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\begin{document}

\title{Ecological stoichiometric characteristics of nitrogen and phosphorus in
leaves, stems and roots of Haloxylon ammodendron in southern
Gurbantunggut Desert and their relationship with soil factors}



\author[1]{Cuimeng Lian}%
\author[1]{Kaijuan Du}%
\author[2]{Yan Luo}%
\author[1]{zhipeng De}%
\author[3]{Yanming Gong}%
\affil[1]{xinjiang daxue dianqi gongcheng xueyuan}%
\affil[2]{Xinjiang University}%
\affil[3]{Xinjiang Institute of Ecology and Geography}%


\vspace{-1em}



  
  \date{May 21, 2024}


\begingroup
\let\center\flushleft
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\maketitle
\endgroup





\selectlanguage{english}
\begin{abstract}
In order to explore the stoichiometric characteristics of nitrogen (N)
and phosphorus (P) of Haloxylon ammodendron on the south edge of
Gurbantungut Desert, and to reveal the adaptability of desert plants to
nutrient utilization in barren habitats, this study took the south edge
of Gurbantungut Desert in Xinjiang as a typical area. The contents of N
and P in leaves, stems and roots of H. ammodendron were measured and
analyzed, and the correlation between the ecological stoichiometry of N
and P in organs and soil factors was discussed, as well as the influence
of the samples and organs. The results showed as follows: (1) There were
significant differences in N content, P content and N:P among different
organs of H. ammodendron, and the trend of each index was roughly the
same. The general trend was higher in leaves, followed by stems and
roots. (2) Correlation analysis showed that N content in all organs of
H. ammodendron was positively correlated with soil total nitrogen. P
content in leaves and roots was significantly positively correlated with
soil total P, while P content in stems was significantly negatively
correlated with soil total P. P content in all organs was negatively
correlated with soil N:P. The contents of N, P and N:P in different
organs were negatively correlated with soil pH and electrical
conductivity. (3) General linear model analysis showed that organs had
great influence on N content, P content and N:P of H. ammodendron.%
\end{abstract}%



\sloppy


\textbf{Ecological stoichiometric characteristics of nitrogen and
phosphorus in leaves, stems and roots of Haloxylon ammodendron in
southern Gurbantunggut Desert and their relationship with soil factors}

Cuimeng Lian\textsuperscript{1}, Kaijuan Du\textsuperscript{1}, Yan
Luo\textsuperscript{1*}, De zhi Peng\textsuperscript{1}, Yanming
Gong\textsuperscript{2,3*}

\textsuperscript{1} College of Ecology and Environment, Xinjiang
University, Urumqi 830017, China

\textsuperscript{2}Bayinbuluk Grassland Ecosystem Research Station,
Xinjiang Institute of Ecology and Geography, Chinese Academy of
Sciences, Bayinbuluk 841314, China

\textsuperscript{3}CAS Research Center for Ecology and Environment of
Central Asia, Urumqi 830011, China

Corresponding Author:

Yan Luo\textsuperscript{1}

Address: 777 Huarui street, Urumqi 830017, China

Email address: \emph{luoyan505@xju.edu.cn}

Yanming Gong\textsuperscript{2,3}

Address: 818 South Beijing Road, Urumqi 830011, China

Email address: gongym@ms.xjb.ac.cn

\textbf{Abstract}

In order to explore the stoichiometric characteristics of nitrogen (N)
and phosphorus (P) of \emph{Haloxylon ammodendron} on the south edge of
Gurbantungut Desert, and to reveal the adaptability of desert plants to
nutrient utilization in barren habitats, this study took the south edge
of Gurbantungut Desert in Xinjiang as a typical area. The contents of N
and P in leaves, stems and roots of \emph{H. ammodendron} were measured
and analyzed, and the correlation between the ecological stoichiometry
of N and P in organs and soil factors was discussed, as well as the
influence of the samples and organs. The results showed as follows: (1)
There were significant differences in N content, P content and N:P among
different organs of \emph{H. ammodendron} , and the trend of each index
was roughly the same. The general trend was higher in leaves, followed
by stems and roots. (2) Correlation analysis showed that N content in
all organs of \emph{H. ammodendron} was positively correlated with soil
total nitrogen. P content in leaves and roots was significantly
positively correlated with soil total P, while P content in stems was
significantly negatively correlated with soil total P. P content in all
organs was negatively correlated with soil N:P. The contents of N, P and
N:P in different organs were negatively correlated with soil pH and
electrical conductivity. (3) General linear model analysis showed that
organs had great influence on N content, P content and N:P of \emph{H.
ammodendron} .

\textbf{Keywords:} \emph{Haloxylon ammodendron} ; Gurbantungut Desert;
Ecological stoichiometry; Correlation analysis; Soil factor

\textbf{Introduction}

Ecological stoichiometry is a scientific theory to study the balance and
relationship between the elements of ecosystem (especially N and P).
This theory applies the methods and principles of chemistry, physics and
other disciplines to study the content and ratio characteristics of
organic elements and their changes with the environment at different
scales and levels in the field of ecology (Hu et al., 2020; Niklas,
2006). The analysis of the relationship between the content and ratio of
various chemical elements in plants and environmental factors is of
great significance for us to understand the nutrient utilization and
nutrient limitation of plants, the chemical cycle of bio-earth and the
function of community or ecosystem (Niklas, 2006).

