scholarly journals Demographic vulnerability of an extreme xerophyte in arid Australia

2018 ◽  
Vol 66 (1) ◽  
pp. 26 ◽  
Author(s):  
Lynda D. Prior ◽  
Quan Hua ◽  
David M. J. S. Bowman
Keyword(s):  
Radiocarbon Dating ◽  
Arid Zone ◽  
Size Class ◽  
Mean Annual Precipitation ◽  
Class Structure ◽  
Mature Trees ◽  
Basal Diameter ◽  
Large Trees ◽  
Callitris Glaucophylla

Callitris glaucophylla (syn. C. columellaris F.Muell.) is an iconic Australian conifer that is suffering a recruitment deficit over much of the arid zone. Here, seedling establishment requires a series of unusually wet years, and protection from high levels of herbivory. The aim of our study was to determine the size class structure of C. glaucophylla populations in the most arid part (150 mm mean annual precipitation) of its range, and particularly whether seedlings had established during a wet period in 2010/11. We sampled C. glaucophylla populations throughout the region, including inside a 6000 ha feral animal exclosure. We found no seedlings from 2010/11, except on drainage lines adjacent to roads. Of 255 plots centred on mature trees, only 2% contained older seedlings, and 8% contained saplings, with no differences inside or outside exclosure, and 84% of trees were larger than 20 cm basal diameter. Matching dates of known regeneration with long-term rainfall records suggested that successful regeneration of C. glaucophylla requires a total of 600–720 mm of rain over a 2 year period. Our radiocarbon dating showed the age of three large trees ranged from 106 to 268 years, signifying that such trees in this region likely have only 2–8 climatic opportunities to reproduce.

Rainfall and grazing: not the only barriers to arid-zone conifer recruitment

2017 ◽  
Vol 65 (2) ◽  
pp. 109 ◽  
Author(s):  
Heidi C. Zimmer ◽  
Singarayer K. Florentine ◽  
Rita Enke ◽  
Martin Westbrooke
Keyword(s):  
Arid Zone ◽  
Stand Density ◽  
Grazing Pressure ◽  
Large Herbivore ◽  
Large Herbivores ◽  
South Wales ◽  
Large Trees ◽  
Callitris Glaucophylla ◽  
And Control

An understanding of the drivers of infrequent recruitment is fundamental in managing for species persistence. Callitris glaucophylla Joy Thomps. & L.A.S. Johnson (white cypress-pine) is a slow-growing, long-lived conifer, with a distribution that extends across arid Australia. Arid populations of C. glaucophylla are endangered in New South Wales, and are characterised by infrequent recruitment. We examined recruitment patterns of C. glaucophylla in differential grazing exclosures (excluding rabbits, excluding large herbivores or excluding both) and in unfenced areas. More recruitment occurred in rabbit-proof exclosures, compared with nearby large herbivore and control exclosures, although some rabbit-proof exclosures recorded no recruitment. Increases in recruitment at several long-term exclosures were associated with wet periods, as was recruitment at some unfenced sites. Apart from grazing and rainfall, recruitment was related to mature tree size and stand density (probably because of their influence on seed availability). These endangered arid C. glaucophylla woodlands are all that remains of a once extensive distribution, and are habitat for a suite of threatened species. Reduction in grazing pressure, particularly from rabbits, is clearly critical to maintain recruitment in these remnant populations. Chances of recruitment appear to be enhanced in low-density stands, around large trees, and in dune blow outs – fencing should focus on these areas.

scholarly journals Size-class structure of the forests of Finland during 1921–2013: a recovery from centuries of exploitation, guided by forest policies

2019 ◽  
Vol 139 (2) ◽  
pp. 279-293
Author(s):  
Helena M. Henttonen ◽  
Pekka Nöjd ◽  
Susanne Suvanto ◽  
Juha Heikkinen ◽  
Harri Mäkinen
Keyword(s):  
Land Use ◽  
Geographical Area ◽  
Species Group ◽  
Size Class ◽  
Class Structure ◽  
Initial State ◽  
Frequency Distributions ◽  
Size Classes ◽  
Growing Stock ◽  
Large Trees

