Effects Of Different Land Research Articles

Divergence in energy sources for Prochilodus lineatus (Characiformes: Prochilodontidae) in Neotropical floodplains

ABSTRACT The stable carbon isotopic variability and the contributions of autochthonous (sediment microbial biomass, phytoplankton, and periphyton) and allochthonous (soil microbial biomass) sources available to the detritivorous fish Prochilodus lineatus were investigated in three environments of the floodplain of the Upper Paraná River. The isotopic composition of carbon sources and fish varied significantly among the studied environments. The autochthonous resources, represented by the phytoplankton, were the most assimilated by the species, followed by periphyton and sediment microbial biomass. The species used the sources differently in each environment. This study suggests that the inherent characteristics of this area, as well as the size of the watershed, the dry season, anthropogenic actions, and phytoplankton productivity, favor the use of autochthonous resources by the species studied. Therefore, studies in the floodplain should employ an eco-hydrological approach that quantifies the magnitude of energy subsidies, as well as an access route to consumers, knowledge about the selectivity of detritivorous species and the effects of different land uses.

The Effect of Different Land Uses on Some Physical, Chemical and Biological Quality Indicators of Soil

The Effect of Different Land Uses on Some Physical, Chemical and Biological Quality Indicators of Soil

The effects of different land uses on soil hydraulic properties in the Loess Plateau, Northern China

AbstractSome agriculture practices are unsuitable in the northern hilly region of the Chinese Loess Plateau and have resulted in the degradation of the native vegetation ecosystems and unfavorable soil hydraulic properties, which cause serious soil losses. The objective of this study was to ascertain the influence of land use changes on soil infiltration rate and other related soil properties in this region. A total of 90 infiltration tests were run on six different land uses (natural grassland, apple orchard, abandoned apple orchard, farmland wheat, farmland maize, and scrub grassland). For studying the infiltration rate, a triplicate of infiltration tests had been taken using a disc permeameter with different pressure heads. Infiltration rate was high in abandoned apple orchard (10 mm min−1) whereas very low in apple orchard (0.6 mm min−1). The statistical analysis showed that the main soil properties were affected by changes of land use types or vegetation cover. Compared with that in the natural grassland and abandoned apple orchard sites, a notable reduction of soil root biomass, infiltration, and bulk density in apple orchard was recorded. The root image analysis showed that the natural grassland and abandoned apple orchard have strong root systems, that is, root length density 6.97 ± 0.344 cm cm−3, root surface area 1.56 ± 0.24 cm2 cm−3, and average root diameter 0.814 ± 0.24 mm, in comparison with other sites. The limited root length density, root surface area, and average diameter were recorded in apple orchard 0.51 ± 0.03 cm cm−3, 0.49 ± 0.12 cm2 cm−3, and 1.88 ± 0.24 mm. Conclusively, our study suggests that converting farmland apple orchard into grassland or scrubland may change soil hydraulic properties, which may help to reduce soil losses in the Loess Plateau.

Soil quality assessment under different land uses in an alpine grassland

Soil quality index (SQI) is widely practiced form plot to national scales to assess the status and use potential of soils. However, how to objectively choose relevant indicators and score these indicators to generate comprehensive SQI is still a major challenge because of the complexity and site-specificity of soils. The objective of this study is to develop SQI using different indicators selecting methods (total data set, minimum data set and revised minimum data set) and scoring methods (linear and non-linear) to evaluate the influences of three land uses (CL, cropland; GR, grazing grassland; FE, grassland enclosure) on soil quality in an alpine grassland. Fourteen soil indicators representing soil physical, chemical and biological properties were measured at 0–20 cm depth. One-way analysis of variance and principal component analysis were used with the fourteen indicators to select the total data set, minimum data set and revised minimum data set. Eleven soil indicators exhibited treatment differences were identified as the total data set. However, only two (AN and MBC) and four (MWD, SOC, AN and MBC) soil indicators were retained in the minimum data set and revised minimum data set, respectively. The six SQIs developed in this study quantified the effects of different land uses on soil quality equally well regarding both sensitivity and accuracy. However, the differentiating ability of SQI calculated using the non-linear scoring-revised minimum data set method (SQI-NLRM) was better than other SQIs based on minimum data set and revised minimum data set because of the highest F value and greatest correlation coefficient with SQI based on total data set. Under GR and CL treatment, SQI-NLRM values were 15.15% and 69.70% lower than that under FE treatment. These results indicated that land use conversions can significantly change the soil quality in the alpine grassland, and the SQI-NLRM developed in this study provides a sensitive and effective approach for quantitative evaluation of soil quality.

