Eucalyptus Short-Rotation Management Effects on Nutrient and Sediments in Subtropical Streams

Carolina Bozetti Rodrigues,Patrick Lane,Walter De Paula Lima,Ricardo Hideo Taniwaki,Silvio Frosini De Barros Ferraz

doi:10.3390/f10060519

Abstract

Forested catchments generally present conserved aquatic ecosystems without anthropogenic disturbances; however, forest management operations can degrade these environments, including their water quality. Despite the potential degradation, few studies have analyzed the effects of forest management in subtropical regions, especially in forest plantations with intensive management, such as Eucalyptus plantations in Brazil. The intensive management of those plantations is characterized by fast-growing, short rotation cycles, and high productivity. This study aimed to assess the effects of Eucalyptus plantations harvesting on the concentration and exportation of nutrients and suspended solids in subtropical streams. Results showed that clear-cut harvesting and subsequent forest management operations do not alter most of the concentration of nitrate, potassium, calcium, and magnesium. The concentration of suspended solids increased during the first year after timber harvesting in all studied catchments, however, the increases were statistically significant in only two catchments. In the first year after harvest, it was observed an increment of water yield/precipitation ratio at three catchments, which also increased export of nutrients and suspended solids. Our results showed that harvesting of fast-growing Eucalyptus forest plantations partially affected sediment exports and did not compromise water quality in the studied catchments. However, the catchment land-use design, especially related to road density and land-use composition, showed significant relationship with sediment exportation.

Highlights

Water quality of a stream is determined by a range of current and historical influences on catchment, from natural or anthropogenic origin, and is an important indicator of aquatic ecosystem health [1].Streams draining forested landscapes usually have higher water quality than streams draining other land uses, such as agricultural fields [2,3,4,5,6,7,8]
Catchments are located in private company areas, which were managed for commercial purposes, following usual short rotation forest operations, inherent to the pulpwood production process
The Q:P ratio was higher in after harvesting (AH) in relation to before forest harvesting (BH) year, which means that a higher amount of precipitation was converted into streamflow in these catchments (Table 3)

Summary

Introduction

Water quality of a stream is determined by a range of current and historical influences on catchment, from natural or anthropogenic origin, and is an important indicator of aquatic ecosystem health [1].Streams draining forested landscapes usually have higher water quality than streams draining other land uses, such as agricultural fields [2,3,4,5,6,7,8]. The high quality of water provided by forested landscapes is partly attributed to a better soil infiltration and a variety of physical and biogeochemical ecosystem processes in the soil that filter particles and chemicals from the water [9]. From 1990 to 2015, native forests areas around the world were reduced from 4.28 to 3.99 billion of hectares [10]. Forest plantations play an important role in providing roundwood for industrial and energy generation in several countries around the world [10,11]. Forest plantations accounted for one-third of the world’s industrial demand for roundwood and projections indicate that in 2040, half the world’s demand for this type of raw material will be supplied by forest plantations [11,12]

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