scholarly journals Contrasting effects of nutrients and consumers on tree colonization and growth during secondary succession

2020 ◽  
Author(s):  
Robert W. Heckman ◽  
Fletcher W. Halliday ◽  
Peter A. Wilfahrt
Keyword(s):  
Tree Growth ◽  
Secondary Succession ◽  
Seed Rain ◽  
Subsequent Growth ◽  
Basal Diameter ◽  
Herbaceous Communities ◽  
Two Phases ◽  
Opposing Effects ◽  
Herbaceous Community

AbstractFor succession to proceed from herbaceous to woody dominance, trees must colonize herbaceous communities and grow. Success across these two phases of succession might result from different interactions with the herbaceous community. First, colonizing trees must compete against larger, established herbs, while subsequent growth occurs among similarly sized or smaller herbs. This shift from colonization to growth may cause three drivers of secondary succession— nutrients, consumers, and herbaceous diversity—to differentially affect tree colonization and growth. Initially, these drivers should favor larger, established herbs, reducing colonization. Later, when established trees can better compete with herbs, these drivers should benefit trees and increase their growth. In a four-year study, we added nutrients to, excluded aboveground consumers from, and manipulated initial richness of, the herbaceous community, then allowed trees to naturally colonize these communities (from intact seedbanks or as seed-rain) and grow. Nutrients and consumers had opposing effects on tree colonization and growth: adding nutrients and excluding consumers reduced tree colonization, but later increased established tree growth (height, basal diameter). Together, this shows stage-specific impacts of nutrients and consumers that may improve predictions of the rate and trajectory of succession: factors that initially limited tree colonization later helped established trees to grow.

Changes in seed rain during secondary succession in a tropical montane cloud forest region in Oaxaca, Mexico

2008 ◽  
Vol 24 (4) ◽  
pp. 433-444 ◽  
Author(s):  
R. F. del Castillo ◽  
M. A. Pérez Ríos
Keyword(s):  
Seed Dispersal ◽  
Secondary Succession ◽  
Cloud Forest ◽  
Seed Rain ◽  
Stand Age ◽  
Primary Forest ◽  
Forest Fragments ◽  
Long Distance ◽  
Southern Mexico ◽  
Tropical Montane Cloud Forests

AbstractSeed dispersal is the first stage of colonization, and potentially affects recruitment. This process deserves more attention in tropical montane cloud forests (TMCF), since secondary succession is common owing to episodic disturbances. We studied annual seed rain in 10 nearby forest stands, ≈7 to ≈100 y following shifting agriculture, and one primary forest stand in southern Mexico to test the hypothesis that seed rain is limited at the scale of neighbouring fragments and that such limitation differs among species with different dispersal modes and successional origin. Annual seed rain was heterogeneous among forest fragments probably due to the prevalence of local seed dispersal, differences in stand age and the proportion of zoochory, and may help explain the patchy distribution of species observed in TMCF. Seed rain abundance and species diversity per unit trap area increased with the age of the stand. Biotically dispersed seeds increased towards older stands relative to abiotically dispersed seeds. Late-successional seeds were rarer in early successional stands than pioneer seeds in late-successional stands, suggesting that long-distance dispersal is generally more common for pioneer plants. Seed dispersal appears to constrain forest regeneration and to influence fragment species composition as a function of the distance from the source forests.

Genetic control of coppice and lignotuber development in Eucalyptus globulus

2003 ◽  
Vol 51 (1) ◽  
pp. 57 ◽  
Author(s):  
S. P. Whittock ◽  
L. A. Apiolaza ◽  
C. M. Kelly ◽  
B. M. Potts
Keyword(s):  
Genetic Diversity ◽  
Tree Growth ◽  
Artificial Selection ◽  
Eucalyptus Globulus ◽  
Cotyledonary Node ◽  
Subsequent Growth ◽  
Seedling Traits ◽  
Short Rotation ◽  
Vigorous Growth ◽  
Number Of Stems

