Arid Valley Research Articles

岷江干旱河谷25种植物一年生植株根系功能性状及相互关系

相同条件下相同生长期的植物根系生长与适应策略及其差异性还不清楚。因此,采集岷江干旱河谷地区25种乡土植物(木本15/草本10种)的种子于2009年3月播种在同一干旱环境中,9月测定了1年生植株的最大根深(RD_max)、根幅(RW)与根生物量(RB),计算了总根长(TRL)、比根长(SRL)及细/粗根生物量比(RB_f/c),分析了它们之间的关系,进行了根系功能组划分。结果表明:1) 25种植物1年生植株RD_max与RW变异较小,总变异率为14.9%和20.7%;TRL和SRL变异相对较大,分别为28.5%和34.7%,草本植物SRL明显大于木本植物;RB和RB_f/c种间变异较大,总变异率分别为50.1%和70.5%;2) 25种植物的RD_max、RW、RB和TRL间呈显著正相关关系,表明根系较深的物种RW较大,TRL和RB也较高;SRL与RD_max呈极显著负相关关系,与RB_f/c呈极显著正相关关系,表明根系垂直分布较浅的物种细根发达,SRL较大;3) 主成分分析显示,25种植物可分为3个功能组:第1组具有较大RD_max、RW和RB,资源利用持续时间较长;第2组具有较大TRL、SRL和RB_f/c,资源利用效率较高;第3组根系功能性状没有一致的突出特点,可能通过降低自身生理机能适应生存条件。综合分析表明,岷江干旱河谷区25种植物1年生植株根系的功能性状变异明显,可塑性大,历经长期自然选择压力而形成了不同的环境适应策略,但生长型并不必然表达出1年生植株根系功能性状的差异性。;The functional traits and distribution patterns of roots affect the amount of soil resources used by the plant. These functional traits can mirror plant ecological resource utilization strategies for capturing soil water and nutrients. Changes in root functional traits can affect important plant processes, including water- and nutrient-use efficiencies and the ability to compete for belowground resources. In this study, root functional traits and correlations among them were investigated in one-year-old plants of 25 species from the arid valley of Minjiang River. The specific objectives were to compare plants of the same age growing in the same conditions to assess the trade-offs among root functions based on correlations among different functional traits, and to define plant functional types and their adaptation strategies. Seeds of vascular plant species were pretreated and sown in March 2009 in a field at the Maoxian Station for Ecosystem Research, Chinese Academy of Science. Complete root systems were sampled by excavating the entire individual in September, 2009, when plants were one year old. We measured six root functional traits; root depth_max, root width, total root length, specific root length, total root biomass, and ratio of fine/coarse root biomass. We examined the specific ecological strategies of the 25 species in adapting to the same habitat by comparing and contrasting the individual trait range and testing relationships among root functional traits. There was relatively low variability among the 25 species in terms of root depth_max (14.9%) and root width (20.7%), but higher variability in total root length (28.5%) and specific root length (34.7%). The specific root length of herbaceous plants was markedly greater than that of woody plants. Among the 25 species, there were significant differences in root biomass (total variance ratio, 50.1%) and the ratio of fine/coarse root biomass (total variance ratio, 70.5%). At the species level, there were significant positive correlations among root depth_max, root width, total root length, and root biomass, indicating that plants with deeper roots generated greater root width, longer total root length, and greater root biomass. In addition, specific root length was significantly positively correlated with the ratio of fine/coarse root biomass but negatively correlated with root depth_max. These results indicated that plants with higher specific root length tended to generate more fine roots but a relatively shallow root system. The principal component analysis showed that the 25 species could be divided into three functional groups, explaining nearly 80% of the total variation. The first group had larger root depth_max, greater root width, and greater root biomass; the second group had greater total root length, greater specific root length, and larger ratio of fine/coarse root biomass; the third group did not show uniform patterns for any of the six functional traits. This comprehensive analysis revealed that there was variability in the individual root functional traits among 25 different species from the arid valley of Minjiang River, and that different functional types showed various environmental adaptation strategies. Species adapt to local water and nutrient conditions either by improving water- and nutrient-use efficiencies or by decreasing root performance functions. The life-form of a given species could not predict differences in functional root traits at the one-year-old growth stage.

