Effect of recurrent fires on soil nutrient dynamics in a tropical dry deciduous forest of Western Ghats,India

The role of forest fires in the soil dynamics and global carbon cycle has not been comprehensively studied in tropical forests as the effects of fire on tropical forest soils can be extremely variable. This study was aimed to understand how repeated fires affect physical and chemical properties of soil in a tropical dry deciduous forest and alter soil fertility and health. The study was carried out in the dry deciduous forest of Mudumalai Tiger Reserve. Soil samples were collected from unburned (B0) to six-time burned (B6) plots. Samples were collected from each plot from three different depths viz. 0–10 (Top), 10–20 (Middle), and 20–30 cm (Bottom) and analyzed for soil physical and chemical properties. Soil pH, EC, WHC decreased with increasing fire frequencies while bulk density increased. Organic Carbon, Total N, and available P decreased with increasing fire frequencies whereas extractable K initially increased but decreased with the very high frequency of fires. NO₃^?N slightly decreased with high fire frequencies but NH₄^?N decreased significantly with increasing fire frequency. These results provide a new insight regarding the influence of repeated fires on soil that will be valuable to understand the effect of fire on the recovery of soils and nutrient dynamics.     

Diversity of soil fungi in dry deciduous forest of Bhadra Wildlife sanctuary, western Ghats of southern India

We assessed soil fungal diversity in the dry deciduous forest of a Bhadra Wildlife Sanctuary of the Western Ghats(210.31 m a.s.l.;N 13°44’ and E75°37’).Soil samples were collected by random mixed sampling during winter(November,2008),summer(March,2009) and monsoon(August,2009) seasons,and physico-chemical parameters were recorded.During winter,summer,and monsoon seasons,49,45 and 49 of fungal species belongs to 20,18 and 19 of genera were isolated,respectively.Isolated soil fungi were mainly of the Mitosporic fungi,followed by Zygomycotina,Ascomycotina,Oomycotina and Coelomycetes.Indices of diversity,dominance and fisher alpha during winter,summer and monsoon seasons were 3.756,3.638 and 3.738(H’),0.9737,0.9694 and 0.9726(1-D) and 18.84,29.83 and 19.46(α),respectively.Spearman’s(r) correlation coefficient of fungal population with physico-chemical parameters of soils showed significantly positive and negative correlations(p<0.01) during winter,summer and monsoon seasons.Physico-chemical soil parameters played an important role in the occurrence,diversity,distribution,and relative abundance of fungal species in the tropical dry deciduous forest soil.     

Structure and floristic composition of tree stand in tropical forest in the Eastern Ghats of northern Andhra Pradesh,India

The changes in species composition, abundance and forest stand structure were analyzed across altitudinal regimes in tropical for- ests of Eastern Ghats of northern Andhra Pradesh, India. Three 1-ha plots were established with one each in low, medium and high altitudes. A total of 153 species, 2129 stems (709 stems ·ha -1 ) of ≥10 cm girth were enumerated. Species richness and diversity pattern varied along altitud- inal gradient and increased with the altitude. Species richness varied from 52 to 110 species·ha -1 and stand density from 639 to 836 stems·ha -1 with average basal area of 34.39 m 2 ·ha -1 . Shannon-Wiener index (H’) ranged from 4.55 to 5.17. Low altitude (i.e., Site 1) is dominated by Xylia xylocarpa (59.22) and Lagerstroemia parviflora (23.90), medium altitude (i.e., Site 2) by Xylia xylocarpa (45.50) Bursera serrata (17.29), and high altitude (i.e., Site 3) has Schleichera oleosa (28.25) Pterocarpus marsu- pium (26.55) as predominant species. Taxonomically, Rubiaceae (12 species), Fabaceae (12), Euphorbiaceae (11), Rutaceae (7) and Lauraceae (7) were dominant families. Density-wise, Fabaceae, Combretaceae, Euphorbiaceae, Anacardiaceae and Myrtaceae were abundant. Thus, conservation assessment based on altitudinal regimes and the information on species structure and function can provide baseline information for monitoring and sustaining the biodiversity.     

