Seed dispersal and germination were examined for 70 species from the cold Gurbantunggut Desert in northwest China. Mean and range (3 orders of magnitude) of seed mass were smaller and narrower than those in other floras (5–8 orders of magnitude), which implies that selection favors relatively smaller seeds in this desert. We identified five dispersal syndromes (anemochory, zoochory, autochory, barochory, and ombrohydrochory), and anemochorous species were most abundant. Seed mass (
Each desert plant species has its own complex life history strategy that enables it to persist in its arid habitat. These strategies include seed dispersal and germination [
Seed germination and dormancy are pivotal events in seedling establishment, and they are closely related to seed dispersal and population generation. Some researchers consider seed dormancy as an adaptive bet-hedging strategy in spatiotemporally varying environments [
The Gurbantunggut Desert is located in the center of the Junggar Basin, Xinjiang Province, China, and it is the second largest desert in China with an area of 48,800 km2. In this area, there are 208 species of seed plants that belong to 30 families and 123 genera. Dominant families are Amaranthaceae, Asteraceae, Brassicaceae, Fabaceae, Poaceae, Polygonaceae, Tamaricaceae, and Zygophyllaceae and they contain 74% of all species in the Gurbantunggut Desert [
Information on seed dispersal and seed germination of desert plants is crucial to understanding adaptative strategies of plants in these arid areas. For the Gurbantunggut Desert, we asked the following questions. (1) Do escape and protection dispersal strategies exist? If they do, what is the proportion of each dispersal strategy? (2) Are seed traits related to seed dispersal sydromes, that is, what is the relationship between dispersal strategies and dispersal syndromes? (3) Do cautious and opportunistic germination strategies exsit? If they do, what is the proportion of each germination strategy, that is, what is the relationship between dispersal strategies and germination strategies? To answer these questions, we observed and measured seed structure, seed mass, seed size, seed shape to determine dispersal strategies, and syndromes and conducted seed germination experiments.
Because of the rain shadow from the Himalayan and Tian Shan ranges, moist air currents from the Indian Ocean do not reach the Gurbantunggut, resulting in a vast arid expanse. Mean annual precipitation is approximately 80 mm, falling predominantly during spring. Mean potential annual evaporation is >2600 mm. The mean annual temperature is 7.3°C. Wind speeds are highest in late spring (mean
Family, species, vegetative period, month of seed collection, seed traits (seed mass, seed size, seed shape), seed germination percentage, dispersal syndromes and dispersal strategies recorded for each of the 70 study species.
