BUSCADOR RECOLECTA

When modelling the emergence of weeds, two main factors are considered that condition
this process: temperature and soil moisture. Optimum temperature is necessary for metabolic
processes that generate energy for growth, while turgor pressure is necessary for root
and shoot elongation which eventually leads to seedling emergence from the soil. Most
emergence models do not usually consider light as a residual factor, but it could have an
important role as it can alter directly or indirectly the dormancy and germination of seeds. In
this paper, inclusion of light as an additional factor to photoperiod and radiation in emergence
models is explored and compared with the classical hydrothermal time (HTT) model
using Camelina microcarpa as an example. HTT based on hourly estimates is also compared
with that based on daily estimates. Results suggest that, although HTT based models
are accurate enough for local applications, the precision of these models is improved when
HTT is estimated hourly and solar radiation is included as a factor., This work was supported by the Ministerio de Educación y Ciencia de España (AGL2010-
22084-C02-01). We thank the Botanical Garden of the University of Latvia for letting us set the
experiment in their court. We thank Núria Moix, Ana Isábal, Jordi Rey, Ana Baños and Eva
Edo for their help in the field. We also thank Joe Boots for his expert field assistance at the
Morris, Minnesota field site.

Nest densities of harvester ants (Messor barbarus) are high in rain-fed cereal fields in north-eastern Spain where the ants remove large quantities of seeds, contributing to reductions in weed populations. The distribution of harvester ant nests within a field can influence the effectiveness of ants as weed seed predators because areas with low ant nest density have lower weed seed removal rates. Tillage can disturb or even kill ant colonies and may be an important factor explaining the distribution of nests within fields. During the summers of 2011 - 2013, the number of nests in a 50 x 50 m area in 4 tilled and 3 no-till fields were counted. Tilled fields were disturbed twice a year, in November before cereal seeding and in July, after cereal harvest, whereas no-till fields had no soil disturbance. Ant nests were evenly spaced in no-till fields whereas nests were randomly distributed in tilled fields. Our results provide evidence that no-till in cereal fields promotes a more even distribution of M. barbarus nests, which should result in higher and more regular levels of weed seed predation across the field., We would like to thank Sergi Royan and Nuria Moix for their help in locating and counting ant nests for this study. We would also like to thank the farmers Xavier Llobet, Alejandro Pollino, Jaume Ros, and Fran X. Albareda for allowing us to asses nest density in their fields. This study was partially funded by projects AGL2010-22084 and AGL2007-60828 from the Spanish National R&D program, and the Department of Agriculture, Food and environment of the Catalan Government (DAAM) (2012 AGEC 00040 Ajuts a la producción agraria ecològica).

Germination and emergence are critical life stages for annual plants and so their full understanding is essential for managing arable plant populations. This study investigated the most important species-specific environmental cues that regulate seed germination and emergence (temperature and light) of the arable Ranunculaceae species Consolida orientalis, Consolida pubescens, Delphinium gracile, Delphinium halteratum ssp. verdunense and Nigella gallica, in order to propose management strategies for their preservation in agro-ecosystems. Growth chamber and outdoor pot experiments were conducted for two consecutive seasons to analyse light (complete darkness or 12 h light) and temperature (5/10, 5/15 and 10/20ºC) requirements and emergence patterns. The relative light germination requirement (ΔGlight), which extends from -100 (complete darkness) to 100 (light), was estimated. Weibull functions were fitted to observed emergence (%) in pots. For all species, germination was higher in complete darkness than with a light regime (-60 < ΔGlight < -95). This dark requirement indicates better germination for buried seeds. A tillage operation just after seed shed is therefore recommended. Consolida spp. germinate and emerge almost exclusively in autumn-winter, while Delphinium spp. and N. gallica can also germinate in spring. These arable plants would be able to adapt to delayed sowings, an important strategy for avoiding early-emerging competitive weeds. Facultative winter-germinating species could face early herbicide treatments if sufficient emergence occurs in winter-spring. These results bring new information to develop conservation strategies for these species in agro-ecosystems., This work was supported by the Ministerio de Educación y Ciencia de España (AGL2007-60828 and AGL2010-22084-C02-01). Special thanks to
Nuria Moix, Eva Edo and Laia Mateu for their help during the experimental work.

