Journal articles on the topic 'Xeric'
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1
Eslami, S. V. "Comparative Germination and Emergence Ecology of Two Populations of Common Lambsquarters (Chenopodium album) from Iran and Denmark." Weed Science 59, no. 1 (March 2011): 90–97. http://dx.doi.org/10.1614/ws-d-10-00059.1.
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Common lambsquarters, a summer annual weed, has occupied comparatively different ecogeographical regions around the globe. To investigate the extent to which germination and emergence traits have differentiated in two natural populations of common lambsquarters from different environments (Denmark as mesic and Iran as xeric population), experiments were conducted in the laboratory. Germination of both populations was stimulated by light. The greatest germination percentage of xeric and mesic populations occurred at 25/15 and 20/10 C, respectively. The xeric population showed significantly greater germinability at the lowest (15/5 C) and the highest (35/25 C) fluctuating temperature regimes. Germination of the xeric population was only slightly affected, and the mesic population was severely retarded at a salinity level of 20 desi siemens (DS) m−1. Greater than 42% of the xeric seeds germinated at 30 dS m−1salinity, while the mesic germination almost ceased at this salinity level. Germination of seeds placed in distilled water after the 14-d salinity exposure treatments (recovery rates) was also greater for the xeric vs. mesic populations. Xeric populations showed more than 65% germination up to the osmotic potential of −0.4 MPa, while decreasing osmotic potential from 0 to −0.4 MPa caused an 80% reduction in mesic population germinability (9% germination). The greatest emergence of xeric (77%) and mesic (70%) populations occurred for seeds placed on the soil surface and no seedlings emerged from burial depth 3 cm. These study results suggest that common lambsquarters populations have differentiated for heat, salinity, and drought tolerance at germination stage. These contrasting germination patterns are appeared to be due to either adaptation via natural selection or maternal effects, or some combination of both. Though this study has certain limitations, it, through its findings and their propositions, adds to the existing knowledge about interpopulation differences in germination requirements of common lambsquarters, as a globally distributed species.
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Kubiske, Mark E., and Marc D. Abrams. "Photosynthesis, water relations, and leaf morphology of xeric versus mesic Quercusrubra ecotypes in central Pennsylvania in relation to moisture stress." Canadian Journal of Forest Research 22, no. 9 (September 1, 1992): 1402–7. http://dx.doi.org/10.1139/x92-186.
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Differences in photosynthesis and water relations during drought, and in leaf morphology, were evaluated in 1-year-old greenhouse-grown Quercusrubra L. seedlings from neighboring mesic and xeric sites in central Pennsylvania, U.S.A. Xeric seedlings had higher photosynthetic rates and stomatal conductance to water vapor than mesic seedlings during well-watered conditions. During a drought cycle, xeric seedlings maintained positive net photosynthesis at significantly lower predawn leaf water potential and relative water content. Mesic seedlings exhibited greater intrasource variation in gas exchange during drought, which may be related to reduced selection pressure for drought tolerance characteristics on the mesic site or to gene flow from the adjacent, upslope xeric site. Nonstomatal limitations to photosynthesis increased during drought and accounted for 98% of the reduction in photosynthesis as both sources approached incipient wilting. Xeric seedlings exhibited less nonstomatal inhibition of photosynthesis during early and midstages of drought, suggesting a greater tolerance of the photosynthetic apparatus for tissue water deficit. Xeric seedlings also exhibited the expected leaf morphological characteristics, which included smaller leaf area and greater leaf thickness and specific leaf mass. These results indicate that Q. rubra growing on adjacent sites in central Pennsylvania exhibit ecotypic differences in ecophysiology that are consistent with site moisture conditions.
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Caraco, N. F., N. F. Caraco, J. J. Cole, and J. J. Cole. "Human influence on nitrogen export: a comparison of mesic and xeric catchments." Marine and Freshwater Research 52, no. 1 (2001): 119. http://dx.doi.org/10.1071/mf00083.
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Human impact on export of nitrogen in rivers is of great concern because increases in nitrogen export can dramatically increase primary productivity and decrease water quality in the coastal zone. Most research on this has been done for mesic catchments and not the xeric catchments that cover a large fraction of the earth’s surface. This paper uses river data to compare whole-catchment nitrogen export from xeric and mesic areas and human impact on this export. Results suggest that although nitrogen export is lower from xeric catchments than from mesic catchments, human impact on export and forms of nitrogen being exported may be similar. In both xeric and mesic catchments with low population density (<20 humans km–2) the export of nitrate averages only 30%of export from catchments with populations ≥20 humans km–2. For organic N export there is little effect of human population in either xeric or mesic catchments. Thus, for both xeric and mesic catchments human activity is associated with a shift in dominant form of N being exported. On average, organic N is the dominant form of nitrogen being exported at low human population densities, whereas inorganic N export tends to dominate at higher population densities.
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Comeau, Philip G., and James P. Kimmins. "Above- and below-ground biomass and production of lodgepole pine on sites with differing soil moisture regimes." Canadian Journal of Forest Research 19, no. 4 (April 1, 1989): 447–54. http://dx.doi.org/10.1139/x89-070.
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The distribution of tree biomass and the allocation of production was measured in four stands of lodgepole pine (Pinuscontorta var. latifolia Engelm.), two growing on sites with xeric soil moisture regimes and two on sites with mesic soil moisture regimes. At the time of sampling the stands were 70–78 years old. Aboveground biomass ranged from 116.5 Mg•ha−1 on one xeric site to 313.1 Mg•ha−1 on one mesic site. Stem biomass represented 68 and 73% of total tree biomass on the xeric and mesic sites, respectively. Total root biomass represented between 20 and 28% of total lodgepole pine biomass. Fine and small roots (<5 mm diameter) represented 4 and 1.5% of total tree biomass on the xeric and mesic sites, respectively. Total net primary production ranged from 7.9 Mg•ha−1•year−1 on the xeric sites to 11.9 Mg•ha−1•year−1 on the mesic sites. Stemwood production represented 20 and 27% of total net primary production on the xeric sites and 35% on both mesic sites. Belowground production represented 38 and 46% of total net primary production on the two mesic sites (4.5 and 5.5 Mg•ha−1•year−1, respectively) and 55 and 66% on the two xeric sites (4.3 and 6.3 Mg•ha−1•year−1, respectively). Fine and small roots represented 82–94% of belowground production. Production allocation was in the following order: fine and small roots > stems > foliage > coarse roots > branches, for all but the wettest site, where stem production exceeded fine and small root production.
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Tworkoski, T. J., M. S. Ross, and G. M. Hopper. "Analysis of chestnut and scarlet oak stump sprout growth." Canadian Journal of Forest Research 20, no. 1 (January 1, 1990): 112–16. http://dx.doi.org/10.1139/x90-016.
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This paper describes stem unit development of chestnut (Quercusprinus L.) and scarlet oak (Q. coccinea Muenchh.) stump sprouts growing on mesic and xeric sites in the Ridge and Valley physiographic region of southwest Virginia. On xeric sites, scarlet oak sprouts produced longer stem units than chestnut oak sprouts, whereas chestnut oak produced more flushes than scarlet oak. However, seasonal height growth was the same for both species. On xeric sites, 39% of the chestnut oaks flushed at least three times compared with 9% on the xeric site. Stem unit length among flushes of chestnut oak was similar, regardless of site. In oaks, stem unit analysis can be useful for evaluating growth components that may affect regenerative success and subsequent stand yield.
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Oswald, Scott W., and Doug P. Aubrey. "Xeric Tree Populations Exhibit Delayed Summer Depletion of Root Starch Relative to Mesic Counterparts." Forests 11, no. 10 (September 23, 2020): 1026. http://dx.doi.org/10.3390/f11101026.
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Research linking soil moisture availability to nonstructural carbohydrate (NSC) storage suggests greater NSC reserves promote survival under acute water stress, but little is known about how NSC allocation responds to long-term differences in water availabilty. We hypothesized populations experiencing chronic or frequent water stress shift carbon allocation to build greater NSC reserves for increased survival probability during drought relative to populations rarely experiencing water stress. Over a year, we measured soluble sugar and starch concentrations from branches, stems, and coarse roots of mature Pinus palustris trees at two sites differing in long-term soil moisture availability. Xeric and mesic populations exhibited a cycle of summer depletion-winter accumulation in root starch. Xeric populations reached a maximum root starch concentration approximately 1–2 months later than mesic populations, indicating delayed summer depletion. Xeric and mesic populations reached the same minimum root starch at similar times, suggesting extended winter accumulation for xeric populations. These results suggest seasonal mobilization from root starch is compressed into a shorter interval for xeric populations instead of consistently greater reserves as hypothesized. Seasonal trends differed little between xeric and mesic populations for starch and sugars, suggesting the importance of roots in seasonal carbon dynamics and the primacy of starch for storage. If roots are the primary organ for longterm storage, then our results suggest that whole-plant mobilization and allocation respond to chronic differences in water availability.
