Arid Communities Research Articles

The role of xerophytic vegetation on fog harvest

Fog is an important resource for plant growth in arid communities. However, it is unclear whether small shrubs have an ability to capture fog water. We aimed to test this role and expected that were modulated by plant geometry (e.g., height, volume), as neighbor tree species do. Moreover, if xerophytes are adapted to this water resource, they should follow the temporal fluctuations in atmospheric fog offer, to exhibit a high efficiency in fog harvest, and capturing more fog than rain. Two sites in north-central Chile were worked, where 11–12 species per site were studied. Three funnels connected to bottles were placed beneath each plant, and evaluated monthly to quantify fog dripping. Fog offer was measured with standard fog collectors (SFCs). Several species collected more water than the controls in open spaces, reaching up to 182 mm/yr. A significant correlation of water harvest with plant height and volume was found. Only in the xeric site, water capture correlated significantly with SFC data. The capture efficiency was also the highest in this site. Fog harvest by plants was several times the rainwater input (31–34 mm), highlighting the role of xerophytes in the capture of the more abundant resource supplied by fog.

Arid community responses to nitrogen and carbon addition depend on dominant species traits and are decoupled between above‐ and below‐ground biomass

AbstractQuestionsArid communities are strongly limited by soil resources including water and nitrogen (N). Plants compete for N with other plants and microorganisms, which are also limited by carbon (C). We propose that above‐ and below‐ground plant responses to soil resources are modulated by community structure (species relative abundances, “mass ratio hypothesis”) and species traits (relative growth rates — RGRs). We evaluated the single and combined effects of soil N and C addition on the above‐ and below‐ground biomass accumulation of perennial grass patches in an arid community, and the mechanisms involved in their responses.LocationPatagonian steppe, Argentina.MethodsWe added N (2 g N m−2; NH4NO3) and C (330 g C m−2; sucrose) to 1‐m2 field plots in a factorial design. After two years, we harvested above‐ground (n = 5 plots) and below‐ground biomass (n = 10 soil cores) and sorted it by species. We measured potential soil respiration as a proxy of microbial activity.ResultsTotal above‐ground biomass increased by 55% as a result of N and decreased by 45% as a result of C addition, in relation to controls. C addition reduced total below‐ground biomass by 42%. The above‐ground differences were associated with changes in the biomass of dominant species according to their RGRs. Poa ligularis (dominant, high RGR) increased by 92% as a result of N addition while Pappostipa speciosa (dominant, low RGR) decreased by 55% as a result of C addition. Intermediate and subordinate grasses did not modify their biomass, independently of their RGR. Potential soil respiration was three times higher in plots with C addition than in control plots.ConclusionsCommunity biomass was explained by a combination of mass ratio hypothesis and specific RGR, as dominant grasses controlled above‐ground community responses to N (high‐RGR species) and C addition (low‐RGR species). Our findings highlight the independence between the above‐ and below‐ground processes and the importance of considering community equitability and species characteristics to predict plant community responses to changes in soil resources.

Promoting Larval Source Management in Urban and Arid Communities as a Vital Supplementary Intervention, Zambia

Promoting Larval Source Management in Urban and Arid Communities as a Vital Supplementary Intervention, Zambia

Effect of Climate Change on Acquisition of Quality Education: A Case Study of Maasai Pastoralists in Narok County, Kenya

Climate change is a global phenomenon with far reaching impacts. Arid and semi-arid communities in Kenya, among them the Maasai community from Narok County, are dependent on the natural resources for their livelihood thus are greatly hit by the adverse impacts of climate change. This paper sought to establish the indirect effects of climate change on the quality of education among the Maasai community. Desktop literature review approach and key informant phone interviews were adopted for data collection. The review of literature indicated that increased poverty levels arising from climate change has largely affected the affordability of quality education. Therefore, people in Maasai community resort to coping mechanisms on labour demands that accelerate school dropout as well as early marriages. The Maasai herders are forced to increase their migration trends to long distances, a practice that has increased child labour disrupting learning for most school going children. In addition, the girl child has become more vulnerable to sexual abuse and early marriages with a consequent denial of education opportunities. The effect of the climate change on wildlife habitat has led to human- wildlife conflict that poses a threat to the security of the community members and therefore interferes with the smooth running of schools. Consequently, interventions to mitigate climate change effects should not only concentrate on the direct but also the indirect impacts that have got multiplier effects on sectors like education. These interventions should include, provision of adequate water infrastructure, investment in education policy and boarding school Infrastructural development.

