Landsliding related to land-cover change: A diachronic analysis of hillslope instability distribution in the Sierra Norte,Puebla, Mexico

This study examines mass movement associated with land use change, particularly deforestation, from multiple perspectives. The significance of such understanding is related to the degree of impact landsliding may cause on human settlements and economic activities, and on forest ecosystems. In this paper, the distribution of hillslope instability in the Sierra Norte, Puebla, Mexico is addressed by means of a diachronic analysis, which involves the development of vegetation indexes, as well as vegetation fragmentation derived from Landsat-5 (TM) and Landsat-7 (ETM+) satellite images from 1989 and 1999, respectively. The time period was chosen to compare vegetation cover conditions prior and after the extreme October 1999 rainfall event that triggered hundreds of slope failures in the study area. Results suggested there was a significant vegetation reduction from 1989 to 1999, which was strongly expressed by an increase of 809 km² of bare surfaces. Additionally, areas with highest vegetation density (91–100%) decreased considerably, from 1245 to 363 km², resulting in a net vegetation reduction of 70%. Furthermore, it was possible to highlight that landslide concentration was much higher on surfaces that were bare and had low vegetation density (0–50%), representing 85% of hillslope instability, than on surfaces having a greater density of vegetation cover. Land use change and land degradation are precursors to environmental hazards, such as mass movement events, that pose serious threats to regional population distributions and economic vitality.     

Uptake and translocation of iron from ferrated rhodotorulic acid in tomato

Micro‐organisms may develop an iron‐deficiency stress when grown in an alkaline environment and secrete ferric‐specific chelators known as siderophores. Some of these siderophores may have stability constants which can exceed 30. This is comparable to the synethetic Fe chelate FeEDDHA. Our objective was to determine if the Fe‐efficient T3238 FER tomato and the Fe‐inefficient T3238 fer tomato could use iron supplied as the siderophore ferrated‐rhodotorulic acid. After these two tomato cultivars were grown with adequate nutrition to obtain plants large enough for experimental testing, they were grown without iron until Fe‐deficiency‐stress symptoms developed and then iron was supplied as ferrated‐rhodoturulic acid. Iron efficient T3238 FER tomato utilized iron supplied as the siderophore and greened whereas, the Fe‐inefficient T3238 fer tomato plants were chlorotic because they could not use the iron in the siderophore. This study demonstrated that some higher plants subjected to various degrees of iron‐deficiency stress in nutrient culture may derive their iron requirement from siderophores of microbial origin.     

Predicting runoff from semi-arid hillslopes as source areas for water harvesting in the Sierra de Gador, southeast Spain

The effectiveness of water harvesting systems collecting surface runoff form rangeland hillslopes in semi-arid regions is difficult to predict, since the hydrological response at the outlet depends on the heterogeneity of hydrological processes. The lack of continuous runoff pathways, due to the irregular spatial patterns of soil properties and the variety of antecedent soil moisture conditions directly influence runoff generation and control discharge into the water harvesting cisterns. The aim of this paper is to evaluate the effectiveness of semi-arid hillslopes in generating runoff for water harvesting systems. Runoff was estimated by the STREAM expert-based model which was applied to three semi-arid hillslopes (0.4 to 6 ha). On the one hand the STREAM model rules were adapted to the regional conditions i.e. an antecedent precipitation index was adjusted to local soil moisture conditions and the rainfall duration was defined as the total rainfall event quantity and the effective rainfall duration (P_tot/t_eff). On the other hand, the distribution of rock outcrop and vegetation cover along the slopes was used to define homogeneous hydrological units. Final infiltration capacities were attributed to these hydrological units based on values found in the literature. The prediction performances are acceptable for the three water harvesting systems with an RMSE of 13.9 m³. It was shown that the rainfall/runoff model was more sensitive to the duration of the storm than to the antecedent soil moisture conditions. The use of a unique set of hydrological parameters for the three water harvesting systems on representative hillslopes allows the runoff prediction from any rangeland hillslope within the same region. Furthermore, the spatial patterns of soil surface characteristics are crucial for collecting runoff at the outlet of the system. Model runs demonstrated that degradation of vegetation and sealing of very small areas within flow paths can lead to an increase of annual runoff by as much as a factor two.     

