The impact of light quality and leaf wetness on photosynthesis in north-west Andean tropical montane cloud forest

2005 ◽  
Vol 21 (5) ◽  
pp. 549-557 ◽  
Author(s):  
Matthew Guy Letts ◽  
Mark Mulligan
Keyword(s):  
Cloud Forest ◽  
Net Photosynthesis ◽  
Leaf Wetness ◽  
Total Solar Radiation ◽  
Wet Season ◽  
Lowland Rain Forest ◽  
North West ◽  
Montane Cloud Forest ◽  
The Impact ◽  
Trees And Shrubs

Photosynthesis was limited by low-intensity photosynthetically active radiation (PAR) and leaf wetness in a lower montane cloud forest (LMCF) of Cauca, Colombia. Mean PAR intensity remained below the saturation level for leaf-scale net photosynthesis (Pn) throughout the solar day during the wet season and for most of the solar day during the dry season. PAR represented a smaller fraction of total solar radiation (K↓) in LMCF than in lowland rain forest (LRF). In LMCF trees and shrubs, mean PAR-saturated Pn ranged from 4.3–10.6 μmol C m−2 s−1 at 1450 m, and from 3.5–10.2 μmol C m−2 s−1 at 2150 m. Pn was reduced by abaxial wetness in leaves of some trees and shrubs, and eliminated in others. This study indicates that persistent cloudiness and interception of cloud water by leaves limit LMCF productivity.

scholarly journals Climatic Variability and Wet Season Rice (Oryza sativa L.) Production in North-West Bangladesh

2017 ◽  
Vol 15 (1) ◽  
pp. 68-80 ◽  
Author(s):  
JC Biswas ◽  
MB Hossain ◽  
AK Choudhury ◽  
N Kalra ◽  
M Maniruzzaman
Keyword(s):  
Oryza Sativa ◽  
Rice Yield ◽  
Oryza Sativa L ◽  
Climatic Variability ◽  
Weather Data ◽  
Yield Reduction ◽  
Wet Season ◽  
North West ◽  
Sunshine Hours ◽  
The Impact

Climate change is influencing rice (Oryza sativa L.) production in some agro-ecological regions of Bangladesh. The impact of seasonal climatic variability on rainfed lowland rice (transplanted aman or T. Aman) yield in north-west Bangladesh was analyzed based on historic weather data from 1971 to 2010. Wet season maximum and minimum temperatures were increasing by 0.0174 and 0.0083°C year-1, respectively. Sunshine hours for the same   period have decreased by 0.0259-0.027 hr year-1. The representative concentration pathway (RCP) based projection showed increased maximum and minimum temperatures by 0.42-1.51 and 0.79-1.34°C, respectively in 2050. T. Aman rice yield could be reduced by 0.17-0.37 t ha-1 if temperature rises by 1°C. If sunshine hour decreases by 1 hr, yield reduction could be 0.20 t ha-1. Combined effect of increased minimum temperature and decreased sunshine hours will govern T. Aman rice yield in future.The Agriculturists 2017; 15(1) 68-80

The Paradox of Rattus Tunneyi: Endangerment of a Native Pest.

1996 ◽  
Vol 23 (1) ◽  
pp. 1 ◽  
Author(s):  
RW Braithwaite ◽  
AD Griffiths
Keyword(s):  
Fire Regime ◽  
Wet Season ◽  
North West ◽  
Plant Parts ◽  
The North ◽  
European Colonization ◽  
Riparian System ◽  
The Impact ◽  
North Western ◽  
Population Numbers

An analysis of mark-recapture data for Rattus tunneyi in Kakadu National Park from a 7-year period was performed. Capture rates declined 500-fold during this period. The species exhibits a strong preference for riparian vegetation. The diet is primarily herbivorous, with little insect material. High-nutrient plant parts are generally chosen. Reproduction is most common in the wet season but some breeding extends throughout the year if unseasonal rain occurs during the dry season. Fire regime seems to have little effect on population numbers. The level of groundwater irrigating the riparian system and to a lesser extent current rainfall have a much stronger influence. Museum records show a contraction since European colonization from a near-total continental distribution to one-seventh of its former distribution along the north-west Australian and southern Queensland coast. The contraction from the more arid regions is likely to be due to the impact of introduced mammalian herbivores on the riparian habitats which previously functioned as refuge areas during periods of low water availability. Historically, R. tunneyi is likely to have fluctuated in distribution and abundance throughout the continent. In recent times, this has included irruptions into commercial crops in some areas. The loss of local refuges plus relatively poor powers of dispersal have resulted in the distribution now being fragmented, with the north-western and central east coasts of Australia providing the most significant habitat for the species.