Research on the Niche of Major Plant Population of the Barren Hillsides in the Arid Valley of the Upper Reach of the Minjiang River

The niche breadths and niche overlaps of Selaginella pulvinata and of other several main species of the herbaceous layer were measured at the barren hillsides in the arid valley of the upper reach of the Minjiang River. The results indicate that Selaginella pulvinata can distribute in various communities and adapt the environment of this region. Because all of them can express the highest ability to combat the draught and explore resources, the competitions among them can be found obviously. It is very useful for us to the vegetation recovery of the barren hillsides in the arid valley of the upper reach of the Minjiang River that had been damaged seriously by the 8.0 earthquake at 2:28pm on May 12th in Wenchuan, Sichuan Province, China.

Surface energy and water vapor fluxes observed in a desert plantation in central Iran

Summertime observations of surface radiation budget, energy balance and atmospheric surface layer meteorology were made on an arid valley floor planted with Haloxylon aphyllum to combat desertification in central Iran. The surface microclimate is characterized and compared with other arid regions and the role of ‘desert greening’ on surface fluxes is considered. A high surface albedo (0.265) and large longwave radiation loss produced relatively low net radiation. Energy partitioning was dominated by sensible and ground heat fluxes with opposing diurnal asymmetry governed by strong diurnal variability in eddy diffusivity. The Bowen ratio was 2.53, which fell inside the range of other vegetated arid surfaces. Surface temperature gradients were strong both in the atmospheric surface layer and in the substrate, with consistent lapse conditions by day and inversions at night. The wind regime included a moderate daytime regional wind which displayed Coriolis turning and weaker nocturnal slope flows. Actual evapotranspiration (1 mm dy −1) was only a small fraction of potential evapotranspiration. The diurnal pattern of AET indicates strong stomatal control. The desert greening effect of Haloxylon plantations provided atmospheric water and reduced sensible heat flux by up to 40%.

Distribution patterns of shrubby N‐fixers and non‐N fixers in an arid valley in Southwest China: implications for ecological restoration

AbstractShrubs play different key roles in arid regions. Comparisons of shrubs and their site adaptability are essential for correct selection of candidates in developing restoration theory and practice. A survey of topography, soil properties and shrub composition was conducted in fifty‐seven 5‐m × 5‐m plots in an arid valley of the upper Minjiang River, Southwest China. With cluster analysis and critical examinations based on edaphic properties, soil was classified into three groups: dry cinnamon soils (DCS), calcareous cinnamon soils (CCS) and eluvial‐accumulation cinnamon soils (EACS). EACS had the highest fertility level, DCS the next and CCS the lowest level. For non‐N fixers, soil moisture is the primary limiting factor, and nitrogen the next. However, N‐fixers are weakly constrained by soil moisture and nitrogen, the extent of which is species‐specific. N‐fixers had a significantly higher cumulative relative importance value (44.4%) in CCS than in DCS (34.0%) and EACS (17.3%). The results suggest that it would be reasonable to restore non‐N fixers in DCS and EACS and that N‐fixers are appropriate for CCS. Compared with grass, shrubs significantly enhanced the availability of nitrogen and phosphorus and soil electric conductivity, and significantly decreased the soil C/N ratio. The median fertility level of soil dominated by N‐fixers indicates that N‐fixers are suitable driver candidates from grassland to non‐N‐fixing shrub land. Four native shrubby legumes (Indigofera amblyantha, Sorphora viciifolia, Desmodium podocarpum and Bauhinia faberivar) and one soil‐conserving shrub (Ajania potaninii) are the top‐priority pioneers for ecological restoration.