AbstractFrequency distributions of tree diameters are a powerful tool for analyzing changes of tree populations in large areas. We analyzed the densities and mean volume estimates of trees in different size classes for the Finnish forests over the time-span of the National Forest Inventories (1921–2013). The results display a general increase in trees in all size classes, species group and geographical area, mainly after the 1970s. The densities of medium- and large-sized conifers showed large increases in the southern boreal subzone, spruces even more than pines. Small- to medium-sized pines have increased in the middle and northern boreal subzones. The shifts in growing stock are related to changing land use, resulting from the development of the society. The low quantities of both growing stock and large trees during the 1920s reflect a poor initial state of forests. Several land use forms of the former agriculture-based society were detrimental to forests, including slash and burn agriculture, cattle grazing and tar production. The pressure from alternative land use forms was stronger in southern Finland, where the population density (people per km2) is much higher. Between 1971 and 2013, the changes in size-class structure can be attributed mainly to intensified silviculture boosted by actions of the Finnish governments, including both legislation and financial support for management activities. Not only the development of growing stock has exceeded expectations, but the increase has also concentrated in the economically valuable trees in the large size classes.

The benefits of seed enrichment on sandalwood (Santalum spicatum) populations, after 17 years, in semi-arid Western Australia

2014 ◽  
Vol 36 (5) ◽  
pp. 475 ◽  
Author(s):  
Jonathan E. Brand ◽  
Benjamin Sawyer ◽  
David R. Evans
Keyword(s):  
Western Australia ◽  
Seedling Survival ◽  
Size Class ◽  
Stem Diameter ◽  
Class Structure ◽  
Large Trees ◽  
Land Systems ◽  
Santalum Spicatum ◽  
Semi Arid ◽  
Germinated Seeds

Initially, the size-class structure of 1067 natural sandalwood (Santalum spicatum) trees and seedlings, growing in populations at three semi-arid sites (Burnerbinmah, Ninghan and Goongarrie) in Western Australia, was measured during 1996–97. These same populations, and any new sandalwood seedlings and small trees that had established after 1996–97, were measured again after 17 years (2013). Size-class structure was assessed by measuring over-bark stem diameter at 150 mm above the ground. Populations of sandalwood trees at the Burnerbinmah and Ninghan sites failed to regenerate and, after 17 years, they contained only 0–3% small trees and 0–2% seedlings. Their overall population size declined by 21–24% and, combined with recruitment failure, these natural stands of sandalwood may largely disappear within 50–60 years. At the Goongarrie site, the proportion of large trees within the natural population increased from 58% to 82%. The proportion of small trees was constant at 13–16%, while seedlings declined from 29% to 2%. The population reduced by 35%, mainly due to high seedling mortality. Although the population was in decline, there appeared to be enough small trees and seedlings to maintain the population longer than at both the Burnerbinmah and Ninghan sites. In a second study, 16 640 sandalwood seeds were sown at the same three sites during 1996–97, and then assessed for germination, survival, growth and fruit production over 17 years. Sandalwood germination and growth were compared between locations, fencing treatments and land systems. Seed enrichment was successful at each site with 27–45% germination and 6–20% survival (from germinated seeds) after 17 years. The overall seedling survival rates (from total seeds sown) ranged from 2.1% to 5.2%. Mean stem diameter of seedlings was significantly larger at Goongarrie (37 mm) than at both Burnerbinmah and Ninghan (20–22 mm) sites. Grazing significantly affected the performance of sandalwood seedlings at an age of 17 years at the Ninghan site. At this site, seedling survival (from germinated seeds) was 16% in the fenced plots compared with only 6% in the unfenced plots. Mean stem diameter in the fenced plots (24 mm) was also significantly greater than in the unfenced plots (11 mm). Land systems did not affect survival of sandalwood seedlings at the Burnerbinmah site but had a significant impact at the Goongarrie site after 17 years. Seedling survival was significantly greater on the hills and ridges than those growing on the plains with granite and red sand plains. Seed-enrichment programs are recommended to improve long-term regeneration and sustainability of sandalwood trees.

