scholarly journals Performance of tropical forest seedlings under shade and drought: an interspecific trade-off in demographic responses

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Stefan J. Kupers ◽  
Christian Wirth ◽  
Bettina M. J. Engelbrecht ◽  
Andrés Hernández ◽  
Richard Condit ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Performance Metrics ◽  
Barro Colorado Island ◽  
First Year ◽  
Drought Intensity ◽  
Trade Off ◽  
Deep Shade ◽  
Species Responses ◽  
The Relationship

AbstractSeedlings in moist tropical forests must cope with deep shade and seasonal drought. However, the interspecific relationship between seedling performance in shade and drought remains unsettled. We quantified spatiotemporal variation in shade and drought in the seasonal moist tropical forest on Barro Colorado Island (BCI), Panama, and estimated responses of naturally regenerating seedlings as the slope of the relationship between performance and shade or drought intensity. Our performance metrics were relative height growth and first-year survival. We investigated the relationship between shade and drought responses for up to 63 species. There was an interspecific trade-off in species responses to shade versus species responses to dry season intensity; species that performed worse in the shade did not suffer during severe dry seasons and vice versa. This trade-off emerged in part from the absence of species that performed particularly well or poorly in both drought and shade. If drought stress in tropical forests increases with climate change and as solar radiation is higher during droughts, the trade-off may reinforce a shift towards species that resist drought but perform poorly in the shade by releasing them from deep shade.

scholarly journals Consistency of demographic trade-offs across tropical forests

2021 ◽  
Author(s):  
Stephan Kambach ◽  
Richard Condit ◽  
Salomón Aguilar ◽  
Helge Bruelheide ◽  
Sarayudh Bunyavejchewin ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Large Scale ◽  
Negative Relationship ◽  
Trade Off ◽  
Growth And Survival ◽  
Trade Offs ◽  
Tree Communities ◽  
Demographic Processes ◽  
Tropical Forest Dynamics

All species must balance their allocation to growth, survival and recruitment. Among trees, evolution has resulted in different strategies of partitioning resources to these key demographic processes, i.e. demographic trade-offs. It is unclear whether the same demographic trade-offs structure tropical forests worldwide. Here, we used data from 13 large-scale and long-term tropical forest plots to estimate the principal trade-offs in growth, survival, recruitment, and tree stature at each site. For ten sites, two trade-offs appeared repeatedly. One trade-off showed a negative relationship between growth and survival, i.e. the well-known fast−slow continuum. The second trade-off distinguished between tall-statured species and species with high recruitment rates, i.e. a stature−recruitment trade-off. Thus, the fast-slow continuum and tree stature are two independent dimensions structuring most tropical tree communities. Our discovery of the consistency of demographic trade-offs and strategies across forest types in three continents substantially improves our ability to predict tropical forest dynamics worldwide.

Effects of light availability and rainfall on leaf production in a moist tropical forest in central Panama

1998 ◽  
Vol 14 (3) ◽  
pp. 309-321 ◽  
Author(s):  
JOHN A. BARONE
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Light Availability ◽  
Dry Season ◽  
Wet Season ◽  
Leaf Production ◽  
Active Radiation ◽  
One Year ◽  
The Relationship ◽  
Central Panama

New leaf production in seasonal tropical forests may result from changes in water or light availability. In this study, the relationship between leaf flushing, photosynthetically active radiation (PAR) and rainfall was examined for understorey saplings in a moist tropical forest over one year. During the wet season, weeks with greater PAR were correlated with a greater proportion of saplings flushing new leaves during subsequent weeks in nine out of ten species. Rainfall was negatively correlated with subsequent leafing during the wet season for six of ten species. However, during the dry season, rainfall was positively correlated with leafing during the following weeks for six species, but the relationship was much weaker. PAR in the dry season was negatively correlated with flushing in eight species. These results support the hypothesis that under well-watered conditions, light limits leaf production, and peaks in insolation result in greater leaf production.

scholarly journals The growth−survival and stature−recruitment  trade-offs structure the majority of tropical forests.

2021 ◽  
Author(s):  
Stephan Kambach ◽  
Richard Condit ◽  
Salomón Aguilar ◽  
Helge Bruelheide ◽  
Sarayudh Bunyavejchewin ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Large Scale ◽  
Negative Relationship ◽  
Trade Off ◽  
Growth And Survival ◽  
Trade Offs ◽  
Tree Communities ◽  
Demographic Processes ◽  
Tropical Forest Dynamics

All species must balance their allocation to growth, survival and recruitment. Among trees, evolution has resulted in different strategies of partitioning resources to these key demographic processes, i.e. demographic trade-offs. It is unclear whether the same demographic trade-offs structure tropical forests worldwide. Here, we used data from 13 large-scale and long-term tropical forest plots to estimate the principal trade-offs in growth, survival, recruitment, and tree stature at each site. For ten sites, two trade-offs appeared repeatedly. One trade-off showed a negative relationship between growth and survival, i.e. the well-known fast−slow continuum. The second trade-off distinguished between tall-statured species and species with high recruitment rates, i.e. a stature−recruitment trade-off. Thus, the fast-slow continuum and tree stature are two independent dimensions structuring most tropical tree communities. Our discovery of the consistency of demographic trade-offs and strategies across forest types in three continents substantially improves our ability to predict tropical forest dynamics worldwide.