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Canadell, Josep, and Ferran Rodà. "Root biomass of Quercusilex in a montane Mediterranean forest." Canadian Journal of Forest Research 21, no. 12 (December 1, 1991): 1771–78. http://dx.doi.org/10.1139/x91-245.
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Biomass allocation to roots was studied in holm oak (Quercusilex L.), a dominant evergreen tree in broad-leaved sclerophyllous Mediterranean forests. The root systems of 32 single-stemmed holm oaks growing in shallow soils on largely unfissured bedrock were excavated in a mesic site and a xeric site in the Montseny Mountains (northeast Spain). Individual root:shoot biomass ratios (roots with diameter <1 cm not included) of single-stemmed trees were significantly higher in the xeric site (mean 0.45) than in the mesic site (mean 0.37), probably reflecting the lower water availability and higher light availability in the xeric site. It is concluded that single-stemmed holm oaks have higher root:shoot ratios than most temperate forest trees, particularly so when growing on a xeric site. Root:shoot ratios of single-stemmed trees were not linearly correlated with dbh. Allometric regressions of root biomass on dbh did significantly differ between sites. Roots <1 cm in diameter were sampled with soil cores in the mesic site. Holm oaks ≥5 cm dbh in a stand dominated by single-stemmed trees on the mesic site had an aboveground biomass of 160 t/ha and a belowground biomass of 63 t/ha. The belowground biomass was composed of 30 t/ha of root crowns plus roots >5 cm in diameter, 17 t/ha of roots 1–5 cm in diameter, and 16 t/ha of roots <1 cm in diameter. The xeric stand was dominated by multistemmed holm oaks with massive root crowns developed after repeated coppicing. Three multistemmed trees were excavated, yielding a mean root:shoot ratio of 1.2. Through resprouting from root crowns, managed or disturbed holm oak forests can accumulate a belowground biomass greater than that displayed aboveground: 91 t/ha (excluding roots <1 cm in diameter) and 79 t/ha, respectively, in our xeric stand.
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Dengler, Jürgen, Stefan Widmer, Eline Staubli, Manuel Babbi, Jamyra Gehler, Daniel Hepenstrick, Ariel Bergamini, et al. "Dry grasslands of the central valleys of the Alps from a European perspective: the example of Ausserberg (Valais, Switzerland)." Hacquetia 18, no. 2 (December 1, 2019): 155–77. http://dx.doi.org/10.2478/hacq-2019-0008.
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Abstract The upper Rhone valley in the Swiss canton of Valais is one of the driest and most continental of the inner-alpine valleys and harbours a rich xerothermic flora. We studied syntaxonomy and ecology of dry grasslands and their species richness patterns. In 2018 we recorded 28 vegetation plots (10 m2) and three nested-plot series of 0.0001 to 100 m2 on the south-facing slopes above the village of Ausserberg. Mean richness of all species ranged from 1.7 on 1 cm2 to 47.3 on 100 m2, with little contribution of bryophytes and lichens. The species-area relationship for total richness closely followed a power function. Modified TWINSPAN yielded a three-cluster solution, which could easily be matched with three orders of the class Festuco-Brometea: Stipo pulcherrimae-Festucetalia pallentis (xeric, rocky), Festucetalia valesiacae (xeric, non-rocky) and Brachypodietalia pinnati (meso-xeric). The subdivision of the xeric types into two orders is new for Swiss dry grasslands, where these types up to now had been joined in a single alliance Stipo-Poion within the Festucetalia valesiacae.
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Martin, Chris A., and Jean C. Stutz. "Growth of Sour Orange in Response to Mesic or Xeric Geographic Isolates of Glomus intraradices under Two Irrigation Frequency Regimens." HortScience 31, no. 4 (August 1996): 664c—664. http://dx.doi.org/10.21273/hortsci.31.4.664c.
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Sour orange (Citrus aurannum L.) seedlings were inoculated with geographic isolates of an endomycorrhizal fungus, Glomus intraradices Smith and Schneck, from a xeric (New Mexico) or mesic (Florida) climate or not inoculated as controls, and were grown for 5 months under high (soil water potential more than or equal to –0.1 MPa, irrigated once every 3 days) or low (more than or equal to –1.0 MPa, irrigated once every 12 to 15 days) irrigation frequency regimens. Similar leaf P concentrations were achieved in all plants by giving more P fertilizer to nonmycorrhizal plants than mycorrhizal plants. Plants inoculated with the xeric isolate had more arbuscules and fewer vesicles than those inoculated with the mesic isolate. Mycorrhizal fungi had little affect on plant growth under high irrigation frequency. Low irrigation frequency reduced plant growth compared with high irrigation frequency. Under low irrigation frequency, shoot and root growth increased for mycorrhizal plants; however, the magnitude of increase of shoot growth was greatest for plants inoculated with the xeric isolate. Additionally, low irrigation frequency was associated with a dramatic decrease in vesicle formation in roots inoculated with the mesic isolate. This study showed that sour orange plants especially benefited from inoculation with an isolate from a xeric climate under low irrigation frequency, independent of P nutrition.
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Heinemann, Karin, Thomas Kitzberger, and Thomas T. Veblen. "Influences of gap microheterogeneity on the regeneration of Nothofagus pumilio in a xeric old-growth forest of northwestern Patagonia, Argentina." Canadian Journal of Forest Research 30, no. 1 (February 1, 2000): 25–31. http://dx.doi.org/10.1139/x99-181.
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We experimentally examined the influences of within-gap environmental heterogeneity on regeneration patterns of Nothofagus pumilio (Poepp. & Endl.) Krasser near the xeric limit of its distribution in northern Patagonia, Argentina. Results from this xeric old-growth forest are compared with patterns previously described for the same species in mesic forests. Survival of N. pumilio seedlings beneath tree-fall gaps in this relatively xeric forest appears to be strongly influenced by moisture availability. Seedlings and saplings that have survived this demographic bottleneck are found at microsites where soil water potentials are higher, such as in the shady northern edges of tree-fall gaps (Ψ = -0.46 MPa compared with less than -0.6 MPa in other gap positions) and on coarse woody debris (Ψ = -0.29 MPa, compared with -0.51 MPa on the forest floor). Although gap creation in this dry N. pumilio forest is favorable to tree regeneration by releasing light resources, decreased water resources may switch the system from a light- to a water-limited system in some positions of the gap. This may explain the lack of regeneration of N. pumilio often observed after creation of large gaps towards the xeric end of its range and needs to be considered in the management of this important timber species.
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Wilkins, R. Neal, Wayne R. Marion, Daniel G. Neary, and George W. Tanner. "Vascular plant community dynamics following hexazinone site preparation in the lower Coastal Plain." Canadian Journal of Forest Research 23, no. 10 (October 1, 1993): 2216–29. http://dx.doi.org/10.1139/x93-275.
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Differential responses of vascular plant community compositions, diversities, and species-abundance distributions to hexazinone site preparation were evaluated on three 1-year-old clearcuts, each representing a point along a generalized edaphic gradient (xeric sandhill, mesic flatwoods, and hydric hammock). Foliar cover by species was sampled along four 20-m permanent line transects within each of three blocked replications of hexazinone treatments (0.0, 1.7, 3.4, and 6.8 kg/ha) at pretreatment and after the first and second growing seasons post-treatment. Cover by woody species decreased with increasing hexazinone rates on all sites (P < 0.05). Herbaceous vegetation recovered from first-season reductions to levels that did not vary with treatment (xeric sandhill and mesic flatwoods) or increased with increasing hexazinone rates (hydric hammock). Hexazinone tolerance by Gelsemiumsempervirens (L.) Ait.f. and Vaccinium spp. on the xeric sandhill and Ilexglabra (L.) Gray and G. sempervirens on the mesic flatwoods influenced diversity responses by woody and herbaceous vegetation. With increasing rates, herbaceous diversity decreased on the xeric sandhill, did not vary on the mesic flatwoods, and increased on the hydric hammock. Plant community responses to hexazinone were found to be functions of application rate, edaphic factors, adaptive strategies of resident species, and the presence or absence of hexazinone-tolerant species.