N and P are essential nutrients for plant growth, and N is an important
element for plant protein and chlorophyll synthesis. P is an important
element that constitutes nucleic acid and ATP, both of which affect the
normal metabolism, growth and development, morphology and function of
plants (Hu et al., 2020). The N and P stoichiometric characteristics of
plants can reflect the growth rate, productivity level and the
effectiveness of soil resources to a certain extent. The productivity of
plants is often positively correlated with leaf N content, and the
growth rate is positively correlated with leaf P content (Reich et al.,
2009; Niklas \& Cobb, 2005). The characteristics of N content, P content
and stoichiometric ratio in different plant organs are different due to
the difference of nutrient distribution, storage and function. Leaf is
the organ of plant photosynthesis, stem is the nutrient organ between
root and leaf, and root is an important organ for plant to absorb and
transport water and nutrient elements underground. There are significant
differences in N content and P content in plant leaves at different
research levels, which are mainly determined by genetic factors and
environmental factors (Chen et al., 2022). In general, the N content and
P content of plant leaves with faster growth and shorter life are
higher, and the N content and P content of plant leaves with slower
growth and longer life are lower (Han et al., 2005). The lifespan of
roots is shorter than that of leaves and stems, decomposes faster, and
is greatly affected by soil nutrients (Jackson et al., 1997). The
content of N and P elements in the leaves of Alashan desert plants is
higher than that in stems and roots (He et al., 2016), which indicates
that plants tend to invest more N and P into leaves, reduce the openness
of stomata, and save water while improving the efficiency of
photosynthesis (Liu et al., 2022; He et al., 2016). In addition, desert
plants also adapt to the arid and barren environment in the desert by
reabsorbing the nutrients of senescent leaves (He et al., 2015;
Drenovsky et al., 2010).

The available N and P contents in soil environment have profound effects
on the ecological stoichiometric characteristics of N and P in plants.
The soil in high latitudes is relatively young, and the ability of
parent rock to release P is strong, but the content of N is low, so
plant growth is usually limited by N element; The soil in low latitudes
is ancient, the ability of parent rock to release P is weak, the content
of N is high, and plant growth is usually limited by P element (Reich \&
Oleksyn, 2004). In addition, when the availability of nutrients in the
soil changes, plants will enhance their ability to obtain external
nutrient resources by changing external morphology and regulating
internal physiological functions (Fransen \& De Kroon, 2001; Jackson et
al., 1996). When soil N supply is insufficient, plants allocate more
biomass to the belowground part to expand root growth, which helps roots
to obtain more N (Song \& Hou, 2020). The soil conditions of different
deserts in China are quite different, and the soil total nitrogen and
total phosphorus are lower than the national level. Therefore, desert
plants may be limited by both N and P elements. The N and P contents of
leaves, roots and litters of northern desert plants were positively
correlated with soil N and P contents, indicating that their N and P
stoichiometric characteristics were affected by soil factors. Therefore,
it is of great significance to study the characteristics of N content, P
content and stoichiometric ratio of plant leaves, stems, roots and soil
for understanding the distribution of nutrients in various organs during
plant growth, the utilization efficiency of soil nutrients and revealing
the adaptation mechanism of plants to the environment (Wen et al.,
2021).

Through the review of domestic and foreign research, it is found that
domestic and foreign scholars have done a lot of work on the study of
plant ecological stoichiometry in various ecosystems, and have achieved
extremely fruitful research results. At present, the research mainly
focuses on the stoichiometric characteristics of plant leaves, less
attention is paid to stems and fine roots, and the research on the
relationship between ecological stoichiometry of plant leaves, stems and
roots and soil factors in desert ecosystems needs to be further
strengthened. Taking the southern margin of Gurbantunggut Desert as a
typical sample area, this paper focuses on the stoichiometric
characteristics of N and P in leaves, stems and roots of H. ammodendron
in different places of the south edge of Gurbantunggut Desert, in order
to enrich the research results of plant ecological stoichiometry in
desert ecosystem.

Gurbantunggut Desert is located in the center of the Junggar Basin and
has a unique climate-soil-vegetation type diversity. It has typical
scientific value for studying the ecological geographical pattern of
plant stoichiometry and its driving mechanism (Zhang et al.,
2020).\emph{H. ammodendron} is the main constructive species and one of
the most distinctive landscape vegetation in the Gurbantunggut Desert
(Liu et al., 2021) . It plays an important role in maintaining the local
ecological balance and plant community composition (Li et al., 2014).
However, for half a century, environmental degradation, deforestation
and overgrazing have led to the decline and even death of a large area
of \emph{Haloxylon Bunge} , which seriously threatened the stability of
ecosystem function in Gurbantunggut Desert. In this study, the south
edge of the Gurbantunggut Desert was taken as the research area. The
characteristics of N content, P content and stoichiometric ratio of
different organs (leaves, stems and fine roots) and soil of typical
plant \emph{H. ammodendron} in this area were studied. The correlation
between the stoichiometric characteristics of\emph{H. ammodendron} and
soil factors was discussed in order to provide a scientific basis for
revealing how plants in desert ecosystems adapt to the environment.

