclimate, soil properties and N mineralization. Our data showed that, after 6 months, understory removal (UR) in both plantations had greatly increased soil surface luminous intensity (90–500 cd) and temperature (0.5–0.8 °C); soil moisture was reduced in the Eucalyptus plantation but not in the Acacia plantation. Understory removal also reduced soil organic matter (SOM), but had little impact on other soil chemical properties, including total phosphorus, C/N, pH, exchangeable cations (K, Ca, Mg), available P, ande extractable NH₄–N and NO₃–N. We found a significant decline of soil N mineralization and nitrification rates in the 0–5 cm soils of UR in both plantations. The decline of SOM in UR may contribute to the lower N transformations rates. This study indicates that a better understanding of understory vegetation effects on soil N cycling would be beneficial to forest management decisions and could provide a critical foundation for advancing management practices.     

甘肃小陇山日本落叶松人工林不同发育阶段土壤理化性质的变化

采用时序研究法对甘肃小陇山林区日本落叶松人工林不同发育阶段(6、15、23、35 a)的土壤物理性质、化学性质进行多因子综合比较,利用主成分分析的方法,以主成分特征贡献率为权重,计算土壤肥力综合指标值,分析土壤性质的演变规律。结果表明:日本落叶松人工林发育至近熟林阶段,土壤物理性质变差,表现为土壤密度最大1.62g·cm-3,毛管孔隙度和最大持水量降至最低,分别为29.69%、24.45%,并且土壤有机质、氮、磷、钾、镁、钙含量也明显降低;而到成熟林阶段,土壤理化性质有显著改善,土壤密度降低为1.21 g·cm-3、毛管孔隙度和最大持水量恢复至45.56%、42.65%,土壤养分含量也有了很大的提高,甚至超过了中龄林阶段的水平;同时幼龄林、中龄林、近熟林和成熟林土壤性质综合得分分别为-0.329、0.188、-0.565、0.739,也表明近熟林土壤性质最差,成熟林土壤性质最好。     

Phosphorus dynamics and solubilizing microorganisms in acid soils under different land uses of Lesser Himalayas of India

Although chemical and some soil physical properties have been studied under different land uses of the Lesser Himalayas of India, very limited information is available on soil biochemical properties. Hence we investigated phosphorus (P) fractions [total P (TP), inorganic P (P_i), organic P (P_o), available P, microbial biomass P (MBP)], enzyme activities [dehydrogenase, phosphatases, phytase], phosphate solubilizing bacteria (PSB) and fungi (PSF), and their correlations of acid soils (0–15 and 15–30 cm depths) under different land uses (viz, organic farming, maize–wheat, apple orchard, undisturbed oak forest and uncultivated land of the Indian Himalayas). All land use systems differed significantly for the P fractions, except TP. The highest values for TP, P_i, available P and MBP were found in soils under oak forest and lowest in uncultivated land. However, P_o content was highest in apple orchard. The organic farming (organic manures field under garden pea-french bean cropping system for > 10 years) maintained highest activities of dehydrogenase, acid phosphatase and alkaline phosphatase. The highest phytase activity and highest numbers of PSB (99 × 10³ g^?1 soil) and PSF (30 × 10³ g^?1 soil) were observed in the rhizosphere soils of oak forest. Significant relationships between soil P fractions and enzyme activities, except alkaline phosphatase, were recorded in surface soil layer. PSB and PSF population were also correlated significantly with P fractions and enzyme activities. This would lead us to understand the level of degradation of P pools due to cultivation over forest system and the suitable management practices needed for soil quality restoration.     

Soil phosphorus fractions and their availability over natural succession from clear-cut of a mixed broadleaved and Korean pine forest in northeast China

To assess phosphorus (P) status of forest soil under naturally restored vegetation,P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest.Four communities of shrub,softwood broad-leaved forest,softwood and hardwood broad-leaved forest,and hardwood broad-leaved forest represented different succes-sional stages.A soil sample from a primary broad-leaved and Korean pine stand was the control.A sequential P frac-tionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P.The results show that available P increased significantly with long-term succession,while both sodium bicarbonate-extractable P(NaHCO3-P) and sodium hydroxide-extractable P (NaOH-P) fractions were reduced in early successional stages and increased in late stages.Compared to the primary forest,concentrations of P fractions in the four stages signifi-cantly decreased except for HCl-P,indicating that soil P supplements over the long-term did not return to primary forest levels.The results of related analysis also showed that NaHCO3-Pi levels were significantly related to avail-able phosphorus.According to the path analysis coeffi-cient,NaHCO3-Pi exhibited the highest effect on available P among eight P fractions;the indirect effects of other P fractions via NaHCO3-Pi were larger than those with other P fractions.Overall,this study suggests that soil P bioavail-ability gradually improved during natural vegetation res-toration on clear-cut sites mainly through the increase of NaHCO3-P,where phosphorous is immediately available,and subsequently available phosphorus NaOH-P.     

