2.1 Tree improvement

         Ninety-five
saplings of Gmelina arborea collected
from 19 seed sources were plantain June, 2001. These were collected from six
different sites viz. 4 from Goalpara, 3 from Dudhnoi, 3 from Damara,4 from
Boko,2 from Byrnihat and 3 from Silchar.

         Seed
source from Byrnihat (AAU 15 & AAU 16) registered 28.98 & 26.89m and
Silchar (AAU 17 & AAU 18) registered 25.86 & 27.67 m tree height
respectively, in 20 yrs old plantation

         AAU
15, AAU 16, AAU 17 & AAU 18 registered dbh of 45.36, 44.85, 49.99 and 51.48
cm respectively, in 20 years;

         AAU
18 (Silchar), recorded the highest timber volume of 3.253 m3/tree, biomass of
1789.47 Mg/ha and above ground C stock of 878.15 Mg/ha.

         The
mean height, dbh, timber volume and biomass of 19 sources are presented in Tables5.1, 5.2, 5.3 and 5.4.

2.2
Agroforestry system

2.2.1 Acacia mangium based AF system

Ø   
The maximum plant height (17.57 m), dbh (36.21 cm),
timber volume (472.25 m³/ha), tree biomass (505.13Mg/ha) and above
ground carbon stock (252.56 Mg/ha) was recorded in intercrop plot where tree
spaced at 5 m x 4 m.

Ø   
The maximum fodder yield of Hybrid napier (52.16
t/ha) was obtained in sole fodder followed by tree spaced at 5 m x 6 m (46.78
t/ha), 5 m x 5 m (40.78 t/ha) and 5 m x 4 m (39.81t/ha), respectively.

Ø   
The highest increase in OM %, available N in kg/ha,
P₂O₅ in kg/ha & K₂O in kg/ha of 37.76 %,
29.10 %, 30.35 % & 14.71 % respectively over the initial year were recorded
in the intercrop plot of tree& fodder where trees spaced at 5m x 4 m.

2.2.2     
Acacia mangium for timber

Ø   
The average of 73 superior trees attained 26.8m plant height and 42.0 cm
dbh, 9.82m canopy diameter, and 442.14 m3^3/ha timber volume in 21^st
year.

Ø   
Timber volume and tree biomass of the standing tree were 440.6 m3/ha and
500.2 Mg/ha respectively.

Ø   
Above ground C stock observed was 248.16 Mg/ha.

Ø   
Here increase in OM %, available N in kg/ha, P₂O₅
in kg/ha & K₂O in kg/ha of 6.52 %, 32.98 %, 8.62 % 14.78 %
respectively over the initial year.

2.2.3 Jackfruit-based AF
system

Ø   
Tree height of 8.98 m was recorded in the intercrop plot whereas it was
8.62 m in tree without crop. The dbh (31.82 cm) of jackfruit was superior in
the intercrop plot in comparisen to sole tree plot (30.28 cm). Timber volume,
tree biomass and above ground C stock for jackfruit was higher in inter-crop
plots, being 61.24 m3/ha, 106.18 Mg/ha, and5and 53.28 Mg respectively. However,
canopy diameter (8.56 m) was higher in sole jackfruit.

Ø   
Fruit yield of jackfruit was not increase in 18 years of plantation on.

Ø   
In this agroforestry system increase in OM%, available N in kg/ha, P₂O₅
in kg/ha & K₂Oin kg/ha of 45.24 %, 26.94 %, 25.8 % & 14.54 %
respectively over the initial year were recorded.

2.2.4 Gmelina arborea based Agrisilvicultural
system

Ø   
In nearly 6th year plantation maximum tree ht. (7.14 m) collar girth
(32.08 cm) were observed insole tree plot and Cowpea-Toria sequence as
intercrops respectively.

Ø   
Max canopy diameter (2.98 m) was found in GG-Toria sequence as intercrop.

Ø   
Max annual increment of tree height (465%), collar girth (382%) and
canopy diameter (264%) recorded in GG-Toria sequence as intercrop.

Ø   
No remarkable yield reduction of intercrops observed upto 6^th of
plantation.

Ø   
The highest increase in OM %, available N in kg/ha, P₂O₅
in kg/ha & K₂O in kg/ha of16.92%, 9.86%, 21.86% & 8.82 %
respectively over the initial year were recorded in the intercrop plot of
tree& GG -Toria sequence.

2.3      
Growth pattern of Melocanna
baccifera

Ø    Muli bamboo attained 13.12 m
in height and1478 cm in girth in 21 years.

Ø    The mean yield of matured
bamboo and B:C ratio were 322620 no./ha and 3.46,  respectively.

2.4      
Growth pattern of Bambusa balcooa.

Ø   
Mean plant height (25.59 m), spread (5.67 m), new culm (23.52 no.), total
culms (149.31 nos.), canopy diameter (15.79 m), biomass (193.67 Mg/ha) and
harvestable yield (1297.69 no./ha) of Bambusa
balcooa was recorded in 14years after plantation.

Ø   
In the case of Bambusa balcooa, increase in OM%, available N in kg/ha, P₂O₅
in kg/ha & K₂Oin kg/ha of 48.80 %, 16.43 %, 13.86 % & 8.88 %
respectively over the initial year were recorded.

2.5      
Growth pattern of Bambusa tulda

Ø   
Mean plant height (18.73 m), spread (3.97 m), new culm (33.53 no.), total
culms (117.97 nos.), canopy diameter (11.73 m), biomass (229.37 Mg/ha) and
harvestable yield (2354.59 no./ha) was observed in Bambusa tulda in 14 years after plantation.

Ø   
In case of Bambusa tulda,
increase in OM%, available N in kg/ha, P₂O₅ in kg/ha
& K₂O in kg/ha of 42.06 %, 17.36 %, 13.14 % & 6.92 %
respectively over the initial year were recorded.