LTER site established at Yatir semi-arid forest in 2010.
Site manager: Tamir Klein
Research station manager: Dan Yakir
Contact: Tamir Klein
Operating Organization: KKL
General Site Description:
The Yatir Research site was set up in 2000 at the center of the Yatir Forest, a 2’800 ha afforestation system of mainly P. halepensis trees, and is located on the southern end of the Hebron mountain range and at the northern edge of the Negev desert (31° 20’ N; 35° 3’ E; elevation 600 to 850 meters above sea level). Most of the area was planted during the 1960s-1970s. The site is located in the transition zone between the semi-arid and arid Mediterranean climates. Average air temperature for January and July is 10 and 25°C, respectively. Mean annual potential ET is 1600 mm, and mean annual precipitation is 285 mm. Only winter precipitation occurs in this region, creating a distinctive wet season (winter, December to March) and an extended dry season (summer, June to October), with short transition periods between them: a wetting season (autumn) and a drying season (spring). Research in the site mainly focuses on ecophysiology and ecohydrology, energy, carbon and water budgets, influence of stand density (through manipulation experiments), boundary layer dynamics and ecosystem interactions with the climate.
Purpose of Site:
The Yatir Project, initiated in 2000, aims to focus on the complex impact of land use changes, such as afforestation, on carbon sequestration potential, surface temperature (energy budget), and water yield (the difference between precipitation and loss by evapotranspiration). Understanding these aspects and the unavoidable tradeoffs among them are often neglected, especially in the semi-arid region. But their knowledge should be used as a critical tool in formulating national and regional water and carbon management policies. Quantitative knowledge of these tradeoffs should also help in better understanding biosphere-atmosphere interactions on the global scale. Land use changes in Israel (from extensive tree cover ~10,000 years ago to today’s intensive agriculture) significantly altered water yield. The main consequences are increases in runoff, contributing to floods, erosion and loss of fertile soils. Evapotranspiration provides the driving force for forest growth and carbon sequestration (coupled with other factors). Using the Yatir forest as a case study, we have demonstrated that the semi-arid zone has, in fact, greater potential than initially expected for carbon sequestration. In addition to the obvious tradeoffs between water yield and carbon sequestration, afforestation in the semi-arid region also has significant effects on surface temperatures. On sufficiently large scales, such changes in surface energy budget can influence local climate. Changes in forest cover due to climate change or human activities, have therefore complex but important consequences for water, carbon and the local environment that are poorly understood at present. Such changes could feed-back on the atmosphere and climate system. The aim of the Yatir site is to significantly advance our knowledge on this front in a typical semi-arid environment.
The LTER experiment in Yatir forest, established at 2010, was aimed to test the effects of stand density and livestock grazing on tree performance and forest dynamics.
History of site:
The first trees were planted in 1960s-1970s by the Jewish National Fund (JNF/קק”ל). It is named after an ancient Levite city within its territory, Yatir (Book of Joshua 21:13-14). Millions of trees have been planted, mostly coniferous trees – Aleppo Pine and Cypress, but also some broad-leafed trees, e.g. Eucalyptus and Acacia, as well as vineyards and various shrubs, and the forest is still being extended through JNF plantations as of 2016. Yatir Forest has changed the arid landscape of the northern Negev, halting the desertification on the heights northeast of Beersheba. On relatively flat terrain of even trees’ age and within ~0.5 km from the permanent research flux tower, fifteen plots of 0.5 ha were defined (70×70 m or 50×110 m), with a buffer zone of 15 m from each side of the quadrilateral to limit external impacts (Fig. S1). During 2009 the plots were thinned to form three stand density levels; five plots remained unthinned to simulate the average 300 trees ha-1 density level of the forest, five plots were thinned into a moderate density of 200 trees ha-1 and five plots were thinned into a low density of 100 trees ha-1. In 2010-2011, each plot was divided into two (0.25 ha each) to examine the grazing effect; One part of the plot was fenced to exclude the entrance of grazers, and the second part remained accessible. Two parallel 30×4 m transects were defined in each part of the plot, facing east to west. Along these transects, annual measurement surveys are performed.