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Anella, Louis, and Thomas H. Whitlow. "PHOTOSYNTHESIS DURING INUNDATION FOR ACER RUBRUM L. POPULATIONS FROM CONTRASTING HABITATS." HortScience 29, no. 4 (April 1994): 247d—247. http://dx.doi.org/10.21273/hortsci.29.4.247d.
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Changes in photosynthesis and root morphology during flooding were studied in container-grown 2- to 3-year-old Acer rubrum L. saplings. The seed was collected from opposite ends of a hydrologic gradient: two upland xeric sites [the George Washington National Forest in Page County, Va. (38°25'N, 78°35'W), and the Robinson Forest in Perry County, Ky. (37 °9'N, 83°7'W)] and a floodplain hydric site [the Presquile National Wildlife Refuge along the James River in Chesterfield County, Va. (37°21'N, 77°16'W)]. Each xeric site, containing various half-sib families (maternal parent known, paternal parent from one or more sources), was compared to a different hydric site half-sib family. After 1 week of flooding, the xeric-site trees had lower net photosynthesis than the hydric-site trees and remained significantly lower for the duration of the study. After an initial drop, hydric-site plants showed a recovery in net photosynthesis, indicating a greater ability to acclimate to a flooding stress. Seventy-one percent of the hydric-site plants developed adventitious roots and all retained their leaves. Xeric-site plants did-not develop adventitious roots and 61% were defoliated after 60 days of continuous flooding. The results indicate ecotypic differentiation in physiological response between Acer rubrum populations collected from opposite ends of a hydrologic gradient.
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Hadly, Elizabeth Anne. "Influence of Late-Holocene Climate on Northern Rocky Mountain Mammals." Quaternary Research 46, no. 3 (November 1996): 298–310. http://dx.doi.org/10.1006/qres.1996.0068.
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An exceptionally rich paleontological site containing thousands of mammalian fossils and well-dated with 18 radiocarbon samples provides evidence of late-Holocene ecological response to climatic change in northern Yellowstone National Park, Wyoming. The mammalian fauna, composed of 10,597 identified specimens, shows surprising affinity to the local habitat with little evidence of long-distance transport of faunal elements, thus revealing the faithfulness of a fossil site to the community from which it is derived. The mammals illustrate ecological sensitivity to a series of mesic to xeric climatic excursions in the sagebrush-grassland ecotone during the past 3200 yr. From 3200 cal yr B.P. to a maximum of 1100 cal yr B.P., the species composition of mammals indicates wetter conditions than today. Beginning about 1200 cal yr B.P., the fauna becomes more representative of xeric conditions with maxima in xeric-indicator taxa and minima in mesic-indicator taxa, concordant with the Medieval Warm Period (circa 1000 to 650 yr B.P.). Cooler, wetter conditions which prevailed for most of the Little Ice Age (700 to 100 yr B.P.) in general correspond to a return to a more mesic mammalian fauna. A warm period within the Little Ice Age is documented by a xeric fauna. These data show that mammalian ecological sensitivity to climatic change over this intermediate time scale holds promise for predictions about the impacts of future global warming.
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Iorgu, Ionuţ Ştefan, and Elena Iulia Iorgu. "First Record of Saga pedo (Orthoptera: Tettigoniidae) in Muntenia (Southern Romania)." Travaux du Muséum National d’Histoire Naturelle “Grigore Antipa” 58, no. 1-2 (April 1, 2016): 33–35. http://dx.doi.org/10.1515/travmu-2016-0004.
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Abstract Although occupying a vast area, the distribution range of Saga pedo is f ragmented and populations are small, severely threatened by habitat destruction and pollution. In Romania, the species is known to occur in xeric and semi–xeric meadows from Dobrogea, Eastern Moldavia, Transylvania and Banat. During a short trip in late June 2014, we found three nymphs of Saga pedo at Berca Mud Volcanoes, the first record of the species in the historical region of Muntenia (Southern Romania).
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Arakawa, Kazuharu. "Simultaneous Metabarcoding of Eukaryotes and Prokaryotes to Elucidate the Community Structures within Tardigrade Microhabitats." Diversity 12, no. 3 (March 20, 2020): 110. http://dx.doi.org/10.3390/d12030110.
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Tardigrades are microscopic invertebrates that can withstand complete desiccation, but their interspecies interactions with prokaryotes and eukaryotes within their microhabitat remain relatively unexplored. Here, I utilized combined metabarcoding of eukaryotes and prokaryotes to simultaneously identify entire community structures within xeric and mesic mosses that harbor tardigrades. The populations of organisms within the microecosystems were successfully determined in 45 xeric moss samples and 47 mesic moss samples. Organismal composition was largely consistent regardless of the moss/lichen substrate, but significantly varied in the two tested locations, possibly because of the differences in environmental humidity. Xeric mosses containing xerophilic tardigrades and other anhydrobiotic invertebrates tended to have significantly limited biological diversity and prokaryotic population dominated by cyanobacteria, suggesting a selection due to extreme desiccation. A combined metabarcoding approach to identify both eukaryotes and prokaryotes can successfully elucidate community structures within microscopic ecosystems, and this can be a potential approach to study the microecology of meiofauna, including tardigrades.
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Akkemik, Ünal, Nevriye Neslihan Acarca Bayam, and Ferdi Akarsu. "An approach to compare the environmental conditions of Acer in the Miocene and in the modern flora of Turkey, based on wood anatomy." Acta Palaeobotanica 58, no. 2 (December 1, 2018): 209–17. http://dx.doi.org/10.2478/acpa-2018-0010.
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AbstractIn this study, xeromorphy ratios were calculated for Acer L. (maple) fossil woods in order to infer the precipitation conditions in the Miocene at the sites of the fossils, based on a comparison with the xeromorphy ratios of selected extant Acer species. The four studied petrified wood samples came from three localities of the Galatean Volcanic Province in Turkey: Kozyaka village (Bolu Province, Seben District), İnözü Valley (Ankara Province, Beypazarı District), and Kıraluç precinct between Nuhhoca and Dağşeyhler villages (Ankara Province, Beypazarı District). The calculated xeromorphy ratios ranged from 3 to 18 for the present-day wood and from 13 to 19 for the early Miocene wood. Values over 10 (11–18) represent xeric conditions; the lower values (3–7) indicate mesic conditions in modern Acer woods. The xeromorphy ratios of the Miocene wood indicate xeric conditions; we conclude that the sites of the fossil Acer woods were xeric, very similar to the modern Acer woodlands of central and southern Anatolia.
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Dunlap, J. M., R. F. Stettler, and P. E. Heilman. "Genetic variation and productivity of Populustrichocarpa and its hybrids. VIII. Leaf and crown morphology of native P. trichocarpa clones from four river valleys in Washington." Canadian Journal of Forest Research 25, no. 10 (October 1, 1995): 1710–24. http://dx.doi.org/10.1139/x95-185.
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A common-garden study of Populustrichocarpa Torr. & Gray was initiated in 1985, when clonal material from 128 trees was collected from sites distributed along two mesic (Hoh, Nisqually) and two xeric (Dungeness, Yakima) river valleys. This material was grown for 1 year at Puyallup, Wash. In spring 1986, cuttings from this material were used to establish two replicate plantations, one at Puyallup and the other at Wenatchee, Wash. Data were collected from a subset of 80 clones on 8 single-leaf and 14 crown traits after two growing seasons. Analyses of variance revealed significant (p ≤ 0.10) differences among rivers in nearly all single-leaf traits by the second year at both plantations. Two-year leaf sizes at Puyallup significantly declined in this order: Hoh (388 cm2) > Nisqually > Dungeness > Yakima (194 cm2). At Wenatchee, a similar mesic > xeric pattern was found among river sources, but leaves were smaller there. When grown at Puyallup, leaves of clones from lower elevations in the Yakima valley were significantly (p ≤ 0.10) smaller, lighter, thinner, and weighed less per unit area than upper elevation clones. Chi-square tests showed that abaxial leaf surfaces were greener in Yakima trees than in trees from other locations, especially in those from the the lower Yakima valley. In the crown traits of trees grown in Puyallup, river and clone-within-site-within-river effects were significant for all traits, whereas site-within-river effects were significant for only 8 traits. Mesic-origin trees were significantly larger in size traits, e.g., branch length, than xeric-origin trees. Trees from the Yakima drainage system were leafier and branchier (p ≤ 0.10) than both Nisqually and Hoh trees. Values for most crown traits were greater (p ≤ 0.10) in the xeric, lower Yakima clones than in the mesic, upper Yakima clones. These mesic-xeric differences were similar for Dungeness trees, although there were few significant differences between the lower and upper elevational groups. Single-leaf and crown traits of trees from the four river valleys seem to be adapted to the respective mesic and xeric conditions of the source environments. Within the Yakima river valley, a sharp change in leaf and crown traits and in atmospheric moisture levels coincide midway along the transect, suggesting the presence of a steep selection gradient in the Bristol Canyon area.