The economics of short-rotation pulpwood plantations of Eucalyptus globulus as a coppice crop are influenced by stump survival and subsequent coppice growth rates. This study revealed significant genetic diversity in coppicing traits, both within and between subraces, following felling in a progeny trial after 9 years of growth. A total of 67% of trees coppiced after 14 months, but subraces varied from 43 to 73%. Heritabilities for coppice success (0.07) and subsequent growth (0.16–0.17) were low but statistically significant. Strong genetic correlation between presence/absence of coppice, the number of stems coppicing from the stump and modal coppice height, indicate that selection is possible by using the binary trait. The ability of a tree to coppice was genetically correlated with tree growth prior to felling (rg = 0.61) and with nursery-grown seedling traits, where large genetic differences were observed in the development of lignotubers. Coppicing was genetically correlated with the number of nodes with lignotubers (rg = 0.66) and seedling stem diameter at the cotyledonary node (rg = 0.91). These traits were uncorrelated with later age growth and with each other. The results suggest that coppicing is influenced by three independent mechanisms—lignotuber development, enlargement of the seedling stem at the cotyledonary node and vigorous growth—which enhance ability to survive catastrophic damage, and indicate that both lignotuber and coppice development can be altered by both natural and artificial selection.

scholarly journals Opposing effects on two phases of defense responses from concerted actions of HSC70 and BON1 in Arabidopsis

2015 ◽  
pp. pp.00970.2015 ◽  
Author(s):  
Mingyue Gou ◽  
Zemin Zhang ◽  
Ning Zhang ◽  
Quansheng Huang ◽  
Jacqueline Monaghan ◽  
...  
Keyword(s):  
Defense Responses ◽  
Two Phases ◽  
Opposing Effects

scholarly journals Aboveground Biomass Response to Release Treatments in a Young Ponderosa Pine Plantation

Forests ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 795
Author(s):  
Martin Ritchie ◽  
Jianwei Zhang ◽  
Ethan Hammett
Keyword(s):  
Tree Growth ◽  
Ponderosa Pine ◽  
Aboveground Biomass ◽  
Growth Potential ◽  
Basal Diameter ◽  
Chemical Release ◽  
No Release ◽  
Woody Shrubs ◽  
Shrub Biomass ◽  
Release Control

Controlling competing vegetation is vital for early plantation establishment and growth. Aboveground biomass (AGB) response to manual grubbing release from shrub competition was compared with no release control in a twelve-year-old ponderosa pine (Pinus ponderosa Lawson & C. Lawson) plantation established after a wildfire in northeastern California. In addition, response to chemical release followed by precommercial thinning in an adjacent plantation was also examined as a growth potential from a more intensively managed regime, where shrub competition was virtually eliminated. We measured AGB in both planted trees and competing woody shrubs to partition the biomass pools in the plantation. The results showed a significant grubbing treatment effect on basal diameter (BD) at 10 cm aboveground (p = 0.02), but not on tree height (p = 0.055). Height and BD were 2.0 m and 7.4 cm in the manual release, respectively, compared to 1.7 m and 5.6 cm in the control. However, chemical release produced much greater rates of tree growth with a height of 3.6 m and BD of 14.7 cm, respectively. Tree AGB was 60% higher with the manual release of shrubs (1.2 Mg ha−1) than with control (0.7 Mg ha−1) (p < 0.05). The planted area without shrub competition yielded a much higher green tree biomass (16.0 Mg ha−1). When woody shrub biomass was included, the total AGB (trees and woody shrubs) appeared slightly higher, but non-significant in the no release control (13.3 Mg ha−1) than in the manual release (11.9 Mg ha−1) (p = 0.66); the chemical release had 17.1 Mg ha−1. Clearly, shrub biomass dominated this young plantation when understory shrubs were not completely controlled. Although the manual release did increase targeted tree growth to some degree, the cost may limit this practice to a smaller scale and the remaining shrub dominance may create long-term reductions in growth and a persistent fuels problem in these fire-prone ecosystems.

scholarly journals Seed Rain and Advance Regeneration in Secondary Succession in the Brazilian Amazon