Family | Species | Life form | Collecting time (months) | Seed mass (mg) | Seed size (mm) | Seed shape (variance) | Seed germination percentage (%) | Dispersal syndromes | Dispersal |
---|---|---|---|---|---|---|---|---|---|
Ephedraceae |
|
LS | 9 | 2.81 ± 0.071 | 3.926 ± 0.054 | 0.144 | 0 | Anemochory | Escape-protection |
|
|||||||||
Poaceae |
|
E | 8 | 0.076 ± 0.0024 | 0.584 ± 0.021 | 0.028 | 5.5 ± 2.22 | Anemochory | escape |
|
E | 6 | 1.78 ± 0.046 | 11.389 ± 0.792 | 0.184 | 87.33 ± 2.40 | Epizoochory | Protection | |
|
LPH | 8 | 7.85 ± 0.68 | 9.534 ± 0.775 | 0.178 | 0.5 ± 0.5 | Epizoochory | Protection | |
|
LP | 8 | 9.44 ± 0.14 | 13.708 ± 0.872 | 0.156 | 47 ± 2.08 | Epizoochory | Protection | |
|
|||||||||
Papaveraceae |
|
LBP | 6 | 0.42 ± 0.0018 | 1.269 ± 0.044 | 0.065 | 30 ± 5.29 | Autochory | Escape |
|
|||||||||
Ranunculaceae |
|
E | 6 | 1.06 ± 0.0099 | 4.614 ± 0.229 | 0.018 | 20.67 ± 1.76 | Epizoochory | Escape-protection |
|
|||||||||
Caryophyllaceae |
|
LA | 9 | 0.20 ± 0.0087 | 0.499 ± 0.011 | 0.028 | 0 | Barochory | Escape |
|
|||||||||
Amaranthaceae |
|
LA | 9 | 1.16 ± 0.027 | 2.208 ± 0.093 | 0.108 | 8.5 ± 2.22 | Barochory | Protection |
|
LA | 9 | 0.70 ± 0.0046 | 2.083 ± 0.058 | 0.069 | 14.5 ± 5.50 | Barochory | Escape | |
|
LA | 10 | 0.68 ± 0.0088 | 2.115 ± 0.034 | 0.066 | 56 ± 2.00 | Barochory | Escape | |
|
LS | 10 | 1.14 ± 0.020 | 2.064 ± 0.062 | 0.104 | 66.5 ± 4.03 | Anemochory | Protection | |
|
LA | 10 | 1.10 ± 0.032 | 4.472 ± 0.355 | 0.168 | 11 ± 4.65 | Anemochory | Escape-protection | |
|
LA | 9 | 0.66 ± 0.0078 | 3.018 ± 0.145 | 0.15 | 15 ± 1.91 | Epizoochory | Protection | |
|
LA | 10 | 0.43 ± 0.0049 | 2.958 ± 0.165 | 0.04 | 85.5 ± 4.27 | Epizoochory | Protection | |
|
LS | 10 | 0.54 ± 0.015 | 2.238 ± 0.066 | 0.083 | 96 ± 5.48 | Anemochory | Escape | |
|
LA | 9 | 1.51 ± 0.025 | 7.624 ± 0.556 | 0.364 | 42.5 ± 2.36 | Epizoochory | Escape-protection | |
|
LA | 7 | 0.35 ± 0.0017 | 0.964 ± 0.025 | 0.078 | 98.5 ± 0.96 | Barochory | Escape | |
|
LA | 8 | 0.11 ± 0.0022 | 0.594 ± 0.023 | 0.037 | 6.5 ± 0.96 | Barochory | Escape | |
|
LA | 9 | 0.22 ± 0.0021 | 0.864 ± 0.049 | 0.074 | 99 ± 0.58 | Barochory | Escape | |
|
LA | 10 | 0.35 ± 0.0016 | 1.776 ± 0.086 | 0.044 | 7.5 ± 2.22 | Barochory | Escape | |
|
LA | 8 | 0.73 ± 0.01 | 2.634 ± 0.083 | 0.143 | 0 | Epizoochory | Escape | |
|
LA | 10 | 1.06 ± 0.011 | 2.092 ± 0.047 | 0.088 | 77.00 ± 2.34 | Anemochory | Escape-protection | |
|
LS | 10 | 0.24 ± 0.0074 | 1.798 ± 0.077 | 0.046 | 69 ± 3.00 | Anemochory | Escape | |
|
LS | 10 | 3.89 ± 0.12 | 10.676 ± 0.419 | 0.172 | 73.5 ± 5.74 | Anemochory | Protection | |
|
LS | 10 | 7.97 ± 0.085 | 9.528 ± 0.149 | 0.147 | 54 ± 4.55 | Anemochory | Protection | |
|
LA | 9 | 0.23 ± 0.0057 | 0.932 ± 0.043 | 0.083 | 4 ± 1.41 | Epizoochory | Escape | |
|
LS | 10 | 0.15 ± 0.002 | 1.568 ± 0.080 | 0.032 | 96.5 ± 1.71 | Anemochory | Escape | |
|
LS | 10 | 0.16 ± 0.0065 | 3.712 ± 0.213 | 0.047 | 98.00 ± 0.77 | Anemochory | Escape | |
|
LA | 10 | 0.47 ± 0.008 | 0.698 ± 0.017 | 0.104 | 68 ± 2.45 | Anemochory | Escape | |
