Human activity disturbances on the structure and impacts on the service values of the coastal ecosystems in Tanzania
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Date
2018-12
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Fujian Agriculture and Forestry University
Abstract
This study aimed to investigate and document human activities disturbances
on the ecosystems structure and impacts on ecosystem services values (ESV)
along the coastal areas of Tanzania. The study provides initial understanding
about spatial characteristics ofsoils and vegetation on human disturbed sites
in comparison with the intact sites, and establishment of temporal coastal
ESV to provide information for sustainable management of tropical
ecosystems in Tanzania. Specifically, this study aimed 1. To establish spatial
variation on soil physical properties (electrical conductivity, soil texture and
bulk density), and soil chemical properties (nitrogen (N), carbon (C),
phosphorus (P), calcium (Ca), magnesium (Mg), potassium (K) and sodium
(Na) across disturbed and intact sites of the coastal ecosystems; 2. To
investigate the impacts of human activities disturbances on the vegetation
and regeneration potential of naturally occurring tropical coastal forests; 3.
To establish the correlations between vegetation and soil properties of the
human disturbed and intact coastal forest ecosystems; 4. To explore how
socioeconomic activities contribute to temporal change of coastal
ecosystems and their impacts of changes on the coastal ESV; 5. To identify
and gauge the current restoration interventions and factors influencing
restoration of the disturbed coastal ecosystems in Tanzania.
This study was conducted by collecting data from the Coastal Zone sites in
Tanzania. The zone stretches within 850km from the boarder of Tanzania
and Kenya in the north, and Tanzania and Mozambique in the south. The
zone represents the coastal ecosystems, which are affected by human
disturbances especially between 2000 and 2016. The classification of land
cover and land uses was firstly computed from the areas that cover S37 00,
S37 50 and S37 50, S37 10 geographical coordinates. Samples were
collected from Uzigua Forest Reserve (UFR). Certainly, this forest is within
100 km from the coastline of Indian Ocean, thus the reserve is considered
among the true representative of the Tropical Coastal Ecosystems in
Tanzania.
The study collected bio-physical and socioeconomic data to understand the
interplays between human activities, structure and services of the coastal
sites. Soil samples were collected from ADS, DGS and CFS in forty-seven
(25m x 25m) sampling plots. Each site provided 47 samplings plots, which
resulted into 141 plots in total. These plots were laid randomly because
agriculture and livestock grazing are not uniformly distributed within the
ecosystems. In each of the plots, 10 soil samples were collected from 1-
30cm depth because agriculture and livestock grazing activities affect the
surface and near surface layers ofthe soils. Representative soil samples were
put into tightened double plastic bags, labeled and stored at 4°C to reduce
further microbial degradation during transportation and storage in the
laboratory. Fresh air-dried and oven-dried weights were determined before
subjecting soil samples into further laboratory analysis.
Soil physical and chemical properties were analyzed as follows: Electric
conductivity was determined by electrical conductivity meter, soil texture by
pipette method and bulk density calculated by dividing dry weight of soils
by volume. Determination of total nitrogen followed the Kjeldahl acid digestion procedures while total carbon were analysed by the Walkley-Black
procedures. Potassium Dichromate (KoCriCh) and concentrated Sulphuric
Acid (H2SO4) were used to produce the reaction and products. Available
phosphorus was determined by the Bray-II method. The Ammonium Acetate
was used to extract exchangeable Ca, K, Mg and Na. Then K content was
determined by using flame photometer while ethylenediaminetetraacetic acid
(EDTA) titration was done to measure Ca, Mg and Na. A combined glass calomel electrode used to determine the pH of aqueous suspensions.
Tree inventories were prepared on each sites to determine forest structure in
the human disturbed areas compared to intact sites. From live trees (i)
number oflive trees per unit area (N/ha), (ii) basal area of live trees (m2 /ha),
and (iii) volume of live tree per unit area (m3 /ha). Basal area and volume
were compared between and across CFS, ADS and DGS. The mean values
and t-test were used to compare and judge the variations, which exist across
the sites. The results were considered significant atp < .050.
To analyze the differences in vegetation the following parameters were
computed (i) Shannon diversity index, (ii) Simpson diversity index, iii)
species evenness and (iv) the importance value index (IVI). Each of the
computed diversity indices were subjected into the Microsoft Excel 10 and
Statistical Package for Social Sciences Software (SPSS) for production of
means, standard deviation and t-tests.The Detrended Canonical
Correspondence Analysis (DCCA)) was used to obtain multiple linear
regressions and optimal linear combination between tree parameters and soil
variables for comparisons across CFS, ADS and DGS. To analyze the
impacts of human activities on changes of ecosystems, land cover and land
use (LCLU) and estimation of ESV, area changes were detected based on
differences between imagery identification ofthe changed areas. The LCLU
information were used to compare land changes in relationships with the
socioeconomic activities, and the dynamics of ESV in the coastal zone. The
LCLU data for 2000 and 2010 were from the Globe Land 30 mapping
products at 30-meter spatial resolution developed by National Geomatics
Center of China, while 2016 images were produced from Landsat 8.
Classification of images was done from Landsat TM/ETM+ for 2000, 2010
and 2016 years complemented with MODIS and Normalized Difference
Vegetation Index time series, and Chinese HJ imagery. The LCLU
categories and ecosystem service coefficients used to compute ESV on each
LCLU categories.