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Lighton, J., and D. Berrigan. "Questioning paradigms: caste-specific ventilation in harvester ants, Messor pergandei and M. julianus (Hymenoptera: Formicidae)." Journal of Experimental Biology 198, no. 2 (February 1, 1995): 521–30. http://dx.doi.org/10.1242/jeb.198.2.521.
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Do developmental constraints in ant colonies limit gas exchange strategies to those displayed by female alates (presumptive queens)? In the xeric harvester ant genus Messor, we found that M. pergandei and M. julianus female alates ventilated highly discontinuously, as predicted, but M. julianus workers ventilated less discontinuously and M. pergandei workers (which occur in more xeric habitats) ventilated continuously. We present the salient characteristics of the discontinuous ventilation cycles of the species and the manner in which they are modulated by CO2 emission rates at a single temperature (24 °C). We demonstrate that, in M. julianus workers, open-spiracle phase CO2 emission rate only slightly exceeds overall CO2 emission rate, making discontinuous ventilation marginal, a state extrapolated in M. pergandei to continuous ventilation. However, workers are plainly capable of far greater rates of CO2 emission than when inactive at 24 °C, so the lack of discontinuous ventilation in M. pergandei under normoxic conditions is not likely to be imposed by physiological constraints and may, in fact, be a response to its xeric environment. We hypothesize ­ aside from phylogenetic effects ­ that discontinuous ventilation occurs primarily in insects that may experience hypoxic and hypercapnic conditions, such as ant queens during claustral colony foundation and perhaps workers within the nest environment; that discontinuous ventilation is not necessarily essential to reduce respiratory water loss; and that it will not necessarily occur in castes or species routinely exposed to xeric but normoxic conditions.
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Peterson, Cathleen A., L. Brooke McDowell, and Chris A. Martin. "286 Plant Life Form Frequency, Diversity, and Irrigation Application in Urban Residential Landscapes." HortScience 34, no. 3 (June 1999): 491E—491. http://dx.doi.org/10.21273/hortsci.34.3.491e.
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Heightened awareness of ecological concerns have prompted many municipalities to promote water conservation through landscape design. In central Arizona, urban residential landscapes containing desert-adapted plant species are termed xeriscapes, while those containing temperate or tropical species and turf are termed mesoscapes. Research was conducted to ascertain landscape plant species diversity, tree, shrub, and ground cover frequency; landscape canopy area coverage; and monthly irrigation application volumes for xeric and mesic urban residential landscapes. The residential urban landscapes were located in Tempe and Phoenix, Ariz., and all were installed initially between 1985 and 1995. Although species composition of xeric and mesic landscapes was generally dissimilar, both landscape types had comparable species diversity. Mesoscapes had significantly more trees and shrubs and about 2.3 times more canopy area coverage per landscaped area than xeriscapes. Monthly irrigation application volumes per landscaped surface area were higher for xeriscapes. Even though human preference for xeric landscape plants may be ecological in principle, use of desert-adapted species in central Arizona urban residential landscape settings might not result in less landscape water use compared with mesic landscapes.
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Williams, C. Jason, Frederick B. Pierson, Peter R. Robichaud, and Jan Boll. "Hydrologic and erosion responses to wildfire along the rangeland–xeric forest continuum in the western US: a review and model of hydrologic vulnerability." International Journal of Wildland Fire 23, no. 2 (2014): 155. http://dx.doi.org/10.1071/wf12161.
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The recent increase in wildfire activity across the rangeland–xeric forest continuum in the western United States has landscape-scale consequences in terms of runoff and erosion. Concomitant cheatgrass (Bromus tectorum L.) invasions, plant community transitions and a warming climate in recent decades along grassland–shrubland–woodland–xeric forest transitions have promoted frequent and large wildfires, and continuance of the trend appears likely if warming climate conditions prevail. These changes potentially increase overall hydrologic vulnerability by spatially and temporally increasing soil exposure to runoff and erosion processes. Plot and hillslope-scale studies demonstrate burning may increase event runoff or erosion by factors of 2–40 over small-plot scales and more than 100-fold over large-plot to hillslope scales. Reports of flooding and debris flow events from rangelands and xeric forests following burning show the potential risk to natural resources, property, infrastructure and human life. We present a conceptual model for evaluating post-fire hydrologic vulnerability and risk. We suggest that post-fire risk assessment of potential hydrologic hazards should adopt a probability-based approach that considers varying site susceptibility in conjunction with a range of potential storms and that determines the hydrologic response magnitudes likely to affect values-at-risk. Our review suggests that improved risk assessment requires better understanding in several key areas including quantification of interactions between varying storm intensities and measures of site susceptibility, the varying effects of soil water repellency, and the spatial scaling of post-fire hydrologic response across rangeland–xeric forest plant communities.
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McDowell, L. Brooke, and Chris A. Martin. "596 Landscape Design and History Affect Urban Plant Gas Exchange Parameters." HortScience 34, no. 3 (June 1999): 549E—550. http://dx.doi.org/10.21273/hortsci.34.3.549e.
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Effects of landscape design and land use history on gas exchange parameters were evaluated for woody plants in a factorial site matrix of formerly desert or agricultural land uses and xeric or mesic residential landscape designs within the metropolitan area of Phoenix, Ariz. Remnant Sonoran Desert sites and an alfalfa agricultural field functioned as controls. Residential landscapes and the alfalfa field were irrigated regularly. Monthly instantaneous measurements of maximum leaf and stem carbon assimilation (A), conductance (gs), and transpiration (E) were made within three replicates of each site type during 1998 and 1999. Measurements were repeated monthly on three woody plant life forms: trees, shrubs, and ground covers. Assimilation fluxes were not related to former land use, but were lower for plants in xeric compared with those in mesic landscapes. Transpiration fluxes were higher for plants in formerly agricultural sites than in formerly desert sites, and were lower in xeric than in mesic landscape design. Compared with plants in residential landscapes, A and E fluxes were generally higher for plants in the agricultural control sites and were lower for plants at the desert control sites. Plant instantaneous transpiration efficiency (ITE = A/E) was higher in formerly agricultural sites than in formerly desert sites but was not affected by landscape design. Patterns of A, gs, and shoot temperature at irrigated sites suggest that maximum plant carbon assimilation was not limited by shoot conductance but was more responsive to shoot temperature. Similarities in patterns of ITE between plants in the different landscape design types suggest that xeric and mesic landscape plants do not differ in terms of water use efficiency.
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Sekulić, Dimitrije, Branko Karadžić, Nevena Kuzmanović, Snežana Jarić, Miroslava Mitrović, and Pavle Pavlović. "Diversity of Ostrya carpinifolia Forests in Ravine Habitats of Serbia (S-E Europe)." Diversity 13, no. 2 (February 3, 2021): 59. http://dx.doi.org/10.3390/d13020059.
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We investigated vegetation in ravine habitats of Serbia, in order to classify hop hornbeam (Ostrya carpinifolia Scop.) forests in syntaxonomic terms, assess the effects of environmental factors on their floristic differentiation, and detect the biodiversity components of the analyzed communities. Both K-means clustering and Bayesian classification revealed five ecologically interpretable groups of forests that belong to the alliances Ostryo carpinifoliae-Fagion sylvaticae, Ostryo carpinifoliae-Tilion platyphylli, Fraxino orni-Ostryion carpinifoliae, Pseudofumario albae-Ostryion carpinifoliae, and Achilleo ageratifoliae-Ostryion carpinifoliae. Canonical correspondence analysis indicated that these alliances are clearly differentiated along a combined light–moisture gradient (from shade and mesic to sunny and xeric variants). The alpha diversity increases from xeric to mesic alliances. A lower alpha diversity in xeric forests may be explained by the stress conditions that prevent mesic species from colonizing the saxatile habitats. Extremely high—almost the greatest possible—values of both the species turnover and beta diversity were detected in all variants of the analyzed forests. Such high diversity may be the result of the strong environmental gradients in ravine habitats. The investigated forests represent an important pool of rare, paleo-endemic species that survived Quaternary glaciations in ravine refugia.
