A database of weed plants in the European part of Russia

Abstract Background Weeds are plants that, although not specially cultivated, grow and often adapt to growing in arable lands. They form an ecological variant of flora, as a historically-formed set of species growing on cultivated soils. For the rational use of the chemical and biological crop protection products and to produce safe and high-quality food, up-to-date data on the floristic diversity of weeds and the patterns of its geographical change are required. The need for a weeds' database arises that allows many specialists to work together independently. However, the great value of any database lies not in its existence, but in the accumulation of data that can be used to analyse the factors affecting the species diversity of weeds. New information A dataset of weed species diversity and their distribution in the European part of Russia, based on the results of the authors' own research from 1999 to 2019, has been created. The dataset includes 24,284 observations of occurrences of weed plants, which were obtained on the basis of 2,049 relevés of segetal plant communities in seven regions of the European part of Russia. In total, the dataset includes information about 329 species of vascular plants growing in 65 farmlands: cereals, spring and winter crops, industrial crops, row crops and perennial grasses (Tretyakova et al. 2020).


Introduction
Weeds are plants that, although not specially cultivated, are adapted to growing in arable lands (Ulyanova 2005, Luneva 2018. Typically, weeds are considered to be an undesirable element in crop agriculture. Their negative impact on crop development can be described in terms of competition for resources, reduction in productivity, increased challenges during harvesting and an overall increase in the cost of agricultural production. According to contemporary agricultural practice, the main task is not to completely eliminate weed plants, but rather to limit their appearance, mitigate their harmful effect and maintain them at a level that does not adversely affect the productivity of cultivated plants. In this regard, approaches to weed management are changing. Emerging approaches include descriptions of weeds as a special ecological group of plants growing on arable land (Altieri and Liebman 1988, Ulyanova 1998, Liebman et al. 2001. In recent decades, some weed species have been identified as being under threat indicating a need for their conservation (Hofmeister 1992, Eggers and Zwerger 1998, Holub and Procházka 2000, Meyer et al. 2010).
An important principle of organic farming involves the limited and rational use of herbicides. This creates a need to search for additional crop management strategies for controlling weeds (Harker et al. 2005, Harker andO'Donovan 2013). The "ecological weed management" approach (Altieri andLiebman 1988, Heard et al. 2003), which may be the most sustainable form of weed control in the long term (Walsh andPowles 2014, Zelaya andOwen 2017), suggests a tolerance for low weed infestation. The basis for the development of new ecological strategies for weed control is the availability of complete data on the biological diversity and distribution of weeds in particular areas.
The systematic study of weeds in Russia should be attributed to the beginning of the 20th century by the works of A. I. Maltsev (Maltsev 1962). In 1934, the Academy of Sciences of the USSR published a summary "Weeds of the USSR" (Keller 1934), which contains detailed botanical descriptions of 1326 species of weeds and information on their biology and distribution. To date, a large amount of research has been carried out on the weed plants species composition in the north-west and the central part of Russia (Palkina 2011, Palkina 2015, Luneva et al. 2017, in Siberia and the Russian Far East (Ulyanova 1985, Ulyanova 2005, Terekhina 2000 in the Cis-Urals and the Urals (Tuganayev 1984, Mirkin et al. 1985, Sleptsova and Rudakov 1985, Tuganayev and Semenova 1993,Tret'yakova 2006,Khasanova et al. 2014, Tuganayev et al. 2015, Khasanova et al. 2016, Kondratkov and Tretyakova 2018, Tretyakova and Kondratkov 2018, Kondratkov and Tretyakova 2019. In this paper, we present a dataset on the current diversity and distribution of weed plants in the European part of Russia. In total, the dataset contains 329 species of vascular plants growing in farmlands of 65 crops: cereals, spring and winter crops, industrial crops, row crops and perennial grasses. The dataset is expected to make a contribution to a deeper understanding of how biogeographic gradients of natural and anthropogenic factors determine the diversity of weed communities.

General description
Purpose: This paper aims to present the dataset on weed plants in the European part of Russia recently published in GBIF as a Darwin Core Archive.
Populating the database on the biological diversity of weeds in the European part of Russia. The need for this is caused by significant changes taking place in Russian agriculture due to the replacement of collective and state farms by production cooperatives, agricultural holdings and large agro-industrial enterprises. During this time, wide-reaching changes also took place in terms of agricultural practices, farm areas and the range of cultivated crops. Thus, it became necessary to update the data on the weed species composition and distribution. In this work, we integrate data from weed research specialists operating in seven regions of Russia from 1999 to 2019.

2.
Providing detailed information on the distribution of weeds in the regions of Russia and the occurrence of different types of arable lands. We suggest the dataset will give the scientific community an opportunity to reveal the driving factors that affect the diversity of weeds communities and to elicit its latitudinal and longitudinal variations, as well as the relationship between the weed species composition and cultivated crops. This is of key importance for the ability to predict the spread of weeds under different scenarios of climate change in different natural zones and will serve as a basis for comparison with data collected in the future.

Study area description:
The studied areas are located in the northwest of Russia (Leningrad, Novgorod, Pskov and Vologda oblasts), in the Cis-Ural region and in the Urals (the Udmurt Republic, the Republic of Bashkortostan and Sverdlovsk oblast). The latitudinal gradient covers the taiga, forest-steppe and steppe natural zones.

