Time stability of soil water storage measured by neutron probe and the effects of calibration procedures in a small watershed

The knowledge of soil water storage (SWS) of soil profiles is crucial for the adoption of vegetation restoration practices. With the aim of identifying representative sites to obtain the mean SWS of a watershed, a time stability analysis of neutron probe evaluations of SWS was performed by the means of relative differences and Spearman rank correlation coefficients. At the same time, the effects of different neutron probe calibration procedures were explored on time stability analysis. mean SWS estimation. and preservation of the spatial variability of SWS. The selected watershed, with deep gullies and undulating slopes which cover an area of 20 ha, is characterized by an Ust-Sandiic Entisol and an Aeolian sandy soil. The dominant vegetation species are bunge needlegrass (Stipa bungeana Trim) and korshinsk peashrub (Carugano Korshinskii kom.). From June 11, 2007 to July 23,2008, SWS of the top1 m soil layer was evaluated for 20 dates, based on neutron probe data of 12 sampling sites. Three calibration procedures were employed: type 1, most complete, with each site having its own linear calibration equation (TrE); type II. with TrE equations extended over the whole field: and type III, with one single linear calibration curve for the whole field (UnE) and also correcting its intercept based on site specific relative difference analysis (RdE) and on linear fitting of data (RcE), both maintaining the same slope. A strong time stability of SWS estimated by TrE equations was identified. Soil particle size and soil organic matter content were recognized as the influencing factors for spatial variability of SWS. Land use influenced neither the spatial variability nor the time stability of SWS. Time stability analysis identified one site to represent the mean SWS of the whole watershed with mean absolute percentage errors of less than 10%, therefore. this site can be used as a predictor for the mean SWS of the watershed. Some equations of type II were found to be unsatisfactory to yield reliable mean SWS values or in preserving the associated soil spatial variability. Hence, it is recommended to be cautious in extending calibration equations to other sites since they might not consider the field variability. For the equations with corrected intercept (type III), which consider the spatial variability of calibration in a different way in relation to TrE, it was found that they can yield satisfactory means and standard deviation of SWS, except for the RdE equations, which largely leveled off the SWS values in the watershed. Correlation analysis showed that the neutron probe calibration was linked to soil bulk density and to organic matter content. Therefore, spatial variability of soil properties should be taken into account during the process of neutron probe calibration. This study provides useful information on the mean SWS observation with a time stable site and on distinct neutron probe calibration procedures, and it should be extended to soil water management studies with neutron probes, e.g., the process of vegetation restoration in wider area and soil types of the Loess Plateau in China. (C) 2009 Elsevier B.V. All rights reserved.

Temporal changes of an alfalfa succession and related soil physical properties on the Loess Plateau, China

The objective of this work was to investigate the relationship between changes in the plant community and changes in soil physical properties and water availability, during a succession from alfalfa (Medicago sativa L.) to natural vegetation on the Loess Plateau, China. Data from a succession sere spanning 32 years were collated, and vegetative indexes were compared to changes related to soil bulk density and soil water storage. The alfalfa yield increased for approximately 7 years, then it declined and the alfalfa was replaced by a natural community dominated by Stipa bungeana that began to thrive about 10 years after alfalfa seeding. Soil bulk density increased over time, but the deterioration of the alfalfa was mainly ascribed to a severe reduction in soil water storage, which was lowest around the time when degradation commenced. The results indicated that water consumption by alfalfa could be reduced by reducing plant density. The analysis of the data also suggested that soil water recharge could be facilitated by rotating the alfalfa with other crops, natural vegetation, or bare soil.

Plantas que causam alterações mecânicas ou traumáticas em ruminantes e equinos, com ênfase em Stipa spp. (Gramineae)

Várias plantas podem provocar algum tipo de injúria mecânica. Entre elas as que causam traumatismo da pele ou mucosas, e as que causam alterações do sistema digestório, incluindo obstrução esofágica, sobrecarga ruminal e obstrução intestinal. Neste trabalho são revisadas algumas plantas que causam essas alterações e é descrito um surto de injúria mecânica causada por Stipa spp. (flechilha) em ovinos no Uruguai. Os animais, principalmente os cordeiros, apresentavam grande quantidade dos frutos de flechilha incrustadas na lã e alguns desses se introduziam na pele, panículo adiposo e músculo cutâneo do tronco causando dermatite e paniculite multifocal difusa.

Padrões de distribuição geográfica das espécies de Stipa L. (Poaceae-Stipeae) ocorrentes no Brasil

No Brasil ocorrem 22 espécies de Stipa, com maior diversidade no Rio Grande do Sul, onde todas estão presentes, 12 destas atingindo Santa Catarina, sete o Paraná e apenas uma espécie, S. sellowiana Nees ex Trin. & Rupr., alcançando os campos de altitude da Serra da Mantiqueira, em Minas Gerais, limite norte de distribuição do gênero e da tribo Stipeae no Brasil. O trabalho apresenta uma análise da distribuição geográfica destas espécies, fornecendo mapas com os diferentes padrões de distribuição encontrados.

