Predicting breeding bird occurrence by stand- and microhabitat-scale features in even-aged stands in the Central Appalachians

Spatial scale is an important consideration when managing forest wildlife habitat, and models can be used to improve our understanding of these habitats at relevant scales. Our objectives were to determine whether stand- or microhabitat-scale variables better predicted bird metrics (diversity, species presence, and abundance) and to examine breeding bird response to clearcut size and age in a highly forested landscape. In 2004-2007, vegetation data were collected from 62 even-aged stands that were 3.6-34.6 ha in size and harvested in 1963-1990 on the Monongahela National Forest, WV, USA. In 2005-2007, we also surveyed birds at vegetation plots. We used classification and regression trees to model breeding bird habitat use with a suite of stand and microhabitat variables. Among stand variables, elevation, stand age, and stand size were most commonly retained as important variables in guild and species models. Among microhabitat variables, medium-sized tree density and tree species diversity most commonly predicted bird presence or abundance. Early successional and generalist bird presence, abundance, and diversity were better predicted by microhabitat variables than stand variables. Thus, more intensive field sampling may be required to predict habitat use for these species, and management may be needed at a finer scale. Conversely, stand-level variables had greater utility in predicting late-successional species occurrence and abundance; thus management decisions and modeling at this scale may be suitable in areas with a uniform landscape, such as our study area. Our study suggests that late-successional breeding bird diversity can be maximized long-term by including harvests >10 ha in size into our study area and by increasing tree diversity. Some harvesting will need to be incorporated regularly, because after 15 years, the study stands did not provide habitat for most early successional breeding specialists.     

Independently evolved virulence effectors converge onto hubs in a plant immune system network

Plants generate effective responses to infection by recognizing both conserved and variable pathogen-encoded molecules. Pathogens deploy virulence effector proteins into host cells, where they interact physically with host proteins to modulate defense. We generated an interaction network of plant-pathogen effectors from two pathogens spanning the eukaryote-eubacteria divergence, three classes of Arabidopsis immune system proteins, and ~8000 other Arabidopsis proteins. We noted convergence of effectors onto highly interconnected host proteins and indirect, rather than direct, connections between effectors and plant immune receptors. We demonstrated plant immune system functions for 15 of 17 tested host proteins that interact with effectors from both pathogens. Thus, pathogens from different kingdoms deploy independently evolved virulence proteins that interact with a limited set of highly connected cellular hubs to facilitate their diverse life-cycle strategies.     

Isolation of culturable phosphobacteria with both phytate-mineralization and phosphate-solubilization activity from the rhizosphere of plants grown in a volcanic soil

Chilean volcanic soils contain large amounts of total and organic phosphorus, but P availability is low. Phosphobacteria [phytate-mineralizing bacteria (PMB) and phosphate-solubilizing bacteria (PSB)] were isolated from the rhizosphere of perennial ryegrass (Lolium perenne), white clover (Trifolium repens), wheat (Triticum aestivum), oat (Avena sativa), and yellow lupin (Lupinus luteus) growing in volcanic soil. Six phosphobacteria were selected, based on their capacity to utilize both Na-phytate and Ca-phosphate on agar media (denoted as PMPSB), and characterized. The capacity of selected PMPSB to release inorganic P (Pi) from Na-phytate in broth was also assayed. The results showed that from 300 colonies randomly chosen on Luria–Bertani agar, phosphobacteria represented from 44% to 54% in perennial ryegrass, white clover, oat, and wheat rhizospheres. In contrast, phosphobacteria represented only 17% of colonies chosen from yellow lupin rhizosphere. This study also revealed that pasture plants (perennial ryegrass and white clover) have predominantly PMB in their rhizosphere, whereas PSB dominated in the rhizosphere of crops (oat and wheat). Selected PMPSB were genetically characterized as Pseudomonas, Enterobacter, and Pantoea; all showed the production of phosphoric hydrolases (alkaline phosphatase, acid phosphatase, and naphthol phosphohydrolase). Assays with PMPSB resulted in a higher Pi liberation compared with uninoculated controls and revealed also that the addition of glucose influenced the Pi-liberation capacity of some of the PMPSB assayed.     

