Agriculture Reference
In-Depth Information
in both upstream and downstream areas with various vital ecosystem services.
Based on the Millennium Ecosystem Assessment (MA 2005), the ecosystem
services arising from alder-cardamom agroforestry system can be classified into
four categories:
(a) Supporting services which are evident from the system's positive impact on
productivity, nutrient cycling, nitrogen fixation, energy fixation and nutrient use
efficiency
(b) Provisioning services which are evident from the system's yields of cardamom,
firewood, fodder and other products
(c) Regulating services which are evident from the system's contribution to soil
and water conservation, soil fertility, carbon storage and flows, and a favourable
microclimate
(d) Cultural services which are evident from the system's aesthetic, educational and
recreational benefits
In the sections below, the various ecosystem services associated with alder-cardamom
cultivation in the Eastern Himalayas will be discussed based on the authors' extensive
research experience in the region. Furthermore, the efficiency in delivering these
services will be described and compared for agroforestry systems with and without
N
2
-fixing alder, and also for systems with stands of different age.
18.3.1
Productivity, Yield and Energy Efficiencies
The performance of alder-cardamom systems was much higher in terms of produc-
tivity and agronomic yield, compared to the forest-cardamom systems (Table 18.1).
Alder actually influenced the system by its fast growth which contributes to higher
total biomass, and also by enhancing cardamom performance as illustrated by
greater tiller numbers, basal area and biomass (Sharma et al. 1994). The agronomic
yield of cardamom increased 2.2 times under the alder canopy. Similarly, the com-
parative study on the impact of standing age (5, 10, 15, 20, 30 and 40 years) on the
cardamom crop and the alder trees associated revealed that net primary productivity
was the highest (22 t ha
−1
year
−1
) in the 15-year-old stand and the lowest (7 t ha
−1
year
−1
) in the 40-year-old stand (Sharma et al. 2002a). Agronomic yield of carda-
mom peaked between 15 and 20 years of age. Cardamom productivity doubled
between the 5 to 15-year-old stand and then decreased with plantation age. It reached
a minimum in the 40-year-old stand. The performance of cardamom in association
with alder remained ecologically and economically beneficial until the plantation
was 20 years old. This suggests that the re-plantation cycle should begin around
this age for sustainable management practice. Cardamom being a shade-tolerant plant
does not perform well when the canopy opens, as observed after 30 years of age.
Ageing could also play a role in the decreasing performance of both the crop and
the associated alder.
Studies of energy distribution and flow rates determined for various components
of the alder-cardamom and forest-cardamom agroforestry systems highlighted that
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