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Schroeter, Burkhard, T. G. Allan Green, Ana Pintado, Roman Türk, and Leopoldo G. Sancho. "Summer activity patterns for mosses and lichens in Maritime Antarctica." Antarctic Science 29, no. 6 (August 1, 2017): 517–30. http://dx.doi.org/10.1017/s095410201700027x.
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AbstractWithin Antarctica there are large gradients both in climate and in vegetation which offer opportunities to investigate links between the two. The activity (% total time active) of lichens and bryophytes in hydric and xeric environments was monitored at Livingston Island (62°39'S). This adds a northern site with a maritime, cloudy climate to previous studies in the southern Antarctic Peninsula and the Dry Valleys (78°S). Annual activity increases northwards from less than 1% to nearly 100%. There is a major and consistent difference between hydric sites which, with snow melt, can be 100% active in summer months even in the Dry Valleys, and xeric sites which, depending on precipitation, rarely exceed 80% activity even at Livingston Island. Mosses dominate hydric sites and lichens the xeric sites all along the gradient. Mean temperatures when active are 2–4°C at all sites, as liquid water is required. Light is a potential major stress reaching 880 µmol m-2s-1when active in continental sites. The lack of extremes in temperatures and light combined with high activity levels means that summer at Livingston Island is one of the better sites for lichen and bryophyte growth in the world.
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Evgen’ev, M. B., D. G. Garbuz, V. Y. Shilova, and O. G. Zatsepina. "Molecular mechanisms underlying thermal adaptation of xeric animals." Journal of Biosciences 32, no. 3 (April 2007): 489–99. http://dx.doi.org/10.1007/s12038-007-0048-6.
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Raj, Anup, and Poonam Sharma. "Floristic diversity of arboreal communities in the high altitude deserts of Ladakh." Indian Journal of Forestry 33, no. 4 (December 1, 2010): 533–36. http://dx.doi.org/10.54207/bsmps1000-2010-07yph1.
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Analysis of woody components of 4 communities in Nubra valley of Ladakh revealed that Hippophae rhamnoides was the most dominant species sharing 31 per cent of total importance value. Across the communities within landscape relative dominance of this species decreased from 77.76 per cent on most hydric sites (along river bank) to merely 0.27 per cent on most xeric sites (dry rocks). On the other hand, relative dominance of Ephedra gerardiana and Berberis ulicina increased with increasing aridity of sites. Productivity-diversity relationship followed unimodal curve which peaked at sites along streams. Maximum species turnover rate was found across the sites along steams while the most xeric sites were more uniform within.
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DE S. MENDONÇA, JR., MILTON. "Galling arthropod diversity in the subtropical neotropics: Espinilho savannah and riparian forests compared." Revista Colombiana de Entomología 37, no. 1 (June 30, 2011): 111–16. http://dx.doi.org/10.25100/socolen.v37i1.9053.
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Xeric sites with scleromorphic vegetation appear to have higher gall-inducing arthropod richness as revealed in studies of local faunas across the world, and the harsh environment hypothesis (HEH) was proposed to explain this. However, plant richness also seems to influence galling arthropod richness positively, which appears paradoxical on a biogeographical scale. To test the HEH in southern Brazil, a sampling regime distinct from the usual local survey was adopted: eight transects were sampled during 90 min counting all galls; this was repeated three times over one year for the same transects. Xeric espinilho savannah (five transects) and mesic Uruguay River riparian forests (three transects) in subtropical Brazil were compared. Fifty-nine gall morphotypes on 15 host families were recognized out of 12,355 individual galls. Riparian forests were richer (individual-based rarefaction) and had higher gall equitabilities (bootstrapped 95% CIs); this contradicted the HEH. The plant richness hypothesis was generally supported because forests were recorded as richer in both plants and host plants. Vegetation types had different galling and host plant compositions; the latter may drive the former. Species pools appear distinct among environments, even adjacent ones, given the low similarities found. This further negates the ecological process of preference for xeric sites proposed in the HEH.
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Dai, Jingyu, Surui Lu, Yang Qi, and Hongyan Liu. "Tree-to-Shrub Shift Benefits the Survival of Quercus mongolica Fisch. ex Ledeb. at the Xeric Timberline." Forests 13, no. 2 (February 5, 2022): 244. http://dx.doi.org/10.3390/f13020244.
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Woody species are either trees or shrubs, with the exception of approximately 9.2% “trub” species exhibiting both tree and shrub growth forms. Little is known thus far about the ecological importance of plant growth-form plasticity under a drying climate. Quercus mongolica Fisch. ex Ledeb., a dominant tree species of temperate forests in East Asia, typically shows tree-to-shrub growth-form shifts at the xeric timberline and is suitable to test whether growth-form plasticity can physiologically benefit plant drought acclimation. We quantified the tree architecture, drought stress, physiological drought tolerance, and nonstructural carbohydrates of Q. mongolica trees and shrubs on the opposite slope of the same mountain at the xeric timberline in July 2018. Compared with Q. mongolica trees on shady slopes, the shrubs on sunny slopes had less available water to use and were more severely threatened by drought. Moreover, the shrubs had stronger tolerance to drought but still tended to have less nonstructural carbohydrate accumulation. The tree-to-shrub shift effectively benefits the survival of Q. mongolica under a dry climate and may strongly contribute to forest dynamics and even fire regimes under climate drying, especially for sensitive ecosystems such as the xeric timberline, which will be vulnerable under future climate change scenarios.
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Hochkirch, A., A. C. Gärtner, and T. Brandt. "Effects of forest-dune ecotone management on the endangered heath grasshopper, Chorthippus vagans (Orthoptera: Acrididae)." Bulletin of Entomological Research 98, no. 5 (April 21, 2008): 449–56. http://dx.doi.org/10.1017/s0007485308005762.
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AbstractDry, oligotrophic ecosystems are highly threatened in Europe due to massive changes in land use and eutrophication. The conservation of these xeric habitats has received much attention, whereas the ecotones between xeric habitats and other habitat types are often disregarded. One species which mainly inhabits the transition zone between pine forests and adjacent xeric habitats is the heath grasshopper, Chorthippus vagans. This species is endangered in large parts of Europe. One of the largest populations in northern Germany is found on a degraded inland dune near Hanover. This population is threatened by dense growth of deciduous trees and litter accumulation. We analyzed changes in the distribution of this population after the implementation of conservation measures (thinning out the forest and removal of leaf litter). Moreover, we examined dispersal distances of the species in order to assess its colonization potential. We also studied the microhabitat preferences of C. vagans to assess key factors influencing its local distribution. Our data show a substantial growth in population size, which might be a consequence of the conservation measures. New patches on the dune were colonized, promoting dispersal between the subpopulations. We propose that restoration of forest-dune ecotones should be considered more often in landscape planning and conservation management.
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Laiviņš, Māris, Agnese Priede, Dārta Kaupe, and Andis Lazdiņš. "Succession of Xeric Calcareous Grassland Toward Thermophilous Oak Forest: The Case of Abava Valley, West Latvia." Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences. 75, no. 4 (August 1, 2021): 268–81. http://dx.doi.org/10.2478/prolas-2021-0040.
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Abstract The succession of semi-natural xeric calcareous grassland plant communities toward deciduous forest communities is poorly studied in Latvia. There is insufficient knowledge on the natural transformation of dry calcareous grasslands of Festuco-Brometea into thermophilous quasi-climax oak forest communities of Quercetea pubescentis that are very rare in Latvia. In this paper, a geobotanical study is presented that included studies of soils, tree age, spatial pattern of trees, vegetation composition of different succession stages, and analysis of environmental factors. The study was conducted in the Abava Valley, West Latvia, an area that is unique with species-rich xeric calcareous Festuco-Brometea grasslands, thermophilous oak forests dominated by Quercus robur, and intermediate secondary succession stages with young to medium-aged Juniperus communis and Pinus sylvestris formations.
