Low Rainfall Areas Research Articles

Postharvest Tillage Reduces Downy Brome (Bromus tectorumL.) Infestations in Winter Wheat

In the Pacific Northwest, downy brome continues to infest winter wheat, especially in low-rainfall areas where the winter wheat–summer fallow rotation is the dominant production system. In Washington, a study was conducted for 2 yr at two locations in the winter wheat–summer fallow region to determine the influence of four postharvest tillage treatments on vertical seed movement, seedbank depletion, and plant densities of downy brome. The four tillage implements included a disk, sweep plow, harrow, and skew treader. The study also included a no-till treatment for comparison. The sweep plow and disk led to the most vertical movement of downy brome seed compared with the no-till treatment. Approximately 75% of the fall postharvest seed in the no-till treatment was located either on the soil surface or in the 0- to 3-cm depth at both locations. In contrast, 75% of the seed in the disked treatment was located from 0 to 6 cm deep at both locations. The disk and sweep plow both decreased downy brome seed in the soil at the 0- to 3-cm depth compared with the harrow and no-till treatments. There was no difference in downy brome plant densities following postharvest tillage in the summer fallow due to any of the treatments. However, plant densities in the subsequent winter wheat crop were reduced by the disk and sweep plow compared with the no-till and skew-treader treatments. In general, seed densities as affected by the skew treader fell between the disk and the no-till treatments. The use of the sweep plow and the disk should be integrated into a weed management strategy for downy brome in the wheat–fallow region of the Pacific Northwest.

Avian responses to the diversity and configuration of fire age classes and vegetation types across a rainfall gradient

In many regions, planned burns are implemented to reduce fuel loads and mitigate wildfire risk; increasingly, they are also used to achieve conservation outcomes. However, there is uncertainty regarding how best to apply fire to landscapes in order to enhance biodiversity. The assumption that variable fire regimes are conducive to biodiversity conservation is appealing given its basis in landscape ecological theory, which predicts that spatially complex landscapes sustain greater biodiversity. This supposition is often used as a basis for fire management but has rarely been tested in the context of fire. We sought to test predicted positive relationships between bird diversity and both landscape diversity and configuration in the fire-prone Otway Ranges, southeast Australia, where vegetation transitions from treeless heath to tall open eucalypt forest across a rainfall gradient. We used a whole-of-landscape sampling approach, and mapped fire age classes and vegetation types separately within thirty-six 300ha landscape sampling units. Bird surveys were undertaken at sub-sampling locations during two successive years, and presence-absence data were used to generate landscape-level estimates of species richness and turnover. Generalized linear mixed models, model selection and model averaging were used to investigate how birds responded to landscape diversity and configuration across the rainfall gradient. Species richness was positively associated with age class diversity, age class configuration and vegetation type diversity. Species turnover was positively associated with age class diversity in areas of lower rainfall but exhibited a negative response in areas of higher rainfall. Neither response variable was associated with vegetation type configuration. This study is one of few landscape scale analyses to provide empirical support for the widely held assumption that spatially variable fire regimes can increase the diversity of faunal assemblages. Further, our results demonstrated consistency in responses of species richness to fire-mediated landscape complexity across a rainfall gradient. Managers can potentially increase bird species richness by increasing both the diversity of fire age classes, and the complexity of age class configuration, within relatively small (300ha) areas.

Deficiencies in the Briske et al. Rebuttal of the Savory Method

Clinging to past viewpoints and techniques based on a lim- ited and small subset of knowledge on the subject of range- land grazing management is not helpful. The knowledge base used by Briske et al. 1 stems from a very poor understanding of Holistic Planned Grazing and poorly executed grazing ex- periments (see the work of Teague et al. ). 2 To make sweeping statements such as “The Savory method cannot green deserts or reverse climate change” is particularly misleading. It ig- nores the fact that many ranchers operating in low rainfall areas from 10 to 15 inches, areas so bare of vegetation that most people would call them deserti ed, have managed to restore vegetation, ecosystem function, and productivity us- ing Holistic Planned Grazing when even complete removal of livestock had failed to achieve any restoration. Only if the comment refers to true deserts receiving almost no rainfall would the statement possibly be true. DOI: 10.2458/azu_rangelands_v35i6_teague

