| dc.description.abstract | Papyrus growth dynamics, culm density, standing
biomass, primary productivity and prevailing environmental
variables (light, temperature and nutrients)
were investigated in Lake Naivasha papyrus swamp. The
effect of the above environmental variables on growth
of papyrus was investigated under controlled environment.
Under natural conditions papyrus mean culm
biomass at maturity was 257 ± 149 g while maximum
relative growth rate was estimated to be 0.221 ± 0.097
-1 '-1 g g week . Mean culm density was estimated to be
-2 _~'=c _
13.1 ± 1.9 m . Harvesting papyrus stimulated growth
resulting ln an increas~ in culm density which reached
- 2 ",
a peak of 19.0 m after six months of re-growth.
Papyrus aboveground an'd,belowground biomass was
estimated to b~ 3602 and 1040 g,m -2 respectively.
During the re-growth of papyrus in the harvested
stan ds, the cei1ing y ie1d (274l-g J!l - 2) was at tained
after 6 months. Aboveground net primary productivity
was 14.1 g m-2 day-l while the oelowground
productivity was estimated to be 4.0 g m-2
net primary
-1
day
Aboveground net primary productivity in the harvested
stands reached a peak of 21.0g m-2 day-l after four
months of re-growth. The annual production of papyrus
in Lake Naivasha swamp was estimated to be 6607 g m -2
yr -1
Levels of total solar radiation above the papyrus
canopy rang ed from 10.6 to 25. 2 ·~U. m-2 day -1 wi th
-2 -1 a mean of 18.2 MJ m day . Instantaneous values of
solar radiation received by papyrus canopy for most
of the day (9h -_lSh) ranged from 400-960 W m-2
The range of temperature in various positions of
papyrus canopy was recorded to be 7.2 - 33.3 °c in air
above papyrus canopy, 7.5 - 28.0 °c in air at midcanopy,
8.0 - 24.5 °c in papyrus cu1ms and 14.7 -
18.6 °c in swamp sediments.
Determination of inorganic nitrogen ln swamp
water showed levels of ammonium nitrogen, nitrite
nitrogen and nitrate nitrogen were 296 ± 95, 1.1 ± 0.4,
-1
and 6.4 ± 3.0 ~g ~ . Dissolved nitrogen had a mean
concentration of 1~29 ± 0.14 mg 1-1 while particulate
nitrogen.concent!atioD was 0.91 ± 0.38 mg 1-1. Total
mean concentration of nitrogen in swamp water was
- ~1
2.51 ± 0.30 mg 1
The mean concentration otorthophosphate in
swamp water was 24.0 ± 12.0 ~g )-1. Dissolved and
particulate phosphorus had mea~:concentrations of
-1
76.8 ± 19.5 and 76.5 ± 47.8 ~g 1 respectively
while total phosphorus concentration was 153.3 ± 63.3
~g -1 1 .
The mean concentrations of dlssolved and
particulate sulphur were 105 ± 57 and 151 ± 51 ~g 1-1
respectively. Total sulphur had a mean concentration
-1
of 256 ± 82 u g 1
Of the three nutrients analysed in swamp
sediments, nitrogen had the highest level of 1.97 ±
0.460%. Sulphur and phospho~us content of swamp
sediments were 0.196 ± 0.049% and 0.104 ± 0.009%
respectively.
In the nutrient analysis of papyrus tissue,
highest level of nitrogen (1.97 ± 0.44%) was found
in the umbel while nitrogen levels in papyrus roots,
rhizomeS"culms and scale leaves were 1.37 ± 0.13%,
1.37 ± 0.33%, 0.72 ± 0.17% and 0.50 ± 0.12%
respectively. Phosphorus had the highest levels In
rh izornes (0 .31 ± O.0 7%J Wh i1e the urnbel s, cu1ms ,
scale leaves and roots had phosphorus content of
0~24 ± 0.07%, 0.~4 ± 0.06%, 0.11 ± 0.04% and
0.09 ± 0.03% respectively. Highest levels of sulphur :. -
(0.14 ±, 0.07%) occurred in the rhizomes while sulphur
content of the-umbels, roots, culms and scale leaves
was estimated to be 0.09 ± 0.02%, 0.08 ± 0.02%,
0.06 ± 0.03% and 0.06 ± 0.03%-respectively. Nutrient
content of papyrus tissue was:iound to decrease with
increasing ~ge of the plant.
Nutrition studies showed ~hat an increase in
nitrogen content of papyrus leaves from a low level
of 11.8 to a high level of 36.6 mg g-1 increased growth
parameters as follows: photosynthetic rates from
O .010 ± 0.078 to 0.752 ± 0.154 mg CO - 2 -1 2.m s
xx -
chlorophyll content from 162 ± 90 to 687
total leaf area from 11.0 ± 4.0 to 251,2
~2
± 86 mg m
2
± 80,0 em ,
total leaf biomass from 0.020 ± 0.019 to 0.720 ± 0.170
g, plant biomass from 0.125 ± 0.045 to 2.96 ± 1.36 g
and leaf extension rate from 2.75 ± 1.26 to 32.9 ± 3.