Labile, recalcitrant, and microbial carbon and nitrogen pools of a tallgrass prairie soil in the US Great Plains subjected to experimental warming and clipping

Carbon (C) and nitrogen (N) fluxes are largely controlled by the small but highly bio-reactive, labile pools of these elements in terrestrial soils, while long-term C and N storage is determined by the long-lived recalcitrant fractions. Changes in the size of these pools and redistribution among them in response to global warming may considerably affect the long-term terrestrial C and N storage. However, such changes have not been carefully examined in field warming experiments. This study used sulfuric acid hydrolysis to quantify changes in labile and recalcitrant C and N fractions of soil in a tallgrass prairie ecosystem that had been continuously warmed with or without clipping for about 2.5 years. Warming significantly increased labile C and N fractions in the unclipped plots, resulting in increments of 373 mg C kg⁻¹ dry soil and 15 mg N kg⁻¹ dry soil, over this period whilst clipping significantly decreased such concentrations in the warmed plots. Warming also significantly increased soil microbial biomass C and N in the unclipped plots, and increased ratios of soil microbial/labile C and N, indicating an increase in microbial C- and N-use efficiency. Recalcitrant and total C and N contents were not significantly affected by warming. For all measured pools, only labile and microbial biomass C fractions showed significant interactions between warming and clipping, indicating the dependence of the warming effects on clipping. Our results suggest that increased soil labile and microbial C and N fractions likely resulted indirectly from warming increases in plant biomass input, which may be larger than warming-enhanced decomposition of labile organic compounds.     

Mechanism of salt tolerance in the grass species,Anneurolepidium chinense

The salt-tolerant grass plant, Anneurolepidium chinense, is commonly used for grazing in Northeast China and Inner Mongolia. The plants were grown in water culture and salt tolerance was evaluated in a greenhouse. The plants survived upon exposure to 500 mM NaCI salinity and developed stolons to produce daughter plants. Under 100 and 200 mM NaCI salinity, the plants accumulated mainly K+ to maintain the osmotic pressure of the young leaf blades. Betaine and reducing sugars were also the major constituents of the solutes that accumulated under saline conditions.     

Gully erosion associated with the expansion of unterraced almond cultivation in the coastal Sierra de Lujar,S. Spain

Since Moorish times, the lower slopes of the Sierra de Lujar in southern Spain have been intensively cultivated. Despite steep slopes and the highly erodible nature of the local micaschist/quartzite bedrock and derivative Quaternary sequences, accelerated erosion has largely been contained throughout this history by substantial, well-maintained rock terraces. However, since 1987, European Union (EU) agricultural policy has been to encourage the cultivation of certain crops by subsidising their expanded cultivation on a ‘per hectare’ basis. This has resulted in hasty clearance of native Mediterranean matorral on sites really unsuitable for the local staple crop (almonds), and erosion-prevention terraces are often absent or rudimentary. Gullying is now a very serious problem on some of these newly cleared sites. This paper identifies the lithological, topographic and agricultural policy controls on the consequent gully distribution, and then explores the pedological and hydrological controls on gully initiation on a single unterraced slope. Using these results alongside morphological data from gully surveys, a gully initiation and growth model is presented. This suggests that two types of gully are present in the area. ‘Type 1’ or upper-slope gullies are initiated by overland flows, which are relatively infrequent. By contrast, ‘type 2’ or slope-base gully initiation involves saturation and collapse in fossil landslip scars in Holocene colluvium. These two very different morphological systems may integrate through the terminal fan of the upslope gullies, in a manner described by Tiexeira de Oliveira 1990. The implications of this are that in the study area, sediment removal is associated with a very few highly productive sites. Contemporary management is briefly assessed against this model of geomorphic change in the area.     

