This study covers the vegetation composition and diversity in two heavy metal sites with distinct climatic and edaphic environments in the Philippines, Zambales, and Surigao del Norte in the northern and southern regions, respectively, Tree density and basal area were higher in Zambales than in Surigao del Norte. Species diversity, however, was higher in Surigao del Norte site (H'=1.1071) than in Zambales, which may be attributed to high water and nutrient availability and unique geologic formations. Soil properties also varied, with higher organic matter concentration in Surigao del Norte. Twenty-one out of 35 taxonomic families in both sites were common in serpentine soils. Nine families were recorded to have a large number of individuals on both sites. A total of 11 species were known metallophytes of which four are Ni hyperaccumulators and seven are endemic to both sites. These Ni hyperaccumulators have a high potential for phytoremediation, phytostabilization, and rhizofiltration. However, due to the scarce information on Ni hyperaccumulators, conservation statuses of most of them are unknown. Agricultural interference, site destruction and excessive mining are some of the factors contributing to the diminishing fate of metallophytes. Thus, it calls for its prioritization in biodiversity conservation.
Due to extensive mining activities, strip vegetation and soil contamination with heavy metals have become common. One of the approaches to ecological restoration is phytostabilization, which uses plants to stabilize and reduce the mobility of heavy metals in the soil. In this study, six species of grasses – namely, Alloteropsis semialata (R.Br.) Hitchc., Cymbopogon citratus (DC.) Stapf, Dinochloa acutiflora (Munro) Soenarko, Imperata cylindrica (L.) Raeusch., Machaerina disticha (C.B. Clarke) T. Koyama, and Panicum repens L. – were collected from a degraded area with lateritic soil in Brgy. Taltal, Masinloc, Zambales, Philippines. The root growth, the direction of roots formed, and mean daily transpiration rate were observed to find a combination of grass species for phytostabilization. Leaf and root anatomical sections were observed using the freehand technique to know the characteristics that enable them to thrive in lateritic soil. D. acutiflora was the only species that exhibited horizontal and spreading roots and the fastest root growth among the six species, whereas A. semialata and P. repens were the deepest penetrating roots among the vertical forming roots. Transpiration rate was the highest at 12:00 PM and is significantly differentiated from 09:00 AM and 04:00 PM – as exhibited by the two exotic species, I. cylindrica and P. repens. Leaf anatomical features in the transverse section – such as thickened epidermal cell walls (anticline), presence of sclerenchyma caps, extended vascular bundles, and bulliform cells – were observed in the leaves of the six species. Root anatomical features observed were thickened epidermal cell walls (anticline), thick endodermis, and a large cortex filled with intercellular spaces (P. repens, D. acutiflora, and M. disticha), as well as black spots in the cortex and pericycle (A. semialata). Knowing these traits, A. semialata, D. acutiflora, and P. repens were found suitable for phytostabilization.
Following the international protocol for establishment of permanent plots, a two-hectare permanent biodiversity monitoring area (PBMA) was established inside Makiling Forest Reserve. Results of the intensive 100% inventory revealed that the PBMA holds tremendous tree diversity. A total of 155 tree species were identified. Of these, 148 are indigenous to the Philippines with 47 endemics (30% endemism). The most abundant native species in the PBMA is Magabuyo (Celtis luzonica) with 2,287 individuals, followed by Balobo (Diplodiscus paniculatus), Tinaang pantai (Drypetes maquilingensis), and Apanang (Mallotus cumingii). The average diameter for all trees inside the plot is 14.28 cm. More than 90% of the individual trees fall under the category poles and saplings while large trees account to only 0.6%. Twenty-nine (29) species are listed under either the Philippine Red List (Fernando et al. 2008) or the IUCN Red List of Threatened Species . Noteworthy among the list are the six critically endangered (CR) premium timber species including Makaasim (Syzygium nitidum), Kamagong (Diospyros discolor), Narra (Pterocarpus indicus), Bagtikan (Parashorea malaanonan), Guijo (Shorea guiso), and White lauan (Shorea contorta). The geodatabase that includes an interactive map developed in this study is of critical importance for future research activities in the area.
Plant growth and leaf photosynthesis were studied for saplings of two species in the Dipterocarpaceae family planted on open bare ground in the Philippines. The greatest rate of growth in height in the initial 14 months after planting was for Shorea contorta, followed by Dipterocarpus grandiflorus. The light-saturated photosynthetic rate (P max ) for S. contorta and D. grandiflorus was 9.9 ± 0.29 μmol m -2 s -1 and 5.5 ± 0.28 μmol m -2 s -1 , respectively. Dark respiration and apparent quantum yield efficiency did not differ between them. The daily course of photosynthesis showed the existence of a midday depression in net photosynthesis for S. contorta and D. grandiflorus on open bare ground. When the leaf-to-air vapor pressure difference (L-AirVPD) was abruptly raised to 30 hPa, the decrease in the rate of photosynthesis was the same for potted saplings of S. contorta and D. grandiflorus in the nursery. One reason for the difference in growth between species is thought to be the difference in carbon gain depending on a difference in P max between the species in the morning, before the leaves suffer from large L-AirVPD at midday.Discipline: Forestry and forest products Additional key words: leaf-to-air vapor pressure difference, open bare ground planting, photosynthetic rate, tropical rain forestThis research was conducted in a collaborative study
The study on monitoring carbon accumulation and sequestration potential of Large Leaf Mahogany (Swietenia macrophylla King.) plantation in Mount Makiling Forest Reserve was a continuation of the same study conducted in 2000. It aimed to look into the sequestration rate of the plantation after a 10-year period. The study measured the biomass, C and CO2 stored in the aboveground, ground and belowground biomass. It also quantified the rate of C captured with the 2000 study as baseline data. The latest study showed that the plantation has a total biomass production of 1,120 Mg ha-1 which is equivalent to 542 Mg ha-1 of C and 1,989 Mg ha-1 of CO2. Within a 10-year period, it registered a biomass buildup of 43 Mg ha-1 yr-1 and sequestered carbon at 22 Mg ha-1 yr-1 and 81 Mg ha-1 yr-1 of CO2. Its carbon storing capacity surpasses that of an old growth forest, natural stand and other types of vegetation. It can be concluded that the potential of forest plantation to sequester carbon can be maximized given a good-site condition, appropriate silvicultural practices applied, less human disturbances thus allowing the stand to attain its optimum growth as manifested by the plantation studie.
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