Mineral Soil Layers Research Articles

Forest harvesting reduces the soil metagenomic potential for biomass decomposition.

Soil is the key resource that must be managed to ensure sustainable forest productivity. Soil microbial communities mediate numerous essential ecosystem functions, and recent studies show that forest harvesting alters soil community composition. From a long-term soil productivity study site in a temperate coniferous forest in British Columbia, 21 forest soil shotgun metagenomes were generated, totaling 187 Gb. A method to analyze unassembled metagenome reads from the complex community was optimized and validated. The subsequent metagenome analysis revealed that, 12 years after forest harvesting, there were 16% and 8% reductions in relative abundances of biomass decomposition genes in the organic and mineral soil layers, respectively. Organic and mineral soil layers differed markedly in genetic potential for biomass degradation, with the organic layer having greater potential and being more strongly affected by harvesting. Gene families were disproportionately affected, and we identified 41 gene families consistently affected by harvesting, including families involved in lignin, cellulose, hemicellulose and pectin degradation. The results strongly suggest that harvesting profoundly altered below-ground cycling of carbon and other nutrients at this site, with potentially important consequences for forest regeneration. Thus, it is important to determine whether these changes foreshadow long-term changes in forest productivity or resilience and whether these changes are broadly characteristic of harvested forests.

Soil disturbance and early vegetation response to varying intensity of energy wood harvest

Forest biomass plays an important role in the production of renewable energy, particularly in northern Europe. During recent decades, tree stumps have also been increasingly used for energy production. The environmental impacts of stump removal on the functioning of forest ecosystems, for example on soil processes and biodiversity, are still inadequately understood. To investigate the separate impacts of tree stump and logging residue removal on soil and plant variables, we conducted a large-scale replicated experiment in clear-felled stands in three geographical areas. Four energy wood harvesting levels were combined with patch mounding (organic and mineral soil layer turned upside down) as a site preparation method. The harvesting treatments were: (1) no energy wood harvesting, (2) 70% logging residue removal, (3) 25 stumps per hectare left at site and 70% logging residue removal (maximum level in official recommendations), (4) complete stump and 100% logging residue removal. Soil disturbance in terms of mineral and organic soil cover increased with the increasing harvesting level, but complete stump removal did not increase the mineral soil cover more than partial stump removal (on average 95% removed). Despite the increase in soil disturbance, stump removal did not have an overall impact on plant species richness or vegetation composition in the second growing season after harvesting. However, an increasing trend in Betula spp. biomass with increasing harvesting intensity was seen in two of three study areas in four years. Our results underscored the high site-dependency of the effects of stump removal on ecological variables, thus the initial stand structure and vegetation type need to be considered when planning harvesting treatments.

Soil microbial community resilience with tree thinning in a 40-year-old experimental ponderosa pine forest

Establishment of native grasses is a primary objective of restoration in Pinus ponderosa var. scopulorum (P. & C. Lawson) forests in the southwestern United States. Interactions among native grasses and soil microorganisms generate feedbacks that influence the achievement of this objective. We examined soil chemical properties and communities of plants and soil microorganisms in clear-cuts and P. ponderosa stands thinned and maintained at low and medium tree densities for over 40 years along with high density (unthinned) stands. Phospholipid fatty acids (PLFA) in soils were analyzed to examine arbuscular mycorrhizal (AM) fungi and microbial communities in the three thinning treatments and the unthinned stands with and without a recent broadcast burn. Additionally, two native bunchgrasses, Festuca arizonica and Muhlenbergia wrightii were grown in containers filled with intact soil cores collected from each field plot to more thoroughly compare the abundance of AM fungi and microbial communities across different stand densities and burn treatments. Tree thinning decreased litter cover and increased the abundance and diversity and altered community composition of both herbaceous vegetation and AM fungi. In the mineral soil layer, the pH, total carbon, nitrogen, phosphorus and PLFA profiles did not differ significantly among the four stand density or burn treatments. Mycorrhizal colonization of the container grown grasses did not significantly differ with tree density or burn treatments; however, F. arizonica roots had a strong trend for decreased colonization when grown in soil from high density (unthinned) tree cover. Soil from the containers with F. arizonica had a greater abundance of AM fungal spores. Furthermore, bacterial community composition varied with grass species. Concentration of biomarkers for bacteria were higher in soil that supported F. arizonica compared to soil in which M. wrightii was grown. Our results indicate that the creation of clear-cut openings in forests may increase the abundance and richness of AM fungal propagules and soil bacterial communities were surprisingly resilient to tree thinning and low-intensity fire treatments. These results suggest managing forests to create clear-cut openings generate conditions that favor understory native grasses and AM fungi that are linked to soil bacterial communities.

Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils

Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to mor. Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints.