Changing perspectives of the demands on tropical forests

1992 ◽  
Vol 68 (4) ◽  
pp. 476-480
Author(s):  
R. D. Ayling
Keyword(s):  
Developing Countries ◽  
Tropical Forest ◽  
Tropical Forests ◽  
Forest Resources ◽  
The South ◽  
Ecosystem Degradation ◽  
The North ◽  
The Relationship ◽  
North And South

Underlying many of the issues associated with tropical forests, deforestation and ecosystem degradation is the relationship between North and South – the relationship between "developed" and "developing" countries. This relationship is the origin of some major perceptions which we in the North hold about the needs and expectations of societies in the South related to their tropical forest resources.

scholarly journals Detecting tropical forest biomass dynamics from repeated airborne lidar measurements

2013 ◽  
Vol 10 (8) ◽  
pp. 5421-5438 ◽  
Author(s):  
V. Meyer ◽  
S. S. Saatchi ◽  
J. Chave ◽  
J. W. Dalling ◽  
S. Bohlman ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Spatial Scale ◽  
Tropical Forests ◽  
Spatial Scales ◽  
Forest Biomass ◽  
Airborne Lidar ◽  
Barro Colorado Island ◽  
Accurate Estimation ◽  
Old Growth ◽  
Lidar Measurements

Abstract. Reducing uncertainty of terrestrial carbon cycle depends strongly on the accurate estimation of changes of global forest carbon stock. However, this is a challenging problem from either ground surveys or remote sensing techniques in tropical forests. Here, we examine the feasibility of estimating changes of tropical forest biomass from two airborne lidar measurements of forest height acquired about 10 yr apart over Barro Colorado Island (BCI), Panama. We used the forest inventory data from the 50 ha Center for Tropical Forest Science (CTFS) plot collected every 5 yr during the study period to calibrate the estimation. We compared two approaches for detecting changes in forest aboveground biomass (AGB): (1) relating changes in lidar height metrics from two sensors directly to changes in ground-estimated biomass; and (2) estimating biomass from each lidar sensor and then computing changes in biomass from the difference of two biomass estimates, using two models, namely one model based on five relative height metrics and the other based only on mean canopy height (MCH). We performed the analysis at different spatial scales from 0.04 ha to 10 ha. Method (1) had large uncertainty in directly detecting biomass changes at scales smaller than 10 ha, but provided detailed information about changes of forest structure. The magnitude of error associated with both the mean biomass stock and mean biomass change declined with increasing spatial scales. Method (2) was accurate at the 1 ha scale to estimate AGB stocks (R2 = 0.7 and RMSEmean = 27.6 Mg ha−1). However, to predict biomass changes, errors became comparable to ground estimates only at a spatial scale of about 10 ha or more. Biomass changes were in the same direction at the spatial scale of 1 ha in 60 to 64% of the subplots, corresponding to p values of respectively 0.1 and 0.033. Large errors in estimating biomass changes from lidar data resulted from the uncertainty in detecting changes at 1 ha from ground census data, differences of approximately one year between the ground census and lidar measurements, and differences in sensor characteristics. Our results indicate that the 50 ha BCI plot lost a significant amount of biomass (−0.8 Mg ha−1 yr−1 ± 2.2(SD)) over the past decade (2000–2010). Over the entire island and during the same period, mean AGB change was 0.2 ± 2.4 Mg ha−1 yr−1 with old growth forests losing −0.7 Mg ha−1 yr−1 ± 2.2 (SD), and secondary forests gaining +1.8 Mg ha yr−1 ± 3.4 (SD) biomass. Our analysis suggests that repeated lidar surveys, despite taking measurement with different sensors, can estimate biomass changes in old-growth tropical forests at landscape scales (>10 ha).

scholarly journals Detecting tropical forest biomass dynamics from repeated airborne Lidar measurements

2013 ◽  
Vol 10 (2) ◽  
pp. 1957-1992 ◽  
Author(s):  
V. Meyer ◽  
S. S. Saatchi ◽  
J. Chave ◽  
J. Dalling ◽  
S. Bohlman ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Spatial Scales ◽  
Forest Biomass ◽  
Airborne Lidar ◽  
Barro Colorado Island ◽  
Accurate Estimation ◽  
Prediction Errors ◽  
Old Growth ◽  
Lidar Measurements

