scholarly journals Seasonal and successional dynamics of size-dependent plant demographic rates in a tropical dry forest

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9636
Author(s):  
Irving Saenz-Pedroza ◽  
Richard Feldman ◽  
Casandra Reyes-García ◽  
Jorge A. Meave ◽  
Luz Maria Calvo-Irabien ◽  
...  
Keyword(s):  
Climate Change ◽  
Tropical Forests ◽  
Dry Season ◽  
Dry Forest ◽  
Species Density ◽  
Wet Season ◽  
Successional Stage ◽  
Size Dependent ◽  
Demographic Rates ◽  
Successional Stages

Tropical forests are globally important for biodiversity conservation and climate change mitigation but are being converted to other land uses. Conversion of seasonally dry tropical forests (SDTF) is particularly high while their protection is low. Secondary succession allows forests to recover their structure, diversity and composition after conversion and subsequent abandonment and is influenced by demographic rates of the constituent species. However, how these rates vary between seasons for different plant sizes at different successional stages in SDTF is not known. The effect of seasonal drought may be more severe early in succession, when temperature and radiation are high, while competition and density-dependent processes may be more important at later stages, when vegetation is tall and dense. Besides, the effects of seasonality and successional stage may vary with plant size. Large plants can better compete with small plants for limiting resources and may also have a greater capacity to withstand stress. We asked how size-dependent density, species density, recruitment and mortality varied between seasons and successional stages in a SDTF. We monitored a chronosequence in Yucatan, Mexico, over six years in three 0.1 ha plots in each of three successional stages: early (3–5 years-old), intermediate (18–20 years-old) and advanced (>50 years-old). Recruitment, mortality and species gain and loss rates were calculated from wet and dry season censuses separately for large (diameter > 5 cm) and small (1–5 cm in diameter) plants. We used linear mixed-effects models to assess the effects of successional stage, seasonality and their changes through time on demographic rates and on plant and species density. Seasonality affected demographic rates and density of large plants, which exhibited high wet-season recruitment and species gain rates at the early stage and high wet-season mortality at the intermediate stage, resulting in an increase in plant and species density early in succession followed by a subsequent stabilization. Small plant density decreased steadily after only 5 years of land abandonment, whereas species density increased with successional stage. A decline in species dominance may be responsible for these contrasting patterns. Seasonality, successional stage and their changes through time had a stronger influence on large plants, likely because of large among-plot variation of small plants. Notwithstanding the short duration of our study, our results suggest that climate-change driven decreases in rainy season precipitation may have an influence on successional dynamics in our study forest as strong as, or even stronger than, prolonged or severe droughts during the dry season.

scholarly journals Fruiting phenology and consumption by birds in Ficus calyptroceras (Miq.) Miq. (Moraceae)

2002 ◽  
Vol 62 (2) ◽  
pp. 339-346 ◽  
Author(s):  
J. RAGUSA-NETTO
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Dry Season ◽  
Dry Forest ◽  
Wet Season ◽  
Frugivorous Birds ◽  
Fruiting Phenology ◽  
Dry Seasons ◽  
Seed Dispersers ◽  
Wet And Dry Seasons

Figs are a remarkable food resource to frugivores, mainly in periods of general fruit scarcity. Ficus calyptroceras Miq. (Moraceae) is the only fig species in a type of dry forest in western Brazil. In this study I examined the fruiting pattern as well as fig consumption by birds in F. calyptroceras. Although rainfall was highly seasonal, fruiting was aseasonal, since the monthly proportion of fruiting trees ranged from 4% to 14% (N = 50 trees). I recorded 22 bird species feeding on figs. In the wet season 20 bird species ate figs, while in the dry season 13 did. Parrots were the most important consumers. This group removed 72% and 40% of the figs consumed in the wet and dry seasons, respectively. No bird species increases fig consumption from dry to wet season. However, a group of bird species assumed as seed dispersers largely increases fig consumption from wet to dry season, suggesting the importance of this resource in the period of fruit scarcity. The results of this study points out the remarkable role that F. calyptroceras plays to frugivorous birds, in such a dry forest, since its fruits were widely consumed and were available all year round.

scholarly journals Characterization of Dry-Season Phenology in Tropical Forests by Reconstructing Cloud-Free Landsat Time Series