Seasonal soil CO2 efflux dynamics after land use change from a natural forest to Moso bamboo plantations in subtropical China

Moso bamboo plantations (Phyllostachys pubescens) are one of the most important forest types in southern China, but there is little information on the effects of their establishment and silvicultural practices on soil CO₂ efflux. The objectives of this study were to evaluate the effect of land use change from a natural broadleaf evergreen forest to Moso bamboo plantations and their management practices on soil CO₂ efflux in a subtropical region of China using static closed chamber method. Regardless of the land uses or management practices, the effluxes over a 12-month period had a seasonal pattern, with the maximum effluxes observed in summer and the minimum in winter. Whereas there was no significant difference in the total annual soil CO₂ efflux between the natural broadleaf evergreen forest (BL) and the conventionally managed bamboo forests (CM), soil CO₂ efflux in the intensively managed bamboo forest (IM) was significantly higher. Soil temperature was the most important environmental factor affecting soil CO₂ efflux rates for all three land uses. Soil moisture also had a significant positive correlation with soil CO₂ efflux rates. Soil temperature and moisture had greater influence on soil CO₂ efflux rate in the IM than the CM and BL forests. Soil dissolved organic C had a positive correlation with soil CO₂ efflux rate in the CM, but had no significant correlation with that in the IM or the BL forests. Our study for the first time demonstrated that conversion of the natural subtropical broadleaf evergreen forest to Moso bamboo does not increase soil CO₂ efflux. However, when bamboo forests are under intensive management with regular tillage, fertiliser application and weeding, significantly more soil CO₂ emission occurs. Therefore, best management practices should be developed to reduce soil CO₂ efflux in Moso bamboo plantations in the subtropical regions of China.     

Effects of freeze-thaw on soil nitrogen and phosphorus availability at the Keerqin Sandy Lands, China

A laboratory simulated freeze-thaw was conducted to determine the effects of freeze-thaw on soil nutrient availability in temperate semi-arid regions. Soil samples were collected from sandy soils （0-20 cm） of three typical ecosystems （grassland, Mongolian pine plantation and poplar plantation） in southeastern Keerqin Sandy Lands of China and subjected to freeze-thaw treatment （-12℃ for 10 days, then r 20℃ for 10 days） or incubated at constant temperature （20℃ for 20 days）. Concentrations of the soil NO3^--N, NH4^＋-N, NaHCO3 extractable inorganic P （LPi） and microbial biomass P （MBP） were determined on three occasions： at the start of the incubation, immediate post-thawing and at the 10th day post-thawing. The results showed that soil net nitrification and N mineralization rates at three sites were negatively affected by freeze-thaw treatment, and decreased by 50%-85% as compared to the control, of which the greatest decline occurred in the soil collected from poplar plantation. In contrast, the concentration of soil NH4^＋-N, NaHCO3 extractable inorganic P （LPi） and microbial biomass P were insignificantly influenced by freeze-thaw except that LPi and NH4^＋-N showed a slight increase immediate post-thawing. The effects of freeze-thaw on soil N transformation were related to soil biological processes and the relatively constant available P was ascribed to severe soil aridity.     

Vegetation community and soil characteristics of abandoned agricultural land and pine plantation in the Qinling Mountains,China

In order to determine the changes in the characteristics of the vegetation and soil following agricultural abandonment and compare the effects of different restoration approaches on ecosystem recovery, we studied the vegetation community and soil characteristics (nutrients, bulk density, water content and pH) of Pinus tabulaeformis plantations and abandoned croplands in different successional stages in the Foping National Nature Reserve, located in the Qinling Mountains, northwest China. The results indicated that natural vegetation and habitat could be restored via natural regeneration. These spontaneous restoration forests were characterized by high diversity, high soil fertility and rich unique species. The soil organic matter, total carbon, total nitrogen, available potassium, community cover, depth of litter, depth of humus and soil water content increased significantly with years after abandonment, while the total potassium, total phosphorus, available phosphorus, soil pH did not seem to change significantly with abandonment time. The soil mineral nitrogen (NH₄-N + NO₃-N) tended to increase during the first 50 years after abandonment and then decreased. The pine plantations tended to show a low level of biodiversity in tree and herb layer, but the shrub layer (including sapling) composition and diversity were similar to secondary forests. Although the pine plantation showed lower soil fertility, they did not seem to result in the habitat-degradation.     

