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European species-rich grasslands are threatened both by land use intensification as well as land abandonment. The studies shown in this thesis tested the possible use of ecological knowledge to ensure hay productivity whilst maintaining diversity of grasslands, with a view to informing ecological restoration. The overall approach was to understand interactions between plants, to study diversity effects on productivity, and mainly investigate how plant functional groups that arrive first in the system can create priority effects that influence community productivity both above- and belowground. A grassland field experiment was established and monitored for four years, in order to verify the effects of manipulating the order of arrival of different plant functional groups, as well as the sown diversity level on productivity and methane yield. The overall findings were: a) sowing legumes first created priority effects aboveground (higher biomass) and belowground (lower root length), plants invested less in roots and more in shoots, b) priority effects were more consistent below than aboveground, c) sown diversity did not affect aboveground biomass, d) the order of arrival treatments indirectly affected methane yield by affecting the relative dominance of plant functional groups. Since the researchers lack information on how legumes and non-legumes interact spatially belowground, (particularly related to root foraging) a controlled experiment was performed, using two grass species and one legume. The identity and location of the neighbours played a role in interactions, and the order plants arrived modulated it. When the focal species (grass) was growing with a legume it generally equated to the same outcome as not having a neighbour. Roots from the focal species grew more toward the legume than the grass neighbour, indicating a spatial component of facilitation. Since these studies involved root measurements, a method study was also conducted to verify how comparable and accurate are root length estimates obtained from different techniques. Results showed that the use of different methods can lead to different results, the studied methods did not have the same accuracy, and the automated methods can underestimate the root length. Overall, the results allow to conclude that different groups of plants arriving before others affected above and belowground biomass, roots may be key drivers during the creation of these priority effects, and interaction outcomes between plants depended on neighbour identity and location, modulated by the order they arrive in. The results suggest that priority effects can be used by sowing different species or plant functional groups at different time to steer a community to a desired trajectory depending on the restoration goal. However, there is a need to test contingency, potential, and long term impacts of such possible tools for restoration.
Economic theory suggests both positive and negative relationships between intra-firm wage inequality and productivity. This paper contributes to the growing empirical literature on this subject. We combine German employer-employee-data for the years 1995-2005 with inequality measures using the whole wage distribution of a firm and rely on dynamic panel-data estimators to control for unobserved heterogeneity, simultaneity problems and possible state dependence. Our results indicate a relative minor influence of intra-firm wage inequality on firm productivity. If anything, they provide some support for a view suggesting that some inequality may be beneficial, while too much leads to a detrimental effect on productivity.
Using unique recently released nationally representative high-quality longitudinal data at the plant level, this paper presents the first comprehensive evidence on the relationship between exports and productivity for Germany, a leading actor on the world market for manufactured goods. It applies and extends the now standard approach from the international literature to document that the positive productivity differential of exporters compared to non-exporters is statistically significant, and substantial, even when observed firm characteristics and unobserved firm specific effects are controlled for. For West German plants (but not for East German plants) some empirical evidence for self-selection of more productive firms into export markets is found. There is no evidence for the hypothesis that plants which start to export perform better in the three years after the start than their counterparts which do not start to sell their products on the world market. Results for West Germany support the hypothesis that the productivity differential between exporters and nonexporters is at least in part the result of a market driven selection process in which those export starters that have low productivity at starting time fail as a successful exporter in the years after the start, and only those that were more productive at starting time continue to export.
This paper contributes to the flourishing literature on exports and productivity by using a unique newly available panel of exporting establishments from the manufacturing sector of Germany from 1995 to 2004 to test three hypotheses derived from a theoretical model by Hopenhayn (Econometrica 1992): (H1) Firms that stop exporting in year t were in t-1 less productive than firms that continue to export in t. (H2) Firms that start to export in year t are less productive than firms that export both in year t-1 and in year t. (H3) Firms from a cohort of export starters that still export in the last year of the panel were more productive in the start year than firms from the same cohort that stopped to export in between. While results for West Germany support all three hypotheses, this is only the case for (H1) and (H2) in East Germany.
Using panel data from Spain Farinas and Ruano (IJIO 2005) test three hypotheses from a model by Hopenhayn (Econometrica 1992): (H1) Firms that exit in year t were in t-1 less productive than firms that continue to produce in t. (H2) Firms that enter in year t are less productive than incumbent firms in year t. (H3) Surviving firms from an entry cohort were more productive than non-surviving firms from this cohort in the start year. Results for Spain support all three hypotheses. This paper replicates the study using a unique newly available panel data sets for all manufacturing plants from Germany (1995 – 2002). Again, all three hypotheses are supported empirically.
Using unique recently released nationally representative high-quality data at the plant level, this paper presents the first comprehensive evidence on the relationship between productivity and size of the export market for Germany, a leading actor on the world market for manufactured goods. It documents that firms that export to countries inside the euro-zone are more productive than firms that sell their products in Germany only, but less productive than firms that export to countries outside the euro-zone, too. This is in line with the hypothesis that export markets outside the euro-zone have higher entry costs that can only by paid by more productive firms.
Empirische Befunde zeigen, dass exportierende niedersächsische Industriebetriebe produktiver als vergleichbare nicht exportierende Betriebe sind, wobei diese Unterschiede bereits vor dem Exportstart bestehen (also eine Selbstselektion der produktiveren Betriebe auf Exportmärkte stattfindet), während es für Lerneffekte im Zusammenhang mit Exportaktivitäten und daraus folgendem höherem Produktivitätswachstum in exportierenden Betrieben keine Evidenz gibt. Mit neu verfügbaren Paneldaten für deutsche Industriebetriebe und auf der Grundlage der Ergebnisse einer neuen international vergleichenden Studie zeigt dieser Beitrag, dass die Produktivitätsprämie in Niedersachsen so hoch wie im Durchschnitt für den Rest von Westdeutschland, aber höher als für Ostdeutschland ist. Niedersachsen nimmt im internationalen Vergleich damit einen Mittelplatz unter den hier betrachteten Ländern ein. Ein interregionaler bzw. internationaler Vergleich der Größenordnungen der Selektions- und Lerneffekte ist hier allerdings nicht möglich. Zwar zeigt eine Gegenüberstellung der Ergebnisse für Niedersachsen mit denen für das übrige West- bzw. für Ostdeutschland und mit den übrigen EU-Ländern in den meisten Fällen ein Bild ähnlich wie für Niedersachsen, aber die Gruppen der Starter umfassen dabei in der Regel nur wenige Firmen, und die geschätzten Koeffizienten sind sehr häufig statistisch insignifikant, so dass ein quantitativer Vergleich nicht möglich ist.
We use comparable micro level panel data for 14 countries and a set of identically specified empirical models to investigate the relationship between exports and productivity. Our overall results are in line with the big picture that is by now familiar from the literature: Exporters are more productive than non-exporters when observed and unobserved heterogeneity are controlled for, and these exporter productivity premia tend to increase with the share of exports in total sales; there is strong evidence in favour of self-selection of more productive firms into export markets, but nearly no evidence in favour of the learning-by-exporting hypothesis. We document that the exporter premia differ considerably across countries in identically specified empirical models. In a meta-analysis of our results we find that countries that are more open and have more effective government report higher productivity premia. However, the level of development per se does not appear to be an explanation for the observed cross-country differences.