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.     

Short-term compost effect on macroaggregation in a sandy soil under low rainfall in the valley of Mexico

Several studies have shown the importance of organic material in the formation and stability of soil aggregates. The organic matter of soil (SOM) is affected among other factors by the application of farmyard waste and compost, as well as tillage and crop rotation. This paper examines the aggregation and stability of a sandy soil (Haplic Fluvisol) in the valley of Mexico when treated with either 40 Mg ha⁻¹ of compost or urea (80 kg ha⁻¹ of N) and sown to amaranth (Amaranthus hypochondriacus L.) under dryland conditions. The application of compost resulted in a significantly larger proportion of aggregates in the fractions >1 mm (1.0–2.0, 2.0–2.3, 2.3–4.7 mm) than in the smaller fraction (<1 mm). However the stability of the macroaggregates >1 mm in the compost treatment was not higher than in contrasting treatments which did not include organic matter. Compost, which was applied under drought conditions, did not increase the aggregate stability of the soil probably because of the restricted transformation of the compost and microorganism activity.     

Growth and root architecture responses of zoysiagrass to changes in fertilizer nitrate : urea ratio

Although zoysiagrass (Zoysia spp.) responds to nitrogen (N) application in the field, especially during the establishment phase, no guidelines are available for the preferred form of N for these species. A greenhouse experiment was performed to see how zoysiagrass responds to nitrate and urea as N sources. Z. japonica cv. El Toro (fast‐growing) and cv. Meyer (slow‐growing) and Z. matrella cv. Zorro (fast‐growing) and cv. Diamond (slow‐growing) were chosen for this study. Plants were clonally propagated as phytomers, established in 21 cm deep cone‐tainers filled with a sand‐based growth medium. The treatment consisted of a modified, half‐strength Hoagland's solution with five different nitrate : urea ratios (100 : 0, 75 : 25, 50 : 50, 25 : 75, 0 : 100). Plant responses were assessed in terms of biomass production (leaf, culm, roots, and total plant dry weight) and rooting characteristics (length, area, diameter, volume, tips, forks, crossings, and root volume ratio) 10 weeks after the initiation of the experiment. The differing sources of N resulted in changes in plant growth and development. The cultivars had different above and below‐ground biomass and root architecture traits. El Toro had the highest total biomass production (2.083 g plant⁻¹ DW), while Meyer and Zorro together averaged 0.734 g plant⁻¹ DW (65% less than El Toro). Diamond was the least productive in terms of leaf, culm, and root biomass (0.278 g plant⁻¹ DW; 87% less than El Toro). Furthermore, above‐ and below‐ground DW production was greatest following treatment with 25 : 75 nitrate:urea, whereas 100% nitrate produced plants with the lowest DW. Zoysiagrass rooting traits were only minimally influenced by N source; as the concentration of urea increased, slight increases in root surface area and volume were observed, accompanied by a decline in the root volume ratio.     

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.     

高寒地区燕麦 (Avena sativa L.) 人工草地生物量分配对施肥和混播措施的响应

【目的】了解高寒地区燕麦人工草地生物量分配格局对燕麦品种、施肥措施和混播水平的响应机制,为高寒地区人工草地建植提供依据。 【方法】采用“三因素四水平”正交试验设计,包括 4 个燕麦品种,分别为青燕 1 号、林纳、青海 444、青海甜燕麦;4 种施肥措施,分别为不施任何肥料 (CK₀)、尿素 75 kg/hm2 + 磷酸二铵 150 kg/hm2 (NP)、有机肥 1500 kg/hm2 (OM) 和尿素 37.5 kg/hm2 + 磷酸二铵 75 kg/hm2 + 有机肥 750 kg/hm2 (NP + OM);4 个箭筈豌豆混播水平,分别为 0、45、60、75 kg/hm2,在燕麦拔节期、抽穗期、开花期和乳熟期分别对各处理燕麦和箭筈豌豆各器官生物量进行了测定。 【结果】燕麦人工草地地上生物量以青燕 1 号 (85.57%)、尿素 + 磷酸二铵 + 有机肥处理 (84.91%) 和 0 kg/hm2 混播水平 (85.81%) 时分配比例最高;地下生物量以林纳 (18.04%)、不施肥 (16.02%) 和 30 kg/hm2 混播水平 (16.29%) 时分配比例最高。茎、叶、穗和根生物量分配比例分别为 44%～48%、19%～24%、17%～22% 和 14%～18%。茎、叶、穗和地下生物量分配随季节分别呈增加、先降后增、增加和下降的变化趋势;在各因素影响下,燕麦生长前期以叶生长为主,中、后期以茎生长为主,而箭筈豌豆在生长前期以根生长为主,中、后期以叶生长为主。燕麦生物量分配在整个生育期处于优势地位,地上生物量分配始终高于地下,表现为异速生长关系。茎和地下生物量分配在生长前期和后期分别受施肥措施和品种的影响;叶生物量分配在整个生育期受混播水平的影响;燕麦穗生物量分配主要受品种和混播水平的影响。 【结论】品种、施肥措施和箭筈豌豆混播水平均对高寒地区燕麦人工草地生物量分配具有显著影响,选用青燕 1 号品种,单播,配施尿素 37.5 kg/hm2、磷酸二铵 75 kg/hm2、有机肥 750 kg/hm2 时地上生物量分配最高;选用林纳,并混播 30 kg/hm2 的箭筈豌豆,采用不施肥措施时地下生物量分配最高。     