Mineral composition and growth responses of tomato (Solanum lycopersicum L.) plants to irrigation with produced waters from the oil industry

Produced waters are considered a byproduct from the oil industry that may contain mineral elements essential for plant nutrition, which enables them for irrigation purposes. Due to the growing demand for water for agricultural use in the world, the aim of this study was to determine the feasibility of using dilutions of fresh water and produced water derived from the gas-producing zone of Sabinas-Piedras Negras, in northern México and their effect on mineral content and allocation, growth, and yield of tomato plants. The results showed that the dilutions containing produced water reduced fruit, stem, and leaf fresh weight, and that the uptake and accumulation of minerals in plant tissues, except for sodium, was also decreased. However, plants irrigated with dilutions of produced and fresh water showed increased translocation of essential minerals from the leaves to the fruit, which partially contributed to alleviate the negative effects on fruit yield.     

Using traits of species to understand responses to land use change: Birds and livestock grazing in the Australian arid zone

The expansion of the artificial water-point network and livestock grazing in arid and semi-arid Australia has significantly increased access to water by water limited herbivores and thus has potential to seriously negatively affect the unique endemic flora and fauna. We examined the effects of the expansion of the water-point network on the arid and semi-arid zone bird community, using data from the Atlas of Australia bird surveys of 1977-1981 and 1996-2001. We examined whether traits of species could be used to uncover the critical ecological processes altered by this land use change. We detected large scale declines in individual species. Species reliant on water for nesting and feeding declined more than other groups in the presence of high water-point density, likely through direct effects of livestock degrading habitat of both natural and artificial water points. The arid zone has no natural hoofed animals and livestock have significant impacts. Species that forage and nest on the ground also showed large declines, likely because of trampling and removal of vegetation by livestock and potentially through the indirect effect of water limited predators, dingos and foxes, expanding their ranges in response to the expanding network of water points in the landscape. This result was also apparent at large spatial scales so that these local-scale responses to water points translate into continental-scale population declines. Using traits of species to understand declines of bird species helped us to uncover which critical changes associated with the expansion of the water-point network most affected the bird community and therefore which species are most at risk.     

Microbial community structure and characteristics of the organic matter in soils under Pinus sylvestris, Picea abies and Betula pendula at two forest sites

 Microbial biomass C (C_mic), C mineralization rate, phospholipid fatty acid (PLFA) profiles and community level physiological profiles (CLPPs) using Biolog were determined from the humus and mineral soil layers in adjacent stands of Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and silver birch (Betula pendula Roth) at two forest sites of different fertility. In addition, the Fourier-transformed infrared (FTIR) spectra were run on the samples for characterization of the organic matter. C_mic and C mineralization rate tended to be lowest under spruce and highest under birch, at the fertile site in all soil layers and at the less fertile site in the humus layer. There were also differences in microbial community structure in soils under different tree species. In the humus layer the PLFAs separated all tree species and in the mineral soil spruce was distinct from pine and birch. CLPPs did not distinguish microbial communities from the different tree species. The FTIR spectra did not separate the tree species, but clearly separated the two sites. Received: 3 December 1999     

Microbial biomass,N mineralization,and the activities of various enzymes in relation to nitrate leaching and root distribution in a slurry-amended grassland

High rates of cattle slurry application induce NO _inf3 ^sup- leaching from grassland soils. Therefore, field and lysimeter trials were conducted at Gumpenstein (Austria) to determine the residual effect of various rates of cattle slurry on microbial biomass, N mineralization, activities of soil enzymes, root densities, and N leaching in a grassland soil profile (Orthic Luvisol, sandy silt, pH 6.6). The cattle slurry applications corresponded to rates of 0, 96, 240, and 480 kg N ha^-1. N leaching was estimated in the lysimeter trial from 1981 to 1991. At a depth of 0.50 m, N leaching was elevated in the plot with the highest slurry application. In October 1991, deeper soil layers (0–10, 10–20, 20–30, 30–40, and 40–50 cm) from control and slurry-amended plots (480 kg N ha^-1) were investigated. Soil biological properties decreased with soil depth. N mineralization, nitrification, and enzymes involved in N cycling (protease, deaminase, and urease) were enhanced significantly (P<0.05) at all soil depths of the slurry-amended grassland. High rates of cattle slurry application reduced the weight of root dry matter and changed the root distribution in the different soil layers. In the slurry-amended plots the roots were mainly located in the topsoil (0–10 cm). As a result of this study, low root densities and high N mineralization rates are held to be the main reasons for NO _inf3 ^sup- leaching after heavy slurry applications on grassland.     