\textbf{Materials and Methods}

2.1 Study area

Gurbantunggut Desert is located in the center of the Junggar Basin in
northern Xinjiang (44\selectlanguage{ngerman}°11'-46°20'N, 84°31'-91°00'E). It is the second
largest desert in China and the largest fixed and semi-fixed desert in
China (Tian et al., 2022).

The study area is located in the south edge of the Gurbantunggut Desert.
The terrain in this area is high in the northeast and low in the
southwest, with an altitude of 400-700 m. It belongs to a typical
temperate continental climate. It is hot and dry in summer and cold and
long in winter. The annual average temperature is 5-5.7 °C, the maximum
temperature is above 40 °C, the minimum temperature is below -40 °C, the
annual evaporation is 2000-2800 mm, the annual precipitation is 80-160
mm, and the winter snow depth is 10-30 cm (Tursun et al., 2022). Desert
soil is mainly fixed, semi-fixed sandy soil (Zhao et al., 2019), loose
matrix, nutrient-poor. The main vegetation is \emph{H. ammodendron}
,\emph{Ephedra} \emph{przewalskii Stapf} , \emph{Artemisiadesertorum}
\emph{Spreng.} \emph{Syst.} \emph{Veg} ,\emph{Ceratoideslatens}
(\emph{J.} \emph{F.} \emph{Gmel.} ) \emph{Reveal et Holmgren} , etc (Tan
et al., 2021).

From west to east, 5 samples of Karamay, Kuitun, Shihezi, Fukang and
Qitai were selected in the south of Gurbantunggut Desert (Table 1).

Table 1 Basic Situation of Sample Plot\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Plot name\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
longitude (\selectlanguage{ngerman}°E)\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Latitude (\selectlanguage{ngerman}°N)\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
Elevation (m)\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
MAT ()\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
MAP (mm)\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Kuitun\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
84.86\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
44.85\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
295\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
8.70\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
118\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Karamay\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
85.03\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
45.29\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
270\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
8.89\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
114\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
FuKang\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
88.30\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
44.52\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
499\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
7.63\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
169\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Qitai\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
90.06\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
44.81\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
563\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
8.68\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
109\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
Shi hezi\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
85.15\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
44.72\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
366\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
9.07\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
122\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

\par\null

2.2 Sampling methods

The sampling time of this study was July 2019. A 20 m \selectlanguage{ngerman}× 20 m quadrat was
set up in 5 samples, and the plants in the quadrat were collected in
individual units, 10 replicates were collected in each quadrat, and the
fresh weight was not less than 5 g. Aboveground organs were collected by
branch shear method, and underground organs were collected by excavation
method. Put the collected samples into a marked envelope and bring them
back to the laboratory to determine the element content of each organ.

While collecting plant samples, soil samples were collected by S-type
multipoint sampling method. Ten sampling points were set up in each
quadrat, and 0-50 cm soil was mixed. After removing the roots, stones
and other litters of the mixed soil samples, about 1 kg of average
samples were retained and sealed in a numbered plastic bag.

2.3 Methods of sample treatment

The plant samples were dried to constant weight at 65 °C in an oven, and
the dry weight of the plant samples was recorded. Each organ of the
sample was ground with a pulverizer and passed through an 80-mesh sieve,
weighed, bagged and sealed for the determination of N and P contents
in\emph{H. ammodendron} and the calculation of N:P ratio. The total
nitrogen content of each organ of \emph{H. ammodendron} was determined
by Kjeldahl method, and the total phosphorus content was determined by
molybdenum antimony colorimetry. The results of N and P determination
were expressed as nutrient content per unit mass (mg/g).

The collected soil samples were air-dried, the plant roots and stones in
the soil samples were removed, ground through a 60-mesh sieve, and
bagged for testing. Soil samples measured indicators include : pH,
conductivity, total nitrogen, total phosphorus. The soil pH was
determined by redox potentiometer, and the soil conductivity was
determined by electrode method; Soil total nitrogen and total phosphorus
determination methods are the same as plants. Longitude, latitude and
altitude data are measured using GPS during sampling.

2.4 Statistic methods

Excel 2019 and SPSS 26.0 were used for data preprocessing, drawing and
statistical analysis of the experimental data; One-way analysis of
variance was used to test the stoichiometric characteristics of N and P
in the leaves, stems and roots of \emph{H. ammodendron} and the
difference of soil factors. Duncan 's method was used for multiple
comparisons, the significance level of difference was 0.05; The
relationship between stoichiometric characteristics of \emph{H.
ammodendron} organs and soil factors was tested by Pearson correlation
analysis; The effects of different samples and organs on the
stoichiometric characteristics of N and P in \emph{H. ammodendron} use
the general linear model to analyze the main factor effects and
interactions.

\par\null

\textbf{Results and analysis}

3.1 Ecological stoichiometric characteristics of N and P in \emph{H.
ammodendron}

3.1.1 Characteristics of N content, P content and stoichiometric ratio
in different organs of \emph{H. ammodendron}

The N content, P content and stoichiometric ratio of \emph{H.
ammodendron} in the study area were analyzed by classical statistics.
The results are shown in Table 2.The overall N and P contents of\emph{H.
ammodendron} ranged from 30.93 to 68.35 mg/g and from 1.96 to 5.54 mg/g,
with an average of 48.72 and 2.82 mg/g, respectively. The range was
37.42 and 3.58 mg / g, respectively. By further analyzing the
stoichiometric ratio of N and P in \emph{H. ammodendron} , it can be
seen that the range of N:P is 7.67-26.56, with an average of 17.97.