Do soil fauna really hasten litter decomposition? A meta-analysis of enclosure studies

We present a meta-analysis of experiments in which researchers used litter bags or similar enclosures to explore three questions: Do soil macrofauna increase the removal of litter from the soil surface? How is this mass loss of litter by macrofauna affected by climate and litter quality? To what extent does litter loss from litter layer by macrofauna correspond with litter mineralization? In total, we found 132 published field experiments in which authors compared litter bags with mesh sizes that did permit or not permit access by soil fauna. Meta-analysis of these experiments indicated that litter removal was significantly greater from bags that did permitted rather than did not permitted soil macrofauna access. When we divided these studies according to climate, a significant positive effect of soil fauna on litter removal was only evident from the warm humid, temperate regions with correspond to deciduous forest zone. When studies from this climate zone were sorted according to litter C:N ratio, the effect of fauna was significant in all cases except when the ratio was low (<20), and the effect of fauna was greatest when the ratio was intermediate (20–30). To assess how litter removal from litter bags corresponds with mineralization, we reviewed 11 published experiments that used litter boxes that were or were not accessible to soil macrofauna and 8 studies where fauna was experimentally removed and added. These boxes contained both litter and a mineral soil layer, which allowed researchers to estimate litter removal from the litter layer, the increase in C content (C sequestration) in the mineral soil, and overall C mineralization (difference of the former and the latter number). Analysis of these experiments indicated that fauna significantly increased litter removal from the litter layer, which agreed with the litter bag meta-analysis, but did not significantly affect overall C mineralization. This is consistent with meta-analysis of seven studies showing that rate of leaf litter decomposition is significantly faster than decomposition of macrofauna feces produced from the same litter.

Tillage effects on quality of organic and mineral soils under on-farm conditions in Ohio

Assessment of management-induced changes in soil quality is important for sustaining crop yield. The purpose of conducting on-farm field research is to come up with fact-based answers to farming’s challenging questions and this type of research targets “real-world” data. However, research information on impacts of tillage on organic (muck) soils is scanty, and underlying processes of management-induced changes in soil characteristics are poorly understood. In addition, data are scarce on impacts of immediate short-term tillage on historically no-tilled mineral soils. Thus, the objectives of this research are to evaluate impacts of (1) long-term conventional tillage (CT) on organic or muck (Mc) soil compared to non-cropped no-till (NT) condition and (2) short-term CT on mineral (CrB) soil, which has been under NT management under corn. All monitored soil properties were significantly affected by soil type. Compared to CrB, Mc had 6.4 and 5 times higher soil organic carbon (SOC) and nitrogen (N) concentrations, respectively for all sampling depths. Long-term tillage had no impact on Mc probably due to its porous nature, weak structure and high organic matter content. In the mineral soil, short-term CT significantly affected bulk density (BD), water-stable aggregates (WSA), and available water capacity (AWC), especially, in the surface (0–10 cm) layer. The BD was reduced by CT for CrB by up to 14 % (NT 1.6 Mg m−3), compared to NT. Residue incorporation in the plow layer under CT (~20 cm) may have increased aggregation by up to 19 % (70–83 %) and SOC by up to 15 % (2–2.3 %) in CrB compared with that under NT (total aggregation 70 %, SOC 2 %). The data of this study demonstrate that (1) selected muck soil had significantly improved soil properties (higher WSA, AWC, SOC and N, and lower BD and penetration resistance) than those of the studied mineral soil, (2) long-term tillage did not affect the properties of the native muck soil, and (3) surface layer of the long-term no-tilled mineral soil was significantly affected by introduction of only 1 year of CT management.

Sorption processes of radiocesium in soil and bedrock

Abstract Three recent studies on cesium sorption in soil and bedrock are reviewed. 137Cs, originating from fallouts of nuclear weapons tests and the Chernobyl accident was found to decrease in an exponential manner in forest soil, and the highest fraction in soil profiles was found in the organic layer. Also, the mineral layer below the organic layer contained a large fraction of cesium inventory but at depths below 20 cm only a very small fraction was observed. In the bedrock of Olkiluoto, where the final repository for spent nuclear fuel from the Finnish nuclear power plants will be constructed, mica mineral biotite plays the most important role in cesium sorption. The selectivity of biotite decreases in the order Cs &gt; K &gt; Na &gt; Ca and the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange reactions, respectively. Ion exchange isotherms for Cs/Na and Cs/K exchange were modelled by assuming three different ion exchange sites: frayed edge sites (FES), basal plane sites and intermediate sites. The selectivity coefficients derived for these sites were successfully used to predict cesium sorption in a mica gneiss rock. Sorption of cesium in mineral soil layers from the Olkiluoto overburden were studied using three different approaches: model batch experiments, an in-situ method and calculations. All three approaches gave the same trend but the distribution coefficient values varied in range of one order of magnitude.

