Low Soil Organic Matter Content Research Articles

Differences in soil organic matter, extractable nutrients, and acidity in European beech (Fagus sylvatica L.) forest soils related to the presence of ground flora

Differences in soil organic matter (SOM) content, soil acidity, and soil exchangeable nutrients (NH4–N, NO3–N, Ca, K, Na, Mg) related to the presence of ground flora were studied. The study was carried out for a growing season in two different Fagus sylvatica L. forests in southern Sweden, and the differences in soil characteristics below naturally occurring patches of Deschampsia flexuosa (L.) Trin. or Anemone nemorosa L. were compared with those with no ground flora. Patches of D. flexuosa led to higher soil pH, but lower SOM, water content, base saturation, and NH4–N concentration compared with adjacent zones without D. flexuosa. The lower SOM content suggested an increased rate of decomposition which caused soil pH to increase because of release of basic cations. In the presence of A. nemorosa, pH was higher and the exchangeable acidity lower than for patches without the herb. In early spring, when A. nemorosa emerged and flowered, the NH4–N concentration was somewhat lower in the presence of the herb than when it was absent. For the evergreen grass D. flexuosa NH4–N concentrations were lower in patches with the grass later in the summer season (July). This work indicates the presence of spatial and temporal differences in nutrient circulation and decomposition on the small ground flora scale, which should be considered when studying nutrient and carbon cycles of temperate forests.

Toluene sorption behavior on soil organic matter and its composition using three typical soils in China

The effect of soil organic matter (SOM) content and composition on sorption behavior of toluene for fluvo-aquic, red and black soils in China was investigated in batch experiments. Tested SOM was fractionated into two primary sorptive domains (‘soft’ and ‘hard’) to explain the dependence of sorption behavior on SOM composition. All the tested soils exhibited similar sorption kinetics and nonlinear sorption isotherms. Soils with high SOM content possessed a high sorptive capacity. Clay minerals also contributed to the sorptive capacity, especially for fluvo-aquic and red soils with low SOM content. In comparison, after removing most ‘soft’ SOM fraction from soils through hydrogen peroxide treatment, the residual ‘hard’ SOM fraction of three soil samples exhibited a slower sorption rate and a less sorption capacity compared to the untreated soil samples. The nonlinear degree of sorption was positively correlated with the content of ‘hard’ SOM for all soil samples. This is explained by the combined effect of SOM content and the composition on toluene sorption rates, sorption capacity and nonlinear degree of sorption of three typical soils in China.

Drying-induced changes in phosphorus status of soils with contrasting soil organic matter contents – Implications for laboratory approaches

Phosphorus (P) fractions are commonly assessed on dried soils in environmental and long-term field research, because this is the most convenient method of storing large quantities of samples before analysis. However sample pre-treatment may seriously affect the results, especially those regarding the organic P fractions. The objective of the present study was to assess the effect of soil drying under laboratory conditions on the P status of soils with contrasting physico-chemical and microbial properties. We used soils from a (Pinus pinaster) forest in southwest France sampled from different soil depths and different site classes featuring a gradient of soil organic matter (SOM), and aluminium (Al) and iron (Fe) oxides. Total P, total organic and inorganic P, water soluble phosphate ions (iP), microbial P and the potentially mineralizable P in ‘dead’ organic matter were determined on fresh, moist soils maintained at 4°C and on the same soils, oven-dried at 60°C. Laboratory-drying resulted in a general decrease in total organic P, which was positively correlated with microbial P and SOM content. These drying-induced changes in total organic P were associated with a concomitant increase in total inorganic P and water soluble iP, which were dramatic in the organic forest floor samples (on average +2965% (×31 increase) in total inorganic P, and +11880% (×123 increase) in water soluble iP). The changes in water soluble iP were correlated with the SOM: Al and Fe oxides ratio and showed little effect of soil drying in deeper soil layers with a low SOM and high oxide contents. Our results indicated that soil drying mainly resulted in the lysis of the microbial pool, and to a much lesser extent, in the physical disruption and mineralization of the SOM. We conclude that soil drying before analyses can generate a significant bias in the evaluation of soil P stocks and fluxes, especially in SOM-rich layers. We recommend that fresh soil samples should be used as far as possible to determine soil P status.