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Rivera-Milán, Frank F. "Transect Surveys of Columbid Nests on Puerto Rico, Vieques, and Culebra Islands." Condor 103, no. 2 (May 1, 2001): 332–42. http://dx.doi.org/10.1093/condor/103.2.332.
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Abstract I conducted transect surveys of pigeon and dove (Columbidae) nests on Puerto Rico, Vieques, and Culebra islands. Nest detection probability and density differed between study areas in January–August 1991 and 1992. Nest detection probability and density did not differ between years or among species, so I used transect data from a larger study (1986–1999) to assess the relationships between nest density and rainfall, food abundance, food diversity, and predator abundance along transects. Food abundance was the most important predictor of annual changes in nest density on the surveyed transects in mesic and xeric habitats during May–June 1986–1999. Positive correlations of annual nest density estimates suggested parallel responses among columbid species to similar or covarying resources in mesic and xeric habitats.
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Szanyi, Szabolcs, Ludvig Potish, István András Rácz, Zoltán Varga, and Antal Nagy. "Orthoptera assemblages of the relict meadows of the Szernye marsh area (West Ukraine: Transcarpathia)." Biologia 76, no. 10 (May 10, 2021): 2931–40. http://dx.doi.org/10.1007/s11756-021-00768-z.
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AbstractOrthoptera assemblages were sampled between 2012 and 2014 on six grasslands in marginal part of the former Szernye Marsh (Bereg Lowland, Transcarpathia, West Ukraine). 24 species in 1306 individuals were observed which is about the half of the Orthoptera species known from the Bereg Lowland. The bulk of the assemblages is formed by generalist chortobiont species (62.5%), while thamnobionts, connected with tall forb and/or shrubby vegetation, also reach a relatively high frequency (29.1%). According to the biogeographical composition, the Euro-Siberian species were predominating (58.3%), combined with only scarce presence of West Palearctic and Mediterranean species. The multivariate analysis did not show any clear subdivision according to the a priori vegetation types with the exception of the xeric habitats. This assemblage type were characterised by a low species number (7–12) and very high frequency of one or at least two dominant species which were common in all types of studied habitats. Although their subdominant species differed from the other two assemlage types but they could not be referred as true character species. Thus the studied xeric habitats are not such true xeric grasslands as the sandy and saline grasslands of the Pannonian lowland. The main natural value of the area is preseved by semi-natural humide and transitional habitat types, which can be conserved by yearly alternating mowing and preserving the mosaic structure with some corridors among them.
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Velev, Nikolay, and Kiril Vassilev. "Management Regimes within Syntaxa of Semi-Natural Grasslands in West Bulgaria." Hacquetia 13, no. 1 (June 1, 2014): 191–204. http://dx.doi.org/10.2478/hacq-2014-0003.
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Abstract This study focuses on mesic and xeric grasslands of mostly secondary origin, and that are influenced by human activity. Mesic grasslands are traditionally used for hay-making, and xeric ones for pastures. Over the last 20 years, livestock farming in Bulgaria has significantly declined so that less grass is needed. Many types of grasslands are no longer used and lots of abandoned fields can be found nowadays in Bulgaria. The analyses in this study are based on 868 releves collected on xeric and mesic grasslands according to the methodological approach of Braun- Blanquet. As a result, five alliances within two classes are recognized: the class Festuco-Brometea, represented by three alliances, namely Cirsio-Brachypodion pinnati, Chrysopogono-Danthonion calycinae and Festucion valesiacae, and the class Molinio-Arrhenatheretea, represented by two alliances, namely Arrhenatherion elatioris and Cynosurion cristati. The majority of the managed grasslands are situated in close proximity to settlements. Most of the abandoned areas (30%) are found within Cirsio-Brachypodion alliance. These grasslands are characterized by the highest values of total cover of vegetation. They are located in the most distant and least accessible areas. If use is not resumed, all the abandoned grasslands will be under threat of extinction in the near future. At the same time, many arable lands have been abandoned and turned into grasslands by the processes of secondary succession.
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Groeschl, DA, JE Johnson, and DW Smith. "Wildfire Effects on Forest Floor and Surface Soil in a Table Mountain Pine-Pitch Pine Forest." International Journal of Wildland Fire 3, no. 3 (1993): 149. http://dx.doi.org/10.1071/wf9930149.
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Wildfire plays a dominant role in creating die environmental and biological conditions necessary for the natural regeneration of mixed Pinus pungens Lamb. (Table Mountain pine)-Pinus rigida Mill. (pitch pine) forests. This study of forest floor and surface soil properties following a mid-July wildfire in these forests in the Shenandoah National Park revealed significant reductions in nutrient contents. Prolific regeneration of the pines occurred following the fire, with over 9,000 seedling/ha tallied in high severity areas, compared with less than 800 seedlings/ha in unburned areas. It is hypothesized that fire degrades site quality and sets back the site succession process so that the pines are better able to compete with invasive, xeric-site deciduous species like oaks and maples. Adjacent, unburned xeric-site oak forests dominate on more moist and fertile sites.
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Khan, Aziz, Sultan Mehmood, Israr Ahmad, Ashfaq A. Khan, Sami Ullah, and Malik Shuaib. "ANTIMICROBIAL AND PHYTOTOXIC ACTIVITIES OF FEW IMPORTANT XERIC PLANTS." Pakistan Journal of Phytopathology 29, no. 1 (July 12, 2017): 29. http://dx.doi.org/10.33866/phytopathol.029.01.0319.
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The present study was conducted to record and report the biological activities of four selected xerophytes species of District Bannu. Phytotoxic effect of Calligonum polygonoides, Sueda fruticosa, Peganum harmala (L.) and Rosa brunonii was conducted by the germination of Cucumus sativus, Brassica olerace, Helianthu annus and Abelmoschus esculentus similarly antibacterial and antifungal activities were also carried out in libratory by using of various strains of bacteria and fungal such as Bacillus subtilis and Escherichia colli, Aspergillus niger and Aspergills flavos. All of the selected plants have inhibitory effect on bacteria growth. In this study the effect of different concentration (.5mg/ml, 10mg/ml) of shade dry leaf methanol extract of Calligonum polygonoides, Sueda fruticos, Peganum harmala (L.) and Rosa brunonii on various strains of bacteria and fungi were investigated. The results showed that the methanol extract of Calligonum polygonoides, Rosa brunonii and Peganum harmala (L.). inhibit the growth of bacteria and fungi just like antibiotic but Sueda fruticosa have little inhibitory effect on Bacterial and fungal strain. Maximum growths of bacteria and fungi were occurred at positive control Petri dish (DMSO); growth were not observe at Petri plate of Tetracycline and Terbinofine test tube.Growth of bacteria and fungi was not observe in higher concentration Rosa brunonii and Calligonum polygonoides on various strains of bacteria and fungi.
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Michelette, Elen R. F., and João M. F. Camargo. "Bee-plant community in a xeric ecosystem in Argentina." Revista Brasileira de Zoologia 17, no. 3 (September 2000): 651–65. http://dx.doi.org/10.1590/s0101-81752000000300011.
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Thomas, E. Perry, Dean W. Blinn, and Paul Keim. "Do xeric landscapes increase genetic divergence in aquatic ecosystems?" Freshwater Biology 40, no. 4 (December 1998): 587–93. http://dx.doi.org/10.1046/j.1365-2427.1998.00357.x.
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Davidowitz, Goggy. "Does precipitation variability increase from mesic to xeric biomes?" Global Ecology and Biogeography 11, no. 2 (March 2002): 143–54. http://dx.doi.org/10.1046/j.1466-822x.2002.00271.x.
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Houdeshel, C. Dasch, Christine A. Pomeroy, and Kevin R. Hultine. "Bioretention Design for Xeric Climates Based on Ecological Principles1." JAWRA Journal of the American Water Resources Association 48, no. 6 (August 10, 2012): 1178–90. http://dx.doi.org/10.1111/j.1752-1688.2012.00678.x.
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Aguilera-Miller, Eduardo Felipe, and Sergio Ticul Álvarez-Castañeda. "Review of philopatry and its strategy in xeric environments." Therya 10, no. 1 (January 30, 2019): 39–44. http://dx.doi.org/10.12933/therya-19-754.
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Olson, Storrs L. "Muscis Hawaiiensis Mantissae I: Two weedy species of Bryum new to the archipelago." Bryophyte Diversity and Evolution 17, no. 1 (December 31, 1999): 129–30. http://dx.doi.org/10.11646/bde.17.1.15.