Contribution of participatory forest management towards conservation and rehabilitation of dry Afromontane forests and its implications for carbon management in the tropical Southeastern Highlands of Ethiopia

Participatory forest management (PFM) has been applied as an approach to create a framework for collaborative forest management between local communities and government forestry agencies. This study was designed to assess the contribution of PFM approach in improving forest status in the Southeastern Highlands of Ethiopia. Landsat satellite imageries of four years were used to evaluate the trends and rate of deforestation before and after PFM interventions. Socio-economic data were collected from sample household surveys, key participants, focus group discussions, and field observations. The results showed that there was high rate of deforestation before PFM intervention as forestland has decreased by 19% (2531 ha) between 1990 and 2000. However, after the PFM intervention (2000–2016), the forest cover has increased by 247 ha (2.2%). During this period, net 1016 ha of shrub-lands were converted into forestland owing to significant forest regeneration. In addition, most sampled households (94% and 96% from lower and upper altitudes, respectively) perceived that PFM had significantly contributed to improve forest regeneration in their locality. This study revealed that PFM can serve as a stepping stone for carbon financing mechanisms to reduce greenhouses emission and enhance carbon sinks via forest resources.     

Relationship between annual rainfall and tree mortality in a tropical dry forest: Results of a 19-year study at Mudumalai,southern India

Variability in rainfall is known to be a major influence on the dynamics of tropical forests, especially rates and patterns of tree mortality. In tropical dry forests a number of contributing factors to tree mortality, including dry season fire and herbivory by large herbivorous mammals, could be related to rainfall patterns, while loss of water potential in trees during the dry season or a wet season drought could also result in enhanced rates of death. While tree mortality as influenced by severe drought has been examined in tropical wet forests there is insufficient understanding of this process in tropical dry forests. We examined these causal factors in relation to inter-annual differences in rainfall in causing tree mortality within a 50-ha Forest Dynamics Plot located in the tropical dry deciduous forests of Mudumalai, southern India, that has been monitored annually since 1988. Over a 19-year period (1988–2007) mean annual mortality rate of all stems >1 cm dbh was 6.9 ± 4.6% (range = 1.5–17.5%); mortality rates broadly declined from the smaller to the larger size classes with the rates in stems >30 cm dbh being among the lowest recorded in tropical forest globally. Fire was the main agent of mortality in stems 1–5 cm dbh, elephant-herbivory in stems 5–10 cm dbh, and other natural causes in stems >10 cm dbh. Elephant-related mortality did not show any relationship to rainfall. On the other hand, fire-related mortality was significantly negatively correlated to quantity of rainfall during the preceding year. Mortality due to other causes in the larger stem sizes was significantly negatively correlated to rainfall with a 2–3-year lag, suggesting that water deficit from mild or prolonged drought enhanced the risk of death but only with a time lag that was greater than similar lags in tree mortality observed in other forest types. In this respect, tropical dry forests growing in regions of high rainfall variability may have evolved greater resistance to rainfall deficit as compared to tropical moist or temperate forests but are still vulnerable to drought-related mortality.     

辽东山区原始红松混交林土壤有机碳及其影响因素研究

以辽东山区原始红松混交林为研究对象,对比分析了不同树种组成下原始红松混交林土壤有机碳含量的差异,研究了土壤有机碳与土壤属性因子和植被覆盖因子的相关关系,并研究了土壤碳密度的分布规律。结果显示,3种原始红松混交林土壤有机碳含量均随着剖面深度的增加而降低;0~10 cm土层深度土壤有机碳含量为红松阔叶林阔叶红松林针阔混交林,表层土壤有机碳主要来源于枯落物层的分解,表层土壤有机碳的特征表明原始红松混交林树种构成不同,潜在地影响着生态系统内的碳循环。对土壤属性因子而言,碳氮比与有机碳含量呈极显著的正相关关系,而容重、pH值呈显著的负相关关系;对植被覆盖因子而言,枯落物有机碳、全氮、碳氮比与土壤有机碳含量则无相关关系;0~100 cm深度内红松阔叶林的土壤碳密度最大,为181.4 t/hm2,针阔混交林次之,为180.56 t/hm2,阔叶红松林最小,为150.78 t/hm2,且接近70%的土壤碳储存集中在40 cm以上的土层内。旨在为揭示原始红松混交林对土壤有机碳的影响因素和探索我国原始红松混交林土壤碳分布格局提供科学依据。     