2021 ◽  
Vol 13 (23) ◽  
pp. 4736
Author(s):  
Xiaolin Zhu ◽  
Eileen H. Helmer ◽  
David Gwenzi ◽  
Melissa Collin ◽  
Sean Fleming ◽  
...  
Keyword(s):  
Time Series ◽  
Puerto Rico ◽  
Tropical Forests ◽  
Tropical Dry Forest ◽  
Dry Season ◽  
Dry Forest ◽  
High Quality ◽  
Forest Zone ◽  
Fine Resolution ◽  
Field Plots

Fine-resolution satellite imagery is needed for characterizing dry-season phenology in tropical forests since many tropical forests are very spatially heterogeneous due to their diverse species and environmental background. However, fine-resolution satellite imagery, such as Landsat, has a 16-day revisit cycle that makes it hard to obtain a high-quality vegetation index time series due to persistent clouds in tropical regions. To solve this challenge, this study explored the feasibility of employing a series of advanced technologies for reconstructing a high-quality Landsat time series from 2005 to 2009 for detecting dry-season phenology in tropical forests; Puerto Rico was selected as a testbed. We combined bidirectional reflectance distribution function (BRDF) correction, cloud and shadow screening, and contaminated pixel interpolation to process the raw Landsat time series and developed a thresholding method to extract 15 phenology metrics. The cloud-masked and gap-filled reconstructed images were tested with simulated clouds. In addition, the derived phenology metrics for grassland and forest in the tropical dry forest zone of Puerto Rico were evaluated with ground observations from PhenoCam data and field plots. Results show that clouds and cloud shadows are more accurately detected than the Landsat cloud quality assessment (QA) band, and that data gaps resulting from those clouds and shadows can be accurately reconstructed (R2 = 0.89). In the tropical dry forest zone, the detected phenology dates (such as greenup, browndown, and dry-season length) generally agree with the PhenoCam observations (R2 = 0.69), and Landsat-based phenology is better than MODIS-based phenology for modeling aboveground biomass and leaf area index collected in field plots (plot size is roughly equivalent to a 3 × 3 Landsat pixels). This study suggests that the Landsat time series can be used to characterize the dry-season phenology of tropical forests after careful processing, which will help to improve our understanding of vegetation–climate interactions at fine scales in tropical forests.

scholarly journals Future Climate Change Renders Unsuitable Conditions for Paramo Ecosystems in Colombia

2020 ◽  
Vol 12 (20) ◽  
pp. 8373
Author(s):  
Matilda Cresso ◽  
Nicola Clerici ◽  
Adriana Sanchez ◽  
Fernando Jaramillo
Keyword(s):  
Climate Change ◽  
Greenhouse Gas Emission ◽  
Dry Season ◽  
Capital City ◽  
Maximum Temperature ◽  
Future Climate Change ◽  
Mountain Range ◽  
Wet Season ◽  
Temperature And Precipitation ◽  
The Future

Paramo ecosystems are tropical alpine grasslands, located above 3000 m.a.s.l. in the Andean mountain range. Their unique vegetation and soil characteristics, in combination with low temperature and abundant precipitation, create the most advantageous conditions for regulating and storing surface and groundwater. However, increasing temperatures and changing patterns of precipitation due to greenhouse-gas-emission climate change are threatening these fragile environments. In this study, we used regional observations and downscaled data for precipitation and minimum and maximum temperature during the reference period 1960–1990 and simulations for the future period 2041–2060 to study the present and future extents of paramo ecosystems in the Chingaza National Park (CNP), nearby Colombia’s capital city, Bogotá. The historical data were used for establishing upper and lower precipitation and temperature boundaries to determine the locations where paramo ecosystems currently thrive. Our results found that increasing mean monthly temperatures and changing precipitation will render 39 to 52% of the current paramo extent in CNP unsuitable for these ecosystems during the dry season, and 13 to 34% during the wet season. The greatest loss of paramo area will occur during the dry season and for the representative concentration pathway (RCP) scenario 8.5, when both temperature and precipitation boundaries are more prone to be exceeded. Although our initial estimates show the future impact on paramos and the water security of Bogotá due to climate change, complex internal and external interactions in paramo ecosystems make it essential to study other influencing climatic parameters (e.g., soil, topography, wind, etc.) apart from temperature and precipitation.