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Bryum lisae var. cuspidatum and B. radiculosum were collected in xeric, lowland habitats on the islands of Oahu and Kauai, respectively, and constitute the first records for either species for the Hawaiian archipelago.
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Harzé, Mélanie, Grégory Mahy, and Arnaud Monty. "Drought stress inducing intraspecific variability in Potentilla tabernaemontani (Rosaceae), a calcareous grassland species." Plant Ecology and Evolution 151, no. 1 (March 28, 2018): 153–58. http://dx.doi.org/10.5091/plecevo.2018.1347.
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Background and aims – Calcareous grasslands are among the most species-rich habitats in Western Europe. Populations of plant species characterizing these ecosystems are naturally submitted to high variability in environmental conditions at the very local scale, resulting in pronounced variation in functional traits. Individuals located on xeric parts of calcareous grasslands are characterized by plant traits that potentially ensure more successful performance under stressful conditions. In the context of increased frequency of summer heat waves based on climate change, our aim was to determine a possible intraspecific variability in drought response among individuals of one calcareous grassland plant species.Methods – A greenhouse experiment was set up to follow survival of Potentilla tabernaemontani Asch. individuals according to their habitat of origin (xeric or mesic parts of Belgian calcareous grasslands) and the treatment applied (low or high drought stress).Key results – The results demonstrated that individuals originating from xeric parts survived drought stress better than individuals from mesic parts of calcareous grasslands. Specific leaf area (SLA) of all individuals was very low in the experiment, allowing them to decrease water loss during drought stress. Leaf production was lower for individuals exposed to high drought stress while flower production was higher. That potentially expressed a trade-off between tolerance to water stress, individual growth and reproduction. Conclusions – Local scale environmental heterogeneity deserves to be considered in conservation and restoration plans as it induces intraspecific functional variability between individuals and impacts individuals’ ability to survive drought stress.
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Bergeron, Yves, and Daniel Gagnon. "Age structure of red pine (Pinusresinosa Ait.) at its northern limit in Quebec." Canadian Journal of Forest Research 17, no. 2 (February 1, 1987): 129–37. http://dx.doi.org/10.1139/x87-024.
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At the northern limit of red pine (Pinusresinosa Ait.) fire may be of critical importance in determining the persistence of red pine and its restriction to islands and shores of lakes. The objectives of the study were to document the distribution pattern of red pine populations of the Lake Duparquet area in northwestern Quebec and to analyze the age structure and fire history of the populations. The combined age structure of 22 red pine populations is balanced and uneven aged, with two periods of increased recruitment from 1805 to 1864 and from 1925 to 1974. The analysis of individual populations indicates that they can be separated into three groups associated with specific site conditions: (i) uneven-aged populations with constant recruitment occurring on xeric sites, (ii) even-aged populations without regeneration occurring on mesic sites, and (iii) uneven-aged populations, showing both a constant recruitment and peak periods of regeneration, occurring on sites with xeric and mesic portions. Although all fires registered, lethal and nonlethal, are generally asynchronous between sites, the fires of 1825 and 1944 seem to have affected large areas of the lake. Two mechanisms for the maintenance of red pine were detected: self-regeneration of populations resistant to fires on xeric sites, and the transitory colonization of mesic sites by populations susceptible to lethal fires and established by seed from distant seed sources. Red pine may be restricted to lake landscapes because of the abundance of sites protected from lethal fires.
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Farji-Brener, Alejandro G., Luciana Elizalde, Hermógenes Fernández-Marín, and Sabrina Amador-Vargas. "Social life and sanitary risks: evolutionary and current ecological conditions determine waste management in leaf-cutting ants." Proceedings of the Royal Society B: Biological Sciences 283, no. 1831 (May 25, 2016): 20160625. http://dx.doi.org/10.1098/rspb.2016.0625.
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Adequate waste management is vital for the success of social life, because waste accumulation increases sanitary risks in dense societies. We explored why different leaf-cutting ants (LCA) species locate their waste in internal nest chambers or external piles, including ecological context and accounting for phylogenetic relations. We propose that waste location depends on whether the environmental conditions enhance or reduce the risk of infection. We obtained the geographical range, habitat and refuse location of LCA from published literature, and experimentally determined whether pathogens on ant waste survived to the high soil temperatures typical of xeric habitats. The habitat of the LCA determined waste location after phylogenetic correction: species with external waste piles mainly occur in xeric environments, whereas those with internal waste chambers mainly inhabit more humid habitats. The ancestral reconstruction suggests that dumping waste externally is less derived than digging waste nest chambers. Empirical results showed that high soil surface temperatures reduce pathogen prevalence from LCA waste. We proposed that LCA living in environments unfavourable for pathogens (i.e. xeric habitats) avoid digging costs by dumping the refuse above ground. Conversely, in environments suitable for pathogens, LCA species prevent the spread of diseases by storing waste underground, presumably, a behaviour that contributed to the colonization of humid habitats. These results highlight the adaptation of organisms to the hygienic challenges of social living, and illustrate how sanitary behaviours can result from a combination of evolutionary history and current environmental conditions.
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Deltoro, Vicente I., Angeles Calatayud, Cristina Gimeno, and Eva Barreno. "Water relations, chlorophyll fluorescence, and membrane permeability during desiccation in bryophytes from xeric, mesic, and hydric environments." Canadian Journal of Botany 76, no. 11 (November 1, 1998): 1923–29. http://dx.doi.org/10.1139/b98-167.
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The interactions among water content, chlorophyll a fluorescence emission, and potassium leakage were analyzed during dehydration in desiccation-tolerant bryophytes from xeric habitats (Hedwigia ciliata (Hedw.) P. Beauv., Hypnum cupressiforme Hedw., Leucodon sciuroides (Hedw.) Schwaegr., Orthotrichum cupulatum Brid., Pleurochaete squarrosa (Brid.) Lindb., Porella platyphylla (L.) Pfeiff., and Tortula ruralis (Hedw.) Gaertn., Meyer & Scherb.) and desiccation-intolerant bryophytes from mesic and hydric environments (Barbula ehrenbergii (Lor.) Fleisch., Cinclidotus aquaticus (Hedw.) B. & S., Conocephalum conicum (L.) Underw., Lunularia cruciata (L.) Dum. ex Lindb., Palustriella commutata (Hedw.) Ochyra, Philonotis calcarea (B. & S.) Schimp., and Rhynchostegium riparioides (Hedw.) Card.). Their fluorescence characteristics at low water content were low efficiency of photosynthetic quantum conversion, closed photosystem II reaction centers, and strong nonphotochemical quenching only in desiccation-tolerant species. Full restoration of fluorescence parameters upon rewatering in species from xeric environments indicated that the photosynthetic apparatus was fully functional after desiccation. Species from hydric and mesic habitats were unable to restore photochemical activity. This might be a consequence of photoinhibition but also of membrane damage, as indicated by the large leakage of potassium. It is suggested that the capacity to enhance thermal energy dissipation during dehydration might have evolved in species from xeric environments as an adaptation to the utilization of an erratic supply of water. This protective strategy would lower the probability of photodamage during water loss and thus maintain the photosynthetic apparatus in a quickly recuperable state.Key words: bryophytes, chlorophyll fluorescence, dehydration, desiccation tolerance, thermal energy dissipation.
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Pyne, Milo, Steve L. Orzell, Edwin L. Bridges, and Derick Poindexter. "Physalis macrosperma (Solanaceae: Physalinae), a new psammophyte endemic to the west Gulf Coastal Plain of the southeastern U.S.A., a global biodiversity hotspot." Journal of the Botanical Research Institute of Texas 13, no. 1 (July 23, 2019): 31–50. http://dx.doi.org/10.17348/jbrit.v13.i1.824.
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A new species of Physalinae (Solanaceae) is described and illustrated that is endemic to the West Gulf Coastal Plain of the southeastern United States, a global biodiversity hotspot. Physalis macrosperma sp. nov. is distinguished by its large obpyramidal fruiting calyx (35–70 mm in length), its large seeds [3.2–4.2(4.8) mm in length and 2.5–3.5(3.9) mm in width], and its coarsely pitted seed testa. The ecological and geographical setting of P. macrosperma and its morphological relationships with similar taxa are presented. Physalis macrosperma is an herbaceous perennial psammophyte inhabiting open sand barrens within pyrogenic savanna-woodlands of xeric sandhills. It occurs on droughty undulating Eocene-age quartzipsamments within south-central and east-central Texas and on younger xeric sands embedded within the fire-maintained pinelands of southwestern Arkansas, western Louisiana, and southeastern Texas.