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.     

过量铜在两个柑橘品种幼苗中的分布特征及根细胞壁响应机制

  【目的】  探究过量铜在两个柑橘品种幼苗组织水平和亚细胞水平上的分布特征以及根细胞壁对铜毒害的响应机制,以揭示柑橘耐铜毒害机理,为优化不同柑橘品种铜养分管理提供科学依据。  【方法】  以砂培的雪柑(Citrus sinensis)和沙田柚(Citrus grandis)实生苗为试验材料,进行连续18周不同浓度铜处理,即Cu 0.5 μmol/L (对照)和300 μmol/L (过量铜)。处理结束后,分析铜在柑橘幼苗不同组织水平(主根、侧根、茎和叶)、侧根亚细胞水平(细胞壁、细胞器和可溶性部分)以及侧根细胞壁多糖组分(果胶、半纤维素Ⅰ、半纤维素Ⅱ和纤维素)上的分布特征;采用透射电镜(TEM)以及傅里叶变换红外光谱(FTIR),分析柑橘侧根细胞壁微结构变化(厚度、化学基团构成等)。  【结果】  1) 组织水平上,不论是对照还是过量铜处理的柑橘苗,侧根是铜分布的主要部位,且过量铜处理的沙田柚侧根铜含量显著高于雪柑。对照组的雪柑和沙田柚侧根铜分布率分别为57.32%和51.31%;过量铜处理后,雪柑和沙田柚侧根铜分布率分别提高到90.87%和91.99%。相反,过量铜处理显著降低了两个柑橘品种幼苗茎和叶的铜分布率。2) 在侧根亚细胞水平上,细胞器是铜在对照组柑橘苗的主要分布部位。对照组的雪柑和沙田柚侧根细胞器铜分布率分别为58.61%和39.26%;过量铜处理后,雪柑和沙田柚侧根细胞器的铜分布率分别降低到14.34%和11.49%。与对照相比,过量铜处理显著提高了两个柑橘品种幼苗侧根细胞壁和可溶性部分的铜含量,且过量铜处理的沙田柚侧根细胞壁铜含量显著高于雪柑。3)与对照相比,过量铜处理显著提高了两个柑橘品种幼苗侧根细胞壁各多糖组分的铜含量。其中,对照组的雪柑和沙田柚侧根细胞壁果胶铜分布率分别为44.69%和37.15%;过量铜处理后,雪柑和沙田柚侧根细胞壁果胶铜分布率分别提高到98.45%和98.48%。但过量铜处理的两个柑橘品种幼苗侧根细胞壁上的半纤维素Ⅰ、半纤维素Ⅱ和纤维素中的铜分布率显著降低。4)分级提取细胞壁并结合TEM分析表明,过量铜处理显著提高两个柑橘品种幼苗侧根细胞壁的提取率以及细胞壁厚度,且过量铜处理的沙田柚细胞壁提取率与细胞壁厚度均显著高于雪柑。5) FTIR分析表明,沙田柚侧根细胞壁果胶、纤维素和蛋白质等成分上羟基、羧基和氨基官能团参与了铜的吸附和固定。  【结论】  亚细胞水平上,300 μmol/L过量铜处理的柑橘苗侧根可溶性部分和细胞壁是铜的主要分布部位,细胞壁果胶对铜的固定降低了铜向地上部的运输。提高细胞壁含量、增厚细胞壁以及促进细胞壁对铜的吸附可能是沙田柚幼苗耐铜性强于雪柑的主要原因。     

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.     