燕山北部华北落叶松人工林与杨桦天然次生林土壤碳密度的比较

为了了解人工造林过程对土壤碳储量的影响,对燕山西部山地常见的华北落叶松人工林和杨桦天然次生林土壤有机碳含量进行了研究。结果表明,华北落叶松人工林和杨桦天然次生林的土壤剖面平均有机碳含量分别为30.45g/kg和28.45g/kg,二者没有明显差异;2种林分的土壤有机碳含量均随着土层深度的增加而降低,下降幅度则随深度的增加逐渐减缓,表层土壤对土壤的碳存储贡献更大。总的来看,土壤有机碳含量在深层(30cm以下)相邻土层之间差异不显著,说明深层土壤中,有机碳含量变化较小。由以上结果可以得出结论,在造林措施适当、人为干扰较少的条件下,人工林同样可以维持与天然林相近的较高的土壤碳储量。     

利用卫星遥感和GIS技术测定印度切蒂斯格尔地区干旱热带森林的土地利用、生物量和碳贮量

2001-2002年间,利用卫星遥感和GIS技术研究印度切蒂斯格尔邦的赖布尔地区干旱热带森林的土地利用、生物量和碳贮量情况。主要森林类型为:柚木森林、混合林、衰退森林和婆罗双树混交林。在这些不同森林类型中,立地的坡度和坡面影响森林植被类型、生物量和碳贮量。不同森林类型中,木材积蓄积量、生物量和碳贮量的变化范围分别为:35.59～64.31 m3·hm-2、45.94～78.31Mg·hm-2和22.97～33.27Mg·hm-2。混合林中每公顷的木材蓄积量、生物量和碳贮量最大,衰退森林中的最低。混合林、柚木森林、衰退森林和婆罗双树混交林的总碳量分别为8170.72 Mg、81656.91 Mg、7833.23 Mg和7470.45 Mg。蒂斯格尔邦地区干旱热带森林处于不成熟的生长阶段,且具有很强的碳回收潜力。图6表7参49。     

Carbon density and accumulation in woody species of tropical dry forest in India

We studied the carbon density and accumulation in trees at five sites in a tropical dry forest (TDF) to address the questions: how is the TDF structured in terms of tree and carbon density in different DBH (diameter at breast height) classes? What are the levels of carbon density and accumulation in the woody species of TDF? Is the vegetation carbon density evenly distributed across the forest? Does carbon stored in the soil reflect the pattern of aboveground vegetation carbon density? Which species in the forest have a high potential for carbon accumulation? The WSG among species ranged from 0.39 to 0.78 g cm⁻³. Our study indicated that most of the carbon resides in the old-growth (high DBH) trees; 88-97% carbon occurred in individuals ?19.1 cm DBH, and therefore extra care is required to protect such trees in the dry forest. Acacia catechu, Buchanania lanzan, Hardwickia binata, Shorea robusta and Terminalia tomentosa accounted for more than 10 t ha⁻¹ carbon density, warranting extra efforts for their protection. Species also differed in their capacity to accumulate carbon indicating variable suitability for afforestation. Annually, the forest accumulated 5.3 t-C ha⁻¹ yr⁻¹ on the most productive, wettest Hathinala site to 0.05 t-C ha⁻¹ yr⁻¹ on the least productive, driest Kotwa site. This study indicated a marked patchy distribution of carbon density (151 t-C ha⁻¹ on the Hathinala site to 15.6 t-C ha⁻¹ on the Kotwa site); the maximum value was more than nine times the minimum value. These findings suggest that there is a substantial scope to increase the carbon density and accumulation in this forest through management strategies focused on the protection, from deforestation and fire, of the high carbon density sites and the old-growth trees, and increasing the stocking density of the forest by planting species with high potential for carbon accumulation.     