Table 2 Statistical analysis of ecological N and P stoichiometry of
spindle spindle\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
\begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Parameter\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Mean (mg/g)\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
SD\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Range (mg/g)\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Min (mg/g)\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Max (mg/g)\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Bias angle\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
Peak\strut
\end{minipage} & \begin{minipage}[t]{0.10\columnwidth}\raggedright\strut
CV\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Leaf\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
19.80\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.41\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
20.19\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
10.10\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
30.29\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.12\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.11\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.22\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.07\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.21\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.09\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.54\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.63\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.21\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.82\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.20\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N:P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
18.97\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.85\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
19.15\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
9.00\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
28.15\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.13\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.76\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.26\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
16.68\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
5.06\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
20.91\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
7.90\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
28.81\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.59\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.29\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.30\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Stem\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.96\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.57\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.72\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.51\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.23\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.28\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
10.53\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.59\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N:P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
20.91\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
9.36\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
36.94\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.69\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
39.63\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.27\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.00\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.45\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
12.25\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.95\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
20.41\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.76\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
25.17\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.29\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.82\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.40\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Root\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.79\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.18\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.77\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.44\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.21\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.16\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.56\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.23\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N:P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
16.05\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
5.89\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
20.98\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
5.80\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
26.78\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.01\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.88\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.37\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
48.72\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
10.18\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
37.42\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
30.93\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
68.35\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.25\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.98\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.21\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
Whole\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.82\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.70\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
3.58\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
1.96\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
5.54\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
2.79\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
8.23\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.25\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
N:P\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
17.97\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
4.71\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
18.89\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
7.67\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
26.56\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.25\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
-0.40\strut
\end{minipage} & \begin{minipage}[t]{0.07\columnwidth}\raggedright\strut
0.26\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

The N content, P content and stoichiometric ratio of \emph{H.
ammodendron} leaves in the study area were analyzed by classical
statistics. The results are shown in Table 2. The variation range of N
content and P content in \emph{H. ammodendron} leaves were 10.10-30.29
mg/g, 0.54-1.63 mg/g, respectively. The average values were 19.80 mg/g
and 1.07 mg/g, respectively. By further analyzing the stoichiometric
ratio of N and P in leaves, it was found that the N:P ranged from 9.00
to 28.15, with an average of 18.97. The variation coefficients of N
content, P content and N:P in \emph{H. ammodendron} leaves were all
greater than 0.1, which were moderate variation.

The N content, P content and stoichiometric ratio of \emph{H.
ammodendron} stems in the study area were analyzed by classical
statistics. The results are shown in Table 2. The variation range of N
content and P content in \emph{H. ammodendron} stems were 7.90-28.81
mg/g, 0.51- 3.23 mg/g, respectively. The average values were 16.68 mg/g
and 0.96 mg/g, respectively. By further analyzing the stoichiometric
ratio of N and P in \emph{H. ammodendron} stems, it can be seen that the
range of N:P was 2.69-39.63, with an average of 20.91. The variation
coefficients of N content, P content and N:P in \emph{H.
ammodendron}stems were all greater than 0.1, which were moderate
variation.

The N content, P content and stoichiometric ratio of \emph{H.
ammodendron} roots in the study area were analyzed by classical
statistics. The results are shown in Table 2. The variation range of N
and P contents in \emph{H. ammodendron} roots were 4.76-25.17 mg/g and
0.44-1.21 mg/g, respectively. The average values were 12.25 mg/g and
0.79 mg/g, respectively. By further analyzing the N and P stoichiometry
of \emph{H. ammodendron} roots, it can be seen that the N:P ratio ranged
from 5.80 to 26.78, with an average of 16.05. The variation coefficients
of N content, P content and N:P in \emph{H. ammodendron} roots were all
greater than 0.1, which were moderate variation.

The N content, P content and stoichiometric ratio of each organ
of\emph{H. ammodendron} were analyzed by one-way anova and multiple
comparisons. The results are shown in Figure 1. There were differences
in N content, P content and their stoichiometric ratios in different
organs of \emph{H. ammodendron.}

N content and P content showed the trend of leaves \textgreater{} stems
\textgreater{} roots. The N content of leaves was significantly higher
than in stems and roots (\emph{p} \textgreater{}0.05), and the P content
was significantly higher than in roots (\emph{p} \textgreater{}0.05).
The N and P contents in stems were significantly higher than in root
(\emph{p} \textgreater{}0.05). The N:P of leaves and stems was
significantly higher than in roots (\emph{p} \textgreater{}0.05), and
the order was stems \textgreater{} leaves \textgreater{} roots.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Figure 1 Stoichiometric Characteristics of N and P in Different Organs
of \emph{H. ammodendron}

Note: Different capital letters indicate significant differences between
different organs of the same index(\emph{p\textless{}} 0.05)

3.1.2 Ecological stoichiometric characteristics of N and P in different
organs of \emph{H. ammodendron}

The N content, P content and stoichiometric ratio of different organs
of\emph{H. ammodendron} were analyzed by one-way anova and multiple
comparisons. The results are shown in Figure 2. There were differences
in N and P contents in different organs of \emph{H. ammodendron.}