Land use influences harvestman diversity in northern Spain: a case study involving secondary grasslands and forest plantations (Arachnida: Opiliones)

Harvestmen have a general distribution pattern with more species and higher abundance in forests than in open habitats, as previously verified in mountain Cantabrian areas of northern Spain, of the Orocantabrian Province. The study of harvestmen of the low Cantabrian areas of the adjacent biogeographic Cantabro-Atlantic Province is highly appropriate to determine the influence of biogeographic position on the main diversity parameters and the effect of different land uses on harvestman assemblages. The main types of managed habitats (forest plantations and secondary grasslands), together with natural forests, non-planted young forests, shrublands and habitat boundaries were continuously sampled with seven pitfall traps during 1 year at 28 sites. The harvestman assemblages were classified using six different analyses, and indicator species were identified. The spatial patterns of harvestman diversity in low areas differed from those of mountain areas, although they have 15 species in common. Remarkably, higher average harvestman species richness was measured in low Cantabrian areas than in mountain areas. Shrublands and boundaries were the most species-rich habitats. Forested areas were the poorest in abundance, and were not the habitats richest in harvestman species, though they had higher average richness than mountain Cantabrian forests. Grasslands had a unique harvestman composition with significant extraordinary abundances, in particular of Homalenotus quadridentatus (indicator species of this habitat) and H. laranderas. Interestingly, H. laranderas, Paroligolophus agrestis and Ischyropsalis hispanica, indicator species of some open habitats in low Cantabrian areas, have recently been shown to be indicators of shady forests in mountain Cantabrian territories.

The effects of forest succession and grazing intensity on bird diversity and the conservation value of a Northern Adriatic karstic landscape

We studied the effects of different land uses on conservation value and bird diversity in a Northern Adriatic karstic landscape. Our research area was situated in SW Slovenia and was covered with dry pastures and meadows in different stages of forest sucession and with different grazing intensities. We surveyed birds in 2007 and 2012 using the line transect method, with 50.4 km being covered each year. In the analysis we divided the survey transects into 200 m tiles which were used as statistical units in the analysis. We then modelled conservation value, bird diversity and bird abundances with different land uses; we used boosted regression trees as a modelling tool. Canonical correspondence analysis showed that a distinct group of birds occurred on tiles with higher grazing intensity. The species in this group also had significantly higher abundances in 2012 than in 2007. Forest succession was the most important predictor of SPA conservation value (Special Protected Areas according to the Directive on the conservation of wild birds of the European Union) and had negative effect on it; grazing intensity had a unimodal positive influence on conservation value and was most beneficial at low intensity. The model for the European conservation value showed a rather low predictive power. Farmland bird diversity was also negatively affected by forest and positively by grazing intensity. For the four Natura 2000 species—protected species in the SPA Kras (Woodlark Lullula arborea, Red-backed Shrike Lanius collurio, Corn Bunting Emberiza calandra and Skylark Alauda arvensis), forest cover also had a negative effect. Grazing intensity had a positive effect for Woodlark, Red-backed Shrike and Skylark. The highest SPA conservation value and farmland bird diversity could therefore be achieved in a landscape with as low a forest succession as possible and grazing present but at low intensity. We recommend inclusion of appropriate measures in the agri-environment schemes (CAP pillar II) of Rural Development Programmes of the countries in the region with similar areas. The payments should be sufficiently stimulative to reopen the large areas subject to forest encroachment in the Northern Adriatic hinterland.