Downscaled Climate Change Projections for Wa District in the Savanna Zone of Ghana

2014 ◽  
Vol 9 (4) ◽  
pp. 422-431 ◽  
Author(s):  
Emmanuel Tachie-Obeng ◽  
◽  
Bruce Hewitson ◽  
Edwin Akonno Gyasi ◽  
Mark Kofi Abekoe ◽  
...  
Keyword(s):  
Climate Change ◽  
Local Level ◽  
Control Period ◽  
Dry Season ◽  
Future Climate ◽  
Future Climate Change ◽  
Wet Season ◽  
Annual Variations ◽  
Near Future ◽  
Savanna Zone

The possibility of future climate change in Ghana has received much attention due to repeated droughts and floods over the last decades. The savanna zone which is described as the food basket of Ghana is highly susceptible to climate change impact. Scenarios from 20-year time slices of the near future – 2046-2065 – and the far future – 2081-2100 – climate change meant to help guide policy remain a challenge. Empirical downscaling performed at the local-scale of Wa District in the savanna zone of Ghana under the IPCC A2 SRES emissions scenario showed evidence of probable climate change with mean annual temperatures expected to increase over an estimated range of 1.5°C to 2.3°C in the near future, with number of cool nights becoming less frequent, especially during the Harmattan1 period. The dry season is expected to be warmer than the wet season, with high inter-annual variations projected in both maximum (Tmax) and minimum (Tmin) temperatures. Given an average of 1 day of Tmax > 40°C per month in the control period of 1961-2000, the number of hot days is expected to increase to 12 by 2046-2065. An increase in total rainfall is projected with possible shifts in distribution toward the end of the year, with a slight increase in rainfall during the dry season and an increase of rainfall at the onset and toward the end of the wet season. However, a decrease in June rainfall is projected in the wet season. The objective of this paper is to improve the understanding of future climate as a guide to local level medium-term development plans of effective adaptation options for Wa district in the savanna zone of Ghana.

Effect of the red land crab (Gecarcinus lateralis) on leaf litter in a tropical dry forest in Veracruz, Mexico

1993 ◽  
Vol 9 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Martin Kellman ◽  
Bianca Delfosse
Keyword(s):  
Leaf Litter ◽  
Seasonal Pattern ◽  
Coastal Dunes ◽  
Dry Season ◽  
Dry Forest ◽  
Wet Season ◽  
Nutrient Pools ◽  
Land Crab ◽  
Litter Biomass ◽  
Gecarcinus Lateralis

ABSTRACTThe effect of the red land crab (Gecarcinus lateralis) on leaf litter biomass and nutrient transformation was investigated in a semi-deciduous tropical forest on coastal dunes using access and exclusion plots observed for six months. Crabs were in burrows during drought, but began foraging immediately after rainfall. Crabs accelerated litter disappearance significantly during the wet season at one site located beneath Brosimum alicastrum, but had no effect beneath a nearby Enterolobium cyclocarpum. The difference is tentatively attributed to small leaflet size in the latter species which crabs were unable to handle and consume. At both sites, litter in exdosures had approximately doubled by the end of the ensuing dry season. At the Brosimum site it is attributed to sporadic crab detritivory occurring after dry seasonal rains. At the Enterolobium site it is attributed to preferential retention of litter in the cxclosures during strong dry season winds. The nutrient content of litter exposed to, or protected from, crabs was not significantly different at either site and differences in litter nutrient pools reflected differences in litter biomass. Accelerated nutrient mineralization due to crab detritivory was concentrated early in the wet season before leaching began from the soils, and it is suggested that this altered seasonal pattern of mineralization may reduce the loss of nutrients from the site in percolating water.

scholarly journals Total OH reactivity over the Amazon rainforest: variability with temperature, wind, rain, altitude, time of day, season, and an overall budget closure

2021 ◽  
Vol 21 (8) ◽  
pp. 6231-6256
Author(s):  
Eva Y. Pfannerstill ◽  
Nina G. Reijrink ◽  
Achim Edtbauer ◽  
Akima Ringsdorf ◽  
Nora Zannoni ◽  
...  
Keyword(s):  
Tropical Forests ◽  
Time Of Day ◽  
Green Leaf Volatiles ◽  
Dry Season ◽  
Amazon Forest ◽  
Wet Season ◽  
Leaf Volatiles ◽  
Transition Season ◽  
Wide Range ◽  
Volatile Organic