Geo-environmental model for the prediction of potential transmission risk of Dirofilaria in an area with dry climate and extensive irrigated crops. The case of Spain

Zoonotic filarioses caused by Dirofilaria immitis and Dirofilaria repens are transmitted by culicid mosquitoes. Therefore Dirofilaria transmission depends on climatic factors like temperature and humidity. In spite of the dry climate of most of the Spanish territory, there are extensive irrigated crops areas providing moist habitats favourable for mosquito breeding. A GIS model to predict the risk of Dirofilaria transmission in Spain, based on temperatures and rainfall data as well as in the distribution of irrigated crops areas, is constructed. The model predicts that potential risk of Dirofilaria transmission exists in all the Spanish territory. Highest transmission risk exists in several areas of Andalucía, Extremadura, Castilla-La Mancha, Murcia, Valencia, Aragón and Cataluña, where moderate/high temperatures coincide with extensive irrigated crops. High risk in Balearic Islands and in some points of Canary Islands, is also predicted. The lowest risk is predicted in Northern cold and scarcely or non-irrigated dry Southeastern areas. The existence of irrigations locally increases transmission risk in low rainfall areas of the Spanish territory. The model can contribute to implement rational preventive therapy guidelines in accordance with the transmission characteristics of each local area. Moreover, the use of humidity-related factors could be of interest in future predictions to be performed in countries with similar environmental characteristics.

Relationships between annual rainfall, damage symptoms and insect borer populations in mid-rotation Eucalyptus nitens and Eucalyptus globulus plantations in Tasmania: can static traps be used as an early warning device?

SummaryRoutine forest health surveillance of Eucalyptus nitens and E. globulus plantations in Tasmania has detected more frequent borer-related mortality in mid-rotation plantations in drier areas of the state. Damaging borer populations are not usually detected using traditional health surveillance techniques until mortality has occurred. Appropriately baited static traps are known to attract a wide range of stem-boring insects and might provide a means of monitoring populations in at-risk plantations. The objectives of this study were to explore the relationships between rainfall, tree stress symptoms and stem-borer-related damage symptoms in plantation eucalypts, and the nature of the associated borer populations, to determine whether static traps might provide an effective early warning system.Trees from a number of mid-rotation plantations covering a range of rainfall categories were visually assessed for a wide range of damage symptoms, and two intercept panel traps baited with α-pinene and ethanol lures were deployed in each of 19 compartments between November 2006 and March 2007. All beetles caught in the traps were identified to species level and the numbers tallied. The incidence of damage symptoms tended to be negatively correlated with mean annual rainfall and was higher in plantations from lower-rainfall areas. There were no clear relationships between aggregated trap catches of borers and annual rainfall or the incidence of damage symptoms. However, a greater range of borer species was trapped in drier areas and the number of species trapped showed a strong negative correlation with annual rainfall. There were also strong positive correlations between damage levels and the range of borer species trapped. The size of the populations of some species, in particular some of the scolytids, increased substantially with decreasing rainfall and was strongly associated with the incidence of damaged trees. Cerambycids were the only group significantly correlated with borer-specific symptoms, but further work is required to determine their utility for monitoring purposes.In vulnerable plantations an increase in the range of borer species, scolytid populations or specific indicator species caught in static traps might provide useful early warning of unacceptable levels of mortality or stem damage. As such, static trapping has the potential to monitor populations and allow for timely silvicultural intervention to ameliorate stress.

Economic analysis and environmental impacts of water harvesting techniques in the low rainfall areas of Jordan

Water harvesting has become an important priority for supporting the increasing population in the low rainfall areas of Jordan. The specific objectives of this paper are to assess the economic and environmental impacts of different water-harvesting techniques in Jordan’s Badia region. Cost benefit analysis (CBA) was used to estimate the economic impact of using water harvesting techniques. A simple simulation model was used to estimate the environmental indicators related to biomass productivity of barley and shrubs and soil erosion. The internal rate of return (IRR) showed that planting barley with water harvesting was more feasible (IRR 17%) than the farmers’ practice of planting barley (IRR 7.85%). The study concluded that the valuation and assessment of environmental benefits associated with implementing water harvesting techniques is important for justifying the public investment for these techniques in the dry areas of Jordan.