The interaction between the spatial distribution of weed richness and weed cover and the spatial location of harvester ant nets was investigated in cereal fields. The understanding of such interdependencies can be relevant to understand weed population dynamics in dryland cereal fields and may enhance management strategies for weed control. We used spatial statistical tools derived from point process theory. In particular, we compared the two spatial configurations by assuming two different point patterns. We did so by replacing the random weed fields by a related point pattern and comparing it with the point pattern of harvester ants. Our results suggest that areas with a high density of ant nests are, in this case study, in areas with low weed richness and that large nests have a greater impact than small nests. Considering that only one field was analysed, preserving and enhancing regular ant nest distributions, especially of large nests, might have an impact on depleting weeds and consequently enhancing weed control., We wish to thank the Ministry of Education and
Science of Spain (projects AGL 2007-60828 and AGL 2010-22084-C02-01) for the research funding

This research investigated the temperature and light requirements for seed germination and emergence patterns of pinnate poppy, violet horned-poppy, and nodding hypecoum, three annual Papaveraceae species found in arable lands in the Mediterranean region. Two experiments performed in growth chambers (1) analyzed light (complete darkness or 12 h light) and temperature (10/5, 15/5, and 20/10 C day/night temperatures) requirements for germination, and (2) determined base temperature (T-b) for germination. An outdoor pot trial was also set up to study emergence patterns. All species showed higher germination in complete darkness than they did with a light regime, irrespective of dormancy level, time of the year, and temperature regime under which germination was tested, illustrating better germination when seeds are buried. T-b ranged from -2.6 to 0 C, depending on the species, indicating low temperature requirements for germination. Given their higher germination in daily fluctuating, rather than constant temperatures, the three Papaveraceae species should have the capacity to form persistent seed banks. These species behaved as winter annuals (from November to February) in the pot experiment and had difficulties to emerge in spring. Given that they cannot avoid autumn-winter chemical treatments, this could partially explain their regression in arable fields. These results bring new information to develop management strategies for these Papaveraceae species in agroecosystems., Special thanks to Núria Moix, Ana Isábal, and Laia Mateu for their help during the experimental work. This work was supported by the Ministerio de Educación y Ciencia de España (AGL2007-60828 and AGL2010-22084-C02-01).

The adoption of conservation agriculture (CA) techniques by farmers is changing the dynamics of weed communities in cereal fields and so potentially their spatial distribution. These changes can challenge the use of site-specific weed control, which is based on the accurate location of weed patches for spraying. We studied the effect of two types of CA (direct drilling and harrow-tilled to 20 cm) on weed patches in a three-year survey in four direct-drilled and three harrow-tilled commercial fields in Catalonia (North-eastern Spain). The area of the ground covered by weeds (hereafter called “weed cover”) was estimated at 96 to 122 points measured in each year in each field, in 50 cm × 50 cm quadrats placed in a 10 m × 10 m grid in spring. Bromus diandrus, Lolium rigidum, and Papaver rhoeas were the main weed species. The weed cover and degree of aggregation for all species varied both between and within fields, regardless of the kind of tillage. Under both forms of soil management all three were aggregated in elongated patterns in the direction of traffic. Bromus was generally more aggregated than Lolium, and both were more aggregated than Papaver. Patches were stable over time for only two harrow-tilled fields with Lolium and one direct-drilled field with Bromus, but not in the other fields. Spatial stability of the weeds was more pronounced in the direction of traffic. Herbicide applications, crop rotation, and traffic seem to affect weed populations strongly within fields, regardless of the soil management. We conclude that site-specific herbicides can be applied to control these species because they are aggregated, although the patches would have to be identified afresh in each season., This research was funded by the Spanish National Program (project: AGL2010-22084-C02-0). A.E.M. was funded by the Institute Strategic Programme (ISP) grants, “Soils to Nutrition” (S2N) grant number BBS/E/C/000I0330, and the joint Natural Environment Research Council (NERC) and Biotechnology and Biological Sciences Research Council (BBSRC) ISP grant “Achieving Sustainable Agricultural Systems” (ASSIST) grant number BBS/E/C/000I0100, using facilities funded by the BBSRC.