|
LA | 9 | 1.75 ± 0.015 | 0.728 ± 0.029 | 0.129 | 3 ± 1.29 | Anemochory | Escape-protection | |
|
LA | 10 | 0.055 ± 0.0004 | 1.270 ± 0.121 | 0.047 | 15 ± 3.87 | Anemochory | Escape | |
|
LA | 10 | 1.04 ± 0.004 | 6.162 ± 0.218 | 0.182 | 0 | Anemochory | Escape-protection | |
|
LA | 10 | 5.18 ± 0.069 | 10.176 ± 0.596 | 0.139 | 26 ± 8.21 | Anemochory | Escape-protection | |
|
LA | 10 | 2.68 ± 0.053 | 8.312 ± 0.537 | 0.139 | 24 ± 9.42 | Anemochory | Escape-protection | |
|
LA | 10 | 1.80 ± 0.040 | 6.690 ± 0.269 | 0.115 | 43.5 ± 3.30 | Anemochory | Escape-protection | |
|
LA | 10 | 2.71 ± 0.041 | 8.216 ± 0.424 | 0.129 | 3 ± 1.29 | Anemochory | Escape-protection | |
|
LA | 9 | 0.57 ± 0.017 | 1.463 ± 0.088 | 0.02 | 38.5 ± 1.89 | Barochory | Escape | |
|
LA | 10 | 0.35 ± 0.0057 | 1.244 ± 0.033 | 0.029 | 24 ± 2.83 | Barochory | Escape | |
|
LS | 10 | 0.32 ± 0.0051 | 1.086 ± 0.040 | 0.003 | 52.5 ± 5.62 | Barochory | Escape | |
|
LS | 10 | 2.48 ± 0.021 | 2.934 ± 0.162 | 0.029 | 79 ± 2.65 | Anemochory | Escape-protection | |
|
LA | 10 | 0.15 ± 0.0028 | 0.792 ± 0.031 | 0.034 | 29 ± 1.91 | Barochory | Escape | |
|
|||||||||
Polygonaceae |
|
LS | 8 | 26.72 ± 1.21 | 10.138 ± 0.369 | 0.045 | 1 ± 0.58 | Anemochory | Escape-protection |
|
|||||||||
Tamaricaceae |
|
LS | 8 | 9.16 ± 0.12 | 6.050 ± 0.156 | 0.078 | 31.5 ± 2.50 | Anemochory | Escape-protection |
|
|||||||||
Plumbaginaceae |
|
LP | 8 | 0.26 ± 0.0063 | 2.622 ± 0.048 | 0.051 | 34.5 ± 12.53 | Anemochory | Escape |
|
LS | 8 | 0.30 ± 0.0052 | 2.784 ± 0.157 | 0.109 | 29 ± 6.56 | Anemochory | Escape | |
|
|||||||||
Fabaceae |
|
LS | 10 | 4.87 ± 0.064 | 3.672 ± 0.129 | 0.078 | 7.5 ± 1.89 | Autochory | Escape-protection |
|
LP | 8 | 37.90 ± 0.54 | 11.424 ± 0.639 | 0.091 | 8.23 ± 1.50 | Autochory | Escape-protection | |
|
LP | 8 | 9.04 ± 0.060 | 2.796 ± 0.151 | 0.038 | 7.5 ± 0.96 | Autochory | Escape-protection | |
|
LP | 8 | 19.00 ± 0.19 | 3.968 ± 0.074 | 0.039 | 9.13 ± 1.67 | Autochory | Escape-protection | |
|
E | 6 | 1.01 ± 0.018 | 2.248 ± 0.059 | 0.105 | 14.67 ± 1.33 | Autochory | Escape-protection | |
|
E | 6 | 0.88 ± 0.0096 | 2.100 ± 0.030 | 0.107 | 14.00 ± 3.06 | Autochory | Escape | |
|
|||||||||
Zygophyllaceae |
|
LS | 7 | 46.00 ± 0.91 | 7.916 ± 0.174 | 0.059 | 0 | Endozoochory | Protection |
|
LS | 8 | 106.53 ± 2.92 | 28.588 ± 1.133 | 0.051 | 83.5 ± 3.10 | Anemochory | Escape-protection | |
|
LP | 7 | 2.98 ± 0.92 | 3.704 ± 0.045 | 0.123 | 50.5 ± 6.70 | Anemochory | Escape-protection | |
|
|||||||||
Brassicaceae |
|
E | 6 | 0.37 ± 0.0050 | 1.474 ± 0.043 | 0.107 | 93.33 ± 1.76 | Ombrohydrochory | Escape |
|
E | 6 | 0.86 ± 0.0023 | 1.024 ± 0.040 | 0.08 | 6 ± 3.06 | Ombrohydrochory | Escape | |
|
E | 6 | 0.11 ± 0.0007 | 0.916 ± 0.025 | 0.081 | 23.33 ± 2.40 | Ombrohydrochory | Escape | |
|
E | 6 | 0.92 ± 0.0068 | 1.016 ± 0.038 | 0.074 | 46 ± 7.21 | Ombrohydrochory | Escape | |
|
E | 6 | 4.01 ± 0.065 | 3.740 ± 0.163 | 0.066 | 3.33 ± 0.67 | Epizoochory | Escape-protection | |