Spatial Distribution of Soil Organic Matter Using Geostatistics: A Key Indicator to Assess Soil Degradation Status in Central Italy

Soil organic matter (SOM) content is one of the main factors to be considered in the evaluation of soil health and fertility. As timing, human and monetary resources often limit the amount of available data, geostatistical techniques provide a valid scientific approach to cope with spatial variability, to interpolate existing data and to predict values at unsampled locations for accurate SOM status survey. Using geostatistical and geographic information system (GIS) approaches, the spatial variability of some physical and chemical soil parameters was investigated under Mediterranean climatic condition in the Abruzzo region of central Italy, where soil erosion processes accelerated by human induced factors are the main causes of soil degradation associated with low SOM content. Experimental semivariograms were established to determine the spatial dependence of the soil variables under investigation. The results of 250 soil sampling point data were interpolated by means of ordinary kriging coupled with a GIS to produce contour maps distribution of soil texture, SOM content related to texture, and C/N ratio. The resulting spatial interpolation of the dataset highlighted a low content of SOM in relation with soil texture in most of the surveyed area (87%) and an optimal C/N ratio for only half of the investigated surface area. Spatial location of degraded area and the assessment of its magnitude can provide decision makers with an accurate support to design appropriate soil conservation strategies and then facilitate a regional planning of agri-environmental measures in the framework of the European Common Agricultural Policy.

Corn response to tillage and water table depth

WITHIN-FIELD VARIATIONS OF MIDWEST CORN YIELDS AND PROBABLE CAUSES Yields in some sections of fields are commonly less than half of those in the best sections, as illustrated in figure 1, which shows corn yields in 2010 measured along two transects across a 10 ha (25 ac) field in Winnebago County, Wisconsin. These large yield differences are surprising because farmers usually use the same seed and rates of fertilizer, manure, and herbicide and the same equipment for tillage and seeding over a whole field. The south side of this field is 1.8 to 3.6 m (6 to 12 ft) lower than the north side, so as is commonly the case, the black topsoil layer is thicker on the south (lower and flatter) side than the north. Since yields tended to be better on the north side of this field, lower soil organic matter content was apparently not a dominant factor causing the lower yields. Installation of piezometers and monitoring of water tables during the following fall, winter, and early spring months showed water tables averaging about 80 cm (31 in) below the surface but rising in April and averaging about 40 cm (16 in) below the soil…

Land-Use Effect on Selected Soil Quality Parameters

Land use is a key factor that affects soil quality. The purpose of the present study was to investigate changes of selected soil chemical properties related to soil function under different land uses. Five experimental sites arranged in a complete randomized blocks located within the Kalloni watershed (Lesvos Island, Greece) corresponding to different land uses (Pinus brutia forest, brushwood pasture, rain-fed olive grove, wheat, and maize) were compared for soil pH, electrical conductivity (EC), total nitrogen (N), nitrate N (NO3-N), Olsen phosphorus (P), and organic matter. Soil nitrate and P concentration were in the order corn > wheat > olive > pasture > forest. Soil EC and NO3-N showed significant within-year variability only in the corn and wheat systems. Corn and wheat had the lowest soil organic-matter content followed the order forest > pasture > olive grove = wheat = corn. However, total N did not significantly differ among land uses.

Formation and remobilisation of soil microbial residue. Effect of clay content and repeated additions of cellulose and sucrose

In two studies, we assessed the mass balance of added 14C-labelled sucrose and 15NH415NO3 by measuring 14CO2, 14C and 15N in soil microbial biomass (SMB) and 14C and 15N in soil solution. Specifically, we assessed the potential of recently added 14C to be re-mobilised by cryptic growth using subsequent additions of sucrose and cellulose and the effect of physical protection on the stabilisation of the labelled substrate. We used both a constructed soil with low soil organic matter content and varied the clay content as well as a natural soil. We observed a substantial initial as well as a later stage transfer of 14C into unidentifiable form, hypothesised to be microbial residues. When using a standard kEC value of 0.45, only roughly 50% of the added labelled substrates were accountable and therefore we explored the full range of reported kEC values to assess the mass balance. Subsequent application of unlabelled sucrose and cellulose did not substantially increase turnover 14C and 15N. Contrary to our expectation, there was no effect of clay content on the amount of unidentified 14C and 15N. The unidentified 14C and 15N is ascribed to formation of soil microbial residue. The low recovery of added isotope suggests that our mechanistic models are missing a large and important pool in order to realistically simulate organic matter turnover in soil.

