Effects of environmental changes on the vitality of forest stands

Abstract

Using the physiological single tree growth model BALANCE, vitality of forest stands was simulated in dependence of the site-related factors, climate and stand structure. At six level II plots in southern Germany with the main tree species beech (Fagus sylvatica L.), oak (Quercus robur L.), spruce (Picea abies [L.] Karst.), and pine (Pinus sylvestris L.), simulated results were compared to measured values (soil water content, bud burst and leaf colouring, diameter at breast height, tree height and crown density) in order to validate the model. Sensitivity tests were done to examine the influence and the interactions of the environmental parameters. The validation results show that BALANCE is capable of realistically simulating the growth and vitality of forest stands for central European regions for medium term time spans (several years). The validation of the water balance module produces mean absolute errors based on field capacity between 2.7 and 6.9% in dependence of sites and forest stands. Senescence of foliage as well as crown density is reproduced with a correlation coefficient of 0.70 compared to measurements. Differences between measured and simulated diameter values were smaller than 1% for spruce and smaller than 6.5% for beech after 7 years of simulation, and smaller than 1% for oak after 8 years of simulation. On the other hand, the simulations for pine trees conform less with the measurements (difference: 22.6% after 8 years). The sensitivity of the model on environmental changes and on combinations of these parameters could be demonstrated. The responses of the forest stands were quite different.

Simulating stand climate, phenology, and photosynthesis of a forest stand with a process-based growth model

“…Our values are somewhat higher because spruce as well as beech has relatively high lai values. Also, we have excluded the Table 5 Means of measured and modeled rates of photosynthesis (g C m −2 ) of two beech trees and one spruce tree in sun-exposed and shaded crown parts Comparing former water balance validation results of BALANCE (Grote et al 2003;Rötzer et al 2005), where modeled soil water contents were opposed to measured data, and the means over 20 months from this study with the literature results of other (water balance) models (e.g., Wegehenkel and Jochheim 2003;Gusev and Nasova 2003;Rötzer et al 2004b), the water balance of forest stands could be described reasonably well by the model BALANCE.…”

“…A more detailed description of BALANCE can be obtained in Grote and Pretzsch (2002), Rötzer et al (2005Rötzer et al ( , 2009.…”

“…Others that consider dimensional changes on an average tree basis are, e.g., FORGRO (Mohren et al 1993; Mohren and van de Veen 1995) and TREEDYN3 (Bossel 1996). Models which simulate tree classes or even individual trees explicitly are Tree-BGC (Korol et al 1995), LIGNUM (Perttunen et al 1996;Lo et al 2001), and BALANCE (Grote and Pretzsch 2002;Rötzer et al 2005), which is used for this study.…”

Extending a physiological forest growth model by an observation-based tree competition module improves spatial representation of diameter growth

“…Langvall and Löfvenius 2002) to estimate how the impact of long-term changes might be mitigated or best capitalized (Goreaud et al 2006). In individual tree, physiological models such as BALANCE (Grote and Pretzsch 2002;Rötzer et al 2005) modellers have merged available theory about the underlying processes of growth into mechanistic aggregates of soil and vegetation modules that take into account individual tree position, dimension and vertical crown stratification. In contrast to the typical process model which is mechanistic and detailed for processes that are relevant to a selected focus (as reviewed by Mäkelä et al 2000), such as carbon fixation, the ecopyhsiological individual tree model is designed to estimate the distribution of tree dimensional growth with a very high generality.…”

Acclimatation of three co-occurring tree species to water stress and their role as site indicators in mixed pine-oak forests in the Sierra Madre Oriental, Mexico

“…The response of forests to these changes is uncertain and has the potential to greatly alter the distribution and productivity of tree species (Pastor and Post 1988;Kramer 1983;Tschaplinski et al 1998;Rötzer et al 2005;Ricker et al 2007). Inappropriate land-use contributes further to the acceleration of forest degradation and deforestation in great parts of the mountain chain Sierra Madre Oriental due to anthropogenic pressures (Domínguez and Návar 2000;Cantú and González 2002;González Tagle et al 2005).…”