Abstract. Reducing uncertainty of terrestrial carbon cycle depends strongly on the accurate estimation of changes of global forest carbon stock. However, this is a challenging problem from either ground surveys or remote sensing techniques in tropical forests. Here, we examine the feasibility of estimating changes of tropical forest biomass from two airborne Lidar measurements acquired about 10 yr apart over Barro Colorado Island (BCI), Panama from high and medium resolution airborne sensors. The estimation is calibrated with the forest inventory data over 50 ha that was surveyed every 5 yr during the study period. We estimated the aboveground forest biomass and its uncertainty for each time period at different spatial scales (0.04, 0.25, 1.0 ha) and developed a linear regression model between four Lidar height metrics and the aboveground biomass. The uncertainty associated with estimating biomass changes from both ground and Lidar data was quantified by propagating measurement and prediction errors across spatial scales. Errors associated with both the mean biomass stock and mean biomass change declined with increasing spatial scales. Biomass changes derived from Lidar and ground estimates were largely (36 out 50 plots) in the same direction at the spatial scale of 1 ha. Lidar estimation of biomass was accurate at the 1 ha scale (R2 = 0.7 and RMSEmean = 28.6 Mg ha−1). However, to predict biomass changes, errors became comparable to ground estimates only at about 10-ha or more. Our results indicate that the 50-ha BCI plot lost a~significant amount of biomass (−0.8 ± 2.2 Mg ha−1 yr−1) over the past decade (2000–2010). Over the entire island and during the same period, mean AGB change is −0.4 ± 3.7 Mg ha−1 yr−1. Old growth forests lost biomass (−0.7 ± 3.5 Mg ha−1 yr−1), whereas the secondary forests gained biomass (+0.4 ± 3.4 Mg ha−1 yr−1). Our analysis demonstrates that repeated Lidar surveys, even with two different sensors, is able to estimate biomass changes in old-growth tropical forests at landscape scales (>10 ha).

The Need to Belong and the Relationship Between Loneliness and Health

2014 ◽  
Vol 22 (4) ◽  
pp. 194-201 ◽  
Author(s):  
Freda-Marie Hartung ◽  
Britta Renner
Keyword(s):  
Individual Differences ◽  
Social Isolation ◽  
Social Situation ◽  
First Year ◽  
Health State ◽  
Need To Belong ◽  
First Year University ◽  
Perceived Social Isolation ◽  
The Impact ◽  
The Relationship

Humans are social animals; consequently, a lack of social ties affects individuals’ health negatively. However, the desire to belong differs between individuals, raising the question of whether individual differences in the need to belong moderate the impact of perceived social isolation on health. In the present study, 77 first-year university students rated their loneliness and health every 6 weeks for 18 weeks. Individual differences in the need to belong were found to moderate the relationship between loneliness and current health state. Specifically, lonely students with a high need to belong reported more days of illness than those with a low need to belong. In contrast, the strength of the need to belong had no effect on students who did not feel lonely. Thus, people who have a strong need to belong appear to suffer from loneliness and become ill more often, whereas people with a weak need to belong appear to stand loneliness better and are comparatively healthy. The study implies that social isolation does not impact all individuals identically; instead, the fit between the social situation and an individual’s need appears to be crucial for an individual’s functioning.

Thathir Quality Scholarship Program For Students At University level

2018 ◽  
Vol 2 (3) ◽  
pp. 206-219
Author(s):  
Louay Qais Abdullah ◽  
Duraid Faris Khayoun
Keyword(s):  
College Students ◽  
Life Sciences ◽  
Economic Feasibility ◽  
First Year ◽  
Grant Program ◽  
Scholarship Program ◽  
University Level ◽  
Faculty Of Education ◽  
The University ◽  
The Relationship

The study focused basically on measuring the relationship between the material cost of the students benefits program and the benefits which are earned by it, which was distributed on college students in the initial stages (matinee) and to show the extent of the benefits accruing from the grant program compared to the material burdens which matched and the extent of success or failure of the experience and its effect from o scientific and side on the Iraqi student through these tough economic circumstances experienced by the country in general, and also trying to find ways of proposed increase or expansion of distribution in the future in the event of proven economic feasibility from the program. An data has been taking from the data fro the Department of Financial Affairs and the Department of Studies and Planning at the University of Diyala with taking an data representing an actual and minimized pattern and questionnaires to a sample of students from the Department of Life Sciences in the Faculty of Education of the University of Diyala on the level of success and failure of students in the first year of the grant and the year before for the purpose of distribution comparison. The importance of the study to measure the extent of interest earned in comparision whit the material which is expenseon the program of grant (grant of students) to assist the competent authorities to continue or not in the program of student grants for the coming years.

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