Plantas que causam alterações mecânicas ou traumáticas em ruminantes e equinos, com ênfase em Stipa spp. (Gramineae)

Várias plantas podem provocar algum tipo de injúria mecânica. Entre elas as que causam traumatismo da pele ou mucosas, e as que causam alterações do sistema digestório, incluindo obstrução esofágica, sobrecarga ruminal e obstrução intestinal. Neste trabalho são revisadas algumas plantas que causam essas alterações e é descrito um surto de injúria mecânica causada por Stipa spp. (flechilha) em ovinos no Uruguai. Os animais, principalmente os cordeiros, apresentavam grande quantidade dos frutos de flechilha incrustadas na lã e alguns desses se introduziam na pele, panículo adiposo e músculo cutâneo do tronco causando dermatite e paniculite multifocal difusa.

Assessment of species diversity and state of "Stipa tenacissima" steppes

North African steppes are subjected to extreme degradation resulting in the reduction of their surface, genetic erosion of resources, and decrease in biodiversity. "Stipa tenacissima" steppes, which constitute one of the most representative vegetation types in the driest areas of the Mediterranean basin, are continuously degrading. With the aim of contributing to a better knowledge of the floristic composition and diagnosing the state of degradation of these steppes, we conducted a phytoecological analysis of 10 "S. tenacissima" sites in Tunisia. Floristic inventory compiled a systematic list of 46 vascular plant species belonging to 43 genera and 26 families. Species richness ranged from 4 to 18 species per 900 m2. Total vegetation cover was moderate and fluctuated between 22.8% and 49.9%. Our results revealed also a decreasing trend in species richness with increasing elevation (ρ = –0.585). Indeed, species richness was negatively correlated with slope (ρ = –0.19) and positively correlated with sand content (ρ = 0.262). Biological types were dominated by chamaephytes; this chamaephytization is due to the phenomenon of aridization and overgrazing. Moreover, the low species cover and the appearance of nonpalatable species highlighted the vulnerability of these steppes to degradation.

Contribution a l’identification des principaux facteurs de degradation des steppes a Stipa tenacissima du sud-ouest Algerien

La steppe algérienne est confrontée depuis plusieurs décennies à un problème de dégradation induit par l’effet combiné de facteurs anthropiques et naturels. Les résultats obtenus dans la lutte contre ce phénomène, malgré les moyens mobilisés, restent très mitigés et révèlent l’inefficacité des approches et méthodes adoptées. Toute action de préservation et de réhabilitation de la steppe doit reposer dans un premier temps sur un diagnostic permettant d’identifier et d’évaluer le poids de chaque facteur dégradant. Parmi les facteurs souvent soulignés on note le climat, le parcours, le défrichement et la pratique d’une agriculture pluviale sans une justification ni estimation de cet impact. Le diagnostic ciblant et classant les principaux facteurs de régression des formations steppique de Stipa tenacissima est l’objectif assigné à cette publication. La démarche retenue traitera de l’état des formations steppiques face aux pressions pour une identification des facteurs causaux de cette situation et une évaluation de leur impact futur.

Cambios en la vegetacion de un campo abandonado despues de un cultivo de trigo

La vegetación prístina de los campos altos del sur de Santa Fe (Argentina) son distintos tipos de flechillares caracterizados por la abundancia de varias especies del género Stipa. Cuando un campo agrícola se abandona suele revertir a las comunidades prístinas. El objeto de este trabajo es analizar los diez primeros años de la sucesión secundaria de un campo sometido a agricultura durante largo tiempo que se abandonó después de un cultivo de trigo (Triticum aestivum). En el primer año aparece trigo acompañado de malezas anuales (Chenopodium album y Portulaca oleracea); después del primer año una parcela fue colonizada por Baccharis salicifolia y las otras por Carduus acanthoides, Cerastium glomeratum, Ammi majus, etc. Los últimos años constituyen una etapa en la que disminuye la diversidad y se establece una fuerte dominancia de Baccharis salicifolia o Carduus acanthoides. El Sorgo de Alepo (Sorghum halepense) aparece en las etapas tempranas y perdura durante todo el período con valores altos de abundancia. Aún, prácticamente no han aparecido especies de los flechillares, por lo tanto se concluye que no ha transcurrido suficiente tiempo para que se regenere el flechillar, o porque sus especies no se encuentran en los bancos de semillas o en las proximidades.