印度西部5种热带干落叶林中凋落物中生物元素和返回到绿叶中的季节性变化(英文)

本文对印度西部5种热带干落叶林中凋落物里生物元素的季节性变化和它们返回到新鲜叶中季节性变化进行研究。对5个树种:阿拉伯金合欢(Acacia nilotica L.)、金合欢(Acacia leucophloea Roxb.)、柚木(Tectonagrandis L.f.)、绒毛野独活(Miliusa tomentosa Roxb.)和紫矿(Butea mono-sperma Lain.)中凋落物的成熟叶、枝和再生部分的N、P、Ca、Mg、K和Na的浓度,以及老叶和幼叶中浓度间的关系进行调查。对这些树种的总干物质进行记录,并分析它们所含的N、P、Ca、Mg、K和Na的含量。其中阿拉伯金合欢叶子中N的含量最高,而金合欢的叶子里Ca和Mg含量最高。叶中含P最多的是阿托伯金合欢、金合欢和紫矿,而含P最少的是柚木和绒毛野独活。K和Na含量在这些树种中没有明显的区别。观察发现,N、P和K的浓度随季节变化大,但Ca和Mg则不然。唯有钾在所有树种中都是最稳定的,吸收N和P可以用于来年新叶的生长。从老叶和凋落物中吸收的营养会支持新叶的生长,并增加土壤的肥力。图1表4参30。     

Anthropogenic disturbances and status of forest and wildlife in the dry deciduous forests of Chhattisgarh state in India

The advent of modern forces and the changes in socioeconomic patterns of forest dwellers have increased the pressures on the forests. In order to mitigate such pressures and also to protect the forests and wildlife the model of protected areas networks has shifted and enhanced such pressures in the unprotected natural forests due to several reasons. Being a low profile category of protected status and continuous human settlements, the present study highlights the case of dry deciduous forests of Sarguja district of Chhattisgarh state of India. The major objectives of this study were to quantify the status of forests and wildlife and also to determine the extent of anthropogenic disturbances faced by the dry deciduous forests of central India. Transect and silent drive count methods were used for sampling wildlife and quadrat method was used for sampling vegetation. Besides, the local uses of various forest produces were also studied in view of understanding the people dependency on forests. The forest vegetation, in the study area, was pre-dominated by Shorea robusta, which had Madhuca indica, Diospyrus melanoxylon and Buchnania lanzan as the major companion species. The forest had either the high girth class mature tree species or the saplings. The low vegetation cover and density were due to the high anthropogenic pressures mainly in the form of heavy livestock grazing and collection of ethnobotanically important species. The study though reveals that the area is not rich in wildlife and the forest is fragmented, the area still supports some important species, which include many rare and endangered plants and animals. The findings of this study have been discussed in view of the management and conservation of the forest and wildlife in the dry deciduous forests.     

Temporal dynamics and spatial variations of forest vegetation carbon stock in Liaoning Province,China

There are many uncertainties in the estimation of forest car- bon sequestration in China, especially in Liaoning Province where vari- ous forest inventory data have not been fully utilized. By using forest inventory data, we estimated forest vegetation carbon stock of Liaoning Province between 1993 and 2005. Results showed that forest biomass carbon stock increased from 68.91 Tg C in 1993 to 97.51 Tg C in 2005, whereas mean carbon density increased from 18.48 Mg·ha -1 C to 22.33 Mg·ha -1 C. The carbon stora...     

Estimations of total ecosystem carbon pools distribution and carbon biomass current annual increment of a moist tropical forest