For major parameters measured at the Yair research station, reported according to the eLTER standard, please see the attached Excel sheet. Parameters monitored regularly at the LTER experiment are:
Radial pine stem growth
Annual pine needle growth
Leaf area index
Pine fine root production
Pine germination, seedling survival and growth
Annual grass biomass production
Understory woody plant cover
Soil moisture and water potential
Publications specific for the Yatir LTER experiment:
- Pozner, E., Bar-On, P., Livne-Luzon, S., Moran, U., Tsamir-Rimon, M., Dener, E., … & Klein, T. (2022). A hidden mechanism of forest loss under climate change: The role of drought in eliminating forest regeneration at the edge of its distribution. Forest Ecology and Management, 506, 119966.
- Tsamir, M., Gottlieb, S., Preisler, Y., Rotenberg, E., Tatarinov, F., Yakir, D., … & Klein, T. (2019). Stand density effects on carbon and water fluxes in a semi-arid forest, from leaf to stand-scale. Forest Ecology and Management, 453, 117573.
- Additionally, research in Yatir forest yielded 352 publications along the years. The ten most recent publications from Yatir forest are:
- Qubaja, R., Moinester, M., & Kronfeld, J. (2022). Potential Global Sequestration of Atmospheric Carbon Dioxide by Semi-Arid Forestation. arXiv preprint arXiv:2205.10641.
- Preisler, Y., Hölttä, T., Grünzweig, J. M., Oz, I., Tatarinov, F., Ruehr, N. K., … & Yakir, D. (2022). The importance of tree internal water storage under drought conditions. Tree physiology, 42(4), 771-783.
- Wagner, Y., Feng, F., Yakir, D., Klein, T., & Hochberg, U. (2022). In situ, direct observation of seasonal embolism dynamics in Aleppo pine trees growing on the dry edge of their distribution. New Phytologist.
- Dubinin, M. V., Osem, Y., Yakir, D., & Paz-Kagan, T. Linking between Water Use Efficiency and Leaf Area Index Along an Aridity Gradient in Dryland Forests. Available at SSRN 4124944.
- Thakur, G., Schymanski, S. J., Mallick, K., Trebs, I., & Sulis, M. (2022). Downwelling longwave radiation and sensible heat flux observations are critical for surface temperature and emissivity estimation from flux tower data. Scientific reports, 12(1), 1-14.
- Yakir, D., Lintunen, A., Preisler, Y., Oz, I., Vesala, T., & Hölttä, T. (2021). Bark transpiration rates can reach needle transpiration rates under dry conditions in a semi-arid forest. Frontiers in plant science, 12.
- Rotenberg, E., Qubaja, R., Preisler, Y., Yakir, D., & Tatarinov, F. (2021). Carbon and Energy Balance of Dry Mediterranean Pine Forests: A Case Study. In Pines and Their Mixed Forest Ecosystems in the Mediterranean Basin (pp. 279-301). Springer, Cham.
- Muller, J. D., Rotenberg, E., Tatarinov, F., Oz, I., & Yakir, D. (2021). Evidence for efficient nonevaporative leaf‐to‐air heat dissipation in a pine forest under drought conditions. New Phytologist, 232(6), 2254-2266.
- Nadal‐Sala, D., Grote, R., Birami, B., Lintunen, A., Mammarella, I., Preisler, Y., … & Ruehr, N. K. (2021). Assessing model performance via the most limiting environmental driver in two differently stressed pine stands. Ecological applications, 31(4), e02312.
- Stavi, I., Yizhaq, H., Szitenberg, A., & Zaady, E. (2021). Patch-scale to hillslope-scale geodiversity alleviates susceptibility of dryland ecosystems to climate change: Insights from the Israeli Negev. Current Opinion in Environmental Sustainability, 50, 129-137.