Using DNA from museum specimens to preserve the integrity of evolutionarily significant unit boundaries in threatened species

Use of DNA from museum samples is a powerful tool to directly establish historical ESU boundaries in areas where populations of a species have been extirpated. The brush-tailed rock-wallaby (Petrogale penicillata) has suffered extensive reductions in range and population size since European settlement in Australia. Populations of this species have been grouped into three putative evolutionarily significant units (ESUs) which were likely once contiguous along the south-east coast of Australia. However, there is currently a gap of ∼320 km between extant populations of the southern and central ESUs. Conservation plans for the brush-tailed rock-wallaby include re-introductions of animals to locations within their former range. In order to preserve the historic geographic integrity of the genetic lineages within the species, it is necessary to map the boundary between the southern ESU and central ESU to allow more informed management decisions about which lineages should be used to re-stock specific geographic locations. We have extracted DNA from samples from museum specimens that come from locations between the southernmost extant colony of the central ESU and the remaining wild colony of the southern ESU. We sequenced a 177 bp interval of the left domain of the mitochondrial DNA control region and used phylogenetic analysis to group obtained sequences with previously published sequences belonging to the three ESUs. We have extended the range of the central ESU southwards and the range of the southern ESU northwards such that the gap between the ESUs is now approximately 160 km. We recommend that, where suitable historical museum collections exist, this technique be incorporated into re-introduction plans for other threatened species.     

A review of allodiversity in Lake Naivasha, Kenya: Developing conservation actions to protect East African lakes from the negative impacts of alien species

The biodiversity of developing countries is increasingly threatened by introductions of invasive alien species. This study on the allodiversity in Lake Naivasha, Kenya reviews the pathways, establishment rates and outcomes of introduced species, and provides the basis for determining conservation actions that, if implemented, could prevent potentially harmful effects of similar events in other East African lakes. Introductions into Naivasha commenced in the 1920s with the release of a sport fish and have since produced an allodiversity of 23 species. This includes species that are no longer present (e.g., some tilapia species), presumed no longer present (e.g., the Nile perch Lates niloticus) or whose distribution is highly localised and ecologically neutral (e.g., the coypu Myocastor coypus). It also includes species that established successfully and invoked major changes in lake ecology (e.g., the red swamp crayfish Procambarus clarkii) and a species that is producing apparent economic benefits to the local population (i.e., the common carp Cyprinus carpio). The most frequent donor continents were the Americas and most species were the result of secondary introductions. The main introduction vector was active release that aimed to enhance fishery production. Alien species now dominate each main level of the lake’s food web and produce impacts that are rarely restricted to a single ecosystem service. With a few exceptions, the majority of introductions translate into socioeconomic costs that contribute to rising social conflicts and exacerbating poverty. Development of appropriate conservation management tools within a regulatory framework could help protect Naivasha from further damage and could be used elsewhere in East African lakes to ensure that subsequent introductions enhance ecosystem services without affecting biodiversity.     

Cultivation effects on biochemical properties, C storage and N natural abundance in the 0–5 cm layer of an acidic soil from temperate humid zone

Changes in some soil chemical, including ¹⁵N values, and biochemical properties (microbial C, FDA hydrolysis, glucosidase and urease activities) due to two tillage systems, conventional tillage (CT) and no-tillage (NT), were evaluated in an acid soil from temperate humid zone (NW of Spain) and compared with values obtained for a reference forest soil. The results showed that in the surface layer (0–5 cm depth) tillage tended to increase soil pH and to decrease organic matter levels and microbial biomass and activity values. The data also indicated that 8 years of NT, compared to CT, resulted in greater organic matter content and increased microbial biomass and activity, the changes being more pronounced for the microbial properties. Adoption of NT resulted in an increase of soil C storage of 1.24 Mg C ha⁻¹ year⁻¹ with regard to CT. The suitability of ¹⁵N as a potential tracer of land-use in this acid soil was also confirmed.     