Incorporation of carbon from decomposing litter of two pioneer plant species into microbial communities of the detritusphere

Initial ecosystems are characterized by a low availability of nutrients and a low soil organic matter content. Interactions of plants and microorganisms in such environments, particularly in relation to litter decomposition, are very important for further ecosystem development. In a litter decomposition study using an initial substrate from a former mining area, we applied the litter of two contrasting pioneer plant species (legume vs. pasture plants), Lotus corniculatus and Calamagrostis epigejos, which are commonly observed in the study area. Litter decomposition was investigated and carbon (C) translocation from litter into soil microorganisms was described by following (13) C from labelled plant litter materials into the fraction of phospholipid fatty acids. Labile C compounds of both plant litter types were easily degraded during the first 4 weeks of litter decomposition. In contrast to climax ecosystems, where the importance of fungi for litter degradation has been shown in many studies, in our experiment, data clearly indicate an outcompetition of fungi by Gram-positive bacteria as soon as available nitrogen is limited in the detritusphere.

Butachlor Sorption in Organically Rich Soil Particles

The herbicide butachlor [N‐(butoxymethyl)‐2‐chloro‐N‐(2,6‐diethylphenyl)acetamide] is a pre‐emergence herbicide belonging to the chloroacetanilide group used widely to control grasses in Asian countries. Butachlor has toxicity to aquatic organisms and earthworms and can induce apoptosis in mammalian cells. This study used a batch equilibration method to investigate butachlor sorption by different size organomineral fractions of a black soil. About 60 to 70% of butachlor was adsorbed on the clay size fraction, 30 to 40% on the silt fraction, and <0.3% by the fine sand fraction. For the clay fraction, the nonlinearity of adsorption was significant in the low equilibrium concentration range. For the silt and fine sand fractions, the isotherms were near linear across the concentration range studied. Butachlor adsorption on a clay fraction treated with H2O2 showed that the degree of nonlinearity became smaller, and the value of the normalized sorption coefficient for organic C (Koc) was much higher than that of the untreated clay fraction. Mineral colloids might have a dual function in the butachlor adsorption process. For an adsorbent with a very low soil organic matter (SOM) content, mineral colloids could enhance butachlor adsorption because of their high exposed mineral surface, which would result in higher Koc values. For an adsorbent with a high SOM content, mineral colloids might weaken the SOM partition function because of their strong association with and coating of SOM, which would result in lower Koc values. These results are useful to better understand the adsorption mechanism of anthropogenic organics in different components and size fractions of soils.

Effect of surfactant on the estimation by solid phase microextraction of bioavailable pyrene in soil samples

This study was focused on the effect of the presence of surfactant on the bioremediation efficacy and sensitivity of solid phase microextraction (SPME) in the pyrene-contaminated soil. Soils with 1.3 and 7.6% soil organic matter (SOM) were tested for biodegradation by microorganisms and extracted by aqueous solutions of the matrix used for SPME. For the biodegradation test, the presence of Triton X-100 at 5× CMC (critical micelle concentration) significantly enhanced pyrene removal for soil with lower SOM content (1.3%). However, this removal was insignificant for soil with higher SOM content (7.6%). The results may suggest that 5× CMC was not sufficient to improve significantly pyrene desorption for soil with higher SOM content. For the bioavailability test, in the absence of Triton X-100, SPME estimation of bioavailability in soils with indigenous or seeded microorganisms had an error range within 15%. However, with addition of Triton X-100, SPME estimations showed a significant decline (41 and 77%), in relation to their predicted values, for soil samples with SOM of 1.3 and 7.6%, respectively. The main reason for this underestimation is that micelle formation from the application of surfactant impacted the concentration of dissolved pyrene, rather than competitive site occupation between pyrene and surfactant molecules for SPME fiber. Thus, if soil samples contain surfactant, SPME would significantly underestimate bioavailability and risk level of PAH-contaminated sites.