Thlaspi arvense L is a common weed found in most temperate regions throughout the world that also shows excellent potential for domestication as an oilseed crop. The complexity of T. arvense seed dormancy presently makes it difficult to predict its emergence and manage it as an oilseed crop. Therefore, a better understanding of factors controlling seed dormancy will help develop strategies for managing its weediness and facilitate development of crop genotypes. T. arvense has semi-indeterminate growth and seeds developed at the base of the inflorescence (basal) generally mature sooner than those near the top (apical). However, little is known about the maternal influences on the level of dormancy and germination of basal and apical seeds. To study this, two T. arvense populations, one from Spain and another from USA, were both grown at field sites in Almenar, Spain and Morris, Minnesota, USA during the same growing season (autumn 2012-summer of 2013). Basal and apical seeds collected at maturity were analyzed for mass, total protein and carbon content, oil content, and fatty acid profiles. Under controlled environment conditions, seed germination was measured at 5, 8, 11, 14, 17, and 20 degrees C and germination rate estimated at 8 C. Seed position on the inflorescence did not affect germination consistently nor were there clear differences in seed attributes between positions. However, seeds of both populations produced at Almenar had lower germination and were consistently larger and contained higher oil and carbon content than seeds produced at Morris. Results indicate that environmental influences at each growth location played a larger role in influencing dormancy and germination of seeds produced than did the seed attributes measured or position of seeds on the inflorescence. Published by Elsevier B.V., The experiment carried out in Almenar, Spain was supported by the Spanish project AGL2010-22084-C02-01 and by a grant from the Sociedad Española de Malherbologia (SEMh) in 2013

The aim of the present work is to study possible differences in the germination behavior of apical and basal seeds (produced in the upper and lower fruits of the infruitescence), of two populations of field pennycress (Thlaspi arvense), both produced in a Mediterranean and a continental temperate climate. The results showed that among the three studied factors (population, seed type, production site), only the production site was relevant for the total germination, germinating those produced in Morris in a greater amount than those produced in Lleida. Germination models could be applied only to seeds produced at Morris (>10% germination), and despite the lack of differences in the total germination percentage, germination rates (speed—b parameter—and time to 50% germination—G50) differed between population and seed types—apical seeds from the Spanish population germinated faster (lower b parameter) than the rest, while apical seeds of both populations germinated faster than the corresponding basal seeds (lower G50). The results show, on the one hand, the importance of the seed production site if this species was considered as a commercial oilseed crop and, on the other hand, differences that will help seed selection for seed germination and establishment improvement of pennycress., This work was financed, in part, by the grant given to Eva Edo-Tena by the Spanish Weed Science Society (SEMh), as well as by the Spanish Ministry of Science and Innovation (MICIIN) AGL2010-22084-C02-01 Plan Nacional I+D+I (MICIIN).

The harvester ant Messor barbarus can be responsible for high weed seed losses in dryland cereals in Spain. Because weeds occur in patches, harvester ants have to be able to find and exploit patches. However, seed patches can differ in size and may, therefore, differ in the probability of being discovered and exploited. Here, 90 patches varying in size from 0.25 to 9 m2 were created in three 50 x 50 m subareas in a cereal field. Oat seeds were sown, as weed seed surrogates, in the patches at 2000 seeds m-2. After 24 h, those remaining were collected and the exploitation rate (the percentage of seeds removed per patch discovered by ants) was estimated. Harvester ant nests and the location of the seed patches were georeferenced and used to estimate distances between them. The patch encounter rate (the proportion of patches discovered by the ants) decreased slightly, but significantly, with decreasing patch size, though not the exploitation rate, which was lowest in the smallest patches (78-94%) and highest in the largest (99-100%). Seed patches that were not found or partially exploited were mostly located in subareas with a lower ant nest density or a longer distance away from the nearest nest than seed patches that were fully exploited. The results of this study indicate that the interaction between the spatial distribution of ant nests and the patchy distribution of seeds can create opportunities for seeds to be subjected to lower levels of predation., Valentina Atanackovic and Joel Torra contributed
equally to the work described in this paper and should be considered joint first authors. We wish to thank Barbara Baraibar, Nuria Moix and Jordi Recasens. We also thank Xavier Llobet for allowing us to use his cereal field and for his patience and hospitality. We wish to thank Universitat de Lleida for providing a PhD grant to V. Atanackovic, and Ministry of Education and Science of Spain for funding (projects AGL 2007-60828 and AGL 2010-22084-C02-01).