Solvent-free lipase-catalyzed preparation of long-chain alkyl phenylpropanoates and phenylpropyl alkanoates

An enzymatic method was developed for the preparation of medium- or long-chain alkyl 3-phenylpropenoates (alkyl cinnamates), particularly alkyl hydroxy- and methoxy-substituted cinnamates such as oleyl p-coumarate and oleyl ferulate. The various alkyl cinnamates were formed in high to moderate yield by lipase-catalyzed esterification of cinnamic acid and its analogues with fatty alcohols in vacuo at moderate temperatures in the absence of drying agents and solvents. Immobilized Candida antarctica lipase B was the most effective biocatalyst for the various esterification reactions. The relative esterification activities were of the following order: dihydrocinnamic > cinnamic > 3-methoxycinnamic > dihydrocaffeic approximately 3-hydroxycinnamic > 4-methoxycinnamic > 2-methoxycinnamic > 4-hydroxycinnamic > ferulic approximately 3,4-dimethoxycinnamic > 2-hydroxycinnamic acid. With respect to the position of the substituents at the phenyl moiety, the esterification activity increased in the order meta > para > ortho. Rhizomucor miehei lipase demonstrated moderate esterification activity. Compounds with inverse chemical structure, that is, 3-phenylpropyl alkanoates such as 3-(4-hydroxyphenyl)propyl oleate, were also obtained in high yield by esterification of fatty acids with the corresponding 3-phenylpropan-1-ols.     

Prior exposure to diurnal heating influences soil respiration and N availability upon rewetting

On sunny summer days, the top 10 cm of soil in southern Australia are heated to temperatures between 50 and 80 °C for a few hours a day, often for several successive days. These extreme temperature events are likely to have profound effects on the microbiota in these soils, but we do not know how this recurrent heat exposure influences microbial dynamics and associated nutrient cycling. In this study, an air-dry soil from southern Australia was exposed to one or two diurnal heating events with maximum temperature of 50 or 70 °C. The control was left at ambient temperature (Amb). All soils were rapidly rewet. Soil respiration was measured for 7 days after rewetting; microbial biomass C, available N and P were determined before rewetting and 1 and 7 days after rewetting. After heating and before rewetting compared to Amb, microbial biomass C (MBC) was 50–80% lower, but available P was 25% higher in heated soils. Available N differed little between Amb and heated soils. Rewetting resulted in a flush of respiration in Amb and soils heated once, but there was no respiration flush in soils heated twice. Cumulative respiration compared to Amb was about 10% higher in soils heated once and about 25% lower in soils heated twice. In Amb, MBC 1 day after rewetting was similar as before rewetting. But in heated soils, MBC increased from before rewetting to 1 day after rewetting about fourfold. Compared to Amb, available N 1 day after rewetting was 20–30% higher in soils heated to 70 °C. Seven days after rewetting, available N was 10% higher than Amb only in soils heated twice to 70 °C. It can be concluded that diurnal heating kills a large proportion of the microbial biomass and influences soil respiration and nutrient availability after rewetting of soils. The effect of heating depends on both maximum temperature and number of events.     