ORGANIC HIGHBUSH BLUEBERRIES (VACCINIUM CORYMBOSUM L.) PRODUCTION: LONG-TERM EFFECT OF CULTIVATION SYSTEM AND PH REGULATION ON PLANT GROWTH, YIELD AND ROOT DISTRIBUTION AND BIOMASS WITH TWO CULTIVARS

In recent years, an increasing market for blueberries has developed in Switzerland. Blueberries are well suited for organic production because few disease and insect pests are currently found under Swiss conditions. Soil conditions present the greatest obstacle to blueberry cultivation in that Swiss soils are often too alkaline and have low soil organic matter content. During a nine-year (1998–2006) field experiment on an alkaline soil, we tested the feasibility and plant performance of three peat-free cultivation systems (deep ditch, flat ditch, raised bed) and two acidification methods (sulfur or citric acid versus an untreated control). Cultivars were ‘Bluecrop’ and ‘Reka’. The vegetative growth of the bushes was not significantly affected by the cultivation systems. However, the deep ditch system obtained produced significantlyhigher yields (6.04 kg) compared with the raised bed system (5.13 kg). The yield in the flat ditch system (5.96 kg) was not significantly different from either of the other two systems. Lowering pH levels in the substrate sufficiently (pH<4.8) was achieved only with sulfur (30 g/plant/y). The acidification treatments affected the shrub development and yields significantly. Compared with the untreated control, shrub volume (+43%) and accumulated yield (+55%) were greater in the treatment with application of sulfur. With the citric acid treatment, shrub volume and yield were increased by 12% and 9%, respectively. Root growth and biomass showed no differences between the cultivation systems. A flat ditch with pine sawdust combined with acidification by sulfur offers good plant growth and yield performance and is cheaper to install compared with deep ditch. Based on these results, we have recommended this cultivation system with sulfur applications for commercial blueberry production in regions with alkaline soils in Switzerland since 2005.

Dependence of soil fertility on organic and mineral fertilization in a 46-year long-term field experiment

Increasing doses of farmyard manure (FYM) or equivalent mineral NPK fertilizers and their combinations were analysed in a crop rotation with potato, maize and winter wheat with special regard to their long-term influence on soil fertility. The yield-increasing capacity of FYM doses was only 82%, as compared to the equivalent amount of mineral NPK. Fairly high N release (50.9 kg ha −1 ) could be observed on the unfertilized plots. Great differences in N utilization were recorded, depending on the form and dose of fertilizers. The average N utilization from FYM was only 29.3%, while that of the equivalent fertilizer application was 49.8%. The lowest soil reactions were observed without fertilization and at the highest NPK doses. Negative N balances generally resulted in low soil organic matter content. FYM and equivalent NPK fertilizers had a similar influence on the ammonium lactate (AL)-extractable K 2 O content of the soil, while an increase in the AL-P 2 O 5 content could be observed in the case of mineral fertilization.

Soil fertility as affected by long-term fertilization and crop sequence

In a crop rotation with potato, maize and winter wheat, increasing doses of farmyard manure (FYM) or equivalent NPK fertilizers and their combinations were analyzed with special regard to their long-term influence on soil fertility. The yield-increasing capacity of FYM doses was only 82%, as compared to the equivalent amount of mineral NPK. On the unfertilized plots, fairly high N-release (50.9 kg ha−1) could be observed. Great differences in N-utilization developed depending on the form and dose of fertilizers. N-utilization from FYM was only 29.3%, while that of equivalent fertilizer application was 49.8%. The lowest soil reactions were observed both without fertilization and with the highest NPK doses. Negative N-balances generally resulted in low soil organic matter content. While FYM and equivalent NPK fertilizers similarly influenced the ammonium lactate-extractable AL-K2O content of the soil, an increased AL-P2O5 content could be observed in the case of mineral fertilization. The worst previous crop of wheat was maize (100%), wheat itself was better (133%), and potato was markedly good. The worst previous crop of maize was itself (100%), while wheat and potato were equally favorable (136–137%).

Physical properties of low-lying agricultural peat soils in England

The drainage of low-lying peatland for agriculture and subsequent conservation measures adopted on some of these peatlands has led to differing degrees of change in the physical and hydraulic characteristics of the soil. We assessed the degree of peat decomposition and measured the soil organic matter (SOM) content, particle density, dry bulk density, saturated hydraulic conductivity, and water retention and shrinkage characteristics for a range of peat soil horizons sampled in two low-lying agricultural peatland in England. The physical and hydraulic properties of the peats considered were significantly influenced by the degree of decomposition. Higher decomposition resulted in lower SOM content, higher bulk density and lower porosity. In addition, pedogenic alterations due to intensive drainage and land use lead to a greater degradation of the soil structure in the upper soil layers. Less decomposed peats had a higher propensity to shrink under increasing water potentials. They had a lower air entry pressure and drained faster than degraded peats. In addition, they had a higher saturated hydraulic conductivity. This shows that decomposition and pedogenic alterations lead to the loss of structural pores. Hence decomposition and humification result in the degradation of the soil structure and a reduction in the soil capacity to store, retain and transmit water.

