Predicting the spatial distribution of ground flora on large domains using a hierarchical Bayesian model

Accomodation of important sources of uncertainty in ecological models is essential to realistically predicting ecological processes. The purpose of this project is to develop a robust methodology for modeling natural processes on a landscape while accounting for the variability in a process by utilizing environmental and spatial random effects. A hierarchical Bayesian framework has allowed the simultaneous integration of these effects. This framework naturally assumes variables to be random and the posterior distribution of the model provides probabilistic information about the process. Two species in the genus Desmodium were used as examples to illustrate the utility of the model in Southeast Missouri, USA. In addition, two validation techniques were applied to evaluate the qualitative and quantitative characteristics of the predictions.This revised version was published online in May 2005 with corrections to the Cover Date.     

Farmers' perspectives of rodent damage and management from the highlands of Tigray,Northern Ethiopian

A farmers' knowledge, attitude and practice (KAP) survey was conducted in the highlands of Tigray, northern Ethiopia, to better understand rodent damage and rodent management from the farmers' perspective. Farmers (n = 191) from Dogu'a Temben district, were interviewed using a semi-structured questionnaire. The large majority of the farmers stated that rodents are the main pests in crop fields (92.1%) and storage (88.5%). The farmers (64.2%) reported they experienced 100–500 kg ha⁻¹ damage in crop fields, which is equivalent to 8.9–44.7% loss in annual production. There was some overlap between the most common crops grown in the highlands and the most common crops susceptible to rodent attack. Farmers identified barley as the crop most susceptible to rodent attack (76.4%) and the booting stage as the crop developmental stage with the highest rodent abundance and damage. Rodenticide application was the most commonly practiced management strategy in crop fields (51.8%); in storage, farmers mainly keep domestic cats around granaries (80.6%). We recommend a reduction in reliance on chemical rodenticide in crop fields and a shift to a more sustainable rodent management approach to reduce rodent numbers and damage.     

Nature and importance of weeds in sorghum in the Yemen Arab Republic

Abstract

Grain sorghum (Sorghum bicolor (L.) Moench) is the dominant crop in North Yemen agriculture, covering about 70–80% of the arable land. Weed control is still carried out mainly by hand. Many of the weeds are used as fodder for animals. A total of 137 weeds was collected in sorghum. Most frequent were Cynodon dactylon (L.) Pers. and Cyperus mtundus (L): their importance decreased, however, under a well‐established sorghum crop providing good shade cover and under conditions of increased crop fertilization with mineral nitrogen. Under these conditions, for example, Commelina spp. and Flaveria trinerva (Spreng.) Mohr became commoner. Thus increased use of nitrogen altered the nature and hierarchy of the weed flora. Relationships between the indicator figures of the weeds and the habitat, as defined by Ellenberg, were confirmed. Traditional methods of weed control have so far worked well, as witness an average cover of 60% sorghum and 20% weeds. In future, however, rising costs and labour shortages will increase the demand for less time‐consuming weed control strategies.     

Evaluation of a Rapid Field Test Method for Assessing Nitrogen Status in Potato Plant Tissue in Rural Communities in the Bolivian Andean Highlands

The relatively poor accessibility, high costs, long turnaround time for analysis, and lack of information about soil and plant testing in the Andean highland region (Altiplano) of Bolivia has hampered informed and timely nutrient management decisions for potato (Solanum tuberosum L.) crops. The objective of this study was to determine if the Cardy nitrate meter (Horiba Ltd., Kyoto, Japan), a low-cost, portable, and rapid field test method, could be used to improve nitrogen (N) fertility management among isolated rural indigenous communities at different elevations in this rugged semi-arid environment. Fully matured leaf petioles were sampled at blooming time from potato trials established in three communities during the 2006–2007 and 2007–2008 growing seasons. Those trials were composed of 12 fertility treatments (i.e., an unfertilized control and different combinations of sheep and cow manure, inorganic fertilizer, commercial household/urban compost, and a commercial microbial activator soil amendment) arranged in a randomized complete block design with four replications. In general, in both growing seasons and in all communities, nitrate measured in the sap of leaf petioles by the Cardy meter had relatively low but significant correlations with leaf petiole total N (ranging from r² = 0.07 to r² = 0.60 across seasons and communities) and with total fresh tuber yield (ranging from r² = 0.11 to r² = 0.50 across seasons and communities). However, some problems were encountered with being able to consistently calibrate the meter with supplied standards prior to each use of the meter. These results indicate that the Cardy ion meter might be an effective tool for potato growers or agricultural professionals working in the Altiplano of Bolivia if further research can be conducted to determine if the meter is consistent for diverse sites in the Altiplano and is practical for the cultural, economic, and environmental conditions of the region.     

