scholarly journals Is a long hygroscopic awn an advantage for Themeda triandra in drier areas?

2020 ◽  
Author(s):  
Craig D Morris
Keyword(s):  
Rotational Speed ◽  
Soil Surface ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient ◽  
Themeda Triandra ◽  
Daily Movement ◽  
Blotting Paper ◽  
Mesic Grassland ◽  
Kwazulu Natal ◽  
Aridity Indices

AbstractThemeda triandra has bigeniculate hygroscopic lemma seed awns that twist when wet and drying, thereby transporting the caryopsis across the soil surface into suitable germination microsites. The prediction that awns would be longer in drier grassland and have greater motility to enable them to move quickly and further to find scarce germination sites was tested in KwaZulu-Natal. Awns (n = 100) were collected from 16 sites across a mean annual precipitation gradient (575-1223 mm), ranging from 271-2097 m a.s.l. The daily movement of hydrated long and short awns (n = 10) across blotting paper was tracked for five days, and the rotational speed of anchored awns was measured. Awn length varied considerably (mean: 41.4-63.2 mm; sd: 3.44-8.99) but tended to increase (r = 0.426, p = 0.099) not decline, with increasing MAP. Awn length was unrelated to elevation, temperature and aridity indices. Long awns rotated at the same rate (2 min 48 sec) but moved twice as fast (46.3 vs. 22.1 mm day-1) and much further (maximum: 82.1 vs. 38.6 mm day-1) than short awns. Whether moisture limits awn development, the benefit of longer awns to negotiate densely tufted mesic grassland, and the multifunctionality of awns require investigation.

scholarly journals High Resolution of Water Availability for Emilia-Romagna Region over 1961–2015

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
F. Cervi ◽  
M. M. Nistor
Keyword(s):  
Water Availability ◽  
Soil Surface ◽  
Mean Annual Precipitation ◽  
Mean Annual Temperature ◽  
North East ◽  
The North ◽  
Precipitation Decrease ◽  
Normal Period ◽  
Emilia Romagna Region ◽  
Annual Water

In this study, monthly time series of precipitations and temperatures from 1024 controlled and homogeneous meteorological stations located in the Emilia-Romagna region (northern Italy) are processed in order to assess potential climate changes that occurred during the period 1961–2015. Normal period as baseline between 1961 and 1990 (1990s) and recent period between 1991 and 2015 (2010s) were adopted in this study to analyse the possible effect of climate change on water availability during long-term period. Based on monthly and annual temperature (TT), precipitation (PP), and potential (ET0), the actual evapotranspiration (AET0) and water availability (WA) were computed at high spatial resolution. Between the two analysed periods, during the 2010s, it was found an increase in the maximum mean annual temperature by 1.08°C while the maximum mean annual precipitation saw a slight decrease (from 2222 mm to 2086 mm). The precipitation decrease is more intense in the South and West sectors of area (8%) and mainly depends on negative changes taking place during the winter and the beginning of spring (from December to March). The maximum mean annual ET0 and AET0 reached values of 663 mm and 565 mm during the 1990s, while during the 2010s, the found values were 668 mm and 572 mm, respectively. Because of the decrease in precipitation and increase in the ET0 and AET0, the WA (the proportion of precipitation that is available at the soil surface for subsequent infiltration and runoff processes) shows a reduction (about 10–20%) in the whole region, with exception of the North-East part of the Emilia-Romagna region. The decrease in the mean annual water availability induces severe issues concerning the water resources management across the whole Emilia-Romagna region.

Nitrogen fixation beyond leguminous plants: characterising overlooked plant-bacteria associations in the light of climate change

2020 ◽  
Author(s):  
Kathrin Rousk
Keyword(s):  
Climate Change ◽  
Nitrogen Fixation ◽  
Community Composition ◽  
Abiotic Factors ◽  
Arctic Tundra ◽  
The Arctic ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient ◽  
Cyanobacterial Community ◽  
Moss Species