2011 ◽  
Vol 4 (3) ◽  
pp. 300-316 ◽  
Author(s):  
Lindsay M. Wieland ◽  
Rita C. G. Mesquita ◽  
Paulo Estefano D. Bobrowiec ◽  
Tony V. Bentos ◽  
G. Bruce Williamson
Keyword(s):  
Secondary Succession ◽  
Brazilian Amazon ◽  
Seed Rain ◽  
Advance Regeneration

scholarly journals Spatial variation in the structure and composition of the herbaceous community in a semiarid region of northeastern Brazil

2013 ◽  
Vol 73 (1) ◽  
pp. 135-148 ◽  
Author(s):  
KA. Silva ◽  
JMFF. Santos ◽  
DM. Santos ◽  
EMN. Ferraz ◽  
EL. Araújo
Keyword(s):  
Plant Density ◽  
Diversity Index ◽  
Northeastern Brazil ◽  
Semiarid Region ◽  
Ecological Value ◽  
Importance Value Index ◽  
Importance Value ◽  
Herbaceous Communities ◽  
Average Plant ◽  
Herbaceous Community

In the arid and semiarid environments of the world, microhabitats serve as models for the structure of vegetation communities. The goal of this study was to identify differences in the structures of the herbaceous communities growing on a crystalline substrate and those growing on a sedimentary substrate in a semiarid region of northeastern Brazil. One hundred 1 × 1 m plots were established in each area for quantitative sampling, with 69 species recorded in the crystalline area and 76 in the sedimentary area. The average plant density was higher in the sedimentary area, and average diameters and heights were greater in the crystalline area. The families and species with a high Importance Value Index (IVI) and a high Mixed Ecological Value Index (MEVI) differed between the areas. Of the species with high densities, only four were found in both areas. Shannon-Weiner diversity index values in the crystalline (2.96 nats/ind.-1) and sedimentary (2.89 nats/ind.-1) areas were similar. Evenness values on both substrates were also similar (0.72 and 0.71 in the crystalline and sedimentary areas, respectively). This study shows that variations in plant establishment conditions between crystalline and sedimentary areas in a semiarid region of northeastern Brazil should be considered as structure-modeling factors for the herbaceous community.

Trunk and main-branch development in Nothofagus pumilio (Nothofagaceae): a retrospective analysis of tree growth

2002 ◽  
Vol 80 (7) ◽  
pp. 763-772 ◽  
Author(s):  
A Passo ◽  
J G Puntieri ◽  
D Barthélémy
Keyword(s):  
Tree Growth ◽  
Sharp Decrease ◽  
Tree Age ◽  
Nothofagus Pumilio ◽  
Basal Diameter ◽  
Length Unit ◽  
Architectural Analysis ◽  
Architectural Features ◽  
Shoot Size ◽  
Number Of Leaves

The development of the trunk and main branches of approximately 26-year-old Nothofagus pumilio (Poepp. et Endl.) Krasser trees was studied. The length and number of leaves of annual shoots were recorded for 56 trees from a natural population. Morphological and macroanatomical features allowed the identification of shoot apex deaths and the axillary positions from which branches and relay shoots derived. The trees had a mean height of approximately 6 m and a mean basal diameter of approximately 8 cm. The length of trunk shoots increased from the first years to the intermediate years of tree growth and decreased for the last 6 years of tree growth. The maximum length and number of leaves of trunk shoots were registered for the years around 1985, when tree age was about 17 years. The likelihood of apex death for trunk shoots was minimum for the period of maximum trunk shoot size. Despite the fact that the architectural features of the sampled trees corresponded to those of young, vigorously growing trees, they seemed to have reached a stage of low annual height growth. A sharp decrease in trunk shoot size occurred in 1992, a year in which rainfall during the growing season reached the minimum for the lifetime of the sampled trees. The size of shoots developed after 1992 was, on average, lower than that of shoots developed before 1992. Stressful conditions in this year may relate to meristem ageing and thus to the size of shoots formed in the following years. Main branches started their development with shoots similar to those of the trunk but were clearly differentiated from the trunk 5 years later. The differentiation between main branch and trunk shoots involved not only a lower shoot size but also a higher number of leaves per shoot length unit in main branch than in trunk shoots.Key words: Nothofagus pumilio, architectural analysis, shoot, trunk development, branching pattern, morphogenetic gradient.

