University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Ecosystem function enhanced by combining four functional types of plant species in intensively managed grassland mixtures: a 3‐year continental‐scale field experiment

Abstract: 1.A coordinated continental-scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N2-fixing legume or nonfixing grass) crossed with temporal development (fast-establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site and sown at two levels of seed density. 2.Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best-performing monoculture of 1·07 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best-performing monoculture = 1·18). 3.Mixtures maintained a resistance to weed invasion over at least 3 years. In mixtures, median values indicate

Sources and mechanisms of priming effect induced in two grassland soils amended with slurry and sugar

Abstract: The mechanisms and specific sources of priming effects, ie short term changes of soil organic matter (SOM) decomposition after substance addition, are still not fully understood These uncertainties are partly method related, ie until now only two C sources in released CO2 could be identified We used a novel approach separating three carbon (C) sources in CO2 efflux from soil The approach is based on combination of different substances originated from C3 or C4 plants in different treatments and identical transformation of substances like C3 sugar (from sugar beet) and C4 sugar (from sugar cane) We investigated the influence of the addition of two substances having different microbial utilizability, ie slurry and sugar on the SOM or/and slurry decomposition in two grassland soils with different levels of Corg (23 vs 51% C) Application of slurry to the soil slightly accelerated the SOM decomposition Addition of sugar lead to changes of SOM and slurry decomposition clearly characterized by two phases: immediately after sugar addition, the microorganisms switched from the decomposition of hardly utilizable SOM to the decomposition of easily utilizable sugar This first phase was very short (2‐3 days), hence was frequently missed in other experiments The second phase showed a slightly increased slurry and SOM decomposition (compared to the soil without sugar) The separation of three sources in CO2 efflux from grassland soils allowed us to conclude that the C will be utilized according to its utilizability: sugarOslurryOSOM Additionally, decomposition of more inert C (here SOM) during the period of intensive sugar decomposition was strongly reduced (negative priming effect) We conclude that, priming effects involve a chain of mechanisms: (i) preferential substrate utilization, (ii) activation of microbial biomass by easily utilizable substrate (iii) subsequent increased utilization of following substrates according to their utilizability, and (iv) decline to initial state q 2005 Elsevier Ltd All rights reserved

The degradability characteristics of fifty-four roughages and roughage neutral-detergent fibres as described by in vitro gas production and their relationship to voluntary feed intake

Abstract: Fifty-four roughages of known voluntary dry-matter intakes (DMI; range 7.8-35.2 g/kg live weight per d) were examined in vitro in a gas production test. Samples (200 mg) of roughage and roughage neutral-detergent fibre (NDF) respectively were incubated in a mixed suspension of rumen contents for 96 h and the gas volumes recorded after 4, 6, 8, 12, 24, 30, 36, 48, 54, 60 and 96 h. The kinetics of gas production were derived from the volume recordings described by the exponential equation Y = A + B(l-e-ct) where A is the intercept and ideally reflects the fermentation of the soluble and readily available fraction of the feed, B describes the fermentation of the insoluble (but with time fermentable) fraction and c the fractional rate at which B is fermented per h; A + B describes total fermentation. In vitro true dry matter (TD) and NDF degradabilities (NDF-D) after 24 h incubation were also determined. Of the variation in DMI, 75% was accounted for by the in vitro gas production parameters A, B and c in stepwise multiple regressions; 82% of the variation in DMI was explained by the parameters (ANDF + BNDF) and cNDF as obtained from the incubation of roughage NDF. The rate constants (c) were less important than parameters related to the extent of gas production, accounting for only 6.5 (whole roughage) and 4.1% (NDF) of the variation in DMI. There was no statistical advantage in the use of the exponential model describing extent and rate of fermentation over some of the simple gas volume measurements: 75% of the variation in DMI was accounted for by in vitro gas production of whole roughage after 8 h of incubation. On average gas production from NDF measured from 24-96 h accounted for 81% of the variation in DMI. A combination of gas volume measurements after a short period of incubation (4-8 h) with a concomitant determination of NDF-D after many hours (> or = 24 h) can render NDF preparations and long incubation times redundant. A method is suggested to obtain two results for DMI prediction in one single incubation. Of the variation in DMI 80% was accounted for by the incubation of 500 mg whole roughage when incubation was terminated after 24 h and the residual undegraded substrate quantified.

Exploration and Exploitation Strategies, Profit Performance, and the Mediating Role of Strategic Learning: Escaping the Exploitation Trap

Abstract: This study focuses on the role of strategic learning as a mediating construct between opportunity-seeking (exploration) and advantage-seeking (exploitation) strategies and profit performance. Prior studies argue that the effect of these core elements of strategic entrepreneurship (exploration and exploitation) cannot be fully captured through their direct effects on profit performance, but that this relationship consists of mediating factors. This study proposes that the process of strategic learning, through its intraorganizational elements that enable the dissemination, interpretation, and implementation of strategic knowledge, enables firms to capitalize on the benefits of both exploration and exploitation strategies. Results from 206 Finnish software firms indicate that strategic learning fully mediates the relationship between exploration, exploitation, and profit performance. The result contributes by stressing the importance of strategic learning processes, especially in conjunction with entrepreneurial exploration strategies. Furthermore, the study demonstrates that the effect from exploration to strategic learning is moderated by the level of exploitation. This moderation effect suggests that the strategic learning is limited, being a path dependent capability that favors exploitation over exploration when stretched. However, strategic learning effectively allows both types of strategies to improve profit performance.

Social media’s enduring effect on adolescent life satisfaction

Abstract: In this study, we used large-scale representative panel data to disentangle the between-person and within-person relations linking adolescent social media use and well-being. We found that social media use is not, in and of itself, a strong predictor of life satisfaction across the adolescent population. Instead, social media effects are nuanced, small at best, reciprocal over time, gender specific, and contingent on analytic methods.