The N content of \emph{H. ammodendron} in Kuitun, Karamay and Shihezi
showed a trend of leaves \textgreater{} stems \textgreater{} roots. The
N content of leaves was significantly higher than stems (\emph{p}
\textless{}0.05), and the N content of stems was significantly higher
than roots. There was no significant difference in N content in
different organs of \emph{H. ammodendron} in Fukang and Qitai (\emph{p}
\textgreater{}0.05). The N content in Fukang was stems \textgreater{}
leaves \textgreater{} roots, while that in Qitai was leaves
\textgreater{} stems \textgreater{} roots. The N content of leaves in
Karamay was significantly higher than in Fukang and Qitai (\emph{p}
\textless{}0.05). There was no significant difference in the N content
of \emph{H. ammodendron} stems among the 5 samples (\emph{p}
\textgreater{}0.05), and the N content of \emph{H. ammodendron}roots in
Qitai was significantly higher than in Karamay (\emph{p}
\textless{}0.05).

The P content of \emph{H. ammodendron} in Kuitun and Karamay showed
stems \textgreater{} leaves \textgreater{} roots, and the P content
of\emph{H. ammodendron} stems was significantly higher than that of
roots (\emph{p} \textgreater{}0.05). Qitai and Shihezi showed a trend of
leaves \textgreater{} root s\textgreater{} stems. The P content of each
organ of \emph{H. ammodendron} in Qitai was significantly different
(\emph{p\textless{}0.05} ), and the P content of leaves in Shihezi was
significantly higher than that of stems and roots (\emph{p}
\textless{}0.05). The P content of Fukang was leaves \textgreater{}
stems \textgreater{} roots, and the P content of leaves and stems was
significantly higher than that of roots (\emph{p\textless{}} 0.05). In
the 5 samples, the P content of leaves in Shihezi was significantly
higher than in Fukang, Karamay and Kuitun, and the P content of leaves
in Fukang and Karamay was significantly higher than in Kuitun (\emph{p}
\textless{}0.05).The P content in stems of kuitun was significantly
higher than in Qitai and Shihezi (\emph{p} \textless{}0.05). The P
content of \emph{H. ammodendron} roots in Qitai was significantly higher
than in Kuitun, Karamay and Fukang, and the P content of \emph{H.
ammodendron} roots in Shihezi was significantly higher than in Kuitun
(\emph{p} \textless{}0.05).

The N:P of \emph{H. ammodendron} in Qitai and Shihezi showed a trend of
stems \textgreater{} leaves \textgreater{} roots, and the N:P of stems
was significantly higher than that of leaves and roots (\emph{p}
\textless{}0.05). The N:P of leaves in Kuitun was significantly higher
than that of stems, and leaves \textgreater{} roots \textgreater{} stems
(\emph{p} \textless{}0.05), The N:P of leaves and stems in Karamay was
significantly higher than that of roots, and leaves \textgreater{} stems
\textgreater{} roots (\emph{p} \textless{}0.05). There was no
significant difference in N:P in different organs of\emph{H.
ammodendron} in Fukang, and stems \textgreater{} roots \textgreater{}
leaves (\emph{p} \textgreater{}0.05). Among the 5 samples, the N:P of
leaves in Kuitun and Karamay was significantly higher than in Fukang,
Qitai and Shihezi, and the N:P of stems in Qitai was significantly
higher than in the other 4 samples (\emph{p\textless{}0.05} ). There was
no significant difference in N:P of\emph{H. ammodendron} roots in 5
samples (\emph{p} \textgreater{}0.05).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

Figure 2 Ecological Stoichiometric Characteristics of N and P in
Different Organs of \emph{H. ammodendron}

Note: Different capital letters indicate that the difference between the
same organ is significant; different lowercase letters indicate
significant differences between different organs in the same
place(\emph{p\textless{}} 0.05)

3.2 Relationship between N, P stoichiometric characteristics of \emph{H.
ammodendron} and soil factors

3.2.1 Different soil factors

One-way anova analysis of variance and multiple comparisons were
performed on soil factors in different samples. The results are shown in
Table 3. There were significant differences in soil P content, N:P, pH
and electrical conductivity among different samples (\emph{p}
\textgreater{}0.05). The soil P content in Qitai was significantly
higher than in other samples (\emph{p} \textless{}0.05), Fukang soil N:P
was significantly higher than other samples (\emph{p} \textless{}0.05),
Karamay soil N:P was significantly higher than Kuitun, Qitai and Shihezi
(\emph{p} \textless{}0.05). The soil pH in Karamay and Qitai was
significantly higher than in other samples (\emph{p} \textless{}0.05).
The soil electrical conductivity of Qitai was significantly higher than
that of other samples, and that of Shihezi was significantly higher than
that of Kuitun, Karamay and Fukang (\emph{p} \textless{}0.05).