川西亚高山森林林窗不同时期土壤转化酶和脲酶活性的特征

As an important small scale disturbance,forest gaps are often considered to be major drivers in the natural forest regeneration. Moreover,forest gaps can play essential roles in soil processes including the dynamics of soil enzyme activity,since the snow,precipitation and sunshine duration could be redistributed in different gap location due to the effects of forest canopy. Subalpine forest in western Sichuan is a typical cold biome,which often displays sensitive responses to environment disturbance because of its fragile characters. As yet,more and more recent studies have concentrated on gap characteristics and seedling regeneration processes in this area,but little attention has been given to the effects of forest gap on soil enzyme activity. As we know,soil invertase and urease are the key enzymes involved in the soil organic carbon and nitrogen transformation,respectively,and the changes of their activities are closely associated with the carbon and nitrogen cycling. Therefore,to understand the effects of forest gap on soil invertase and urease activities at different seasons in alpine forest,a field experiment was conducted in a Picea asperata plantation forest in western Sichuan. The dynamics of soil invertase and urease activity under gap center,gap edge and under-canopy were investigated from June 2012 to May 2013.Soil samples in soil organic layer and mineral soil layer were collected in growing season( completely soil thawing stage,early stage and later stage of growing season) and freeze-thaw season( onset stage of freezing,deeply soil freezing stage and soil thawing stage). The results showed that soil invertase activity in soil organic layer was higher than that in mineral soil layer regardless of forest gap location. Soil invertase activity during the growing season in both soil organic layer and mineral soil layer showed the order: gap center under-canopy gap edge,but soil urease activity showed the order: gap center gap edge under-canopy. In comparison with gap edge and under-canopy,gap center exhibited higher soil invertase activity at onset stage of freezing and deeply soil freezing stage,while soil invertase activity in under-canopy was higher than that of gap center and gap edge at soil thawing stage. In addition,soil urease activity at onset stage of freezing and soil thawing stage was significantly higher in under-canopy than that in gap center and gap edge,although which at deeply soil freezing stage showed few differences in different gap locations. The results here imply that gap location has a profound impact on soil invertase and urease activities at different seasons in subalpine forest.

哀牢山亚热带常绿阔叶林森林土壤温湿特征及其对温度升高的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 哀牢山亚热带常绿阔叶林森林土壤温湿特征及其对温度升高的响应 DOI: 10.5846/stxb201403260562 作者: 作者单位: 中国科学院热带森林生态学重点实验室,中国科学院哀牢山生态站;中国科学院哀牢山生态站,日本国立环境研究所,日本,筑波,-,;日本国立环境研究所,日本,筑波,-,中国科学院热带森林生态学重点实验室,中国科学院哀牢山生态站;中国科学院哀牢山生态站,中国科学院热带森林生态学重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 云南省自然科学基金重点项目(2011FA025);国家基金-云南省联合项目(U1202234); 国家基金重大项目(31290220); 中国科学院战略性专项项目(XDA05050601, XDA05050206) Responses of soil temperature, moisture and respiration to experimental warming in a subtropical evergreen broad-leaved forest in Ailao Mountains, Yunnan Author: Affiliation: Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为把握土壤温度对未来全球气候变暖的响应程度,评估气候变暖对亚热带森林土壤呼吸的影响,利用在哀牢山亚热带常绿阔叶林中设置的土壤增温和土壤呼吸人工控制实验2011-2013年的实测数据,通过分析,得到如下结果:环境温度的升高不会改变林内的近地层气温、土壤温度和土壤含水量的年变化和日变化规律;冬季和夜间增温效应大于夏季和昼间;增温会导致土壤含水量降低,雨季的效应大于干季;增温导致的升温效应和降低土壤水分效应具有一定的年变化,但是基本没有日变化;所设置的人工增温控制实验的年平均增温在2.0 ℃左右,所设置人工控制实验可以达到5 cm土壤增温2.0 ℃的设计要求,可为其后探讨土壤呼吸对温度升高的响应提供良好的基础保证. Abstract:The soil-surface carbon flux is comparable to that of photosynthesis in terrestrial ecosystems. Much soil carbon flux to the atmosphere is due to rhizosphere metabolism (root respiration) and the decomposition of soil microbes (microbial respiration), which are both very sensitive to temperature. With soil temperatures increasing, soil respiration will increase, thereby accelerating global change. To improve our understanding of the response of soil temperature to future warming and to assess the potential effects of global warming on soil respiration in subtropical forests, we experimentally warmed subtropical evergreen broad-leaved forest soils in Ailao Mountain Southwest, China and measured their respiration. This experiment was conducted at the Ailaoshan Station for Subtropical Forest Ecosystem Studies (24°32'N, 101°01'E; 2480 m above sea level) of the Chinese Ecological Research Network, Jingdong County, Yunnan Province. The annual mean air temperature was 11.0℃, with a maximum monthly mean temperature of 15.3℃ in July and a minimum monthly mean temperature of 5.1℃ in January. The site has strong rainy seasons (May to October) and dry seasons (November to April the following year). The average annual rainfall was 1882 mm, with 1607 mm (85.4% of the annual total) in the rainy season and 274.2 mm in the dry season (14.6% of the annual total). The soil is yellow brown in this area. Litterfall accumulates to 3-7 cm. Soil humus is dark brown and 10-15 cm thick. The mineral soil layer is loose and dominated by soil aggregates. Surface soils have high water permeability and water conservation ability, high organic carbon, and a pH of 4.5-5. Our artificial warming experiment was conducted in a subtropical forest where wind speed and radiation are both low at the surface. A multi-channel automated chamber system was used to continuously monitor soil CO2 effluxes. The system was comprised of 20 automatic chambers (length 90 cm × width 90 cm × height 50 cm) and a control box, and the 20 chambers were divided into 4 treatments (5 chambers per treatment): control, litter removal, trenching, and infrared light warming. The soil efflux of each chamber was measured automatically each hour and environmental factors were measured each half hour. When measuring soil efflux, the chamber was closed for 3 min, then opened for 57 min by opening its lid. Thus, environmental conditions (e.g., wind, rainfall, and litterfall) in chambers were similar to those outside. In the artificial warming experiment, variations in soil temperature and soil water content were observed along with soil respiration. Based on measurements from 2011 to 2013, we concluded that warming did not change the seasonal and diurnal patterns of air temperature near the soil surface, soil temperature, or soil water content of the forest. The warming effects in winter and nighttime were greater than in summer and daytime. Warming decreased soil water content to a larger extent in the rainy season than in the dry season. The temperature increase and soil water decrease resulting from warming had seasonal variations, but not diurnal variations. The experimental warming increased the annual soil temperature by about 2℃; therefore, the warming treatment reached the goal of increasing soil temperature at 5 cm by 2℃. Our infrared warming method achieved a relatively stable warming effect without time lags in soil-temperature variations in the primary subtropical evergreen broad-leaved forest in Ailao Mountain. In this subtropical evergreen broad-leaved forest, soil temperature has previously shown a significant warming trend, so this study can supply information about soil respiration responses. This study also showed that variation in local air temperature, soil temperature, and soil-water content will not change under global warming, but soil-water content will decline with increased temperature, especially in the rainy season. In the forest, soil respiration is affected not only by soil temperature, but also by soil water content. As warming decreases soil water content, the effects of soil water content variation on soil respiration should be examined in future research. 参考文献 相似文献 引证文献