Precipitation of NiHfsi phase in NiAl single crystals containing Hf

1995 ◽  
Vol 53 ◽  
pp. 532-533
Author(s):  
A. Garg ◽  
R. D. Noebe ◽  
R. Darolia
Keyword(s):  
High Temperature ◽  
Single Crystals ◽  
High Temperature Strength ◽  
Bridgman Technique ◽  
Shell Mold ◽  
Third Phase ◽  
Unknown Phase ◽  
Transmission Electron ◽  
Two Phases ◽  
Nial Matrix

Small additions of Hf to NiAl produce a significant increase in the high-temperature strength of single crystals. Hf has a very limited solubility in NiAl and in the presence of Si, results in a high density of G-phase (Ni16Hf6Si7) cuboidal precipitates and some G-platelets in a NiAl matrix. These precipitates have a F.C.C structure and nucleate on {100}NiAl planes with almost perfect coherency and a cube-on-cube orientation-relationship (O.R.). However, G-phase is metastable and after prolonged aging at high temperature dissolves at the expense of a more stable Heusler (β'-Ni2AlHf) phase. In addition to these two phases, a third phase was shown to be present in a NiAl-0.3at. % Hf alloy, but was not previously identified (Fig. 4 of ref. 2 ). In this work, we report the morphology, crystal-structure, O.R., and stability of this unknown phase, which were determined using conventional and analytical transmission electron microscopy (TEM).Single crystals of NiAl containing 0.5at. % Hf were grown by a Bridgman technique. Chemical analysis indicated that these crystals also contained Si, which was not an intentional alloying addition but was picked up from the shell mold during directional solidification.

Imaging of Al-Li-Cu alloys with a Scanning Ion Microprobe

1990 ◽  
Vol 48 (2) ◽  
pp. 314-315
Author(s):  
K.K. Soni ◽  
D.B. Williams ◽  
J.M. Chabala ◽  
R. Levi-Setti ◽  
D.E. Newbury
Keyword(s):  
Mass Spectrometry ◽  
Secondary Ion Mass Spectrometry ◽  
Equilibrium Phase ◽  
Icosahedral Symmetry ◽  
Ion Microprobe ◽  
X Ray ◽  
Cu Alloys ◽  
Two Phases ◽  
The University ◽  
Secondary Ion

In contrast to the inability of x-ray microanalysis to detect Li, secondary ion mass spectrometry (SIMS) generates a very strong Li+ signal. The latter’s potential was recently exploited by Williams et al. in the study of binary Al-Li alloys. The present study of Al-Li-Cu was done using the high resolution scanning ion microprobe (SIM) at the University of Chicago (UC). The UC SIM employs a 40 keV, ∼70 nm diameter Ga+ probe extracted from a liquid Ga source, which is scanned over areas smaller than 160×160 μm2 using a 512×512 raster. During this experiment, the sample was held at 2 × 10-8 torr.In the Al-Li-Cu system, two phases of major importance are T1 and T2, with nominal compositions of Al2LiCu and Al6Li3Cu respectively. In commercial alloys, T1 develops a plate-like structure with a thickness <∼2 nm and is therefore inaccessible to conventional microanalytical techniques. T2 is the equilibrium phase with apparent icosahedral symmetry and its presence is undesirable in industrial alloys.

Defect structures of Nb1+αS2 sulfidation scales

1992 ◽  
Vol 50 (1) ◽  
pp. 38-39
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Stacking Faults ◽  
Rhombohedral Structure ◽  
Stacking Sequence ◽  
Defect Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plane Normal ◽  
Lower Case ◽  
Sulfur Layer ◽  
Two Phases

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.

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