Table 3 One-way analysis of variance and multiple comparisons of soil
factors in different sample plots\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
Plot & Index & TN & TP & N:P & pH & EC\tabularnewline
Kuitun & Mean(mg/g) & 0.82\textsuperscript{a} & 0.46\textsuperscript{b}
& 1.80\textsuperscript{c} & 8.71\textsuperscript{b} &
0.96\textsuperscript{c}\tabularnewline
& SD & 0.57 & 0.32 & 0.50 & 0.53 & 0.54\tabularnewline
Karamay & Mean(mg/g) & 1.25\textsuperscript{a} & 0.51\textsuperscript{b}
& 3.54\textsuperscript{b} & 9.12\textsuperscript{a} &
0.50\textsuperscript{c}\tabularnewline
& SD & 1.43 & 0.39 & 2.45 & 0.08 & 0.41\tabularnewline
FuKang & Mean(mg/g) & 2.16\textsuperscript{a} & 0.42\textsuperscript{b}
& 5.19\textsuperscript{a} & 8.46\textsuperscript{b} &
0.85\textsuperscript{c}\tabularnewline
& SD & 2.56 & 0.49 & 2.12 & 0.19 & 0.43\tabularnewline
Qitai & Mean(mg/g) & 1.51\textsuperscript{a} & 3.11\textsuperscript{a} &
0.84\textsuperscript{c} & 9.1\textsuperscript{a} &
11.84\textsuperscript{a}\tabularnewline
& SD & 0.27 & 2.29 & 0.54 & 0.34 & 1.50\tabularnewline
Shi hezi & Mean(mg/g) & 2.10\textsuperscript{a} &
1.38\textsuperscript{b} & 1.55\textsuperscript{c} &
8.68\textsuperscript{b} & 4.45\textsuperscript{b}\tabularnewline
& SD & 0.56 & 0.46 & 0.11 & 0.13 & 6.38\tabularnewline
\bottomrule
\end{longtable}

Note: Different lowercase letters indicate significant differences
between different plots for the same soil factor(\emph{p\textless{}}
0.05)

3.2.2 Relationship between N, P ecological stoichiometry in different
organs of \emph{H. ammodendron} and soil factors

The correlation analysis of N content, P content and N:P with soil
factors in different organs is shown in Table 4. On the whole, the N
content, P content and N:P of each organ were only significantly
correlated with soil total nitrogen and total phosphorus (\emph{p}
\textless{}0.05), but not significantly correlated with soil N:P, pH and
conductivity (\emph{p} \textless{}0.05). The results showed that N
content of leaves and P content of roots were significantly positively
correlated with soil N content (\emph{p} \textless{}0.05), and N content
and N:P of stems were significantly positively correlated with soil N
content (\emph{p} \textless{}0.01). The P content of leaves and roots
was significantly positively correlated with soil P content (\emph{p}
\textless{}0.05), the P content of stems and the N content of roots were
significantly negatively correlated with soil P content
(p\textless{}0.05), and the N:P of roots was significantly negatively
correlated with soil P content (\emph{p} \textless{}0.01).The P content
of leaves was significantly negatively correlated with soil N:P
(\emph{p} \textless{}0.05), and the P content of roots was significantly
negatively correlated with soil N:P (\emph{p} \textless{}0.01).There was
no significant correlation between N:P of leaves and soil N content, P
content and N:P (\emph{p} \textless{}0.05). There was no significant
correlation between stem indexes and soil N:P and pH (\emph{p}
\textless{}0.05).There was no significant correlation between N content
in each organ and soil pH (\emph{p} \textless{}0.05). The N:P of leaves
was significantly negatively correlated with soil pH (\emph{p}
\textless{}0.01), and the P content of roots was significantly
positively correlated with soil pH (\emph{p} \textless{}0.05). The P
content of leaves was significantly positively correlated with soil
electrical conductivity (\emph{p} \textless{}0.05), N:P was
significantly negatively correlated with soil electrical conductivity
(\emph{p} \textless{} 0.01), and the N content of stems was
significantly negatively correlated with soil electrical conductivity
(\emph{p} \textless{} 0.05). There was no significant correlation
between root indexes and soil electrical conductivity (\emph{p}
\textless{}0.05).

Table 4 Pearson correlation analysis of N, P ecological stoichiometric
characteristics in different organs of \emph{H. ammodendron} and soil
factors\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
Organ & Index & TN & TP & N:P & pH & EC\tabularnewline
Leaf & N & 0.35* & 0.02 & -0.28 & -0.25 & -0.18\tabularnewline
& P & 0.17 & 0.36* & -0.30* & 0.23 & 0.34*\tabularnewline
& N:P & 0.16 & -0.26 & -0.02 & -0.37** & -0.41**\tabularnewline
Stem & N & 0.78** & 0.08 & 0.03 & -0.04 & -0.32*\tabularnewline
& P & -0.23 & -0.29* & 0.02 & -0.09 & -0.05\tabularnewline
& N:P & 0.51** & 0.26 & -0.14 & 0.11 & -0.27\tabularnewline
Root & N & 0.05 & -0.35* & -0.09 & 0.03 & -0.03\tabularnewline
& P & 0.30* & 0.28* & -0.41** & 0.41** & 0.07\tabularnewline
& N:P & -0.17 & -0.56** & 0.17 & -0.26 & -0.07\tabularnewline
\bottomrule
\end{longtable}

Note: *,\emph{p\textless{}} 0.05;**,\emph{p} <0.01\begin{CJK}{UTF8}{gbsn}。

\end{CJK}\selectlanguage{english}3.3 Effects of samples and organs on the ecological stoichiometric
characteristics of N and P in \emph{H. ammodendron}

Through general linear model analysis, the effects of samples and organs
on the ecological stoichiometric characteristics of N and P in \emph{H.
ammodendron} were quantified. The results are shown in Table 5. The
effect of organs on the N content, P content and N:P of \emph{H.
ammodendron} was significant (\emph{p} \textless{}0.01), and the samples
only had significant effect on N:P (\emph{p\textless{}} 0.05). The
interaction between samples and organs had significant effects on N
content (\emph{p\textless{}} 0.05), and extremely significant effects on
P content and N:P (\emph{p} \textless{}0.01).