Post-fire survival and flushing in three Sierra Nevada conifers with high initial crown scorch

2009 ◽  
Vol 18 (7) ◽  
pp. 857 ◽  
Author(s):  
Chad T. Hanson ◽  
Malcolm P. North
Keyword(s):  
Sierra Nevada ◽  
Pinus Ponderosa ◽  
Fire Severity ◽  
Conifer Species ◽  
Mature Trees ◽  
Salvage Logging ◽  
Abies Magnifica ◽  
Crown Scorch ◽  
Tree Survival ◽  
Large Trees

With growing debate over the impacts of post-fire salvage logging in conifer forests of the western USA, managers need accurate assessments of tree survival when significant proportions of the crown have been scorched. The accuracy of fire severity measurements will be affected if trees that initially appear to be fire-killed prove to be viable after longer observation. Our goal was to quantify the extent to which three common Sierra Nevada conifer species may ‘flush’ (produce new foliage in the year following a fire from scorched portions of the crown) and survive after fire, and to identify tree or burn characteristics associated with survival. We found that, among ponderosa pines (Pinus ponderosa Dougl. ex. Laws) and Jeffrey pines (Pinus jeffreyi Grev. & Balf) with 100% initial crown scorch (no green foliage following the fire), the majority of mature trees flushed, and survived. Red fir (Abies magnifica A. Murr.) with high crown scorch (mean = 90%) also flushed, and most large trees survived. Our results indicate that, if flushing is not taken into account, fire severity assessments will tend to overestimate mortality and post-fire salvage could remove many large trees that appear dead but are not.

scholarly journals Paleoclimatic Implications of Radiocarbon Dating Of Speleothems from the Cracow-Wieluń Upland, Southern Poland

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 103-110 ◽  
Author(s):  
Anna Pazdur ◽  
Mieczysław F. Pazdur ◽  
Jacek Pawlyta ◽  
Andrzej Górny ◽  
Michał Olszewski
Keyword(s):  
Systematic Study ◽  
Radiocarbon Dating ◽  
Karst Region ◽  
Radiocarbon Dates ◽  
Preliminary Results ◽  
Last Glaciation ◽  
Geological Museum ◽  
Paleoclimatic Records ◽  
Age Range

We report preliminary results of a long-term systematic study intended to gather paleoclimatic records from precisely dated speleothems. The research project is limited to speleothems deposited in caves of the Cracow-Wieluń Upland, the largest and best-explored karst region in Poland, covering ca. 2900 km2 with >1000 caves. Speleothem samples were selected from collections of the Geological Museum of the Academy of Mining and Metallurgy in Cracow. Radiocarbon dates of these samples from ca. 45–20 ka bp almost exactly coincide with age range of the Interplenivistulian. A break in speleothem formation between ca. 20 and 10 ka bp may be interpreted as a result of serious climatic deterioration associated with the maximum extent of the last glaciation. We observed differences among 14C, U/Th and AAR dating results. Changes of δ13C and δ18O in speleothems that grew between ca. 30 and 20 ka bp may be interpreted as changes of paleoclimatic conditions.

scholarly journals Ice genesis and its long-term dynamics in Scărişoara Ice Cave, Romania

2010 ◽  
Vol 4 (4) ◽  
pp. 1909-1929
Author(s):  
A. Perşoiu ◽  
A. Pazdur
Keyword(s):  
Radiocarbon Dating ◽  
Ice Age ◽  
Clear Understanding ◽  
Lake Ice ◽  
Ice Flow ◽  
Paleoclimatic Significance ◽  
Basal Melting ◽  
Perennial Ice ◽  
Level Monitoring