Re-Examining Access and Participation: Contribution of Cultural and Socio-Economic Variables in Inhibiting Rural Arid Communities of Kenya to Meet the EFA 2015 Target?

Re-Examining Access and Participation: Contribution of Cultural and Socio-Economic Variables in Inhibiting Rural Arid Communities of Kenya to Meet the EFA 2015 Target?

Травяная растительность побережья Японского моря (Лазовский государственный природный заповедник им. Л. Г. Капланова. Приморский край)

Травяная растительность побережья Японского моря (Лазовский государственный природный заповедник им. Л. Г. Капланова. Приморский край)

Mind the gap among patches in arid plant communities: rapid root proliferation in response to N addition

In arid communities, it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbouring bare ground areas. This becomes relevant in systems where the vegetation is distributed in patches surrounded by bare soil. However, whether roots of different species may be overlapping under bare ground areas is still controversial. The factors controlling root responses when no plants appear to be directly influencing the gap among patches are still unclear. The aim of our study was to detect perennial grasses responses to an N enrichment pulse. In a semi-arid steppe (Patagonia, Argentina), we buried root traps filled with sieved soil with and without N addition, under bare soil patches. Traps were harvested after 4 and 6 months. Trap neighbourhoods (30 cm in diameter) included at least three of the dominant tussock species. After harvests, we identified species in the traps by root traits and quantified diversity, biomass and specific relative growth rates. Bare ground areas show simultaneous root growth of different species. Diversity of perennial grass roots was higher with N addition than without it in the first harvest (4 months), but this difference disappeared in the second harvest (6 months). Root biomass was maximal after 6 months in N addition traps. Species preferred by herbivores (Bromus pictus and Poa ligularis) showed rapid growth and responses to N addition. Differences between harvests may be an indicative that N pulses interact with rising temperatures and soil water content as growing season progress.

Man's artificial glacier—a way forward toward water harvesting for pre and post sowing irrigation to facilitate early sowing of wheat in cold arid Himalayan deserts of Ladakh

AbstractUnavailability of irrigation water for early sowing has remained a constant problem in cold arid deserts of Ladakh. In order to get a solution to this problem, a 2-yr farmers’ participatory research trial with best bet agronomic management on artificial glacier water harvesting technology was conducted. The technology involves collecting water from natural glaciers that melt during late December. The water is diverted toward a shed constructed with stone embankments set up at regular intervals. The area is chosen where there is minimum interference of solar radiation, generally between two mountain slopes or ridge that is on the leeward side. The melted water is that melts from the natural glacier impeded by the embankments and get frozen here. This frozen water starts melting in late March and is used for both pre sowing and initial crop water requirement. It also ensures early sowing of wheat by creating additional 45-day window which leads to introduction of long- and medium-duration wheat varieties to replace decades old locally grown short-duration varieties. The work was initiated with a benchmark survey of 100 farmers to get an understanding of present irrigation scenario, crop management practices and date of sowing. Data from 99 farmer participating trial of wheat conducted after or from bench mark survey clearly indicated that the effect of water shortage can be seen on yield and yield attributing characters due to unavailability of pre sowing irrigation and water requirement at imperative growth stages and may also lead to terminal heat stress in wheat crop. Out of total number of irrigations applied, initial two irrigations can be compensated by artificial glacier water harvesting technique, leading to a revolution in the agriculture scenario of the tribal population by introduction of long- and medium-duration wheat varieties in cold arid desert of Ladakh for the very first time. It was observed that wheat seeding done in first fortnight of April gave better yields in comparison to late seeded wheat. Moreover, the long-duration varieties (LDVs) or medium-duration varieties (MDVs) sown under late condition gave better yield in comparison to locally grown short-duration varieties sown at same time. Yield potential of LDVs and MDVs of wheat under late sowing was found quite low in comparison to early-sown wheat, still when compared with the performance of locally grown wheat the yields were more even if the local varieties were sown early. The outcome of this study will help the farmers of tribal, cold arid community in harvesting better wheat yields by timely sowing of the wheat crop accompanied with better bet agronomic management practices. Government initiative is further required to ensure better outreach of complete crop management strategies to the tribal farming community of the region in order to ensure food security and improve their socioeconomic status.

