Scientometrics (2012) 92:735–746 DOI 10.1007/s11192-012-0623-y
Research status and trends in limnology journals: a bibliometric analysis based on SCI database Xiaofeng Cao • Yi Huang • Jie Wang • Shengji Luan
Received: 2 December 2011 / Published online: 17 January 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract An effective bibliometric analysis was applied in this work to evaluate global scientific production of the subject category of ‘‘limnology’’ from 2001 to 2010. Data was based on the Science Citation Index compiled by Institute for Scientific Information (ISI), Philadelphia, USA. The h-index and NetDraw were designed to characterize the limnology publications. The results showed that the limnology research constantly increased over the past decade. The researchers paid most attention to ‘‘diatoms’’, ‘‘eutrophication’’ and ‘‘phosphorus’’. Moreover, the keywords plus of ‘‘growth’’, ‘‘model’’, ‘‘dynamic’’, offered a thorough description for the limnology research. Among the research institutes interested in limnologic research, the US Geological Survey was the flagship while the USA attained a dominant position in the global research in the field. Keywords
Limnology Bibliometric analysis h-index NetDraw
Introduction The limnology is a comprehensive, integrated and scientific understanding of inland waters. It’s usually defined as ‘‘freshwater oceanography’’. As one of interdisciplinary scientific researches focusing on inland waters, limnology incorporates knowledge of geological, physical, chemical, and biological processes at a range of spatial and temporal scales. Inland waters within the purview of modern limnology include lakes, streams, rivers, ground water, and often wetlands (Cole 2009). Numerous studies have been carried X. Cao College of Geomatics, Xi’an University of Science and Technology, Xi’an 710054, China Y. Huang (&) College of Environmental Sciences and Engineering, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871, People’s Republic of China e-mail:
[email protected] J. Wang S. Luan School of Environment and Energy, Shenzhen Graduate School, Peking University, Shenzhen 518055, China
123
736
X. Cao et al.
out on the various aspects of limnology research, such as Tranvik et al. (2009) indicated that inland waters constitute a significant component of the global carbon cycle; Dudgeon et al. (2006) demonstrated that freshwater ecosystems may well be the most endangered ecosystems in the world. What’s more, eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by over-enrichment with P and N (Carpenter et al. 1998), and its research trend was changing to policy and management from technological researches (Huang and Wang 2011). But these studies were mainly basis on analyses of a part or a hot spot, and meanwhile there is no report to analyze the research status and trends of academic field as a whole. As a method for systematic analysis, bibliometric method was used to measure scientific progress in many disciplines, including water resources, ecology, and so on, therefore, the purpose of the research is to analyze the subject category of limnology with bibliometric method based on literature to illustrate global research status and trends on the discipline during the period of 2001–2010. The result could help to better understand the global development of discipline on limnology, and potentially guide limnologist for evaluating and orienting their research.
Materials and methodology Documents used in this work were based on the database of the Science Citation Index which was maintained by the ISI Web of Science, Philadelphia, PA, USA. Online literature searches were carried out using the SCI database. All journals that publish papers mostly on limnology were selected from among 21 journals listed in the subject category of ‘‘limnology’’ indexed by ISI in 2011. Articles originating from England, Scotland, North Ireland, and Wales were reclassified as from the United Kingdom (UK). Papers addressed in Taiwan were not included in China. The impact factor (IF) of a journal was determined for each document as reported in the year 2010 ISI, Journal Citation Reports (JCR), which is the latest data available. Citation counts of all the papers were obtained on November 9th, 2011 when the SCI search process for this study was conducted. Collaboration type was determined by the addresses of the authors, where the term ‘‘single country publication’’ was assigned if the researchers’ addresses were from the same country. The term ‘‘internationally collaborative publication’’ was designated to those papers that were coauthored by researchers from more than one country. The term ‘‘single institute publication’’ was assigned if the researchers’ addresses were from the same institute. The term ‘‘inter-institutionally collaborative publication’’ was assigned if authors were from different institutes. All the papers referring to the subject category of limnology during 2001–2010 were assessed from the following aspects: publication outputs, document type and language, countries, institutes, journals, author keywords, keywords plus, most frequently cited papers and authors h-index. An evaluating indicator, h-index (Hirsch 2005), was applied to characterize the limnology publications. The h-index is an original and simple new measure incorporating both quantity and quality that has many advantages over other bibliometric measures (Kulasegarah and Fenton 2010; Gla¨nzel 2006). NetDraw is a free program written by Borgatti (2002) and arguably the best network visualization package on the market. It can handle multiple relations at the same time. It was used to analyze the correlation of international collaboration and inter-institutional collaboration in this paper.