Table 5 General Linear Model Analysis of Effects of Organs and Sampling
Areas on N and P Ecological Stoichiometry of \emph{H. ammodendron}\selectlanguage{english}
\begin{longtable}[]{@{}lllllll@{}}
\toprule
Independent variable & Dependent variable & Quadratic sum & Freedom &
Mean square & Statistic & Significance\tabularnewline
Site & N & 92.82 & 4.00 & 23.21 & 1.07 & 0.37\tabularnewline
& P & 0.19 & 4.00 & 0.05 & 0.43 & 0.79\tabularnewline
& N:P & 395.37 & 4.00 & 98.84 & 2.70 & 0.03*\tabularnewline
Organ & N & 1437.40 & 2.00 & 718.70 & 33.17 & 0.00**\tabularnewline
& P & 2.05 & 2.00 & 1.02 & 8.99 & 0.00**\tabularnewline
& N:P & 599.80 & 2.00 & 299.90 & 8.19 & 0.00**\tabularnewline
Sitet\selectlanguage{ngerman}×Organ & N & 385.78 & 8.00 & 48.22 & 2.23 & 0.03*\tabularnewline
& P & 4.15 & 8.00 & 0.52 & 4.56 & 0.00**\tabularnewline
& N:P & 1799.08 & 8.00 & 224.89 & 6.14 & 0.00**\tabularnewline
\bottomrule
\end{longtable}

Note: *,\emph{p\textless{}0.05} ;**,\emph{p} <0.01\begin{CJK}{UTF8}{gbsn}。

\end{CJK}\selectlanguage{english}\textbf{4.Discussion}

4.1 Changes of N and P stoichiometric characteristics in different
organs of

\emph{H. ammodendron}

The average content of N and P in the leaves of \emph{H. ammodendron} in
the study area (19.80 mg/g, 1.07 mg/g) was lower than the average level
of N and P in the leaves of terrestrial plants (20.60 mg/g, 1.99 mg/g)
(Tan et al., 2021), and the average level of N and P in the leaves of
terrestrial plants in China (20.20 mg/g, 1.46 mg/g) (Ding \& Cong,
2021), indicating that the nutrient content of \emph{H.
ammodendron}leaves in this area is low. Leaves are organs for
photosynthesis to produce organic matter. \emph{H. ammodendron} grows
rapidly in summer, requiring leaves to produce more organic matter to
meet the needs of plant growth. Therefore, the absorption of N and P in
leaves increased and the accumulation of N and P in leaves was generally
higher than in stems and roots (Han et al., 2005; Wei, 2000; Elser et
al., 2000). The metabolic activity of stems was stronger than that of
roots, so the N and P contents of stems were lower than those of leaves,
but higher than those of roots (Makino et al., 2003). The metabolic
level of roots is low, and the absorbed nutrients are also supplied to
other organs and parts while maintaining their own growth, so the N
content and P content in roots are the lowest. N:P is closely related to
plant growth rate and soil resource availability (Xiao et al., 2014;
Makino et al., 2003; Qian et al., 2002). The precipitation in the study
area is scarce, the soil is barren, and plants need to absorb water and
nutrients from deep soil (Paige \& Michaeleen, 2020; Sun et al., 2020;
Chen et al., 2016). Plant N:P can be used to determine the nutrient
supply of plant growth by the environment (Chen et al., 2016; Lv et al.,
2015), N:P<14,plant growth is mainly limited by N ; N:P>16,Plant
growth is mainly limited by P (Han et al., 2005; Elser et al., 2000).
The N:P of \emph{H. ammodendron}plants and organs in the study area was
higher than 16, indicating that\emph{H. ammodendron} in the study area
was more limited by P than N (Nie et al., 2022; Li et al., 2019). In
this study, the N:P in leaves and stems of \emph{H. ammodendron} was
significantly higher than in roots, which may be resulted from the
higher utilization efficiency of N and P in aboveground parts (Kerkhoff
et al., 2006).