Cultivation of Aswagandha (Withania somniferaDunal) duringrabiseason is more economical as compared tokharifseason

Aswagandha (Withania somnifera dunal) is grown as late kharif crop in all over India particularly in Rajasthan, Gujarat and Madhya Pradesh. Being a midseason crop, Aswagandha cultivation is very limited and farmers are hesitating in growing it. The continuous long duration or heavy rains in starting of rainy season caused severe losses to aswagandha crop. This loss can be reduce only by choosing the low rainfall areas or by planting aswagandha after passing the heavy rainfall days of August to September month. The experiment was conducted on growing of aswagandha with two released varieties and four advance genotypes of aswagandha during kharif and rabi season in the year 2008–09 and 2009–10. The observation recorded on plant height (cm), number of branches, root length(cm), root width(cm) and dry root yield (q/ha) in both the season. All the characteristics showed slight decline in magnitude in Rabi season except Number of branches and root length (cm). Though there was a decline in dry root yield (q/ha) at genotypic level in Rabi season but the average dry root yield was 5–8 q/ha in both the season. The major diseases viz mortality of seedlings and root rot which are common in kharif season was not observed in Rabi season. The weed management and the quality of roots can easily be maintained in rabi season. Study recommended that the growing of aswagandha during rabi season is more suitable as well as more economical (farmers can save Rs 3000–4000/ha) for cultivation in the state.

Simulation of water-limited growth of the forage shrub saltbush (Atriplex nummularia Lindl.) in a low-rainfall environment of southern Australia

Old man saltbush (Atriplex nummularia Lindl.) is a useful forage shrub for livestock in the low-rainfall areas of the world, and particularly in Australia. In these semi-arid and arid environments, saltbush is valuable for increasing the production from otherwise marginal areas of the farm and during drought periods when there are few feed alternatives. The ability to predict the growth and development of perennial forages such as old man saltbush in response to rainfall, soils and farm management is necessary for farming system planning and design purposes. A field experiment was conducted at Waikerie, South Australia, to inform the development of a new forage shrub model for use in the APSIM framework. The model takes into account the common setup of saltbush plantations in alley systems, by simulating light interception and water uptake for interacting shrub and inter-row zones separately. This is done by modelling the canopy and root system development. Field data across three soil types along a landscape catena showed that the model was able to satisfactorily predict daily biomass accumulation, partitioning into leaf and woody biomass, and regrowth after grazing. The model was sensitive to properties associated with the root system, and with limited parameterisation can be tailored to simulate different clonal cultivars. The model can now be used in the APSIM framework to assess temporal and spatial dynamics of forage systems combining shrubs with herbaceous pasture components.

Influence of tree age and density on the above-ground natural durability of eucalypt species at Innisfail

SummaryAn above-ground flat-panel test was conducted at Innisfail to determine the influence of tree age on natural durability against decay of heartwood of eucalypt species grown in low-rainfall areas. After nine years’ exposure, heartwood from trees aged 30–50 or 80+ years had similar natural durabilities in Eucalyptus sideroxylon, Corymbia spp., E. cladocalyx and E. occidentalis. However, except for E. cladocalyx, the heartwood from trees less than 25 years old was less durable than that from older trees for Corymbia spp., E. leucoxylon, E. occidentalis and E. sideroxylon. Density was a useful predictor of natural durability, especially in the lower range that differentiated wood in young trees. The importance of density within the more-mature tree age ranges of 30–50 years and 80+ years was unclear, perhaps showing that a threshold age for the production of mature heartwood had been reached. Comparisons, including with the yardstick species Pinus radiata, E. regnans, E. obliqua and E. camaldulensis, suggest that E. occidentalis could be assigned a class-2 above-ground natural durability rating in AS 5604, while the class-1 rating for E. astringens should be re-examined.