Alternative pathways to landscape transformation: invasive grasses, burn severity and fire frequency in arid ecosystems

Summary Arid ecosystems are often vulnerable to transformation to invasive‐dominated states following fire, but data on persistence of these states are sparse. The grass/fire cycle is a feedback process between invasive annual grasses and fire frequency that often leads to the formation of alternative vegetation states dominated by the invasive grasses. However, other components of fire regimes, such as burn severity, also have the potential to produce long‐term vegetation transformations. Our goal was to evaluate the influence of both fire frequency and burn severity on the transformation of woody‐dominated communities to communities dominated by invasive grasses in major elevation zones of the Mojave Desert of western North America. We used a chronosequence design to collect data on herbaceous and woody cover at 229 unburned reference plots and 578 plots that burned between 1972 and 2010. We stratified the plots by elevation zone (low, mid, high), fire frequency (1–3 times) and years post‐fire (YPF; 1–5, 6–10, 11–20 and 21–40 YPF). Burn severity for each plot was estimated by the difference normalized burn ratio. We identified two broad post‐fire successional pathways. One was an outcome of fire frequency, resulting in a strong potential transformation via the grass/fire cycle. The second pathway was driven by burn severity, the critical aspect being that long‐term transformation of a community could occur from just one fire in areas that burned at high or sometimes moderate severity. Dominance by invasive grasses was most likely to occur in low‐and high‐elevation communities; cover of native herbaceous species was often greater than that of invasive grasses in the mid‐elevation zone. Synthesis. Invasive grasses can dominate a site that burned only one time in many decades at high severity, or a site that burned at low severity but multiple times in the same time period. However, high burn severity may predispose areas to more frequent fire because they have relatively high cover of invasive annual grass, suggesting burn severity and fire frequency have both independent and synergistic effects. Resilience in vegetation structure following fire in many arid communities may be limited to a narrow window of low burn severity in areas that have not burned in many decades.

Root proliferation strategies and exploration of soil patchiness in arid communities

AbstractSoil patchiness is a key feature of arid rangelands. As root proliferation contributes to soil exploration and resource uptake, it is ecologically relevant to understand how species respond to soil heterogeneity and coexist. Campbell et al.'s influential 1991 hypothesis proposes that dominant species deploy root systems (scale) that maximize soil volume explored. Instead, subordinate species show accurate root systems that exclusively proliferate in nutrient‐rich patches (precision). After many experiments under controlled conditions, the generality of this hypothesis has been questioned but a field perspective is necessary to increase realism in the conceptual framework. We worked with a guild of perennial graminoid species inside a grazing exclosure in an arid Patagonian steppe, a model system for ecological studies in arid rangelands for four decades. We buried root traps in bare ground patches with sieved soil, with or without a pulse of nitrogen addition, to measure specific root biomass and precision at 6 and 18 months after burial. We also estimated scale (root density) in naturally established plants, and root decomposition in litter bags. Several species grew in root traps. Dominant species showed the highest root biomass (in both harvests) and scale. Subordinate species grew more frequently with nitrogen addition and showed lower biomass and scale. Similar total root biomass was found with and without nitrogen addition. Species differed in root decomposition, but correcting species biomass by decomposition did not change our conclusions. We did not find a relation between scale and precision, indicating that Campbell's hypothesis is probably not supported in this Patagonian steppe. Soil resource acquisition differences probably do not utterly explain the coexistence of dominant and subordinate species because the steppe is also affected by large herbivore grazing. We propose that root proliferation in this steppe is the result of the interaction between individual density in the community and specific root growth rates.