Bromus diandrus Roth is a common weed species that has increased in no-tillage dry-land cereal fields in NE Spain because of the limited control options. The fitness response of plants with different emergence times (ETs) and its influence on demography has huge implications in weed management. With this subject, three ETs (F1, F2 and F3) of B. diandrus were established through three crop-sowing dates (D1, Oct.; D2, Nov.; D3, Dec.) for each of the three years in a barley-wheat-wheat rotation. In barley, the herbicides applied were not specific for B. diandrus, whereas in wheat the specific herbicide mesosulfuron-methyl plus iodosulfuron-methyl-sodium was applied. Plant density after treatments and fitness characteristics were estimated for each weed ET. Weed density decreased for later ETs and fitness was density-dependent, showing significantly higher values when a non-specific herbicide was applied, except in number of caryopses per spikelet. The increasing fitness shown by plants with later ETs and the linear relationships of vegetative biomass vs reproductive biomass and fecundity were disrupted by the herbicide mesosulfuron-methyl plus iodosulfuron-methyl-sodium. Plants that had survived this herbicide when wheat was growing had lower values for all the characteristics analysed. After three seasons, as a consequence of decreasing seed recruitment, a practical depletion of the B. diandrus population was achieved in F2 and F3 (<2.8 and <1 plants/m2, respectively) but not in F1 (60.5 plants/m2). This study shows the importance of delayed crop sowing to optimize the control of B. diandrus in cereal fields with no tillage., This work was supported by the Ministerio de Educación y Ciencia de España (projects AGL2007-60828 and AGL2010-22084-C02-01) and by a PhD student grant from the Universitat de Lleida.

Questions: What is the role of managed fallow habitats in providing resources for pollination services in agricultural landscapes? How is resource provision affected by fallow management and landscape structure? Can the resulting variation in the value of fallows to pollinators be explained using the response-and-effect trait framework?
Location: Four semi-arid Mediterranean agricultural regions (NE Iberian Peninsula).
Methods: Landscape complexity, fallow field age and management practices were identified as the explanatory factors that interact which each other and affect the provision of resource for pollination communities. A trait-based approach was taken to model the system. Plant traits were selected on the basis of their response to abiotic factors (response traits) and those
that influence the interaction with pollinators (effect traits). Plant community characterization was calculated based on both taxonomic and functional indices. The linkages between the selected plant traits on contrasting fallows were analyzed using community-weighted mean Redundancy Analysis (CWM-RDA).
Results: The presence of semi-natural areas in the landscape was shown to enhance the value of fallows for pollinators, providing a source of diverse flower forms. In contrast, we found that field edges act as a relatively poor reservoir for flowering plant species in these areas. Land-use practices promoting mid-successional plant communities that support the coexistence of
diverse life forms with overlapping flowering periods and a range of flower morphologies had the greatest potential to support a diverse pollinator community.
Conclusions: An early-herbicide application (February) combined with shredding were identified as the best fallow-practices for enhancing resources for pollinators. The construction of our framework will help policy makers to identify management recommendations that will
result in the most beneficial plant communities for pollinators in fallows., Funding information
Ministerio de Economía y Competitividad, Grant/Award Number: AGL2010-
22084-C02-01 and EEBB-I-13-07228; NERC Environmental Bioinformatics Centre, Grant/Award Number: NE/N018125/1 LTS-M ASSIST

