Elsevier

Ecological Engineering

Volume 60, November 2013, Pages 116-125
Ecological Engineering

The effects of short-term rainfall variability on leaf isotopic traits of desert plants in sand-binding ecosystems

https://doi.org/10.1016/j.ecoleng.2013.07.022Get rights and content

Highlights

  • We examined succession effects on water–nutrient interactions of sand-binding species.

  • We also examined short-term rainfall and seasonality effects of the same species.

  • We found species dependent strategies to adapt to the harsh environments.

  • These sand-binding plants developed into stable stage but short-term climate variability has severe impact on their function.

  • These results provide important clues on how these sand-binding plants potentially respond to climate change.

Abstract

Sand-binding vegetation is effective in stabilizing sand dunes and reducing soil erosion, thus helps minimize the detrimental effects of desertification. The aim of this study is to better understand the relationships between water and nutrient usage of sand-binding species, and the effects of succession and rainfall variability on plants’ water–nutrient interactions. We examined the effects of long-term succession (50 years), inter-annual rainfall variability (from 65% of the mean annual precipitation in 2004 to 42% in 2005) and seasonality on water–nutrient interactions of three major sand-binding species (Artemisia ordosica, Hedysarum scoparium and Caragana korshinskii) by measuring foliar δ13C, δ15N and [N]. Long-term succession in general did not significantly alter δ13C, δ15N and [N] of the three species. Short-term rainfall variability, however, significantly increased foliar δ13C levels of all three species by 1.0–1.8‰ during the severely dry year. No significant seasonal patterns were found in foliar δ13C and δ15N values of the three species, whereas foliar [N] varied by season. For the two leguminous shrubs, the correlations between δ13C and δ15N were positive in both sampling years, and the positive correlation between [N] and δ13C was only found in the severely dry year. The results indicate that these sand-binding plants have developed into a relatively stable stage and they are able to regulate their nitrogen and water use in responding to environmental conditions, which reinforces the effectiveness of plantation of native shrubs without irrigation in degraded areas. However, the results also indicate that short-term climate variability could have severe impact on the vegetation functions.

Introduction

Desertification is one of the major environmental problems worldwide (Reynolds et al., 2007) and it occurs in almost every habitable region such as North America (e.g., Schlesinger et al., 1990, Li et al., 2008, Ravi et al., 2009), Africa (e.g., Thomas et al., 2008, Wang et al., 2010a) and northern China (e.g., Chen et al., 1996, Mitchell et al., 1998, Liu et al., 2012). The deserts in northern China are expanding at an estimated rate of 2100 km2 year−1 (Chen et al., 1996, Mitchell et al., 1998).

Revegetation of native shrubs, a massive ecological engineering project (Mitsch et al., 1993), has been one of the most effective methods to reduce desertification. Large areas of China's desert regions have been reclaimed through planting of native plants since the 1950s (Shapotou Desert Research and Experiment Station, 1986). For example, the 1000-km long Baotou-Lanzhou railway that passes through Shapotou region has been protected by sand-binding shrubs that were planted in 1956, 1964, 1981 and 1987, respectively (Shapotou Desert Research and Experiment Station, 1986). The success of these efforts suggests that it is an effective approach to control desertification and to restore the ecological environment along transportation corridors in the desert regions of China (Xiao et al., 2003a, Li et al., 2006). Many revegetated species, such as Caragana intermedia, Calligonum arborescens and Tamarix ramosissima, disappeared over the years, whereas some native species such as Artemisia ordosica, Hedysarum scoparium and Caragana korshinskii survived during succession and have become the dominant shrubs (Ma et al., 2002). As a result of long-term succession, the planted vegetation ecosystem is expected to develop into a stable system (Xiao et al., 2003b). The effects of long-term succession and short-term climate variability (e.g., rainfall) on the function of these successful sand-binding species (e.g., A. ordosica, H. scoparium, and C. korshinskii) are not yet fully understood, which hinders our ability to predict future successional pathways of such planted ecosystems under the circumstances of potential warming and drought in this region (Solomon et al., 2007).

