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Fine root distributions of shelterbelt trees and their water sources in an oasis of arid northwestern China
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Shelterbelt trees play an important role in maintaining the sustainability of oases agricultural ecosystems,
but the trees require a considerable amount of water for survival. The objectives of this study were
to investigate the root distributions, transpiration and water sources of shelterbelt trees (Gansu Poplar;
Populus gansuensis) in order to improve water management efficiency. Fine root and soil water distributions
were investigated along three transects that passed through cropland and an adjacent shelterbelt,
while sap flow measurements were conducted on six Gansu Poplar trees. Results showed that roots
were mainly distributed within 5 m of both sides of an irrigation channel passing between the first and
second tree rows. The maximum distance to which trees extended fine roots horizontally was about 18 m
from the shelterbelt. In 2-m soil profiles, fine roots were mainly distributed in the 1.4e2.0 m and 0
e0.4 m layers depending on the available water sources. A positive relationship was observed between
soil water and fine root mass density. Trees grown near the cropland-shelterbelt border exploited water
from cropland irrigation and irrigation channel leakage, greatly enhancing their transpiration. During the
growing season of 2013, the mean total transpiration of trees grown farther away from the border (10.75
and 17.45 m) was 216.9 mm, whereas for trees grown nearer to the border (0.85 and 6.30 m) the amounts
were 670.1 and 488.7 mm, respectively. If the trees were assumed to absorb the same amount of water
from soil, rainfall and groundwater sources, then irrigation water sources provided 67.6% and 55.6% of
the water meeting the transpiration requirements of the trees closest to the border. The results have
important implications for water management in oasis agricultural areas by limiting the extension of
shelterbelt tree roots into adjacent cropland in order to improve irrigation water use efficiency.</div
Differences in hydrological responses for different vegetation types on a steep slope on the Loess Plateau, China
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Extensive vegetation restoration practices have been implemented to control soil erosion on the Loess
Plateau, China. However, no strict guidelines are available to determine the most suitable plant species
for vegetation restoration within a given area. The objective of this study was to quantify the changes
of each component (soil water storage, surface runoff, and actual evapotranspiration) of a water balance
model and soil loss over time under eight different vegetation types, and to further determine the optimal
vegetation type for soil and water conservation and sustainable ecological restoration on the steep slopes
(>25 ) on the Loess Plateau. The results indicated that vegetation type substantially affected soil water
storage and that the greatest soil water storage in both the shallow (0–2 m) and the deep soil layers
(2–5 m) occurred under Bothriochloa ischaemum L. (BOI). Vegetation type also affected surface runoff
and soil losses. The most effective vegetation types for reducing soil erosion were BOI and
Sea-buckthorn (Hippophae rhamnoides L.), while Chinese pine (Pinus tabulaeformis Carr.) and Chinese
pine + Black locust (Robinia pseudoacacia L.) were the most ineffective types. Soil water dynamics and
evapotranspiration varied considerably among the different vegetation types. A soil water surplus was
only found under BOI, while insufficient water replenishment existed under the other seven vegetation
types. The higher water consumption rates of the seven vegetation types could result in soil desiccation,
which could lead to severe water stresses that would adversely affect plant growth. This study suggested
that both vegetation type and its effect on controlling soil erosion should be considered when implementing
vegetation restoration and that BOI should be highly recommended for vegetation restoration
on the steep slopes of the Loess Plateau. A similar approach to the one used in this study could be applied
to other regions of the world confronted by the same problems of water scarcity along with the need for
vegetation restoration.</div
Temporal stability analysis identifies soil water relations under different land use types in an oasis agroforestry ecosystem
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The springwheat–shelterbelt–maize agroforestry ecosystemis one of themost common land use patterns occurring
in oasis agriculture in the arid zones of northwest China. Soil water interactions were hypothesized to exist
between adjacent land use types, and that these interactions could be analyzed by using the soil water content
(SWC) measured at the most time-stable locations (MTSLs) under each land use type. Objectives of this study
were to (1) identify the MTSLs for the different soil layers under each land use type and (2) to investigate the
soil water relations between adjacent land use types using the SWC measured at the identified MTSLs. The
SWC was measured in 2012 and 2013 at 10-cm depth intervals within 0–260 cm soil profiles at 36 locations
along three transects that passed through spring wheat, shelterbelt, andmaize subplots. A time-stability analysis
ofSWCwas used to identify theMTSLs in the four different soil layers under each of the three land use types. The
results indicated that temporal variations in soil water in the same soil layer among the three land use types
tended to have similar patterns. The SWC of the different soil layers undermaize exhibited the highest temporal
stability among the three land use types. TheSWCmeasured at theMTSLs identified for each soil layer under each
land use typewas proven to represent their meanSWC. Correlation analyses of the SWCs measured at theMTSLs
between two land use types indicated that soilwater relations occurred between adjacent land use types but not
between those that were non-adjacent land use types by the correlation analyses of the SWCs measured at the
MTSLs between two land use types. In the upper soil layer (0–200 cm), soilwater relations weremainly affected
by shelterbelt rootwater uptake fromthe adjacent cropland into which the tree roots had extended. In the lower
soil layer (200–260 cm), the soil water relations among the three land use types were due to groundwater recharge,
which was a result of crop irrigation that had raised the water table to a level at which it could replenish
this soil layer.</div
Data for: Composition and variation of soil δ15N stable isotope in natural ecosystems
No full textAll observed soil 15N data are available, which includes the longitude and latitude of sampling locations, mean annual precipitation, mean annual temperature, soil water content, soil total N, SOC, elvation, and soil particle distribution
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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