Values and Services of Nitrogen-Fixing Alder Based Cardamom Agroforestry Systems in the Eastern Himalayas - Smallholder Tree Growing for Rural Development and Environmental Services - page 382

Himalayas, which is comparable to the mixed tree species forest-cardamom ECE
value of 1.19 percent. The ECE contribution of large cardamom was much greater in
the alder-cardamom system (0.85 percent) than the forest-cardamom system (0.36
percent). The Energy Fixation Efficiency (EFE) is the annual net energy fixation per
unit energy of leaf, and the Energy Accumulation Ratio (EAR) is calculated as the
energy stored in the system divided by annual net energy fixation (Sharma et al.
2002). The EFE and EAR of the alder-cardamom system were slightly lower than that
of the forest-cardamom system. The alder-cardamom system showed lower EAR,
resulting from less energy accumulation in the perennial components of alder trees
and also a greater annual turnover in the form of leaf and twigs of tree and cardamom
components. This reveals that there are higher energy dynamics in the alder-carda-
mom system compared to its forest-cardamom counterpart. The EFE may be expected
to decrease with increasing rates of fixation because the availability of other resources
(such as water or nutrients) may become limited and will constrain production. The
EFE in the alder-cardamom based agroforestry systems was generally consistent with
this hypothesis: it decreased - and was lower compared to the forest cardamom sys-
tem - due to the influence of N 2 -fixing alder trees (3.29 GJ GJ −1 leaf energy year −1 in
alder-cardamom and 3.70 GJ GJ −1 leaf energy year −1 in forest-cardamom). Yet, the
EFE contribution of large cardamom was greater in the alder-cardamom system (3.20
GJ GJ −1 leaf energy year −1 ) than in the forest-cardamom (3.07 GJ GJ −1 leaf energy
year −1 ) system. Energy efficiency in N 2 -fixation decreased with plantation age, rang-
ing between 58-103 g N 2 fixed 10 4 kJ −1 energy in the pure age series of alder stands
(Sharma and Ambasht 1991), which is comparable to 68 g N 2 fixed 10 4 kJ −1 energy in
the alder-cardamom system.
The results of the alder-cardamom system's age series showed that annual net
energy fixation was highest (444 × 10 6 kJ ha −1 year −1 ) in the 15-year-old stand,
being 1.4 times the 5-year-old stand and 2.9 times the 40-year-old stand fixation
(Sharma et al. 2002a). Regression analyses suggest that younger plantations are
more productive for both cardamom and alder, with inverse relationships between
stand age and production efficiency, energy conversion efficiency or energy utilized
in nitrogen fixation, and a positive relationship between production efficiency and
energy conversion efficiency. The energy dynamics also support the earlier finding
concerning the alder-cardamom system's sustainability by adopting a 15 to 20 years
rotational cycle.
Cultivation of cardamom is a relatively low input cash crop. The main require-
ments are labour and firewood for curing the cardamom capsules. The outputs
include agronomic yield, fodder and firewood from trees. The quantum of energy
input and output for the alder-cardamom system was about twice the quantum for
the forest-cardamom system (Table 18.2). The ratio of output to input produced
lower values for the alder-cardamom system. However the cash income from this
system was more than double the cash income from the forest-cardamom system,
and also the cost-benefit analysis gave better results for the former alder-cardamom
system. Both the quanta of energy and higher cash return for the alder-cardamom
agroforestry system support the idea that the integration of alder trees in cardamom
plantations is an efficient management system.