123
Research status and trends in limnology journals
737
Results and discussion Publication outputs In total, there were 15,899 papers downloaded from the SCI database during 2001–2010 in the subject category of ‘‘limnology’’. The cumulative number of papers consistently increased in this period, as displayed in Fig. 1. Thousand two hundred and sixty seven papers were published in 2001, while the number of papers was 2014 in 2010, about 2 times of that in 2001. Especially, it was the fast-growing period of 2006–2007 which the growth rate reached 16%. Meanwhile, the increase of cumulative number indicated that authors were putting more effort to describe the limnology research than they formerly did. Document type and language Following ISI’s document type classification, 8 documents types were found in the total 15,899 publications during 2001–2010. Articles (14,922) were the most-frequently used document type comprising 93.9% of the total production, followed by proceedings papers (563, 3.5%), editorial materials (445, 2.8%), and reviews (347, 2.2%). The others were less significant, including corrections (139), biographical item (41), reprints (4), and letters (1). For language analysis, there were 15,853 publications published in English, as the most popular language, comprised 99.7% of the total publications and other languages that were less used were French (19, 0.12%), German (16, 0.10%), Portuguese (6, 0.038%), Spanish (3, 0.019%), Romanian (1, 0.006%), and one paper was unspecified. Distribution of outputs in journals Fifteen thousand eight hundred and ninety nine papers were published in 21 searched journals under the subject category of limnology from 2001 to 2010. Comparison of major
Fig. 1 Annual distribution of research papers in journals under SCI category of limnology from 2001 to 2010
123
738
X. Cao et al.
factors (IF, IF rank, number of papers in 2010, and h-index) among all journals is listed in Table 1. The h-index offers a new indicator to the research performance and the IF is also a mature indicator. Water Resources Research published the most papers not only in the past decade (3,989, 25%) but also in 2010, while Limnology and Oceanography had the highest h-index (74) and IF (3.385). Among these journals, the IF and h-index are highly variable. In addition, Bradford’s Law of Scattering (Bradford 1934) was applied. Bradford’s law is a pattern first described by Samuel C. Bradford in 1934 that estimates the exponentially diminishing returns of extending a search for references in science journals. The journals were shorted in descending order in terms of number of papers, and then divided into three approximately equal zones. The first zone containing 2 (9.5%) of 21 journals represents the most productive one-third of the total papers. The second zone with 5 (23.8%) of 21 journals represents the moderate productive one-third of total papers, and the third zone with 14 (66.7%) of 21 journals represents the least productive one-third of total papers. The number of journals in the three zones approximately followed Bradford’s law. To reiterate, the number of journals was close to 1: n: n2 (1:2.6:6.8). Water Resources Research and Limnology and Oceanography were the two Bradford’s core journals in the subject category of limnology.