<p>Nitrogen (N<sub>2</sub>) fixation performed by moss-associated cyanobacteria is one of the main sources of new N in pristine, high latitude ecosystems like boreal forests and arctic tundra. Here, mosses and associated cyanobacteria can contribute more than 50% to total ecosystem N input. However, N<sub>2</sub> fixation in mosses is strongly influenced by abiotic factors, in particular moisture and temperature. Hence, climate change will significantly affect this key ecosystem process in pristine ecosystems. Here, I will present a synthesis of several field and laboratory assessments of moss-associated N<sub>2</sub> fixation in response to climate change by manipulating moisture and temperature in subarctic and arctic tundra.</p><p>Both in a long-term climate warming experiment in the arctic, and along a continental climate gradient, spanning arctic, subarctic and temperate ecosystems, increased temperatures (up to 30 °C) lead to either no effect or decreased N<sub>2</sub> fixation rates in different moss species. Yet, N<sub>2</sub> fixation rates were strongly dependent on moss-moisture, which seems to be a more important driver of N<sub>2</sub> fixation in mosses than temperature.</p><p>In another set of studies, two dominant moss species (Hylocomium splendens, Pleurozium schreberi) were collected from a steep precipitation gradient (400-1200 mm mean annual precipitation, MAP) in the Subarctic close to Abisko, Northern Sweden, and were incubated at different moisture and temperature levels in the laboratory. Nitrogen fixation, cyanobacterial abundance (via qPCR) and cyanobacterial community composition (via sequencing) on the mosses were assessed. Moisture and temperature interacted strongly to control moss-associated N<sub>2</sub> fixation rates, and the highest activity was found at the wet end of the precipitation gradient. Although cyanobacterial abundance was higher in one of the investigated mosses (H. splendens), translating into higher N<sub>2</sub> fixation rates, cyanobacterial community composition did not differ between the two moss species. Nostoc was the most common cyanobacterial genera on both mosses, and hardly any methanotrophic N<sub>2</sub> fixing bacteria were found on the mosses along the precipitation gradient. Increased temperatures lead to increased abundances of certain cyanobacterial genera (Cylindrospermum and Nostoc), while others declined in response to warming. Hence, cyanobacterial communities colonizing mosses will be dominated by a few cyanobacteria species in a warmer climate, and temperature and moisture interact strongly to affect their activity. Thus, these two major climate change factors should be considered in unison when estimating climate change effects on key ecosystem processes such as N<sub>2</sub> fixation. Further, host identity determines cyanobacterial abundance, and thereby, N<sub>2</sub> fixation rates.</p><p> </p><p> </p><p> </p>

Prevalence and Diversity of Entomopathogenic Nematodes Spanning a Mean Annual Precipitation Gradient in Pastureland in Oklahoma

2016 ◽  
Vol 41 (4) ◽  
pp. 933-944 ◽  
Author(s):  
Kyle Risser ◽  
Carmen Greenwood ◽  
Nathan Walker ◽  
Mark Payton ◽  
Justin Talley
Keyword(s):  
Entomopathogenic Nematodes ◽  
Annual Precipitation ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient

scholarly journals INFLUENCES OF BIOLOGICAL PREPARATIONS ON SOIL PROPERTIES IN THE SPRING WHEAT CROP

2018 ◽  
Author(s):  
Rita ČEPULIENĖ ◽  
Darija JODAUGIENĖ
Keyword(s):  
Spring Wheat ◽  
Soil Surface ◽  
Chemical Compounds ◽  
Mean Annual Precipitation ◽  
Wheat Crop ◽  
Mean Annual Temperature ◽  
Biological Processes ◽  
Micro Structure ◽  
The Mean ◽  
Fertilizer Rates

The natural biochemical, biophysical and biological processes in the soil is changing due to the intensive use of pesticides. At present, it is actual fertilization technologies, which are based on non-fertilizer rates increase bat on their rational use because in the fertilizer is unnecessary chemical compounds that promote mineral nutritional elements leaching. Have been studied the effect of biological preparations BactoMix, AgroMik and Rizobakterin on soil physical properties. Experiments were carried out in 2015–2016 at the Experimental Station of Aleksandras Stulginskis University on Calcari-Endohypogleyic Luvisol. The mean annual temperature of the study site is 6.0–6.5 °C, mean annual precipitation is 600–650 mm and mean annual length of sun shine is 1750–1800 hour (Lithuanian Hydrometeorological Service). Biological preparations sprayed on the soil surface and incorporated in the soil by sowing spring wheat. The use of biological preparations had a tendency to reduce soil density (from 2.3 to 5.3 %), to increase soil porosity (from 0.6 to 2.1 %). Biological preparations had no significant influence on quantity couples filled with moisture and air. The hardness of the soil after spring wheat harvest was the smallest in the fields sprayed by Rizobakterin preparation. The use of biological preparations BaktoMix and Rizobakterin significantly increased soil moisture. The following preparations significantly decreased soil pulverized fractions (micro structure) and significantly increased amount of particles larger than 10 mm.