In this study, we measured dual isotope (13C and 15N) compositions and nitrogen concentrations ([N]) of three dominant species, i.e., A. ordosica, H. scoparium, and C. korshinskii, and analyzed their interactions to investigate the effects of long-term succession (50 years) and short-term drought (2 years) on plant uptake of water and nitrogen at a desert stabilized by sand-binding plants in northern China. Besides providing valuable isotopic information of these sand-binding species, this study will have both theoretical and applied importance in the restoration of degraded ecosystems and in improving our ability to predict the response of planted sand-binding vegetation to climate change.

Stable isotopes are used in the investigation because they provide integrated information on plant water and nutrient use and serve as powerful tracers in ecosystem studies. The stable carbon isotope ratio (δ13C) of plant tissues reflects the relations between plant carbon and soil water. The effect of water availability on carbon isotope discrimination during photosynthesis of C3 plant is relatively well understood (e.g., Farquhar et al., 1982). For example, photosynthesis depends on water availability, and low water availability can decrease the assimilation of carbon, thereby reducing plant productivity and the corresponding nitrogen requirements or assimilation rates, leading to different patterns of δ13C and δ15N variation (Yoneyama et al., 2001). Foliar δ13C typically increases when water availability is low, as a result of stomatal closure and reduced transpiration (Peuke et al., 2006). And foliar δ13C is higher in the water-limited treatment relative to the well-watered treatment (Grant et al., 2012). Analyses of δ13C have greatly increased our understanding of the relationships between water and carbon use by desert plants (Ehleringer, 1993). Nitrogen isotope ratio (δ15N) provides information on ecosystem nitrogen cycling (Högberg et al., 1995, Roggy et al., 1999, Ometto et al., 2006, Bai et al., 2009) and plant nitrogen isotope discrimination is related to the availability of nutrients and water (Högberg, 1997, Swap et al., 2004, Aranibar et al., 2008, Wang et al., 2010b). Previous studies showed that succession affected N cycling and it was reflected in foliar δ15N (Davidson et al., 2007, Wang et al., 2007), and foliar δ15N signatures decreased as successional age increased at both the plant community and species levels (Wang et al., 2007).

Plant δ13C and δ15N signatures are often regulated by two or more factors (BassiriRad et al., 2003, Murphy and Bowman, 2009). For example, Schulze et al. (1991) point out that the significant correlation between δ15N and δ13C values of nitrogen-fixing African trees is caused by decreased water use efficiency, compared with that of the non-nitrogen-fixers. The decreased water use efficiency in nitrogen fixer usually is a result of the extra cost of carbohydrate supply to the nitrogen-fixing diazotroph (Farquhar and Richards, 1984).

Previous research also shows that photosynthetic capacity is strongly correlated with C3 plant foliar [N] because photosynthetic enzymes, such as RuBP carboxylase, contain large amounts of nitrogen (Reich et al., 1998, Tognetti and Penuelas, 2003). It is also found that higher photosynthetic activity leads to enriched foliar δ13C values (O’Leary, 1981). Because of these two reasons, positive correlations between foliar δ13C and [N] have been found in many cases (e.g., Sparks and Ehleringer, 1997, Wang et al., 2008). Such relationships together with the positive correlation between foliar δ15N and [N] in non-nitrogen-fixing plants (Hobbie et al., 2000, Wang et al., 2007) suggest that foliar δ13C, δ15N, and [N] levels are closely linked.

This study is to investigate the interactions of plant nitrogen and water use in planted sand-binding vegetation after long-term succession and to test whether there are functional group (potential nitrogen-fixer and non nitrogen-fixer) dependent adaptation strategies to water and nitrogen variations in the harsh environments. Specifically, the objectives of this study are to investigate (1) the long-term effect (up to 50 years) of successional age on the isotopic signatures (δ13C and δ15N) and [N] of three dominant shrubs in planted sand-binding vegetation communities; (2) the effects of seasonality and short-term drought on variations in isotopic signatures and [N] of each species; and (3) the relationships between δ13C, δ15N, and [N] of the three shrub species. The results will provide important implications on how plant species adapt to harsh environments in terms of water use efficiency and nutrient use during succession and how plant species respond to environmental changes.