Table 1 Comparison in major factors among all journals in the SCI category of limnology Journal
TP (%)
IF
R (IF)
h-index
TP (2010)
Water Resources Research
3,989 (25.09)
2.737
2
61
479
Limnology and Oceanography
2,268 (14.27)
3.385
1
74
225
Water Environment Research
1,460 (9.18)
0.890
12
28
165
Marine and Freshwater Research
1,162 (7.31)
1.572
6
33
151
Journal of Great Lakes Research
905 (5.69)
1.305
9
30
132
Journal of Freshwater Ecology
850 (5.35)
0.399
17
15
80
Journal of Paleolimnology
823 (5.18)
2.676
3
38
137
Archiv Fur Hydrobiology
602 (3.79)
N/A
N/A
26
N/A
Aquatic Ecology
461 (2.90)
1.429
8
18
66
Aquatic Sciences
425 (2.67)
1.565
7
30
44
Limnology and Oceanography Methods
411 (2.59)
1.823
4
26
59
Chinese Journal of Oceanology and Limnology
386 (2.43)
0.325
18
5
177
Lake and Reservoir Management
330 (2.08)
0.543
16
13
36
Limnologica
305 (1.92)
1.651
5
17
45
Fundamental and Applied Limnology
303 (1.91)
1.108
11
11
64
Water and Environment Journal
292 (1.84)
0.694
15
9
38
Annales De Limnologie International Journal of Limnology
285 (1.79)
0.796
14
12
28
Limnology
222 (1.40)
0.800
13
12
33
Journal of Limnology
156 (0.98)
1.140
10
8
Journal of The Chartered Institution of Water and Environmental Management
155 (0.98)
N/A
N/A
10
N/A
Amazoniana Limnologia Et Oecologia Regionalis Systemae Fluminis Amazonas
109 (0.69)
N/A
N/A
7
N/A
55
TP (%) total number and percentage of publications, IF impact factor in 2010, R (IF) rank of impact factor
123
Research status and trends in limnology journals
739
Distribution of country/territory There were 313 papers could not be identified their authors’ country or territory information in the ISI Web of Knowledge. Of the 15,586 papers, 12,316 (77.5%) papers were independent publications and 3,450 (21.7%) papers were international collaborative publications. The top 20 most productive countries/territories for total publications were showed in Table 2. Among the top 20 countries/territories were three Asian countries, three American countries, two Oceanian countries and thirteen European countries. The USA ranked first in terms of total, single country and internationally collaborative publications. However, the collaborative papers represented only 24.5% of the total publications from the USA, which was the least than that of other countries in the top 20. Norway, ranked 18th in the number of total publications, but it had the highest proportion (73.6%) collaborative papers. The paper impact of the USA was excellent with the highest h-index (78) among all the countries, followed by Canada (47) and Germany (44). In addition, ten countries had an index of 30–43. It is worth noting that China ranked 6th in the number of total publications, but had the lower h-index of 20. The analysis also demonstrated the rank of country/territory was highly coincident with the distribution ratio of large lakes in the world. Nearly half (48%) of lakes of which the surface area is greater than 500 km2 were found in North America (Herdendorf 1982) that published about 52% papers (Table 2). Table 2 Top 20 most productive countries/territories with publications in all journals under SCI category of limnology during 2001–2010 Countries/territories
TP
TPR (%)
SP
SPR (%)
CP
CPR (%)
RC%
h-index
USA
6,806
1 (42.81)
5,140
1 (41.73)
1,666
1 (48.29)
20 (24.5)
78
Canada
1,422
2 (8.94)
804
3 (6.53)
618
2 (17.91)
14 (43.5)
47
Australia
1,318
3 (8.29)
941
2 (7.64)
377
5 (10.93)
18 (28.6)
41
UK
1,134
4 (7.13)
563
6 (4.57)
571
3 (16.55)
10 (50.4)
43
Germany
1,058
5 (6.65)
567
5 (4.60)
491
4 (14.23)
12 (46.4)
44
China
912
6 (5.74)
656
4 (5.33)
256
9 (7.42)
19 (28.1)
20
France
625
7 (3.93)
304
8 (2.47)
321
6 (9.30)
9 (51.4)
39
Italy
572
8 (3.60)
291
9 (2.36)
281
8 (8.14)
11 (49.1)
31
Spain
495
9 (3.11)
281
10 (2.28)
214
11 (6.20)
15 (43.2)
32
Japan
485
10 (3.05)
324
7 (2.63)
161
13 (4.67)
17 (33.2)
25
The Netherlands
475
11 (2.99)
183
11 (1.49)
292
7 (8.46)
4 (61.5)
41
Switzerland
418
12 (2.63)
162
13 (1.32)
256
10 (7.42)
5 (61.2)
35
Sweden
365
13 (2.30)
163
12 (1.32)
202
12 (5.86)
8 (55.3)
38
New Zealand
233
14 (1.47)
104
15 (0.84)
129
17 (3.74)
7 (55.4)
28
Denmark
232
15 (1.46)
89
20 (0.72)
143
15 (4.14)
3 (61.6)
34
Israel
220
16 (1.38)
93
19 (0.76)
127
18 (3.68)
6 (57.7)
26
Belgium
210
17 (1.32)
79
22 (0.64)
131
16 (3.80)
2 (62.4)
22
Norway
197
18 (1.24)
52
28 (0.42)
145
14 (4.20)
1 (73.6)
30
Brazil
185
19 (1.16)
104
14 (0.84)
81
20 (2.35)
13 (43.8)
17
Finland
177
20 (1.11)
102
16 (0.83)
75
21 (2.17)
16 (42.4)
25
TP total publications, SP single country publications, CP internationally collaborative publications; R rank; % share in publication, RC% percentage of internationally collaborative publication in total publications of each country