Reliability of the Artemisia/Chenopodiaceae pollen ratio in differentiating vegetation and reflecting moisture in arid and semi-arid China

The Holocene ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 858-864 ◽  
Author(s):  
Yuan Wang ◽  
Wei Wang ◽  
Lina Liu ◽  
Yajuan Jiang ◽  
Zhimei Niu ◽  
...  
Keyword(s):  
Inner Mongolia ◽  
Surface Sediments ◽  
Qaidam Basin ◽  
Source Area ◽  
Soil Surface ◽  
Mean Annual Precipitation ◽  
Climate Reconstructions ◽  
Moisture Conditions ◽  
Semi Arid ◽  
Inner Mongolia Plateau

The reliability of the ratio between Artemisia and Chenopodiaceae pollen percentage (i.e. A/ C) in differentiating vegetation and reflecting moisture conditions in arid and semi-arid regions has been disputed and this hindered its potential application in palaeoclimate reconstructions. In this paper, we investigated the A/ C ratios of lake-centre surface sediment from 45 lakes in the Inner Mongolia Plateau and the Qaidam Basin in arid and semi-arid China, and numerically studied the relationships of A/ C ratios with vegetation and moisture. We found that the A/ C ratio of lake-centre surface sediments can be used as an effective index to differentiate desert and steppe and also can be used as a valid indicator to infer mean annual precipitation (MAP) in the Inner Mongolia Plateau and the Qaidam Basin in arid and semi-arid China. Moreover, the A/ C ratio from lake-centre surface sediments is more reliable and robust than that of soil-surface samples in differentiating vegetation and reflecting moisture conditions, and this might be attributed to its larger pollen source area and regional representation. In addition, the ( A − C)/( A + C) index helps to overcome the inherent weakness of non-linearity of the A/ C ratio and may be useful in paleo-vegetation reconstruction. These findings provide useful references for pollen-based vegetation and climate reconstructions of lake cores in arid and semi-arid China.

scholarly journals Carbon and nitrogen dynamics of native <i>Leymus chinensis</i> grasslands along a 1000 km longitudinal precipitation gradient in northeastern China

2014 ◽  
Vol 11 (24) ◽  
pp. 7097-7106 ◽  
Author(s):  
L. Ma ◽  
S. Yuan ◽  
C. Guo ◽  
R. Wang
Keyword(s):  
Aboveground Biomass ◽  
Northeastern China ◽  
Annual Precipitation ◽  
Leymus Chinensis ◽  
Mean Annual Precipitation ◽  
N Availability ◽  
Ecosystem Structure ◽  
Precipitation Gradient ◽  
Organic Matter Quality ◽  
C And N

Abstract. Understanding how ecosystem carbon (C) and nitrogen (N) cycles respond to the variability of precipitation can help us assess the effects of global climate change on terrestrial ecosystem structure and function. We investigated the contributions of aboveground biomass, litter, root, soil and microbial communities to ecosystem C and N processes at 14 sites along a 1000 km precipitation gradient in native Leymus chinensis grasslands of northeastern China. The results show that aboveground biomass C and N increased gradually, while no significant regional trends in litter and root biomass were found with increasing mean annual precipitation (MAP) along the gradient. Soil respiration increased first and then decreased from the dry to mesic sites, which could be ascribed to the relative changes in temperature, soil fungal : bacterial biomass and N availability. Surprisingly, N mineralization varied only slightly along the gradient, likely due to the decreases of soil organic matter quality (i.e., C : N). Stepwise regression models indicated regional soil C and N content positively correlated with MAP and clay content. Overall, C and N sequestration increased 3.2- and 1.8-fold with increasing MAP in terms of C and N storage in aboveground biomass, roots, litter and soil. It was concluded from the current study that regional precipitation variability strongly influences ecosystem C and N dynamics. The ecosystem C and N sequestration are primarily modulated by annual precipitation and soil texture, while the C and N turnover are largely controlled by microbial community composition, temperature and soil quality in L. chinensis grasslands across the large-scale precipitation gradient.

scholarly journals The Joint Effects of Precipitation Gradient and Afforestation on Soil Moisture across the Loess Plateau of China

Forests ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 285 ◽  
Author(s):  
Qindi Zhang ◽  
Wei Wei ◽  
Liding Chen ◽  
Lei Yang
Keyword(s):  
Soil Moisture ◽  
Loess Plateau ◽  
Regional Scale ◽  
Mean Annual Precipitation ◽  
Precipitation Gradient ◽  
Vegetation Types ◽  
The Loess Plateau ◽  
Deep Soil ◽  
Ecological Regions ◽  
Caragana Korshinskii