Surface saline deposits and their substrates in a polluted arid valley (Murcia, Spain)

This study reports the mineralogical and geochemical variations of surface saline deposits and their substrates along an arid valley with an ephemeral river system (Spanish: rambla) affected by pollution from the now closed Cabezo de San Cristobal mine. This mine, which is close to Mazarron, Spain, once produced Pb, Zn, Ag and Fe ores. Saline efflorescences and crusts were found on piles of tailings and on the mudflats surrounding acidic ponds associated with the mine. These were composed of jarosite (10–60%), haematite (up to 20%) and gypsum (5–20%), and the kieserite (20–40%) and halotrichite (5–40%) mineral groups. In the rambla deposits downstream of the mine, the mineralogy of the saline efflorescences was similar to that recorded upstream: gypsum up to 20%, thenardite 5–20%, halite 20–40% and bloedite 20–40%. However, the substrate was very different, being mainly composed of jarosite (40–60%), haematite (5–20%) and goethite (5–20%); these minerals were never found upstream of the mining area, where carbonates predominated. Downstream of the mine, the rambla deposits contained large quantities of Fe (158,251 ppm), Pb (2,720 ppm), Zn (3,064 ppm), Sb (240 ppm) and As (1,092 ppm), along with Co (29 ppm), Ce (323 ppm), V (112 ppm), Th (23 ppm) and Nb (19 ppm) (all figures are maxima). Upstream, these contents were insignificant. Neither were large quantities found in the actual stream water (only Cu, V and Zn were detected, and then at concentrations of <0.05 ppm). Leaching and washing out from the tailings and other mine wastes substantially altered the substrates, but not the composition of the saline efflorescences along the arid valley.

Fleeting fame and groundwater: isolation and water in Kings River Valley, Nevada

This article examines how crop irrigation with groundwater briefly transformed the image of the Kings River Valley, a remote arid valley in northern Nevada, US, and captured state and national attention during a brief period in the mid-twentieth century. The valley’s short time in the limelight reveals the appeal of finding and recovering abundant water in arid places, bringing to light how groundwater use, technology, and regulation may be connected with alternating cycles of remoteness and popularity in a place. Coupled with improvements to infrastructure was the backdrop of a successful place; success, in this case, being associated with the know-how and capacity for massive withdrawals of groundwater and the ability to use this water to enhance agriculture. However, agriculture dependent upon groundwater in an arid place is complicated and uncertain, made more so when isolation is involved. As the technologies that supported large-scale groundwater pumping became more commonplace throughout the country and as groundwater became less readily accessible in the valley, attention to the Kings River dwindled and it slipped back into obscurity. Although groundwater has not completely disappeared, heavy groundwater pumping has altered the Kings River Valley, the place itself changing in the process. There are, however, some who gain advantage from isolation. The economic and political advantage of greater isolation accrued principally to absentee landowners, whose roots in Western cities were removed from daily life in the King River Valley. Isolation allowed less regulatory oversight of existing groundwater users, resulting in financial benefits which accrued primarily to those who supplied the cash and expertise for crops, cows, and groundwater, but did not actually reside in the valley. Absentee ranch owners generally had this capital, having the requisite connections and motivations to operate skillfully in the more structured and regulatory environment. Thus, this article analyzes water history coupling it with questions that are geographic in nature. What is it that makes a place isolated and how does groundwater figure into changes in isolation? How do cycles of isolation fit with changes in water technologies and regulation? And while the consequences of isolation may be apparent, what are the advantages of isolation to those using groundwater?

Pseudoridolfia, nouveau genre d'Apiaceae découvert au Maroc

A morphological study of a new species of Apiaceae and a molecular systematic analysis based on ITS sequences has led to the description of the new genus Pseudoridolfia that is related to Foeniculum, Ridolfia and Anethum. The new species, P. fennanei, occurs in the Tetraclinis articulata formations of the semi—arid valleys located on the northern fringe of the Central Plateau of Morocco.