Ecosystem Services: Response

C. Obst et al. provide a welcome opportunity to clarify the difference between environmental-economic cost-benefit analyses (such as ours) and environmental accounting exercises [such as the UN-SEEA ([ 1 ][1], [ 2 ][2]) initiative]. Accounting studies attempt to assess the total value of goods related to ecosystem services in a manner comparable to that used for market-priced goods in national accounts. A decline in the ecosystem services account over time signals a potential need to invest in underlying natural capital. However, such accounts do not indicate the most cost-effective form of that investment. Environmental economic analyses such as ours typically consider changes in value from the status quo that alternative investments provide, and identify those that yield higher value for money. The two approaches are complements rather than substitutes and serve differing but highly compatible elements of the decision-making process. A. Graham et al. criticize our use of “the value of nonmarket goods such as biodiversity.” Although we valued nonmarket greenhouse gas emissions and recreation, we explicitly did not attempt to define biodiversity in terms of economic values; instead, we applied a quantitative constraint prohibiting the degradation of biodiversity within our scenario analyses and examined the costs this would entail, finding them to be minor relative to other values. Graham et al. 's critique that we should not compare nonmarket values for ecosystem services with the market price of agricultural output ignores the fact that, as stated, we are conducting an economic analysis of marginal changes from the status quo and not attempting to assess the total value of food. In such assessments of changes, the use of market prices is standard ([ 3 ][3]). Indeed, there is an argument ([ 3 ][3]) that such analyses should subtract subsidies (including income support), which would reduce agricultural values ([ 4 ][4]). Graham et al. also question the possible increase in yields attributable to climate change. We do believe that UK farming will generally benefit from warmer temperatures but caution that [as detailed in ([ 5 ][5])] within areas of lower rainfall, increased drought could potentially reduce or even reverse these gains. We agree with R. Aspinall and P. Gregory that it would be better to consider net profits rather than farm gate prices, although again this would have reduced estimates of agricultural values. The need to link land use to its ecosystem service impacts favored our use of Agricultural Census ([ 6 ][6]) data, which omits profits. We are currently addressing this through a link to the Farm Business Survey ([ 7 ][7]) database. However, we disagree with the authors' contention that we should have included the added-value of post-farm food processing. Aside from the fact that the UK food processing industry is a major importer of non-UK produce, such an approach would be analogous to valuing timber at the price of fine furniture. It is the raw material value that is relevant here. Similarly, our analysis explicitly links agricultural land use to its impacts on the ecosystem service considered. 1. [↵][8] United Nations, European Commission, Food and Agriculture Organization of the United Nations, International Monetary Fund, Organisation for Economic Co-operation and Development, World Bank, “System of Environmental-Economic Accounting 2012: Central Framework, prepublication (white cover)” (2012); . 2. [↵][9] United Nations, European Commission, Organisation for Economic Co-operation and Development, World Bank, “System of Environmental-Economic Accounting 2012: Experimental Ecosystem Accounting, pre-publication (white cover)” (2013); [http://unstats.un.org/unsd/envaccounting/eea\_white\_cover.pdf][10]. 3. [↵][11] 1. H. M. Treasury , The Green Book: Appraisal and Evaluation in Central Government (The Stationery Office, London, 2003). 4. [↵][12] 1. I. J. Bateman, 2. A. A. Lovett, 3. J. S. Brainard , Applied Environmental Economics: A GIS Approach to Cost-Benefit Analysis (Cambridge Univ. Press, Cambridge, 2003). 5. [↵][13] 1. C. Fezzi 2. et al ., Env. Res. Econ., 10.1007/s10640-013-9663-x (2013). doi:10.1007/s10640-013-9663-x [OpenUrl][14][CrossRef][15] 6. [↵][16] Department for Environment, Food and Rural Affairs, June Agricultural Census (Edina, Manchester, UK, 2010). 7. [↵][17] Rural Business Research, “Farm Business Survey” (2013); [www.fbspartnership.co.uk][18]. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5 [6]: #ref-6 [7]: #ref-7 [8]: #xref-ref-1-1 View reference 1 in text [9]: #xref-ref-2-1 View reference 2 in text [10]: http://unstats.un.org/unsd/envaccounting/eea_white_cover.pdf [11]: #xref-ref-3-1 View reference 3 in text [12]: #xref-ref-4-1 View reference 4 in text [13]: #xref-ref-5-1 View reference 5 in text [14]: {openurl}?query=rft.jtitle%253DEnv.%2BRes.%2BEcon.%26rft_id%253Dinfo%253Adoi%252F10.1007%252Fs10640-013-9663-x%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [15]: /lookup/external-ref?access_num=10.1007/s10640-013-9663-x&link_type=DOI [16]: #xref-ref-6-1 View reference 6 in text [17]: #xref-ref-7-1 View reference 7 in text [18]: http://www.fbspartnership.co.uk

Does aridity influence the morphology, distribution and accumulation of calcium oxalate crystals in Acacia (Leguminosae: Mimosoideae)?