Effects of the land use/cover on the surface runoff and soil loss in the Niğde-Akkaya Dam Watershed, Turkey

Erosion, flood, and overflow events are frequently experienced due to changes in the land use in watersheds where human impacts are intensive. It is important to understand the effects of land use types on erosion at a watershed scale. This knowledge can then be used to manage soil and water resources in watersheds better. The aim of this study is to determine the effects of different land uses/covers on the surface runoff and soil loss by using a rainfall simulator in natural land conditions in the Niğde Akkaya Dam watershed with semi-arid conditions. For this purpose, 5 cultivated lands with different product patterns with similar conditions (apple orchard (A), potato cultivation area (P), bean cultivation area (B), clover cultivated land (CL), abandoned cultivated land (AB), plantation areas (cedar (C) and almond (AL)), and pasturelands covered with Thymus sp. (T), Agropyron sp. (AG) and Stipa sp. (S) were selected for the applications. The applications were carried out in two repetitions on circular test parcels of 0.28m2 established in these lands. During the land applications, the characteristics of surface runoff (ponding time, surface runoff start time, average surface runoff rate, runoff coefficient) and the average sediment concentration in the surface runoff water were determined. The data obtained were evaluated by using the ANOVA, Duncan's test, and Pearson correlation analysis test and SPSS statistical program. The results of the study revealed that the surface runoff occurred in the abandoned cultivation area, bean cultivation area, potato cultivation area, and thyme-covered pastureland in a short time. The runoff coefficient values by the land cover are sorted from high to low as B>T>P>A>AB>AL>C>CL>S>AG. The sediment concentration in the runoff water is sorted from high to low as T>P>B>AB>AL>A>C>S. When the situation was evaluated in terms of the soil loss (erosion), it was concluded that the sorting is as P>T>A>AB>B>AL>C>S>CL.

Effect of different land cover/use types on canopy layer air temperature in an urban area with a dry climate

Knowledge of the influence of land cover on air temperature in arid cities is scarce, yet essential for urban planners to select landscape design and management strategies which can improve livability and provide efficient landscape irrigation. The objectives of this study were to consider the effects of urban land use on air temperature changes in an arid city based on data collected in Isfahan, Iran at a local scale. This study reports a statistical analysis of temperature variation with respect to land use throughout the day and night. It is also the first study to report the effects of land cover on the time that daily minimum and maximum temperature occurs. The land use characteristics considered included green space, streets, buildings, population density and bare land. Air temperature was measured for 42-months at the canopy level of five intra urban sites and one reference site in a lightly developed suburban location. The temperature of all intra-urban sites was higher than the suburban reference site for a majority of observations during daytime throughout the year. The effect of land use on air temperature overnight was greater than daytime. The highest temperature difference occurred overnight in summer, with differences up to 12 °C when comparing an irrigated, vegetated site and the suburban site on an hourly basis. On average, the daily maximum temperature in urban areas occurred sooner than in the suburb in all seasons. The highest mean time difference was 78 min between the commercial–residential and suburban stations in summer.

The effects of land use at different spatial scales on instream features in agricultural streams

The conversion of forests into agriculture has been identified as a key process for stream homogenization. However, the effects of this conversion can be scale-dependent. In this context, our aim was to identify the influence of different land uses at different spatial scales (catchment, drainage network and local) on instream features in agricultural streams. We defined six classes of land use: native forest, reforestation, herbaceous and shrubs, pasture, sugarcane and other categories. We obtained 22 variables related to instream, riparian area, stream morphology and water physicochemical characteristics in 86 stream reaches. To identify and isolate the effect of different land uses at different spatial scales on instream features, we performed a partial redundancy analysis (p-RDA). Different land uses and scales influenced instream features and defined two stream groups: (i) homogeneous streams with a higher proportion of sand substrate and instream grasses that were associated with the proportion of herbaceous vegetation at the local scale and with pasture at all scales and (ii) heterogeneous streams with a higher physical habitat integrity associated with the proportion of forest and sugarcane at the local and catchment scales. Land use at the catchment scale affected the physicochemical water properties and stream morphology, whereas stream physical habitat (i.e., substrate, instream cover, marginal vegetation and stream physical habitat condition) was mainly influenced by land use at the local scale (i.e., 150 m radius). Pure catchment, drainage network and local land uses explained 9%, 7% and 4%, respectively, of the total variation of instream features. Thus, to be most effective, stream conservation and restoration efforts should not be limited to only one scale.