Effect of silicon on the alleviation of boron toxicity in wheat growth,boron accumulation,photosynthesis activities,and oxidative responses

Little is known about the alleviation of boron (B) toxicity in wheat induced by silicon (Si), especially on the photosynthesis properties and antioxidative responses. The purpose of this research was to evaluate the effect of Si on the toxicity of B in wheat and the related mechanisms. A greenhouse pot experiment was conducted using wheat (Triticum aestivum Linn.) at the early seedling stage. Boric acid was added to soil to create three B concentrations. Each B treatment consisted of two Si treatment including control and Si application. Our results show that Si has an alleviative effect on B toxicity in wheat plant. Si showed significant alleviative effect on wheat growth at 150 mg B kg^?1 whereas did not show significant alleviative effect at 300 mg B kg^?1. Under B stress, plant dry weight of wheat was reduced and the reduction was alleviated by Si. However, plant tissue B accumulation was not reduced by the application of Si. Net photosynthetic rates of wheat were not influenced significantly by B or Si. The oxidative damages in wheat that were caused by excess B were not significantly alleviated by Si. These results suggest that the effect of Si on B toxicity in wheat is still controversial and more studies need to be conducted.     

Responses of carbon,nitrogen and phosphorus to two consecutive drying–rewetting cycles in soils

Drying and rewetting cycles are known to be important for the dynamics of carbon (C), phosphorus (P), and nitrogen (N) in soils. This study reports the short‐term responses of these nutrients to consecutive drying and rewetting cycles and how varying soil moisture content affects microbial biomass C and P (MBC and MBP), as well as associated carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions. The soil was incubated for 14 d during which two successive drying–rewetting episodes were imposed on the soils. Soils subjected to drying (DRW) were rewetted on the seventh day of each drying period to return them to 60% water holding capacity, whilst continually moist samples (M), with soil maintained at 60% water holding capacity, were used as control samples. During the first seven days, the DRW samples showed significant increases in extractable ammonium, total oxidized nitrogen, and bicarbonate extractable P concentrations. Rewetting after the first drying event produced significant increases only in CO₂ flux (55.4 µg C g^?1 d^?1). The MBC and MBP concentrations fluctuated throughout the incubation in both treatments and only the second drying–rewetting event resulted in a significantly MBC decrease (416.2 and 366.8 mg kg^?1 in M and DRW soils, respectively). The two drying–rewetting events impacted the microbial biomass, but distinguishing the different impacts of microbial versus physical impacts of the perturbation is difficult. However, this study, having a combined approach (C, N, and P), indicates the importance of understanding how soils will react to changing patterns of drying–rewetting under future climate change.     

Terrestrial ciliates (Protozoa,Ciliophora) from two islands (Gough,Marion) in the southern oceans,with description of two new species,Arcuospathidium cooperi and Oxytricha ottowi

Twenty-seven soil and moss samples from Gough Island (40°21′S, 09°53′E) and Marion Island (46°52′S, 37°51′E), two small volcanic elevations in the South Atlantic and southern Indian Oceans, were investigated for ciliated protozoa using the non-flooded Petri dish method. Collections were made from a variety of biotopes covering most principal soil and vegetation types. Sixty species were found, 39 on each of the two islands studied; all are first records for these regions. The mean number of species per sample was markedly higher on Gough (14) than on Marion Island (5.7), reflecting increased climatic severity and decreased soil fertility, respectively. Grassland with a well developed soil cover supported more species than sites with sparse vegetation or heavily eutrophic penguin-influenced habitats. Colpodids dominated the frequency spectrum due to their r-selected survival strategy. The most common species were Colpoda steinii, a euryoecious bacteria feeder, and Pseudoplatyophrya nana, an obligate fungal sucker, also belonging to the Colpodea. Species were very patchily distributed, probably due to the environmental severity allowing few pioneers to establish stable populations. Hemimastix amphikineta, a peculiar heterotrophic flagellated organism, was found on Gough Island, an observation that supports the restricted Gondwanian distribution previously proposed for this species. Two new species were found. Arcuospathidium cooperi n. sp., a gymnostome ciliate, was discovered on Marion Island and belongs to a small group of spathidiids lacking extrusomes. Oxytricha ottowi n. sp., a hypotrichous ciliate, was discovered on Gough Island and is unique in having eight macronuclear nodules.     

