Climate Response of Growth and Water Use in Semi-Arid Pine Forest
Investigators (most current known information)
Proposal Abstract
Introduction
This report provides a summary on the two main components of the project: 1) The tree ring analysis of samples collected in the joint field campaign of the 1st year and 2) The ecopshysiolgical measurements from the seasonal campaigns. These activities follow the original objectives and plan of operation. The first manuscript based on work in the framework of this research project has now been published in Oecologia, a second one is in advanced stage of preparation, and others are planned. All the main results and the tree rings raw data are reported here.
Original objectives
- To correlate climatic conditions with the inter- and intra-annual variations in stem growth and stand level water use efficiency of trees growing along a climate gradient in Israel.
- To examine the quantitative relationships between tree ring parameters and leaf and canopy scale gas exchange parameters at the Yatir forest site. In particular the following hypotheses will be tested: a) Intrinsic water use efficiency estimated from tree ring δ13C is directly comparable to instantaneous water use efficiency estimates from leaf and flux tower gas exchange measurements and b) Tree ring δ13C is a faithful recorder of average leaf net CO2 exchange, which may, under specific conditions, be used to indicate net ecosystem CO2 flux.
Conclusions
Based on the results reported here, we concluded: 1) Soil water status was a dominant, but not sole, limiting factor on growth, leaf gas exchange and δ13C of Aleppo pine in the semi‑arid Yatir forest, Israel, both on seasonal and annual time‑scales; 2) While other factors, such as VPD, temperature, radiation loads and the plants hydraulic conductivity, are likely to play important roles too, the large enhancement in growth by the irrigation treatment indicated that nutrient availability was not a major limitation, at least at the short term; 3) As expected, irrigation enhanced A and gs and resulted in increases in BAI and needle length, and decreases in δ13Cgx, δ13Cn and δ13Ct but did not change phenological patterns; 4) A close association between average, assimilation‑weighted δ13Cgx and δ13Cn and δ13Ct clearly support the application of 13C in both tree rings and needles as a time integrated proxy of ecophysiological plant response to environmental conditions during assimilation, on both inter‑annual and seasonal time‑scales; 5) Although stored photosynthates influenced growth and δ13Cn and δ13Ct values over time, this may be mostly buffering fluctuations in C supply, as it did not significantly affect the dynamic and robust links between δ13Cgx and δ13Cn and δ13Ct values, and 6) These links also clearly indicated that the growth, which continued during the stressful dry season at the study site, was mainly incorporating concurrently assimilated carbon, rather than stored carbon from the high activity wet season.
Outcome
Articles
Tamir K., D. Hemming, T. Lin, J.M. Grünzweig, K. Maseyk, E. Rotenberg, and D. Yakir. 2005. “Association between tree-ring and needle δ13C and leaf gas exchange in Pinus halepensis under semi-arid conditions.” Oecologia 144(1):45-54.
Scartazza. A, C. Mata, G. Matteucci, D. Yakir, S. Moscatello, and E. Brugnoli. 2004. “Comparisons of δ13C of photosynthetic products and ecosystem respiratory CO2 and their responses to seasonal climate variability.” Oecologia 140(2):344-351.