Calcium oxalate (CaOx) crystals are a common natural feature of many plant families, including the Leguminosae. The functional role of crystals and the mechanisms that underlie their deposition remain largely unresolved. In several species, the seasonal deposition of crystals has been observed. To gain insight into the effects of rainfall on crystal formation, the morphology, distribution and accumulation of calcium oxalate crystals in phyllodes of the leguminous Acacia sect. Juliflorae (Benth.) C. Moore & Betche from four climate zones along an aridity gradient, was investigated. The shapes of crystals, which include rare Rosanoffian morphologies, were constant between species from different climate zones, implying that morphology was not affected by rainfall. The distribution and accumulation of CaOx crystals, however, did appear to be climate-related. Distribution was primarily governed by vein density, an architectural trait which has evolved in higher plants in response to increasing aridity. Furthermore, crystals were more abundant in acacias from low rainfall areas, and in phyllodes containing high concentrations of calcium, suggesting that both aridity and soil calcium levels play important roles in the precipitation of CaOx. As crystal formation appears to be calcium-induced, we propose that CaOx crystals in Acacia most likely function in bulk calcium regulation.

Toward Sustainable Agriculture: An Evaluation of Compost and Inorganic Fertilizer on Soil Nutrient Status and Productivity of Three Maize Varieties Across Multiple Sites in Malawi

Declining soil fertility is a major constraint limiting African agriculture. In a four-year (2007–2011) on-farm study in Malawi, we compared the effects of compost (bokash and liquid manure) and compost (bokash) in combination with low doses of inorganic fertilizer with recommended inorganic fertilizer rates on the performance of three maize genotypes. Compost use resulted in increases in soil organic carbon, total nitrogen, available phosphorus, and soil pH. Chemical analysis of both bokash and liquid manure indicated the need to improve compost quality. In low rainfall areas and sites characterized by poor soils but with good quality compost, maize yields did not show significant differences between chemical fertilizer and bokash plus urea. Although it was not possible to quantify soil-water balance studies in these on-farm trials, it can be assumed that bokash helped in soil-water conservation in low rainfall areas, thereby, improving the ability of maize to withstand conditions of water stress compared with the effects of NPK fertilizer. While SC627 gave 29% higher yields under chemical fertilizer compared with bokash and urea, yields of both local and ZM621 were similar between the two treatments, suggesting that local and ZM621 are less responsive to fertility inputs. Our study showed that for maize hybrid variety, SC627, lower vulnerability to low yields is obtained from the application of chemical fertilizer. For both local maize and OPV variety ZM621, less risk of a lower yield is obtained when the plots received applications of a combination of bokash and urea rather than a total reliance on chemical fertilizer. The results of this study call for a more nuanced approach than the current recommendation permits.

Opportunistic Mediterranean agriculture – Using ephemeral pasture legumes to utilize summer rainfall

The wet winters and summer droughts of dry Mediterranean-type climates create a highly seasonal supply of feed for livestock. Much of the forage value of winter-active annual pastures and crop residues is realized as dry feed during summer–autumn. Sporadic summer–autumn rainfall rapidly degrades the quality of dry plant residues. In low rainfall areas of the southern Australian wheatbelt, there are no well-adapted crops or pastures to convert summer rainfall into high-quality green feed and supplementary feeding is required to maintain livestock condition. We therefore investigated two undomesticated ephemeral legumes (Cullen cinereum and Cullen graveolens). In a field experiment, the ephemerals were dormant in winter–spring and responded strongly to summer rainfall, with 0.45–0.82tha–1 of shoot dry weight produced over summer. Extrapolation of regional historic rainfall records showed similar or greater summer–autumn rainfall in 40% of years and also suggested that conditions will probably be too dry for perennial pastures such as Medicago sativa (lucerne) to persist in up to 60% of years. An analysis using MIDAS, a bio-economic model, suggested that ephemerals could increase total farm profit and stocking rates (10.3% and 7.7%, respectively), and decrease supplementary feeding of grain by >50% by providing high quality feed in years that summer–autumn rainfall occurs. We suggest there is considerable potential for ephemeral legumes to contribute to the sustainability of mixed agriculture in dry Mediterranean-type climates by utilizing sporadic summer rainfall whilst complementing existing annual pasture and cropping systems.