六盘山四种森林生态系统的碳氮储量及组成与分布特征

Carbon( C) and nitrogen( N) are important elements of forest ecosystems,and quantifying C and N storage and distribution is a critical step for better understanding of C and N cycles in forest ecosystems. C and N pools in forests vary greatly,depending on the forest type,forest growth stage,and site quality. The mechanisms controlling the spatial and temporal variation of C and N accumulation in forest ecosystems, especially in the northwestern China, have been sporadically investigated in the past. In this paper,the content,storage and distribution of C and N were investigated infour typical forests at the Liupan Mountains in Ningxia,northwestern China. The four forest types included Larix principisrupprechtii plantation,Pinus armandii secondary forest,Betula platyphylla secondary forest,and Prunus salicina shrubs.The concentrations of C and N were measured in different organs of the trees,and the contents of C and N in the vegetation layers of trees,shrubs,grasses,and layers of humus,and soil( 0—100 cm depth) were estimated. Storage,composition,and distribution of C and N in these ecosystems were examined. The results showed that the concentrations of C did not significantly differ among the different organs and tree species, but the concentration of N varied. The highest N concentration was found in the leaves and the lowest in the trunk. The contents of C and N were higher in the above-ground biomass than in the below-ground biomass for both shrubs and grasses. The C contents decreased in the order of tree layer shrub layer grass layer,but N contents increased in the order of tree layer shrub layer grass layer in the studied forests. The C content was lower in the humus layer than in each of the vegetation layers,but the situation was opposite for the N content. The contents of both C and N decreased with increasing soil depth. The total C storage in the four forest ecosystems was in the following order: B. platyphylla secondary forest( 640. 02 t / hm2) P. armandii secondary forest( 450. 98 t /hm2) L. principis-rupprechtii plantation( 364. 56 t /hm2) P. salicina shrub( 196. 55 t /hm2). The total N storage decreased from 47. 02 t / hm2 in B. platyphylla secondary forest to 36. 19 t / hm2 in P. armandii secondary forest,27. 86 t / hm2 in L. principis-rupprechtii plantation and 15. 99 t / hm2 in P. salicina shrub ecosystems in the study sites. The amount of C and N in the soil( 0—100 cm depth) accounted for the major proportion of the total C and N storage in the studied forest ecosystems,with the range of 84. 7% —93. 9% for C and 98. 1% —98. 6% for N for the four forest types. On average,the C / N ratio in the soil and in the entire ecosystem was 12. 48 and 13. 52 in B. platyphylla secondary forest,11.84 and 13. 12 in L. principis-rupprechtii plantation,11. 70 and 12. 29 in P. salicina shrub,and 10. 76 and 12. 56 in P.armandii secondary forest,respectively. In addition,the C / N ratio decreased gradually from the tree layer to shrub layer,grass layer,humus layer,and mineral soil layer. Our study demonstrated that various forest types had different ability for the sequestration and accumulation of C and N in the studied area.