4.2 The relationship between N, P stoichiometric characteristics of
\emph{H. ammodendron} organs and soil factors

Soil total nitrogen was significantly positively correlated with the N
content of \emph{H. ammodendron} leaves and extremely significantly
positively correlated with the N content of stems, indicating that the N
of \emph{H. ammodendron} leaves and stems mainly came from soil total
nitrogen. The growth and metabolism of these two organs were greatly
affected by soil N , and the change of soil nutrient content had a
greater impact on stems (Hogberg et al., 2006). Soil total phosphorus
was significantly positively correlated with P content in leaves and
roots of \emph{H. ammodendron} , negatively correlated with P content in
stems, indicating that soil P limited the growth of leaves and roots.
Except for the P content in leaves and roots of \emph{H. ammodendron} ,
there was no significant correlation between soil N:P and N, P
ecological stoichiometry in different organs of \emph{H. ammodendron} ,
indicating that soil nutrient stoichiometry had little direct effect on
the organs of \emph{H. ammodendron} , which may be due to the fact
that\emph{H. ammodendron} was limited by both water and nutrient
elements, and formed unique ecological stoichiometry and physiological
and ecological habits after long-term evolution (Liu \& Wang, 2020).
Soil pH affects the solubility of mineral salts, which in turn affects
the effectiveness of soil nutrients (Bell et al., 2014). The soil in the
study area is alkaline, which affects the release of N and P. Therefore,
soil pH is generally negatively correlated with different indicators of
various organs of \emph{H. ammodendron} . Soil electrical conductivity
reflects the salt content in soil (Bell et al., 2014; Matzek \&
Vitousek, 2009; Reich et al., 2009; Craine et al., 2008). When the soil
salt content is high, the soil osmotic pressure increases, and it is
more difficult for roots to absorb water and salt. Therefore, soil
electrical conductivity is generally negatively correlated with N and P
stoichiometric characteristics of leaves, stems and roots. The above
showed that the ecological stoichiometric characteristics of N and P
in\emph{H. ammodendron} were affected by organs and soil factors.

4.3 Effects of samples and organs on ecological stoichiometric
characteristics of N and P in \emph{H. ammodendron}

In this study, the ecological stoichiometric characteristics of N and P
in \emph{H. ammodendron} were mainly affected by organs and the
interaction between samples and organs. Samples only had a significant
effect on N:P content of \emph{H. ammodendron} . The effects of sampling
sites on the ecological stoichiometric characteristics of N and P
in\emph{H. ammodendron} may be related to external environmental
factors, such as topography and soil (Abbas et al., 2013; Agren \& Weih,
2012; Sardans et al., 2012; Cuassolo et al., 2012). The effects of
organs on the ecological stoichiometric characteristics of N and P in
\emph{H. ammodendron} may be related to its own structural
characteristics and genetic characteristics. Studies have shown that
plants respond to changing environments by regulating the nutrient
content and proportion of each organ (Sun et al., 2020). Therefore, the
effect of organs on N content, P content and N:P of \emph{H.
ammodendron} was significant, but the effect of samples on N:P was also
significant, which indicated that the ecological stoichiometric
characteristics of N and P of \emph{H. ammodendron} in this study were
affected by the single factor of samples and organs and the interaction
of two factors.

\textbf{5.Conclusion and prospect}

5.1 Conclusions

In this paper, \emph{H. ammodendron} in five areas of Gurbantunggut
Desert was selected as the research object. Combined with mathematical
statistics method, the N content, P content and N:P characteristics
of\emph{H. ammodendron} leaves, stems and roots were calculated and
compared. The relationship between N, P ecological stoichiometry
characteristics of \emph{H. ammodendron} organs and soil factors was
analyzed. It was found that the differences of N, P content and N:P in
different organs of \emph{H. ammodendron} were significant, and the
trend of each index was roughly the same. The overall trend was that the
leaves were relatively high, followed by the stems, and the roots was
generally low. The N content of each organ of \emph{H. ammodendron} was
significantly positively correlated with soil total nitrogen. The P
content of leaves and roots was significantly positively correlated with
soil total phosphorus, and the P content of stems was significantly
negatively correlated with soil total phosphorus. P content in different
organs was negatively correlated with soil N:P. The N content, P content
and N:P in different organs generally showed a certain negative
correlation with soil pH and electrical conductivity, and the organs had
a greater impact on the N content, P content and N:P of \emph{H.
ammodendron.}

5.2 Limitations and prospects

The time period of this study is short, and only the \emph{H.
ammodendron} in the southern margin of the Gurbantunggut Desert was
studied. The spatial and temporal distribution of the overall ecological
stoichiometric characteristics of desert plants in the region was not
studied in depth. The research on the ecological stoichiometric
characteristics of various elements in various organs of desert plants
can reveal the distribution characteristics of ecological stoichiometric
characteristics of desert plants and the adaptability of desert plants
to the environment in more detail, and the follow-up work needs to be
further refined. In addition, this study only combines some soil factors
( soil N, P content, pH, conductivity ). In the later study, more
environmental factors ( such as annual rainfall and annual average
temperature ) need to be combined.

\textbf{Author Contributions:} C.L. and K.D carried out the fieldwork
and wrote the first draft of the manuscript. Y.L. carried out the
fieldwork and assisted with revising the draft manuscript. D.P. carried
out the fieldwork, Y.G. assisted with revising the draft manuscript. All
authors contributed to the article and approved the submitted version.
All authors have read and agreed to the published version of the
manuscript.

\textbf{Funding:} Third Xinjiang Scientific Expedition Program (Grant
No. 2022xjkk040301), China Postdoctoral Science Foundation (No.
2022M722667) and Department of Education of Xinjiang Uygur Au-tonomous
Region, Dr. Tianchi Program Project (No. TCBS202123).

\textbf{Conflicts of Interest:} The authors declare that the research
was conducted in the absence of any commercial or financial
relationships that could be construed as a potential conflict of
interest.

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