Comparison of net ecosystem CO2 exchange in two peatlands in western Canada with contrasting dominant vegetation, Sphagnum and Carex

Net ecosystem carbon dioxide exchange was measured in two contrasting peatlands in northern Alberta, Canada using the eddy covariance technique during the growing season (May–October). Sphagnum spp. made up approximately 66% of the total LAI (1.52 m² m⁻²) at the poor fen and the total N content of Sphagnum capitula was 7.8 mg g⁻¹ at the peak of the growing season. In contrast, the dominant plant species at the extreme-rich fen site, the perennial sedge, Carex lasiocarpa, accounted for approximately 60% of the total LAI (1.09 m² m⁻²), and had leaf total N content of 19.3 mg g⁻¹ at peak biomass. In addition, the peak aboveground biomass was higher at the poor fen (230.9 g m⁻²) than at the extreme-rich fen (157.1 g m⁻²). Both sites had maximum daily rates of net CO₂ uptake of approximately 5 μmol m⁻² s⁻¹, and typical nighttime rates of CO₂ loss of approximately 2 μmol m⁻² s⁻¹ during the peak of the growing season. Calculations of maximum photosynthetic and respiratory capacity were consistently higher at the extreme-rich fen. The poor fen was a net sink for CO₂ during 4 of the 6 months (peaking at 44 g C m⁻² in July), while only slight net losses of CO₂ (3 g C m⁻²) occurred in May and September. In contrast, the extreme-rich fen was calculated to be a significant net sink for CO₂ only during 2 months of the growing season (peaking at 30 g C m⁻² in August), while significant net losses of CO₂ occurred in May (8 g C m⁻²) and in October (13 g C m⁻²). The plant species at the poor fen site were active earlier and later in the growing season, while it took longer for C. lasiocarpa to develop leaf tissue, and leaf senescence and reduction in photosynthetic activity occurred earlier in the fall at the extreme-rich fen. When integrated over the 6-month growing season, the poor fen was a net sink (90 g C m⁻²) that was three times larger than the extreme-rich fen (31 g C m⁻²). The ratio of cumulative total ecosystem respiration to gross primary production was 0.7 at the poor fen and 0.9 at the extreme-rich fen.     

Wild potato (Solanum sect.Petota) germplasm collecting expedition to Mexico in 1993, with special reference toSolanum bulbocastanum Dunal andS. cardiophyllum Lindley

Summary A joint Mexico/United States expedition collected wild potato (Solanum sect.Petota) germplasm in Mexico between August 1–31, 1993. The purpose of the expedition was to expand germplasm and herbarium collections ofS. bulbocastanum andS. cardiophyllum. Collections were made from west-central to southern Mexico, and comprised 19 true seed and 37 tuber collections (45 collections in total) of 9 species and two putative natural hybrids.     

PRE-PLANT VERSUS IN-SEASON APPLICATION OF PHOSPHORUS FERTILIZER FOR RUSSET BURBANK POTATO GROWN IN CALCAREOUS SOIL

Potato (Solanum tuberosum L.) has active surface roots that may enable phosphorus (P) fertigation. Fertilizer trials were conducted in 2002–2004 with 0 or 224 kg P₂O₅ ha^?1 applied as incorporated pre-plant broadcast, in-season fertigation, or split application (half pre-plant and half in-season). All of the P fertilization treatments increased petiole P concentration over the untreated control in all three years of the trial, but only the pre-plant application resulted in significant increases in US No. 1 and Total yields. Both the pre-plant and the split application resulted in significant increases in Marketable yield (US No. 1 &; 2). These results show that P fertilizer should be applied and incorporated prior to planting. Fertigated P does enter into the plant, but the relative efficiency of this method of application for P is poor with regard to important yield and quality parameters and application as such should be limited to “rescue” situations.     

Attenuation of Actinobacillus pleuropneumoniae by inactivation of aroQ.

Actinobacillus pleuropneumoniae is the aetiological agent of porcine pleuropneumonia, a disease resulting in morbidity and mortality of pigs and accordingly economic losses within the swine industry. In order to construct a potential vaccine strain of A. pleuropneumoniae for control of this disease, the aroQ gene, required for the aromatic biosynthetic pathway, was targeted for inactivation. The resulting strain was tested for virulence within pigs. The aroQ gene and an adjacent gene, dapD, were cloned. A recombination cassette, for inactivation of aroQ, was constructed from these cloned genes by inserting an ampicillin resistance gene and this was transformed into A. pleuropneumoniae. Integration of this construct into the chromosomal location of aroQ and disruption of the aroQ/dapD gene arrangement was confirmed through PCR and Southern analysis. The resulting HS25 aroQ mutants were unable to grow in a chemically defined medium and following intratracheal delivery to pigs were only able to induce lung lesions when given at a level 10,000 times greater than that of the parent strain. Complementation with an in trans, functional, aroQ gene restored the ability of the mutant strain to grow in a chemically defined medium and virulence, when tested in pigs, confirming attenuation results from inactivation of aroQ. In conclusion, this work has constructed a defined mutant of A. pleuropneumoniae that is attenuated and may be safely delivered live to pigs.     