川西亚高山/高山森林土壤养分动态及其对季节性冻融的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 川西亚高山-高山森林土壤养分动态及其对季节性冻融的响应 DOI: 10.5846/stxb201312303063 作者: 作者单位: 四川农业大学,四川农业大学;绵阳师范学院,四川农业大学,四川农业大学 作者简介: 通讯作者: 中图分类号: S718.5 基金项目: 国家自然科学基金项目(31170423, 31270498); 国家"十二五"科技支撑计划(2011BAC09B05); 四川省杰出青年学术与技术带头人培育项目(2012JQ0008, 2012JQ0059); 高等学校博士学科点(博导类)专项科研基金(20105103110002)项目 Dynamics of soil nutrients and their response to seasonal freeze-thaw in the subalpine-alpine forests of western Sichuan Author: Affiliation: Key Laboratory of Ecological Forestry Engineering,Institute of Ecology Forestry,Sichuan Agricultural University,Key Laboratory of Ecological Forestry Engineering,Institute of Ecology Forestry,Sichuan Agricultural University;Ecological Security and Protection Key Laboratory of Sichuan Province, Mianyang Normal University,Key Laboratory of Ecological Forestry Engineering,Institute of Ecology Forestry,Sichuan Agricultural University,Key Laboratory of Ecological Forestry Engineering,Institute of Ecology Forestry,Sichuan Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为深入了解川西亚高山-高山森林冬季生态学过程,于2008年11月-2009年10月,在土壤冻结初期、冻结期和融化期及植被生长季节,研究了不同海拔(3582 m、3298 m和3023 m)岷江冷杉林土壤养分动态及其对季节性冻融的响应。3个海拔森林土壤冬季具有较高养分含量,且随土壤冻融过程不断变化。土壤有机层可溶性碳和氮、铵态氮、硝态氮含量在冻结初期显著增加后快速降低,并随融化过程迅速增加后再次降低,而土壤可溶性碳和氮、硝态氮含量在冻结期变化不明显,铵态氮显著增加。矿质土壤层可溶性碳和氮、铵态氮含量也在冻结初期显著增加后降低,而土壤可溶性氮、铵态氮和硝态氮在冻结期显著增加,并在融化期经历一个明显的含量高峰。海拔和土层的交互作用显著影响土壤可溶性碳和硝态氮含量,土壤养分含量与土壤温度的相关性随海拔差异而不同。这表明季节性冻融期是土壤生态过程的重要时期,土壤冻融格局显著影响川西亚高山-高山森林土壤养分动态。 Abstract:Soils in subalpine and alpine ecosystems during winter experience extensive snow cover, freezing, thawing, and freeze-thaw cycle with air temperatures fluctuating above and below 0 ℃. Such conditions have profound repercussions on soil nutrient availability, microbial biomass, and enzyme activity in subalpine and alpine ecosystems during winter, yet systemic studies of these ecosystems are lacking. In order to deeply understand winter ecological processes in the subalpine and alpine forests of western Sichuan, three fir (Abies faxoniana) forests including primary fir forest at 3582 m altitude, fir and birch mixed forest at 3298 m altitude, and secondary fir forest at 3023 m altitude were chosen as study subjects. Soil was collected at different stages: at the onset of the soil freezing period, the soil frozen period, the soil thawing period, and the growing season from November 2008 to October 2009. Concentration of dissolved carbon and nitrogen, NH4+-N, and NO3--N were measured in each soil sample. Compared to the growing season, the content of measured nutrients was relatively high during winter in all sampled forests. Moreover, the dynamics of the measured soil nutrients changed with the processes of the soil freeze-thaw cycle. In the soil organic layer, the amount of dissolved carbon and nitrogen, NH4+-N, and NO3--N significantly increased followed by a decrease in both the onset of the soil freezing period and the soil thawing period, whereas they showed little change in the soil frozen period, except for NH4+-N. In the mineral soil layer, the content of the measured nutrients also significantly increased and then decreased with the onset of the soil freezing period. However, the content of the dissolved nitrogen, NH4+-N, and NO3--N visibly increased in the soil frozen period, reaching a peak in the soil thawing period. Additionally, the interaction of the altitude and soil layer affected the amount of dissolved carbon and NO3--N. Correlation between the concentration of soil nutrients and soil temperature varied with the altitude. The results suggested that the seasonal freeze-thaw period is a crucial stage for ecological processes in the soil, and the soil freeze-thaw pattern significantly affects the dynamics of soil nutrients in the subalpine and alpine forests of western Sichuan. 参考文献 相似文献 引证文献