Section snippets

Study area

Shapotou region is located at the southeastern border of the Tengger Desert in China (Fig. 1). The region receives high solar radiation and is low in relative humidity. Average annual precipitation is 180.2 mm, with 80% of the rainfall occurring from May to September. The mean annual temperature is 10.0 °C, with a mean January temperature of −6.9 °C and a mean July temperature of 24.3 °C. The water table is more than 80 m below ground, thus rainfall is usually the only source of water for plants.

The

Foliar δ15N, δ13C, and [N] of each species

Foliar δ15N values of A. ordosica, H. scoparium, and C. korshinskii differed significantly (p < 0.05), with the most negative value in A. ordosica (−3.1 ± 0.1‰ (mean ± SE)) and the most positive value in C. korshinskii (−1.5 ± 0.1‰) (Table 3). Foliar δ13C values of A. ordosica (−24.4 ± 0.1‰) and H. scoparium (−24.5 ± 0.1‰) did not show significant difference, but both values were significantly more negative than that of C. korshinskii (−23.2 ± 0.1‰, p < 0.05) (Table 3). Foliar [N] of C. korshinskii (16.1 ± 0.98 g 

Variations in three plant species

Foliar δ13C is an indicator of long-term plant water use efficiency (Farquhar et al., 1989). Our results showed that the δ13C values (ranging from −21.1 to −26.6‰) of the dominant shrubs in the Tengger Desert (a cold desert) were more positive than the values reported for other desert C3 plants, which ranged from −21.0 to −28.0‰ in the northern Namaqualand Desert of South Africa (Rundel et al., 1999), from −22.0 to −29.0‰ in the Arizona deserts of the United States (Ehleringer and Cooper, 1988)

Summary

To better understand the long-term succession and short-term climate variability effects on the functions of three major sand-binding species (A. ordosica, H. scoparium and C. korshinskii), we examined the effects of succession, rainfall variability, and seasonality on foliar δ13C, δ15N and [N]. The study has both theoretical and applied importance in the restoration of degraded lands and in improving our ability to predict the response of planted sand-binding vegetation to climate change. The

Acknowledgments

This research was supported by the National Natural Science Foundation of China (91125025, 91025016), the National Science & Technology Pillar Program during the Twelfth Five-Year Plan Period (2011BAC07B05), and the Ministry of Forestry Welfare Special Project (201004010-05).

References (70)

  • M.H. O’Leary

    Carbon isotope fractionation in plants

    Phytochemistry

    (1981)
  • A.D. Thomas et al.

    Carbon dioxide fluxes from cyanobacteria crusted soils in the Kalahari

    Appl. Soil Ecol.

    (2008)
  • L. Wang et al.

    Patterns and implications of plant–soil δ13C and δ15N values in African savanna ecosystems

    Quater. Res.

    (2010)
  • E. Bai et al.

    Spatial variation of the stable nitrogen isotope ratio of woody plants along a topoedaphic gradient in a subtropical savanna

    Oecologia

    (2009)
  • H. BassiriRad et al.

    Widespread foliage δ15N depletion under elevated CO2: inferences for the nitrogen cycle

    Global Change Biol.

    (2003)
  • J. Bremner et al.

    Nitrogen-total

  • G. Chen et al.

    Desertification: international research topics and research strategies of China

    Explor. Nat.

    (1996)
  • E.A. Davidson et al.

    Recuperation of nitrogen cycling in Amazonian forests following agricultural abandonment

    Nature

    (2007)
  • T.E. Dawson et al.

    Stable isotope in plant ecology

    Annu. Rev. Ecol. Syst.

    (2002)
  • E. De Martonne

    Une nouvelle fonction climatologique: L’indice d’aridité

    La Meteorologie

    (1926)
  • Z. Duan et al.

    Abiotic soil crust formation on dunes in an extremely arid environment: a 43-year sequential study

    Arid Land Res. Manage.

    (2003)
  • J. Ehleringer et al.

    Correlations between carbon isotope ratio and microhabitat in desert plants

    Oecologia

    (1988)
  • J. Evans

    Photosynthesis and nitrogen relationships in leaves of C3 plants

    Oecologia

    (1989)
  • G. Farquhar et al.