Impacts of prescribed fire on soil loss and soil quality: An assessment based on an experimentally-burned catchment in central Portugal

Prescribed (controlled) fire has recently been adopted as an important wildfire-fighting strategy in the Mediterranean. Relatively little research, however, has assessed its impacts on soil erosion and soil quality. This paper investigates hillslope-scale losses of soil, organic matter and selected nutrients before and after a ‘worst-case scenario’ prescribed fire in a steep, shrub-vegetated catchment with thin stony soil in central Portugal. Comparison is made with soil erosion measured: (1) on a nearby hillslope burned by wildfire and monitored at the hillslope scale; and (2) on long-unburned terrain at small-plot, hillslope- and catchment-scales. Hillslope-scale pre- and post-fire soil erosion was recorded over periods of 6weeks to 5months for (1) 9.5months pre-fire and 27months post-fire in the prescribed fire catchment, and (2) c. 3years post-fire at the wildfire site. Organic matter content, pH, total N, K2O, P2O5, Ca2+ and Mg2+ were measured in the eroded sediment and in pre- and post-prescribed fire surface soil. Results indicate that: (1) both the prescribed fire and the wildfire caused expected marked increases in erosion compared with unburned terrain; and (2) the hillslope-scale post-prescribed fire soil losses (up to 2.41tha−1yr−1) exceeded many reported plot-scale post-prescribed fire and post-wildfire erosion rates in the Mediterranean. As a comparison, post-fire erosion for both fire types was less than that caused by some other forms of common soil disturbance (e.g. types of tillage) and even that on undisturbed shrubland in low rainfall areas of the region. Total estimated post-prescribed fire particulate losses of organic matter and nutrients represent only 0.2–2.9% of the content in the upper 2cm of soil, suggesting only a modest fire effect on soil quality, although this may reflect in part a lack of extreme rainfall events following the fire. The longer-term implications for soil conservation of repeated prescribed fire in the Mediterranean are explored and future research priorities identified.

Food security, climate change, and sustainable land management. A review

Agriculture production in developing countries must be increased to meet food demand for a growing population. Earlier literature suggests that sustainable land management could increase food production without degrading soil and water resources. Improved agronomic practices include organic fertilization, minimum soil disturbance, and incorporation of residues, terraces, water harvesting and conservation, and agroforestry. These practices can also deliver co-benefits in the form of reduced greenhouse gas emissions and enhanced carbon storage in soils and biomass. Here, we review 160 studies reporting original field data on the yield effects of sustainable land management practices sequestering soil carbon. The major points are: (1) sustainable land management generally leads to increased yields, although the magnitude and variability of results varies by specific practice and agro-climatic conditions. For instance, yield effects are in some cases negative for improved fallows, terraces, minimum tillage, and live fences. Whereas, positive yield effects are observed consistently for cover crops, organic fertilizer, mulching, and water harvesting. Yields are also generally higher in areas of low and variable rainfall. (2) Isolating the yield effects of individual practices is complicated by the adoption of combinations or “packages” of sustainable land management options. (3) Sustainable land management generally increases soil carbon sequestration. Agroforestry increases aboveground C sequestration and organic fertilization reduces CO2 emissions. (4) Rainfall distribution is a key determinant of the mitigation effects of adopting specific sustainable land management practices. Mitigation effects of adopting sustainable land management are higher in higher rainfall areas, with the exception of water management.