123
740
X. Cao et al.
Using NetDraw, a core group of countries in the collaboration network is visualized (Borgatti 2002). NetDraw measures the relative importance of nodes within the network and could be viewed as an indicator of countries’ positions within the collaboration network in our study (Liu et al. 2011). The thickness of links shows the strength of correlation, and the size of nodes shows the amount of single country publication. In this study, The United States took the central position in the network of international collaboration, and it was the principal collaborator with major productive countries, such as the UK and Germany. The network showed the strongest correlation between the USA and Canada as well (Fig. 2). It could be a result from the transboundary Laurentian Great Lakes basin between USA and Canada which promoted the collaboration of the two countries. Distribution of institutes There were 319 papers without their authors’ institute information on the ISI Web of Knowledge. Of the 15,580 papers, 6,939 (43.6%) papers were independent publications and 8,641 (54.3%) papers were inter-institutional collaborations. Except for Chinese Academy of Sciences and Environment Canada, all of the other institutes were from America in the top 20 most productive institutes. The US Geological Survey published the most total publications and the inter-institutionally collaborative publications. Moreover, the h-index (36) of US Geological Survey was the highest among all the institutes. There were six institutes under the h-index of 20. Environment Canada ranked the 14th in the number of total publications, but it had the highest percentage of collaborative papers. Table 3 also demonstrated that University of Minnesota has strongly independent research ability and less desire to collaboration with other institutes in limnology research. But equally remarkable, China ranked 2nd in the number of total publications, but still had the lowest h-index of 13. Figure 3, produced from NetDraw program, shows a cluster of top 50 institutes based on the number of papers to the collaboration network (Fig. 3). The results displayed that institutions in the United States, especially those affiliated with the university system,
Fig. 2 The network of international collaboration among the top 50 countries/territories based on total number of papers published in journals under SCI category of limnology from 2001—2010
123
Research status and trends in limnology journals
741
Table 3 Top 20 most productive institutes in publications in all journals under SCI category of limnology during 2001–2010 Institute
TP
TPR (%)
SP
SPR (%)
CP
CPR (%)
RC %
hindex
US Geological Survey
449
1 (2.82)
124
2 (1.79)
325
1 (3.76)
12 (72.4)
36
Chinese Academy of Sciences
420
2 (2.64)
153
1 (2.20)
267
2 (3.09)
18 (63.6)
13
University of Wisconsin
202
3 (1.27)
52
5 (0.75)
150
3 (1.74)
9 (74.3)
26
University of Minnesota
184
4 (1.16)
75
3 (1.08)
109
10 (1.26)
20 (59.2)
24
University of California, Berkeley
183
5 (1.15)
68
4 (0.98)
115
8 (1.33)
19 (62.8)
25
Michigan State University
175
6 (1.10)
36
15 (0.52)
139
4 (1.61)
5 (79.4)
24
University of Arizona
172
7 (1.08)
45
6 (0.65)
127
6 (1.47)
10 (73.8)
30
NOAA
160
8 (1.01)
27
30 (0.39)
133
5 (1.54)
2 (83.1)
24
University of Waterloo
149
9 (0.94)
44
7 (0.63)
105
11 (1.22)
13 (70.5)
24
Oregon State University
142
10 (0.89)
26
33 (0.37)
116
7 (1.34)