Quantitative assessment of the effect of recreation on vegetation, forest litter, and soil compactness in forest parks of Moscow

The quantitative characteristics of vegetation, forest litter, and soil status at different stages of recreation digression are discussed by the example of the Losinyi Ostrov and the Bittsevskii Les forest parks (Moscow). Plant cover is most sensitive to recreation impact: successions of its parameters are already seen at transition to stage II of ecosystem digression. Forest litter type is changed at stages III and IV, and a statistically significant drop in its reserves occurs at stage V. The compactness of the top mineral soil layer increases statistically by 0.24–0.28 g/cm3 at rather high recreation impact at stages IV and V.

Long term changes in soil properties and enzyme activities after almond shell mulching in avocado organic production

The recycling of almond shell as mulch would allow avocado orchards to be managed organically, maintaining plant yield and improving soil conditions simultaneously. This study aims to analyze the long term effects of successive applications of almond shell as mulching for organically grown avocado. Effects on soil properties, enzyme activities and soil carbon storage as well as avocado yield and growth were studied in comparison to no-tillage conventionally managed (using mineral fertilizers and herbicides) avocado. In 2002, 2007 and 2012 almond shells were applied in a 7cm thick layer (26.0kg dry matterm−2) covering 4m×8m per tree. After a 10-year period a new soil organic horizon was established in the organic treatment, and the upper mineral soil layer (0–25cm) enhanced its C content from 43gkg−1 in F to 91 in gkg−1, and proportionally P and N contents. The high lignin content of almond shells, 362gkg−1, led to low organic matter degradation, 37% for the 10-year period. Nevertheless, this reduced rate of organic matter mineralization was sufficient to supply the needed nutrients and to maintain or even increase fruit yield in the organic treatment. Urease, β-glucosidase, dehydrogenase, protease and phophomonoesterase showed high microbiological activity in the organic layer decreasing in mineral layers. Enzyme activities were significantly correlated to soil OC (organic C) content and site specific soil moisture. Reduced mineralization and high surface microbiological activity make almond shell an ideal mulch for avocado trees combining increased soil organic C content and agricultural benefits.

Vertical migration of radiocesium and clay mineral composition in five forest soils contaminated by the Fukushima nuclear accident

In forest soils contaminated by radiocesium (134Cs and 137Cs), deposition from the Fukushima nuclear accident, clay minerals might play important roles in long-term cesium (Cs) dynamics through sorption. To determine whether radiocesium can be retained within the organic layer and the upper mineral soil layers in the Fukushima region, we investigated the vertical distribution of 134Cs and 137Cs and the clay mineral composition in five soil profiles of varying radiocesium deposition levels and vegetation types. X-ray diffraction analyses and oxalate extraction suggested that hydroxy-interlayered vermiculites and short-range-ordered aluminum (Al) and iron (Fe) compounds (i.e, allophane and ferrihydrite) were major clay mineral species of the upper soil layers. The vertical soil distribution of 134Cs and 137Cs suggested that most of them were retained in the organic layer and upper mineral soil layer under different levels of deposition. Within 1.5 years after the accident, both 134Cs and 137Cs were leached from the organic layer, and most of these (59–73%) were accumulated in the upper soil layer (0–5 cm). The proportion of 137Cs (or 134Cs) leaching from the organic layer was greater at sites receiving greater amounts of precipitation. The substantial accumulation of 137Cs in the upper soil layer, irrespective of the 137Cs deposition level or clay mineral composition, suggests that sorption capacities of clays and organic matter are sufficiently high to retain 137Cs in the surface soil during at least the initial stage of contamination.