The food production and processing value chain is under pressure from all sides-increasing demand driven by a growing and more affluent population; dwindling resources caused by urbanization, land erosion, pollution and competing agriculture such as biofuels; and increasing constraints on production methods driven by consumers and regulators demanding higher quality, reduced chemical use, and most of all environmentally beneficial practices 'from farm to fork'. This pressure can only be addressed by developing efficient and sustainable agricultural practices that are harmonized throughout the value chain, so that renewable resources can be exploited without damaging the environment. Bridges must, therefore, be built between the diverse areas within the food production and processing value chain, including bridges between different stages of production, between currently unlinked agronomic practices, and between the different levels and areas of research to achieve joined-up thinking within the industry, so that the wider impact of different technologies, practices and materials on productivity and sustainability is understood at the local, regional, national and global scales. In this article, we consider the challenges at different stages and levels of the value chain and how new technologies and strategies could be used to build bridges and achieve more sustainable food/feed production in the future., Research at the University of Lleida is supported by MINECO, Spain (AGL2009-11006; AGL2009-11475; AGL2009-11964; AGL2009-13517-C03-02; AGL2010-21572; AGL-22050-C03-01; AGL2010-22084-CO2-O1; AGL2010-22182; AGL2011-23996; AGL2011-24862; AGL2011-30529-C02-02; AGL2012-35300; AGL2012-40144-C03-03; BIO2011-22525; BIO2011-23324; BIO2007-61413; CTQ2009-07831; CTM2009-14612 and PIM2010PKB-00746); EU FP7 Integrated Project 222716 SmartCell; EU FP7 European Research Council IDEAS Advanced Grant (to PC) Program-BIOFORCE; EU FP7 Large-scale integrated project KBBE 222738 Selection and improving of fit-for-purpose sampling procedures for specific foods and risks (BASELINE); EU FP7 Program-SICA project KBBE 222690; COST Action FA0804: Molecular farming: plants as a production platform for high value proteins; COST Action FA 1006: Plant Engine; COST Action TD1104: Development of electroporation-based technologies; Centre CONSOLIDER on Agrigenomics funded by MICINN, Spain; the HENUFOOD project (CEN-20101016) as part of the CENIT program and the INCOMES project as part of the INNPRONTA 2011.

Antiguamente el Bromus diandrus no era una especie problemática en
los cereales de invierno, estando su presencia restringida a los linderos
y ambientes ruderales. Sin embargo, la introducción de sistemas de
laboreo de conservación en algunas zonas, en especial la siembra
directa, ha comportado una mayor dificultad de control de ciertas
malas hierbas, entre ellas el bromo. En este artículo se sientan las
bases para un control integrado de esta mala hierba, basado en la
aplicación de herbicidas junto con la implantación de métodos
culturales, Los distintos resultados presentados en el presente artículo han formado parte de sendos proyectos de investigación financiados por el Plan Nacional I+D+i (AGL2007-60828 y AGL2010-22084-C02-01) y que ha llevado a cabo el grupo de Malherbología y Ecología Vegetal de la Universitat de Lleida

Knowledge on the emergence patterns of rare arable plants (RAP) is essential to design their conservation in Europe. This study hypothesizes that is possible to find functional groups with similar emergence patterns within RAP with the aim of establishing management strategies. Seeds of 30 different species were collected from Spanish arable fields and sown under two tillage treatments: (a) 1 cm depth without soil disturbance to simulate no-till, and (b) 1-10 cm depth with soil disturbance every autumn to simulate tillage to 10 cm depth. Two trials were established; the first trial being maintained for three seasons and the second for two seasons. Relative emergence in autumn, winter and spring was calculated each season. Afterwards, multivariate analysis was performed by K-means clustering and Principal Component Analysis to find groups of RAP species with similar emergence patterns. Four RAP groups were defined, and each was based on its main emergence season: autumn, winter, spring, or autumn-winter. Tillage treatment and the year of sowing had little effect on emergence patterns, which were mostly dependent on environmental factors, particularly temperature and rainfall. Therefore, conservation strategies could be designed for each of these RAP functional groups based on emergence patterns, rather than on a species-by-species basis., This research was funded by the Programa Estatal de Investigación, Desarrollo y Competitividad of the Ministerio de Indústria, Economía y Competitividad de España (AGL2007-60828 and AGL2010-22084-C02-01). Joel Torra acknowledges support from the Spanish Ministry of Science, Innovation and Universities (grant Ramon y Cajal RYC2018-023866-I).