Composition and mineralization of soil organic carbon pools in four single-tree species forest soils

Forest soil carbon(C) is an important component of the global C cycle. However, the mechanism by which tree species influence soil organic C(SOC) pool composition and mineralization is poorly understood. To understand the effect of tree species on soil C cycling, we assessed total, labile, and recalcitrant SOC pools, SOC chemical composition by ~(13) C nuclear magnetic resonance spectroscopy, and SOC mineralization in four monoculture plantations. Labile and recalcitrant SOC pools in surface(0–10 cm) and deep(40–60 cm) soils in the four forests contained similar content. In contrast, these SOC pools exhibited differences in the subsurface soil(from 10 to20 cm and from 20 to 40 cm). The alkyl C and O-alkyl C intensities of SOC were higher in Schima superba and Michelia macclurei forests than in Cunninghamia lanceolata and Pinus massoniana forests. In surface soil, S.superba and M. macclurei forests exhibited higher SOC mineralization rates than did P. massoniana and C.lanceolata forests. The slope of the straight line between C_(60) and labile SOC was steeper than that between C_(60) and total SOC. Our results suggest that roots affected the composition of SOC pools. Labile SOC pools also affected SOC mineralization to a greater extent than total SOC pools.     

Feasibility of implementing thinning in even-aged <Emphasis Type="Italic">Larix olgensis</Emphasis> plantations to develop uneven-aged larch–broadleaved mixed forests

Thinning experiments were conducted in larch (Larix olgensis) plantations to assess the feasibility of converting even-aged plantation stands to uneven-aged forests with more complex stand structures. Stands established in 1965 and 1960 were thinned in 2004 (Regime A, for determining the effect of recent thinning on emergence of seedlings) and 1994 (Regime B, for examining the effects of the past thinning on establishments of recruitments), respectively, at two intensities each. Natural regeneration, together with litter depth, canopy openness and vegetation cover, was surveyed in the thinned plots. Results indicated that larch seedlings started to emerge in May, reached a peak in June, decreased from June through September, and then disappeared in October. No larch seedlings exceeded 1 year old in the thinned plots because of the low levels of light and dense litter and vegetation cover. However, there were many naturally regenerated seedlings (5–50 cm in height) and saplings (50–500 cm in height) of broadleaved tree species such as Acer spp., Fraxinus spp., Cornus controversa, Quercus mongolica, and even the climax tree species, Pinus koraiensis, in the thinned plots. The mean density of regenerated seedlings reached 6.7 and 4.5 stems m⁻² in Regimes A and B, respectively, whilst the mean density of regenerated saplings reached 4,595 stems ha⁻¹ in Regime B. These results suggest that it is impractical to turn even-aged larch plantations to uneven-aged larch forests, but it may be feasible to develop uneven-aged larch-broadleaved forests from even-aged larch plantations through thinning.     

Carbon storage in old-growth and second growth fire-dependent western larch (Larix occidentalis Nutt.) forests of the Inland Northwest,USA

There is limited understanding of the carbon (C) storage capacity and overall ecological structure of old-growth forests of western Montana, leaving little ability to evaluate the role of old-growth forests in regional C cycles and ecosystem level C storage capacity. To investigate the difference in C storage between equivalent stands of contrasting age classes and management histories, we surveyed paired old-growth and second growth western larch (Larix occidentalis Nutt)–Douglas-fir (Pseudostuga menziesii var. glauca) stands in northwestern Montana. The specific objectives of this study were to: (1) estimate ecosystem C of old-growth and second growth western larch stands; (2) compare C storage of paired old-growth–second growth stands; and (3) assess differences in ecosystem function and structure between the two age classes, specifically measuring C associated with mineral soil, forest floor, coarse woody debris (CWD), understory, and overstory, as well as overall structure of vegetation. Stands were surveyed using a modified USFS FIA protocol, focusing on ecological components related to soil, forest floor, and overstory C. All downed wood, forest floor, and soil samples were then analyzed for total C and total nitrogen (N). Total ecosystem C in the old-growth forests was significantly greater than that in second growth forests, storing over 3 times the C. Average total mineral soil C was not significantly different in second growth stands compared to old-growth stands; however, total C of the forest floor was significantly greater in old-growth (23.8 Mg ha⁻¹) compared to second growth stands (4.9 Mg ha⁻¹). Overstory and coarse root biomass held the greatest differences in ecosystem C between the two stand types (old-growth, second growth), with nearly 7 times more C in old-growth trees than trees found on second growth stands (144.2 Mg ha⁻¹ vs. 23.8 Mg ha⁻¹). Total CWD on old-growth stands accounted for almost 19 times more C than CWD found in second growth stands. Soil bulk density was also significantly higher on second growth stands some 30+ years after harvest, demonstrating long-term impacts of harvest on soil. Results suggest ecological components specific to old-growth western larch forests, such as coarse root biomass, large amounts of CWD, and a thick forest floor layer are important contributors to long-term C storage within these ecosystems. This, combined with functional implications of contrasts in C distribution and dynamics, suggest that old-growth western larch/Douglas-fir forests are both functionally and structurally distinctive from their second growth counterparts.     

