Biomass is among the most important state variables used to characterize ecosystems. Estimation of tree biomass involves the development of species-specific “allometric equations” that describe the relationship betw...Biomass is among the most important state variables used to characterize ecosystems. Estimation of tree biomass involves the development of species-specific “allometric equations” that describe the relationship between tree biomass and tree diameter and/or height. While many allometric equations were developed for northern hemisphere and tropical species, rarely have they been developed for trees in arid ecosystems, limiting, amongst other things, our ability to estimate carbon stocks in arid regions. Acacia raddiana and A. tortilis are major components of savannas and arid regions in the Middle East and Africa, where they are considered keystone species. Using the opportunity that trees were being uprooted for land development, we measured height (H), north-south (C1) and east-west (C2) canopy diameters, stem diameter at 1.3 meters of the largest stem (D1.3 or DBH), and aboveground fresh and dry weight (FW and DW, respectively) of nine trees (n = 9) from each species. For A. tortilis only, we recorded the number of trunks, and measured the diameter of the largest trunk at ground level (D0). While the average crown (canopy) size (C1 + C2) was very similar among the two species, Acacia raddiana trees were found to be significantly taller than their Acacia tortilis counterparts. Results show that in the arid Arava (southern Israel), an average adult acacia tree has ~200 kg of aboveground dry biomass and that a typical healthy acacia ecosystem in this region, may include ~41 tons of tree biomass per km2. The coefficients of DBH (tree diameter at breast height) to biomass and wood volume, could be used by researchers studying acacia trees throughout the Middle East and Africa, enabling them to estimate biomass of acacia trees and to evaluate their importance for carbon stocks in their arid regions. Highlights: 1) Estimations of tree biomass in arid regions are rare. 2) Biomass allometric equations were developed for A. raddiana and A. tortilis trees. 3) Equations contribute to the estimation of carbon stocks in arid regions.展开更多
Water availability,which enables plant growth and animal activity,regulates dryland ecosystem function.In hyper-arid ecosystems,rain cannot support vascular plant growth.Therefore,hyper-arid vegetation is restricted t...Water availability,which enables plant growth and animal activity,regulates dryland ecosystem function.In hyper-arid ecosystems,rain cannot support vascular plant growth.Therefore,hyper-arid vegetation is restricted to the lower topography,where runoff accumulates.Typically,food resources originating from areas of dense vegetation are dispersed across the desert floor,enabling animal life in areas lacking vascular plant growth.However,certain regions,such as the hyper-arid upper topography,may be devoid of plant-derived food resources.The present study examined arthropod activity in the upper topography of a hyper-arid desert,in comparison with arthropod activity in the lower topography.Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel,vegetated riverbeds.Surprisingly,the study revealed dense arthropod communities in the barren upper topography.Arthropods collected in the upper topography represented 26%of total arthropod abundance.In addition,the overlap between arthropod identity in the ridges and wadis(i.e.,riverbeds)was low,and certain arthropods were strongly affiliated with the ridges.The upper topographic communities included high numbers of silverfish(Zygentoma:Lepismatidae),malachite beetles(Psiloderes),and predatory mites(Acari:Anystidae),and these arthropods were present at various life stages.It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area.These results raise the possibility that other food sources,independent from vascular plants,may play a significant role in the life history of hyper-arid arthropods.展开更多
Aims In plant eco-physiology,less negative(enriched)carbon 13(^(13)C)in the leaves indicates conditions of reducing leaf gas exchange through stomata,e.g.under drought.In addition,^(13)C is expected to be less negativ...Aims In plant eco-physiology,less negative(enriched)carbon 13(^(13)C)in the leaves indicates conditions of reducing leaf gas exchange through stomata,e.g.under drought.In addition,^(13)C is expected to be less negative in non-photosynthetic tissues as compared with leaves.However,these relationships inδ^(13)C from leaves(photosynthetic organs)to branches,stems and roots(non-photosynthetic organs)are rarely tested across multiple closely related tree species,multiple compartments,or in trees growing under extreme heat and drought.Methods We measured leaf-to-root^(13)C in three closely related desert acacia species(Acacia tortilis,A.raddiana and A.pachyceras).We measuredδ^(13)C in leaf tissues from mature trees in southern Israel.In parallel,a 7-year irrigation experiment with 0.5,1.0 or 4.0 L day1 was conducted in an experimental orchard.At the end of the experiment,growth parameters andδ^(13)C were measured in leaves,branches,stems and roots.Important Findings Theδ^(13)C in leaf tissues sampled from mature trees was ca.-27‰,far more depleted than expected from a desert tree growing in one of the Earth's driest and hottest environments.Across acacia species and compartments,δ^(13)C was not enriched at all irrigation levels(-28‰to ca.-27‰),confirming our measurements in the mature trees.Among compartments,leafδ^(13)C was unexpectedly similar to branch and rootδ^(13)C,and surprisingly,even less negative than stemδ^(13)C.The highly depleted leafδ^(13)C suggests that these trees have high stomatai gas exchange,despite growing in extremely dry habitats.The lack ofδ^(13)C enrichment in nonphotosynthetic tissues might be related to the seasonal coupling of growth of leaves and heterotrophic tissues.展开更多
文摘Biomass is among the most important state variables used to characterize ecosystems. Estimation of tree biomass involves the development of species-specific “allometric equations” that describe the relationship between tree biomass and tree diameter and/or height. While many allometric equations were developed for northern hemisphere and tropical species, rarely have they been developed for trees in arid ecosystems, limiting, amongst other things, our ability to estimate carbon stocks in arid regions. Acacia raddiana and A. tortilis are major components of savannas and arid regions in the Middle East and Africa, where they are considered keystone species. Using the opportunity that trees were being uprooted for land development, we measured height (H), north-south (C1) and east-west (C2) canopy diameters, stem diameter at 1.3 meters of the largest stem (D1.3 or DBH), and aboveground fresh and dry weight (FW and DW, respectively) of nine trees (n = 9) from each species. For A. tortilis only, we recorded the number of trunks, and measured the diameter of the largest trunk at ground level (D0). While the average crown (canopy) size (C1 + C2) was very similar among the two species, Acacia raddiana trees were found to be significantly taller than their Acacia tortilis counterparts. Results show that in the arid Arava (southern Israel), an average adult acacia tree has ~200 kg of aboveground dry biomass and that a typical healthy acacia ecosystem in this region, may include ~41 tons of tree biomass per km2. The coefficients of DBH (tree diameter at breast height) to biomass and wood volume, could be used by researchers studying acacia trees throughout the Middle East and Africa, enabling them to estimate biomass of acacia trees and to evaluate their importance for carbon stocks in their arid regions. Highlights: 1) Estimations of tree biomass in arid regions are rare. 2) Biomass allometric equations were developed for A. raddiana and A. tortilis trees. 3) Equations contribute to the estimation of carbon stocks in arid regions.