Coupled control of land uses and aquatic biological processes on the diurnal hydrochemical variations in the five ponds at the Shawan Karst Test Site, China: Implications for the carbonate weathering-related carbon sink

High-resolution hydrochemical data from five spring-fed ponds are presented to demonstrate the effect of different land uses and aquatic biological processes on the carbon cycle at a karst-analog test site. The results show that hydrochemical parameters including pH and the concentrations of HCO3−, Ca2+, NO3−, partial pressures of CO2 (pCO2) and dissolved O2 (DO) as well as carbon isotopic compositions (δ13C) of HCO3– in the pond water all displayed distinct diurnal variations, while those of the spring water itself were rather stable. The coupled dynamic behaviors of pCO2, DO and NO3− indicate a significant influence from the metabolism of submerged plants in the ponds. In the afternoon, when photosynthesis is the strongest, the pCO2 of the five pond waters was lower even than that of the ambient atmosphere, demonstrating the existence of a “biological carbon pumping (BCP) effect”, similar to that in the oceans. It was determined that, in October (autumn), the BCP fluxes in the five spring-fed ponds were 156±51tCkm−2a−1 in P1 (Pond 1 – adjoining a bare rock shore), 239±83tCkm−2a−1 in P2 (adjoining uncultivated soil), 414±139tCkm−2a−1 in P3 (adjoining land cultivated with corn), 493±165tCkm−2a−1 in P4 (adjoining grassland) and 399±124tCkm−2a−1 of P5 (adjoining brushland), indicating the potentially significant role of aquatic photosynthesis in stabilizing the carbonate weathering-related carbon sink. In addition, by comparing the DIC concentrations and fluxes of DIC transformed into autochthonous organic matter (AOC) in the five ponds, the so-called “DIC fertilization effect” was found in which more AOC is produced in pond waters with higher concentrations of DIC. This implies that the carbon cycle driven by aquatic biological processes can be regulated by changing land use and cover, the latter determining the DIC concentrations. Further, the rock weathering-related carbon sink is underestimated if one only considers the DIC component in surface waters instead of both DIC and AOC.

Impacts of land-use and management systems on organic carbon and water-physical properties of a Latossolo Amarelo (Oxisol)

The Cerrado biome has outstanding territorial relevance in the state of Piauí, in which weather conditions, relief and favorable soil has made this region one reference in food production. This study focused to evaluate the effects of different land uses, management systems and their respective terms on organic carbon content and physical properties of a Latossolo Amarelo (Oxisol) in the Southwestern Piauí state. The study was performed in the city of Uruçuí, situated in the southwestern Piauí state. We assessed nine farming areas with different backgrounds regarding land-use, management system and run time. The treatments consisted of areas under no-till for 3 and 6 years (NT3 and NT6), under pasture for 2 and 5 years (PA2 and PA6), under eucalyptus plantation for six and twelve years (EU6 and EU12), under conventional tillage for two and 8 years (CT2 and CT8) and under native Cerrado (NC), which represented a reference condition. Conversion of the native Cerrado into no-till and grazing areas increased soil organic carbon content over time.

Growth and survival of juvenile Pomacea canaliculata (Gastropoda: Ampullariidae) in plain streams associated to different land uses

ABSTRACTPomacea canaliculata is an apple snail that has become an invasive species in several countries. In this research, through two simultaneous experiments, we assessed the effects of different land uses (urban, agriculture, cattle grazing, farms and recreation) on the growth and survival of snails from native populations. The survival was not affected by the water quality of the three streams studied, whereas the growth of snails exposed to the water of the urban stream was impaired. Therefore, our results suggest that the growth rate of P. canaliculata could be useful for the assessment of a moderate urban impact.