盐分对土壤呼吸和有机质动力学的影响与土壤电导率相关，而与渗透势的关系更为密切

Osmotic potential (OP) of soil solution may be a more appropriate parameter than electrical conductivity (EC) to evaluate the effect of salts on plant growth and soil biomass.However,this has not been examined in detail with respect to microbial activity and dissolved organic matter in soils with different texture.This study evaluated the effect of salinity and sodicity on respiration and dissolved organic matter dynamics in salt-affected soils with different texture.Four non-saline and non-sodic soils differing in texture (S-4,S-13,S-24 and S-40 with 4％,13％,24％ and 40％ clay,respectively) were leached using combinations of 1 mol L-1 NaC1 and 1 mol L-1 CaC12 stock solutions,resulting in EC (1:5 soil:water ratio) between 0.4 and 5.0 dS m-1 with two levels of sodicity (sodium absorption ratio (SAR) ＜ 3 (non-sodic) and 20 (sodic),1:5 soil:water ratio).Adjusting the water content to levels optimal for microbial activity,which differed among the soils,resulted in four ranges of OP in all the soils:from-0.06 to--0.24 (controls,without salt added),-0.55 to-0.92,-1.25 to-1.62 and-2.77 to-3.00 Mpa.Finely ground mature wheat straw (20 g kg-1) was added to stimulate microbial activity.At a given EC,cumulative soil respiration was lower in the lighter-textured soils (S-4 and S-13) than in the heavier-textured soils (S-24 and S-40).Cumulative soil respiration decreased with decreasing OP to a similar extent in all the soils,with a greater decrease on Day 40 than on Day 10.Cumulative soil respiration was greater at SAR =20 than at SAR ＜ 3 only at the OP levels between-0.62 and-1.62 MPa on Day 40.In all the soils and at both sampling times,concentrations of dissolved organic C and N were higher at the lowest OP levels (from-2.74 to-3.0 MPa) than in the controls (from-0.06 to-0.24 MPa).Thus,OP is a better parameter than EC to evaluate the effect of salinity on dissolved organic matter and microbial activity in different textured soils.     

Carbon storage in loess derived surface soils from Central Germany: Influence of mineral phase variables

The influence of the soil mineral phase on organic matter storage was studied in loess derived surface soils of Central Germany. The seven soils were developed to different genetic stages. The carbon content of the bulk soils ranged from 8.7 to 19.7 g kg^—1. Clay mineralogy was confirmed to be constant, with illite contents > 80 %. Both, specific surface area (SSA, BET‐N₂‐method) and cation exchange capacity (CEC) of bulk soils after carbon removal were better predictors of carbon content than clay content or dithionite‐extractable iron. SSA explained 55 % and CEC 54 % of the variation in carbon content. The carbon loadings of the soils were between 0.57 and 1.06 mg C m^—2, and therefore in the ”︁monolayer equivalent” (ME) level. The increase in SSA after carbon removal (ΔSSA) was significantly and positively related to carbon content (r² = 0.77). Together with CEC of carbon‐free samples, ΔSSA explained 90 % of the variation in carbon content. Clay (< 2 μm) and fine silt fractions (2—6.3 μm) contained 68—82 % of the bulk soil organic carbon. A significantly positive relationship between carbon content in the clay fraction and in the bulk soil was observed (r² = 0.95). The carbon pools of the clay and fine silt fractions were characterized by differences in C/N ratio, δ¹³C ratio, and enrichment factors for carbon and nitrogen. Organic matter in clay fractions seems to be more altered by microbes than organic matter in fine silt fractions. The results imply that organic matter accumulates in the fractions of smallest size and highest surface area, apparently intimately associated with the mineral phase. The amount of cations adhering to the mineral surface and the size of a certain and specific part of the surface area (ΔSSA) are the mineral phase properties which affect the content of the organic carbon in loess derived arable surface soils in Central Germany most. There is no monolayer of organic matter on the soil surfaces even if carbon loadings are in the ME level.     

Impact of short‐rotation coppice with poplar and willow on soil physical properties

As the land area of short‐rotation coppice (SRC) increases, their soil physical impacts have to be evaluated. The objective of this study was to detect the effects of long‐term SRC with poplar and willow on the vertical distribution of soil physical properties (bulk density, water retention, penetration resistance) and on solute transport patterns. An 18‐year‐old SRC located in northeastern Germany was compared to an adjacent continuous arable cropping system by means of soil sampling, penetrologger measurements and dye tracer experiments. The topsoil's bulk density was significantly lower under SRC than under cropland. This effect was especially pronounced in the uppermost 10 cm, where also the air capacity and the plant‐available water content were higher under SRC. The penetration resistance in 25–50 cm depth was reduced under SRC compared to the cropland, indicating a loosening of the plough pan. Dye tracer experiments showed that the importance of preferential flow was higher under SRC due to tree root channels and an increasing colonisation with invertebrates. SRC has ecologically advantageous effects on soil physical properties of the topsoil, however, combined with an enhanced risk of preferential solute transport upon application of agrochemicals.