Changes in woody species composition following establishing exclosures on grazing lands in the lowlands of Northern Ethiopia

Restoring vegetation in low rainfall areas is difficult and urges the need to design an effective and low-cost method of vegetation restoration. This study was undertaken in the lowlands of northern Ethiopia to: (1) investigate how exclosure age affects restoration of degraded native plant species richness, diversity and aboveground standing biomass, and (2) identify soil characteristics, which affect effectiveness of exclosures to restore degraded native vegetation. Replicated (n = 3) 5-, 10- and 15- year-old exclosures were selected and each exclosure was paired with an adjacent grazing land to detect changes in vegetation variables following establishing exclosures on communal grazing lands. All exclosures displayed higher species richness, diversity and aboveground biomass when compared to the adjacent grazing lands. Results on vegetation composition indicate that all exclosures are at early stage of succession. In all exclosures and grazing lands, vegetation variables displayed significant (p < 0.05) correlations with soil variables indicating that consideration of soil fertility will help enhance natural regeneration in exclosures. Our study indicates that the establishment of exclosures on degraded communal grazing lands can be effective in restoring degraded native vegetations, and with time, exclosures may obtain an important role as source of seeds of indigenous woody species. Key words : Grazing pressure, land degradation, land use conversion, native vegetation, soil variables, vegetation restoration.

Multiple Impact of Integrated Watershed Management in Low Rainfall Semi-Arid Region: A Case Study from Eastern Rajasthan, India

The agriculture in low rainfall areas of eastern Rajasthan, India is characterized by high risks from drought, degraded natural resources and pervasive poverty, food insecurity and malnutrition. In this region, water is the main limiting factor for upgrading rainfed agriculture. For such areas integrated watershed management is recognized as a potential approach for agriculture growth and rehabilitation of fragile and degraded lands. At Gokulpura-Goverdhanpura village in Bundi eastern Rajasthan, India an integrated watershed project was implemented using the holistic systems approach. This paper discusses the impacts of this watershed program on bio-physical, socio-economic, environmental and ecological parameters. Results indicate that due to watershed interventions the groundwater availability has substantially increased which brought changes in cropping patterns with high value crops. Significant increases in irrigated area, cropping intensity along with diversification of crops from traditional to commercial cash crops were recorded. The watershed program also significantly improved the socio-economic status of the watershed community. It has increased the income and reduced poverty of the people in the watershed. The watershed interventions generated good employment opportunities and significantly reduced the migration of both skilled and unskilled labor from the watershed village to urban areas. It has also improved the environmental quality and ecological status in the watershed. The watershed interventions increased the vegetative index or greenery, reduced runoff, soil loss, and land degradations and improved the bio-diversity in fragile ecosystems. Overall, the integrated watershed program at Gokulpura-Goverdhanpura provided resilience by ensuring continued and sustainable multiple outputs, besides soil and water conservation and other positive environmental effects.

Improved decision-making on irrigation farming in arid zones using a system dynamics model

The Sandveld region in the Western Cape is a low rainfall area dominated by agricultural production using groundwater resources. The rise in agricultural production in the Sandveld has led to questions regarding the region’s ecological sustainability. We developed a system dynamics model for the Sandveld system which captures land-use change, agricultural production, and groundwater abstraction and recharge. Using this model, we find little evidence that pressures on livelihoods result, either currently or in the immediate future, from ecological feedback effects. The model does indicate that the highest risks are associated with the financial viability of agriculture, in its present form, in the region. With lower margins, a drive towards economies of scale in agricultural production is more likely in the future. This process has had severe implications in some sectors already, with a 39% decrease in the number of potato producers in the Sandveld region between 2003 and 2009. These results highlight that an integrated approach to agricultural, economic and environmental management and planning is needed to capture the economic and ecological complexity and dynamics of the Sandveld system.

Ecological characteristics and cultivar influence optimal plant density of East African highland bananas (Musa spp., AAA-EA) in low input cropping systems