Soil nematodes associated with different land uses in the Los Tuxtlas Biosphere Reserve, Veracruz, Mexico

Modification of above-ground land use leads to many changes in the below-ground rhizosphere. A study was conducted of soil nematodes and their diversity associated with different land uses in the Biosphere Reserve Los Tuxtlas, Mexico. Three sites were selected to investigate 4 types of land uses: natural forest, secondary forest, pasture, and maize fields. Total abundance of nematodes and estimators based on generic and diversity indices were assessed and compared between the 4 land uses and sites. Fifty-three families and 124 genera of nematodes were identified from the study area. The dominant families were Criconematidae, Hoplolaimidae, Cephalobidae, and Tylenchidae, and the most abundant genera in this study were Helicotylenchus, Discocriconemella, Tylenchus, Steinernema and Mesocriconema. The greatest nematode abundance, generic richness, and diversity were found in natural forest, closely followed by secondary forest. Intensive (largely monocrop) agricultural systems, represented by maize fields and pasture, had low generic richness and significantly less diversity than non-disturbed systems. Most of the estimators and indices were useful in showing the significant effects of different land uses on soil nematodes in Los Tuxtlas, Mexico. This study is the first of its type to be carried out in the Biosphere Reserve Los Tuxtlas, being the first report of soil nematodes that shows the effects of the land use changes that have been made in recent years.

The Effects of Different Land Covers on Foundation Heat Exchangers Design in Chinese Rural Areas

The Ground Source Heat Pump (GSHP) system is extensively applied all around world for building heating and cooling. A new system type which uses foundation heat exchangers (FHXs) to reduce system capital cost has been suggested. This paper aims at studying the effects of different land covers on FHXs design lengths; consequently these affect the system capital cost. The FHXs are more applicable to rural areas since it requires enough space for laying the heat exchangers. In Chinese rural area, FHXs buried at 8 locations in 4 different cli-mates are investigated. In each location, the FHX design lengths under bare soil, concrete and vegetation are simulated. It is found that, in warm climates, land cover type has little effect on the results. In other climates, the FHX design length under bare soil and results under concrete are respectively 5.8%-18.1% and 15.9%-38.3% longer than the results under vegetation cover.

Características e atributos de Latossolos sob diferentes usos na região Oeste do Estado da Bahia

Resumo O objetivo deste trabalho foi avaliar os efeitos de diferentes usos da terra nas características e nos atributos de Latossolos da região Oeste do Estado da Bahia. Os Latossolos apresentavam texturas com fração areia amplamente predominante, e foram avaliados em áreas de cerrado, algodão, soja e feijão, no Município de Luís Eduardo Magalhães. A caracterização morfológica e a coleta de amostras de solos para avaliação dos atributos físicos e químicos por horizontes foram feitas em minitrincheiras, enquanto a avaliação da condutividade hidráulica saturada foi feita com permeâmetro de Guelph em duas profundidades: 0,0-0,20 e 0,20-0,40 m. Os Latossolos avaliados, além de uma estrutura maciça, apresentaram horizonte genético adensado, que, sob uso agrícola, torna-se mais compactado, espesso e superficial, e forma torrões quando revolvido. O uso agrícola reduz a condutividade hidráulica saturada dos Latossolos avaliados nas duas camadas, com exceção do cultivo de feijão.