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Driessche, R. van den. "Influence of container nursery regimes on drought resistance of seedlings following planting. I. Survival and growth." Canadian Journal of Forest Research 21, no. 5 (May 1, 1991): 555–65. http://dx.doi.org/10.1139/x91-077.
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Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), lodgepole pine (Pinuscontorta Dougl.), and white spruce (Piceaglauca (Moench) Voss) seedlings were grown in Styroblock containers in a container nursery from February to July 1988 and then exposed to three temperatures and three levels of drought stress applied factorially during 18 July to 29 September 1988. Mean temperatures of 13, 16, and 20 °C were imposed in growth chambers, in a cooled plastic house, and in an ambient plastic house, respectively. Control, medium, and severe levels of drought stress were imposed in a series of eight cycles, resulting in mean xylem pressure potentials of −0.32, −0.50, and −0.99 MPa, respectively. Seedlings were kept in the ambient plastic house until January, when they were lifted and cold-stored until planting. Between 11 and 18 April 1989, seedlings were planted in 0.5 m deep sand beds, which provided hygric, mesic, and xeric conditions for testing all species and treatments. At the end of nursery growth, increase in nursery temperature increased height and height:diameter ratio in all species and shoot:root dry weight ratio in Douglas-fir and lodgepole pine. Increase in temperature also increased the number of seedlings with large well-formed buds in white spruce, but reduced the number in Douglas-fir. Drought stress reduced height and dry weight in all species and bud length in lodgepole pine. After 9 weeks in sand beds, low nursery temperature increased survival (19% for lodgepole pine and white spruce grown in the xeric bed), except for Douglas-fir grown in the xeric bed. Nursery drought stress also increased survival (16% for Douglas-fir and lodgepole pine in the xeric bed), but had little effect on white spruce. Low temperature and drought stress treatments that increased survival also reduced height and dry weight of lodgepole pine and white spruce after one growing season in sand beds. Survival showed significant negative correlations with height, dry weight, and height:diameter and shoot:root weight ratios. Low nursery temperature continued to affect growth after planting, increasing relative growth rate and allometric ratio (K) of Douglas-fir and decreasing K of white spruce.
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Stringer, Jeffrey W., Thomas W. Kimmerer, John C. Overstreet, and James P. Dunn. "Oak Mortality in Eastern Kentucky." Southern Journal of Applied Forestry 13, no. 2 (May 1, 1989): 86–91. http://dx.doi.org/10.1093/sjaf/13.2.86.
Full textAbstract:
Abstract Canopy-tree mortality was assessed from 1985 through 1987 at Robinson Forest in eastern Kentucky. Red oaks, predominantly scarlet oak and black oak, experienced the greatest mortality followed by hickories, white oak, and chestnut oak. Mortality was concentrated in mixed red and whiteoak stands on relatively xeric mid- or upper-slope positions. Mortality was not severe in oak-pine stands on extremely xeric sites. The loss of red oaks in mixed oak stands is typical of the current mortality pattern in the southern Appalachians as well as past mortality associated with regionaldroughts. Mortality will probably continue, and these types of losses should be incorporated into management plans. Treatments to alleviate monetary losses include salvage cuts where feasible and treatments aimed at decreasing the basal area of black and scarlet oaks growing in stands whichare considered at risk. South. J. Appl. For. 13(2):86-91.
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Domínguez, Karina, and María Luisa Jiménez. "Composition of spider prey captured by the wasp Trypoxylon (Trypargilum) tridentatum tridentatum in two habitats in an oasis in Baja California Sur, Mexico." Canadian Entomologist 140, no. 3 (June 2008): 388–92. http://dx.doi.org/10.4039/n08-006.
Full textAbstract:
AbstractTrypoxylon (Trypargilum) tridentatum tridentatum Packard (Hymenoptera: Crabronidae) is a spider-hunting wasp in mesic and xeric habitats in the arid Baja California peninsula of Mexico. Spider (Araneae) prey were collected every 2 weeks from wasp trap nests. Individuals of the family Araneidae were the most abundant prey (60.9%), followed by Theridiidae and Mimetidae. Dictynidae, Anyphaenidae, Salticidae, Uloboridae, Tetragnathidae, Miturgidae, and Philodromidae were captured only in the mesic habitat. An unidentified species of Eriophora Simon (Araneidae) was the most frequently collected spider in the xeric habitat (29.0%), followed by Theridion submissum Gertsch and Davis (Theridiidae) (24.0%), which was the commonest prey species in the mesic habitat (21.1%), and Metepeira crassipes Chamberlin and Ivie (Araneidae) (16.5%). Nineteen species and three families are newly recorded as prey. The araneids Araneus lineatipes (O.P.-Cambridge) and Kaira alba (Hentz) and the uloborids Philoponella arizonica (Gertsch) and Uloborus segregatus Gertsch are new records for Baja California.
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Giannoulis, Kyriakos, Dimitrios Bartzialis, Elpiniki Skoufogianni, and Nicholaos Danalatos. "Nutrients Use Efficiency and Uptake Characteristics of Panicum virgatum for Fodder Production." Journal of Agricultural Science 9, no. 3 (February 13, 2017): 233. http://dx.doi.org/10.5539/jas.v9n3p233.
Full textAbstract:
Panicum virgatum could produce cattle feed with lower costs due to the low input requirements and its perennial nature. Dry biomass yield vs. N-P-K nutrient uptake relations as well as the N-mineralization and the N-fertilization recovery fraction for Panicum virgatum (cv. Alamo) were determined under field conditions for four N-fertilization (0, 80, 160 and 240 kg ha-1) and two irrigation levels (0 and 250 mm), οn two soils in central Greece with rather different moisture status. It was found that the dry fodder yield on the aquic soil may reach 14 t ha-1 using supplemental irrigation; while on the xeric soil a lower yield of 9-10 t ha-1 may be produced only under supplemental irrigation. Moreover, the average N, P and K concentration was 1.3%, 0.14% and 1.3% in leaves, and 0.5%, 0.85%, and 1.5% in stems, respectively, showing the very low crop requirements. Furthermore, linear biomass yield-nutrient uptake relationships were found with high R2, pointing to nutrient use efficiency of 132 and 75 kg kg-1, for N and K respectively. The base N-uptake ranged from 71-74 kg ha-1 on the aquic to 60 kg ha-1 or less on the xeric soil. Finally, it was found that N-recovery fraction was 20% on the aquic soil and lower on the xeric. Therefore, it could be conclude that Panicum virgatum seems to be a very promising crop for fodder production and its introduction in land use systems (especially οn aquic soils of similar environments) should be taken into consideration.
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Burgess, J., K. Szlavecz, N. Rajakaruna, S. Lev, and C. Swan. "Vegetation dynamics and mesophication in response to conifer encroachment within an ultramafic system." Australian Journal of Botany 63, no. 4 (2015): 292. http://dx.doi.org/10.1071/bt14241.
Full textAbstract:
The biological, ecological, and evolutionary significance of serpentine habitats has long been recognised. We used an integrated physiochemical dataset combining plot spatial data with temporal data from tree cores to evaluate changes in soils and vegetation. Data suggest that this unique habitat is undergoing a transition, endangering local biodiversity and endemic plant species. The objective of this work was to analyse the vegetation dynamics of a xeric serpentine savanna located in the Mid-Atlantic, USA. We employed vegetation surveys of 32 10 × 15 m quadrats to obtain woody species composition, density, basal area, and developed a spatial physiochemical dataset of substrate geochemistry to independently summarise the data using regression and ordination techniques. This information was interpreted alongside historical, dendrochronologic and soil stable carbon isotopic data to evaluate successional dynamics. Comparisons among geologic, pedologic and vegetation environmental drivers indicated broad correlations across an environmental gradient, corresponding to a grassland to forest transition. The woodland communities appear to be part of a complex soil moisture and chemistry gradient that affects the extent, density, basal area and species composition of these communities. Over the gradient, there is an increase in α diversity, a decrease in the density of xeric and invasive species, and an increase in stem density of more mesic species. Dendrochronology suggests poor recruitment of xeric species and concomitant increase in more mesic species. The data indicated that former C4-dominated grasslands were initially invaded by conifers and are now experiencing mesophication, with growing dominance by Acer, Nyssa and more mesic Quercus and Fagus species.