הלמן דוד

ד"ר
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תחומי מחקר: 
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קורות חיים

Education

2012 – 2016           PhD.

Department of Geography and Environment - Bar Ilan University, Israel. Advisors:

Prof. Itamar Lensky (Bar-Ilan University), Prof. Dan Yakir (Weizmann Institute of

Science) and Dr. Yagil Osem (Agricultural Research Organization – ARO).

Dissertation: The water use and water use efficiency of Mediterranean forests

assessed by satellite remote sensing.

2002 – 2004          M.Sc.

Environmental and Earth Sciences – The Hebrew University of Jerusalem, Israel,

supervised by Prof. Yigal Erel. Topic: The effect of climatic parameters on the

release of Pb and Sr isotopes during the dissolution of Granites (Geochemistry).

1998 – 2002          B.Sc.

Geology. Institute of Earth Sciences - The Hebrew University of Jerusalem, Israel.

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Professional experience

2011 –                   Computer programming and research assistant in the Remote sensing lab.

                              Department of Geography and Environment - Bar Ilan University.

2002 – 2004          Courses teaching in: Geochemistry; Soil Sciences; Computer skills – Institute of

                              Earth Sciences, The Hebrew University of Jerusalem, Israel.

2002 – 2004          Clean laboratory for trace metals and isotopic composition analyses – Institute of

                              Earth Sciences, The Hebrew University of Jerusalem, Israel.

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Awards and Scholarships

2015 – 2017          Israel Water Authority scholarship

2014 – 2015          The Rieger Foundation, USA: Marshall Tulin Fellowship program for

                               environmental studies (1 year)

2013 – 2014          The Ministry of Agriculture and Rural Development scholarship

2012 – 2016           Bar Ilan Presidential scholarship for excellent Ph.D. candidates   

2002 – 2004           Environmental and Earth Sciences scholarship for excellent M.Sc. students, The

                               Hebrew University of Jerusalem.

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* Find a more detailed CV here

 

 

תחומי התמחות

Research fields

My main interests are in the fields of Biogeochemistry and Eco-hydrology. I am studying how climate affects biogeochemical and hydrological processes in terrestrial natural and agricultural vegetation systems. I am also seeking to understand how vegetation functioning and dynamics interact with different human systems.

I use process-driven numerical models, remote sensing (RS) tools, as well as numerous field techniques to study those systems. Using such tools may help us deepen our knowledge on eco-hydrological and biogeochemical processes occurring in terrestrial ecosystems. Using numerical models and RS tools concerns regarding climate change and land cover effects on these processes can be addressed. It enables us forecasting potential future atmospheric feedback. Combining these tools with statistical methods enables us forecasting feedbacks from/on human systems.

With help of others, I have developed empirical and biophysical models using satellite information for continuously monitoring vegetation dynamics and processes. For example, the empirical PaVI-E and  biophysical RS-Met models were developed to assess actual evapotranspiration (ET) and CO2-uptake in natural Mediterranean ecosystems at a moderate spatial resolution of 250-m. A phenology-based method for monitoring woody and herbaceous vegetation dynamics at a sub-pixel scale was also developed based on time series analysis of MODIS-derived vegetation indices.

We use these tools to explore changes in vegetation composition, ecosystem fluxes, water yield (WY = Rain-ET) and water use efficiency (WUE = carbon/ET) in Mediterranean forests and woodlands. It helped us identifying underlying factors affecting these important parameters.

Currently, I am involved in a COST (European Cooperation in Science and Technology) Action on 'Harmonization of Unmanned Aerial System (UAS) techniques for agricultural and natural ecosystems monitoring' as the vice-leader of WG3 on soil water content monitoring.

If you are interested in one of those fields or just curious about what I am doing, you are welcome to contact me and visit my personal web.