3 (81.7)
29
University of Washington
139
11 (0.87)
44
7 (0.63)
95
16 (1.10)
15 (68.3)
28
Stanford University
138
12 (0.87)
37
11 (0.53)
101
14 (1.17)
11 (73.2)
25
University of Michigan
135
13 (0.85)
33
18 (0.48)
102
12 (1.18)
8 (75.6)
19
Environment Canada
134
14 (0.84)
20
60 (0.29)
114
9 (1.32)
1 (85.1)
18
University of Colorado
130
15 (0.82)
28
26 (0.40)
102
13 (1.18)
7 (78.5)
29
University Western Australia
126
16 (0.79)
42
9 (0.61)
84
21 (0.97)
16 (66.7)
23
US EPA
125
17 (0.79)
24
39 (0.35)
101
15 (1.17)
4 (80.8)
19
University of Florida
124
17 (0.78)
37
11 (0.53)
87
20 (1.01)
14 (70.2)
19
University of Illinois
122
19 (0.77)
41
10 (0.59)
81
24 (0.94)
17 (66.4)
19
CSIC
121
20 (0.76)
26
31 (0.37)
95
17 (1.10)
6 (78.5)
24
TP total publications, SP single institute publications, CP inter-institutionally collaborative publications, R rank, % share in publication, C% percentage of inter-institutionally collaborative publication in total publications of each institute
Fig. 3 The network of inter-institutional collaboration among the top 50 institutes based on the number of papers published in all journals under SCI category of limnology during 2001—2010
123
742
X. Cao et al.
tended to collaboration more with each other. By comparison, although the Chinese Academy of Sciences produced a substantial amount of publications, its links with other institutes were fewer except for Ocean University of China. Distribution of author keywords and keywords plus analysis The author keywords of total 8,682 papers with records including keywords in the SCI database during 2001–2010 were undertaken. Analysis of author keywords in this work revealed that altogether 45,894 were used. 14,209 (31%) author keywords appeared only once, 5,914 (13%) author keywords appeared twice and 3,003 (6.5%) appeared three times. 25 most frequently used author keywords and its rank and percentage in different period were listed in Table 4, which showed the mainstream research in limnology and mainly focused on ‘‘diatoms’’, ‘‘eutrophication’’, ‘‘phosphorus’’, ‘‘phytoplankton’’, ‘‘water quality’’ and so on. Obviously, ‘‘groundwater’’ ranked second in the 2001–2003 period, but it only ranked 79th in the 2007–2010 period, which indicated that groundwater might be one of research hot spots in the coming decade. Table 4 Top 25 most frequent author keywords used in papers published in all journals under SCI category of limnology during 2001–2010 Author keywords
2001–2010 TP
2001–2010 R (%)
2001–2003 R (%)
Diatoms Eutrophication Phosphorus
2004–2006 R (%)
2007–2010 R (%)
254
1 (1.60)
1 (1.57)
1 (1.80)
226
2 (1.42)
3 (1.11)
3 (1.24)
1 (1.69)
213
3 (1.34)
5 (1.01)
2 (1.58)
3 (1.37)
2 (1.49)
Phytoplankton
163
4 (1.03)
11 (0.81)
4 (1.10)
5 (1.09)
Water quality
159
5 (1.00)
10 (0.83)
7 (0.83)
4 (1.19)
Climate change
158
6 (0.99)
6 (0.99)
7 (0.83)
5 (1.09)
Paleolimnology
149
7 (0.94)
3 (1.11)
11 (0.77)
7 (0.95)
Great Lakes
136
8 (0.86)
9 (0.91)
15 (0.68)
8 (0.93)
Nitrogen
130
9 (0.82)
11 (0.81)
14 (0.68)
9 (0.91)
Sediment
128
10 (0.81)
14 (0.68)
7 (0.83)
12 (0.85)
Nutrients
126
11 (0.79)
15 (0.66)
11 (0.77)
11 (0.88)
Zooplankton
124
12 (0.78)
22 (0.56)
11 (0.77)
9 (0.91)
Groundwater
114
13 (0.72)
2 (1.39)
5 (0.88)
79 (0.27)
Holocene
104
14 (0.65)
13 (0.78)
20 (0.56)
16 (0.64)
Macroinvertebrates
94
15 (0.59)
27 (0.53)
18 (0.59)
18 (0.63)
Cyanobacteria
94
15 (0.59)
44 (0.40)
34 (0.43)
13 (0.79)
