The Olive Tree, Vol. 9 Number 1, 2001

The Summer 2001 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 9 Number 2 , 2001

The Winter 2001 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 8 Number 1, 2000

The Summer 2000 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 8 Number 2, 2000

The Winter 2000 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 7 Number 1, 1999

The Summer 1999 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 7 Number 2, 1999

The Winter 1999 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 6 Number 1, 1998

The Spring 1998 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 5 Number 1, 1997

The Winter 1997 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 4 Number 1, 1996

The Winter 1996 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 3 Number 1, 1995

The Winter/Spring issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

The Olive Tree, Vol. 1 Number 1, 1992

The Summer 1992 issue of The Olive Tree features articles about library projects, collections, technological innovations, and events at Fogler Library, University of Maine.

Modeling tree water deficit from microclimate: an approach to quantifying drought stress

Tree water deficit estimated by measuring water-related changes in stem radius (DeltaW) was compared with tree water deficit estimated from the output of a simple, physiologically reasonable model (DeltaW(E)), with soil water potential (Psi(soil)) and atmospheric vapor pressure deficit (VPD) as inputs. Values of DeltaW were determined by monitoring stem radius changes with dendrometers and detrending the results for growth, We followed changes in DeltaW and DeltaW(E) in Pinus sylvestris L. and Quercus pubescens Willd. over 2 years at a dry site (2001-2002; Salgesch, Wallis) and in Picea abies (L.) Karst. for 1 year at a wet site (1998; Davos, Graubuenden) in the Swiss Alps. The seasonal courses of DeltaW in deciduous species and in conifers at the same site were similar and could be largely explained by variation in DeltaW(E). This finding strongly suggests that DeltaW, despite the known species-specific differences in stomatal response to microclimate, is mainly explained by a combination of atmospheric and soil conditions. Consequently, we concluded that trees are unable to maintain any particular DeltaW. Either Psi(soil) or VPD alone provided poorer estimates of AWthan a model incorporating both factors. As a first approximation of DeltaW(E), Psi(soil) can be weighted so that the negative mean Psi(soil) reaches 65 to 75% of the positive mean daytime VPD over a season (Q. pubescens: similar to65%, P abies: similar to70%, P sylvestris: similar to75%). The differences in DeltaW among species can be partially explained by a different weighting of Psi(soil) against VPD. The DeltaW of P. sylvestris was more dependent on Psi(soil) than that of Q. pubescens, but less than that of P. abies, and was less dependent on VPD than that of P. abies and Q. pubescens. The model worked well for P. abies at the wet site and for Q. pubescens and P. sylvestris at the dry site, and may be useful for estimating water deficit in other tree species.

The dating of dipterocarp tree rings: establishing a record of carbon cycling and climatic change in the tropics

In a first step to obtain a proxy record of past climatic events (including the El Ni (n) over tildeo-Southern Oscillation) in the normally aseasonal tropical environment of Sabah, a radial segment from a recently fallen dipterocarp (Shorea Superba) was radiocarbon dated and subjected to carbon isotope analysis. The high-precision radiocarbon results fell into the ambiguous modern plateau where several calibrated dates can exist for each sample. Dating was achieved by wiggle matching using a Bayesian approach to calibration. Using the defined growth characteristics of Shorea superba, probability density distributions were calculated and improbable dates rejected. It was found that the tree most likely started growing around AD 1660-1685. A total of 173 apparent growth increments were measured and, therefore, it could be determined that the tree formed one ring approximately every two years. Stable carbon isotope values were obtained from resin-extracted wholewood from each ring. Carbon cycling is evident in the `juvenile effect', resulting from the assimilation of respired carbon dioxide and lower light levels below the canopy, and in the `anthropogenic effect' caused by increased industrial activity in the late-nineteenth and twentieth centuries. This study demonstrates that palaeoenvironmental information can be obtained from trees growing in aseasonal environments, where climatic conditions prevent the formation of well-defined annual rings.

Does low phosphorus supply limit seedling establishment and tree growth in groves of ectomycorrhizal trees in a central African rainforest?

In a forest grove at Korup dominated by the ectomycorrhizal species Microberlinia bisulcata, an experiment tested whether phosphorus (P) was a limiting nutrient. P-fertilization of seven subplots 1995-97 was compared with seven controls. It led to large increases in soil P concentrations. Trees were measured in 1995 and 2000. M. bisulcata and four other species were transplanted into the treatments, and a wild cohort of M. bisulcata seedlings was followed in both. Leaf litter fall from trees and seedlings were analysed for nutrients. Growth of trees was not affected by added P. Transplanted seedlings survived better in the controls than added-P subplots: they did not grow better with added-P.M. bisulcata wildlings survived slightly better in the added-P subplots in yr 1 but not later. Litter fall and transplanted survivors had much higher concentrations of P (not N) in the added-P than control subplots. Under current conditions, it appears that P does not limit growth of trees or hinder seedling establishment, especially of M. bisculcata, in these low-P grove soils.