Precipitation quantity and timing affect native plant production and growth of a key herbivore, the desert tortoise, in the Mojave Desert

BackgroundDeserts may be disproportionately vulnerable to changes in precipitation that accompany global climate change due to complex evolutionary relationships of species to historical conditions. Based on current and projected climate scenarios for the southwestern United States, we manipulated rainfall timing and quantity and measured the response by plants and the growth and behavior of the desert tortoise (Gopherus agassizii) to precipitation in the eastern Mojave Desert.ResultsWe found that winter-dominant rain – the current prevailing pattern in the eastern Mojave Desert – and greater total rainfall correlated with greater cover and species richness of plants. Winter-dominant rain also correlated with a higher proportion of native plants flowering relative to invasive plants. Juvenile tortoises grew more rapidly when they were subjected to rainfall treatments that associated with increased plant abundance and species richness, while their behavior appeared more driven by water availability.ConclusionsOur results suggest that precipitation timing may be as important as rainfall quantity when considering total effects of climate change on arid-adapted systems. Further research should explore how the timing of rainfall may interact with aridity or temperature to influence total effects due to climate change on arid communities.

Traditional veterinary solutions for herders living in limited and changing conditions: A case study of “crianceros” of Central Northern Patagonia, Argentina

In the arid Patagonia, sheep and goat breeding provides the main source of income for many traditional families of Mapuche-Tehuelche ancestry (locally named as “crianceros”). Using an ethnobotanical quali-quantitative approach, traditional veterinarian knowledge (TVK) was studied in 20 rural establishments on the Central Chubut plateau (Argentina). During the study 17 diseases were registered, which are treated with 28 remedies involving 14 native plants and other resources of mineral origin. Healing practices include symbolic and religious elements, inherited as part of the biocultural memory of the region's original inhabitants and from European Hippocratic medicine. Environmental processes play a substantial role as aetiological agents, given that the environment is considered by inhabitants in an integral way, composed of both natural and supernatural elements. Plant species are versatile in their healing uses, and treatment is performed by both women and men in a similar manner. This TVK forms part of the unique criancero identity which is characterized by a constant, multidimensional dialogue with the different elements of nature. This article promotes reflection on the complex processes involved in construction of the dynamic, specialized medical-veterinary system in arid communities, and the importance of local veterinary solutions for herders living in limited and changing conditions.

A Multidimensional Functional Trait Approach Reveals the Imprint of Environmental Stress in Mediterranean Woody Communities

Water availability is one of the most important factors determining species distribution, plant community structure and ecosystem functioning. We explore how the functional structure of Mediterranean woody plant communities varies along a regional gradient of aridity in the Andalusian region (south Spain). We question whether communities located in more arid sites show more similarity in their functional structure when compared with communities located in wetter sites or whether, instead, there is divergence in their functional spaces. We selected five aridity zones (three sampling sites per zone) and measured 13 traits of different functional dimensions (including leaf, stem and root traits) in 74 woody plant species. We quantified functional space differences using the n-dimensional niche space approach (hypervolume). We found a larger functional space for the wetter communities compared with the more arid communities, which showed greater overlap of the trait space occupation. Our results indicate that aridity acts as a key abiotic filter affecting various metrics of the community trait structure, in accordance with the plant economics spectrum. We have also documented consistent variation in the functional space, supporting lower functional diversity under more harsh climatic conditions. The trend of functional space variation along the aridity gradient was different when considering traits from only one plant organ. Thus, the filtering process driving the functional structure of the communities studied here largely depends on the trait axis considered; for example, the root dimension showed considerable variation in wet environments, whereas the leaf dimension exhibited a larger functional space in the drier habitats.

Water production for irrigation and drinking needs in remote arid communities using closed-system greenhouse: A review

Water needs for agriculture, food production and drinking are considered one of the most critical challenges facing the world in the present days. This is due mainly to the scarcity and lack of fresh water resources, and the increasing ground water salinity. Most of these countries have a high solar energy potential. This potential can be best developed by solar desalination concepts and methods specifically suited for rural water supply, irrigation. In this paper, a humidification–dehumidification (HD) water desalination system with several technologies for irrigation and drinking needs in remote arid areas is introduced from technical and economic point of views. This study has investigated (1) detailed discussion of technical developments, economical and sustainable aspects; (2) benefits of the new design over traditional applications, desalination and other irrigation methods; (3) specific requirements and implementation challenges in remote and cold regions; (4) performance and reliability improvement possible techniques. Recommended researches and projects leading to high efficiency, economical and sustainable applications of some desalination devices driven by solar energy are highlighted.