Habitat quality, conspecific density, and habitat pre-use affect the dispersal behaviour of two earthworm species, Aporrectodea icterica and Dendrobaena veneta, in a mesocosm experiment

Dispersal capacity is a life-history trait that may have profound consequences for earthworm populations: it influences population dynamics, species persistence and distribution and community structure. It also determines the level of gene flow between populations and affects processes such as local adaptation, speciation and the evolution of life-history traits. It may play a great role in soil functioning by determining the spatial distribution of ecosystem engineers such as earthworms. Dispersal is an evolutionary outcome of the behaviour in response to the ecological constraints of the species. Hence different dispersal behaviour is expected from the different ecological types of earthworms. Nevertheless the dispersal behaviour of earthworms has been little documented.In this work we test a series of basic mechanisms that are fundamental and complementary to understand earthworms dispersal behaviour. We focus on the dispersal triggered by environmental conditions, a fundamental process usually termed “conditional dependent dispersal”. We show experimentally in mesocosms that in one week: 1) earthworm dispersal can be triggered by low habitat quality, either through soil quality or the presence/absence of litter. 2) Earthworms can be subject to positive density dependent dispersal, that is the rate of dispersal increases when density increases; and 3) earthworm dispersal can be reduced by the pre-use of the soil by conspecific individuals that are no longer present.Our results suggest that earthworms may be more mobile than expected from previous estimations, and that they present high capacities of habitat selection. In the light of our findings we elaborate a behavioural scenario of earthworm foraging, and propose several priority working directions.     

Growth,Root Characteristics,and Leaf Nutrients Accumulation of Four Faba Bean (Vicia faba L.) Cultivars Differing in Their Broomrape Tolerance and the Soil Properties in Relation to Salinity

The effects of salinity on four faba bean (Vicia faba L) cultivars [Giza 429, Giza 843, Misr 1 (Orobanche-tolerant), and Giza 3 (Orobanche-susceptible)] and soil properties were investigated in a pot experiment with addition of 0, 50, and 100 mM sodium chloride (NaCl) for 9 weeks. Salinity significantly decreased calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), bicarbonate (HCO₃ ^?), and sulfate (SO₄ ^2?) while significantly increasing sodium (Na⁺), chloride (Cl^?), pH, and electrical conductivity (EC; dS m^?1). Root length density (cm cm^?3), root mass density (mg cm^?3), total dry weight, and salt-tolerance indexes were significantly reduced as a result of application of salinity. The results presented support evidence on the positive relationship between Orobance tolerance and salt tolerance in the three cultivars (Giza 429, Giza 843, and Misr 1). This adaptation was mainly due to a high degree of accumulation of inorganic nitrogen (N), phosphorus (P), K⁺, Ca²⁺, and Mg²⁺ and lesser quantities of Na⁺ and Cl^?, as well as greater K⁺/Na⁺ and Ca²⁺/Na⁺ ratios.     

Exposure of coelomocytes from the earthworm Eisenia hortensis to Cu,Cd, and dimethylbenz[a]anthracene: An in vitro study examining reactive oxygen species production and immune response inhibition

The principal aims of this study were to investigate the in vitro effects of copper (Cu), cadmium (Cd) and the polycyclic aromatic hydrocarbon (PAH) dimethylbenz[a]anthracene (DMBA) on reactive oxygen species (ROS) production and the effect of DMBA on immune function (phagocytosis) in coelomocyte samples isolated from the earthworm Eisenia hortensis. Using a fluorogenic indicator of ROS, dihydrorhodamine 123, we show that earthworm coelomocytes are induced to produce significant increases in ROS when exposed to Cu or Cd at 32–250 μM, an effect diminished by the chelator ethylenediaminetetraacetic acid (EDTA). DMBA also induced significant ROS production in the range of 20–400 μM compared to controls. Testing the effect of DMBA on cellular immune mechanisms, we used a phagocytosis assay to reveal an immunosuppressive effect of DMBA (50–200 μM) on the capacity of hyaline amoebocytes to ingest fluorescent Escherichia coli. These studies illustrate the relative ease and efficiency of these in vitro procedures for testing the toxicological effects of environmental pollutants, including heavy metals and PAHs, using earthworm coelomocytes as indicators of oxidative stress and immune response impairment.     