Externalities of Shipping in the Gulf of Finland until 2015

During the last few years, the discussion on the marginal social costs of transportation has been active. Applying the externalities as a tool to control transport would fulfil the polluter pays principle and simultaneously create a fair control method between the transport modes. This report presents the results of two calculation algorithms developed to estimate the marginal social costs based on the externalities of air pollution. The first algorithm calculates the future scenarios of sea transport traffic externalities until 2015 in the Gulf of Finland. The second algorithm calculates the externalities of Russian passenger car transit traffic via Finland by taking into account both sea and road transport. The algorithm estimates the ship-originated emissions of carbon dioxide (CO₂), nitrogen oxides (NO_x), sulphur oxides (SO_x), particulates (PM) and the externalities for each year from 2007 to 2015. The total NOx emissions in the Gulf of Finland from the six ship types were almost 75.7 kilotons (Table 5.2) in 2007. The ship types are: passenger (including cruisers and ROPAX vessels), tanker, general cargo, Ro-Ro, container and bulk vessels. Due to the increase of traffic, the estimation for NO_x emissions for 2015 is 112 kilotons. The NO_x emission estimation for the whole Baltic Sea shipping is 370 kilotons in 2006 (Stipa & al, 2007). The total marginal social costs due to ship-originated CO₂, NO_x, SO_x and PM emissions in the GOF were calculated to almost 175 million Euros in 2007. The costs will increase to nearly 214 million Euros in 2015 due to the traffic growth. The major part of the externalities is due to CO₂ emissions. If we neglect the CO2 emissions by extracting the CO₂ externalities from the results, we get the total externalities of 57 million Euros in 2007. After eight years (2015), the externalities would be 28 % lower, 41 million Euros (Table 8.1). This is the result of the sulphur emissions reducing regulation of marine fuels. The majority of the new car transit goes through Finland to Russia due to the lack of port capacity in Russia. The amount of cars was 339 620 vehicles (Statistics of Finnish Customs 2008) in 2005. The externalities are calculated for the transportation of passenger vehicles as follows: by ship to a Finnish port and, after that, by trucks to the Russian border checkpoint. The externalities are between 2 – 3 million Euros (year 2000 cost level) for each route. The ports included in the calculations are Hamina, Hanko, Kotka and Turku. With the Euro-3 standard trucks, the port of Hanko would be the best choice to transport the vehicles. This is because of lower emissions by new trucks and the saved transport distance of a ship. If the trucks are more polluting Euro 1 level trucks, the port of Kotka would be the best choice. This indicates that the truck emissions have a considerable effect on the externalities and that the transportation of light cargo, such as passenger cars by ship, produces considerably high emission externalities. The emission externalities approach offers a new insight for valuing the multiple traffic modes. However, the calculation of the marginal social costs based on the air emission externalities should not be regarded as a ready-made calculation system. The system is clearly in the need of some improvement but it can already be considered as a potential tool for political decision making.

Vascular Plants and Biocrusts Modulate How Abiotic Factors Affect Wetting and Drying Events in Drylands

Understanding how organisms control soil water dynamics is a major research goal in dryland ecology. Although previous studies have mostly focused on the role of vascular plants on the hydrological cycle of drylands, recent studies highlight the importance of biological soil crusts formed by lichens, mosses, and cyanobacteria (biocrusts) as a major player in this cycle. We used data from a 6.5-year study to evaluate how multiple abiotic (rainfall characteristics, temperature, and initial soil moisture) and biotic (vascular plants and biocrusts) factors interact to determine wetting and drying processes in a semi-arid grassland from Central Spain. We found that the shrub Retama sphaerocarpa and biocrusts with medium cover (25–75%) enhanced water gain and slowed drying compared with bare ground areas (BSCl). Well-developed biocrusts (>75% cover) gained more water, but lost it faster than BSCl microsites. The grass Stipa tenacissima reduced water gain due to rainfall interception, but increased soil moisture retention compared to BSCl microsites. Biotic modulation of water dynamics was the result of different mechanisms acting in tandem and often in opposite directions. For instance, biocrusts promoted an exponential behavior during the first stage of the drying curve, but reduced the importance of soil characteristics that accentuate drying rates. Biocrust-dominated microsites gained a similar amount of water than vascular plants, although they lost it faster than vascular plants during dry periods. Our results emphasize the importance of biocrusts for water dynamics in drylands, and illustrate the potential mechanisms behind their effects. They will help to further advance theoretical and modeling efforts on the hydrology of drylands and their response to ongoing climate change.

Chemical anlysis of plant communities from Southern Italy

A phytosociological study was conducted in the National Park of Alta Murgia in the Apulia region (Southern Italy) to determine the adverse effects of metal contamination of soils on the distribution of plant communities. The phytosociological analyses have shown a remarkable biodiversity of vegetation on non-contaminated soils, while biodiversity appeared strongly reduced on metal-contaminated soils. The area is naturally covered by a wide steppic grassland dominated by Stipa austroitalica Martinovsky subsp. austroitalica. Brassicaceae such as Sinapis arvensis L. are the dominating species on moderated contaminated soils, whereas spiny species of Asteraceae such as Silybum marianum (L.) Gaertn. and Carduus pycnocephalus L. subsp. pycnocephalus are the dominating vegetation on heavily metal-contaminated soils. The presence of these spontaneous species on contaminated soils suggest their potential for restoration of degraded lands by phytostabilization strategy.