The adoption of no-tillage systems in semi-arid cereal fields in northern Europe has resulted in difficulties in controlling Bromus diandrus. However, in some fields, lower densities are observed in continuous long-term no-tillage management than in other reduced tillage systems. A cumulative effect on the seedbank could promote changes in the period of seedling emergence and in population demography. This study evaluated the effect of long-term mouldboard plough (MbP), chisel plough (ChP), subsoiler (SS) and no-tillage (NT) on the population dynamics of B. diandrus. The work was carried out in a barley (Hordeum vulgare)-wheat (Triticum aestivum)-barley rotation during three seasons where these soil management systems had been applied for the last 22 years. Cumulative emergence (CE) and densities of B. diandrus followed a gradient of ChP > SS > NT > MbP. This cumulative effect over time resulted in significant differences in population demography. A previous hydrothermal emergence model developed for this species estimated the percentage of emergence prior to the date of sowing to be: 71%, 92% and 53% for the seasons 2008-2009, 2009-2010 and 2010-2011 respectively. Furthermore, the reduction in CE observed was on average 53% in SS, 92% in NT and 98% in MbP in comparison with that recorded in ChP. The long-term effect of different tillage systems tended to cause changes to soil characteristics (photo-inhibition of germination, soil temperature, water availability) affecting B. diandrus demography, reaching equilibrium in weed densities over years, which were significantly lower in MbP and NT than in ChP or SS, This work was supported by two projects of the Plan Nacional I +D + I of the Spanish Ministry of Science and Education (AGL2007-60828 and AGL2010-22084-C02-01), and the second author obtained a PhD grant from the Universitat de Lleida. Special thanks to Cristina Majan, Noemı Pacheco, Laura Rosell and Nuria Moix for their help during the data collection in the field and to Jaume Gregori and Carlos Cortes for their help in the field work.

Very little information is available on emergence of rare arable plants (RAP) in relation to soil disturbance and seed burial conditions in Europe. This information is essential to design conservation and soil management strategies to prevent the decline of these species in agroecosystems. The objective of this research was to investigate the effect of soil cultivation with burial time on the emergence and seed persistence of RAP. Seeds of 30 RAP species were collected from Spanish arable fields and subjected to two tillage treatments: (a) no soil disturbance, and (b) autumnal soil disturbance down to 10 cm depth every year. The treatments simulated no-till and tilled (disking), respectively. In plots under no-till, RAP seeds were sown at 1-cm depth. In the tilled plots, seeds were sown homogeneously mixed in the top 1-10 cm of soil. The trial was established every two consecutive seasons, and each trial was maintained for two years. Annual cumulative plant emergence was calculated each year; whereas the first trial was monitored for a third year to estimate seed longevity using a persistence index. The response in emergence of the 30 RAP to annual tillage varied among species. With burial time (number of years), higher emergence was observed for seeds sown in tilled soil. This was true across all species, and with strong season effects. The persistence index was correlated with seed weight, species with bigger seeds had low persistence indices while no pattern was observed for small seeded species. Most RAP species, particularly those with high persistence, showed induction of secondary dormancy processes, highlighting the importance of tillage to promote RAP emergence, and hence, seed bank replenishment. Therefore, as time passes the absence of soil tillage may represent a driver of RAP seed bank decline for those species with secondary dormancy processes. In conclusion, it is important to design soil management strategies, such as regular tillage to promote emergence, on a species basis to preserve RAP in Europe., Special thanks to Núria Moix, Eva Edo, Mariona Julià and Laia Mateu for their help during the experimental work. Special thanks to Frank Forcella for providing helpful comments on the manuscript. This work was supported by the Ministerio de Educación y Ciencia de España (AGL2007-60828 and AGL2010- 22084-C02-01).