-1
64 mm day • Root/shoot ratio, however, decreased from
,,12 ± 1. tc 0.14 ± 0.03. Like nitrogen, an increaso
in phosphorus content of papyrus leaves from a low
level of 0.56 to a high level of 4.95 mg g-l increased
growth parameters as follows: photosynthetic rates
from 0.156 ± 0.102 to 0.693 ± 0.156 mg CO -2 -1 2 m s
chlorophyll content from 454 ± 72 to 726 ± 137 mg m -2
2
total leaf area from 84.5 ± 51.9 to 290.0 ± 37.7 cm
total leaf biomass from 0.23 ± 0.10 to 0.81 ± 0.22g,
plant biomass from '1.07 ± 0.44 to 4.49 ± 0.78g and
,,
leaf extension rate from 16.2 ± 3.96 to 37.4 ± 3.45
-1 .
mm day . Root/shoot ratip decreased from 0.50 ± 0.08
to 0.11 ± '0.05. lncrease in 1eaf,sulphur content from
a law value of 0.14 to. a high value of 1.97 mg g-l
increased the growth parameters fts £ollows: photo~
synthetic rates from 0.296 ± 0.125 to 0.505 ± 0.168 mg
- 2 I -1 :~
CO2 m s ,chlorophyll content from 300 ± 90 to 506 ±
- 2 <
65,mg ill'" total leaf area from 80.5 ± 35.0 to 270.4 ±
2·
62.6 cm , total leaf biomass from 0.23 ± 0.08 to 0.72
±0.19g, and leaf extension rate from 13.9 ± 2.5 to
35.3 ± 3.8 mm day-I. The root/shoot ratio decreased
..from 0.51 ± 0.08 to 0.07 ± 0.01 .
- xxi
The effect of temperature (lO~35 °C) and irradiance
(17~342 ~mole m~2 s~l) on papyrus growth was
investigated under controlled environment. Between
the lowest (lOoC) and the optimum (250C) temperature,
-1 -1
papyrus growth rates (g g week ) increased as
follows: 0.48 ± 0.17 to 1.27 ± 0.07 for whole plants,
0.53 ± 0.08 to 1.25 ± 0.07 for shoots, 0.52 ± 0.20 to
1~39 ± 0.10 for roots and 0.45 ± 0.18 to 1.21 ± 0.06
for leaves. Highest value of specific leaf area (5.26
2 -1 0 ± 0.32 dm g ) at 20 C decreased to the lowest value
2 -1 0 0 (4.72 ± 0.22 dm g ) at 35 C. Between 15 and 35 C
leaf area ratio increased from 2.67 ± 0.18 to 3.18 ±
2 -1 . 0
0.21 dm g . Between 10 and 35 C leaf weight ratio ..•..,
increased from 0.54 ± 0.02 to 0,,67 ± 0.02. Unit leaf
, - 2
rate increased from 18.1 ± 5.4 to 44.7 ± 5.7 g m
",
week-I. Leaf extension rate increased from 4.1 ± 0.03
mm d~y-l at iooc to-a maximum rate of 75.1 ± 7.3 mm
day -'I at 3(tOC.
Although at the lowest irradiance (17 ~mole m-2
-1
s ) relative growth rates were negative they increased
with increasing irradi~ce. At the highest irra-
~2 -1 "'-.
diance (342 ~mole m s ) relative growth rates were
1.67 ± 0.05, 1.67 ± 0.04, 1.70 ± 0.08 and 1.65 ± 0.05
-1 -1
g g week for whole plants, shoots, roots and
leaves respectively. Values of specific leaf area
(7.84 ± 0.~3 dm2 g-l) and leaf area ratio (4.95 ± 0.38
dm g-l) at 17 ~mole m-2 s-l decreased to 3.50 ± 0.26
2 -1 - 2 and 2.10 ± 0.11 dm g respectively at 342 ~mole m
~RSITY OF NA TDrun-2 -1
m s Leaf weight ratio was highest at 68 vmo1e
m-2 s-l but decreased to 0.57 ± 0.01 at 342 ~mo1e m-2
s-l. Between 17 and 342 ~mole m-2 s-l unit leaf rate
increased from -1.13 ± 1.01 to 66.13 ± 1.96 g m-2
week-I. No leaf extension was detected at 17 ~mo1e
m -2 s-1 . However, leaf extension rates increased at
higher irradiances so that a maximum rate of 60.4 ±
6.6 mm -1 -2 -1 day was attained at 265 m-2 s-1 . | en |