With increasing CO₂ in the atmosphere, there is an urgent need of reliable estimates of biomass and carbon pools in tropical forests, most especially in Africa where there is a serious lack of data. Information on current annual increment (CAI) of carbon biomass resulting from direct field measurements is crucial in this context, to know how forest ecosystems will affect the carbon cycle and also to validate eddy covariance flux measurements. Biomass data were collected from 25 plots of 13 ha spread over the different vegetation types and land uses of a moist evergreen forest of 772,066 ha in Cameroon. With site-specific allometric equations, we estimated biomass and aboveground and belowground carbon pools. We used GIS technology to develop a carbon biomass map of our study area. The CAI was estimated using the growth rates obtained from tree rings analysis. The carbon biomass was on average 264 ± 48 Mg ha⁻¹. This estimate includes aboveground carbon, root carbon and soil organic carbon down to 30 cm depth. This value varied from 231 ± 45 Mg ha⁻¹ of carbon in Agro-Forests to 283 ± 51 Mg ha⁻¹ of carbon in Managed Forests and to 278 ± 56 Mg ha⁻¹ of carbon in National Park. The carbon CAI varied from 2.54 ± 0.65 Mg ha⁻¹ year⁻¹ in Agro-Forests to 2.79 ± 0.72 Mg ha⁻¹ year⁻¹ in Managed Forests and to 2.85 ± 0.72 Mg ha⁻¹ year⁻¹ in National Park. This study provides estimates of biomass, carbon pools and CAI of carbon biomass from a forest landscape in Cameroon as well as an appropriate methodology to estimate these components and the related uncertainty.     

Active organic carbon pool of coniferous and broad-leaved forest soils in the mountainous areas of Beijing

In order to explore the effects of different forest types on active soil carbon pool, the amounts and density of soil organic carbon (SOC) were studied at different soil horizons under typical coniferous and broad-leaved forests in the mountainous area of Beijing. The results showed that the amount of total SOC, readily oxidizable carbon and particulate organic carbon decreased with increasing depths of soil horizons and the amounts at depths of 0–10 cm and 10–20 cm in broad-leaved forest was clearly higher than that in coniferous forests. The trend of a decrease in SOC density with increasing depth of the soil horizon was similar to that of the amount of SOC. However, no regular trend was found for SOC density at different depths between coniferous forest and broad-leaved forests. The ratio of readily oxidizable carbon to total amount of SOC ranged from 0.36–0.45 and the ratio of particulate organic carbon to total amount of SOC from 0.28–0.73; the ratios decreased with increasing depths of soil horizons. Active SOC was significantly correlated with total SOC; the relationship between readily oxidizable carbon and particulate organic carbon was significant. A broad-leaved forest may produce more SOC than a coniferous forest.     

尼加拉瓜Chacocente野生动物保护区三种干旱落叶阔叶树种的天然更新动态(英文)

在尼加拉瓜Chacocente野生动物保护区对极又平荚木,毛风铃木和Lonchocarpus minimiflorus(Donn.Sm.)树种的天然更新进行了调查,并分析了更新异质性与地形坡度和入射光的关系。从2001到2003连续3年记录了高度10m以下和直径10cm以下的苗木和幼树。结果表明,3个树种的天然更新的个体数量的密度明显不同,并随时间存在差异。与极叉平荚木相比,L.minimiflorus和毛风铃木天然更新密度较大,只有毛风铃木种群密度方面的净变化是正相关。在树冠部分曝光的条件下,在缓坡和陡坡上更新较好,形成了分布聚集分布,尤其是L.minimiflorus和毛风铃木。仅靠天然更新不足以维持这些树种理想的立木数量,应当采取直接的恢复措施以促进天然更新过程。参47表3图3。     

Uses of tropical deciduous forest species by the Yucatecan Maya

We present the uses that the Maya of Tixcacaltuyub and Tixpeual, Yucatán, México, have for the trees and shrubs of their surrounding tropical dry and deciduous forests; we add the uses for trees and shrubs in their homegardens, because they complement their basic needs. A total of 301 shrubs and tree species were present either in the forest or homegardens sampled; 222 species (73.7%) have at least one reported use. The species with more uses are: Bursera simaruba (10), Gliricidia sepium (10), Cordia dodecandra (9), Plumeria rubra (7), Caesalpinia gaumeri (7), Vitex gaumeri (7), Enterolobium cyclocarpum (7), and Piscidia piscipula (7). More species (152/69.7%) are classified for medical purposes, followed by apiculture (87/39.9%), food (66/30.3%), fuel (38/17.4%), building (41/18.8%) and timber (25/11.5%). Despite the lack of important commercial species (timber, fruit) in this type of tropical forest, we discuss the importance of the tropical dry forest of Yucatán as an area where management could lead to sustainable production of honey, deer and building material for houses.