Effects of land uses on soil physic-chemical properties and erodibility in collapsing-gully alluvial fan of Anxi County, China

As a special kind of soil erosion that severely deteriorates the qualities of soil in granite regions, collapsing gully is widely distributed in the tropical and subtropical areas of South China. In particular, collapsing-gully erosion produces a large amount of sediment deposited on the plough layer of alluvial fan farmland and causes increase of desertification, great reduction of nutrients and rapid enhancement of erodibility in the soil. This study was designed to evaluate the effects of different land uses on the soil physic-chemical properties and erodibility of collapsing-gully alluvial fan. Our results show that the physical properties of soil in alluvial fan were greatly improved with smaller bulk density, increased soil porosity, strengthened water holding capacity and a higher particulate matter content. The chemical properties of soil were also significantly improved, including pH, cation exchange capacity, and the contents of organic matter, total and available nitrogen, potassium and phosphorus. All the land uses were proved to improve the soil properties, especially in the tea garden, vegetable land and paddy field. The results of correlation analyses among the properties demonstrate that the physical and chemical properties were significantly correlated, indicating that improving the soil physical properties is an effective method to increase the soil nutrient in the farmland of collapsing-gully alluvial fan. In addition, the application of land uses included grass land, eucalyptus forest land, vegetable land, tea garden, sweet potato land, and paddy field reduced the erodibility of the soil compare to bare land. The erodibility K values of soils in grass land, eucalyptus forest land, vegetable land, tea garden, sweet potato land, and paddy field were 14.43, 16.97, 45.45, 33.12, 18.94, and 34.01% lower than those of bare land, respectively. The results of multiple linear regression analysis show that the soil erodibility had a significant correlation with the physic-chemical properties, especially the soil texture and the content of organic matter. In conclusion, our results demonstrate that different land use patterns are effective to improve the quality of the soil in collapsing-gully alluvial fan, including the improvements of the soil structure, nutrients and anti-erosion ability. Our findings provide important implications for the soil improvement in the farmland of collapsing-gully alluvial fan.

Environmental factors controlling soil organic carbon storage in loess soils of a subhumid region, northern Iran

Soil organic carbon (SOC) storage is a basic measure used to study soil productivity, hydrology and the balance among greenhouse gases. Variation of SOC is controlled by environmental factors such as land use and topography. Toshan watershed located in northern Iran was selected to study the effects of different land uses i.e. forest (FO), cropland (CP), orchard (OR) and abandoned land (AB) on different slope gradients and aspects on SOC both in surface (0–30cm) and subsurface (30–100cm) layers. A total of 364 soil samples plus 1638 undisturbed ones were collected from two soil layers in 182 sampling sites. Results showed that the surface 30cm soil layer was solely responsible for 54.8% of SOC density. On average, FO with 22.84kgm−2 had the highest SOC density in 0–100cm layer. Deforestation and agricultural activities have resulted in a significant 48.2% decrease of SOC density in 0–30cm soil layer. North facing slope (N) aspect and also flat area of all land uses had the higher SOC density compared to east (E) and west facing slope (W) aspects in this subhumid region in 0–100cm layer. Generally, in the upper 100cm soil layer of deforested lands, gentle and moderate slopes had higher SOC density than steeper slopes. There was a positive significant correlation between SOC density and clay content. The largest amount of SOC storage was observed in the surface 30cm layer accounting for 74,907.94Mg (54.4% of total SOC storage), indicating the important key role of topsoil in conserving SOC. FO with one-third proportion of the total area stored the largest amount of SOC (39,325.55Mg; 52.5%) in surface layer. In conclusion, protection of forest lands is higher important to increase SOC storage. Agricultural activities on steep E and W aspects in deforested lands must be reduced or prohibited. The subsoil has almost the same contribution to SOC storage and therefore should be carefully considered for management measures. Generally, interaction between environmental factors on storing SOC and also rate of carbon loss to the atmosphere was significant.

The effect of different land uses on arbuscular mycorrhizal fungi in the northwestern Black Sea Region.