Spatial pattern of rural settlements in the upper reaches of the Minjiang River

A quantitative analysis of the spatial pattern of rural settlements in the upper reaches of the Minjiang River was made with the major data sources being the relevant ETM image and the national geographical database of China (including contour line, river and road) at the scale of 1:250 000, and using image interpretation and field investigation to obtain spatial information on rural settlements. The results of the spatial analysis technique of GIS and correlation analysis showed that most settlements (78.2 %) were located in the mountain area at 1500 ∼ 2700 m altitude, and almost half in the arid valley area. More than 80.0 % of settlements had their slopes above 15°. Most settlements had good access to water resources, roads and communications, and tended to cluster close to the road network rather than the river. About half of the rural settlements in the study area were relatively concentrated, while the others were decentralized. Those with higher altitude usually had land with steep slope, inconvenient water and road accesses, and were located far apart from each other. In view of such a situation, further research should be done to make reasonable countermeasures on these settlements for better living conditions and ecosystem stability.

Determination of species-area relationships and minimum sampling area for the shrub communities in the arid valley in the upper reach of the Minjiang River, China

The minimum sampling areas (MSAs) for the shrub communities in the arid valley in the upper reach of the Minjiang River, China, were studied by fitting community species-area relationships using 3 types of equations. The MSAs were determined at the proportional factor (ρ) 0.6, 0.7, 0.8 and 0.9. The proportional factors represent the proportion of the number of species within a sampling plot in the total number of species. The MSAs of the shrub communities at different elevations and on different slope faces for ρ = 0.6, 0.7 and 0.8 were all around 100 m 2. Hence, the MSAs could be set to be 100 m 2 (10 m × 10 m) at 60%–80% precision levels. For ρ = 0.9, that is, for a 90% precision level, the MSAs were less than 200 m 2 (10 m × 20 m). The MSAs and species richness increased gradually with the rising elevation. At the elevation below 2000 m, the MSAs and species richness on the north-facing slope were larger than those on the south-facing slope. However, at the elevation around 2200 m, there was no difference amongst different facing slopes. For the shrub communities in the arid valley in the upper reach of the Minjiang River, the species-area curves by fitting the first two equations are better than that by fitting the third equation.

Drought-resistant physiological characteristics of four shrub species in arid valley of Minjiang River, China

The formation of 161 km-long arid valley (170 km 2) of Mingjiang River is attributed to the effect of foehn. The arid valley presents harsh conditions for the growth of vegetation, which include higher annual evaporation and transpiration rate (1400–2000 mm), lower annual precipitation rate (400–700 mm), steep slope, and infertile soils. Although the vegetation is dominated by xerophilous bushes and grasses, it plays a significant role in soil and water conservation in watershed and provides important references in the arid valley as it is very difficult to grow trees. Drought-resistant physiological characteristics of four native species, i.e., Sophora davidiana, Bauhinia faberi var. microphylla, Convolvulus tragacanthoides, and Artemisia gmelinii, have been measured. It was found that the content of chlorophyll, free proline and soluble sugars showed an increase, whereas evaporation ratio, WSD, RWC and cytolemma osmosis showed a decrease under drought stress. Integrated assessment of the four species indicated that the integrated drought resistance index was the highest in July (0.507), followed by September, August and June, whereas it was the lowest in May (0.442). The result provided a basis for vegetation restoration, especially it improved survival of planted species in May and June when plant species exhibit the weakest drought resistance.

Depth of edge influence of the agricultural‐forest landscape boundary, Southwestern China

AbstractThe landscape boundary is an important component of a landscape and often plays an indispensable role in regulating ecological flows. The primary objective of this study was to estimate how far the edge effects on agricultural‐forest landscape boundaries can penetrate into the forest and agricultural field. This will serve as a basis for understanding the interaction between forest and agricultural fields in the mountainous area of southwestern China and provide scientific basis for the practice of the policy of “returning agricultural field to forest.” Based on field investigations, three types of boundaries with six sampling transects were selected. We investigated the soil moisture, soil nutrients and vegetation diversity along the transect gradient and explored the depth of edge influence (DEI) with moving split‐window techniques for analyzing the data. DEI for soil moisture changed with the seasons, ranging from 6 m in the pepper field to 2 m in the forest during the dry season, and from 12 m in the pepper field to 2 m in the forest after heavy rain. DEI based on soil organic matter ranged from 1.5 to 10 m in the forest field, while it was not detected based on other soil nutrient factors. DEI based on vegetation diversity varied from 4 to 26 m and from 10 to 31 m in the forest and agricultural fields, respectively. These results provide the scientific basis for the policy “returning agricultural field to forest”. Based on these field observations, reducing human disturbance and revegetating with natural shrubs and meadows could be more effective for vegetation conservation in terms of soil moisture and soil nutrient content in the arid valley of the Minjiang River.