Lethal temperature for pinewood nematode, Bursaphelenchus xylophilus, in infested wood using radio frequency (RF) energy

We evaluated radio frequency (RF) dielectric heating for eradication of pinewood nematodes (PWN) in infested wood. Thirteen temperatures were tested (from ambient to 70 °C) on small wood samples (2.5 × 3.8 × 0.64 cm) to determine the minimum lethal temperature (100 % mortality), which was 56 °C [based on infra-red (IR) thermal images data 55.5–57.4 °C] with a 1 min hold time. We also used thermal probes inside the wood to confirm that temperatures were ≥56 °C. Thirty additional samples were tested bracketing the minimum lethal temperature using 54, 56 and 58 °C with additional replications to produce the minimum sample size equivalent of 100 % mortality of at least 93,616 nematodes to satisfy the Probit 9 efficacy requirement. This minimum lethal temperature was further verified by treating infested large wood blocks (10.2 × 10.2 × 25.4 cm). All samples that met or exceeded the 56 °C lethal temperature for the required 1 min hold time (as measured by probes inserted in the wood and on the wood surface by IR) produced 100 % mortality. The sample size required to show Probit 9 efficacy was also satisfied. This study supports the consideration of RF in addition to microwave (MW) dielectric heating as alternative treatments of wood packaging material for inclusion in ISPM No. 15, provided the treatment delivers the target lethal temperature throughout the profile of the material in industrial scale operations.     

Effect of altered carbohydrate traits in hulless barley (Hordeum vulgare L.) on nutrient profiles and availability and nitrogen to energy synchronization

Four hulless barley cultivars (zero-amylose waxy, CDC Fibar; 5%-amylose waxy, CDC Rattan; normal-amylose, CDC McGwire and high-amylose, HB08302) were developed at the Crop Development Centre, University of Saskatchewan, with differences in carbohydrates traits on the basis of amylose (1–20% DM) and β-glucan (5–10% DM) content. The objectives of this research were to determine: 1) the effect of the alteration of these carbohydrate traits in hulless barley on nutrient availability in ruminants, and 2) carbohydrate structure conformation on hourly effective rumen degradation ratio, in comparison with hulled barley-CDC Copeland. Among the hulless barley lines, HB08302 was greater (P < 0.05) in rumen bypass crude protein (BCP: 52.1% CP), effective degradability (ED) of neutral detergent fibre (EDNDF: 74 g/kg DM) than these in CDC Fibar, whereas CDC Fibar showed greater (P < 0.05) effective degradable crude protein (EDCP: 90 g/kg DM) than the other hulless barley lines. Compared with hulless barley, the hulled CDC Copeland showed relatively greater (P < 0.05) BNDF (62.5% NDF or 98 g/kg DM), starch degradation rate (K_d: 17.4%/h) and EDST (75.9% ST) but reduced (P < 0.05) rumen undegradable protein (RUP: 49 g/kg DM). With the respect to hourly effective degradation (ED) ratios, hulless barley cultivars exhibited relatively optimal hourly ED ratios, ranging from 23 to 34 g N/kg CHO, higher than the hulled barley. Among hulless barley cultivars, CDC Fibar and Rattan had the highest (P < 0.05) ratios (34 g N/kg CHO), while the ratio for CDC McGwire (23 g N/kg CHO) was the lowest (P > 0.05). In conclusion, hulless barley lines with altered carbohydrate traits have the potential to increase rumen nutrient availability to ruminants. The altered carbohydrate conformation of hulless barley affected hourly ED ratios, thus affecting rumen nitrogen to energy synchronization.     

Predicted truly absorbed protein supply to dairy cattle from hulless barley (Hordeum vulgare L.) with altered carbohydrate traits with multi-year samples