Substrate utilization patterns of desert soil microbial communities in response to xeric and mesic conditions

The Negev Desert is characterized by low soil moisture and organic matter content and an unpredictable rainfall amount, dispersion, and intensity. Water and nutrient availability are, therefore, the major limiting factors of biological activity in arid and semi-arid ecosystems. Plants have developed different ecophysiological adaptations in order to cope with the harsh conditions in this xeric environment, e.g., excretion of salt ( Reaumuria negevensis) and chemical compounds ( Artemisia sieberi) through the leaves. Microorganisms constitute a major part of these ecosystems' total biomass, and are diverse members of the soil food web, being primarily responsible for breaking down complex organic compounds, which are then recycled. They are also known to be very sensitive to abiotic changes and can time their activity to the environmental conditions. Soil samples were collected monthly from a 0 to 10 cm depth, under the canopies of A. sieberi, Noaea mucronata, and R. negevensis. Samples collected from inter-shrub spaces served as control. CO 2 evolution, microbial biomass, microbial functional diversity, and the physiological profile of the community, were determined by MicroResp™ analysis. A significant difference was found between the two dry periods in most of the examined parameters. The values of water, organic matter content, and total soluble nitrogen were higher in soil samples collected in the vicinity of R. negevensis than in samples collected in the vicinity of N. mucronata, A. sieberi, and the open area. A similar trend was found in CO 2 evolution, microbial biomass, and H' values, in which soil samples collected beneath the canopies of N. mucronata and R. negevensis and from open area had higher values during the wet periods (which were characterized by a mesic environment) and in samples collected beneath the A. sieberi in the wet 2006 and dry 2007 periods.

Sorption of the herbicide terbuthylazine in two New Zealand forest soils amended with biosolids and biochars

Terbuthylazine is one of the most commonly used herbicides for vegetation management in forest plantations in New Zealand. Knowledge about the sorption of terbuthylazine on forest soils, especially the influence of coexisting organic amendments, remains obscure. In this study, we evaluated the effects of biosolids and biochars on the sorption of terbuthylazine to forest soils. Two pumice soils, including a forest landing site soil with low soil organic matter content and an organic carbon rich topsoil under standard forest management, were sampled from a 2-year-old replanted pine plantation. The soils were mixed with four organic amendments, including two thermally dried biosolids with one digested and the other undigested, a biochar produced from high temperature pyrolysis (700°C), and a biochar from pyrolysis with a lower temperature (approximately 350°C). A batch equilibration method was used to determine terbuthylazine adsorption-desorption in organic amendment-treated and untreated soils. Adsorption and desorption isotherms were described with the Freundlich equation. Adsorption and desorption isotherms in the soils with or without organic amendments were well described by the Freundlich model. The undigested or digested biosolids added to the topsoil had a negligible or limited effect on the adsorption to terbuthylazine. The addition of the other amendments to the two soils all enhanced the adsorption. The biochars displayed higher efficiency in improving soils’ adsorption capacity to terbuthylazine than the biosolids. Among the organic amendments evaluated, the biochar obtained from high temperature pyrolysis demonstrated the most significant enhancement on adsorption with an enhancing factor of 63; whereas, the digested biosolids showed the weakest enhancement. Furthermore, terbuthylazine adsorbed by the digested biosolids appeared to be more easily desorbed than that by biochar treatments. This work indicates that the addition of organic amendments to forest soils, particularly biochar to a soil with low native organic matter, may enhance soil sorption of terbuthylazine and thus reduce the possibility of the hydrophobic herbicide leaching to groundwater.

Field evidence of a negative correlation between saturated hydraulic conductivity and soil carbon in a sandy soil

Soil organic matter (SOM) is generally assumed to be positively correlated with saturated hydraulic conductivity (KS). However, recent studies of pedotransfer functions suggest a possible negativeKS‐SOM relationship that still needs independent verification. Our fieldKSstudy of sandy soils in a semiarid region provides such in situ evidence of a negativeKS‐SOM relationship, which is nonlinear and is strongest at the lowest levels of soil carbon (&lt;0.1%). A regression analysis also shows that soil carbon is an important factor for explainingKSin those soils. The likely reason for the observed negativeKS‐SOM relationship is a reduced wettability caused by SOM, which is believed to outweigh the impacts of any increase inKScaused by soil aggregation. The low SOM content and large particle size of sand may explain the limited effect of SOM on soil aggregation processes in the examined soils.

