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Differential thermal analysis (DTA) is a technique commonly used to evaluate the cold hardiness of plant organs that supercool as a means for cold survival. The aim of this study was to evaluate the effect of different pretest bud storage conditions, cooling rates, and bud excision techniques on dormant sweet cherry flower bud low temperature exotherms (LTEs) measured using DTA. Furthermore, this study compared cold hardiness estimates made using DTA and controlled freezing tests. We determined that buds stored at warmer temperatures (12.5 °C and room temperature) for 2–6 h prior to DTA or transported to the lab in a moist environment underwent biologically relevant changes in their apparent sensitivity to cold, as indicated by LTEs produced at warmer temperatures. The DTA cooling rate also significantly affected LTEs, with faster cooling resulting in the production of LTEs at warmer temperatures. Overall, LTEs were comparable among buds with varying amounts of plant material remaining attached to the bud base. It is important to note that the region directly subtending the primordia was always left intact on the buds being compared. This study demonstrated that overall, DTA and controlled freezing tests resulted in comparable measures of cold hardiness. The findings presented in this study are pertinent to researchers interested in conducting cold hardiness measurements in sweet cherry and highlight that consistency in DTA pretest conditions and bud preparation are required to achieve reliable LTE results that can be compared among studies. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilization and irrigation are critical for tree fruit and grape production in semi-arid regions of Western North America. Growers are increasingly considering more conservative fertilization and irrigation practices in order to optimize fruit quality while minimizing environmental impacts. The implications for pest populations of such shifts in production practices are not well known and warrant consideration. The objective of this research was to determine the effects of drip irrigation frequency (daily vs approximately every third day) and N fertilizer rate (ranging from 0 to 64 kg N/ha/year) on population densities of the ring nematode, Mesocriconema xenoplax, in a vineyard. The experiment was a split-plot randomized complete block design with irrigation frequency applied as whole-plot treatments and N input applied as subplot treatments. Nematode populations in root zone soils were assessed in spring, summer and fall of 2010 and 2011. There was a significant irrigation frequency × N input interaction, with M. xenoplax population densities increasing with N input under daily irrigation but not under low frequency irrigation. The data suggest that reductions in fertilizer N input and irrigation frequency, that have minimal impacts on fruit quality and yield, can also minimize M. xenoplax population buildup.

Concerns about climate change and the desire to develop a domestic, renewable energy source are increasing the interest in forest biomass extraction, especially in the form of logging residues, i.e., tree tops and branches. We reviewed the literature to determine the site and soil conditions under which removal of logging residues along with the stem (i.e., whole-tree harvesting), especially at clearcut, results in negative impacts on soil productivity compared with conventional stem-only harvesting in boreal and temperate forests. Negative impacts of biomass harvesting on soil nutrient pools (e.g., nitrogen, phosphorus and base cations) and soil acid-base status are more frequent in the forest floor than in the mineral soil. In the first years post-harvest, however, biomass harvesting has the greatest potential to influence tree survival and growth, either positively or negatively, through its effects on microclimate and competing vegetation. Later in the rotation, impaired nitrogen and (or) phosphorus nutrition on whole-tree harvested sites has been shown to reduce tree growth for at least 20 years in some stands. Biomass removal can also reduce the concentrations of base cations in soils and foliage, but this has not, to date, been shown to affect tree productivity. There are no consistent, unequivocal and universal effects of forest biomass harvesting on soil productivity. However, climate and microclimate, mineral soil texture and organic C content, the capacity of the soil to provide base cations and phosphorus, and tree species autecology appear to be critical determinants of site sensitivity to biomass harvesting. Rigorous, long-term experiments that follow stand development through a rotation will facilitate the identification of categories of site or stand conditions under which negative impacts of biomass harvesting are likely. Key words: forest biomass, whole-tree harvesting, soil productivity, tree nutrition, stand productivity. Les preoccupations au sujet des changements climatiques et la volonte de developper des sources d'energie domestique renouvelable augmentent l'interet pour l'extraction de la biomasse forestiere, surtout sous la forme de residus de coupe, c.-a-d., les cimes et les branches des arbres. Les auteurs ont conduit une revue de litterature pour determiner les conditions de site et de sol pour lesquelles l'enlevement des residus de coupe en plus de la tige (c.-a-d., la coupe par arbre entier ), surtout lors de coupes a blanc, conduit a des impacts negatifs sur la productivite des sols comparativement a la recolte conventionnelle du tronc seulement, en forets boreales et temperees. Les impacts negatifs de la recolte de la biomasse sur les reserves du sol en nutriments (p. ex. azote, phosphore et cations basiques) et sur le statut acidite-alcalinite apparaissent plus frequents dans l'humus que dans le sol mineral. Cependant, au cours des premieres annees suivant la recolte, le prelevement de la biomasse montre le plus fort potentiel pour influencer la survie des arbres et leur croissance, soit positivement soit negativement, par ses effets sur le microclimat et la vegetation competitrice. Plus tard dans la revolution, on observe que pour certains peuplements, une nutrition amoindrie en azote et (ou) phosphore sur les sites avec coupe par arbre entier reduit la croissance des arbres pendant au moins 20 ans. Le prelevement de la biomasse peut egalement reduire les teneurs en cations basiques dans les sols et le feuillage, mais ceci ne semble pas se traduire en effet sur la productivite. Il n'y a pas d'effets non equivoques et universels de la recolte de la biomasse sur la productivite des sols. Cependant, le climat et le microclimat, la granulometrie du sol, sa teneur en C organique, sa capacite a fournir les cations basiques et le phosphore, ainsi que l'autecologie des especes semblent constituer des determinants importants de la sensibilite des sites a la recolte de la biomasse. Des experiences rigoureuses, conduites a long terme pour suivre le developpement des peuplements tout au long de la revolution, faciliteront l'identification des categories de sites ou les conditions des peuplements pour lesquels des impacts negatifs sont susceptibles de se developper. [Traduit par la Redaction], Introduction Biomass from forests and byproducts from the manufacturing of traditional forest products are increasingly used to generate a range of bioproducts, of which bioenergy is currently the most common. [...]