Regulation and acclimation of leaf gas exchange in a piñon–juniper woodland exposed to three different precipitation regimes

Abstract

Leaf gas-exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas-exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon-juniper Pinus edulis-Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (-45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas-exchange rates under well-watered conditions, leaf-specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade-off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA.Key-words: acclimation; carbon balance; hydraulic limitation; photosynthesis; piñon-juniper woodland; precipitation manipulation; stomatal conductance; water stress.

The Response of Soil CO2 Efflux to Water Limitation Is Not Merely a Climatic Issue: The Role of Substrate Availability

“…In ecosystems facing severe spells of drought, plant assimilation is strictly dependent on water availability [42][43][44][45], whose duration controls the length of the growing season [46][47][48]. In this study, photosynthesis showed a strong seasonal variation, as confirmed by the significant correlation of Anet Table A3. SIR and total El-FAME were both significantly mostly correlated with SR h , with the exception of carbohydrates and amino acids, and fungi and protozoa respectively (Table 4).…”

Prolonged experimental drought reduces plant hydraulic conductance and transpiration and increases mortality in a piñon–juniper woodland

“…), while also maintaining low, but significant canopy gas exchange even as Ψ s and Ψ PD declined down to values of −6 to −7 MPa during drought (Limousin et al. 2013). Predawn water potential ( Ψ PD ) in piñon deviated significantly from soil water potential ( Ψ s ) during periods of drought (Fig 2…”

“…For each species, a single regression relationship was fit across treatments (see Limousin et al. 2013 for details on the gas exchange sampling effort).…”

“…For details on the methodology, sampling periods, and results from the gas exchange sampling, see Limousin et al. (2013). …”

Impact of intra- versus inter-annual snow depth variation on water relations and photosynthesis for two Great Basin Desert shrubs

“…Also, some aspects of these shrubs (e.g., root depth) may have acclimatized over the ca. 50-year history of the snow fences to the effect of snow depth treatments on soil moisture availability (Atkin et al 2000;Limousin et al 2013;Luo et al 2001). These shrubs are deeply rooted and can utilize soil water to 2-to 3-m depth (Caldwell et al 1998;Peek et al 2005;Ryel et al 2004) though our measurements of soil moisture only extended to 100-cm depth.…”