Field measurements of maximum net photosynthesis (Pmax), leaf nitrogen
(N) content (leaf N per area and percent N), and specific leaf area (SLA) were made for
Amazonian tree species within and across early successional sites of known ages after
abandonment from slash-and-burn agriculture. We examined five species across a successional
sere near San Carlos de Rio Negro, Venezuela, to test whether plasticity was associated
with successional status and to determine whether changes in foliar properties
during secondary succession can be attributed to shifts in species composition, in resource
availability, or both. Average leaf N concentration was high (nearly 3%) for a pioneer
species (Cecropiaficifolia) early in succession (1-3 yr after abandonment) but was always
lower for the other early and mid- to-late succession species, especially later in succession
(1-2% at 5-10 yr after abandonment). Net photosynthetic capacity (P /area and P I
mass) varied as much as sixfold, being higher in pioneer species such as Cecropia and
Vismia on recently abandoned sites and lower in late successional species such as Miconia
and Licania on 10-yr abandoned agricultural sites. Total daily light availability also varied
widely (14-fold) from its peak 1 yr after farm abandonment to low levels 9 yr into succession.
During the first 5 yr of secondary succession, there were significant (P < 0.05) differences
in Pmax and leaf N concentration among species in any given year. In most species,
Pmax values declined with increasing time since abandonment within any given site. There
were important differences in photosynthetic plasticity among species: Pmax tended to be
much greater in earlier than later successional species soon after abandonment. Also, the
difference in Pmax among species narrowed (or reversed) over time since abandonment,
largely because of decreasing Pmax in pioneer species. The results suggest that changes in
both species composition and in resource availability combine to produce the common
pattern of decreasing leaf N concentration and photosynthetic rates during early rain forest
succession after agriculture.
Early successional species showed strong (r2 - 0.57, P = 0.0001) mass-based photosynthesis-N
relationships but weak (r2 = 0.40 or lower, P = 0.000 1) area-based relationships
both across the secondary successional sere after agriculture and across sites varying in
types of disturbance. Both mass- and area-based photosynthesis-N relationships were poorer
or not significant (P > 0.05) for mid- to late-successional species. Higher instantaneous
Pmax/N and greater slopes of the photosynthesis-N relationships in early than late successional
species suggest that pioneer species may show greater carbon assimilation capacity
with elevated leaf N concentration on early successional sites than co-occurring species.
The data suggest that early and late successional species may differ in the mode and degree
of leaf-level physiological plasticity across succession.
Ellsworth, D. S., & Reich, P. B.. (1996). Photosynthesis and Leaf Nitrogen in Five Amazonian Tree Species During Early Secondary Succession. Ecology, 77(2), 581–594. http://doi.org/10.2307/2265632
Ellsworth, D.S.; Reich, P.B..
Photosynthesis and Leaf Nitrogen in Five Amazonian Tree Species During Early Secondary Succession.
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