Numerous studies have been conducted on the effects of plant density on growth and yield of dessert bananas in the humid tropics, but effects of plant densities in relations with ecological characteristics in low input East African highland banana (Musa spp., AAA-EA genome) cropping systems have not been reported. On-station field experiments were conducted in three contrasting agro-ecological sites of Rwanda (Kibungo low rainfall with medium soil fertility, Rubona high rainfall with low soil fertility and Ruhengeri high rainfall with high soil fertility) to explore germplasm×environment interactions. Five different plant densities (plantsha−1): 1428, 2500, 3333, 4444 and 5000 and two cooking (“Ingaju”, “Injagi”) and one beer (“Intuntu”) cultivars were investigated. The effect of plant density on plant performance (growth and yield) over two cropping cycles in low input systems was determined. The effects of site×cultivar and site×density interactions on yield traits were significant (p<0.05). Annual yield increased with increasing plant density but strongly depended on agro-ecological site (from 6.1 to 9.2tha−1yr−1 at Kibungo, 9.5 to 21.5tha−1yr−1 at Rubona and 7.0 to 25.0tha−1yr−1 at Ruhengeri). Yields of beer cultivars increased with density, but those of cooking cultivars decreased. Maximum yields were attained at 4444plantsha−1 at Kibungo and Rubona whilst yields increased linearly beyond this level at Ruhengeri. Crop cycle duration was prolonged with increasing plant density. Relationships between bunch yield, the total above ground dry matter yields and soil chemical properties suggest that nutrient deficiencies were larger at Kibungo (e.g. K) and Rubona (e.g. K, P, Ca and Mg) compared with Ruhengeri, where yield correlated significantly with leaf area index (LAI). LAI increases up to 4, where 95% of solar radiation was intercepted by the crop canopy, indicating that increasing the LAI above 4 would have little effect on production. Evaporation was much greater at lower rainfall areas (e.g. Kibungo) and accompanied by negative annual water deficit (−135mmyr−1) than at high rainfall areas (e.g. Ruhengeri) with positive water surplus (382mmyr−1). Growing degree days from planting to bunch harvest were higher at Kibungo (3675°C days) but much less at the Ruhengeri cooler site (1729°C days), implying temperature is not restrictive at Ruhengeri. This study showed that the optimal density for bananas depends on water availability, soil fertility and cultivar, which serves as an entry point to maximize yield potential for the East African smallholder farmers rather than using a uniform blanket recommended density. We suggest that agronomic optimal plant density is lower (<4444plantsha−1) in low rainfall (<1000mmyr−1) and less fertile areas but seem to be higher (>5000plantsha−1) in areas with high fertility which receive high rainfall (>1300mmyr−1).

Drought risk assessment using remote sensing and GIS techniques

Beginning with a discussion of drought definitions, this review paper attempts to provide a review of fundamental concepts of drought, classification of droughts, drought indices, and the role of remote sensing and geographic information systems for drought evaluation. Owing to the rise in water demand and looming climate change, recent years have witnessed much focus on global drought scenarios. As a natural hazard, drought is best characterized by multiple climatological and hydrological parameters. An understanding of the relationships between these two sets of parameters is necessary to develop measures for mitigating the impacts of droughts. Droughts are recognized as an environmental disaster and have attracted the attention of environmentalists, ecologists, hydrologists, meteorologists, geologists, and agricultural scientists. Temperatures; high winds; low relative humidity; and timing and characteristics of rains, including distribution of rainy days during crop growing seasons, intensity, and duration of rain, and onset and termination, play a significant role in the occurrence of droughts. In contrast to aridity, which is a permanent feature of climate and is restricted to low rainfall areas, a drought is a temporary aberration. Often, there is confusion between a heat wave and a drought, and the distinction is emphasized between heat wave and drought, noting that a typical time scale associated with a heat wave is on the order of a week, while a drought may persist for months or even years. The combination of a heat wave and a drought has dire socio-economic consequences. Drought risk is a product of a region’s exposure to the natural hazard and its vulnerability to extended periods of water shortage. If nations and regions are to make progress in reducing the serious consequences of drought, they must improve their understanding of the hazard and the factors that influence vulnerability. It is critical for drought-prone regions to better understand their drought climatology (i.e., the probability of drought at different levels of intensity and duration) and establish comprehensive and integrated drought information system that incorporates climate, soil, and water supply factors such as precipitation, temperature, soil moisture, snow pack, reservoir and lake levels, ground water levels, and stream flow. All drought-prone nations should develop national drought policies and preparedness plans that place emphasis on risk management rather than following the traditional approach of crisis management, where the emphasis is on reactive, emergency response measures. Crisis management decreases self-reliance and increases dependence on government and donors.