Many weed species are becoming rare due to intense agricultural management, which leads to a decrease of biodiversity in agroecosystems. Cultivating some of these species for their oilseed content may help preserve them while profiting agronomically. Thlaspi arvense is one of these species with potential as an industrial crop. The aim of this work was to develop a model to describe the emergence of this species, and that can help to make decisions for its management, whether for conservation or production purposes. The emergence of two accessions of T. arvense, one from Spain and the other from USA, sown in Spain (Almenar) and USA (Morris), over two seasons (2011–12 and 2012–13) and in Riga (Latvia) over one season (2012), was followed to compare patterns and extent, as well as to develop emergence prediction models based on hydrothermal time (HTT) and photohydrothermal time (PhHTT). For the USA accession, the percentage of seeds that emerged was significantly higher than that of the Spanish accession. Both accessions presented two emergence peaks (autumn–winter and spring) in both localities, but while these peaks could be considered as two different flushes in Almenar – for both accessions –, they appeared to be a single flush disrupted by low winter temperatures in Morris. An HTT-based model was applicable for both accessions with less precision than the PhHTT-based one, which was more accurate in most cases but failed in certain circumstances for the USA accession. The differences in emergence percentage among accessions suggest that some accessions might be more amenable to being used as a crop. The two models developed in this work predicted the emergence of both accessions of T. arvense quite accurately. The inclusion of photoperiod in the hydrothermal time equation, creating a new unit that we have called photohydrothermal time, offers a possibility to obtain more accurate models., This work was supported by the Ministerio de Educación y Cienciade España (AGL2010-22084-C02-01). We thank the Botanical Garden of the University of Latvia for letting us set the experiment in their court. The group from Lleida thanks Núria Moix, Ana Isábal, Jordi Rey-Ana Baños and Eva Edo for their help in the field. We also thank Joe Boots for his expert field assistance at the Morris, Minnesota field site. Finally, we thank Dr Frank Forcella for his valuable suggestions to improve this manuscript.

The potential of fallow lands to favor farmland bird conservation is widely recognized. Since fallows provide key resources for birds within the agricultural matrix, such as nesting sites, shelter and forage, complete understanding of the effect of field-management strategies on vegetation structure and food is essential to fulfill bird requirements and improve habitat management. In this study we experimentally compare the most common field practices (ploughing, shredding, herbicide application and cover cropping) on fallow lands by assessing the resources they provide for birds in terms of vegetation structure and food resources (leaf and seed availability), as well as the economic costs of their implementation. Fallow management treatments are ranked for six target species in a lowland area of the north-eastern Iberian Peninsula, according to the available information on their requirements. The different agronomic practices offer various quantities and types of resources, highlighting the importance of fallow management in bird conservation. Shredding and early herbicide application (February) are estimated to be good practices for Little Bustard (Tetrax tetrax) and Calandra Lark (Melanocorypha calandra), providing both favorable habitat and foraging conditions, while being economical. Meanwhile, superficial tillage in spring is found to be optimum for the rest of the species tested, despite being among the poorest food providers. Alternating patches of the best treatments would improve the effectiveness of agri-environmental schemes by maximizing the harboring habitat for the endangered species., The present work has been financed by the Spanish National Program (proyect: AGL2010-22084-C02-01, BES-2011 047518). We gratefully acknowledge the field assistance of B. Bar- aibar, JA. Conesa, N. Moix, J Rey, A. Royo, X. Sole ́ -Senan and J. Torra. Thank are also due to J. Caus, P. Forns, J. Messegue and JM Montull for allowing us to use their fields and for their patience and hospitality. Field work permits were issued by the ‘Departament de Medi Ambient de la Generalitat de Catalunya’. We appreciate the comments of J. Traba to improve the final draft and S. Lade for the English correction. A pre- doctoral FPI scholarship was provided by the Spanish Ministry of Science and Education for I. Roblen ̃ o.