Plant community complexity in the arid valley of Minjiang River, southwestern China

Biocomplexity theory is becoming increasingly important in understanding natural vegetation dynamics and interrelation among all components of the ecosystem. In this study, based on the field investigation of plant species and environmental factors (altitude, microtopography, soil water content, and soil nutrients) in an arid valley of the upper reaches of Minjiang River, Sichuan Province, southwestern China, plant community complexity and its relationship with environmental factors, community diversity, species evenness and richness were studied. Both total and structural complexities of the communities showed a “high- low-high” tendency with the increase in altitude of the area, which meant that the complexity of communities was the highest at the sites of low and high altitude, whereas it was the lowest at the sites of intermediate altitude. It was found that the total community complexity had significant quadratic correlations with soil organic matter (SOM) content, total nitrogen (N), hydrolyzable N, soil water content, and available potassium (K), whereas it had no significant correlations with soil total K, total phosphorus (P), available P, and pH value. The total community complexity positively correlated with community diversity, species evenness and species richness, whereas the structural complexity negatively correlated with the community evenness. Of the two components of the total community complexity, namely, the structural complexity and the structural diversity, the structural complexity was more sensitive than the structural diversity to the changes of species in the community, which was not only related to the community evenness but also to the community richness. The relative contribution of both the structural complexity and the structural diversity to the total complexity would be different for different study areas or ecosystems.

Designing regional pattern for ecosystem restoration: A case study

Designing regional pattern is challenging for ecosystem restoration both in theory and in practice. The present study proposed a new approach to design regional pattern for ecosystem restoration with a case in the arid valley of Upper Minjiang River, SW China. The procedures are: (1) Determine the regional pattern of main environmental factors based on the relationships between the important environmental factors and the main geographical factors generated from DEM data. (2) Overlay the maps of the main environmental factors. (3) Generate a lookup table according to the species selection rule we proposed to link the candidate restoration species to the main environmental factors. (4) Determine the regional pattern of ecosystem restoration by positioning the restoration species in the map of environmental factors according to the lookup table. The regional restoration pattern designed in this way would be applicable not only to restoring a region, but also to predicting the future landscape change.

Differential responses of shrubs and herbs present at the Upper Minjiang River basin (Tibetan Plateau) to several soil variables

Vertical structure in plant communities is well recognized, but questions remain about the response of different stratal layers in a plant community to resource use. This study provides a quantitative approach to compare the relationships of nine edaphic factors and species distributions in shrub and herb layers, respectively, in an arid valley of the upper Minjiang River, Sichuan Province, China. Classification (TWINSPAN) determined three groups of shrubs and four groups of herbs. Ordination (both DCA and DCCA) found a correlation among species and edaphic variables. Borcard's method [Borcard, D., Legendre, P., Drapeau, P., 1992. Partialling out the spatial component of ecological variation. Ecology 73, 1045–1055.] was employed to partition the variation of species abundance data into independent components: pure spatial, pure environmental, spatial component of environmental influence, and undetermined. Based on those four components, a quantitative comparison of ecological variation between shrubs and herbs further eluidated their different response to the environment. Although soil moisture (SM) content, pH, soil organic matter (OC) and available potassium (AK) were the most important factors to both, the explained ecological variation of herbs was lower than that of shrubs. Understanding differences between stratal layers in resource use can shed light on plant–environment relationships.