基金supported by the Ministry of Science and Technology。
文摘Water availability,which enables plant growth and animal activity,regulates dryland ecosystem function.In hyper-arid ecosystems,rain cannot support vascular plant growth.Therefore,hyper-arid vegetation is restricted to the lower topography,where runoff accumulates.Typically,food resources originating from areas of dense vegetation are dispersed across the desert floor,enabling animal life in areas lacking vascular plant growth.However,certain regions,such as the hyper-arid upper topography,may be devoid of plant-derived food resources.The present study examined arthropod activity in the upper topography of a hyper-arid desert,in comparison with arthropod activity in the lower topography.Pitfall traps were utilized to compare arthropod activity along unvegetated ridges with activity in parallel,vegetated riverbeds.Surprisingly,the study revealed dense arthropod communities in the barren upper topography.Arthropods collected in the upper topography represented 26%of total arthropod abundance.In addition,the overlap between arthropod identity in the ridges and wadis(i.e.,riverbeds)was low,and certain arthropods were strongly affiliated with the ridges.The upper topographic communities included high numbers of silverfish(Zygentoma:Lepismatidae),malachite beetles(Psiloderes),and predatory mites(Acari:Anystidae),and these arthropods were present at various life stages.It remains unclear how arthropod communities can persist in the unvegetated upper topography of the hyper-arid study area.These results raise the possibility that other food sources,independent from vascular plants,may play a significant role in the life history of hyper-arid arthropods.
基金funded by the Benoziyo Fund for the Advancement of ScienceMr and Mrs Norman Reiser,together with the Weizmann Center for New Scientists+1 种基金the Edith&Nathan Goldberg Career Development Chair.D.U.was funded by Ariovich scholarship and by the scholarship of the environmental science school of the Hebrew University.G.W.thanks the Arava Drainage Authority and the Israeli Ministry of Science and Technology(MOST)for their continued support.The study used data available through the TRY initiative on plant traits(http://www.try-db.org,data request 8968).The TRY initiative and database is hosted,developed and maintained by J.Kattge and G.Bonisch(Max Planck Institute for Biogeochemistry,Jena,Germany)TRY is currently supported by DIVERSITAS/Future Earth and the German Centre for Integrative Biodiversity Research(iDiv)Halle-Jena-Leipzig.
文摘Aims In plant eco-physiology,less negative(enriched)carbon 13(^(13)C)in the leaves indicates conditions of reducing leaf gas exchange through stomata,e.g.under drought.In addition,^(13)C is expected to be less negative in non-photosynthetic tissues as compared with leaves.However,these relationships inδ^(13)C from leaves(photosynthetic organs)to branches,stems and roots(non-photosynthetic organs)are rarely tested across multiple closely related tree species,multiple compartments,or in trees growing under extreme heat and drought.Methods We measured leaf-to-root^(13)C in three closely related desert acacia species(Acacia tortilis,A.raddiana and A.pachyceras).We measuredδ^(13)C in leaf tissues from mature trees in southern Israel.In parallel,a 7-year irrigation experiment with 0.5,1.0 or 4.0 L day1 was conducted in an experimental orchard.At the end of the experiment,growth parameters andδ^(13)C were measured in leaves,branches,stems and roots.Important Findings Theδ^(13)C in leaf tissues sampled from mature trees was ca.-27‰,far more depleted than expected from a desert tree growing in one of the Earth's driest and hottest environments.Across acacia species and compartments,δ^(13)C was not enriched at all irrigation levels(-28‰to ca.-27‰),confirming our measurements in the mature trees.Among compartments,leafδ^(13)C was unexpectedly similar to branch and rootδ^(13)C,and surprisingly,even less negative than stemδ^(13)C.The highly depleted leafδ^(13)C suggests that these trees have high stomatai gas exchange,despite growing in extremely dry habitats.The lack ofδ^(13)C enrichment in nonphotosynthetic tissues might be related to the seasonal coupling of growth of leaves and heterotrophic tissues.