The object of the present research was to establish correlations between the status of root colonization of arbuscular mycorrhizal fungi (AMF) and different types of land use. In order to achieve this aim, rhizosphere soil samples from grassland crops were taken during June and July of 2013 in order to use for determining several soil characteristics. The 27 different taxa and 60 soil samples were collected from the rhizosphere level in the study areas. The existence of AMF was confirmed in 100% of these plants with different rations of colonization (approximately 12-89%). Bromus racemosus L. (pasture) was the most dense taxon with the percentage of AMF colonization of 88.9%, and Trifolium pratense L. (forest) was the least dense taxon with the percentage of AMF colonization of 12.2% (average 52.0%). As a result of the statistical analysis, a positive relationship was found between the botanical composition of legumes and AMF colonization (r = 0.35; p = 0.006). However, a negative relationship was determined between botanical composition of other plant families and AMF colonization (r = -0.39; p = 0.002). In addition, a positive relationship was defined between soil pH (H2O) and the root colonization of AMF (r = 0.35; p = 0.005). The pasture had the highest mean value of AMF root colonization. However, the pasture and gap in the forest were in the same group, according to the results of the S-N-K test.

Land use and biodiversity patterns of the herpetofauna: The role of olive groves

The intensification of agriculture has significant environmental consequences. This intensification entails the simplification and homogenisation of the landscape, which leads to strong negative impacts at ecosystem level, including declines in animal biodiversity. The purpose of this study was to assess the effect of different land uses on reptilian and amphibian biodiversity patterns at a regional scale by analysing a large database on the presence of amphibians and reptiles in Andalusia (southern Spain). GIS techniques and the Ecological-Niche Factor Analysis (ENFA) were applied in order to assess whether the habitat was suitable for each reptilian and amphibian species, when the land use variables were excluded. The incongruence between the potential and the observed species richness was then correlated with the main types of land use in Andalusia. Our results showed that irrigated and unirrigated olive groves were associated with a biodiversity deficit of amphibians and reptiles respectively, whereas natural forests and pastures, along with more heterogeneous crops areas, were more suitable. A clustering analysis showed that generalist species were related to olive groves whereas rare and specialist species were related to land uses related to natural vegetation. In summary, our results indicate that large areas covered by olives groves harbour less amphibian and reptilian diversity, thus suggesting that agro-environmental schemes should be carried to promote the species richness in these crops.

Soil organic carbon associated in size-fractions as affected by different land uses in karst region of Guizhou, Southwest China

Land use change has a significant effect on soil organic carbon (SOC), especially on labile organic carbon (LOC) due to its rapid response to soil changes and carbon supply. The objective of the study was to assess the effects of different land uses on soil fraction size distribution, SOC and LOC concentrations and their stocks in karst region of Guizhou Province, Southwest China. Studies were based on soil sampling in paddy, dryland, abandoned cultivated land for 3-years (AC-3), and abandoned cultivated land for 15-years (AC-15) in the 0–10, 10–20, and 20–30 cm depths in karst mountain area of Guizhou Province. Three fraction-size classes [macro (250–2000 μm), micro (53–250 μm), silt + clay (<53 μm)] were fractioned, and SOC and LOC concentrations in whole soil (non-fractionated) and different fraction sizes were also determined. The results showed that paddy contained the highest SOC and LOC concentrations in whole soil and different size-fractions as compared with other land uses down to 30 cm depth. However, the proportions of LOC to SOC were higher in AC-3 than the other land uses, especially pronounced in whole soil, which ranged from 17.5 to 26.3 % in different soil depths. Paddy also contained 23.7 % (100.9 Mg ha−1) more SOC and 17.6 % (19.7 Mg ha−1) more LOC stocks than dryland, whereas the SOC and LOC stocks in AC-15 and dryland were very close to each other in each soil depth. In paddy field, we found that macro-sized fractions contributed the greatest quantities of SOC to whole soil. In addition, paddy had significantly higher SOC stock values in macro-sized fractions than the other land uses in the both 0–10 and 10–20 cm depths. In the present study, there were no obvious increases of SOC and LOC pools among whole soil and different soil size-fractions after 15 years of land abandonment. These results suggest that natural recovery of SOC may take a long time after land abandonment, and paddy could serve as an important land use type for long-term carbon sequestration in karst region of Southwest China.