Abstract. The tropical forests are Earth's largest source of biogenic volatile organic compounds (BVOCs) and thus also the largest atmospheric sink region for the hydroxyl radical (OH). However, the OH sink above tropical forests is poorly understood, as past studies have revealed large unattributed fractions of total OH reactivity. We present the first total OH reactivity and volatile organic compound (VOC) measurements made at the Amazon Tall Tower Observatory (ATTO) at 80, 150, and 320 m above ground level, covering two dry seasons, one wet season, and one transition season in 2018–2019. By considering a wide range of previously unaccounted for VOCs, which we identified by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS), the unattributed fraction was with an overall average of 19 % within the measurement uncertainty of ∼ 35 %. In terms of seasonal average OH reactivity, isoprene accounted for 23 %–43 % of the total and oxygenated VOCs (OVOCs) for 22 %–40 %, while monoterpenes, sesquiterpenes, and green leaf volatiles combined were responsible for 9 %–14 %. These findings show that OVOCs were until now an underestimated contributor to the OH sink above the Amazon forest. By day, total OH reactivity decreased towards higher altitudes with strongest vertical gradients observed around noon during the dry season (−0.026 s−1 m−1), while the gradient was inverted at night. Seasonal differences in total OH reactivity were observed, with the lowest daytime average and standard deviation of 19.9 ± 6.2 s−1 during a wet–dry transition season with frequent precipitation; 23.7 ± 6.5 s−1 during the wet season; and the highest average OH reactivities during two dry-season observation periods with 28.1 ± 7.9 s−1 and 29.1 ± 10.8 s−1, respectively. The effects of different environmental parameters on the OH sink were investigated, and quantified, where possible. Precipitation caused short-term spikes in total OH reactivity, which were followed by below-normal OH reactivity for several hours. Biomass burning increased total OH reactivity by 2.7 to 9.5 s−1. We present a temperature-dependent parameterization of OH reactivity that could be applied in future models of the OH sink to further reduce our knowledge gaps in tropical-forest OH chemistry.

scholarly journals Future Changes in Wet and Dry Season Characteristics in CMIP5 and CMIP6 simulations

2021 ◽  
Author(s):  
Caroline M. Wainwright ◽  
Emily Black ◽  
Richard P. Allan
Keyword(s):  
Climate Change ◽  
South America ◽  
West Africa ◽  
Southern Africa ◽  
Dry Season ◽  
Maximum Temperature ◽  
Wet Season ◽  
Dry Spells ◽  
Dry Spell ◽  
Spell Length

AbstractClimate change will result in more dry days and longer dry spells, however, the resulting impacts on crop growth depend on the timing of these longer dry spells in the annual cycle. Using an ensemble of Coupled Model Intercomparison Project Phase 5 and Phase 6 (CMIP5 and CMIP6) simulations, and a range of emission scenarios, here we examine changes in wet and dry spell characteristics under future climate change across the extended tropics in wet and dry seasons separately. Delays in the wet seasons by up to two weeks are projected by 2070-2099 across South America, Southern Africa, West Africa and the Sahel. An increase in both mean and maximum dry spell length during the dry season is found across Central and South America, Southern Africa and Australia, with a reduction in dry season rainfall also found in these regions. Mean dry season dry spell lengths increase by 5-10 days over north-east South America and south-west Africa. However, changes in dry spell length during the wet season are much smaller across the tropics with limited model consensus. Mean dry season maximum temperature increases are found to be up to 3°C higher than mean wet season maximum temperature increases over South America, Southern Africa and parts of Asia. Longer dry spells, fewer wet days, and higher temperatures during the dry season may lead to increasing dry season aridity, and have detrimental consequences for perennial crops.

scholarly journals SOIL FAUNA AND LEAF LITTER DECOMPOSITION IN DIFFERENT SUCCESSIONAL STAGES OF A SUBMOUNTAINOUS SEASONAL SEMIDECIDUOUS FOREST