Extrafloral nectar fuels ant life in deserts.

Interactions mediated by extrafloral nectary (EFN)-bearing plants that reward ants with a sweet liquid secretion are well documented in temperate and tropical habitats. However, their distribution and abundance in deserts are poorly known. In this study, we test the predictions that biotic interactions between EFN plants and ants are abundant and common also in arid communities and that EFNs are only functional when new vegetative and reproductive structures are developing. In a seasonal desert of northwestern Argentina, we surveyed the richness and phenology of EFN plants and their associated ants and examined the patterns in ant-plant interaction networks. We found that 25 ant species and 11 EFN-bearing plant species were linked together through 96 pairs of associations. Plants bearing EFNs were abundant, representing ca. 19 % of the species encountered in transects and 24 % of the plant cover. Most ant species sampled (ca. 77 %) fed on EF nectar. Interactions showed a marked seasonal pattern: EFN secretion was directly related to plant phenology and correlated with the time of highest ant ground activity. Our results reveal that EFN-mediated interactions are ecologically relevant components of deserts, and that EFN-bearing plants are crucial for the survival of desert ant communities.

Design flow factors for sewerage systems in small arid communities

Reliable estimation of sewage flow rates is essential for the proper design of sewers, pumping stations, and treatment plants. The design of the various components of the sewerage system should be based on the most critical flow rates with a focus on extremely low and peak flow rates that would be sustained for a duration related to the acceptable limits of behavior of the components under consideration. The extreme flow conditions and to what extent they differ from the average values are closely related to the size of the community or network, and the socioeconomic conditions. A single pumping station is usually sufficient to pump flow from small community in either flat or non-undulating topography. Therefore, the hydraulic loading on the wastewater treatment plant (WWTP) results from the pumped flow from the pumping station rather than the trunk sewer flow. The intermittent operation of the pumping units further accentuates the sewage hydrograph in the final trunk sewer. Accordingly, the design flow for the various components of the WWTP should be determined based on their relevant flow factors. In this study, analysis of one representative small community out of five monitored small communities in Egypt and the Kingdom of Saudi Arabia is presented. Pumped sewage flow rates were measured and the sewer incoming flows were hydraulically derived. The hourly and daily sewer and pumped flow records were analyzed to derive the relationship between the flow factors that would be sustained for various durations (instantaneously, 1h, 2h, etc.) and their probability of non-exceedance. The resulting peaking factors with a consideration for their sustained flow duration and specified probability would permit the design of the various components of the treatment plant using more accurate critical flows.

Invasion by an exotic, perennial grass alters responses of a native woody species in an arid system

Grass growth has been encouraged in arid communities globally to improve grazing. Often exotic species are planted, subsequently spreading beyond their plantings to drastically alter cover and negatively impact native species. We evaluated the effects of the invasive, perennial grass Cenchrus ciliaris on the native woody species Cercidium microphyllum over two growing seasons: 2002 and 2003. To determine if C. ciliaris alters seasonal responses of C. microphyllum, we measured predawn water potential, photosynthesis, and branch sacrifice on C. microphyllum growing with either native cover or C. ciliaris. In 2003 a removal treatment of C. ciliaris was applied to assess responses in C. microphyllum during the summer. In both years, C. microphyllum water potentials closely tracked seasonal rainfall, suggesting dependence on shallow soil water. In 2002, we observed few negative impacts when C. microphyllum grew with C. ciliaris. However, the trees growing with C. ciliaris exhibited greater branch sacrifice, a typical response to drought, which likely complicated interpretation of the treatment effects. Removal of C. ciliaris resulted in increased water potentials and photosynthesis. This study suggests that exotic grasses, such as C. ciliaris, can reduce both water potential and photosynthetic rates in mature woody shrubs, like C. microphyllum, in aridland systems.

