A functional comparison of productivity in even-aged and multiaged stands: A synthesis for Pinus ponderosa

The relative productivity of even-aged and uneven-aged or multiaged stands is a frequently debated topic in silviculture and forestry. Nearly all previous comparisons have been empirical growth studies, simulations of stand growth, or economic analyses based on differences in stem volume production. Both even-aged and multiaged systems are highly variable and the large number of variables and assumptions makes any comparisons difficult. In this review, a series of studies in ponderosa pine are synthesized to develop a more functional understanding of the relative stemwood productivity of these variable stand structures. Multiaged ponderosa pine stands were either as efficient or slightly more efficient at converting light energy to volume growth than even-aged stands. Even-aged stands appear to experience a higher level of mid-summer water stress than multiaged stands. This finding suggests reduced photosynthesis in even-aged stands and a possible cause for a slightly lower level of productivity in even-aged stands. However, differences in productivity are likely insignificant in comparison to the wide variations in even-aged and multiaged structures and differences caused by the operations necessary to maintain these structures. As ponderosa pine systems are primarily water-limited, these results may not apply to more light-limited systems.