There were significant variations in spatial soil properties as well as forest
structural parameters and temporal ecosystems service values. 1. The mean
variation in electrical conductivity (pS/cm) between CFS and ADS was
26.197 ± 8.42; CFS and DGS was 5.55 ± 7.45; ADS and DGS was 20.65 ±
3.97. The soil particles ranged between 86.06% to 86.79% for sandy,
11.40% to 14.98% for clay and 1.81% to 2.57% for silt across land uses. The
bulk density in CFS and ADS was 0.05 ± 0.23, in CFS and DGS was 0.13 ±
0.02 and, in ADS and DGS was 0.08 ± 0.02. The mean values (percentage)
for nitrogen = 16.07 ± 0.34, 1.75 ± 0.25, 6.5 ± 0.20; carbon =14.48 ± 0.23,
11.81 ± 0.13, 12.24 ± 0.30; phosphorus =14.12 ± 6.57, 17.74 ± 3.96, and
13.31± 2.86 for CFS, ADS and DGS respectively. There were slightly lower
amount oftotal carbon on ADS than DGS. Carbon-nitrogen ratio was higher
in CFS than in the disturbed sites. The mean values for soluble bases were
3.75, 3.11 and 0.63 for Ca2+; 0.80, 5.87 and 6.67 for Mg2+; 0.03, 0.55, and
0.52 for K+; 0.01, 0.31 and 0.31 for Na+; 2.61, 13.74 and 16.36 (cmol(+)/kg)
for cation exchange capacity and 10.29, 5.86 and 4.42 (% volume ) for base
saturation in three areas: CFS, ADS and DGS.
2. There were significant variation across the vegetation stand parameters
and as well as for diversity indices. Plots in the CFS had higher mean values
of adult trees, basal area and volume than the ADS and DGS. Plots in ADS
had the highest Shannon-Wiener index of seedlings and saplings, followed
by CFS and DGS. The CFS and DGS had higher Simpson’s index for
seedlings and saplings than DGS. Plots in ADS and DGS had higher adult
tree Simpson than closed sites. The equitability of seedlings and saplings
was highest in CFS, followed by ADS and DGS. Plots in ADS had higher
equitability of adult trees than DGS and CFS. Moreover, plots in ADS and
DGS had higher importance value index for seedlings than CFS.
3. The multivariate canonical correlation showed significant variation across
CFS, ADS and DGS. The canonical correlation was F = 2.400, p < .012 for
tree stand parameters (TSP) and soil physical parameters (SPP). In ADS, the
F- test was 0.529, p = .938. In DGS, the significance of all canonical axes
was F = 1.207, p = .242. Correlation of soluble bases and TSP was F =
2.448, p = .018 in CFS, F = 0.687, p = .790 in ADS and F = 0.743, p = .808
in DGS. The values of non-soluble bases and TSP were F = 0.816, p = .572
in CFS, F = 0.687, p = .790 and F = .070, p = .020 in DGS. The SPP and
Shannon index was that F = 1.103, p < .388 in CFS, F = 0.520, p = .714 in
ADS and F = 0.932, p = .444 in DGS. The SPP and IVI was F = 0.042, p =
.996 in CFS, F = 0.819, p = 620 in ADS and F= 0.633, p = .724 in DGS.
Soluble bases and equitability was F = 0.119, p = .968 in CFS, F = 0.001, p
= .001 in ADS and F = 0.011, p = .001 in DGS. There were almost no
established correlation between CNP and equitability across CFS, ADS and
DGS.
4. Between 2000 and 2016, ecosystems along coast changed significantly.
The decline (ha) was in forest by -36 441 (-10%), grazing land by -6 347 (-
2%) and wetland by -112 (-2%). The expansion on LCLU areas was in shrub
land by 11 751 (37%), farm land by 30 506 (43%), waterbody by 279 (14%)
and artificial surface by 365 (14%). The ESV declined in forest cover by
12%, grazing land by 2% and wetlands by 2% while farmland increased by
30%, shrub land by 27% and water body by 12%. The ESV and the total
population ratios declined from $80.4, 63.8 and $46.0 million in 2000, 2010
and 2016 respectively. Perfect positive correlation was on LCLU change and
ESV, population and households in crop farming, livestock keeping and
bioenergy use.
5. The study found that afforestation, reforestation and retaining natural
growing trees are the major restoration interventions used along the coastal
zone of Tanzania. In some cases, eviction of forest invaders are executed to
allow disturbed forests to regenerate naturally. Socioeconomic and climatic
factors significantly have negatively affected artificially planted and natural
regenerating trees (p<.050). Indeed, there were limited understanding on the
ecological values of restoration interventions. Lack of improved planting
materials and local community overdependence on forests resources
significantly impede restoration interventions.
The implications of the findings is that human activities disturbances affect
the structure of ecosystems and services at large. Population and
socioeconomic activities are the main drivers and have increased demand, as a result the coastal ecosystems is losing ESV largely. If not abetted, there is
a danger of further impairments on these ecosystems. Therefore, this study
advise 1. To regulate population and socioeconomic activities to avoid
further negative impacts of coastal LCLU change. 2. To improve the current
restoration interventions by ensuring that the socioeconomic and ecological
interplays along the coastal zones are fully addressed. 3. To investigate and
establish minimum allowed crop-agriculture and livestock grazing
integration equilibrium point in the coastal sites is needed to make
socioeconomic activities a solution with no harm on coastal ecosystems.
Description
PhD-Thesis
Keywords
Tanzania, Coastal ecosystems, Agriculture disturbances, Livestock disturbances