Leaf Bags and Natural Leaf Packs: Two Approaches to Evaluate River Functional Characteristics

Abstract

An extensive knowledge of the functional characteristics of rivers is of basic importance to develop precise management plans with specific aims, e.g. to rehabilitate riparian ecotones or increase the retention capacity of streams. In this study man‐made leaf bags (LB) and natural leaf accumulations (NLP) were used. The first method was useful in calculating breakdown rates and the second one in understanding the effective litter composition, which does not always reflect the composition of the riparian canopy. The assemblages of macroinvertebrate colonizing both LB and NLP were divided into functional feeding groups and compared. Are both methods (Leaf Bags and Natural Leaf Packs) necessary and complementary to analyse the functional characteristics of an upland river? The study was carried out in three different sites on the upper reaches of the Adige River. The breakdown rates were very similar in all three study sites but litter quality and quantity were very different. Although, in the two upper sites, the composition of invertebrates colonizing LB and NLP was the same, abundance and biomass values coincided only in the first stage of the colonization process of LBs. In the third site no invertebrates using litter as a trophic resource were found. Both NLP and LB methods are needed in the evaluation of rehabilitation programs as they take account of the different aspects of the dynamics and the composition of CPOM.

Riparian vegetation as indicator of channel adjustments and environmental conditions: the case of the Panaro River (Northern Italy)

“…; retention of organic/mineral matter during high flows, e.g. Gregory et al 1989;Tockner et al 1999;Braioni et al 2001). From the ecological point of view, the riparian zone works as a food source and provides refugia and reproduction sites for both aquatic and terrestrial communities (Steiger et al 2005).…”

Comparing field and laboratory breakdown rates of coarse particulate organic matter: Sediment dynamics mask the impacts of dissolved nutrients on CPOM mass loss in streams

“…High mechanical energy of flowing water causes fragmentation because the resulted physical stress disrupts leaf structure. Some studies showed that leaf mass loss is higher in stream sites with fluctuating hydrology than in streams with little hydrological variation (Braioni et al, 2001;Spänhoff et al, 2007). In streams, physical fragmen- tation is not only caused by flowing water but also by transported sediments.…”

Laju Dekomposisi Bahan Organik Dan Produksi Invertebrata Air Di Suaka Perikanan Teluk Rasau, Sumatera Selatan

“…Ketiga bentuk bahan organik tersebut mempengaruhi aliran energi pada ekosistem perairan umum dan akan mempengaruhi keanekaragaman hayati, produktivitas perairan dan produksi ikan (Braioni et al, 2001;Kaplan & NewBold, 2003;Whitten et al, 1987). Dari ketiga bentuk bahan organik tersebut, dissolved organic matter merupakan salah satu bentuk bahan organik yang akhir dari proses mineralisasi menghasilkan unsur hara dan karbon yang dibutuhkan oleh organisme produser di perairan.…”

“…Namun hanya sebagian kecil dari fraksi bahan organik tersebut dikonsumsi oleh hewan air, selebihnya bahan organik tersebut mengalami penguraian (dekomposisi). Bahan organik yang pada beberapa fase dekomposisi, akan dikonsumsi oleh organisme detritifora seperti invertebrata air dan ikan (Braioni et al, 2001).…”

“…Tiga stasiun percobaan ditentukan secara purposif yang didasarkan atas perbedaan habitat mikroskopik secara spasial (Gambar 1 dan Tabel 1). Laju dekomposisi bahan organik dilakukan dengan metode litter bag yang terbuat dari kantong jaring berukuran 20x10 cm dengan ukuran mata jaring 2 mm (Braioni et al, 2001;Alvarez et al, 2001). Contoh dedaunan berwarna kuning yang hampir gugur dari tumbuhan riparian jenis tumbuhan serpang (Caesalpinaceae) yang dominan di masing-masing stasiun dikumpulkan dan dibawa ke laboratorium untuk dibersihkan dan dikeringkan sampai bobot stabil dalam oven pada suhu 50°C selama 48 jam.…”