Modeling
92
17 (0.58)
8 (0.96)
58 (0.09)
25 (0.52)
Wastewater
92
17 (0.58)
44 (0.40)
22 (0.54)
14 (0.69)
Lake Erie
91
19 (0.57)
35 (0.48)
7 (0.83)
29 (0.47)
Temperature
89
20 (0.56)
35 (0.48)
24 (0.52)
18 (0.63)
Lake Michigan
81
21 (0.51)
16 (0.61)
24 (0.52)
31 (0.45)
Lake sediments
81
21 (0.51)
33 (0.51)
257 (0.14)
22 (0.55)
Activated sludge
80
23 (0.50)
16 (0.61)
20 (0.56)
36 (0.41)
Macrophytes
79
24 (0.50)
85 (0.28)
49 (0.36)
14 (0.69)
Biodiversity
78
25 (0.49)
85 (0.28)
17 (0.61)
23 (0.53)
TP total publications, R (%) rank and percentage of the author words in total publications
123
Research status and trends in limnology journals
743
Table 5 Top 25 most frequent keywords plus used in papers published in all journals under SCI category of limnology during 2001–2010 Keywords plus
2001–2010 TP
2001–2010 R (%)
2001–2003 R (%)
2004–2006 R (%)
2007–2010 R (%)
Water Growth
856
1 (5.38)
1 (5.94)
1 (5.21)
1 (5.19)
771
2 (4.85)
2 (4.91)
3 (4.87)
5 (4.81)
Phytoplankton
759
3 (4.77)
4 (4.35)
2 (4.94)
3 (4.90)
Model
754
4 (4.74)
3 (4.73)
4 (4.53)
4 (4.87)
Dynamic
704
5 (4.43)
7 (3.39)
5 (4.19)
2 (5.11)
Flow
587
6 (3.69)
6 (4.02)
6 (3.65)
6 (3.54)
Transport
579
7 (3.64)
5 (4.30)
7 (3.45)
8 (3.41)
River
484
8 (3.04)
8 (3.16)
8 (3.25)
10 (2.86)
Variability
461
9 (2.90)
20 (2.15)
14 (2.64)
7 (3.45)
Patterns
445
10 (2.80)
15 (2.45)
16 (2.52)
9 (3.14)
Nitrogen
440
11 (2.77)
9 (2.68)
9 (3.00)
14 (2.68)
Temperature
425
12 (2.67)
16 (2.43)
11 (2.75)
11 (2.76)
Sediments
423
13 (2.66)
10 (2.66)
15 (2.61)
12 (2.69)
Zooplankton
417
14 (2.62)
13 (2.53)
13 (2.70)
15 (2.62)
Communities
416
15 (2.62)
11 (2.63)
17 (2.48)
13 (2.69)
Phosphorus
411
16 (2.59)
14 (2.50)
11 (2.75)
16 (2.53)
Carbon
386
17 (2.43)
18 (2.23)
10 (2.84)
19 (2.29)
Fish
373
18 (2.35)
19 (2.18)
18 (2.39)
17 (2.41)
Lake
354
19 (2.23)
20 (2.15)
20 (2.21)
20 (2.28)
Porous-media
337
20 (2.12)
12 (2.61)
21 (2.16)
29 (1.84)
Organic-matter
323
21 (2.03)
43 (1.29)
19 (2.37)
21 (2.22)
Assemblages
307
22 (1.93)
25 (1.80)
26 (1.74)
23 (2.12)
Fresh-water
303
23 (1.91)
36 (1.39)
21 (2.16)
25 (2.02)
Great Lakes
297
24 (1.87)
22 (2.02)
25 (1.76)
28 (1.85)
Ecosystems
297
24 (1.87)
32 (1.54)
53 (1.31)
18 (2.37)
TP total publications, R (%) rank and percentage of the keywords plus in total publications
The keywords plus, as a new search capability, can provide new ideas and avenues, helping to focus your search (Garfield 1990). There were 14,437 papers with records that included keywords plus, 76.5% of all 115,228 keywords plus appeared more than three times. Table 5 showed the distribution of top 25 most frequent keywords plus. ‘‘phytoplankton’’, ‘‘nitrogen’’, ‘‘temperature’’, ‘‘sediment’’, ‘‘zooplankton’’, ‘‘phosphorus’’ and ‘‘Great Lakes’’ were also used in the keywords plus analysis as well as the author keywords analysis, which had been taken as the hot topic. The rank of ‘‘variability’’, ‘‘patterns’’ and ‘‘temperature’’ raised from 20th, 15th, 16th in 2001–2003 period to 7th, 9th, 11th in 2007–2010 period, respectively. Furthermore, ‘‘growth’’, ‘‘model’’, ‘‘dynamic’’, ‘‘flow’’, ‘‘transport’’, ‘‘variability’’, ‘‘patterns’’, ‘‘communities’’ offered a thorough description for the author keywords analysis in limnology research. Most frequently cited papers Among all the papers referring to the subject category of limnology in the period of 2001–2010, there were 151,496 citations for an average of 9.53 citations per paper. But