 

פרסומים

Publications

13.  Manfreda Salvatore*, McCabe M, Miller P, Lucas R, Pajuelo Madrigal V, Mallinis G, Ben-Dor E, Helman David, Estes L, Ciraolo G, Müllerová J, Tauro F, De Lima M I, De Lima J L, Frances F, Caylor K, Kohv M, Maltese A, Perks M, Ruiz-Pérez G, Su Z, Vico G, Toth B., 2018. On the use of Unmanned Aerial Systems for environmental monitoring. Remote Sensing, 10(4), 641, 1–28. doi: 10.3390/rs10040641.

12.  Blum Moshe, Nestel David, Cohen Yafit, Goldshtein Eitan, Helman David and Lensky Itamar*., 2018. Predicting Heliothis (Helicoverpa armigera) pest population dynamics with an age-structured insect population model driven by satellite data. Ecological Modelling, 369, 1–12. doi.org/10.1016/j.ecolmodel.2017.12.019

11.  Helman David*, Leu Stefan and Mussery Amir*., 2017. Contrasting effects of two Acacia species on understorey growth in a drylands environment: Interplay of canopy shading and litter interference. Journal of Vegetation Science, 28, 1140–1150. doi:10.1111/jvs.12576

10.  Helman David*, 2018. Land surface phenology: What do we really ‘see’ from space? Science of the Total Environment, 618, 665–673. https://doi.org/10.1016/j.scitotenv.2017.07.237.

9.  David Helman, Itamar M. Lensky, Yagil Osem,  Shani Rohatyn, Eyal Rotenberg, and Dan Yakir, 2017: A biophysical approach using drought stress factor for daily estimations of evapotranspiration and CO2 uptake in high-energy water-limited environments, Biogeosciences, 14, 3909-3926, https://doi.org/10.5194/bg-14-3909-2017.

8.  Mussery Amir, Helman David*, Leu Stefan, and Budovsky Arie., 2016. Modeling herbaceous productivity considering tree-grass interactions in drylands savannah: The case study of Yatir farm in the Negev drylands. Journal of Arid Environment, 124, 160-164.

7.  David Helman, Yagil Osem, Dan Yakir, and Itamar M. Lensky 2016: Relationships between climate, topography, water use and productivity in two key Mediterranean forest types with different water- use strategies. Agricultural and Forest Meteorology, 232, 319-330.

6.  David Helman, Itamar M. Lensky, Dan Yakir, and Yagil Osem 2016: Forests growing under dry conditions have higher hydrological resilience to drought than do more humid forests. Glob Change Biol. doi:10.1111/gcb.13551.

5.  David Helman, Itamar M. Lensky, Naama Tessler and Yagil Osem, 2015: A phenology-based method for monitoring annual and perennial vegetation in Mediterranean forests from NDVI time series. Remote Sensing, 20157(9), 12314-12335; doi:10.3390/rs7091231

4.  David Helman, Amir Givati, and Itamar M. Lensky, 2015: Annual evapotranspiration retrieved solely from satellites’ vegetation indices for the Eastern MediterraneanAtmospheric Chemistry and Physics, 15, 12567-12579. doi:10.5194/acp-15-12567-2015

3.   Orit Rotem-Mindali, Yaron Michael, David Helman and Itamar M. Lensky, 2015. The role of local land-use on the urban heat island effect of Tel Aviv as assessed from satellite remote sensing. Applied Geography, 56, 145 – 153.

2.   David Helman, Itamar M. Lensky, Amir Mussery and Stefan Leu., 2014. Rehabilitating degraded drylands by creating woodland islets: Assessing long-term effects on aboveground productivity and soil fertility. Agricultural and Forest Meteorology, 195-196, 52 – 60.

1.   David Helman, Amir Mussery, Itamar M. Lensky and Stefan Leu., 2014. Detecting changes in biomass productivity in a different land management regimes in drylands using satellite-derived vegetation index. Soil Use and Management, 30(1), 32 – 39.

מחקר

PhD thesis

Title: "The water use and water use efficiency of Mediterranean forests assessed by satellite remote sensing"

Advisor:           Prof. Itamar Lensky (Bar-Ilan University)

Co-advisors:    Dr Yagil Osem (Agricultural Research Organization - Volcani center)

                        Prof. Dan Yakir (Weizman Institute of Science)


To read more about my research