photoperiod on spring phenophases such as leaf emergence is still being examined
by phenologists (Chuine 2010). In temperate and boreal regions, the photoperiod
coregulated leaf emergence with temperature (Fu et al. 2015).
Opler et al. (1976) stated that photoperiod and thermal accumulation seem
insufficient to demonstrate the break of dormancy and the resulting synchronised
flowering that is characteristic of many tropical trees, lianas, and shrubs, although
short-day photoperiods are probably a major part of initial induction of the reproductive system.
A study to examine bud responses to photoperiod in adult trees growing outside
revealed that dormancy break is controlled at the bud level, with light sensing (and
probably also temperature sensing) occurring inside the buds. Leaf primordia only
react to photoperiod during the late phase of dormancy break when warm days begin
(Zohner and Renner 2015).
In another study it was investigated that longer chilling duration resulted in earlier
bud burst and maximum bud burst occurred in less thermal time. Consequently,
insufficient chilling is received during warmer winters, so bud burst in spring may be
expected to be delayed. However, the photoperiod effect was found to be weaker for
longer chilling durations; longer photoperiod may, at least in part, compensate for
shorter chilling duration (Pletsers et al. 2015). After comparing other causes of
change for phenology, more evidence of plants comes from changes observed in
the spring (Rosenzweig et al. 2008).
Precipitation
Precipitation and soil water potential are other very important regulating factors in
plant phenology. Sufficient nutrient availability during the growing season enhances
plant tolerance and adaption to freezing stress, which thereby postpones autumn
phenological events. Phenology in the tropical forest, which has more complex
biodiversity than temperate and boreal regions, is majorly governed by precipitation
patterns compared to temperature variability (Pau et al. 2011). Precipitation is crucial
in leaf phenology in the tropical forest, compared to other abiotic elements, because
the tropical climate is more regulated by rainfall-related events (Reich 1995). It was
found that the extent of influence in phenological events by water and nutrient
availability is less in temperate and boreal forests as compared to temperature and
photoperiod (Jaworski and Hilzczanski 2013). In arid and semiarid regions, seasonal
moisture may have a primary or synergetic function in vegetative and reproductive
activity in plants (Beatley 1974; Kemp 1983).
In semiarid regions of California, Mazer et al. (2015) found that, in the
phenophases of some species, precipitation had a central role in prognosticating
the emergence of leaf phenology or flowering. This study also revealed a monthly
synergetic relationship between temperature and precipitation that affected the onset
of phenological transitions. The extent of stress experienced by tropical dry forests
varies largely during the dry months in these areas as drought conditions are
8 Forest Phenology as an Indicator of Climate Change: Impact and Mitigation. . .
193
by phenologists (Chuine 2010). In temperate and boreal regions, the photoperiod
coregulated leaf emergence with temperature (Fu et al. 2015).
Opler et al. (1976) stated that photoperiod and thermal accumulation seem
insufficient to demonstrate the break of dormancy and the resulting synchronised
flowering that is characteristic of many tropical trees, lianas, and shrubs, although
short-day photoperiods are probably a major part of initial induction of the reproductive system.
A study to examine bud responses to photoperiod in adult trees growing outside
revealed that dormancy break is controlled at the bud level, with light sensing (and
probably also temperature sensing) occurring inside the buds. Leaf primordia only
react to photoperiod during the late phase of dormancy break when warm days begin
(Zohner and Renner 2015).
In another study it was investigated that longer chilling duration resulted in earlier
bud burst and maximum bud burst occurred in less thermal time. Consequently,
insufficient chilling is received during warmer winters, so bud burst in spring may be
expected to be delayed. However, the photoperiod effect was found to be weaker for
longer chilling durations; longer photoperiod may, at least in part, compensate for
shorter chilling duration (Pletsers et al. 2015). After comparing other causes of
change for phenology, more evidence of plants comes from changes observed in
the spring (Rosenzweig et al. 2008).
Precipitation
Precipitation and soil water potential are other very important regulating factors in
plant phenology. Sufficient nutrient availability during the growing season enhances
plant tolerance and adaption to freezing stress, which thereby postpones autumn
phenological events. Phenology in the tropical forest, which has more complex
biodiversity than temperate and boreal regions, is majorly governed by precipitation
patterns compared to temperature variability (Pau et al. 2011). Precipitation is crucial
in leaf phenology in the tropical forest, compared to other abiotic elements, because
the tropical climate is more regulated by rainfall-related events (Reich 1995). It was
found that the extent of influence in phenological events by water and nutrient
availability is less in temperate and boreal forests as compared to temperature and
photoperiod (Jaworski and Hilzczanski 2013). In arid and semiarid regions, seasonal
moisture may have a primary or synergetic function in vegetative and reproductive
activity in plants (Beatley 1974; Kemp 1983).
In semiarid regions of California, Mazer et al. (2015) found that, in the
phenophases of some species, precipitation had a central role in prognosticating
the emergence of leaf phenology or flowering. This study also revealed a monthly
synergetic relationship between temperature and precipitation that affected the onset
of phenological transitions. The extent of stress experienced by tropical dry forests
varies largely during the dry months in these areas as drought conditions are
8 Forest Phenology as an Indicator of Climate Change: Impact and Mitigation. . .
193