Feeding strategies for small-scale dairy systems based on perennial (<Emphasis Type="Italic">Lolium perenne</Emphasis>) or annual (<Emphasis Type="Italic">Lolium multiflorum</Emphasis>) ryegrass in the central highlands of Mexico

Small-scale dairying is an option for campesinos in Mexico. The costs of feeding are high and strategies based on quality forages are a priority. The performance, agronomic variables and feeding costs were evaluated for dairy cows continuously grazing perennial ryegrass–white clover for 9 h/day (PRG) or fed cut herbage from annual ryegrass for 8 weeks followed by 9 h/day for 6 weeks on a tethered rotational grazing pattern (ARG). All cows received 3 kg/day of an 18% crude protein (CP) concentrate. A 14-week split-plot on-farm experiment was designed with 10 cows from two participating farmers, and 1.5 ha per strategy. Milk yield was recorded weekly and milk composition, live weight and body condition score were recorded every 14 days. Net herbage accumulation was greater for ARG (8222 kg organic matter (OM)/ha) than for PRG (5915 kg OM/ha) (p < 0.05), with higher CP in PRG (p < 0.05). Milk yield was 19 kg/cow per day for PRG and 15.9 kg/cow per day for ARG (p > 0.05). Over 14 weeks, PRG produced 1422 kg more milk. There were no differences for live weight or condition score (p > 0.05), but linear regression shows a live weight gain of 0.200 kg/cow per day for PRG. Protein and fat content showed no differences (p > 0.05), but milk fat content in PRG was below standard. ARG had 60% higher costs, and margins were 38% higher in PRG. ARG has a place in rain-fed fields. The results provide viable options for improving these systems that may be suitable in their socio-economic context and their social and personal objectives.     

Carbon content in vegetation,litter, and soil under 10 different land-use and land-cover classes in the Central Highlands of Michoacan,Mexico

In this study we estimated the carbon content in vegetation, litter, and soil, under 10 different classes of land-use and land-cover classes (LU/LC) in the Purepecha Region, located in the Central Highlands of México. Forests in this area are representative of the montane forests of Central and Southern Mexico and are subject to rapid degradation and deforestation by human pressure.     

Soil erosion under simulated rainfall in relation to phenological stages of soybeans and tillage methods in Lages, SC, Brazil

Soil tillage may increase vulnerability to water erosion, whereas no tillage and other conservation cultivation techniques are viewed as strategies to control soil erosion. The objective of this research was to quantify runoff and soil losses by water erosion under different soil tillage systems at the Santa Catarina Highlands, southern Brazil. A field study was carried out using a rotating-boom rainfall simulator with 64 mm h⁻¹ rainfall intensity on a Typic Hapludox, between April 2003 and May 2004. Five rainfall tests were applied along successive cropstages. Surface cover was none (fallow) or soybean (Glycine max, L.). Five treatments were investigated, replicated twice. These treatments were conventional tillage on bare soil (BS) as a control treatment and the following treatments under soybean: conventional tillage (CT), no tillage over burnt crop residues on never before cultivated land (NT-B), no tillage over desiccated crop residues, also on never before cultivated land (NT-D) and traditional no tillage over desiccated crop residues on a soil tilled 4 years before this experiment (NT-PT). Water losses by surface runoff seemed to be more influenced by vegetative crop stadium than by tillage system and consequently a wide range of variation in surface runoff was found, following successive cropstages. The most efficient tillage system in reducing surface runoff and soil losses was no tillage, particularly the NT-PT treatment. Sediment losses were more influenced by tillage system than water losses. In the NT-B, NT-D and NT-PT treatments the rate of sediment losses along the crop vegetative cycle showed a tendency to increase from the first to the second cropstages and later to decrease from the third cropstage onwards. In the conventionally tilled treatment (CT) soil losses were greater than in any of the no tillage treatments (NT-D, NT-B and NT-PT) during the initial growth periods, but at the end of the vegetative period differences in sediment rates between tilled and non-tilled treatments tended to be smaller. In the BS control treatment, soil losses progressively increased following the vegetative growth season of soybean.     