Changes in soil organic carbon and nitrogen following forest expansion on grassland in the Southern Alps

The dominant land-use change in the Southern Alps is grassland abandonment, followed by forest expansion. Forest expansion is commonly thought to increase ecosystem C sequestration, but contradictory results have been reported. Our objective was to investigate soil organic carbon (SOC) and nitrogen (N) changes after forest expansion on abandoned grasslands. A land use and management gradient was identified in a subalpine area of Trentino (Italy) comprising four successional stages: (i) managed grassland (manG), mown and manured annually for more than 100years; (ii) grassland abandoned 10years ago (abanG), with shrubs and Picea abies saplings; (iii) early-stage forest (earlyF), dominated by P. abies established on grassland abandoned around 1970; and (iv) old forest (oldF), dominated by Fagus sylvatica and P. abies, representing a reference for long-term forest land use. Organic and mineral soil layers were collected down to 30cm at eight points within three plots for each successional stage.Significantly more SOC was stored in organic layers of oldF compared with other successional stages and the organic layer N stocks were higher in oldF compared with manG and abanG. The SOC and N concentrations were higher in the top 10cm mineral soil of grassland plots compared with forest. The earlyF and oldF stored, on average, 28–35% less SOC in top 10cm mineral soil compared with manG and abanG when stocks were calculated using equivalent soil mass (ESM) and equivalent soil depth (ESD) approaches respectively. SOC stocks in mineral soil (0–30cm) calculated with ESD decreased from manG to oldF; when accounting for total stone content, SOC stocks in earlyF and oldF were 40% and 50% lower than in manG, respectively. The inclusion of organic layers offset mineral SOC stock differences when only stones <5cm were accounted for, but when considering the total stone content, SOC stocks in earlyF remained significantly lower (−31%) than in manG. Tree biomass contributed to higher ecosystem C stocks in oldF, which stored 82–93Mgha−1 of C more than grasslands.Our study revealed a decrease in total SOC stocks after forest expansion on abandoned subalpine grasslands. Tree biomass development contributed to increasing C storage, especially in a long-term forest land use. Forest management should consider that tree biomass and organic layer development require a minimum time period following grassland abandonment to compensate for the decrease in mineral SOC stocks and contribute positively to climate change mitigation.

Long-term effects of liming on health and growth of a Masson pine stand damaged by soil acidification in Chongqing, China.

In the last decades, the Masson pine (Pinus massoniana) forests in Chongqing, southwest China, have increasingly declined. Soil acidification was believed to be an important cause. Liming is widely used as a measure to alleviate soil acidification and its damage to trees, but little is known about long-term effects of liming on the health and growth of declining Masson pine forests. Soil chemical properties, health condition (defoliation and discoloration), and growth were evaluated following application of limestone powder (0 (unlimed control), 1, 2, 3, and 4 t ha−1) in an acidified and declining Masson pine stand at Tieshanping (TSP) of Chongqing. Eight years after liming, in the 0–20 cm and 20–40 cm mineral soil layers, soil pH values, exchangeable calcium (Ca) contents, and Ca/Al molar ratios increased, but exchangeable aluminum (Al) levels decreased, and as a result, length densities of living fine roots of Masson pine increased, with increasing dose. Mean crown defoliation of Masson pines (dominant, codominant and subdominant pines, according to Kraft classes 1–3) decreased with increasing dose, and it linearly decreased with length densities of living fine roots. However, Masson pines (Kraft classes 1–3) in all treatments showed no symptoms of discoloration. Mean current-year twig length, twig dry weight, needle number per twig, needle length per twig, and needle dry weight per twig increased with increasing dose. Over 8 years, mean height increment of Masson pines (Kraft classes 1–3) increased from 5.5 m in the control to 5.8, 6.9, 8.3, and 9.5 m in the 1, 2, 3, and 4 t ha−1 lime treatments, and their mean DBH (diameter at breast height) increment increased from 3.1 to 3.2, 3.8, 4.9, and 6.2 cm, respectively. The values of all aboveground growth parameters linearly increased with length densities of living fine roots. Our results show that liming improved tree health and growth, and these effects increased with increasing dose.

Conversion of cropland to forest increases soil CH4 oxidation and abundance of CH4 oxidizing bacteria with stand age

We investigated CH4 oxidation in afforested soils over a 200-year chronosequence in Denmark including different tree species (Norway spruce, oak and larch) and ages. Samples of the top mineral soil (0–5cm and 5–15cm depth) were incubated and analyzed for the abundance of the soil methane-oxidizing bacteria (MOB) and ammonia-oxidizing bacteria (AOB) and archaea (AOA) based on quantitative PCR (qPCR) on pmoA and amoA genes. Our study showed that CH4 oxidation rates and the abundance of MOB increased simultaneously with time since afforestation, suggesting that the methanotrophic activity is reflected in the abundance of this functional group.The development of forest soils resulted in increased soil organic carbon and reduced bulk density, and these were the two variables that most strongly related to CH4 oxidation rates in the forest soils. For the top mineral soil layer (0–5cm) CH4 oxidation rates did not differ between even aged stands from oak and larch, and were significantly smaller under Norway spruce. Compared to the other tree species Norway spruce caused a decrease in the abundance of MOB over time that could explain the decreased oxidation rates. However, the cause for the lower abundance remains unclear. The abundance of ammonia-oxidizers along the chronosequence decreased over time, oppositely to the MOB. However, our study did not indicate a direct link between CH4 oxidation rates and ammonia-oxidizers. Here, we provide evidence for a positive impact of afforestation of former cropland on CH4 oxidation capacity in soils most likely caused by an increased population size and activity of MOB.