123
744
X. Cao et al.
Table 6 Top 20 most productive authors from papers published in all journals under SCI category of limnology during 2001–2010 Author
TP
TPR (%)
h-index
R (h-index)
Country
Smol JP
49
1 (0.167)
14
6
Xie P
44
2 (0.150)
6
19
China
Effler SW
39
3 (0.133)
10
15
USA
Rodriguez-Iturbe I
38
4 (0.130)
14
6
USA
Rinaldo A
36
5 (0.123)
14
6
Italy
Hecky RE
32
6 (0.109)
14
6
Canada
Canada
Ebener MP
31
7 (0.106)
7
18
Lotter AF
30
8 (0.102)
15
4
USA Switzerland
Wuest A
29
9 (0.099)
12
11
Switzerland
Jones ML
29
10 (0.099)
18
1
Imberger J
28
11 (0.095)
11
12
Middelburg JJ
26
12 (0.095)
16
2
Or D
26
13 (0.089)
10
15
USA
Sivapalan M
25
14 (0.089)
11
12
Austria
Porporato A
25
15 (0.085)
11
12
USA
Cirpka OA
25
16 (0.085)
10
15
Germany
Kong FX
24
17 (0.085)
4
20
McDonnell JJ
23
18 (0.082)
16
2
USA Australia The Netherlands
China The Netherlands
Cole JJ
23
19 (0.078)
14
6
USA
Jeppesen E
22
20 (0.078)
15
4
Denmark
TP total publications, R rank, % percentage of papers author published in total publications
only 30.4% of all papers were above average. The most frequently cited paper was ‘‘Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results’’, which was published in Journal of Paleolimnology by Heiri et al. (2001) from University of Bern in Switzerland and had been cited 543 times by 2010. The second most frequently paper headed ‘‘Variation in delta N-15 and delta C-13 trophic fractionation: Implications for aquatic food web studies’’ was exhibited in Limnology and Oceanography in 2001. It was written by Vander Zanden and Rasmussen (2001) from University of Wisconsin in USA and cited 421 times by 2010. To conclude, the most frequently cited papers had caused a significant influence on the limnology research and it would mean a lot more for the future. Authors h-index In this work, 29,330 authors were signed in the total 15,899 papers. 15.7% of all authors published more than ten papers by 2010. The top 20 most productive authors were listed in Table 6. Among the top 20 authors, seven authors were from USA, followed respectively by China (2), Canada (2), Switzerland (2), The Netherlands (2), Australia (1), Austria (1), Germany (1), Italy (1) and Denmark (1). Smol (Table 6) who published the greatest number of papers had an h-index of 14, and was ranked 6th. It is noted that Jones (Table 6) was ranked 10th in the number of papers but he had the highest h-index of 18. Though Kong FX (Table 6) ranked 17th in the number of papers, he had only 4 which was the lowest h-index in the top 20 most productive authors.
