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 386

Table 18.3 General bird characteristics in three gradient forests with and without cardamom
in Sikkim (Nakul Chettri, unpublished)
Bird variables Alder- Forest- Natural forest

cardamom cardamom without cardamom

Species recorded 48 40 50

Species per sample (mean + SE) 5.9 ± 0.2 7.0 ± 0.5 5.1 ± 0.5

Individual per sample (mean + SE) 23.6 ± 1.7 28.3 ± 3.6 24.4 ± 2.7

Shannon Weiner's diversity (H') 2.9 3.1 3.4

Margalef's species richness 12.2 10.6 12.6

This enhances the richness of tree species in a cardamom dominated system. Trees
from cardamom agroforestry have multiple uses for farmers, such as fodder, fire-
wood, timber, materials for field implements and residues for animal bedding. These
trees also support birds and other wildlife, which has a direct bearing on the ecosys-
tem structure and enables it to function in a sustained manner.
A study of bird characteristics was carried out in three gradient forests in the
Khecheopalri and Yuksam areas of west Sikkim: (1) a natural forest without carda-
mom, (2) a forest with cardamom and (3) an alder forest plantation with cardamom.
The general characteristics of the bird community revealed that an alder-cardamom
field is an equally good habitat for biodiversity as natural and mixed forests
(Table 18.3). A greater richness of bird species and diversity was observed in the natural
forest without cardamom, and the species richness in the alder-cardamom stand was
also greater than in the mixed forests with cardamom. There were no significant dif-
ferences in the variables of these three gradient forests. Interestingly, a higher number
of species per sample was observed in the alder-cardamom field where insectivores
(flycatchers, laughing-thrushes, woodpeckers) and omnivores (drongos, crows, mynas)
were the dominant bird species. In a promising surrogate, the pattern of species richness,
diversity and the guilds of birds are indicative of the habitat's quality (Anand et al. 2005;
Fleishman et al. 2005; Padoa-Schiopa et al. 2006). Since most of the alder-cardamom
fields in Sikkim are contiguous to the natural forest, they have a dual function being a
feeding habitat on the one hand, and leading to a well developed habitat mosaic which
enhances overall biodiversity on the other hand (Chettri et al. 2005). Our results
revealed that alder-cardamom is equally good for forest birds, particularly insectivores
and omnivores. Also, the high species richness compared to the mixed forest is mainly
due to the openness of the upper strata that creates visibility for feeding species. If age
groups of alders are maintained so as to enhance different succession stages, then
diversity might also be enhanced as reported by Shankar Raman et al. (1998).

18.3.5 Soil and Water Conservation

The overland flow (percentage of rainfall during the rainy season) as estimated in
temperate and subtropical forests, cardamom agroforestry, mandarin agroforestry,