Transformation of microbial cenoses in soils of light coniferous forests caused by cuttings and fires in the Lower Angara River basin

The influence of surface fires and cutting on the quantitative and functional parameters of microbial cenoses in the soils of light coniferous forests in the Lower Angara River basin was studied. In the litters of soddy-podzolic soils under pine forests, the microbial biomass was 4080–4700 μg C/g; the basal respiration was 17.00–20.32 μg C-CO2/g/h; and the qCO2, 4.17–4.33 μg C-CO2/mg Cmic/h. In the humus-accumulative horizon, these values were 880–1160 μg C/g, 2.48–4.12 μg C-CO2/g/h, and 2.83–3.55 C-CO2/mg Cmic/h, respectively. In the litter of the one-year-old felled area, the content of microbial biomass carbon was by two times lower; in the litter of burned plots, it was by 60–70% lower than in the litter of the control area. The intensity of the microbial respiration did not change proportionally to the microbial biomass content, which resulted in an imbalance between the processes of the organic matter mineralization-immobilization towards a release of CO2 as evidenced by the increase of the qCO2 values by 2–4 times. In the five-year-old felled area, at the stage of restoring the herbaceous vegetation, a tendency towards the stabilization of the destructive microbiological processes was revealed. In the felled areas, the high number of heterotrophic microorganisms, the reduced oligotrophy of the soil organic horizons, and the more intense microbiological mineralization of the organic matter were observed. The surface fires in the felled areas and forests significantly affected the structure and the number of ecological-trophic groups of microorganisms in the litters, the humus-accumulative horizons, and in the upper mineral soil layers. The maximal structural and functional disturbance in the soil microbial complex was found in the logged areas affected by fires.

Components of Soil Respiration and its Monthly Dynamics in Rubber Plantation Ecosystems

Aim: Our objective was to quantify four components and study effect factors of soil respiration in rubber plantation ecosystems. Providing the basic data support for the establishment of the trade of rubber plantation ecosystem carbon source/sink. Methods: We used Li-6400 (IRGA, Li-COR) to quantitate four components of soil respiration in rubber plantation ecosystems at different ages. Soil respiration can be separated as four components: heterotrophic respiration (Rh), Respiration of roots (Rr), respiration of litter layer (Rl) and respiration of mineral soil (Rm). Important findings: The soil respiration rate (Rs) showed significant seasonal variation. The maximum soil respiration rate of the whole year appeared in August and the minimum in November or December. The components of soil respiration rate order showed as: heterotrophic respiration>respiration of roots>respiration of litter layer> respiration of mineral soil. The soil respiration rate was highly significant correlation (p<0.01, Q₁₀ = 1.13~2.37) with 0~10 cm soil temperature in dry season and significant correlation (p<0.05, Q₁₀ = 1.10~1.77) with 0~10 cm soil temperature in wet season. And soil respiration rate was not significant correlation with soil water content of 5 cm (p≥0.05). The soil respiration components of four kinds forest ages accounted for the percentage contribution to the flux of annual carbon emissions (Rs) as: Rh: 35.28~52.75%, Rr: 21.73~39.97%, Rl: 17.13~19.63%, Rm: 6.605~10.27%%, respectively. The soil respiration rate carbon flux of 5, 10, 19 and 33a respectively were 10.03, 10.34, 11.96 and 11.09 t/hm².a. And the annual carbon flux of soil respiration increased with stand ages increasing in rubber plantation ecosystems.

Fate and Transport of Ambient Mercury and Applied Mercury Isotope in Terrestrial Upland Soils: Insights from the METAALICUS Watershed

The fate of mercury (Hg) deposited on forested upland soils depends on a wide array of biogeochemical and hydrological processes occurring in the soil landscape. In this study, Hg in soil, soilwater, and streamwater were measured across a forested upland subcatchment of the METAALICUS watershed in northwestern Ontario, Canada, where a stable Hg isotope (spike Hg) was applied to distinguish newly deposited Hg from Hg already resident in the watershed (ambient Hg). In total, we were able to account for 45% of the total mass of spike Hg applied to the subcatchment during the entire loading phase of the experiment, with approximately 22% of the total mass applied now residing in the top 15 cm of the mineral soil layer. Decreasing spike Hg/ambient Hg ratios with depth in the soil and soilwater suggest that spike Hg is less mobile than ambient Hg over shorter time scales. However, the transport of spike Hg into the mineral soil layer is enhanced in depressional areas where water table fluctuation is more extreme. While we expect that this pool of Hg is now effectively sequestered in the mineral horizon, future disturbance of the soil profile could remobilize this stored Hg in runoff.