123
Research status and trends in limnology journals
745
Discussion and conclusions For the bibliometric analysis in the subject category of limnology, we obtained some significant points on the global research performance throughout the period from 2001 to 2010. In total, there were 15,899 papers downloaded from the SCI database during 2001–2010. The cumulative number of papers consistently increased in this period. Eight documents types were found and article was the most-frequently used document type comprising 93.9% of the total production. English was the dominant language, and other five languages were also used. Limnology and Oceanography had the highest h-index and IF. Water Resources Research and Limnology and Oceanography were the two Bradford’s core journals in the subject category of ‘‘limnology’’. Limnology traditionally was closely related to hydrobiology, which was concerned with the application of the principles and methods of physics, chemistry, geology, and geography to ecological problems. However, with the global environment changes, more new topics, which are related to the limnology, were mentioned, for instance ‘‘water quality’’, ‘‘watershed management’’. Therefor journals listed in the subject category of ‘‘water resources’’ indexed by ISI, such as water research, water resources management, and other relevant journals should be simultaneously included in the subject category of ‘‘limnology’’. The USA attained a dominant position in the limnology research by contributing the greatest number of single-country and internationally collaborative papers. The US Geological Survey was the flagship in this field. Furthermore, according to the geographic distribution of network, the majority of papers were chiefly distributed in North America and Europe, while USA, UK and Germany were the most important centers of international cooperation. Author Keywords analysis showed that the limnology research mainly focused on ‘‘diatoms’’, ‘‘eutrophication’’ and ‘‘phosphorus’’. ‘‘water’’, ‘‘growth’’, ‘‘phytoplankton’’ were the top 3 most frequent keywords plus. As a result, the trends of research in limnology were changing to water quality or eutrophication, aquatic and relevant techniques. The most frequently cited paper was ‘‘Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results’’, which was published in Journal of Paleolimnology by Heiri et al. (2001) from Switzerland and had been cited 543 times by 2010. Smol (Table 6) who published the greatest number of papers had an h-index of 14, but Jones (Table 6) had the highest h-index of 18.
References Borgatti, S. P. (2002). NetDraw network visualization. USA: Analytic technologies. Bradford, S. C. (1934). Sources of information on specific subjects. British Journal of Engineering, 137, 85–86. Carpenter, S. R., Caraco, N. F., & Correll, D. L. (1998). Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications, 8(3), 559–568. Cole J. J. (2009). Limnology as a discipline. Encyclopedia of inland waters (pp. 6–13). Waltham: Academic Press. Dudgeon, D., Arthington, A. H., Gessner, M. O., et al. (2006). Freshwater biodiversity: Importance, threats, status and conservation challenges. Biological Reviews, 81, 163–182. Garfield, E. (1990). KeyWords Plus: ISI’s breakthrough retrieval method. Part 1. Expanding your searching power on current contents on diskette. Current Comments, 32, 295–299. Gla¨nzel, W. (2006). On the opportunities and limitations of the H-index. Science Focus, 1(1), 10–11.
123
746
X. Cao et al.
Heiri, O., Lotter, A. F., & Lemcke, G. (2001). Loss on ignition as a method for estimating organic and carbonate content in sediments: Reproducibility and comparability of results. Journal of Paleolimnology, 25(1), 101–110. Herdendorf, C. E. (1982). Large lakes of the world. Journal of Great Lakes Research, 8(3), 379–412. Hirsch, J. E. (2005). An index to quantify an individual’s scientific research output. Proceedings of the National Academy of Sciences of the United States of America, 102(46), 16569–16572. Kulasegarah, J., & Fenton, J. E. (2010). Comparison of the h index with standard bibliometric indicators to rank influential otolaryngologists in Europe and North America. European Archives of Oto-RhinoLaryngology, 267, 455–458. Liu, X., Zhang, L., & Hong, S. (2011). Global biodiversity research during 1900–2009: A bibliometric analysis. Biodiversity and Conservation, 20, 807–826. Tranvik, L. J., Downing, J. A., & Cotner, J. B. (2009). Lakes and reservoirs as regulators of carbon cycling and climate. Limnology and Oceanography, 54(6), 2298–2314. Vander Zanden, M. J., & Rasmussen, J. B. (2001). Variation in delta N-15 and dela C-13 trophic fractionation: Implications for aquatic food web studies. Limnology and Oceanography, 46(8), 2061–2066. Yi, H., & Jie, W. (2011). A bibliometric study of the trend in articles related to eutrophication published in Science Citation Index. Scientometrics, 89, 919–927.
123
