L. Lindkvist et D. Chen, Air and soil frost indices in relation to plant mortality in elevated clear-felled terrain in Central Sweden, CLIMATE RES, 12(1), 1999, pp. 65-75
This study investigates the occurrence of low summer night temperatures in
relation to plant mortality in a confined clear-felled area. The work was c
arried out in highly complex and elevated mountainous terrain in central Sw
eden. Indices for air and soil frost were developed to identify the relatio
nship between low temperatures and plant mortality during the peak of the g
rowing season. The indices are based on air temperature measurements at 29
stations and soil temperature measurements for 2 depths at 4 stations. The
terrain was classified according to its curvature at each sampling site. Fo
ur main terrain types and 2 subtypes were identified, which allowed for an
analysis that links the air frost index to a specific terrain feature. An i
nventory of plant mortality was carried out in circular areas of 500 m(2) w
hich were centred around the sampling sites. It was found that terrain curv
ature and aspect in relation to solar azimuth angle around sunrise and suns
et have a significant impact on the frequency of low night temperatures in
summer. This was also reflected by the distribution differences of survivin
g plants between various terrain types. The air frost index was highly corr
elated to the mortality (r = 0.91, N = 29). However, an analysis of the res
idual in the regression indicates that other factors are also important. Th
e soil frost index helps explain the relatively high mortality in convex te
rrain. Also, the influence of temperature-induced frost hardening on the mo
rtality during the vegetative period is discussed.