Influence of precipitation pulses on long-term Prosopis ferox dynamics in the Argentinean intermontane subtropics

Biological processes in arid communities are associated with episodic precipitation pulses. We postulate that annual to decadal-scale precipitation pulses modulate the dynamics of the intermontane Prepuna woodlands. To study this hypothesis, we have assessed the influence of precipitation pulses on the rates of growth and survival of Prosopis ferox in the Prepuna woodlands during the past century. Tree ages from several P. ferox stands were used to reconstruct the establishment patterns at each sampling site. Ring-width chronologies provided the basis to assess the influence of annual versus multiannual precipitation pulses on radial growth and establishment over time. Both the radial growth and the stand dynamics of P. ferox at the regional scale were found to be largely modulated by climate, with precipitation the dominant factor influencing interannual variations in P. ferox ring-widths. Our analysis of dendrochronological dating data on 885 individuals of P. ferox revealed a period of abundant establishment from the mid-1970s to beginning of 1990 s, which is coincident with an interval of remarkable above-average precipitation. However, tree-growth and establishment patterns at the local scale in the Prepuna also reflected land-use changes, particularly long-term variations in livestock intensity. The P. ferox dynamics documented here substantiates the hierarchical concept of "resource-pulse" in dry ecosystems, with precipitation pulses of different lengths modulating distinct dynamic processes in the P. ferox woodlands. Interannual variations in precipitation influence year-to-year patterns of P. ferox radial growth, whereas multiannual oscillations in rainfall influence episodic events of tree establishment. The long-term interval considered in this study enabled us to disentangle the roles of natural versus human controls on P. ferox dynamics in the region.

Testing the role of biotic stress in the stress gradient hypothesis. Processes and patterns in arid rangelands

Since many arid ecosystems are overstocked with domestic herbivores, biotic stress could have a stronger influence in modulating the balance of species interactions than expected from the stress gradient hypothesis (SGH). Here we tested a priori predictions about the effect of grazing on species interactions and fine scale spatial structure of grasses in water‐limited ecosystems. We used detailed vegetation mapping and spatial analysis, and performed a field experiment where the direct and indirect components of positive interactions were disentangled to provide evidence of links between process and pattern. We found associational resistance (biotic refuge) to be the dominant process in grazing situations, while competition, instead of direct facilitation, seemed to govern grass spatial patterns when herbivore pressure was relaxed. These results suggest that facilitation between grasses in arid communities may be related to herbivory rather than nurse plant effects. Associational resistance tends to have the strongest effect on spatial aggregation of species at intermediate grazing pressure. Results suggest that contrary to SGH, this physical clustering of species decreased when grazing pressure reached their maximum levels. Positive associations remained significant only when palatability differences between neighbours is large, suggesting that managing stocking rate is a key factor determining the persistence of herbivory refuges. These refuges are potential foci to initiate population recovery of high quality forage species in arid degraded areas.

Structure and spatial self-organization of semi-arid communities through plant–plant co-occurrence networks

In a variety of areas in ecology, a network approach has proven fruitful in studying the interactions among the components of systems. We propose a novel network approach for examining plant species interactions in plant communities. We constructed various networks based on the plant species found on 12 point-intercept transects in a semi arid community, developing one network for each transect. Species were identified as nodes and were considered linked if they occurred at the same intercept point. To understand the general organization of the networks, we calculated the cumulative distribution of the number of links per species in each network, the average nearest neighbour degree of each species, and the self-organization of the most-linked species. The networks behaved as mutualistic ecological systems and displayed a typical truncated power-law distribution for the cumulative distribution of the number of links per species. The results suggest that most of the species were preferentially associated with a few others. In all but one highly competitive species ( Stipa tenacissima), the number of links and abundance were positively correlated. Link density was positively correlated with the spatial self-organization of the entomophyllous and facilitated species, while generalist species did not present any relation. For S. tenacissima, the link density and spatial self-organization were positively correlated, as other species were able to establish in the edge of S. tenacissima patches when it was less dominant. Our results agree with past works in networks, and it seems that in a semi-arid environment, at least, our network approach would provide additional information about the nature of interactions that each species develops in the community.