Abstract. The paleoclimatic significance of the perennial ice deposit in Scărişoara Ice Cave has been remarked since the early 20th century, but a clear understanding of the processes involved in the genesis, age and long-term dynamics of ice hampered all attempts to extract valuable data on past climate and vegetation changes. In this paper, we present a model of ice genesis and dynamics, based on stable isotopes, ice level monitoring (modern and archived) and radiocarbon dating of organic matter found in the ice. Ice in Scărişoara Ice Cave mostly consists of layers of lake ice, produced as liquid water freezes from top to bottom in mid-autumn, a mechanism that was also acting in the past, during the Medieval Warm Period and the Little Ice Age. The ice block is not stable in shape and volume, being continuously modified by ablation on top, basal melting and lateral flow. Radiocarbon dating shows that the ice block is older than 1200 years, the rate of ice flow and basal melting suggesting that the ice could be much older.

scholarly journals MODELING PRECIPITATION DEPENDENT FOREST RESILIENCE IN INDIA

2018 ◽  
Vol XLII-3 ◽  
pp. 263-266 ◽  
Author(s):  
P. Das ◽  
M. D. Behera ◽  
P. S. Roy
Keyword(s):  
Forest Cover ◽  
Vegetation Type ◽  
Annual Precipitation ◽  
Mean Annual Precipitation ◽  
High Tendency ◽  
North East India ◽  
North East ◽  
Forest Resilience ◽  
The Impact

The impact of long term climate change that imparts stress on forest could be perceived by studying the regime shift of forest ecosystem. With the change of significant precipitation, forest may go through density change around globe at different spatial and temporal scale. The 100 class high resolution (60 meter spatial resolution) Indian vegetation type map was used in this study recoded into four broad categories depending on phrenology as (i) forest, (ii) scrubland, (iii) grassland and (iv) treeless area. The percentage occupancy of forest, scrub, grass and treeless were observed as 19.9&amp;thinsp;%, 5.05&amp;thinsp;%, 1.89&amp;thinsp;% and 7.79&amp;thinsp;% respectively. Rest of the 65.37&amp;thinsp;% land area was occupied by the cropland, built-up, water body and snow covers. The majority forest cover were appended into a 5&amp;thinsp;km&amp;thinsp;&amp;times;&amp;thinsp;5&amp;thinsp;km grid, along with the mean annual precipitation taken from Bioclim data. The binary presence and absence of different vegetation categories in relates to the annual precipitation was analyzed to calculate their resilience expressed in probability values ranging from 0 to 1. Forest cover observed having resilience probability (Pr) &amp;lt;&amp;thinsp;0.3 in only 0.3&amp;thinsp;% (200&amp;thinsp;km<sup>2</sup>) of total forest cover in India, which was 4.3&amp;thinsp;% &amp;lt;&amp;thinsp;0.5&amp;thinsp;Pr. Majority of the scrubs and grass (64.92&amp;thinsp;% Pr&amp;thinsp;&amp;lt;&amp;thinsp;0.5) from North East India which were the shifting cultivation lands showing low resilience, having their high tendency to be transform to forest. These results have spatial explicitness to highlight the resilient and non-resilient distribution of forest, scrub and grass, and treeless areas in India.

Physiological and morphological effects of climate change

2019 ◽  
pp. 120-133 ◽  
Author(s):  
Andrew E. McKechnie
Keyword(s):  
Climate Change ◽  
Body Mass ◽  
High Temperatures ◽  
Arid Zone ◽  
Future Research ◽  
Long Term Effects ◽  
Adaptation To Climate Change ◽  
Heat Events

The direct impacts of higher temperatures on birds are manifested over timescales ranging from minutes and hours to years and decades. Over short timescales, acute exposure to high temperatures can lead to hyperthermia or dehydration, which among arid-zone species occasionally causes catastrophic mortality events. Over intermediate timescales of days to weeks, high temperatures can have chronic sub-lethal effects via body mass loss or reduced nestling growth rates, negatively affecting sev eral fitness components. Long-term effects of warming manifested over years to decades involve declining body mass or changes in appendage size. Key directions for future research include elucidating the role of phenotypic plasticity and epigenetic processes in avian adaptation to climate change, examining the role of stress pathways in mediating responses to heat events, and understanding the consequences of higher temperatures for species that traverse hot regions while migrating.

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