Land cover changes based on plant successions: Deforestation, rehabilitation and degeneration of forest in the upper Dadu River watershed

To link regional land use/cover changes with environmental effects, land cover changes are required to reflect vegetation successions, whereas the land cover classification systems commonly used nowadays cannot serve this purpose. In this paper, a new land cover classification system is established in which land covers are classified by the vegetation succes-sions, taking Zamtang County, Barkam County and Jinchuan County in the upper Dadu River watershed as a study area. Using multi-temporal remote sensing images, the land cover data of 1967, 1986 and 2000 are obtained by means of integration of unsupervised classification and visual interpretation methods. The database facilitates the study of land use/cover changes, en-vironmental effects and ecological construction. Land cover changes reflect the main ecological processes in the upper Dadu River watershed. The landscape composed mainly of grasslands, wildwoods and alpine scrubs in 1967 was changed to that of grasslands, secondary forests, al-pine scrubs, fragmentary wildwoods, artificial forests, secondary scrubs in 2000, meanwhile, the landscape got more fragmentized. The total area of the forests decreased by 9.43%. Study results have shown the process of restoration of logged areas in forest centers. From 1967 to 2000, only 6.86 percents of logged areas were converted to shrubs, meadows or crop-lands, and the rest were converted into artificial forests or secondary forests. So the ecological shelter functions will be restored, stage by stage. Firewood collection, charcoal production and overgrazing are the three major triggers for the extensive degradation of alpine oak forests, Sa-bina tibetica forests and meadows. The arid valley grasslands expanded too. The degradation of vegetation in the southern slopes impairs ecological shelter functions and affects livelihood of local residents, so it is essential to find effective measures for ecological restoration and recon-struction. Field investigations have found that the current measures have not concerned with how to keep the livelihood of local farmers and herders. The most important measure for ecological protection and restoration is to help the farmers and herders to raise the living standard, which means that they will never need to rely only on the colonizing of croplands, the logging of forests and the grazing of livestock to make a living.

The energy balance, evapo-transpiration and nocturnal dew deposition of an arid valley in the Andes

The arid Elqui valley, part of the Norte Chico of Chile between 27°S and 33°S latitude, is located south of the hyper-arid Atacama desert. The region is characterized by complex terrain and great different of the surface properties, the latter due to cultivated and irrigated areas along the valley floor and sparse vegetation in the arid surrounding. Here the energy balance of the valley has been investigated to compare the evapo-transpiration of the cultivated area with the one of the natural vegetation and to estimate the dew deposition, which proves to be an important water resource in arid areas. Analyzes are based on two Bowen ratio and two eddy covariance stations, operated in the Elqui valley from 2000 to 2002 and in November 2004, respectively. The Bowen ratio of the natural vegetation is about β ≈ 11 , but much lower in the cultivated and temporally irrigated area along the valley floor. A typical value of the Bowen ratio of a field covered by potatoes is β ≈ 2.5 after harvesting or during dry periods and is β ≈ 0.7 to 1 after irrigation events or precipitation. For an area with natural vegetation, the annual accumulated evapo-transpiration reaches 65 mm yr −1, which is 65% of the mean annual precipitation and 3.5% of the equivalent net radiation R n / L . For the cultivated fields along the valley floor, the annual accumulated evapo-transpiration reaches 750 mm yr −1, which is 40% of the equivalent net radiation, R n / L , and about 100% of the sum of estimated irrigation and mean annual precipitation ( I+ P). The annual nocturnal dew deposition is about 5–10 mm yr −1 and, thus, serves as an additional water source for natural vegetation, especially during dry years.

Comparison of two approaches for detecting the depth of edge influence on vegetation diversity in the arid valley of southwestern China

Three types of landscape boundary (forest/pepper field, forest/cabbage field, and forest/grassland) were selected in the arid valley of upper reaches of Minjiang River, southwestern China. On the basis of vegetation diversity, the depth of edge influence (DEI) on different types of landscape boundaries was estimated using principal components analysis (PCA) method and moving split-window techniques (MSWT). The results showed that in the 5 transects, PCA method was able to detect the edge influence depth with 3 transects, while MSWT could explain 4 transects. It is concluded that PCA and MSWT both can be used to detect the depth of edge influence within 50 m from the edge to the interior. Similar conclusions were drawn in the forest of each transect with the two methods, but no similar conclusions were drawn in the pepper field of each transect. Although the two methods have advantages and disadvantages respectively, they are useful tools for characterizing edge dynamics. Comparing the two methods, MSWT is more successful.