The role of isolated old oak trees in maintaining beetle diversity within larch plantations in the central mountainous region of Japan

Old oak trees (Quercus crispula Blume) that are remnants of former old-growth forests have been isolated singly or as small patches within a matrix of conifer plantations in the central mountainous region of Japan. Fifty-six aerial Malaise traps were deployed around seven isolated oak trees within larch [Larix kaempferi (Lamb.) Carrière] plantations and at seven larch plots within larch plantations. The species richness and composition of beetles (Cerambycidae, Curculionidae, Elateridae, Chrysomelidae, and Lycidae) around the oak trees were compared to those in the larch plantations. Species richness was higher around the oak trees than in the larch plantations, and the species composition differed. A number of saproxylic beetles were characteristic of isolated old oak trees. These results emphasize the importance of isolated old oak trees for maintaining beetle diversity in larch plantations and raise the possibility that further losses of these isolated oak trees could eliminate many individuals and reduce beetle diversity in larch plantations.     

英国西加云杉和落叶松的无性繁殖

本文概述了英国西加云杉和落叶松无性繁殖的历史、研究背景、生产方法、扦插苗的造林表现和大规模应用的发展前景。目前已优化无性繁殖系统的扦插苗生产成本为常规的１／３，且扦插苗不增加造林成本。     

Soil changes induced by Acacia mangium plantation establishment: Comparison with secondary forest and Imperata cylindrica grassland soils in South Sumatra,Indonesia

Acacia plantation establishment might cause soil acidification in strongly weathered soils in the wet tropics because the base cations in the soil are translocated rapidly to plant biomass during Acacia growth. We examined whether soils under an Acacia plantation were acidified, as well as the factors causing soil acidification. We compared soils from 10 stands of 8-year-old Acacia mangium plantations with soils from 10 secondary forests and eight Imperata cylindrica grasslands, which were transformed into Acacia plantations. Soil samples were collected every 5–30 cm in depth, and pH and related soil properties were analyzed. Soil pH was significantly lower in Acacia plantations and secondary forests than in Imperata grasslands at every soil depth. The difference was about 1.0 pH unit at 0–5 cm and 0.5 pH unit at 25–30 cm. A significant positive correlation between pH and base saturation at 0–20 cm depth indicated that the low pH under forest vegetation was associated with exchangeable cation status. Using analysis of covariance (ANCOVA), with clay content as the covariate, exchangeable Ca (Ex-Ca) and Mg (Ex-Mg) stocks were significantly lower in forested areas than in Imperata grasslands at any clay content which was strongly related to exchangeable cation stock. The adjusted average Ex-Ca stock calculated by ANCOVA was 249 kg ha⁻¹ in Acacia plantations, 200 kg ha⁻¹ in secondary forests, and 756 kg ha⁻¹ in Imperata grasslands at 0–30 cm. Based on a comparison of estimated nutrient stocks in biomass and soil among the vegetation types, the translocation of base cations from soil to plant biomass might cause a decrease in exchangeable cations and soil acidification in Acacia plantations.     