Understanding the dependence of soil moisture changes following afforestation on the precipitation gradient and afforested vegetation types is crucial for improving ongoing afforestation projects, and to guide future restoration strategies in water-limited regions. For this study, we characterized afforestation-induced changes in soil moisture at depths of 0–3.0 m across a precipitation gradient in the semi-arid Loess Plateau of China. A paired experiment was conducted across 15 sites, where native grasslands served as the baseline hydrology. The results showed that korshinsk peashrub (Caragana korshinskii Kom.), sea buckthorn (Hippophae rhamnoides L.), and black locust (Robinia pseudoacacia L.) afforestation caused an overall strong decline in soil moisture content at depths of below 2.2 m. The degree of soil moisture decline at the regional scale did not vary between different afforested vegetation types but was contingent on precipitation. With decreasing precipitation gradients, afforestation increased the cost of deep soil moisture. Precipitation restrictions began to appear at mean annual precipitation (MAP) = 520 mm, and were intensified at MAP = 380 mm, which could be employed to divide the Loess Plateau into different ecological regions. Because of this, different strategies should be assigned in future restoration practices to these ecological regions to align with localized precipitation conditions. It will likely be prudent to encourage afforestation in areas with MAP of more than 520 mm, while advocating alternative grassland restoration in areas with MAP of less than 380 mm.

Germination and Establishment of Themeda triandra (Kangaroo Grass) as Affected by Soil and Seed Characteristics

1993 ◽  
Vol 41 (1) ◽  
pp. 105 ◽  
Author(s):  
BM Sindel ◽  
SJ Davidson ◽  
MJ Kilby ◽  
RH Groves
Keyword(s):  
Relative Humidity ◽  
Soil Surface ◽  
High Moisture Content ◽  
High Moisture ◽  
Themeda Triandra ◽  
Seed Supply ◽  
Diurnal Fluctuations ◽  
Cleaning Methods ◽  
Seed Characteristics ◽  
Natural Means

The seed supply of Themeda triandra, syn. T. australis (kangaroo grass), for revegetation purposes may always be limited given the biological constraints on its production. It is important, therefore, that available seed be used efficiently by maximising germination and establishment. In two glasshouse experiments, we investigated the effects of various soil and seed factors and their interactions on germination and establishment of seeds sown on the soil surface and at depth. Maximum germination was achieved by either de-awning seeds and burying them manually at 1 cm depth or by sowing awned seeds on the soil surface in the vicinity of cracks or stones which allowed up to 96% of the seeds to bury themselves by natural means. Diurnal fluctuations in relative humidity of only 30% caused the 4-6 cm long geniculate awns to twist hygroscopically, thereby propelling the seeds along the soil surface and increasing their chances of becoming buried in favourable or 'safe' microsites for germination. A bitumen-coated straw mulch improved germination of de-awned seeds by maintaining high moisture content in the top 2 cm of soil, but inhibited the movement of awned seeds along the soil surface and their entry into safe microsites for germination. The data are discussed in terms of maximising germination and seedling establishment of Themeda, determining the most appropriate seed harvesting and cleaning methods, and selecting sowing methods which are most likely to be effective.

Seed Longevity of Six Native Forbs in a Closed Themeda triandra Grassland

1995 ◽  
Vol 43 (5) ◽  
pp. 439 ◽  
Author(s):  
ID Lunt
Keyword(s):  
Soil Seed Bank ◽  
Seed Mass ◽  
Soil Surface ◽  
Seed Longevity ◽  
Short Term ◽  
Themeda Triandra ◽  
Native Grassland ◽  
Buried Seeds ◽  
Small Seed ◽  
Closed Canopy

Seeds of six native forbs̵2Arthropodium strictum R.Br., Burchardia umbellata R.Br., Bulbine bulbosa (R.Br.) Haw., Chrysocephalum apiculatum (Labill.) Steetz, Craspedia variabilis Everett & Doust and Leptorhynchos squamatus (Labill.) Less.-were sown on and below the soil surface in a closed, native grassland dominated by Themeda triandra Forsskal. Replicate seed lots were recovered after 2, 4, 6, 9 and 12 months, and viability was assessed. Less than 7% of sown surface seeds of B. bulbosa, B. umbellata, C. variabilis and L. squamatus, and less than 10% of buried seeds of A. strictum, B. umbellata and C. variabilis remained viable after 12 months. Virtually all losses of Liliaceae seeds were due to germination. Fates of Asteraceae seeds were difficult to assess accurately after 6 months, but germination accounted for most seed losses. Burial significantly promoted longevity of B. bulbosa, C. variabilis and L. squamatus seeds. No obvious relationship existed between seed longevity and taxonomic group (Liliaceae versus Asteraceae) or seed mass, for surface or buried seeds; the response of the large-seeded lily, B. bulbosa, was most similar to that of the small-seeded daisy, L. squamatus. Of the six species, C. apiculatum appears to have the greatest potential to accumulate a soil seed bank beneath a closed grass canopy, owing to its small seed size, inhibition of germination beneath a closed canopy, both on and below the soil surface, and sustained viability of buried seeds. Naturally dispersed seeds of the other five species are likely to form smaller, transient or short-term seed banks.

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