|
E | 6 | 0.095 ± 0.0011 | 0.966 ± 0.037 | 0.117 | 54.67 ± 8.74 | Ombrohydrochory | Escape | |
|
E | 6 | 0.21 ± 0.0039 | 1.588 ± 0.090 | 0.103 | 86.67 ± 7.33 | Ombrohydrochory | Escape | |
|
E | 6 | 2.24 ± 0.018 | 3.038 ± 0.115 | 0.095 | 18.67 ± 5.70 | Epizoochory | Escape-protection | |
|
|||||||||
Plantaginaceae |
|
LP | 9 | 0.55 ± 0.0055 | 1.244 ± 0.054 | 0.115 | 89.33 ± 0.67 | Ombrohydrochory | Escape |
|
E | 6 | 1.94 ± 0.021 | 3.546 ± 0.101 | 0.129 | 97.33 ± 0.67 | Ombrohydrochory | Escape-protection | |
|
LP | 8 | 0.44 ± 0.0057 | 1.756 ± 0.054 | 0.105 | 93 ± 3.32 | Ombrohydrochory | Escape | |
|
E | 6 | 2.04 ± 0.054 | 3.534 ± 0.090 | 0.129 | 76.67 ± 0.67 | Ombrohydrochory | Escape-protection | |
|
|||||||||
Compositae |
|
LS | 9 | 2.46 ± 0.040 | 1.546 ± 0.033 | 0.115 | 78.5 ± 3.20 | Ombrohydrochory | Escape-protection |
|
LP | 8 | 4.25 ± 0.041 | 4.876 ± 0.196 | 0.093 | 14 ± 2.45 | Epizoochory | Protection | |
|
LB | 8 | 9.82 ± 0.076 | 4.852 ± 0.053 | 0.09 | 82.5 ± 2.06 | Barochory | Escape-protection |
Notes: LA: long-lived Annuals; LBP: long-lived biennials-perennials; LPH: long-lived perennials; LS: long-lived shrubs; E: annuals/ephemerals.
Freshly matured intact natural dispersal units [
For each species, seeds traits and dispersal syndromes and strategies were determined and classified by follows.
Dispersal syndromes and characteristics of diaspores and number of species, genera, and families with each syndrome.
Dispersal syndrome | Secondary dispersal syndrome | Fruit type of storage material | Fruit or seed |
Number |
Number |
Number |
---|---|---|---|---|---|---|
Zoochory | Endozoochory | Berry, drupe, storage material (sugars, starches, lipids, or proteins), or capsule | Edible aril or pulp | 1 | 1 | 1 |
Epizoochory | Hook-like or sticky substance capsule | Adherence structure | 11 | 10 | 5 | |
|
||||||
Anemochory | Capsule, pod, and winged nut; dust seed (<0.01 mg); hairy; and pappus | Easily dispersal by wind | 25 | 17 | 7 | |
|
||||||
Autochory | Explosive capsule | Ballistic | 7 | 5 | 2 | |
|
||||||
Barochory | None | Seed dispersal via gravity | 15 | 8 | 4 | |
|
||||||
Ombrohydrochory | Mucilage | Seed produces mucilage when wetted | 11 | 8 | 3 |
Germination percentages of fresh seeds of the 70 species were determined under laboratory conditions. For each species, four replicates of 50 seeds were incubated on two layers of moist filter paper in 9 cm diameter Petri dishes at daily (12 h/12 h) light (fluorescent light, 30
Data were analyzed using SPSS 15.0 (SPSS, Chicago, USA). One-way ANOVA was used to test for differences (
The 70 species belong to 15 families and 48 genera, which accounted for 33.7% of the species, 39.0% of the genera, and 50% of the families in the Gurbantunggut Desert. Amaranthaceae was the most common family and included 18 genera and 32 species (Table
Proportion of dispersal syndromes in the three different dispersal strategies of species in the Gurbantunggut Desert.