---

Resumen Presentamos los usos que los mayas de Tixcacaltuyub y Tixpeual, Yucatán, México, le dan a los árboles y arbustos presentes en los bosques tropicales deciduo y seco que les rodean. Asímismo, agregamos los usos para los árboles y arbustos del huerto familiar, ya que estos complementan sus necesidades básicas. Se encontraron un total de 301 especies de árboles y arbustos en el bosque y los huertos; 222 especies (73·7%) tienen al menos un uso reportado. Las especies con más usos son: Bursera simaruba (10), Gliricidia sepium (10), Cordia dodecandra (9), Plumeria rubra (7), Caesalpinia gaumeri (7), Vitex gaumeri (7), Enterolobium cyclocarpum (7) y Piscidia piscipula (7). Se clasificaron mas especies (152/69.7%) para uso medicinal que para cualquier otro uso, le siguieron en orden decreciente, apicolas (87/39.9%), alimenticias (66/30.3%), combustibles (38/17.4%), para construcción (41/18.8%) y maderables (25/11.5%). A pesar de la ausencia de especies importantes comercialmente (maderables, frutos) en este tipo de bosque, discutimos la importancia del bosque tropical seco de Yucatán como un área en la cual el manejo puede conducir a un aprovechamiento sostenido para apicultura, alimento para venado y material para construir habitaciones.

     

Deforestation and forest fragmentation in the highlands of Eastern Ghats,India

Tropical forest cover change along with increasing fragmentation has detrimental effects on the global biodiversity. In the current study change in both forest cover and fragmentation of Koraput district have been assessed in the past three decades(1987-2017) and future decade(2017-2027), which has been modelled using logistic regression showing a gradual decrease in the forest cover and increase in fragmentation. The long term deforestation rates from 1987 to 2017(current period) and from 1987 to 2027(predicted period) were found to be-0.018 and-0.012, respectively. Out of the total geographical area, 2027 number of grids(1 km2) out of 8856 grids were found to have shown extinction of forest in the study period. The conversion of forested lands into other land uses has been one of the major causes of deforestation in Koraput, especially because of the increasing mining activities and establishment of three major industries namely National Aluminium Company(NALCO), Damanjodi, Hindustan Aeronautics Limited(HAL), Sunabeda and Ballarpur Industries Limited(BILT). The forest fragmentation reveals a negative trend, recording highest conversion from large core fragments to edge(191.33 km2) and the predicted period has also shown the same trend of negative change, which poses serious danger to the structure of the forests. Out of all the landscape matrices calculated, number of patches will increase to 214 in 2027 from 93 in 1987. In the test between geographically weighted regression(GWR) and ordinary least square regression(OLS), GWR was the better fit model for drawing a spatial relationship between forest cover and fragmentation changes. The study confirmed that the forest cover change has impacted the forest fragmentation in the study area. The programmes like REDD + should be implemented along with the experiences of Community Forest Management and the joint forest management should be intensified at community level in order to develop better management practices to conserve habitats in biodiversity rich areas.     

Composition,structure and diversity of phyllostomid bat assemblages in different successional stages of a tropical dry forest