FLORESTA ◽  
2021 ◽  
Vol 51 (2) ◽  
pp. 429
Author(s):  
Rodrigo Camara ◽  
Marcos Gervasio Pereira ◽  
Luciano Oliveira Toledo ◽  
Carlos Eduardo Gabriel Menezes
Keyword(s):  
Leaf Litter ◽  
Litter Decomposition ◽  
Soil Fauna ◽  
Dry Season ◽  
Leaf Litter Decomposition ◽  
Successional Stage ◽  
Semideciduous Forest ◽  
Litter Bags ◽  
Successional Stages ◽  
Seasonal Semideciduous Forest

In tropical forests, the stage of ecological succession influences the nutrient cycling. This study aimed to analyze soil fauna community structure, composition, and leaf litter decomposition in fragments of intermediate-successional and late-successional Submountainous Seasonal Semideciduous Forest (ISF and LSF, respectively). We used a square metal frame to collect 10 samples of the leaf litter layer and surface soil (0.00-0.05 m depth) from each area in the wet and dry seasons. Soil fauna individuals were then extracted using a modified Berlese-Tüllgren funnel. For analysis of leaf litter decomposition, 15 litter bags containing 30 g of senescent leaves were randomly placed on the forest floor of each area in the dry season, and three bags were collected after 60, 90, 120, 150, and 180 days. LSF presented higher value of richness and was more associated with Diptera and Formicidae. There was no clear pattern in evenness and diversity with successional stage. The dissimilarity between ISF and LSF in terms of soil fauna community was greater in the dry season. Litter decomposition was almost identical in both areas.

Analyzing Land Use Impacts on Streamflow Response in a Tropical Watershed: A Hydrometric and Geochemical Approach

2020 ◽  
Author(s):  
Nicola Mathura ◽  
Kegan Farrick
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Critical Zone ◽  
Dry Season ◽  
Future Climate Change ◽  
Wet Season ◽  
Forested Catchment ◽  
Streamflow Response ◽  
The Caribbean ◽  
Geochemical Approach

<p>Climate change and unsustainable land use practices such as quarrying have the potential to negatively impact the hydrology and water resource availability in catchments. Throughout the Caribbean, hillside quarrying has become a common practice. While these activities remove large sections of the critical zone, very little work has been done on how hillside quarrying impacts storm response and catchment water storage.  The study is particularly important given the expected changes to rainfall patterns in the Caribbean under future climate change. We hypothesised that the removal of the critical zone during quarrying will increase the magnitude of streamflow response to storm events due to its close proximity to the river, while also reducing the overall storage of the watershed. This study utilized a hydrometric and geochemical approach with direct measurements of rainfall and streamflow, and bi-weekly water sample collections for geochemistry and <sup>18</sup>O and <sup>2</sup>H stable isotopes between the 3.6 km<sup>2</sup> Acono (forested) and the adjacent 3.6 km<sup>2</sup> Don Juan (quarried) watersheds, located in Trinidad and Tobago. A total of 1207 mm of rainfall occurred, with 87.3% falling from August to November (wet season) and 12.7% from December to March (dry season). The δ<sup> 18</sup>O in rainfall ranged from -7.7 to 0.3 ‰ across both seasons with an average δ<sup>18</sup>O of -3.5±1.8‰ during the wet season and 0.1±0.5‰ in the dry season. During the dry season the mean δ<sup> 18</sup>O of stream water showed a difference between the forested (-2.8±0.3‰) and quarried (-3.1±0.3‰) catchments whereas there was little differences in δ<sup>18</sup>O in the forested catchment (-3.3±0.3 ‰) and quarried catchment–(-3.2±0.27‰) in the wet season. Our stream δ<sup>18</sup>O dry season results suggests that different sources of water or anthropogenic influences such as water from settling ponds in the quarry could have impacted the δ<sup>18</sup>O of the quarried stream as we expected the forested catchment to be more stable. Sample collection at these sites is ongoing and additional parameters such as soil water isotopes and rainfall, soil and stream ion chemistry are expected to improve our understanding of the translation from rainfall to streamflow. This research will allow us to gain a better insight of the current hydrological processes within this catchment and aid in the long term adaptive planning for factors such as climate change and further land use change.</p><p> </p>

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