Design description:
The study of the composition of weed species was carried out by the method of route counts, which evenly covered the entire territory of the regions. During the survey, a series of weed community relevés were identified and accurately georeferenced using GPS. The investigated farmlands were used to cultivate 65 crop species, including grain spring and winter crops, industrial crops, row crops and perennial grasses.

Sampling description:
The study of weed plants communities of industrial, row crops and perennial grasses began with the stage of stemming and branching; for grain crops, it began with the stage of tilling and ended before harvesting. For perennial grasses, the 1st year planting was examined. For biennial row-crop and winter crops, both 1st and 2nd year plantings were examined. Neither the peculiarities of agrotechnical methods, nor the use of fertilisers, were taken into account. Weeds referred to any plants occurring in crops that did not serve the crop purpose, including other cultivated plants. Weeds of all ages were taken into account (seedlings, juvenile, immature, generative, excluding seeds), in any phenological (vegetation, budding, flowering, fruiting) or vital state (normally developed and depressed). In the Udmurt Republic, the weed survey was carried out by counting routes, during which floristic descriptions were provided. In the other six regions, the survey was carried out in 10×10 m plots, with at least three replicates. The distance between the plots was at least 500 m. The scientific names of plants were adjusted in accordance with the International Plants Names Index (http://www.ipni.org).
Quality control: Materials were collected and treated by the specialists in the All-Russian Institute of Plant Protection, Komarov Botanical Garden, South-Ural Botanical Garden Institute, Bashkir Scientific Research Institute of Agriculture, Botanical Garden of the Ural Branch of RAS and the Ural Federal University.
In order to publish our dataset on the GBIF network, we adjusted our records to the Darwin Core specifications (Wieczorek et al. 2012).
Georeferencing was carried out using GPS with WGS84 datum. Coordinate uncertainty for all occurrences was 100 metres.

Geographic coverage
Description: The studies were carried out in the southeast and northwest of the European part of Russia (EPR). The studied areas are distinguished by a variety of environmental conditions primarily in terms of heat provision, water availability and range of cultivated crop types. Within the areas, sharp biogeographic gradients of natural and anthropogenic factors are traced ( Table 2).  In the northwest, the oblasts of Leningrad, Pskov, Novgorod and Vologda oblasts are located. This territory lies within the East European Plain. The relief is mostly characterised by low-hills. The duration of the growing season varies from 160-170 days in the south to 110-120 days in the north. The sums of positive temperatures vary from 1760ºC (north) to 2050ºC (south). The value of the hydrothermal coefficient varies from 1.7 to 1.8. In the north, podzolic soils, poor in humus and having a significantly acid pH, are widespread. The middle and south taiga spruce forest of Central European type and broad-leaved forest in the west in the presence of ash and oak is typical for this region. The share of sown area of the total area of the region varies from 2.5% to 4% (Darinsky 2001, Lobachev 2003, sel'khozportal.rf 2016, Fick and Hijmans 2017. In the southeast of the study area, Sverdlovsk oblast, the Udmurt Republic and the Republic of Bashkortostan are located. Sverdlovsk oblast is located in the central and southern parts of the Northern Urals, as well as adjacent parts of the West Siberian and East European plains. The climate of the southeast part of EPR is continental. The annual precipitation decreases from north to south and from west to east. The duration of the growing season varies from 160-170 days (in the west and south) to 110-120 days (in the mountain area of the Urals). The sums of positive temperatures vary from 1800°C (in the north) to 2300°C (in the south). The hydrothermal coefficient varies from 0.85 to 1.8 (Tuganaev 2000, Yaparov 2005, Knyazev et al. 2016, sel'khozportal.rf 2016, Fick and Hijmans 2017. Most of the study area is located in the taiga zone, where podzolic, sod-podzolic soils and grey forest soils are most widespread. In the steppe and forest-steppe zones, leached and podzolised chernozems, as well as meadow chernozem soils, are represented. The share of sown area of the total area of the region varies from 5% for the Sverdlovsk oblast to 25% in the Udmurt Republic and the Republic of Bashkortostan. The study of weed species composition was carried out in seven regions. The largest number of occurrences (15164 or 63%) were made in Leningrad oblast, while the fewest occurrences (188 or 0.8%) were made in Vologda oblast (Fig. 1).

Taxonomic coverage
Description: The dataset includes records on weed species belonging to two plant groups (Equisetophyta and Magnoliophyta), 38 families, 182 genera and 329 species. The largest number of weed species (241) was recorded in Leningrad oblast. In other areas, the weed species diversity varied from 110 to 130 species. In Vologda oblast and the Republic of Bashkortostan, an extremely low number of weed species was noted.
The Equisetophyta group was represented by one family Equisetaceae Rich. ex DC. in which there was one genus Equisetum L. and 3 species (about 1% of all the occurrences). The Magnoliophyta group contained most occurrences (  Table 3. Taxonomic distribution of weed species and species occurrences amongst families in the dataset. Families are listed in order of decreasing total number of occurrences. The families Plantaginaceae, Boraginaceae, Rosaceae and Apiaceae are with many species (10-13 species), but a few occurrences (from 160 to 650).