Phenology of fine roots and shoots using high frequency temporal resolution images in a temperate larch forest

Purpose Understanding tree phenology reveals the underlying mechanisms through plant functional and productive activities and carbon sinks in forest ecosystems. However, previous research on tree phenology has focused on shoot dynamics rather than tree root dynamics. We aimed to explore seasonal temperature patterns of daily-based root and shoot dynamics by capturing high frequency plant images in a larch forest. Methods We monitored continuous images using an automated digital camera for shoot dynamics and a flatbed scanner for the fine root dynamics in the larch. Using the images, we analyzed the relationship between temperature and plant area index as shoot growth status and total root-area proportion of white and brown roots. Results Larch shoot production had a single mountain-shaped peak with a positive correlation between plant area index and air temperature. Fine root production had two peaks in the bimodal root-growth pattern in early summer and late autumn. Soil temperature was positively correlated with white root proportion and negatively correlated with brown root proportion. Conclusion We found differences between shoots and roots regarding temperature relationships. In particular, the automated flatbed scanner method for the root dynamics allowed the collection of detailed bimodal patterns of root production with shift from whitening to browning color, which had been previously overlooked. Such high frequency temporal resolution analysis can provide an in-depth of mechanisms of fine-root and shoot phenology through different stages of plant development in terms of growth and senescence.

Coppice shoot dynamics in a tropical dry forest after human disturbance

Coppicing is an important regeneration mechanism in tropical dry forest after disturbance, but little is known about the long-term dynamics and the rate of recovery of the coppice shoots following clearance. This study reports on the growth and dynamics of coppice shoots following experimental cutting in a tropical dry forest in Jamaica. The fate of coppice shoots was tracked on a total of 481 stumps, representing 51 species over 10 y. The number of coppice shoots and the height and dbh of the leading shoots were measured on the tree stumps 14 mo and 10 y after cutting. Coppicing was vigorous for most tree species, but the average number of shoots per stump decreased significantly over the 9 y period, from 25 to 8 shoots per stump. The average height and diameter of the leading shoots after 10 y were 4.5 m and 3.8 cm, respectively, and the average percentage diameter recovered by the shoots varied between 36% and 95% among the species. Coppicing facilitates the long-term persistence of this dry forest, and the rapid growth of coppice shoots contributed to the resilience of most species after cutting.

Root dynamics in sprouting tanoak forests of southwestern Oregon

Root and shoot biomass were measured across an 8 year chronosequence in mature and regenerating stands of tanoak ( Lithocarpus densiflorus (Hook. & Arn.) Rehd.), following cutting and burning in mature tanoak forests. Tanoak stump sprouts rapidly replaced leaf biomass but did not maintain preexisting root systems. Rather, root biomass declined for several years, with the largest proportional decline in extra-fine roots. Four years after harvest, live root biomasses in diameter classes 0.25–2.00 and 0.25–5.00 mm were 25% and 30% of values in mature tanoak forests, respectively. The proportion of dead roots was strongly correlated with maximum summer soil temperature. Root/shoot ratios recovered to preharvest values by age 3–4 years, at which time the live biomass of fine roots and leaf biomass was approximately 30%–40% of values in mature forest. From age 4 to 8 years, stable root/shoot ratios were associated with a three- to four-fold reduction in growth rate of leaf biomass and a proportional increase in growth of fine roots. These findings support the general theory of a functional root–shoot balance in tanoak and suggest a possible role for soil temperature in postharvest root dynamics. Improved understanding of postdisturbance root and shoot dynamics in tanoak will help identify competitive interactions and priorities for vegetation management decisions in establishment of conifers following harvest of mixed conifer–hardwood forests of southwestern Oregon and northern California.