    Carbon isotope discrimination and photosynthesis

    Ann. Rev. Plant Physiol. Mol. Biol.

    (1989)
  • G. Farquhar et al.

    Isotopic composition of plant carbon correlated with water use efficiency of wheat genotypes

    Aust. J. Plant Physiol.

    (1984)
  • G.D. Farquhar et al.

    On the relationship between carbon isotope discrimination and the intercellular carbon dioxide concentration in leaves

    Aust. J. Plant Physiol.

    (1982)
  • C. Field et al.

    The photosynthesis–nitrogen relationship in wild plants

  • C. Garten et al.

    Relationships between soil nitrogen dynamics and natural 15N abundance in plant foliage from Great Smoky Mountains National Park

    Can. J. For. Res.

    (1994)
  • C.T. Garten

    Variation in foliar 15N abundance and the availability of soil nitrogen on walker branch watershed

    Ecology

    (1993)
  • E.A. Hobbie et al.

    Correlations between foliar d15N and nitrogen concentrations may indicate plant–mycorrhizal interactions

    Oecologia

    (2000)
  • P. Högberg

    15N natural abundance in soil–plant systems

    New Phytol.

    (1997)
  • P. Hogberg et al.

    Role of root symbioses in African woodland and forest: evidence from 15N abundance and foliar analysis

    J. Ecol.

    (1995)
  • P. Högberg et al.

    Measurements of abundances of 15N and 13C as tool in retrospective studies of N balances and water stress in forests: a discussion of preliminary results

    Plant Soil

    (1995)
  • C. Johannisson et al.

    15N abundance of soils and plants along an experimentally induced forest nitrogen supply gradient

    Oecologia

    (1994)
  • J. Li et al.

    Effects of wind erosion on the spatial heterogeneity of soil nutrients in two desert grassland communities

    Biogeochemistry

    (2008)
  • Cited by (11)

    • Latitudinal and climate effects on key plant traits in Chinese forest ecosystems

      2019, Global Ecology and Conservation
      Citation Excerpt :

      Long-term climate variables did not significantly alter d13C and N levels of the plants. Short-term rainfall variability, however, significantly increased foliar d13C of the plants, indicating higher water use efficiency during a more severe drought (Farquhar et al., 1982; Zhao et al., 2013). The results indicate that short-term climate variables significantly affects the plant functions.

    • Variation of carbon use efficiency over ten years in a subtropical coniferous plantation in southeast China

      2016, Ecological Engineering
      Citation Excerpt :

      As the main water supply, precipitation amount not only influenced GEP, NEP, and ecosystem respiration (RE) in Northern Hemisphere forests (Chen et al., 2015), but also influenced GEP and RE in a boreal aspen forest (Barr et al., 2007), through its effect on soil water content. In addition, due to the effects of soil water holding capacity (Rambal and Debussche, 1995), precipitation distribution (Zhao et al., 2013), and vegetation canopy condition (Wang et al., 2011), precipitation characteristics such as frequency (Wang et al., 2011) and timing (Harper et al., 2005), rather than precipitation amount influence ecosystem carbon fluxes. Moreover, seasonal drought caused by asynchrony between precipitation and temperature, influences forest GEP, NEP, and RE in a non-linear fashion due to plant physiological adjustment (Noormets et al., 2008; Ross et al., 2012), and the seasonal variation of CUE may be diverse.

    • δ<sup>13</sup>C values of plants as indicators of soil water content in modern ecosystems of the Chinese Loess Plateau

      2015, Ecological Engineering
      Citation Excerpt :

      The answer is yes because the δ13CAP and δ13CBP values of the individual species all exhibited a tendency to gradual decrease with vegetation restoration (except for S. japonica). For the genus Artemisia, Zhao et al. (2013) found that in general, long-term succession did not significantly alter the δ13C of Artemisia ordoica, but the δ13C of A. scoparis decreased significantly with restoration time in this study. The lack of change observed in the prior study is most likely attributed to the lack of meaningful change in soil water content, which decreased from 2.03% to 1.16% along that chronosequence of succession.

    View all citing articles on Scopus
    View full text