Impact and Challenges of Centres for Education and Community Action in Cameroon’s North West Region

2018 ◽  
Vol 8 (2) ◽  
pp. 51-74
Author(s):  
Fonteh Athanasius Amungwa
Keyword(s):  
Rural Development ◽  
Economic Crisis ◽  
Formal Education ◽  
Community Education ◽  
Sampling Technique ◽  
Community Action ◽  
Structured Interviews ◽  
North West ◽  
West Region ◽  
The Impact

This paper examines the impact of community education and challenges facing Centres for Education and Community Action as a rural development strategy in Cameroon. The study was conducted in the North-West Region of Cameroon, employing field observations, semi-structured interviews with key informants using a convenient sampling technique and through elaborate review of documents. These research instruments were blended into what is termed triangulation and the data collected was analysed descriptively. The main focus of qualitative analysis is to understand the ways in which people act and the accounts that people give for their actions. This paper posits that extreme dependence on the provision of Western formal education cannot solve the problems of a rapidly changing society like Cameroon, which is facing a long-term economic crisis and persistent unemployment issues of graduates. Consequently, education should be redefined in the context of the prevailing economic crisis to make it responsive to the aspirations of rural communities. Findings showed that community education had contributed towards rural development immensely but has suffered many challenges due to neglect of the field in the policy agenda. This paper recommends the integration of community education with formal education to facilitate group and community betterment in particular and rural transformation in general.

Stanowiska reliktowego gatunku Betula humilis (Betulaceae) w Dolinie Górnego Nurca na Nizinie Północnopodlaskiej

2019 ◽  
pp. 161-168
Author(s):  
Aleksander Kołos
Keyword(s):  
Drainage Ditches ◽  
North West ◽  
Hay Meadows ◽  
The North ◽  
South West ◽  
North Eastern ◽  
New Localities ◽  
Western Border ◽  
Betula Humilis ◽  
Trees And Shrubs

Betula humilis Schrank (shrubby birch) is among the most endangered shrub species in Poland. All localities are in the eastern and northern parts of the country, where the species reaches the western border of its geographical range in Europe. Betula humilis is disappearing in Poland due to wetland melioration and shrub succession. Over 80% of the localities described in Poland have not been confirmed in the last 20 years. Five new localities of B. humilis in the North Podlasie Lowland were recorded from 2008 to 2019 in the Upper Nurzec Valley (Fig. 1): 1–1.5 km south-west of Pawlinowo village (in the ATPOL GC7146 plot) and 1.5–2 km north-west of Żuki village (ATPOL GC7155, GC156 and GC166). The population near Pawlinowo (locality 1) is currently composed of ~80 individuals (101 individuals were noted in 2010) and is one of the largest populations in north-eastern Poland. Betula humilis grows there within patches dominated by Salix rosmarinifolia and megaforbs. The population at locality 5 is composed of 18 individuals. At the remaining localities, only 1–4 individuals were found, scattered along drainage ditches surrounded by hay meadows. At some of these localities the species is threatened with extinction. It is suggested to remove competitive trees and shrubs (mainly Populus tremula, Betula pubescens and Salix cinerea) in order to maintain the local populations.

scholarly journals Cable Tensile Forces Associated to Winch Design in Tethered Harvesting Operations: A Case Study from the Pacific North West

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 827
Author(s):  
Omar Mologni ◽  
Eric D. T. Nance ◽  
C. Kevin Lyons ◽  
Luca Marchi ◽  
Stefano Grigolato ◽  
...  
Keyword(s):  
Endurance Limit ◽  
Tensile Force ◽  
Force Analysis ◽  
North West ◽  
The Pacific ◽  
Work Tasks ◽  
Tensile Forces ◽  
System Activation ◽  
The Impact