Studies on successional dynamics in tropical systems have mostly focused on plant communities and mainly have been conducted in tropical humid areas. Here, we document changes in the structure of bat assemblages among secondary successional stages of a neotropical dry forest. We specifically focused on the speciose phyllostomid bat family, comprising most of the foraging guilds found among neotropical bats, including nectarivores and frugivores that play important roles in processes of plant reproduction and forest regeneration. To investigate bat species richness, diversity and abundance during successionnal processes, we mist-netted bat assemblages in 12 sites belonging to 4 different successional stages, namely pastures (0 yrs), early (3–5 yrs), intermediate (8–12 yrs) and late successional stage (>50 yrs). A capture effort of 142 nights using five mist-nets per night yielded 606 phyllostomid bats belonging to 16 species. Late stage was the most speciose sustaining all species found in the study (16 species against 9 for early and intermediate stages and 4 in pastures), and was the only environment where rare species occurred. Species found within any one successional stage were a combination of species found at the previous stage plus additional ones. This additive pattern appeared to be driven by the natural abundance of species, as the abundant species were found across more succesisonal stages than rarer species. Bats were significantly less speciose and less abundant in pastures, regardless of the foraging guild. Bat diversity and abundance did not differ significantly among early, intermediate and late stages. However, nectarivores were more abundant in early compared to late stage, probably as a consequence of differences in patterns of food availability. We conclude that areas of forest, recognized as late stage in our study, are the most important reservoirs of species richness. Secondary vegetation also contains diverse bat assemblages, while pastures only harbour a few abundant and vagile species occasionally crossing this habitat. We suggest that land-use regulations in this region focus on maintaining connectivity of a mosaic of areas of secondary and mature vegetation to insure the conservation of bat diversity as well as their important ecological interactions.     

Successional patterns and gap phase dynamics of a humid tropical forest of the Western Ghats of Kerala, India: ground vegetation, biomass, productivity and nutrient cycling

The population dynamics of the ground vegetation and its energetics such as biomass accumulation and net primary productivity, and the nutrient cycling patterns in the humid tropical forest of the Western Ghats in India are largely determined by gap age and by whether gaps are formed naturally or through selection felling. Responses of plant categories such as herbs, shrubs, tree seedlings and saplings also vary depending upon gap type and age. An exotic species such as Chromolaena odorata occurred only in selection-felled gaps ((9 ± 3)−(49 ± 4) individuals (100 m)⁻²). Nilgirianthus ciliatus, a dominant shrub, plays a key role in the gaps in determining population dynamics of others. The net primary productivity of the ground vegetation, which is about 31.17 ± 4.26 kg (100 m)⁻² year⁻¹ in an undisturbed site, increased a year after gap formation to 102.82 ± 6.46 kg (100 m)⁻² year⁻¹ in natural gaps and to 71.82 ± 2.36 kg (100 m)⁻² year⁻¹ in selection-felled gaps. Five years after gap formation, net primary productivity of the ground vegetation declined considerably, this being related to decline in fast-growing shrub and secondary tree species in the vegetation and gap closure. A similar trend was also recorded for the rates of nutrient uptake and nutrient accumulation in the vegetation.

In natural gaps the soil nutrient level increased gradually with gap age. This could be attributed to slow release of nutrients from the fallen trunks and nutrient storage in the rapidly recovering vegetation. In contrast, in selection-felled gaps, the quantities of soil nutrients such as nitrogen, phosphorus and magnesium were higher in 1-year-old gaps than in undisturbed sites, owing to the release of these nutrients from leaf litter and wood debris which were deposited in larger quantities within the gap itself, and owing to sparse ground vegetation resulting from the greater disturbance of the soil, in the first 1 or 2 years. The fractional annual turnover rates of elements of the ground vegetation and the soil were higher in 1-year-old gaps and declined with gap age. The significance of these results for forest management is discussed.     

Soil physical properties and preferential flow pathways in tropical rain forest, Bukit Tarek, Peninsular Malaysia

Soil physical properties and water movement within soil were investigated using dyes in a tropical rain forest, the Bukit Tarek Experimental Watershed of Peninsular Malaysia. The saturated hydraulic conductivity (K _s) decreased with increasing soil depth. TheK _s values were higher than those reported for other tropical soils. The geometric means of theK _s values ranged from 4.69×10⁻³ (80 cm) to 4.07×10⁻² cm s⁻¹ (10cm). This suggests saturation overland flow may not be dominant but that subsurface flow must play an important role in stormflow generation. The shapes of the soil moisture characteristic curves resembled those of forest soils which have large changes in volumetric water content at pressure heads <30 cmH₂O. The relatively high conductivities were due to the presence of a porous zone of decomposed root channels which existed continuously in vertical direction. Besides decayed roots, living roots also encourage preferential flow in vertical and lateral (downslope) directions. Termite activities may also form water flow pathways in tropical regions. These detailed results help us analyze water flow within the soil in tropical rain forests.