Silage from maize (Zea mays), annual ryegrass (Lolium multiflorum) or their mixture in the dry season feeding of grazing dairy cows in small-scale dairy production systems in the Highlands of Mexico

Small-scale dairy systems based on grazing have dry-season herbage shortages. A repeated 3 × 3 Latin Square experiment evaluated grazing with silage from maize (MS), annual ryegrass (ARG) or a mixture (MIX) with 9 cows with 3 week periods; continuously grazed at 3.6 cows/ha with 3.6 kg DM/day of concentrate. Treatments were 7 kg DM of MS, ARG or a 2 MS:1 ARG mixture. Milk yield (MY), milk composition, live-weight, body condition, silage and concentrate intake were recorded. Herbage DM intake was estimated indirectly. Activity budgets were done for economic analysis. MY on MS (21.5 kg/cow/d) was 0.06 higher than on ARG (P < 0.09) with no differences on MIX. There were no differences for milk fat, milk protein, or body condition score. Live-weight on ARG was higher (P < 0.01) than on MS or MIX. Silage intake was higher (P < 0.01) on ARG and MS than on MIX. Herbage intake was lower (P < 0.05) on MS, compared with MIX and ARG. Total DM intake on ARG was higher than MS (P < 0.01), and MIX in between. MS resulted in 0.12 higher economic returns over ARG which had highest costs. Annual ryegrass may have a place in small-scale systems, but not as silage due to higher costs.     

Restoring landscapes of fear with wolves in the Scottish Highlands

The absence of an organism from a landscape for a long time can be a major barrier to the restoration of that species due to factors such as environmental conditions changing since extinction. This can make it difficult to assess the feasibility of reintroduction when an extirpated species cannot, by definition, be observed in the landscape of interest. In such situations, two important options for conservation scientists include: (1) to draw on insights from analogous ecosystems where the organism is extant, or where it has been successfully reintroduced and (2) to undertake research into the reintroduction in the location of interest under controlled experimental conditions.The idea of reintroducing wolves (Canis lupus) to the Scottish Highlands provides an excellent case study of such a situation. A key argument for reintroduction has been that native red deer (Cervus elaphus) numbers, considered by many to be ecologically unsustainable, would be reduced through wolf predation. To date, research into the ecological value of reintroduction has focused on this important issue. However, new research, emerging from wolf reintroduction projects in North America, suggests that nonlethal ‘behaviourally-mediated’ effects of wolves also have a profound effect on deer behaviour and consequently on the ecosystems in which they live. In short, deer avoid places or browse less where there is a high risk of wolf predation, which allows previously inhibited tree regeneration. The implications for wolf reintroduction in Scotland are that changes in deer behaviour could be as important as lethal effects, and that fewer wolves may be needed than indicated by predator–prey modelling to have significant positive impacts on ecosystems in the Scottish Highlands. Understanding the relative likely contributions of both lethal and nonlethal effects in the Scottish context will be challenging because nonlethal impacts result from an interaction between deer behaviour in response to wolf predation and particular landscapes and ecosystem features. While a full reintroduction may be far off, research must begin in the near term. There would be considerable scientific merit in establishing a large, controlled experiment (for example on an island or in a fenced area) in the Scottish Highlands to examine the relative lethal and nonlethal effects of wolves on deer and ecosystem restoration. In this paper, a long-term pathway for scientific research to provide sound ecological evidence to inform future decision-makers is proposed.