Cable tensile forces in winch-assist harvesting have been investigated in order to assess the safety concerns of the technology. However, the literature is lacking, particularly in regards to the impact of winch design. In this study, a Summit Winch Assist tethering a feller-director on ground slopes up to 77% was monitored for four days. The cable tensile forces were simultaneously recorded at the harvesting and anchor machine at a frequency of 100 Hz. Cameras and GNSS devices enabled a time study of the operations and the recording of machine positions. Winch functionality and design were disclosed by the manufacturer and used for the interpretation of the results. The cable tensile forces reached 296 kN at the harvesting machine and 260 kN at the anchor machine. The slow negotiation of obstacles while moving downhill recorded the highest peaks, mainly due to threshold settings of the winch in the brake system activation. Lower but significant peaks were also recorded during stationary work tasks. The peaks, however, were limited to a few events and never exceeded the endurance limit of the cable. Overall, the study confirmed recent findings in cable tensile force analysis of active winch-assist operations and provided evidence of the underlaying mechanisms that contribute to cable tensile forces.

scholarly journals Seasonal changes in water quality and macrophytes and the impact of cattle on tropical floodplain waterholes

2012 ◽  
Vol 63 (9) ◽  
pp. 788 ◽  
Author(s):  
N. E. Pettit ◽  
T. D. Jardine ◽  
S. K. Hamilton ◽  
V. Sinnamon ◽  
D. Valdez ◽  
...  
Keyword(s):  
Water Quality ◽  
Seasonal Changes ◽  
Aquatic Macrophyte ◽  
Plant Cover ◽  
Critical Role ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Dry Tropics ◽  
The Impact

The present study indicates the critical role of hydrologic connectivity in floodplain waterholes in the wet–dry tropics of northern Australia. These waterbodies provide dry-season refugia for plants and animals, are a hotspot of productivity, and are a critical part in the subsistence economy of many remote Aboriginal communities. We examined seasonal changes in water quality and aquatic plant cover of floodplain waterholes, and related changes to variation of waterhole depth and visitation by livestock. The waterholes showed declining water quality through the dry season, which was exacerbated by more frequent cattle usage as conditions became progressively drier, which also increased turbidity and nutrient concentrations. Aquatic macrophyte biomass was highest in the early dry season, and declined as the dry season progressed. Remaining macrophytes were flushed out by the first wet-season flows, although they quickly re-establish later during the wet season. Waterholes of greater depth were more resistant to the effects of cattle disturbance, and seasonal flushing of the waterholes with wet-season flooding homogenised the water quality and increased plant cover of previously disparate waterholes. Therefore, maintaining high levels of connectivity between the river and its floodplain is vital for the persistence of these waterholes.

Diversity and vertical distribution of epiphytic liverworts in lowland rain forest and lowland cloud forest of French Guiana

2013 ◽  
Vol 35 (4) ◽  
pp. 243-254 ◽  
Author(s):  
Christine Gehrig-Downie ◽  
André Obregon ◽  
Jörg Bendix ◽  
Robbert Gradstein
Keyword(s):  
Vertical Distribution ◽  
Rain Forest ◽  
French Guiana ◽  
Cloud Forest ◽  
Lowland Rain Forest

scholarly journals Second World War conflict archaeology in the forests of north-west Europe

Antiquity ◽  
2014 ◽  
Vol 88 (342) ◽  
pp. 1275-1290 ◽  
Author(s):  
David G. Passmore ◽  
Stephan Harrison ◽  
David Capps Tunwell
Keyword(s):  
Second World War ◽  
Recent Survey ◽  
Support Structures ◽  
World War ◽  
Conflict Archaeology ◽  
North West ◽  
Military Support ◽  
The Impact ◽  
Second World

Concrete fortifications have long served as battle-scarred memorials of the Second World War. The forests of north-west Europe, meanwhile, have concealed a preserved landscape of earthwork field fortifications, military support structures and bomb- and shell-craters that promise to enhance our understanding of the conflict landscapes of the 1944 Normandy Campaign and the subsequent battles in the Ardennes and Hürtgenwald forests. Recent survey has revealed that the archaeology surviving in wooded landscapes can significantly enhance our understanding of ground combat in areas covered by forest. In particular, this evidence sheds new light on the logistical support of field armies and the impact of Allied bombing on German installations.

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