Morphological variability and resource allocation in the annual teosinte (<Emphasis Type="Italic">Zea mays</Emphasis> ssp.<Emphasis Type="Italic"> mexicana</Emphasis> (Schrader) Iltis) of the Toluca Valley,Mexico

This study explores the morphological variability and resource allocation of weedy, annual teosinte (Zea mays ssp. mexicana (Schrader) Iltis, Chalco race) from the Valley of Toluca, central Mexico, and compares it with data reported for maize. One hundred mature and fertile teosinte plants were selected for variation in size and measured. The extremes found for fertile plants were 0.12 and 3.5 m in height and 0.09 vs. 694 g in weight. Fruit were polymorphic, with significant correlation between color and weight. Small plants invested slightly more biomass in the leaves and tall plants invested more in the stem. The minimum mass necessary to produce fertile plants was much lower in teosinte than in maize. Very small teosinte plants formed only female inflorescences, whereas maize produces a tassel. The harvest index was similar to landrace maize, and did not decrease in taller plants, as teosinte can increase the reproductive sink. Toluca teosinte retains several important characteristics of weeds: size variability, adaptation of fruit quantity to environmental conditions, and fruit polymorphism.     

Predator-prey relationships and responses of ungulates and their predators to the establishment of protected areas: A case study of tigers, leopards and their prey in Bardia National Park, Nepal

Interactions among sympatric large predators and their prey and how they respond to conservation measures are poorly known. This study examines predictions concerning the effects of establishing a protected area in Nepal on tigers (Panthera tigris), leopards (Panthera pardus), and their ungulate prey. Within a part of the park, after 22 years the total density of wild ungulates had increased fourfold, to ca. 200 animals/km², almost exclusively due to a remarkable increase in chital deer (Axis axis). Tiger density also increased markedly to nearly 20 animals/100 km², whereas leopard density did not and was ca. 5 animals/100 km². The prediction that grazers should increase more than browsers was only partially supported. The prediction of positive density dependence in prey selection was not supported. Instead, the most abundant species (chital and hog deer, Axis porcinus) were killed less frequently than expected, whereas the lower-density wild boar (Sus scrofa) was preferred. Predictions that (i) initially rare species suffer highest predation was partially supported, that (ii) predation is highest among the most abundant prey was not supported, and that (iii) predation is highest among the most preferred prey independently of their densities was supported. Clearly, the conservation efforts adopted in Bardia were successful, as both tigers and their natural prey base increased. However, the positive numerical response of tigers limited and depressed the abundance of some prey species. Thus, conservation activities aimed at restoring large predators are likely to change in the composition of the overall mammal community, potentially eliminating rare but preferred prey species.     

Historical changes in the bird fauna at Coomooboolaroo, northeastern Australia, from the early years of pastoral settlement (1873) to 1999

Across most of northern Australia, the historical record is generally insufficient to serve as a baseline for interpreting the impacts of European settlement on fauna. A notable exception is the pastoral property Coomoobolaroo (454 km²) in central Queensland, where the ornithologist Charles Barnard maintained a detailed record of bird fauna from 1873 to 1933. We re-surveyed the property in 1999, and collated other information on its current avifauna, giving 242 species in total recorded over the period 1873-1999 (of which we had sufficient information to ascribe trends to 200 species). The bird fauna of Coomooboolaroo has undergone substantial change, across both of the periods 1873-1933 and 1934-1999. From 1873 to 1999, 45% of species declined or were lost from the property, compared with 13% of species that either colonised the property or increased. Most of the latter are widespread species or those known to benefit from clearing and land development. This extent of change appears at least as high as that reported for most comparable studies elsewhere in Australia, despite these being conducted at sites that have been subjected to superficially greater environmental degradation. The greatest rates of loss occurred among birds associated with softwood scrub (dry rainforest), grasslands and swamps. Smaller species were more susceptible to decline, but change in status was not significantly associated with foraging style nor different between residents and migrants. Many of the species that have declined at Coomooboolaroo have also declined in many other geographic regions, habitats and land-uses. Change in status at this property can be attributed to diverse factors, including changes in predation pressures; environmental change due to altered fire regimes and/or grazing by livestock; and vegetation clearance at both property and regional scales. The multiplicity and complex interrelationships of such factors renders it difficult to predict assemblage-level change.