Frequency distribution of seed mass (a), seed size (b), and seed shape (c) of the species in the Gurbantunggut Desert.
The range of seed mass and seed size for dispersal syndromes was greatest in anemochorous species, whereas seed mass was greatest in autochorous species and least in barochorous species. Seed size was largest for zoochorous species and smallest for barochorous species. Zoochorous species had the widest range and largest variance for seed shape and barochorous species the smallest. Seed mass (
Box plots showing mean (
Species with the escape-protection strategy had the largest and widest range of seed mass and those with the escape strategy the narrowest range and lowest seed mass. Species with the escape-protection strategy had the widest range of seed size and of shape variance. Species with the protection strategy had the largest seed size and most irregular seed shape and those with the escape strategy the smallest seed size and roundest seed shape. Seed mass (
Box plots showing mean (
Days to first germination (DFG) ranged from 1 day (i.e.,
Frequency distribution of days to first germination of the species.
Correlations between seed mass (
Relationships between mean seed mass (log10) (a), seed size
Mean germination percentage of four plant life forms. Biennials (<3 species) were excluded from the data.
Box plots showing mean (
Box plots showing mean (
Seed mass and shape are likely to be pivotal ecological traits for seedling establishment, formation of a persistent seed bank, and dispersal. Seed mass via the quantity of stored food reserves also affects plant regeneration, vegetative growth, and survival [
Our study showed that seed shape tended to be round or ellipse, which favours formation of a persistent soil seed bank, while larger, flattened, or elongate seeds are likely to form a transient soil seed bank [
Results of our study also show correlations between seed mass and seed dispersal syndromes. Barochorous seeds tended to be smaller and more rounded than the others (Figure
In other temperate areas, barochorous species are significantly more frequent than anemochorous and zoochorous species [
Because of a low amount of food in many deserts, massive numbers of seeds may be consumed by local animals, especially ants, the main seed predators in desert areas [
Seed germination traits are linked to water availability, biogeography, seed mass, seed shape, and plant life form. In deserts, the water necessary for seedling establishment is available following precipitation and snowmelt and thus seed germination occurs only under these favorable conditions [
The proportion of species with seed dormancy in this area was 82.9%. However, C. C. Baskin and J. M. Baskin reported that 95% of the species in cold deserts are dormant at maturity [
There are many studies about the relationship between life form and seed germination strategy [
Ephemeral plants are a special category in the Gurbantunggut Desert in that they depend on water from snowmelt to germinate, establish seedlings, and complete their life history in spring. As an adaptation to desert environments, ephemeral plants have fast and high germination when conditions are suitable. But why are germination percentages of shrubs higher than that of other life forms? Bu et al. gave a reasonable explanation: faster seed germination of shrubs might be due to their slower growth rate relative to the herbs. Thus, faster germination of shrubs would help them obtain competitive advantages in time and space [
The site where mother plants grow is identified as favorable by successful reproduction, and the best strategy would be to keep as many seeds as possible at the site. Ellner and Shmida studied species in the Negev Desert and suggested that the area near the mother plant was a “safe site” for seed germination and seedling survival [
Gutterman concluded that plants in the Negev Desert with seed protection strategies may develop cautious germination strategies, and plants with seed escape strategies may develop opportunistic germination strategies [
The authors declare that there is no conflict of interests regarding the publication of this paper.
Sincere thanks are extended to Professor Jerry Baskin and Professor Carol Baskin, University of Kentucky, Lexington, USA, for their critical review of and perceptive comments on the paper and for helping improve its language. Funds for this study were provided by the West Light Foundation of the Chinese Academy of Sciences (XBBS201303), the National Basic Research Priorities Program of China (2012FY111500), and the National Natural Science Foundation (31100399) of China.