Tree species diversity,species regeneration and biological productivity of seeded Acacia catechu Willd. In rehabilitated limestone mines in the North West Indian Himalayas

Degraded sites like mine spoils on hillslopes are characterized by poor soil physico‐chemical environments and instability. Reclamation of such areas using low cost bioengineering and vegetative methods were carried out in an abandoned limestone mine in the lower western Indian Himalayas and the impact of these measures on vegetation diversity, secondary succession and growth of seeded Acacia catechu Willd. after two decades of protection are reported in this paper. Results reveal that introduction of fast growing leguminous species affected species diversity and hampered the regeneration and growth of native vegetation, due to the dense shade of the over‐storey component. Species diversity (H') levels increased with the opening of the canopy at different elevations, with the highest diversity (1·624) being recorded on the hilltop with Acacia catechu and Wedlandia exserta dominating the area. Enumeration of various species in the growth stages indicated a large population in the pole stage followed by tree and sapling stage indicating scattered regeneration mostly by 1‐2 species. Tree associations in the lower, middle and upper reaches were of Leucaena leucocephala—A. catechu, A. catechu—Boehemeria rugulosa and A. catechu‐W. exserta, respectively. Seeded A. catechu plants now in the tree stage have attained an average height of 5·5 m and dbh of 10·44 cm with an average wood volume of 0·027 m³ in a period of 16–21 years. At current prices of heartwood (US $435 per m³) of A. catechu which is used in the manufacture of ‘kattha’, the investments made two decades ago (US$ 13043) in the rehabilitation of the limestone mine are fairly justified. Copyright © 2010 John Wiley & Sons, Ltd.     

Response of Amaranthus cruentus cv Mexicano to nitrogen fertilization under irrigation in the temperate,semiarid climate of North Patagonia,Argentina

This article explores the response of three genotypes of Amaranthus to different sowing date and to different doses of nitrogen (N) fertilization. The experimental design was a randomized complete block design with three replicates for cultivars, planting date and fertilization per treatment. Mexicano sown in early December had the best yield (5285?kg ha^-1) with highly significant differences (p?<?0.001) respect to Dorado and Antorcha. To assess the N fertilization Mexicano cultivar was sown at the end of spring (1 December). Morphophysiological variables increased as the N fertilization dose was raised. Higher doses of N fertilizer resulted in greater economic yields this was mainly due to the increase in grain number rather than that of a 1000 grain weight. The results of this investigation suggest that sowing Amaranthus cruentus cv Mexicano on 1 December with 150?kg N ha^?1 favors its general development and allows to obtain high economic and biological yields with an appropriate protein content.     

Field studies to assess the workable range of soils in the tropical zone of Veracruz, Mexico

In the tropical area of Veracruz (Mexico) the decision of when and how to carry out tillage operations is based on qualitative criteria. It often results in excessive and unnecessary work, energy waste, operational delay, soil exposure to water erosion and soil structural damage. Objective criteria are needed in this area for selecting when and how to do cultivation in order to meet crop and conservation requirements. The workable range of typical soils of the area (Haplic Pheaozems) was quantified by assessing in-field implement effects on the soil structure and measuring the specific energy applied by the tractor–implement combination. This was done over a range of soil moisture contents inside and outside the theoretical friable consistency state of the soils, determined by the shrinkage and plastic limits. Empirical relationships between initial moisture content and the technological result of tillage showed that these results for moist loam and clay soils shifted from optimum to poor at soil water potentials that coincides quite well with the plastic limit. However, as soil was drying out, the implement effect changed from optimum to sub-optimum at soil moisture contents well above the shrinkage limit, so the actual field workable range was smaller than the theoretical friable status of the soils. The minimum input of specific energy to obtain optimum results, was close to the soil water potential where results changed to sub-optimum as soils were drying out. To support decisions for tillage planning and operation, valuable information on workable periods can be obtained by making use of quantified workability thresholds.     

Sensitivity to cadmium of the standard test species Folsomia candida compared to two other species, Onychiurus yodai and Sinella umesaoi (Collembola)

Knowing whether test species used for single-species toxicity tests are representative of other species provides valuable information because contaminant effects are often extrapolated to the community level based on these tests. To evaluate how representative the sensitivity of the standard test collembolan species Folsomia candida is for Collembola, we devised toxicity tests using the collembolan species Onychiurus yodai and Sinella umesaoi, which exhibit life-forms different from F. candida. Sensitivity to cadmium (Cd) was compared between F. candida and the novel test species. The 50% effective concentrations for reproduction were 154.7, 72.2 and 40.9 mg Cd/kg dry soil for O. yodai, F. candida and S. umesaoi, respectively. Thus, the reproductive sensitivity of F. candida to Cd was between that of the other two species. Increasing reproductive sensitivity to Cd corresponded to increasing activity levels and a more surface-dwelling life-form. Our data may facilitate the generalisation of effect data for F. candida to other species.     

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