Multiple‐scale soil moisture distribution and its implications for ecosystem restoration in an arid river valley, China

AbstractThe spatial distribution of soil moisture and its multiple‐scale correlations to other environmental factors were examined along the Upper Minjiang River valley, China, a landscape subject to severe land degradation of soil and water erosion but also under investigation for potential ecosystem restoration. Results showed that: (1) Soil moisture was highest in the headwaters, and lowest in the arid valley, while moderate values characterized outside the arid valley. The polynomial model of soil moisture distribution on slopes was concave in the lightly disturbed headwaters, convex in the highly damaged arid valley, while convex on south facing slopes and concave on north facing slopes in highly damaged areas in better environmental condition. (2) Soil moisture was correlated with environmental factors at different scales, where elevation and air humidity were only correlated at the sample plot scale, light intensity and wind speed were found to be significant at both slope and site scales and slope and sample plot scales; while slope angle was correlated at all the three scales. From this we conclude that it is possible to improve soil moisture conditions in the arid valley by lowering slope angle and adding low‐cost irrigation systems. (3) The practical threshold of soil moisture for growing meadows, shrubs, and forests were 11ċ800 per cent, 3ċ925 per cent, and 16ċ078 per cent respectively; the arid valley displayed soil‐moisture conditions unfavourable to forest growth. The planned reforestation project is not ecologically reasonable. Reducing human disturbance and revegetating with natural shrubs and meadows may produce more effective results. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Shrew opossums (Paucituberculata: Caenolestes) from the Huancabamba region of east Andean Peru.

Shrew opossums of the genus Caenolestes are restricted to the northern Andes and include four species: C. fuliginosus, C. convelatus, C. caniventer and C. condorensis (Albuja and Patterson 1996). Caenolestes fuliginosus is a highland species of the paramos of central Ecuador, Colombia and western Venezuela, but the remaining three species occur in sub-tropical montane forests at lower elevations (Albuja and Patterson 1996). Caenolestes convelatus and C. caniventer are known from the western slopes of the Andes, the former from Colombia and northern Ecuador and the latter from southern Ecuador and northern Peru (Bublitz 1987), while the recently described Caenolestes condorensis is currently known only from the isolated Cordillera del Condor along the eastern slopes of the Andes in southern Ecuador (Albuja and Patterson 1996). The first records of Caenolestes from Peru were collected in the Departamento de Piura (Barkley and Whitaker 1984) and were originally reported as C. fuliginosus but later were later identified as C. caniventer (Albuja and Patterson 1996). The Departamento de Piura lies just north of the Huancabamba Depression, a region defined by the arid valley of the Rio Chamaya and adjacent low elevation passes (Fig. 1). Many species of Andean bird reach their southernmost distributional limit at the Huancabamba Depression (Parker et al. 1985), and it has been postulated that the region might also serve as a barrier to the southward dispersal of Caenolestes (Vivar et al. 1997). However, these same authors also cautioned that the Huancabamba region remains poorly surveyed for mammals and that what may appear to be a pattern may in fact be the result of inadequate sampling. In this paper we present additional data on the distribution of Caenolestes from localities in Peru north and south of the Huancabamba Depression.

δ13C and δD Values of Opuntia Atacamensis Depending on Different Environmental Conditions in the Atacama Desert of Northern Chile

We analysed 13carbon and deuterium discrimination in Opuntia atacamensis Phil, at three different sites in the Atacama desert in Northern Chile: At the western Andean slopes, influenced by summer rainfall, in the very arid Chilean central valley, and at coastal fog mountains. At the most arid site, the central valley, discrimination of 13C and D was less (δ-values less negative) and also discrimination more against deuterium. This is an aridity, not an altitude effect. The differences in 13C content may be due to some carbon fixation via the C3 photosynthetic pathway at the more humid sites. Deuterium enrichment at the arid sites might be due to greater discrimination of HDO against H2O during transpirational water loss.