Hulless barley breeding lines varying in amylose (1–20% DM) and β-glucan content (5–10% DM) have been developed at the Crop Development Centre, Canada. The objectives of this large-scale study were to 1) determine and confirm the effect of these new hulless barley lines (zero-amylose waxy, CDC Fibar; 5%-amylose waxy, CDC Rattan; normal-amylose, CDC McGwire and high-amylose, HB08302) with altered carbohydrate traits on 1) metabolic characteristics of protein; 2) intestinal digestion of various nutrients and 3) modeling nutrient supply from these barley varieties by using NRC Dairy 2001 model and DVE/OEB system. CDC Copeland was included as a hulled barley control. Among the hulless barley lines, CDC Fibar contained the highest and CDC McGwire contained the lowest total digestible protein (TDP: 147 vs. 116 g/kg DM). HB08302 was greater (P < 0.05) in intestinal digestible protein (IDP: 40.6% RUP) but relatively lower (P < 0.05) in total digestible protein (TDP: 120 g/kg DM). Compared with hulless barley, hulled barley showed relatively lower (P < 0.05) intestinal digestible protein (38 vs. 53 g/kg DM) and total digestible protein (102 vs. 129 g/kg DM). In modeling nutrient supply from the DVE/OEB system, the results showed hulled barley was lower (P < 0.01) in true protein supplied to the small intestine (TPSI: 127 vs. 142 g/kg DM), lower in truly absorbed rumen bypassed feed protein in small intestine (ABCP^DVE: 43 vs. 58 g/kg DM), lower in truly absorbed protein in the small intestine (DVE: 95 vs. 111 g/kg DM), and lower in degraded protein balance (OEB^DVE: −39 vs. −23 g/kg DM) than the hulless barley lines but greater (P < 0.01) in undigested inorganic matter (9 g/kg DM). From NRC Dairy 2001 model, CDC Fibar was greater (P < 0.05) in degraded protein balance (OEB^NRC: −30 g/kg DM) and metabolizable protein (MP: 118 g/kg DM) than the other hulless barley lines, while hulled barley was relatively lower (P < 0.01) in total metabolizable protein (MP: 83 vs. 105 g/kg DM). Our correlation results suggested that TDP was negatively correlated to amylose (r = −0.85, P < 0.001) but positively correlated to β-glucan level (r = 0.74, P < 0.001) in hulless barley cultivars. The DVE and OEB^DVE as well as MP were negatively correlated (P < 0.05) to amylose level but positively correlated to β-glucan level (P < 0.05). In conclusion, altered carbohydrate traits in the hulless barley varieties have the potential to increase intestinal nutrient availability to ruminants and significantly improved the truly absorbed protein supply to dairy cattle compared to hulled barley. Hulless barley with lower amylose and higher β-glucan level could provide greater (P < 0.05) truly digested protein in the small intestine, better synchronized available energy and N and increase metabolizable protein supply to ruminants.     

A review of the Namaqua gecko,Pachydactylus namaquensis (Reptilia: Gekkonidae) from southern Africa,with the description of two new species

An analysis of morphological and allozyme variation in the Namaqua gecko, Pachydactylus namaquensis from southern Africa is presented. Three separately evolving lineages, well defined by morphology and allozyme variation, are identified. The isolated southern population, occurring on the southern escarpment and Cape Fold Mountains surrounding the western Little Karoo, is named P. kladamderma sp. nov., and is characterized by a slit-like ear opening, low number of granules bordering the mental (3-6) and mental and adjacent infralabials (513), the frequent (79%) occurence of the supralabial entering the nostril, and its drab brown base colouration. A northern population, occurring in southern Namibia and the Richtersveld is named P. haackei sp. nov., and is characterized by its more rounded or squared ear opening; high number of granules bordering the mental and adjacent infralabials (11-19), the general exclusion of the supralabial from the nostril (only 3.7% entry), and brighter, lighter colouration. It is further differentiated from P. kladaroderma on the basis of fixed differences at 11 allozyme loci. Both new species differ from P. namaquensis, which is mainly restricted to Little Namaqua- land, but is sympatric with P. haackei in the Lower Orange River region, by their more heterogenous dorsal scalation, smaller cloacal spurs, lack of spine-like tubercles on the lateral surfaces of the tail, and more fragile skin. The type locality of P. namaquensis is restricted to ‘the vicinity of Springbok, Little Namaqualand, Northern Cape Province, South Africa’.     

Empirical estimation of dispersal resistance surfaces: a case study with red-cockaded woodpeckers

Persistence of wildlife populations depends on the degree to which landscape features facilitate animal movements between isolated habitat patches. Due to limited data availability, the effect of landscape features on animal dispersal is typically estimated using expert opinion. With sufficient data, however, resistance surfaces can be estimated empirically. After modeling suitable prospecting habitat using an extensive dataset from the federally endangered red-cockaded woodpecker (Picoides borealis), we used data from over 800 prospecting events from 34 radio-tagged birds to identify the best relationship between habitat suitability and resistance surfaces. Our results demonstrated that juvenile female P. borealis prospecting for new territories beyond their natal territories preferred to traverse through forests with tall canopy and minimal midstory vegetation. The non-linear relationship between habitat suitability and resistance surfaces was the most biologically relevant transformation, which in turn identified the specific forest composition that promoted and inhibited prospecting and dispersal behavior. These results corresponded with over 60 % of dispersal events from an independent dataset of short-distance dispersal events. This new understanding of P. borealis prospecting behavior will help to identify areas necessary for maintaining habitat connectivity and to implement effective management strategies. Our approach also provides a framework to not only estimate and evaluate resistance surfaces based on species-specific responses to intervening landscape features, but also addresses an often-neglected step, selecting a biologically relevant function to transform habitat suitability model into a resistance surface.