Photoacceleration of plant litter decomposition in an arid environment

In arid ecosystems, abiotic processes facilitate the physical and chemical degradation of plant litter to the extent that decomposition models that use climatic and litter composition variables as surrogates for microbial activity are not predictive. The purpose of this study was to estimate the potential contribution of photodegradation to the decomposition of plant litters that varies in architecture and chemical composition. Litter of Pinus edulis, Juniperus monosperma and Populus deltoides were exposed to ambient and attenuated sunlight, with and without supplemental water additions, at a riparian forest site along the Middle Rio Grande (New Mexico, USA). Mass loss, elemental composition, and microbial extracellular enzyme activities (EEA) were measured over 639 days. The composition of the fungal communities associated with the decomposing litters was compared by analyses of fungal ITS nrDNA sequences. Litter exposed to ambient sunlight had greater mass loss rates than shaded litter, independent of the water treatment: Populus increased by 100%, Pinus by 86% and Juniperus by 46%. The increases were proportional to exposed litter surface area per g dry mass. EEA potentials, particularly oxidative activities, were low in comparison to those measured in mesic ecosystems. For Populus litter, the principal driver of photoacceleration appeared to be photodegradation of cellulose; for Pinus, it was photodegradation of polyphenols; for Juniperus accelerated mass loss was associated with photodegradation of both polysaccharides and polyphenols. Fungal community composition varied by litter type, but the dominant colonizers were yeasts and dark-septate hyphal taxa; a finding consistent with the low enzymatic oxidation potential. This study shows that photochemical oxidation can supplement enzymatic oxidation and increase decomposition rates. As a result, organic matter decomposition in arid ecosystems is not restricted to periods of high moisture availability as is plant production. This decoupling may partly account for the low soil organic matter content of these ecosystems.

SORÇÃO DE S-TRIAZINAS EM SOLOS DE MATA ATLÂNTICA BRASILEIROS

Esta pesquisa foi conduzida para avaliar a sorção de ametrina, atrazina, simazina, prometrina e metamitron em solos de Mata Atlântica na região de Ubatuba, empregando-se o método em batelada. Os herbicidas foram fracamente retidos em solos com baixo teor de matéria orgânica (MO) e, portanto, apresentaram elevado potencial de contaminação da água. Todos os herbicidas mostraram alto valor de Koc em solos da classe Gleissolo Melânico Distrófico, que contém o teor mais elevado de MO. As isotermas de sorção dos herbicidas no Gleissolo Melânico Distrófico sugerem interações específicas entre os herbicidas e a MO, provavelmente com protonação parcial dos herbicidas seguida por processos de troca-iônica e/ou formação de pontes de hidrogênio dos grupos hidroxila sobre a superfície da MO.

Experimental warming does not enhance soil respiration in a semiarid temperate forest-steppe ecosystem

The influence of simulated climate change on soil respiration was studied in a field experiment on 4 m × 5 m plots in the semiarid temperate Pannonian sand forest-steppe. This ecosystem type has low productivity and soil organic matter content, and covers large areas, yet data on soil carbon fluxes are still limited. Soil respiration rate – measured monthly between April and November from 2003 to 2006 – remained very low (0.09 – 1.53 μmol CO2 m−2 s−1) in accordance with the moderate biological activity and low humus content of the nutrient poor, coarse sandy soil. Specific soil respiration rate (calculated for unit soil organic matter content), however, was relatively high (0.36 – 7.92 μmol CO2 g−1 Corg h−1) suggesting substrate limitation for soil biological activity. During the day, soil respiration rate was significantly lower at dawn than at midday, while seasonally clear temperature limitation in winter and water limitation in summer were detected. Between years, annual precipitation appeared to be important in determining soil carbon efflux intensity. Nocturnal warming increased soil temperature in 1 cm depth at dawn by 1.6°C on the average, and decreased topsoil (0–11 cm) moisture content by 0.45 vol%. Drought treatment decreased soil moisture content by an average of 0.81 vol%. Soil respiration rate tended to decrease by 7–15% and 13–15% in response to heat and drought treatment, respectively, although the changes were not statistically significant. Nocturnal warming usually prevented dew formation, and that probably also influenced soil respiration. Based on these results, we expect a reduction in the volume and rate of organic matter turnover in this ecosystem in response to the anticipated climate change in the region.