Nutrient composition of pill millipede manure of the Western Ghats, India

Nutrient composition of the manure of four pill millipedes (Arthrosphaera dalyi, A. davisoni, A. fumosa and A. magna) inhabiting in semi-evergreen forests and plantations of the Western Ghats of Southwest India was evaluated. The quantity and quality of fecal pellets differed between millipedes and their habitats (forest and plantation). Organic carbon content in manure was lower in plantations than in forests, while nitrogen content was elevated in plantations. The carbon to nitrogen (C/N) ratio of manure was lower in plantations compared to forests. The phosphorus content in manure was elevated in plantations in all except for A. dalyi. Calcium content of manure was increased in plantations than in forests. The contents of magnesium, potassium and phenolics in manure showed varied results. The mass of fecal pellets was correlated only with volume in forests (r=0.882; p < 0.01) and pH in plantations (r=0.616; p < 0.05), while the volume of fecal pellets was correlated with nitrogen content in forests (r=0.751; p < 0.01) and calcium in plantations (r=?0.619; p < 0.05). The conductivity was positively correlated with phosphorus and potassium, while magnesium was negatively correlated in forests as well as plantations. Potassium and magnesium were negatively correlated in forests (r=?0.920; p < 0.001) and plantations (r=0.692; p < 0.05). Overall, the physicochemical characteristics and nutrient composition of fecal pelets differed between millipedes as well as habitats. The low carbon to nitrogen ratio and the increased nitrogen, phosphorus and calcium content in the manure of millipedes inhabiting in plantations indicates possibilities for successfully employing them for in situ composting of forest or plantation residues.     

The effects of forest type on soil microbial activity in Changbai Mountain,Northeast China

Key message

Forty years after clear-cutting mixed old-growth forest (broadleaf/Korean pine) in the Changbai Mountain area (Northeast China), a mixed forest with natural broadleaf regeneration and larch plantation displayed larger microbial biomass and activity in the soil than either a naturally regenerated birch forest or a monospecific spruce plantation.

Context

Clear-cutting with limited restoration effort was until the end of the twentieth century the norm for managing primary forests in Northeast China. Forest restoration plays an important role in the recovery of soil quality after clear-cutting, but the effects of different regeneration procedures on forest soil quality remain poorly known in Northeast China.

Aims

We assessed the effects of three regeneration procedures, i.e., (i) naturally regenerated birch forest, (ii) spruce plantation, and (iii) naturally regenerated broadleaf species interspersed with planted larch on soil quality and microbial activity in the Changbai Mountain area. An old-growth mixed broadleaf/Korean pine forest was used as a reference.

Methods

Physical and chemical properties and microbial biomass were recorded in the soil. Basal respiration and carbon mineralization were measured with a closed-jar alkali-absorption method.

Results

Microbial biomass was smaller in the birch forest and spruce plantation than in the old-growth and the mixed broadleaf/larch forests. Moreover, microbial biomass, microbial quotient, and potentially mineralizable carbon were larger in the mixed broadleaf/larch than in the birch forest, while no difference was found between spruce plantation and birch forest for microbial biomass and microbial quotient. Basal respiration and metabolic quotient were larger in the birch forest as compared to the three other forest types, indicating a larger energy need for maintenance of the microbial community and lower microbial activity in the naturally regenerated birch forest.

Conclusion

Mixed broadleaf/larch forest displayed a larger microbial biomass and higher substrate use efficiency of the soil microbial community than either naturally regenerated birch forest or spruce plantation. The combined natural and artificial regeneration procedure (mixed broadleaf-larch forest) seems better suited to restore soil quality after clear-cutting in the Changbai Mountain.

     

杉木纯林、混交林土壤微生物特性和土壤养分的比较研究

本文于2005年5月份,在中国科学院会同森林生态实验站选择了一块15年生的杉木纯林和两块15年生杉阔混交林作为研究对象,调查了林地土壤有机碳、全氮、全磷、硝态氮、有效磷和土壤微生物碳、氮、磷、基础呼吸以及呼吸熵,比较了纯林和混交林土壤微生物特性和土壤养分.结果表明,杉阔混交林的土壤有机碳、全氮、全磷硝态氮和有效磷含量高于杉木纯林;在混交林中,土壤微生物学特性得到改善.在0(10 cm和10(20 cm两层土壤中,杉阔混交林土壤微生物氮含量分别比杉木纯林高69%和61%.在0(10 cm土层,杉阔混交林土壤微生物碳、磷和基础呼吸分别比杉木纯林高11%、14%和4%;在10(20 cm土层,分别高6%、3%和3%.但是,杉阔混交林土壤微生物碳:氮比和呼吸熵较杉木纯林低34%和4%.另外,土壤微生物与土壤养分的相关性高于土壤呼吸、微生物碳:氮比和呼吸熵与土壤养分的相关性.由此可知,在针叶纯林中引入阔叶树后,土壤肥力得以改善,并有利于退化森林土壤的恢复.